DEFORMATION MECHANISM AND STABILITY PREDICTION OF A DEFORMATION MASS IN LEFT BANK SLOPE OF QINGDAHE LOCATED AT LIANGHEKOU HYDROPOWER STATION, YALONG RIVER

The flood discharge inlet of Lianghekou hydropower station could decorate at the left bank slope of Qingdahe River. A new deformation rock mass (Ⅳ) is found after three were identified in the previous stages. The construction safety is largely dependent on the stability of the deformation rock mass. On the basis of engineering geological methods such as exploratory tunneling and stereographic projection, the deformation mechanism is analyzed. The rock slope is toppling with thin and medium-thickness rock stratum. As the uplift of Qinghai-Tibet Plateau and incision of Qingdahe River, the slope is unloaded at the free face. The thin rock stratum is toppling and buckling at the slope toe and then the upper location. The deformation is aggravated with river erosion and a slip plane could be formed gradually. Landslide tends to occur with external disturbances e.g.rainstorm or earthquake. The deformation mass at the upper slope could get further damaged after slope toe failure. Because the thickness of rock stratum is small, the joint group nearly vertical to the bedding plane is developed well and the rock mass is strongly toppling, buckling and fragmentized. The stability is studied quantitatively with Geo-slope software. The results show that the deformation mass Ⅳ is in the limit equilibrium state and could get unstable after the deformation masses located at the lower part of the slope is clear off. Some proper treatment measures are then suggested.