Post-grouting Super-long Bored Pile In Lacustrine Sedimentary StratumBearing Mechanism Research

The super-long bored-cast-in-place piles are widely used in civil engineering and hydraulic engineering depending on their high bearing capacity,good seismic performance,flexible selection to pile length and diameter,meanwhile they can be buried in a large depth of the rock layer with a broader scope of application.However,the relevant research on the bearing mechanism of post-grouting super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers at home and abroad is still lagging behind the practical engineering applications.Therefore,this paper relies on the super-long bored-cast-in-place piles project of No.4 block of Kunming Dianchi International Exhibition Centre in Yunnan Province and is based on the engineering investigation and pile tests of the project,meanwhile employs indoor soil test to review,post-grouting super-long bored-cast-in-place piles in the engineering field to do the model test and the Midas GTS NX three-dimensional finite element numerical simulation to carry out the research of the bearing mechanism of post-grouting super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers.This paper aims at providing some references for revealing the design and construction of post-grouting super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers.The main research contents of this paper include:(1)Analysis of the pile mechanism and technology of post-grouting super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers;combined with the results of piles test for the super-long bored-cast-in-place piles project,analysis of the in-site static loading test on the super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers.(2)Research of the bearing mechanism of post-grouting super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers,and conduction of the model test of post-grouting super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers.(3)Research of numerical simulation of the bearing mechanism post-grouting super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers,depending on the super-long bored-cast-in-place project of No.4 block of Kunming Dianchi International Exhibition Centre in Yunnan Province and employing the Midas GTS NX three-dimensional finite element software.The results of this paper show that:(1)When the post-grouting super-long bored-cast-in-place piles are born,the lateral friction resistance and pile end resistance of the bored pile cannot be simultaneously exerted,and the lateral friction resistance is exerted before the pile end resistance.(2)When the post-grouting super-long bored-cast-in-place piles are born,the lateral friction resistance of the whole pile cannot be reflected at the same time.The soil around the pile top will firstly come out relative displacement to the pile,and the lateral friction resistance of the upper part of the pile top pile will be reflected first;the ultimate lateral friction resistance of the soil layer with different positions has a different relationship with the relative displacement of the pile soil.(3)The post-grouting technology has a better effect on pile settlement control for super-long bored-cast-in-place piles.The post-grouting technology can greatly reduce pile settlement and improve the ultimate bearing capacity limit.The main features of the paper are as follows:(1)Based on the static load test and modified Mohr-Coulomb model of the super-long bored-cast-in-place piles project,setting up the pile-soil Mohr-Coulomb interface,and conducting numerical simulation of the bearing capacity of post-grouting super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers by means of Midas GTS NX three-dimensional finite element software.(2)Carrying out the model test of post-grouting super-long bored-cast-in-place piles in site.Research of the lateral frictional resistance,the axial force and the pile end resistance on the basis of the experimental and finite element numerical simulations,and further research of the bearing mechanism of the super-long bored-cast-in-place piles in lake and marsh sedimentary soil layers.