Research On Approximate Calculation Method And Engineering Application For Design Of Double-row Anti-slide Portal Piles

In the treatment of landslides,anti-slide piles have the advantages of simple structure,flexible layout and convenient construction,so they are widely used.However,in the treatment of large and super-large landslides,due to the large soil thickness of the landslide and the large thrust of the landslide,single-row anti-slide piles cannot meet the requirements of landslide treatment,and double-row and multi-row anti-slide piles have emerged as the times require.Portal double-row anti-slide piles are a kind of double-row anti-slide piles.It connects the front and rear rows of piles through the longitudinal connecting beams on the top of the piles and the transverse crown beams to form a space system to jointly resist the thrust of the soil landslide.It not only enhances the bending and shear resistance of the structure,but also improves the anti-sliding performance of the anti-slide pile.However,due to the complexity and difference of the soil around the pile,the interaction mechanism between the pile and the soil is not clear,resulting in the related design calculation theory is not yet perfect,which severely restricts its application in engineering.Considering this reason,based on the existing research,this paper derives the approximate analytical solution of the internal force and displacement of the portal double-row anti-slide piles based on the design and calculation theory of single-row anti-slide piles.In view of th e structural characteristics of portal double-row anti-slide piles,a simplified calculation model of structural force is established,that is,the portal double-row anti-slide piles are cut from the middle of the connecting beam,and the internal force of the cross-section is an unknown quantity,and the calculation is carried out according to the force method.The anti-slide pile is divided from the sliding surface into a loaded section and an anchored section.For soil landslides,the situation that the sliding surface is above the sliding surface is considered to be empty in front of the pile or the remaining anti-sliding force in front of the pile is not counted.The displacement differential equations of each characteristic section of the front and rear rows of piles are deduced by the foundation coefficient "m-K"method.The differential equation is solved with the boundary conditions of the pile bottom displacement,and the approximate analytical solution of the internal force and displacement of the portal double-row anti-slide pile is obtained.In order to verify the applicable scope and conditions of the approximate analytical solution of the internal force and displacement of the portal double-row anti-slide piles,a numerical analysis model of the portal double-row anti-slide pile was established,by using ABAQUS finite element software.Through analyzing the change law of soil stress,pile displacement and bending moment behind the front row of piles under different row spacing,approximate analytical solutions for pile internal forces and displacements are obtained,and the applicable row spacing range is 4-6 times the pile diameter.Taking the actual landslide project in Xiangxi area as an example,the internal force and displacement of the rectangular anti-slide pile on the main section are calculated by the analytical method and the finite element method,which derived in this paper.The comparison shows that the relative error of the two is about 11%,which indicates that the approximate analytical solution can be easily applied to actual engineering.