The Research On The Influence Of Karst Cave In Front Of Pile On The Horizontal Bearing Characteristics Of Pile Embedded Segment

Karst areas are widely distributed.There are large carbonate strata in China,accounting for 1/3 of the country's total land area.When the horizontal bearing pile(such as anti-slide pile,support pile,etc.)is applied in karst area,the irregular karst cave on the side of the pile will seriously affect the bearing characteristics of the pile.Anti-slide pile before choosing pile with caves exist in this paper as the research object,using numerical analysis method research when there is a cave before pile to pile embedded segment of the influence of the horizontal load-bearing characteristics.According to different deformation characteristics of anti-slide pile,the anti-slide pile in karst area is divided into rigid pile and elastic pile,and the finite element calculation model of two different forms of anti-slide pile is built respectively,and the influence of different roof thickness,high span ratio and distance between the karst pile and pile edge on the horizontal bearing characteristics of the pile embedded segment is analyzed.The following conclusions are drawn: under the uniformly distributed load,the roof of the karst cave in front of the pile is damaged by compression and shear,which leads tothe decrease of the horizontal ultimate bearing capacity of the pile.When the thickness of the roof of the karst cave increases,the distance between the karst cave and the pile edge increases or the ratio of high span decreases,the influence of the karst cave on the pile embedded segment decreases gradually,and the horizontal bearing capacity of the embedded segment increases gradually.Encountered in the project before the pile exist water-eroded cave and the site does not have enough space to far away from the cave,often increase the diameter and depth of the built-in is used to increase the horizontal bearing capacity.In this paper,two kinds of cave-size models that are easy to be destroyed are selected to analyze the situation.The conclusion is as follows:when the long axis of the cave-length is the Y-axis,the increase of pile embedding depth can increase the horizontal bearing capacity the most,followed by the pile diameter.When the long axis of karst cave is X-axis,increasing pile diameter has the greatest influence on the horizontal bearing capacity,followed by the depth of pile embedding.Finally,the optimal plan of horizontal bearing capacity of the fixed section of the lifting pile is selected by checking the numerical analysis results through an engineering example.The research results provide basic technical basis and ideas for solving the problem of lifting the horizontal bearing capacity of pile embedded section when there is a karst cave in front of the pile in karst area.