Volume 15,Issue 3,2017 Table of Contents
2017, 15(3):1-4.
Abstract:
The traditional hydrological frequency analysis (THFA) method has been widely used to estimate the design flood for a given return period. It relies on the assumption that the series should be stationary. However, climate change and human activities caused the series to lose their stationarity, and thus limit the application of the THFA method. In this paper, we studied the 530-year summer-precipitation series covering the period from 1470 to 1999. At the 0.01 significant level, it was found that the series had three change points: 1534, 1724, and 1923. Therefore, the whole series was divided into four sub-sample series. We estimated the probability distribution function (PDF) of each sub-sample using the THFA method. Then we obtained the mixed probability distribution function (MPDF) by weighting and synthesizing the four PDFs related to the four sub-samples. The MPDF was regarded as the PDF of the whole series and was used to estimate the design precipitation for a given return period. Besides, the 530-year large precipitation series was also used to estimate the empirical value of the design precipitation. Then we compared the observation-sample-based estimations and MPDF-based estimations of the design precipitation. The results showed that the MPDF fit the series well.
The traditional hydrological frequency analysis (THFA) method has been widely used to estimate the design flood for a given return period. It relies on the assumption that the series should be stationary. However, climate change and human activities caused the series to lose their stationarity, and thus limit the application of the THFA method. In this paper, we studied the 530-year summer-precipitation series covering the period from 1470 to 1999. At the 0.01 significant level, it was found that the series had three change points: 1534, 1724, and 1923. Therefore, the whole series was divided into four sub-sample series. We estimated the probability distribution function (PDF) of each sub-sample using the THFA method. Then we obtained the mixed probability distribution function (MPDF) by weighting and synthesizing the four PDFs related to the four sub-samples. The MPDF was regarded as the PDF of the whole series and was used to estimate the design precipitation for a given return period. Besides, the 530-year large precipitation series was also used to estimate the empirical value of the design precipitation. Then we compared the observation-sample-based estimations and MPDF-based estimations of the design precipitation. The results showed that the MPDF fit the series well.
2017, 15(3):5-12.
Abstract:
Hydrological analysis requires the time-series consistency of runoff data, but the changing environment destroys the stability of runoff series. Under the influence of climate change and frequent human activities (water conservancy project construction, vegetation cover change and urbanization construction), the underlying surface conditions and physical mechanism of runoff yield changed obviously, resulting in runoff series variation which can not meet the requirements of consistency of hydrological time series and the same distribution. This paper identifies the trend components, the mutation components, the cyclical components and the random components of the annual and monthly runoff sequences and the rainfall date sequence recorded at the Xiahui Station in the lower reaches of the Chao River during 1976-2012 by using non-parametric Mann-Kendall rank test, Pettitt test and variance analysis respectively. By comparing these components between runoff sequences and rainfall date sequence, this paper concludes that the factor of rainfall is not the only one that leads to runoff changes, but the conjoint effect of climate change and human activities on the evolution process of the lower reaches of Chao River basin.
Hydrological analysis requires the time-series consistency of runoff data, but the changing environment destroys the stability of runoff series. Under the influence of climate change and frequent human activities (water conservancy project construction, vegetation cover change and urbanization construction), the underlying surface conditions and physical mechanism of runoff yield changed obviously, resulting in runoff series variation which can not meet the requirements of consistency of hydrological time series and the same distribution. This paper identifies the trend components, the mutation components, the cyclical components and the random components of the annual and monthly runoff sequences and the rainfall date sequence recorded at the Xiahui Station in the lower reaches of the Chao River during 1976-2012 by using non-parametric Mann-Kendall rank test, Pettitt test and variance analysis respectively. By comparing these components between runoff sequences and rainfall date sequence, this paper concludes that the factor of rainfall is not the only one that leads to runoff changes, but the conjoint effect of climate change and human activities on the evolution process of the lower reaches of Chao River basin.
2017, 15(3):13-19.
Abstract:
Based on establishing an evaluation index system, this paper developed a new post-evaluation model based on non-negative matrix factorization (NMF) for diagnostic evaluation. The model uses NMF to decompose the data matrix in to the base vector and the weight vector to the largest approximation degree. Then the base vector is taken as an assessment basis of the evaluation index, and the weight vector is used for grading the evaluation scheme. This model is applied to evaluate the water allocation scheme for Luanhe River from perspectives of scheme quality, implementation process, implementation effect and sustainability. The overall evaluation grade of the scheme is excellent, but there is still room for improvement regarding water sustainability, impact on the water environment, guarantee rate of water quality targets and so on. Results show that the post-evaluation model based on NMF can produce satisfactory outcomes of the post-evaluation considering the system as a whole.
Based on establishing an evaluation index system, this paper developed a new post-evaluation model based on non-negative matrix factorization (NMF) for diagnostic evaluation. The model uses NMF to decompose the data matrix in to the base vector and the weight vector to the largest approximation degree. Then the base vector is taken as an assessment basis of the evaluation index, and the weight vector is used for grading the evaluation scheme. This model is applied to evaluate the water allocation scheme for Luanhe River from perspectives of scheme quality, implementation process, implementation effect and sustainability. The overall evaluation grade of the scheme is excellent, but there is still room for improvement regarding water sustainability, impact on the water environment, guarantee rate of water quality targets and so on. Results show that the post-evaluation model based on NMF can produce satisfactory outcomes of the post-evaluation considering the system as a whole.
2017, 15(3):20-24.
Abstract:
The interfaces of the existing integration systems of digital watershed simulation models are not uniform. The integration is difficult between integration systems and models. The system lacks versatility and scalability. To solve the problems mentioned above, this paper built an open, scalable, and shareable integration architecture for digital watershed simulation models by using SOA and cloud computing technologies. In this architecture, the various transactions in the cloud service system were decomposed into services of different granularities, and the sub-functions were packaged as standard web services. Taking advantage of the typical modularity feature of SOA, the integrated architecture was divided into client layer, cloud service platform, cloud computing application interface layer, model management service layer, cloud service management layer, and physical resources layer. The application system services of the integrated model originated from these layers. This architecture enhanced the openness, interactivity and versatility of water conservancy model platforms.
The interfaces of the existing integration systems of digital watershed simulation models are not uniform. The integration is difficult between integration systems and models. The system lacks versatility and scalability. To solve the problems mentioned above, this paper built an open, scalable, and shareable integration architecture for digital watershed simulation models by using SOA and cloud computing technologies. In this architecture, the various transactions in the cloud service system were decomposed into services of different granularities, and the sub-functions were packaged as standard web services. Taking advantage of the typical modularity feature of SOA, the integrated architecture was divided into client layer, cloud service platform, cloud computing application interface layer, model management service layer, cloud service management layer, and physical resources layer. The application system services of the integrated model originated from these layers. This architecture enhanced the openness, interactivity and versatility of water conservancy model platforms.
2017, 15(3):25-29.
Abstract:
The method of water-supply scheduling is an important issue concerning producing more benefits from the Danjiangkou hydro project. In this paper, a graph of water-supply scheduling was proposed for efficient utilization of water resources, based on the planning & design achievements of the Phase-I South-to-North Water Transfer Middle-Route Project and the requirements on water scheduling scheme compilation for the Middle Route Project. Meanwhile, designed hydrological inflows were used to check the proposed scheduling graph. Results showed that the graph is clear and easy to operate. The operation of Danjiangkou hydro project based on this graph can satisfy the designed water demand of all users and make the water transfer process more balanced. The scheduling graph can guide the operation of Danjiangkou hydro project.
