Strength Characteristics And Seismic Failure Mode Of Loess Slope With Structural Joints

The Loess Plateau,which has the most concentrated and broadest loess development in the world,is one of the four major plateaus in China.The area is densely populated and include the main trunk area of the key pipeline hub project.The Loess Plateau region was damaged by many large earthquakes and hundreds of strong earthquakes,which caused frequent geological disasters and serious loss of personnel and economy.The Earthquake Landslide is one of the worst geological disasters that has the worst impact on the Loess Plateau.Among them,the extensive development of structural joints inside the loess is one of the main triggers for geological disasters that cause the landslides of the loess earthquake.It can not only destroy the soil integrity but also develop into a favorable channel easily for underwater seepage and migration under the loess between joint surfaces.The reflection and refraction of the resulting seismic waves are also important factors leading to the destruction of loess slopes and damage to houses.Therefore,the research of structural joints on the failure mode and stability of loess slopes can not only bring new solutions to the safety prevention problems of structural jointed slopes,but also provide new ideas for the design and construction of slope protection facilities.Necessity for the above research,this paper using unconfined compression test and shear experiment to explored structural joints loess simulation material.Then supplemented PFC discussed the control effect of the joint's location,dip angle and tendency of loess slopes under seismic.The main work and results are as follows:(1)Analyzed the distribution law,development characteristics and occurrence location of typical structural joints in the Loess Plateau.A variety of materials and sample making processes are used to simulate the structural joint surface of loess,which improves the joint making method of laboratory test.A single layer of paper drawing is innovatively used as the joint surface simulation material,which not only can accurately simulate the strength of joint soil,but also can clearly observe the impact of joint on the fracture surface.(2)Four typical failure modes caused by structural joints on loess in unconfined compression tests are summarized,namely sliding failure,sliding shear failure,conjugate shear failure and splitting failure.The failure modes of structural joints on soil are determined Control effect and destruction mechanism.The influence of the change of joint inclination angle on soil failure mode and compressive strength under different water content conditions was analyzed,and the shear strength,cohesion and internal friction of different joint inclination angles and loess under high water content and low water content conditions were clarified.The law of change of soil mechanical parameters such as angle.(3)Under the action of earthquake,the control effect of the change of inclination angle on the failure mode of loess landslide under tectonic joints is studied.When the structural joint is at a low angle,the damage to the slope is the strongest.With the increase of the structural joint inclination,the impact on the slope stability is gradually reduced.The initial failure point of the landslide is generally located at the intersection of the joint extension line and the free surface.At the same time,the formation and extension of the internal fissure network are also closely related to the location of the joint,and the slip surface of the landslide is mostly parallel to the joint surface.(4)Under the action of earthquake,the control effect of the change of inclination angle on the failure mode of loess landslide under tectonic joint under inclination is studied.With the increase of structural joint inclination angle,the influence of joints on slope stability showed a trend of increasing first and then decreasing.Most of the soil fracture network developed along the outer side of the joint.The dip angle and position are closely related.The failure modes are mostly push failure and collapse failure.The sliding surface is approximately perpendicular to the structural joints.For a long time,the loess tectonic joints have rarely studied the mechanical properties and failure modes of loess,mostly based on inductive,statistical,and qualitative descriptions.This research has created a new type of joint simulation through laboratory tests,numerical simulations and other research methods.Quantitatively studied the effect of structural joints on the mechanical properties of loess,and systematically analyzed the control effect of structural joints on the failure mode of loess slopes.Although the factors considered in this study are relatively simple and the setting of joint models is considerably little,I hoped that the relevant conclusions of this study and the new methods proposed can provide a certain reference for the safety evaluation and stability analysis of structural jointed loess slopes.