深井降水条件下穿沁引水隧洞渗流分析

Seepage Analysis of Chuangqi Diversion Tunnel Under Condition of Deep Well Dewatering

深井降水会导致地下水位下降、降低土体强度和稳定性,从而影响引水隧洞施工安全。为研究深井降水对施工期隧洞渗流场的影响,以西霞院水利枢纽输水及灌区工程穿沁隧洞为依托,建立了该隧洞三维渗流有限元计算模型,考虑隧洞施工计划和沁河水位变化,分析了深井降水和未降水情况下隧洞渗流特性。结果表明,深井降水会对隧洞开挖产生影响,使深井周围渗流场位势分布特征发生改变,浸润面形成降落漏斗,水位等值线在深井附近呈回水环状。深井降水相较于深井未降水时的最大渗透坡降、单宽渗透流量分别增加了18.6、3.3倍,各工况下土层渗透稳定均满足要求。研究成果可为类似引调水工程的设计和施工提供参考依据。

Dewatering in deep well would lead to the decline of groundwater level and reduce the strength and stability of the soil, which affects the construction safety of the diversion tunnel. In order to study the influence of deep well dewatering on the seepage field of the tunnel during the construction period, a three-dimensional seepage finite element model of Chuanqin tunnel of Xixiayuan water control project and irrigation area project was established. The construction plan of the tunnel and the change of Qinhe water level were considered to analyze the seepage characteristics of the tunnel under the conditions of deep well dewatering and without dewatering. The results show that the dewatering of the deep wells affects the tunnel excavation, changes the potential distribution characteristics of the seepage field around the deep well, forms a falling funnel on the infiltration surface. The water level contour is in a backwater ring near the deep wells. Compared with the deep well without dewatering, the maximum seepage gradient and unit width seepage flow of deep well dewatering are increased by 18.6 times and 3.3 times, respectively, and the seepage stability of soil layer under all working conditions meets the requirements. The research results can provide a basis for the design and construction of similar water diversion projects.