The method of water-supply scheduling is an important issue concerning producing more benefits from the Danjiangkou hydro project. In this paper, a graph of water-supply scheduling was proposed for efficient utilization of water resources, based on the planning & design achievements of the Phase-I South-to-North Water Transfer Middle-Route Project and the requirements on water scheduling scheme compilation for the Middle Route Project. Meanwhile, designed hydrological inflows were used to check the proposed scheduling graph. Results showed that the graph is clear and easy to operate. The operation of Danjiangkou hydro project based on this graph can satisfy the designed water demand of all users and make the water transfer process more balanced. The scheduling graph can guide the operation of Danjiangkou hydro project.
2017, 15(3):30-36.
Abstract:
Based on the 54-year yearly grid precipitation data of mainland China from 1961 to 2014, the inverse distance weighted interpolation method was used to analysis the spatial-temporal variation on precipitation. Annual precipitation was classified by different quantities and the 54-year area percentage variation of each type was calculated out. A concept of precipitation barycenter was introduced. This study took the amount of precipitation as weights to estimate the annual precipitation barycenter and its changing features. The results show that area percentage variation of each annual precipitation type and the coordinate changing of annual precipitation barycenter were in random sequence with clearly fluctuant features. The annual precipitation type of 400~600mm accounts for the largest area proportion. Also its trend and fluctuation range are the most significant one. By the significant effect of precipitation variability in Northeast and North China, the divergence of precipitation barycenter is larger in northeast-southwest direction. So it can indicate the regional climate abnormal variation. Annual precipitation barycenter changing of the 54 years is most related to >1400mm rainfall area at the latitudinal direction(Y-coordinate). In terms of the longitudinal direction(X-coordinate), there is on obvious correlation. So at this space (mainland China) and time (54years from 1961~2014) scale, the overall precipitation patterns did not change significantly.
Based on the 54-year yearly grid precipitation data of mainland China from 1961 to 2014, the inverse distance weighted interpolation method was used to analysis the spatial-temporal variation on precipitation. Annual precipitation was classified by different quantities and the 54-year area percentage variation of each type was calculated out. A concept of precipitation barycenter was introduced. This study took the amount of precipitation as weights to estimate the annual precipitation barycenter and its changing features. The results show that area percentage variation of each annual precipitation type and the coordinate changing of annual precipitation barycenter were in random sequence with clearly fluctuant features. The annual precipitation type of 400~600mm accounts for the largest area proportion. Also its trend and fluctuation range are the most significant one. By the significant effect of precipitation variability in Northeast and North China, the divergence of precipitation barycenter is larger in northeast-southwest direction. So it can indicate the regional climate abnormal variation. Annual precipitation barycenter changing of the 54 years is most related to >1400mm rainfall area at the latitudinal direction(Y-coordinate). In terms of the longitudinal direction(X-coordinate), there is on obvious correlation. So at this space (mainland China) and time (54years from 1961~2014) scale, the overall precipitation patterns did not change significantly.
2017, 15(3):37-42.
Abstract:
Fukang city in Xinjiang province is faced with increasing scarcity of water resources and worsening ecology. Based on DPSIR, we conducted factor analysis of water resources carrying capacity (WRRC) and built a basic indicator system. Principal component analysis was used to select the main indicators of WRRC and entropy weight analysis was used to determine their weights. A comprehensive evaluation model was built to calculate and evaluate the WRRC of Fukang. The results showed that the selected 4 main indicators can well represent the basic indicator system with an accumulative contribution rate of 92.016%. The WRRC of Fukang fluctuated between 0.498-0.531 during 2006-2014. The rate of decline was slow and the fluctuation range decreased with time. Generally, the utilization has reached saturation. The increased use of agricultural water resulting from social and economic development was a main indicator of the decline in WRRC. But the trend of decline was strongly relieved by the expanding groundwater exploitation and water resources management practices in Fukang.
Fukang city in Xinjiang province is faced with increasing scarcity of water resources and worsening ecology. Based on DPSIR, we conducted factor analysis of water resources carrying capacity (WRRC) and built a basic indicator system. Principal component analysis was used to select the main indicators of WRRC and entropy weight analysis was used to determine their weights. A comprehensive evaluation model was built to calculate and evaluate the WRRC of Fukang. The results showed that the selected 4 main indicators can well represent the basic indicator system with an accumulative contribution rate of 92.016%. The WRRC of Fukang fluctuated between 0.498-0.531 during 2006-2014. The rate of decline was slow and the fluctuation range decreased with time. Generally, the utilization has reached saturation. The increased use of agricultural water resulting from social and economic development was a main indicator of the decline in WRRC. But the trend of decline was strongly relieved by the expanding groundwater exploitation and water resources management practices in Fukang.
2017, 15(3):43-48.
Abstract:
In cold and arid watersheds, streamflow is mainly contributed by snowmelt runoff in the ablation period and rainfall runoff during summer. Surface runoff and snowmelt may have important influence on the water cycle. In this study, the extended Fourier amplitude sensitivity test (EFAST) method was employed for SWAT model parameter sensitivity analysis. The test involved hydrological parameters that describe multiple processes including rainfall runoff, snowmelt, evaporation, percolation, baseflow, and lateral flow. Peak flows in non-melting and snow-melting periods as well as average annual flow were all considered in the sensitivity analysis. In addition, the reasons for the sensitivity of the parameters and the associated hydrological processes that affect the water cycle in the watershed were analyzed. Results showed that the surface runoff, percolation, and snowmelt have significant influence. Besides, the total-order sensitivity of the parameters related to snowmelt process was significant whereas the first-order sensitivity was not significant, indicating that the total-order sensitivity obtained using EFAST is more reasonable. The findings will help hydrological models improve their capability for simulating/predicting water resources during different seasons for snowmelt-precipitation-driven watersheds.
In cold and arid watersheds, streamflow is mainly contributed by snowmelt runoff in the ablation period and rainfall runoff during summer. Surface runoff and snowmelt may have important influence on the water cycle. In this study, the extended Fourier amplitude sensitivity test (EFAST) method was employed for SWAT model parameter sensitivity analysis. The test involved hydrological parameters that describe multiple processes including rainfall runoff, snowmelt, evaporation, percolation, baseflow, and lateral flow. Peak flows in non-melting and snow-melting periods as well as average annual flow were all considered in the sensitivity analysis. In addition, the reasons for the sensitivity of the parameters and the associated hydrological processes that affect the water cycle in the watershed were analyzed. Results showed that the surface runoff, percolation, and snowmelt have significant influence. Besides, the total-order sensitivity of the parameters related to snowmelt process was significant whereas the first-order sensitivity was not significant, indicating that the total-order sensitivity obtained using EFAST is more reasonable. The findings will help hydrological models improve their capability for simulating/predicting water resources during different seasons for snowmelt-precipitation-driven watersheds.
2017, 15(3):49-54.
Abstract:
This paper selected the monthly observed groundwater depth data during 1988-2013 from 17 monitoring wells at Dengkou County in the desert oasis region, and explored the temporal and spatial variation characteristics of the groundwater depth in study area during the 26 years by using kernel K-means and Empirical Mode Decomposition method. The results indicated the following findings: Firstly, 17 monitoring wells can be divided into 3 clusters. The first cluster contains 6 monitoring wells with the largest average depth of groundwater. The second cluster contains 4 monitoring wells with the second largest average depth of groundwater. The third cluster contains 7 monitoring wells with the smallest average depth of groundwater. Secondly, during the past 26 years, the groundwater depths of the first and second clusters tend to increase, respectively up by 0.014m and 0.26m. The groundwater depth of the third cluster tends to decrease, down by 0.08m. Thirdly, the groundwater depths of the three clusters basically show the same annual variation tendency.
