Study On Seismic Design Of Micropiles For Landslide Prevention And Control

As a new type of slope supporting structure,micro-pile has simple construction and low cost.It prevents slope instability in slope seismic engineering.The interaction mechanism of micropiles and landslide,and the seismic effect of micropile are still in the stage of recognition and exploration.This article is based on the National Natural Science Foundation project "Study on the Dynamic Interaction of Micropiles and Landslides"(Approval Number:41572261),which based on the shaking table test.With the help of FLAC3 D simulation software,the author analysed in three aspects,namely,the single-row piles and double-rows in the accumulation layer,the stress,deformation and failure laws of the piles,the three rows of piles which under the action of static and dynamic forces are based on the numerical simulation of the calculation formula and internal force calculation method of the landslide thrust after each row of piles.The main results are as follows:(1)The numerical simulation shows that There are similarities and differences between the stress difference(thrust)curve of miniature pile and the curve under static force by the influence of the seismic force.the single micro pile under dynamic action after the distribution of landslide thrust form a "triangle",three rows of tiny pile composite for "trapezoid" shaped sliding surface above,below the sliding surface as the "triangle",and the thrusting force distribution of pile under static form for the "triangle".(2)Under static and dynamic loading,the micro pile damage mainly shear fracture,bending moment,shear force,axial force are mainly concentrated near the sliding surface which have the most value,the back and bottom of pile body for static shear force,axial force under critical load increasing trend,after gradually become smaller,the front of the pile body shear(axial)value has been increasing;Under dynamic load,the peak acceleration of seismic wave of pile shear increases and increases,and the axial force is manifested as that the rear pile(middle row pile)increases before the critical load,while the middle row pile decreases with the increase of load.(3)The landslide thrust received by the micropile in the accumulation layer landslide,and it had a significant sharing effect.The ratio of the rear row to the front row of the double row pile combination under static force is 0.79: 0.21,and the rear row,middle row and three row pile combination The front row sharing ratio is 0.37: 0.35: 0.28;under the action of earthquake dynamics,the sharing coefficient of the back row,middle row and front row mini piles in the three rows of micro piles is 0.354: 0.348: 0.298.(4)Based on the quasi-static method and the physical-Okabe method to simplify the dynamic analysis,combined with the transfer coefficient method to obtain the single-row and three-row micropile pile post-thrust calculation formula,it is verified that the micropile is an elastic pile,based on the elastic pile Theoretically,the author based on the force analysis of the micro-pile embedding section and the load section is carried out to obtain the calculation method of the internal force of the pile body under earthquake action,and through a specific analysis of an engineering example,the calculation of the thrust value under natural conditions and earthquake action is completed.The design of the pile length and the calculation of the internal force of the pile body verify the rationality of the micro pile design method in this chapter.