基坑涌水量较大情况下边坡稳定性分析与支护研究

Slope Stability Analysis and Supporting Study under the Condition of Larger Foundation Pit Water Inflow

拟建场地位于六枝向斜轴部,裂隙发育,为向斜两翼地下水径流的汇水区。通过抽水试验,确定了水文地质参数,预算地下室开挖1m后,基坑的涌水量为4420.64m3/d。场地开挖后,形成的土质边坡高度为2～3.22m,岩质边坡为2.95～7.03m。由于地下水位埋深为3.00m左右,且基坑涌水量较大,因而地下水对边坡的稳定性影响较大.采用极限平衡法预测东部裙楼的南东面,当后缘裂隙充水高度大于0.57m时,边坡的稳定系数小于1.25,须强制支护,东、西部的稳定系数为2.58,边坡稳定,但仍需进行垂直支护;西部裙楼的南西面的稳定系数为0.83,属不稳定边坡,需进行降水和垂直支护。经过分析,确定基坑岩质边坡为70°,土质边坡为45°。提出了基坑支护方案和土钉墙的支护、施工要求。

Proposed site is situated at the fissure well developed Luzhi syncline axis, the eatchment area of groundwater runoff from both limbs of the syncline. The pumping test obtained hydrogeological parameters; computed foundation pit inflow is 4420.64m^3/d after lm excavation of the basement. Site excavated soil slope height is 2-3.22m, rock slope 2.95-7.03m. Since the groundwater table depth about 3.00m, and pit inflow is rather large, thus larger impact to slope stability from groundwater. To use limit equilibrium method, predicted the east podium building southeast side, when posterior edge fissure water filling height above 0.57m, coefficient of stability 〈1.25, forced supporting is needed, east and west sides coefficient of stability is 2.58, slopes stable, but vertical supporting is still needed; the west podium building southwest side coefficient of stability 0.83, belongs to unstable slope, water table lowering and vertical supporting are needed. After analysis, foundation pit rock slope angle 70o and soil slope angle 450 are determined, foundation pit supporting scheme and soil nail wall supporting and construction requirements put forward.