This paper selected the monthly observed groundwater depth data during 1988-2013 from 17 monitoring wells at Dengkou County in the desert oasis region, and explored the temporal and spatial variation characteristics of the groundwater depth in study area during the 26 years by using kernel K-means and Empirical Mode Decomposition method. The results indicated the following findings: Firstly, 17 monitoring wells can be divided into 3 clusters. The first cluster contains 6 monitoring wells with the largest average depth of groundwater. The second cluster contains 4 monitoring wells with the second largest average depth of groundwater. The third cluster contains 7 monitoring wells with the smallest average depth of groundwater. Secondly, during the past 26 years, the groundwater depths of the first and second clusters tend to increase, respectively up by 0.014m and 0.26m. The groundwater depth of the third cluster tends to decrease, down by 0.08m. Thirdly, the groundwater depths of the three clusters basically show the same annual variation tendency.
2017, 15(3):55-59.
Abstract:
Yingnahe reservoir is responsible for flood control in the basin, and it is an important water source of Dalian city. Its water resources utilization efficiency is very important to the social and economic development of Dalian city. As Yingnahe reservoir does not have a flood control operation scheme yet for the flood season after its reconstruction, we formulated a flood control operation scheme based on forecasting information after we analyzed the availability of runoff production forecast and water draining forecast of the reservoir, with the accumulated net rainfall, reservoir inflow and water level as judging indexes for changing the reservoir outflow. The results showed that the flood forecasting operation scheme can basically realize reservoir regulation, and is reasonable, feasible, and easy to operate. By using the water draining margin as the water storage capacity after pre-discharge of the reservoir, the operation scheme not only ensures economical benefits, but also improves the flood resource utilization efficiency and flood control ability of the reservoir.
Yingnahe reservoir is responsible for flood control in the basin, and it is an important water source of Dalian city. Its water resources utilization efficiency is very important to the social and economic development of Dalian city. As Yingnahe reservoir does not have a flood control operation scheme yet for the flood season after its reconstruction, we formulated a flood control operation scheme based on forecasting information after we analyzed the availability of runoff production forecast and water draining forecast of the reservoir, with the accumulated net rainfall, reservoir inflow and water level as judging indexes for changing the reservoir outflow. The results showed that the flood forecasting operation scheme can basically realize reservoir regulation, and is reasonable, feasible, and easy to operate. By using the water draining margin as the water storage capacity after pre-discharge of the reservoir, the operation scheme not only ensures economical benefits, but also improves the flood resource utilization efficiency and flood control ability of the reservoir.
2017, 15(3):60-66.
Abstract:
High/low precipitation characteristics are important content of precipitation process research. We conducted multi-time scale analysis on the high/low precipitation characteristics of each water resource zone on the Handan Plain using wavelet analysis. The research results showed that: (1) There is a 5 years’ or 9 years’ periodicity in the precipitation processes of all zones on the plain. There is also a 2 years’ or 13 years’ periodicity in the precipitation processes of all zones except for Fuxi Plain. A 21 years’ periodicity is also prominent in the precipitation processes of Zhangweihe and Heilonggang Plains. (2) The high/low precipitation alternation is prominent in all zones on the 5-year and 9-year scales. (3) The high/low precipitation responses of different zones vary on different time scales, and show varied high/low characteristics and evolution trend. The results can provide reference for the local water management and early warning of regional droughts and floods.
High/low precipitation characteristics are important content of precipitation process research. We conducted multi-time scale analysis on the high/low precipitation characteristics of each water resource zone on the Handan Plain using wavelet analysis. The research results showed that: (1) There is a 5 years’ or 9 years’ periodicity in the precipitation processes of all zones on the plain. There is also a 2 years’ or 13 years’ periodicity in the precipitation processes of all zones except for Fuxi Plain. A 21 years’ periodicity is also prominent in the precipitation processes of Zhangweihe and Heilonggang Plains. (2) The high/low precipitation alternation is prominent in all zones on the 5-year and 9-year scales. (3) The high/low precipitation responses of different zones vary on different time scales, and show varied high/low characteristics and evolution trend. The results can provide reference for the local water management and early warning of regional droughts and floods.
2017, 15(3):67-72.
Abstract:
The planting structure information extracted by high-resolution remote sensing imaging can be more intuitive than traditional statistical data to present the spatial distribution and area information of crops. These data can provide important reference for water resources management. In order to eliminate the influence of mixed pixels in GF-1 WFV sensor images on wheat information extraction, we introduced the high-resolution GF-1 PMS sensor images, and established samples in the two images. We used the superior resolution of PMS images to provide real wheat area weight to the training samples of wheat mixed pixels in the WFV image, and obtained the relationship between wheat NDVI and wheat area weight. Then we used the interval normalization method to solve the problem in which one NDVI value corresponded to different wheat area weights, and thus obtained the true area information of wheat in mixed pixels, and extracted the winter wheat information of Jizhou City. It was verified that the method can accurately extract information of winter wheat area under the condition of insufficient samples.
The planting structure information extracted by high-resolution remote sensing imaging can be more intuitive than traditional statistical data to present the spatial distribution and area information of crops. These data can provide important reference for water resources management. In order to eliminate the influence of mixed pixels in GF-1 WFV sensor images on wheat information extraction, we introduced the high-resolution GF-1 PMS sensor images, and established samples in the two images. We used the superior resolution of PMS images to provide real wheat area weight to the training samples of wheat mixed pixels in the WFV image, and obtained the relationship between wheat NDVI and wheat area weight. Then we used the interval normalization method to solve the problem in which one NDVI value corresponded to different wheat area weights, and thus obtained the true area information of wheat in mixed pixels, and extracted the winter wheat information of Jizhou City. It was verified that the method can accurately extract information of winter wheat area under the condition of insufficient samples.
2017, 15(3):73-79.
Abstract:
Under the background of implementation of the most stringent management regulations on water resources, the prediction of short-term water consumption is playing an increasingly significant role in urban water supply system scheduling. Based on the analysis of the temporal evolution pattern and random factors of short-term water consumption, a Bayesian neural network prediction model for urban short-term water consumption was built with the daily maximum temperature, daily water consumption of the previous 7 days, ratio of water consumption of the current month to the annual amount, daily precipitation, and holidays as predictors of short-term water consumption. Meanwhile, Bayesian regularization was used to optimize BP neural network. Both BP network model and the optimized model were applied to a running-water company in Guangzhou City for tesing. The results indicated that the mean absolute percentage error of the Bayesian neural network prediction model was 0.87%, while that of the BP neural network prediction model was 1.85%. Compared to the BP neural network prediction model, the optimized model has stronger generalization ability, with accuracy improved by about 0.98%. Thus, it fits better with the high-precision requirement of urban short-term water prediction.
Under the background of implementation of the most stringent management regulations on water resources, the prediction of short-term water consumption is playing an increasingly significant role in urban water supply system scheduling. Based on the analysis of the temporal evolution pattern and random factors of short-term water consumption, a Bayesian neural network prediction model for urban short-term water consumption was built with the daily maximum temperature, daily water consumption of the previous 7 days, ratio of water consumption of the current month to the annual amount, daily precipitation, and holidays as predictors of short-term water consumption. Meanwhile, Bayesian regularization was used to optimize BP neural network. Both BP network model and the optimized model were applied to a running-water company in Guangzhou City for tesing. The results indicated that the mean absolute percentage error of the Bayesian neural network prediction model was 0.87%, while that of the BP neural network prediction model was 1.85%. Compared to the BP neural network prediction model, the optimized model has stronger generalization ability, with accuracy improved by about 0.98%. Thus, it fits better with the high-precision requirement of urban short-term water prediction.
