New Method For Calculating Pile-soil Stress Ratio Of Gravel Pile Composite Foundation

Pile-soil stress ratio of gravel pile composite foundation is an important design parameter,which reflects the stress sharing of pile and soil on composite foundation.Because of the interaction between pile and soil is extremely complex in the gravel pile composite foundation,it is hard to get an accurate value of pile-soil stress ratio.In the "Technical Code for Ground Treatment of Buildings",it is suggested that the pile-soil stress ratio of the gravel pile composite foundation should be in the range of 2 to 4.According to previous research,the span of this value is too large,which is likely to cause greater error;the current research has mainly focuses on the limit conditions of the gravel pile composite foundation.However,in practical engineering,the gravel pile composite foundation often fails to reach this state,so the theoretical calculation of the pile soil stress ratio will be smaller than that in the actual project,which will easily deviate from engineering design.In view of the above problems,this paper will be based on the normal working condition of gravel pile composite foundation,conducting the research of the pile-soil stress ratio in the following three aspects.(1)From the perspective of the theory analysis,this paper is based on the summary of previous studies,according to the vertical deformation of gravel pile composite foundation under rigid foundation are equal and the radial deformation is coordinated,considering the influence of the vertical load and depth on the pile deformation modulus,the expression of deformation modulus of pile under different vertical loads and depths is derived,then the theoretical calculation method of the pile-soil stress ratio of the normal working condition is obtainedand,according to the parameter analysis of this method,the conclusion is consistent with the measured result.At the same time,the formula for calculating the deformation modulus of pile is applied to calculate the settlement of foundation by the method of composite modulus.(2)The composite foundation of gravel pile is simulated by the finite element method.Assuming that the pile material is the soil hardening model,the modified mohr-coulomb constitutive model in Midas GTS software is used to simulate the model.The results of the analysis are in good agreement with the proposed method in this paper.In addition,using the Midas GTS software to analyze the additional stress in the substratum under the different parameters of the gravel pile composite foundation under different parameters,and the pressure diffusion angle β in the reinforced zone of the gravel pile composite foundation is obtained.(3)Compare the measured data of three engineering cases with the calculated results of the proposed method,the feasibility and practicability of this method are verified.