| The toppling deformation body in front of the dam of the Gushui hydropower station in Lancang River is a typical counter-tilt layered rock slopes,which has the characteristics of large deformation,wide range,Strong weathering and unloading effect,developed joint,strong seismic and tectonic activity.So the problem of seismic stability is extremely prominent.Therefore,on the basis of on-site investigation,this paper studies the dynamic response characteristics and the stability of the toppling deformation body in front of the dam through a combination of physical simulation and numerical simulation and puts forward the reinforcement measures of the slope on the basis.This shows that this study has great engineering practical value and theoretical research value and the main research results are as follows:(1)On the basis of a detailed investigation of the toppling deformation body in front of the dam,according to deformation characteristics,the slab inclination angle,the maximum tension in the layer,the unit tension in the layer,the unloading deformation of the rock body and the weathering degree of the rock body,the deep toppling deformation body is divided into: A extremely strong toppling deformation area(0?71m),strong toppling deformation area B(13?112m),weak toppling deformation area C(29m? Undisclosed),original rock D area(90.7m? Undisclosed).The research foundation for slope dynamic response was provided.(2)Using the dumping deformation body in front of the dam as a prototype,an counter-tilt layered slope test model was generalized.The model slope was built by using prefabricated test blocks and the slope was loaded dynamically through a selfmade model box.On the basis of that the dynamic response characteristics and the deformation failure process of counter-tilt layered rock slopes was studied.The results show that: The horizontal and vertical accelerations have obvious elevation magnification effect and surface magnification effect,and the change of ground motion parameters has great influence on the distribution of acceleration;Under the action of earthquake force,the slope first appeared shear failure at the foot of the slope,and gradually extends upward,which causes rapid toppling deformation of the rock slab in the middle and upper part of the slope,and squeezed the lower rock mass and generated greater rock pressure.Finally,shearing and breaking of the rock slab introduced that a continuous fracture surface formed in the slope and evolved into a potential landslide body.The landslide body may be cut along the foot of the slope,and the whole shear slip failure occurs.(3)In PFC2 D,the numerical calculation model of the frontal dam-deformation body was established.Analyzed the dynamic response law of the slope and the deformation and failure process by inputting the Wolong wave.The rest results showed that: Under the action of earthquake,the horizontal acceleration of rock mass in zone A and zone B of the slope is obviously enlarged,and the velocity time history curve is obviously distorted compared with the input wave.The amplification effect of horizontal acceleration is not obvious in zone C and D,and the velocity time history curve has no obvious distortion compared with the input wave.Under the seismic effect,due to the amplification effect of the acceleration,slope B area rock deformation trend is large,which will squeeze the lower A area rock mass in the lower zone A,resulting in the gradual stress concentration of the zone A rock mass and causing a slowly shear deformation.At the same time,the shear deformation of the lower rock mass provided space for the upper toppling rock deformation.The upper rock body has a strong toppling deformation and the displacement band characteristics has been increasing gradually.the rock body appears a lot of damage in the obvious displacement zone,and generated a gradually increasing displacement finally.The rock masses in Zone A and Zone B in the slope are damaged due to toppling deformation of the upper part and shear deformation of the lower part.Under the action of earthquake,the deformation and failure process of the toppling deformation body in front of the dam can be divided into: slope body shock cracking-toppling intensified-slope foot collapse-shear slip.(4)In PFC3 D,the numerical calculation model of the frontal dam-deformation body was established to research the dynamic response characteristics of the slope toppling deformation body.The test results show that: According to the dynamic response of the toppling deformation body in front of the dam and the numerical analysis results of the reinforcement finite element analysis,the stress of the toppling deformation body in front of the dam is concentrated at the fault under the earthquake.Then,the small deformation at the fault causes large deformation of rock mass at the upper slope and gradually appears a banded displacement characteristics.Finally,the rock masses in the areas A and B above the slope fault altitude have an overall instability and failure.(5)The slope appears as unloading and loose deformation of the shallow surface of the rock mass under static conditions after the excavation of the rock mass in area A.And under the strong earthquakes,The slope appears as the overall high shear damage of the upper and middle rock masses in area B.Under the earthquake,as the slope is reinforced with "anchor cable + frame beam" after the excavation,the displacement development is restricted obviously.The rock mass near the slope surface is combined with prestressed anchor cable to form a continuous compression zone,and this compression effect then passes through the frame bring about a greatly increasing compressive stress in the slope.Then,the distribution range and the extreme value of tensile stress in the excavated slope are reduced significantly.There is no tensile plastic zone appeared in the excavated slope during seismic loading and the extreme value of shear strain increment is not penetrated.So,the dynamic stability of the slope is good. |
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