黄壁庄水库副坝塌陷机理分析

Mechanism Analysis of Collapse of Auxiliary Dam of Huangbizhuang Reservoir

为了调查黄壁庄水库副坝频发塌陷事故的原因,从防渗墙槽壁稳定性角度研究了槽壁稳定性与护壁泥浆重度之间的关系,分析了第六次塌陷前的测试试验结果,并在多种因素共同作用下分析了黄壁庄水库副坝的塌陷机理。结果表明,由于护壁泥浆重度小于设计临界重度,使得槽壁失稳;同时泥浆水渗透到周围非饱和土层,引起土层地下水位上升,尤其是坝基下面的粉土层,在冲击成槽的施工振动、地下水位上升、含水率增加等多种因素的作用下逐渐液化,从而造成承载力降低;另外由于事先未发现基岩中存在溶洞,当成槽钻孔揭穿溶洞时,槽体内的护壁泥浆迅速下沉,槽壁的稳定急剧破坏,致使槽壁完全塌陷。

Based on the stability of trench,the relationship between the stability of trench and unit weight of slurry was studied to investigate frequent collapse of auxiliary dam of Huangbizhuang reservoir.The test before the sixth collapse was analyzed,and the mechanism of collapse of auxiliary dam of Huangbizhuang reservoir was analyzed under the combination of many factors.The results show that the trench lost stability because the unit weight of slurry for protecting wall was less than the designed critical unit weight when the concrete cut-off wall was built.Meanwhile the slurry water penetrated into the surrounding unsaturated soil to cause the underground water level of soil layers rise.Especially,the silty soil under dam foundation gradually liquefied and lost capacity in the condition of construction vibration of hitting into a groove,the rising of water level and the increasing of moisture content of soil.Moreover,since the karst cave was not explored in the bedrock,the slurry for protecting wall in cell body rapidly sunk when karst cave was exposed by the boreholes for concrete cut-off wall.So,the trench stability lost rapidly,and the trench fully collapsed.