2017, 15(3):80-85.
Abstract:
In order to better determine the potential impacts of water contaminants on public health, a fuzzy model based on triangular fuzzy number theory was developed to evaluate the human health risk of drinking groundwater well fields in Shizuishan city in this paper, and then the effects of uncertainties on health risks were analyzed. The results showed that the health risk is not sensitive to the parameter-value-related uncertainty. The pollutant-concentration-related uncertainty plays an important role in the assessment. If the changes in concentration are not taken into account, the calculated risks will be smaller. By using the above model, we obtained the health risks of carcinogens and non-carcinogens in the drinking water well fields of Shizuishan. The chemical carcinogenic risks are much larger than the noncarcinogenic risks, which are all close to the permissible level of 1.0×10-4 a-1. Cr should be the priority concern in the water resource management due to the high carcinogenic risk. The human health risks of the water environment are ranked as follows: NO. 2 well field> NO. 5 well field >NO. 4 well field >NO. 1 well field.
In order to better determine the potential impacts of water contaminants on public health, a fuzzy model based on triangular fuzzy number theory was developed to evaluate the human health risk of drinking groundwater well fields in Shizuishan city in this paper, and then the effects of uncertainties on health risks were analyzed. The results showed that the health risk is not sensitive to the parameter-value-related uncertainty. The pollutant-concentration-related uncertainty plays an important role in the assessment. If the changes in concentration are not taken into account, the calculated risks will be smaller. By using the above model, we obtained the health risks of carcinogens and non-carcinogens in the drinking water well fields of Shizuishan. The chemical carcinogenic risks are much larger than the noncarcinogenic risks, which are all close to the permissible level of 1.0×10-4 a-1. Cr should be the priority concern in the water resource management due to the high carcinogenic risk. The human health risks of the water environment are ranked as follows: NO. 2 well field> NO. 5 well field >NO. 4 well field >NO. 1 well field.
2017, 15(3):86-93.
Abstract:
Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) has been used extensively in broiler poultry feed, and most roxarsone is excreted, almost untransformed, as part of the waste. After entering into the environment, roxarsone can be rapidly transformed into more toxic derivatives, such as arsenate and arsenite, via microbial action or photolysis. These arsenical products can then contaminate soil, surface water, and groundwater through rain and farming irrigation. A chicken farm of Lubei Plain was taken as the study area. The chicken manure, chicken feed, surface soil, manure-piled or background vertical vadose zone profiles, and groundwater around the chicken farm were sampled and the arsenic compounds were detected. The roxarsone concentration in the chicken feed was 34 mg/kg and the HAPA (3-amino-4-hydroxyphenylarsonic) concentration in the chicken manure was 11 mg/kg. The closer to the chicken farm, the higher the arsenic concentration in the surface soil. The arsenic compounds in the three vadose zone profiles were mainly AS(V), with a little AS(III). The concentrations of HAPA, As(V), and As(III) in the manure-piled vertical vadose zone profiles were the highest in the topsoil, and they decreased as the depth increased, while also being affected by soil lithology. The main adsorption layers of arsenic compounds were at 0-30 cm depth and below 200 cm. Compared with that in the background vadose zone, the concentration of arsenic compounds in the manure-piled vertical vadose zone was higher. Among the groundwater samples, 165 μg/kg of As(V) was detected in the old well. The results confirmed that the piled chicken manure had increased the arsenic concentration in the vertical vadose zone, surface soil, and groundwater around the chicken farm, and this pollution was difficult to eliminate.
Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) has been used extensively in broiler poultry feed, and most roxarsone is excreted, almost untransformed, as part of the waste. After entering into the environment, roxarsone can be rapidly transformed into more toxic derivatives, such as arsenate and arsenite, via microbial action or photolysis. These arsenical products can then contaminate soil, surface water, and groundwater through rain and farming irrigation. A chicken farm of Lubei Plain was taken as the study area. The chicken manure, chicken feed, surface soil, manure-piled or background vertical vadose zone profiles, and groundwater around the chicken farm were sampled and the arsenic compounds were detected. The roxarsone concentration in the chicken feed was 34 mg/kg and the HAPA (3-amino-4-hydroxyphenylarsonic) concentration in the chicken manure was 11 mg/kg. The closer to the chicken farm, the higher the arsenic concentration in the surface soil. The arsenic compounds in the three vadose zone profiles were mainly AS(V), with a little AS(III). The concentrations of HAPA, As(V), and As(III) in the manure-piled vertical vadose zone profiles were the highest in the topsoil, and they decreased as the depth increased, while also being affected by soil lithology. The main adsorption layers of arsenic compounds were at 0-30 cm depth and below 200 cm. Compared with that in the background vadose zone, the concentration of arsenic compounds in the manure-piled vertical vadose zone was higher. Among the groundwater samples, 165 μg/kg of As(V) was detected in the old well. The results confirmed that the piled chicken manure had increased the arsenic concentration in the vertical vadose zone, surface soil, and groundwater around the chicken farm, and this pollution was difficult to eliminate.
2017, 15(3):94-99.
Abstract:
The health assessment index system and grading standards for surface water environment were put forward for rational exploitation and protection of water resources in Dagu River basin. A model coupling entropy weight and multivariate connection number was established based on the set pair analysis theory with consideration to the uncertainty of the boundary of grade standards for each index. The method was applied to Dagu River basin to obtain the connection numbers of the health assessment index of surface water environment. The results showed that the surface water environment of Regions Ⅰ(Laixi), Ⅱ(Pingdu), Ⅲ(Jiaozhou and Huangdao), Ⅳ(Jimo and Chengyang), and Ⅵ(Laiyang, Zhaoyuan, and Laizhou) in 2015 were all healthy, but Region Ⅴ(Gaomi) and the whole basin were sub-healthy. The surface water environment of Dagu River basin has been greatly improved by the implementation of the comprehensive management program in Qingdao. The water environment treatment of the whole basin should be carried out in order to further improve the health of the surface water environment in Dagu River basin.
The health assessment index system and grading standards for surface water environment were put forward for rational exploitation and protection of water resources in Dagu River basin. A model coupling entropy weight and multivariate connection number was established based on the set pair analysis theory with consideration to the uncertainty of the boundary of grade standards for each index. The method was applied to Dagu River basin to obtain the connection numbers of the health assessment index of surface water environment. The results showed that the surface water environment of Regions Ⅰ(Laixi), Ⅱ(Pingdu), Ⅲ(Jiaozhou and Huangdao), Ⅳ(Jimo and Chengyang), and Ⅵ(Laiyang, Zhaoyuan, and Laizhou) in 2015 were all healthy, but Region Ⅴ(Gaomi) and the whole basin were sub-healthy. The surface water environment of Dagu River basin has been greatly improved by the implementation of the comprehensive management program in Qingdao. The water environment treatment of the whole basin should be carried out in order to further improve the health of the surface water environment in Dagu River basin.
2017, 15(3):100-107.
Abstract:
The Yellow River is the most important surface water resource in Ningxia, so the water environment quality will directly affect the social and economic development of Ningxia. Based on the statistical data from the environmental monitoring station in Ningxia from 2010 to 2014, using the monitoring data of the main pollutants such as chemical oxygen demand, ammonia nitrogen, and total phosphorus, we employed matter-element analysis, fuzzy clustering, and WASP model to optimize the layout of the Yellow River water quality monitoring cross-sections in Ningxia section. The results showed that the present six national monitoring cross-sections could not provide sufficient monitoring of the water quality variation of Yellow River, and two additional monitoring cross-sections should be added. One should be between Xiaheyan and Jinshawan national monitoring cross-sections, and the other should be between Yesheng Road Bridge and Yingu Road Bridge national monitoring cross-sections. They are respectively at Shikong county (105°40′31″E, 37°34′04″N) and Linhe county (106°18′36″E, 38°16′11″N).
