Three-dimensional NPR support technology for rockburst in the Qinling diversion tunnel of the Hanjiang-to-Weihe River Water Diversion Project
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Abstract:
The Hanjiang-to-Weihe River Water Diversion Project area has more tectonic development such as folds and ruptures, and a series of long joints and joint-intensive zones have been developed in the area, which are generally low in the north and high in the south, with gullies and ravines, so rockburst disasters and damage to the original support structure are frequently generated in this section. Therefore, the study on the water diversion project geological survey, analysis of the tunnel surrounding rock explosion damage characteristics and damage patterns is necessary to carry out ultra-deep tunnel rock explosion three-dimensional NPR high-stress compensation support system for early warning and prevention of rock explosion disaster.Using on-site investigation and other methods, the geological conditions of the tunnel and the causes of rockburst damage were analyzed, and comparative testing was carried out to design a rockburst monitoring and early warning test scheme for the northern section of the project area, and a three-dimensional NPR high-stress compensatory support system with the microscopic NPR anchors as the core was put forward. The degree of rockburst control of the surrounding rocks under the new support system and its support effect were analyzed through on-site testing.Field test results show that the three-dimensional NPR high-stress compensation support system with microscopic NPR anchors as the core can force the excavated surrounding rock in the north section of the tunnel to return to the three-dimensional stress state from the two-dimensional stress state employing high constant resistance stress compensation. The use of good mechanical properties of microscopic NPR anchors on the surrounding rock with high constant resistance, and fast pre-tensioning of timely active support, resulting in the application of microscopic NPR anchors in the research section of the micro-seismic energy, frequency are significantly reduced, the number and depth of the burst crater is significantly reduced, the surrounding rock is in a stable state, and the effect of the support and rock explosion control is remarkable.Through on-site exploration and related experiments, it can be seen that the north section of the project area is a super-deep tunnel with complex geological conditions, which is affected by the tectonic stress, and the rock in the area is prone to stress concentration and rockburst phenomena, such as spalling, ejecting, and throwing. The use of traditional small deformation anchors and multi-layer steel arch rigid primary support systems can not effectively prevent the rock explosion disaster, resulting in the frequent occurrence of rock explosions. Based on the theory of excavation stress compensation, put forward to the microscopic NPR anchors as the core of the three-dimensional NPR high-stress compensation support system, combined with on-site monitoring data analysis, the project section of the monitoring and early warning test section in the application of microscopic NPR anchors, micro-earthquake energy, frequency is significantly reduced. The integrity of the surrounding rock improves the depth of the explosion pit, the steel arch frame force and deformation are reduced, the rock explosion disaster has been effectively controlled, and the support effect is remarkable.
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