Study On Bearing Behavior And Rock-socketed Depth Of Rotary Drilling Piles

In recent years,rotary drilling pile foundation has been an important choice of electric power,industrial and civil buildings,railway and highway etc because of its advantages of high degree of automation,multi-purpose machine,flexibility,high construction efficiency,low environmental pollution and high adaptability to the formation.In order to ensure the structure to withstand all kinds of geological disasters and natural disaster,feasible and reliable rotary drilling pile design and construction technique is an important issue to be resolved.At present,the key technology of the design of the pile is the bearing capacity and settlement calculation of single pile,and the key technology of construction is to control the depth of rock socketed accurately on the premise of safety.The process of traditional design,usually considers pile-soil displacement coordination and ignores shear slip effect caused by the interface between pile and soil.In the construction process,the determination of rock socketed depth is based on the experience of construction technicians according to design drawings.Therefore,for both the design and the construction,the judgements on the base of simplified design analysis theory and empirical support have caused the potential adverse effects on the safety and economy of projects.In order to identify the formation information in the construction process accurately,this paper uses the ratio of the real-time working parameters of the rotary drilling rig to establish the formation information to monitor the rock socketed depth.Based on the finite element software DIANA,the behavior of a single pile under vertical load is studied by setting the pile-soil contact element.The main research contents are as follows:(1)In this paper,the development status of pile soil contact theory and rock socketed depth at home and abroad are analyzed in detail,and the key problems in the design and construction monitoring of pile foundation are summarized.(2)The results of different finite element software in simulating pile-soil interaction are compared and the influence of different parameters on the pile-soil contact surface on the pile-soil interaction are studied.(3)By using the finite element software DIANA,the pile-soil contact model is established and the variation laws of pile top settlement under different key parameters are analyzed in detail to verify the feasibility and rationality of the numerical simulation method.(4)Through the real-time monitoring of rotary drilling rig,the basic parameter is converted into the derived parameters,establishing work ratio model,and using SPSS optimize work ratio threshold for work ratio interval of different layers under the hedge of 95%.The results will support the real-time monitoring of rock socketed depth of rotary pile construction.(5)The mechanical properties of rotary drilling pile and soil are researched based on DIANA.And through comparative analysis of the optimal socketed depth determined by the numerical simulation method and real-time monitoring of work ratio,the accuracy of this method is verify.The innovations of this paper are as follows: using the finite element software DIANA to establish the three-dimensional model of the contact between the pile and soil,take the settlement of the rotary drilling pile top under different factors as the index to study the mechanism of the rock socketed depth.This paper presents work ratio method of real time monitoring and identifying strata of rotary drilling rig to determine rock socketed depth as the support of numerical simulation analysis method.