The Yellow River is the most important surface water resource in Ningxia, so the water environment quality will directly affect the social and economic development of Ningxia. Based on the statistical data from the environmental monitoring station in Ningxia from 2010 to 2014, using the monitoring data of the main pollutants such as chemical oxygen demand, ammonia nitrogen, and total phosphorus, we employed matter-element analysis, fuzzy clustering, and WASP model to optimize the layout of the Yellow River water quality monitoring cross-sections in Ningxia section. The results showed that the present six national monitoring cross-sections could not provide sufficient monitoring of the water quality variation of Yellow River, and two additional monitoring cross-sections should be added. One should be between Xiaheyan and Jinshawan national monitoring cross-sections, and the other should be between Yesheng Road Bridge and Yingu Road Bridge national monitoring cross-sections. They are respectively at Shikong county (105°40′31″E, 37°34′04″N) and Linhe county (106°18′36″E, 38°16′11″N).
2017, 15(3):108-112.
Abstract:
The karstic fissures and conduits are the main underground water-storing space and water-conducting channels in Southwest China. Sinkholes are important water discharge channels for temporary storage of the surface water in karst area, and are widely distributed in the Southwest. To study the effects of sinkholes on the spring flow attenuation process is of great importance to the sustainable development and the study of the karst hydrology. A physical model of fissure-conduit medium was set up in this study, and was used to simulate the spring flow attenuation process in sinkholes of different sizes and degrees of filling. The sensitivity of the attenuation coefficient to different factors was explored with the attenuation curve. Results of the experiments demonstrated that the exponential attenuation formulation can describe the attenuation process generally, and the attenuation curve can be divided into three phases. The attenuation coefficient of the first phase is much subject to the size of the sinkhole. The attenuation coefficient will increase as the sinkhole size decreases, and it has positive correlation with the degree of filling of sinkholes.
The karstic fissures and conduits are the main underground water-storing space and water-conducting channels in Southwest China. Sinkholes are important water discharge channels for temporary storage of the surface water in karst area, and are widely distributed in the Southwest. To study the effects of sinkholes on the spring flow attenuation process is of great importance to the sustainable development and the study of the karst hydrology. A physical model of fissure-conduit medium was set up in this study, and was used to simulate the spring flow attenuation process in sinkholes of different sizes and degrees of filling. The sensitivity of the attenuation coefficient to different factors was explored with the attenuation curve. Results of the experiments demonstrated that the exponential attenuation formulation can describe the attenuation process generally, and the attenuation curve can be divided into three phases. The attenuation coefficient of the first phase is much subject to the size of the sinkhole. The attenuation coefficient will increase as the sinkhole size decreases, and it has positive correlation with the degree of filling of sinkholes.
2017, 15(3):113-119.
Abstract:
Landslide and debris flow are two common geological hazard types in the South-western mountainous area in China. One of the key factors for hazard assessment of landslides and debris flows is their post-initiation mobility. First, the runout process of Bajiaoshu landslide/debris flow was simulated with the Voellmy frictional model, and parameters were obtained. Then the simulation parameters were used to simulate the runout process of Nan’en School landslide for runout prediction and hazard assessment. The results proved to be consistent with field investigation results and earlier hazard assessment conclusions.
Landslide and debris flow are two common geological hazard types in the South-western mountainous area in China. One of the key factors for hazard assessment of landslides and debris flows is their post-initiation mobility. First, the runout process of Bajiaoshu landslide/debris flow was simulated with the Voellmy frictional model, and parameters were obtained. Then the simulation parameters were used to simulate the runout process of Nan’en School landslide for runout prediction and hazard assessment. The results proved to be consistent with field investigation results and earlier hazard assessment conclusions.
2017, 15(3):120-125.
Abstract:
Land subsidence induced by excessive groundwater withdrawal has constituted a major environmental geological problem in Beijing’s plain areas. This paper selected Xiaotangshan and Houshayu areas as typical research areas. By analyzing the development and utilization of bedrock water, we carried out research on the land subsidence induced by bedrock water exploitation. A simplified elastic model was used to assess the amount of elastic deformation caused by bedrock water exploitation. The results showed that from 1974 to 2010, the total exploitation of Xiaotangshan geothermal field was about 94 million cubic meters and the exploitation led to about 1.02 cm elastic deformation; the exploitation of Xiaotangshan karst water reached 30 million cubic meters annually, causing an average annual deformation of about 0.32 cm. Approximate values of the Houshayu area was obtained through estimation, and the accumulated elastic deformation caused by Quaternary groundwater exploitation was about 1.09 cm in the period from 1961 to 2011.
Land subsidence induced by excessive groundwater withdrawal has constituted a major environmental geological problem in Beijing’s plain areas. This paper selected Xiaotangshan and Houshayu areas as typical research areas. By analyzing the development and utilization of bedrock water, we carried out research on the land subsidence induced by bedrock water exploitation. A simplified elastic model was used to assess the amount of elastic deformation caused by bedrock water exploitation. The results showed that from 1974 to 2010, the total exploitation of Xiaotangshan geothermal field was about 94 million cubic meters and the exploitation led to about 1.02 cm elastic deformation; the exploitation of Xiaotangshan karst water reached 30 million cubic meters annually, causing an average annual deformation of about 0.32 cm. Approximate values of the Houshayu area was obtained through estimation, and the accumulated elastic deformation caused by Quaternary groundwater exploitation was about 1.09 cm in the period from 1961 to 2011.
2017, 15(3):126-131.
Abstract:
The relationship between the hydrogeological properties and electrical responses of metamorphic rock fissure water in water-shortage areas of Taihang Mountains has perplexed geologists for a long time. The metamorphic rock area in Fuping County is a typical water-shortage area. Based on the regional geological data, we studied the hydrogeological properties of the metamorphic rock area in Fuping County. We found out the occurrence patterns of the strata, geological structure, and metamorphic rock fissure water. On this basis, we studied the electrical responses to the hydrogeological properties of metamorphic rock fissure water using audio frequency telluric electricity field method, radioactivity exploration, audio frequency magnetotelluric method, and induced polarization method. Geological drills were arranged to test and verify the degree of correspondence between the hydrogeological properties and electrical responses. The results showed that there is evident one-to-one correspondence between the hydrogeological properties and electrical responses of the metamorphic rock fissure water in Fuping County. The groundwater exploration in the metamorphic rock fissure water area in Fuping County has huge practical significance, and it will serve as an example for finding groundwater in other metamorphic rock areas of this type.
The relationship between the hydrogeological properties and electrical responses of metamorphic rock fissure water in water-shortage areas of Taihang Mountains has perplexed geologists for a long time. The metamorphic rock area in Fuping County is a typical water-shortage area. Based on the regional geological data, we studied the hydrogeological properties of the metamorphic rock area in Fuping County. We found out the occurrence patterns of the strata, geological structure, and metamorphic rock fissure water. On this basis, we studied the electrical responses to the hydrogeological properties of metamorphic rock fissure water using audio frequency telluric electricity field method, radioactivity exploration, audio frequency magnetotelluric method, and induced polarization method. Geological drills were arranged to test and verify the degree of correspondence between the hydrogeological properties and electrical responses. The results showed that there is evident one-to-one correspondence between the hydrogeological properties and electrical responses of the metamorphic rock fissure water in Fuping County. The groundwater exploration in the metamorphic rock fissure water area in Fuping County has huge practical significance, and it will serve as an example for finding groundwater in other metamorphic rock areas of this type.
