新龙水电站库区倾倒变形体数值模拟分析

Numerical Simulation of Toppling Rock Mass of Xinlong Hydropower Station

新龙水电站是雅砻江上游梯级电站开发甘孜—新龙段4级开发中的第4级电站,是以发电为主的电站。水电站右岸近坝库段大范围发育有倾倒变形体,总体积约1 600万m3。该变形体在水库蓄水后,受地下水位升高、浸泡影响,变形体岩体的抗剪强度指标降低,极易导致变形体边坡失稳,从而对大坝、泄洪(放空)洞、电站引水口等建筑物安全构成威胁。针对该倾倒变形问题,通过对倾倒变形体工程地质特性及失稳模式等分析,建立边坡离散元的数值计算模型,得出岩体倾倒变形特征和变形破坏机理发展过程,从倾倒变形体的变形特征上来看(以地震工况为例),边坡变形体破坏主要位于强倾倒变形体中,弱倾倒变形体破坏不明显。强倾倒变形体主要表现为向临空面方向发生倾倒—弯曲—拉裂—折断的变形破坏模式,先在坡脚及顶部发生剪切破坏,中间形成锁固段,后剪切贯通整体下滑,成果可为倾倒变形体的稳定性评价及工程开挖施工提供借鉴。

Xinlong hydropower station is the fourth station of Ganzi-Xinlong segment of cascade hydropower stations in the upstream of the Yalong River.Toppling rock mass develops widely near the dam on the right bank,with a total volume of about 16 million m3.After the reservoir impoundment,the shear strength of the deformation rock is reduced under the effect of groundwater level rise and soaking,leading to the instability of the toppling rock slope and threatening the safety of dam,flood discharge tunnel and water inlet.By analyzing the engineering geological condition and instability mode,we established discreet element model of the toppling rock slope and obtained the deformation characteristics and failure mechanism of the toppling rock.In seismic condition,the deformation failure of slope mainly happens in strong toppling rockmass,which first inclines towards the free face,and finally breaks off.It has features of landslide because shear failure first happens at the slope toe and top and then penetrates through the whole slope.It also has features of collapse in seismic vibration condition.This research could be a scientific basis for the stability evaluation and slope excavation.