Study On Dynamic Response Of Anchored Rock Slope Under Strong Earthquake

In the construction of hydropower projects in the southwest of China, stability of high and steep rock slope is an important research topic. This kind of slope is reinforced by prestressed anchor cable, composite structure formed by the action of rock mass and anchor cable. In recent years, southwest region has become a serious earthquake disaster area and many high and steep slopes are faced with severe earthquake test. In 5.12 Wenchuan earthquake, Zipingpu Water Conservancy Project suffered beyond design under the condition of earthquake intensity twice, the water intake slope anchorage showed good seismic performance. The displacement in slope is arranged in the meter, the anchor cable dynamometer monitoring instrument etc. A true record of the slope deformation and anchor stress changes after the earthquake. Based on the experimental results and numerical simulation analysis, the dynamic response of anchored rock slope under strong earthquake is of great significance. The results of this study show that:Under the influence of earthquake, different degrees of permanent displacement occurs in different parts of the slope. The surface displacement is increased by 3.68 ~ 11.52 mm. With the increase of the depth, the increment of displacement decreases. Due to the compression effect of the anchor cable on the slope surface, the surface displacement increment of multi point displacement meter is lower than displacement increment of the adjacent point in the interior. On the same profile, the middle of the slope deformation is greater than the upper slope deformation. On the same elevation, the left side of the slope is larger than the right side. After the earthquake, the main deformation area of each multi point displacement meter is basically the same and the deformation mainly occurs in the interlaminar shear zone of soft rock. The other parts of the slope with the position of the rock mass deformation. When the slope deformes to the free surface, the compression effect of the prestressed anchor cable on the slope surface restrains the deformation of the slope. On both sides of the mountain slope at the boundary of the rock mass has certain constraints and the middle part of the slope is at the absolute free state. These make the slope of the site more easily deformed and the axial force of the prestressed anchor cable is also greater.The results of numerical analysis show that the acceleration and displacement of the slope has some amplification effect. Interlaminar shear zone absorbs the energy of seismic waves cause the dynamic response strongly and the amplification coefficient of PGA is obviously increased. The difference of the different rock strata properties and the poor mechanical properties of the weak and fractured zones lead to the separation of different mechanical properties of the rock mass or the broken rock zone. Finally, the residual deformation of rocks appears. The seismic wave intensity of the interlayer shear zone is significantly weakened, so that the dynamic response of the upper slope is weakened.The axial force of the prestressed cable is slightly fluctuating along with the magnitude of the input seismic wave and increases slowly. The degree variation of axial force is related to the strength of the input seismic wave. Due to the action of earthquake force, the slope is deformed. The anchor cable in the slope constraints the slope deformation development by adjusting the stress state of the slope. The increase of the axial cable force reflects the slope deformation to the free surface. The anchor cable and the slope form a deformation coordination body.When the slope moves to the free surface, the anchor cable will provide a larger anchorage force to limit its movement. When the slope moves to the outside, it can be considered that earthquake disaster response will not happen. The cable structure can effectively reduce the displacement of slope under earthquake action, so as to improve the seismic performance of the slope.