2017, 15(3):132-138.
Abstract:
The study on the resilience deformation rule of canal base in the process of canal excavation has a guiding significance to the canal floor construction. With the improved layered settlement instrument equipped with induction ring, we measured the maximum resilience of the canal base caused by secondary canal excavation to be 102 mm, and established a resilience deformation model, and analyzed quantitatively the contribution degree of each impact factor to the resilience deformation. The results showed that the excavation unloading was the main impact factor of canal base resilience deformation, accounting for about 74% of the total resilience. The canal floor resilience caused by time effect was only 2.43 mm in 5 months after being closed in December 2013. It had little influence on the floor structure, and was conducive to the safe running of the canal.
The study on the resilience deformation rule of canal base in the process of canal excavation has a guiding significance to the canal floor construction. With the improved layered settlement instrument equipped with induction ring, we measured the maximum resilience of the canal base caused by secondary canal excavation to be 102 mm, and established a resilience deformation model, and analyzed quantitatively the contribution degree of each impact factor to the resilience deformation. The results showed that the excavation unloading was the main impact factor of canal base resilience deformation, accounting for about 74% of the total resilience. The canal floor resilience caused by time effect was only 2.43 mm in 5 months after being closed in December 2013. It had little influence on the floor structure, and was conducive to the safe running of the canal.
2017, 15(3):139-144.
Abstract:
The creep characteristic of saturated silt soil was studied through k0 consolidation creep tests under the conditions of axial loading and lateral lightening. The following results were found. First, the axial creep patterns of the two stress paths were basically consistent under the drainage conditions. The volume strains were much smaller than the axial strains. The volume strains showed an alternation between shear shrinkage and shear dilatancy with the passage of time. The Merchant and Burgers creep models both had good fitting accuracy. The creep parameter EM showed no significant increasing or decreasing trend with the increase of deviatoric stress level, but the other creep parameters EK, ηK, ηM of the two creep models decreased with the increase of deviatoric stress level. These findings suggested that the creep strain of silt soil is mildly influenced by viscoelastic modulus, but largely influenced by the viscous coefficient and elastic modulus.
The creep characteristic of saturated silt soil was studied through k0 consolidation creep tests under the conditions of axial loading and lateral lightening. The following results were found. First, the axial creep patterns of the two stress paths were basically consistent under the drainage conditions. The volume strains were much smaller than the axial strains. The volume strains showed an alternation between shear shrinkage and shear dilatancy with the passage of time. The Merchant and Burgers creep models both had good fitting accuracy. The creep parameter EM showed no significant increasing or decreasing trend with the increase of deviatoric stress level, but the other creep parameters EK, ηK, ηM of the two creep models decreased with the increase of deviatoric stress level. These findings suggested that the creep strain of silt soil is mildly influenced by viscoelastic modulus, but largely influenced by the viscous coefficient and elastic modulus.
24 Finite element analysis of the structural characteristics of new assembly buttressed retaining wall
2017, 15(3):145-150.
Abstract:
New assembly buttressed retaining wall is environmentally friendly, beautiful, and can be constructed rapidly, but the adjoining faces between the old and new concrete and the joints can affect the integrity of the structure. Based on the renovation project of Maling river in Suqian city, we analyzed the characteristics of the stress, displacement, and deformation of the wall and the influence of different parameters of the adjoining faces on the loading behavior of the structure using the finite element method. The results showed that the shear stress of the adjoining faces is smaller than the anti-sliding force and that the elastic shear deformation is very small and belongs to the elastic deformation. The tensile stress in the joint is far less than the tensile strength of the concrete. There is greater tensile stress in the junctions between the upper end of the buttress and the precast slab, between the front end of the buttress and the floor, and between the panel and floor. The maximum tensile stress is 1.5MPa, less than the design tensile strength of the concrete. The deformation and displacement of the retaining wall are small and meet the application requirements. Without regard to the cohesion of the adjoining face, the friction coefficient of the adjoining face is more than 0.5. The new assembly buttressed retaining wall of the project meets the safety requirements. The technical scheme is feasible and applicable. The analysis results can provide reference for design and construction.
New assembly buttressed retaining wall is environmentally friendly, beautiful, and can be constructed rapidly, but the adjoining faces between the old and new concrete and the joints can affect the integrity of the structure. Based on the renovation project of Maling river in Suqian city, we analyzed the characteristics of the stress, displacement, and deformation of the wall and the influence of different parameters of the adjoining faces on the loading behavior of the structure using the finite element method. The results showed that the shear stress of the adjoining faces is smaller than the anti-sliding force and that the elastic shear deformation is very small and belongs to the elastic deformation. The tensile stress in the joint is far less than the tensile strength of the concrete. There is greater tensile stress in the junctions between the upper end of the buttress and the precast slab, between the front end of the buttress and the floor, and between the panel and floor. The maximum tensile stress is 1.5MPa, less than the design tensile strength of the concrete. The deformation and displacement of the retaining wall are small and meet the application requirements. Without regard to the cohesion of the adjoining face, the friction coefficient of the adjoining face is more than 0.5. The new assembly buttressed retaining wall of the project meets the safety requirements. The technical scheme is feasible and applicable. The analysis results can provide reference for design and construction.
2017, 15(3):151-157.
Abstract:
In order to analyze the effects of different backfill materials and different backfill thickness on the dynamic response of intake towers, we set up a numerical test model that combined 6 types of backfill materials and 4 types of backfill thickness, and conducted dynamic analysis of the intake tower. When the rock ballast was filled, the maximum stress of the area was greatly reduced, and the stress distribution of the contact surface was changed; the thickness of backfill had little influence on the displacement of the top of the tower. Based on the calculation results and analysis of the numerical test, a new type of backfill was designed with rational use of rock ballast backfill. For this type, the junction between the tower and the backfill was not in the position of the concentrated stress. The maximum stress of the contact surface was greatly reduced, and the stress value of the same area was reduced. The large-stress area shifted downwards, and the area became larger and wider, indicating that the new type improved the stress state of the intake tower structure, and was beneficial to the safety of the intake tower. The proposed method was applied to the structure of a water intake tower in a flood discharging tunnel. Comparison was made between the new and original backfill types in terms of the stress time-history curve of the junction between the intake tower back and backfill, as well as the stress nephogram and damage nephogram of the contact surface between the intake tower back and backfill. The results showed that the dynamic response of the contact surface between the intake tower and backfill was greatly improved by the new type of backfill. This backfill method is of great significance to earthquake resistance and safety of intake tower structures, and can be used as reference for similar projects.
In order to analyze the effects of different backfill materials and different backfill thickness on the dynamic response of intake towers, we set up a numerical test model that combined 6 types of backfill materials and 4 types of backfill thickness, and conducted dynamic analysis of the intake tower. When the rock ballast was filled, the maximum stress of the area was greatly reduced, and the stress distribution of the contact surface was changed; the thickness of backfill had little influence on the displacement of the top of the tower. Based on the calculation results and analysis of the numerical test, a new type of backfill was designed with rational use of rock ballast backfill. For this type, the junction between the tower and the backfill was not in the position of the concentrated stress. The maximum stress of the contact surface was greatly reduced, and the stress value of the same area was reduced. The large-stress area shifted downwards, and the area became larger and wider, indicating that the new type improved the stress state of the intake tower structure, and was beneficial to the safety of the intake tower. The proposed method was applied to the structure of a water intake tower in a flood discharging tunnel. Comparison was made between the new and original backfill types in terms of the stress time-history curve of the junction between the intake tower back and backfill, as well as the stress nephogram and damage nephogram of the contact surface between the intake tower back and backfill. The results showed that the dynamic response of the contact surface between the intake tower and backfill was greatly improved by the new type of backfill. This backfill method is of great significance to earthquake resistance and safety of intake tower structures, and can be used as reference for similar projects.
