Research On The Bearing Performance Of Large-diameter Rock-socketed Cast-in-place Piles In Mudstone Foundations

The rock socketed pile whose pile end is embedded in basic rock mass and combined with the peripile rock mass to form a force whole,and the bearing capacity is greatly improved on the base of end bearing pile.Large diameter rock-socketed cast-in-place pile has the advantages of larger bearing capacity,better seismic performance,smaller settlement,less pile group effect,better adaptability to various strata and rapid construction.As a kind of soft rock,mudstone not only has low strength,but also has the characteristics of water immersion and disintegration.Mudstone is widely distributed in Guizhou area.With the rapid development of economy and society in China,the foundations of many high-rise buildings,especially large diameter cast-in-place piles,need to be placed in mudstone foundation,which has certain requirements for the bearing capacity of mudstone foundation.The main contents of this paper are as follows:This paper introduces and discusses the definition of rock-socketed pile,compares the mechanical characteristics of non-rock-socketed pile and rock-socketed pile,analyzes and discusses the similarities and differences between them,and gives a brief introduction to mudstone.The failure mode and stress characteristics of rock-socketed pile are introduced,and the load transfer mechanism of non-rock-socketed pile and rock-socketed pile under vertical load is discussed and compared.The working mechanism of side resistance and tip resistance of rock-socketed pile and the main factors affecting its exertion are analyzed.Based on the self-balance method,the in-situ test of large-diameter rock-socketed pile in mudstone foundation was carried out and the load transfer characteristics of pressed pile,uplift pile and self-balanced pile were analyzed and compared.Combined with the in-situ test results,the settlement of large diameter rock-socketed pile in mudstone foundation was calculated and analyzed.Based on the field test,the finite element software is used to establish the analysis and calculation model,and the numerical analysis of the large diameterrock-socketed pile in the mudstone foundation is carried out.The bearing characteristics of pile foundation under different working conditions without and without external load and the influence of pile diameter and rock-socketed depth on the bearing capacity of pile foundation are analyzed and compared.Through orthogonal test and grey correlation analysis,the pile diameter,the concrete strength of pile body,the angle of rock friction of bearing layer,the cohesion of rock,the compressive strength of rock in bearing layer,the pile diameter,the concrete strength of pile body,the cohesion of rock in bearing layer,and the compressive strength of rock in bearing layer of mudstone foundation are studied respectively.Sensitivity analysis of 6 independent factors,such as the depth of bearing bed,is carried out.Whether through the range analysis,variance analysis,or grey correlation analysis of the orthogonal test,the sensitivity order of influencing factors of bearing capacity of large diameter rock-socketed pile in mudstone foundation is as follows: depth of bearing bed rock socketed > pile diameter > compressive strength of bearing layer rock.Bearing capacity of large diameter rock-socketed pile on mudstone foundation by variation of bearing bed depth Influence is most sensitive.It can provide reference for the engineering design and practice of large diameter rock-socketed pile similar to mudstone foundation in Guizhou Province.