Model Test Of Pile-Soil Interaction In Expansive Soil

As a kind of clay with strong hydrophilicity,expansive soil is easy to expand and shrink under the influence of hydrometeorological conditions,which greatly threatens the safety of construction facilities in the expansive soil area.The application of pile foundation in expansive soil foundation can effectively reduce the impact of swelling and shrinkage deformation of expansive soil.It is difficult to quantitatively analyze the influence of clay content on expansive soil because of its special nature and complex mineral content.The above purpose can be achieved by preparing the mixture of similar materials of expansive soil with similar properties.In addition,the stress and deformation mechanism of pile expansive soil system are different from other pile-soil systems.Therefore,it has important application value and engineering guiding significance to study the pile-soil interaction in expansive soil similar material mixture and expansive soil foundation.In this paper,on the basis of extensive references at home and abroad,the following problems are studied by means of indoor basic physical and mechanical tests,model tests and ABAQUS finite element numerical simulation(1)Based on the basic mechanical tests in laboratory,the one-dimensional vertical expansion strain of sand-bentonite-gypsum model test mixture with different mass ratio was studied.The effects of gypsum content,bentonite content,moisture content and initial dry density on the swelling strain of the mixture were analyzed by the control variable method.By orthogonal test design,range result analysis and variance result verification,the primary and secondary relationship of the influence of each factor on the expansion strain rate of the mixture is determined,which is convenient to determine the best combination of each factor and horizontal expansion effect in the study of similar materials of expansive soil.It provides a reference for the preparation and study of similar materials with different expansibility.(2)Based on the research of similar material mixture of expansive soil,the appropriate proportion of expansive soil mixture is selected,and the model test of pile-soil interaction in expansive soil foundation is carried out.The loading pile and the non loading pile are designed in the experiment,and the bearing characteristics of the pile in the loading process are studied.After the completion of loading,the immersion test is carried out,and the displacement of pile-soil and the stress characteristics of pile body are analyzed.(3)Based on the model test,using ABAQUS finite element numerical simulation software,the appropriate pile-soil system model is selected to simulate the loading part of pile foundation in the model test.The Q-s curve of the pile,the axial force distribution of the pile and the characteristics of the side friction are analyzed.The results of numerical simulation are compared with the measured values of model test to verify the consistency ofthe basic laws of the two problems,and the reasons for the differences are given.Based on the consistency between the numerical simulation value and the test value,the ultimate bearing capacity of the unfinished pile foundation in the model test is simulated.According to the Q-s curve,the ultimate bearing capacity of the test model pile is given according to the pile foundation test specification.By changing the Q-s curves of pile length and pile diameter under the action of load,it is found that the pile length and pile diameter can improve the bearing capacity of pile foundation,but the economy and rationality should be considered.