Study On Seismic Dynamic Response Of Layered Composite Rock Slope Based On Shaking Table Model Test

China is a geological tectonic environment with many mountains and earthquakes,which makes it a very serious country in the world.Many engineering projects will be carried out in western mountainous areas and strong earthquake areas,inevitably involving many slope seismic stability problems.Therefore,it is of great theoretical and practical significance to strengthen the study of dynamic response characteristics and deformation failure mechanism of slope under earthquake.Layered composite rock slope is a very common slope structure in nature.There are many kinds of lithology in the rock layer.There are structural planes between the rock layers,which constitute the layered composite rock slope.In the process of earthquake,the deformation process,dynamic response and the final position of deformation and failure of layered composite rock slope are very important to understand the dynamic deformation and failure mechanism and the cause of geological disaster.In this paper,through the small-scale shaking table model test,the deformation and failure characteristics of layered composite rock mass are found out,and the seismic dynamic response and deformation and failure mechanism of layered composite rock slope are analyzed.The main work and results are as follows:(1)After the earthquake,the field investigation of Dong He Kou landslide was carried out to analyze the physical parameters of the residual rock mass structure in the sliding area and determine the similarity coefficient of the generalized model of layered composite rock mass.Using the measured seismic wave data of local seismic station as the dynamic loading scheme and using various monitoring sensors,the shaking table test is completed.(2)In the process of shaking table test,the whole process of macro deformation and failure of slope model is recorded by video and photography.The test results show that the dynamic response of layered composite rock slope is not obvious at the initial stage of excitation.With the increase of excitation intensity(input amplitude > 0.7g),cracks begin to develop on the top of the broken body(dolomite layer)of the slope model,and tension cracks occur on the back edge of the slope.After that,the increasing excitation intensity made the dolomite completely disintegrated and slide down,and the deformation and dislocation occurred between the carbonaceous slate and the phyllitic slate in the middle of the slope.When the slope model is finally damaged under the sine wave excitation,the tension crack belt at the back edge of the slope is through,the upper part of the phyllitic slate is sheared along the through belt,and the carbonaceous slate is finally bulging.The test results are not cut out from the carbonaceous slate when the prototype landslide is destroyed,which may be due to the limited size of the physical model and the insufficient height amplification effect of the carbonaceous slate.(3)After preprocessing the data collected in the test,the following conclusions are obtained: the horizontal acceleration response of the layered composite rock slope shows a three-stage growth.When the input amplitude in the first stage of loading is less than 0.5g,the peak response of each elevation point of the slope hardly changes,and the amplification coefficient is less than 1.In the second stage,the peak response begins to increase during the input amplitude of 0.5g-0.7g,and the amplification coefficient is gradually greater than 1,resulting in elevation amplification effect.In the third stage,when the input amplitude is more than 0.8g,the peak response increases greatly,and the maximum amplification coefficient at the top of slope can reach 1.8.At the same time,the three-stage step decline of the horizontal dynamic characteristics of the slope also proves that the deterioration process of the internal structure of the slope model leads to the gradual increase of the dynamic response.In addition to the same three-stage growth of vertical acceleration response and horizontal acceleration response,there is also a strong irregular amplification effect.Specifically,under the condition of high excitation amplitude,the acceleration peak response of carbon slate layer is weakened co MPared with other rock layers,and the amplification coefficient of carbon slate layer slope surface is 12% weaker than that of other rock layers,and 33% weaker than that of other rock layers.From the vertical acceleration Fourier spectrum,it is found that with the increase of excitation intensity,the carbonaceous slate layer shows high-strength response at 11 hz and 22 Hz,while other layers only respond at 11 hz.The second-order natural frequency of the vertical dynamic characteristic transfer function(only the first-order horizontal dynamic characteristic)explains why the vertical dynamic response of slope is more active than the horizontal dynamic response.(4)According to the analysis of the dynamic response of the carbonaceous slate interlayer,it is found that the horizontal dynamic response of the carbonaceous slate layer under different intensity excitation is generally consistent with that of the slope model.In the vertical excitation,the acceleration spectrum response of the carbonaceous plate shows that with the increase of the excitation amplitude,the slope surface has more high-intensity response frequency(11hz and 15Hz)than other positions in the rock.Moreover,the displacement response of the slope surface of carbonaceous slate increases irregularly under vertical excitation,and the maximum absolute displacement increases by 40% co MPared with that under horizontal excitation.This shows that the nonlinear structure(carbonaceous plate rock)in the layered composite rock mass enters into the nonlinear response stage when its layered structure changes(bulging or dislocation)with the increase of excitation amplitude.It makes the whole slope model show irregular amplification effect at high excitation intensity.(5)Using FLAC3 D for numerical simulation,it is found that the dynamic characteristics of numerical model and physical model are consistent.The law of acceleration dynamic response is similar to the physical model,and there is a more obvious mutation in the amplification coefficient when the vertical excitation occurs.The nonlinear dynamic response of the numerical model is related to the change of the physical properties of the carbonaceous slate.The greater the difference of the physical properties of the layered composite rock slope,the more intense the change of the nonlinear dynamic response of the slope.