Study On Seismic Design Technology Of Accumulation Landslide Reinforced By Incline-Straight Combined Micro-piles

China has a vast territory,numerous mountains,complex geological structure and high frequency of geological disasters.As one of the major geological hazards in nature,landslides have received increasing attention from domestic and international research scholars.As a kind of support structure with the advantages of fast and simple construction and low cost,mini-piles are widely used in earthquake relief and small and medium landslide prevention and control.The current academic research on landslide prevention and control technology under static load has been relatively complete,but the research on landslide management under dynamic load is relatively scarce,so the seismic design of mini-pile reinforced landslide is a very important research direction.By studying the force deformation characteristics of mini-pile structure inside the landslide under seismic action,it provides some reference for mini-pile landslide management.In southern shaanxi accumulation landslide in this paper as the research background,the independent micropile,transverse tie beam micropile and inclined straight combination micropile are used as the research objects,and the change law of pile top displacement,pile shear force,bending moment and axial force distribution law of the three types of system micropile under earthquake action are studied through basic physical test,GDS dynamic triaxial test and numerical simulation test.The comparative analysis shows that the mini-pile structure of the inclined and straight combination can resist more landslide thrust than the other two types of mini-pile structures,which indicates that the proposed inclined and straight combination mini-pile structure is more effective in reinforcing landslides and has stronger seismic capacity.Combined with the above mentioned,the overall seismic conceptual design of micro-piles is proposed.Finally,the design and calculation of inclined and straight composite micro-piles are carried out based on engineering examples.The main conclusions of the study include the following:(1)The static parameters such as water content,density,unloaded swelling rate and dynamic parameters such as dynamic shear modulus and damping ratio are obtained through the basic physical experiment and GDS dynamic triaxial test;according to the data,the dynamic shear modulus of soil gradually decreases with the increase of surrounding pressure and the damping ratio gradually increases.(2)Use FLAC 3D to build a landslide model,select model parameters and verify the reasonableness of the model to ensure that the built model meets the test requirements.(3)By comparing the force and deformation characteristics of the pile under the action of peak acceleration in X and Z directions,it is obtained that the horizontal seismic action has more influence on the stability of the landslide than the vertical seismic action;the force value and displacement of the top of the pile of each three rows of mini-piles of three types of systems are: the first row is the largest,the second row is the second and the third row is the smallest;the larger the peak seismic acceleration is,the larger the force and deformation of the mini-pile is.(4)By analyzing the force and deformation data and change trend of each monitoring point of mini-pile,we get that the shear force of mini-pile is “>” distributed,and the shear force near the slip surface reaches the positive maximum;the pile bending moment is “S” type,and the maximum positive bending moment appears near the middle of the slip bed.The maximum positive bending moment appears in the middle of the slide bed,the maximum negative bending moment appears in the middle of the slide body,and the bending moment near the slide surface is almost zero;the axial force distribution of the first and third rows of each pile body has symmetry,the first row of piles is “inverted Z” distribution,and the third row of piles is “Z”distribution,showing “one pull and one pressure” distribution.The first row of piles is“inverted Z” distribution,and the third row of piles is “Z” distribution,showing the “one pull and one compression” force characteristics.(5)A comprehensive comparison analysis shows that the diagonal combination mini-pile has smaller displacement of the pile top,smaller pile shear force,smaller pile moment and larger pile axial force than the independent mini-pile and transverse link beam mini-pile,which indicates that the mini-pile structure has better reinforcement effect on the landslide;The overall seismic concept design of the mini-pile is proposed,and the design calculation is combined with the actual arithmetic example.