水利工程中隧洞施工通常采用全部开挖完成再衬砌的方法。如针对开挖施工的短暂状态采用稳定渗流计算分析其对地下水环境的影响，并不符合实际，且往往会夸大地下水位降落的幅度和影响范围，因此采用非稳定渗流数值模拟技术来评价将更为合理。以某水电站发电引水隧洞施工为例，采用饱和-非饱和非稳定渗流理论，建立了引水隧洞区域的三维有限元模型，对隧洞开挖过程中区域地下水非稳定渗流场进行了数值模拟，总结分析了隧洞从开始挖掘到贯通过程的地下水变化规律并进行地下水环境影响评价。结果表明：采用三维非稳定渗流分析预测隧洞开挖过程中地下水位降落和降落漏斗扩大的过程是可行的；该工程引水隧洞开挖对该区域地下水影响较小，地下水补排关系总体无变化。

During the construction process of tunnel excavation in a hydro-project, the method of all excavation completed before lining was commonly used. As for the seepage flow stability calculation on tunnel excavation temporary state to impact groundwater environment, which is not in line with the actual situation, and often amplifies the water level fluctuation and effective range. In view of this, adopting the technique of unsteady seepage numerical simulation to assess the impact on groundwater environment will be more reasonable. Taking the construction process of a diversion tunnel as an example, based on unsteady saturated and unsaturated seepage theory, the three-dimensional finite element numerical model was established to calculate the transient seepage field of tunnel excavation area. The tunnel groundwater variation from commencement to completion of works was summarized. Groundwater environmental impact assessment on the process of tunnel excavation was done. The results showed that (1) it was feasible to predict the process of water level falling and affective range enlarging by three-dimensional unsteady seepage flow analysis; (2) the groundwater in this region was less effected by excavation of diversion tunnel and groundwater recharge and discharge relations remained unchanged.

江苏高校优势学科建设工程资助项目（水利工程）；江苏省自然科学基金青年基金项目（BK2012410）；中央高校基本业务费项目（2014B11914）