2017, 15(3):158-163.
Abstract:
Based on the multi-phase flow & multi-field coupling theory, this paper adopted the finite element method to calculate the temperature distribution of Muyubao landslide as the atmospheric temperature changes. Further, it analyzed the influence of atmospheric temperature changes on the slope seepage according to the correlation between temperature and viscosity of water. The results of calculation showed that the effect of atmospheric temperature on temperature of the slope body is limited to the shallow surface; as the depth increases, the influence decreases and the hysteresis increases concurrently. The mobility of the water is affected by the change of the slope body’s temperature and it can change the water permeability in the inner slope. The effect of atmospheric temperature on permeability coefficient of the slope has a nonlinear relationship with depth. The effect of atmospheric temperature on the permeability coefficient declines as the depth increases. Generally, the permeability coefficient of the slope no longer change significantly when the depth is deeper than the maximum depth of infiltration. The permeability coefficient of the slope shows seasonal variation with the atmospheric temperature. The permeability coefficient decreases with the increase of depth when the atmospheric temperature is higher than the soil in summer. In contrast, the permeability coefficient increases with the increase of depth in winter.
Based on the multi-phase flow & multi-field coupling theory, this paper adopted the finite element method to calculate the temperature distribution of Muyubao landslide as the atmospheric temperature changes. Further, it analyzed the influence of atmospheric temperature changes on the slope seepage according to the correlation between temperature and viscosity of water. The results of calculation showed that the effect of atmospheric temperature on temperature of the slope body is limited to the shallow surface; as the depth increases, the influence decreases and the hysteresis increases concurrently. The mobility of the water is affected by the change of the slope body’s temperature and it can change the water permeability in the inner slope. The effect of atmospheric temperature on permeability coefficient of the slope has a nonlinear relationship with depth. The effect of atmospheric temperature on the permeability coefficient declines as the depth increases. Generally, the permeability coefficient of the slope no longer change significantly when the depth is deeper than the maximum depth of infiltration. The permeability coefficient of the slope shows seasonal variation with the atmospheric temperature. The permeability coefficient decreases with the increase of depth when the atmospheric temperature is higher than the soil in summer. In contrast, the permeability coefficient increases with the increase of depth in winter.
2017, 15(3):164-170.
Abstract:
Given that the construction of sea-crossing bridges may have adverse effects on rivers, a plane two-dimensional hydrodynamic numerical model was established. The model was tested and proven to be valid with the measured data of tide water, and was used to analyze the effects of the engineering on the rise of water level, the changes of flow regime, as well as the depth of riverbed scour. The study indicated that the sea-crossing bridge engineering will cause a slight rise in the backwater height of the rivers. The maximum backwater height is only 6 cm. But the flow regime will vary greatly as numerous vortices will emerge at the vicinity of the bridge location. These influences will result in local scour of the riverbed, and the maximum scour depth is 0.83 m.
Given that the construction of sea-crossing bridges may have adverse effects on rivers, a plane two-dimensional hydrodynamic numerical model was established. The model was tested and proven to be valid with the measured data of tide water, and was used to analyze the effects of the engineering on the rise of water level, the changes of flow regime, as well as the depth of riverbed scour. The study indicated that the sea-crossing bridge engineering will cause a slight rise in the backwater height of the rivers. The maximum backwater height is only 6 cm. But the flow regime will vary greatly as numerous vortices will emerge at the vicinity of the bridge location. These influences will result in local scour of the riverbed, and the maximum scour depth is 0.83 m.
2017, 15(3):171-176.
Abstract:
To study the pressure characteristics in the stilling basin of a stepped spillway without anti-arc, we chose a reservoir and used the physical model test method to study the pressure characteristics including time-average pressure, fluctuating pressure intensity, and peak pressure pulsation in the stilling basin of a stepped spillway. The results showed that all the time-average pressure was positive in the stilling basin. When the flow regime was skimming flow and transition flow, the time-average pressure became large in the flow impact area, reaching a maximum of 0.926 kPa; it reached the minimum in the downstream rebound zone. The time-average pressure varied slightly when the flow regime was nappe flow, and increased with the increase of flow. The variation patterns of the fluctuating pressure intensity and peak pressure were basically consistent. They both increased with the flow on the whole. The maximum value appeared in the flow impact zone. The maximum fluctuating pressure was 1.198 kPa. It then decreased gradually in the downstream direction until it became stable. The step size hardly affected the time-average pressure and fluctuating pressure on the floor of the stilling basin. The dominant frequencies of fluctuations in the stilling basin were 0.01 – 4 HZ, which belonged to the low-frequency vibration and will not endanger the safety of drainage buildings.
To study the pressure characteristics in the stilling basin of a stepped spillway without anti-arc, we chose a reservoir and used the physical model test method to study the pressure characteristics including time-average pressure, fluctuating pressure intensity, and peak pressure pulsation in the stilling basin of a stepped spillway. The results showed that all the time-average pressure was positive in the stilling basin. When the flow regime was skimming flow and transition flow, the time-average pressure became large in the flow impact area, reaching a maximum of 0.926 kPa; it reached the minimum in the downstream rebound zone. The time-average pressure varied slightly when the flow regime was nappe flow, and increased with the increase of flow. The variation patterns of the fluctuating pressure intensity and peak pressure were basically consistent. They both increased with the flow on the whole. The maximum value appeared in the flow impact zone. The maximum fluctuating pressure was 1.198 kPa. It then decreased gradually in the downstream direction until it became stable. The step size hardly affected the time-average pressure and fluctuating pressure on the floor of the stilling basin. The dominant frequencies of fluctuations in the stilling basin were 0.01 – 4 HZ, which belonged to the low-frequency vibration and will not endanger the safety of drainage buildings.
2017, 15(3):177-182.
Abstract:
To control the temperature and prevent cracks of concrete in culvert projects, we developed a fully automatic digital temperature measurement system. The hardware was composed of digital temperature sensors, an acquisition unit, and GPRS DTU. The software part included the central server and client software. The system has realized unattended operation, multi-point remote measurement, and real-time data sharing within the coverage of GPRS public wireless network. It is small in size, requires no wiring, runs steadily, and has high accuracy. Through several practical applications, it was proved to be stable and reliable. Based on the measured data and the numerical calculation of 3D unsteady temperature field, we retrieved the hydration heat parameters of a specific project. The specifications for P.O 42.5 were: m = 0.69, n = 0.56; and the inverted results were: m = 1.85, n = 0.79. According to these two groups of parameters, we calculated the 3D temperature stress, and obtained completely different results. The former did not exceed the standards, but the latter exceeded several standards and required crack-control measures to ensure the safety of the structure. Therefore, temperature monitoring and parameter inversion are very necessary for practical projects.
