Physical Model Test And Numerical Simulation Study On Deformation Process Of Old Landslide Under Loading

Loading on slopes is one of the most common human activities in mountain areas and one of the most common landslide inducing factors.In mountain towns,due to the shortage of construction land,people or the government often carry out engineering construction after filling and leveling the land behind the old landslide,resulting in disaster events of the revival of the old landslide.Therefore,studying the deformation and failure characteristics of the old landslide after loading and its revival conditions can theoretically enrich the understanding of the internal mechanism of landslide deformation and failure,and has important practical application value.In this paper,physical model tests and numerical simulation methods are used to explore the revival deformation process and revival criterion of the old landslide after loading.In this study,through physical simulation tests,the change characteristics of surface displacement,deep displacement and pore water pressure of the landslide model in the loading process are monitored in real time by marker tracking,flexible fiber grating sensor and seepage pressure sensor.On the basis of physical model tests,Flac3 D and SIGMA/W,which are highly recognized by the industry,are adopted to explore the overall and local revival conditions of landslide and the deformation and failure rules during the revival process.1)Physical model tests show that during the loading process of the first stage platform at the rear of the landslide,the surface displacement increases with the increase of the load,and the landslide displacement presents the basic characteristics of the maximum at the rear and the minimum at the toe of the slope.During the first stage of loading,the displacement of deep part increases obviously.During the loading process of the second-stage platform and the third-stage platform,the surface displacement and the deep displacement did not change.After the model's third stage platform is injected with water,the surface displacement increases slightly,the back of the deep displacement changes greatly,and the front edge hardly changes.The model test results show that the closer to the trailing edge of the landslide,the greater the influence of loading on the stability of the landslide.2)Using the same stability calculation methods(Janbu,Spencer and Morgenstern-Price)in Lizheng software and Geo-Studio software,the calculation results obtained by different methods in the two softwares show that the stability coefficient of the model decreases gradually with the increase of load,but there are obvious differences in magnitude.The results calculated by Morgenstern-Price method and Spencer method are close to each other.The results calculated by the simple cloth method are quite different from those calculated by Morgenstern-Price method and Spencer method.The simple cloth method satisfies the condition of force balance but does not satisfy the condition of moment balance,and the calculation results are conservative,while Morgenstern-Price method and Spencer method satisfy both the condition of force and moment balance,and the calculation results are accurate.Compared with the results of model tests,the results calculated by the three methods of Geo-Studio are closer to reality in Lizheng and Geo-Studio software,and Morgenstern-Price method is relatively more in line with reality.3)The results of Morgenstern-Price method show that the whole model reaches the critical state of instability when the three-stage platform is loaded at 10.71 kPa respectively under staged synchronous loading.The instability critical load of the upper slide is 15.65 kPa,the instability critical load of the middle slide is 21.73 kPa,and the instability critical load of the lower slide is 32.14 kPa.4)Under the instability condition,the failure rule of FLAC3 D and SIGMA/W simulated landslide model is basically the same.The simulation results show that when the model is unstable,the failure of the model starts from the slip zone below the stacking area and advances downward along the slip zone,eventually leading to the plastic zone of the slip zone to be connected and the model to be unstable.The difference between FLAC3 D and SIGMA/W simulation results is mainly shown in the magnitude of displacement.