To control the temperature and prevent cracks of concrete in culvert projects, we developed a fully automatic digital temperature measurement system. The hardware was composed of digital temperature sensors, an acquisition unit, and GPRS DTU. The software part included the central server and client software. The system has realized unattended operation, multi-point remote measurement, and real-time data sharing within the coverage of GPRS public wireless network. It is small in size, requires no wiring, runs steadily, and has high accuracy. Through several practical applications, it was proved to be stable and reliable. Based on the measured data and the numerical calculation of 3D unsteady temperature field, we retrieved the hydration heat parameters of a specific project. The specifications for P.O 42.5 were: m = 0.69, n = 0.56; and the inverted results were: m = 1.85, n = 0.79. According to these two groups of parameters, we calculated the 3D temperature stress, and obtained completely different results. The former did not exceed the standards, but the latter exceeded several standards and required crack-control measures to ensure the safety of the structure. Therefore, temperature monitoring and parameter inversion are very necessary for practical projects.
2017, 15(3):183-189.
Abstract:
Rockbursts in tunnels can be a significant hazard. Based on a large amount of micro-seismic information and hundreds of rockbursts that occurred in four deep headrace tunnels at a hydropower station in Sichuan province, China, we combined numerical calculation with micro-seismic monitoring in order to study the evolution processes of rockbursts. The achieved results are as follows: the excavation scheme, speed, and buried depth can affect the stability of the surrounding rocks in deep, hard-rock tunnels during construction. As the excavation step length, speed, and buried depth increase, the micro-seismic energy rises, and so do the frequency and intensity of rockbursts. The results can provide reasonable and scientific basis for prediction and prevention of rockbursts during underground tunnel excavation under high geostress.
Rockbursts in tunnels can be a significant hazard. Based on a large amount of micro-seismic information and hundreds of rockbursts that occurred in four deep headrace tunnels at a hydropower station in Sichuan province, China, we combined numerical calculation with micro-seismic monitoring in order to study the evolution processes of rockbursts. The achieved results are as follows: the excavation scheme, speed, and buried depth can affect the stability of the surrounding rocks in deep, hard-rock tunnels during construction. As the excavation step length, speed, and buried depth increase, the micro-seismic energy rises, and so do the frequency and intensity of rockbursts. The results can provide reasonable and scientific basis for prediction and prevention of rockbursts during underground tunnel excavation under high geostress.
2017, 15(3):190-196.
Abstract:
Natural vibration frequency is related to the safety of hydropower stations under dynamic loads. It is significant to predict and control the frequency during the design phase. We performed modal analysis on the hydropower house using the ANSYS finite element software. Thus, we obtained the natural vibration frequency of the structure under the different material parameters (elasticity modulus and bulk density) of the first- and second-stage concrete and the foundation. We estimated the correlation between the structure's natural vibration frequency and the main material parameters using the systematical analysis method based on grey relational grade. The following conclusions were reached. When only the elasticity modulus was considered, the elasticity modulus of the foundation had the largest influence on the natural vibration frequency, followed by the first-stage concrete and the second-stage concrete of the hydropower house. When only the concrete bulk density was considered, the influence of the second-stage concrete bulk density was slightly larger than that of the first-stage concrete. When both elasticity modulus and concrete bulk density were considered, the concrete bulk density had a greater influence than elasticity modulus on the natural vibration frequency of the hydropower station, and their correlations with the natural vibration frequency showed little difference. The research results can provide reference for controlling the natural vibration frequency of similar structures.
Natural vibration frequency is related to the safety of hydropower stations under dynamic loads. It is significant to predict and control the frequency during the design phase. We performed modal analysis on the hydropower house using the ANSYS finite element software. Thus, we obtained the natural vibration frequency of the structure under the different material parameters (elasticity modulus and bulk density) of the first- and second-stage concrete and the foundation. We estimated the correlation between the structure's natural vibration frequency and the main material parameters using the systematical analysis method based on grey relational grade. The following conclusions were reached. When only the elasticity modulus was considered, the elasticity modulus of the foundation had the largest influence on the natural vibration frequency, followed by the first-stage concrete and the second-stage concrete of the hydropower house. When only the concrete bulk density was considered, the influence of the second-stage concrete bulk density was slightly larger than that of the first-stage concrete. When both elasticity modulus and concrete bulk density were considered, the concrete bulk density had a greater influence than elasticity modulus on the natural vibration frequency of the hydropower station, and their correlations with the natural vibration frequency showed little difference. The research results can provide reference for controlling the natural vibration frequency of similar structures.
2017, 15(3):197-203.
Abstract:
Using Reynolds averaged Navier-Stokes (RANS) equation, the standard S-A turbulent flow model, SIMPLEC algorithm, and Computational Fluid Dynamics, we conducted numerical simulation of the flow field in the flow channel of the water turbine at Yunxi hydropower station under different schemes, and analyzed the effects of the impeller diameter, blade airfoil, number of blades, blade angle, wheel hub, impeller speed, guide vane airfoil, angle between the guide vane axis and centerline of the unit, number of guide vanes, installation positions of blades and guide vanes, and guide vane opening on the performance of the water turbine. When there were 3 blades, the performance of the turbine unit was optimal. The maximum efficiency of the unit occurred when the speed was 187.5 r/min and the number of guide vanes was 15. We optimized the parts of the original flow channel, and applied the optimized runner to the power station for numerical calculation. According to the results of numerical simulation of the whole flow channel, we predicted the hydraulic performance of the unit after renovation. According to the numerical calculation results, we made a model water turbine and conducted model tests and prototype tests. The results showed that the numerical simulation, model test, and on-site operation results had a consistent variation trend, and that the numerical simulation results can basically accurately reflect the external characteristics and internal flow field characteristics of the power station.
Using Reynolds averaged Navier-Stokes (RANS) equation, the standard S-A turbulent flow model, SIMPLEC algorithm, and Computational Fluid Dynamics, we conducted numerical simulation of the flow field in the flow channel of the water turbine at Yunxi hydropower station under different schemes, and analyzed the effects of the impeller diameter, blade airfoil, number of blades, blade angle, wheel hub, impeller speed, guide vane airfoil, angle between the guide vane axis and centerline of the unit, number of guide vanes, installation positions of blades and guide vanes, and guide vane opening on the performance of the water turbine. When there were 3 blades, the performance of the turbine unit was optimal. The maximum efficiency of the unit occurred when the speed was 187.5 r/min and the number of guide vanes was 15. We optimized the parts of the original flow channel, and applied the optimized runner to the power station for numerical calculation. According to the results of numerical simulation of the whole flow channel, we predicted the hydraulic performance of the unit after renovation. According to the numerical calculation results, we made a model water turbine and conducted model tests and prototype tests. The results showed that the numerical simulation, model test, and on-site operation results had a consistent variation trend, and that the numerical simulation results can basically accurately reflect the external characteristics and internal flow field characteristics of the power station.
2017, 15(3):204-208.
Abstract:
We took a two-dimensional hydrofoil calculation model as the research object, and adopted the method of numerical simulation. The movement of the hydrofoil cavity in the cavitation process was obtained through the numerical simulation study on different cavitation models and turbulence models. The result showed: In different types of cavitation models, the cavitation process of this hydrofoil included the generation, development, fall-off, and burst of vacuoles, and the process showed obvious periodicity. The simulation result of S-S cavitation model was consistent with the actual movement. The S-S cavitation model can well simulate the flow around a hydrofoil in the cavitation process.
We took a two-dimensional hydrofoil calculation model as the research object, and adopted the method of numerical simulation. The movement of the hydrofoil cavity in the cavitation process was obtained through the numerical simulation study on different cavitation models and turbulence models. The result showed: In different types of cavitation models, the cavitation process of this hydrofoil included the generation, development, fall-off, and burst of vacuoles, and the process showed obvious periodicity. The simulation result of S-S cavitation model was consistent with the actual movement. The S-S cavitation model can well simulate the flow around a hydrofoil in the cavitation process.
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