Study On The Analytic Solution Of Foundation Settlement Of Semi-underground Building Under Loading And Unloading Grain Load

In recent years,with the increase of grain output in China,warehouse facilities have been developed rapidly.Many scholars have developed various new silo types,including underground silo and underground building silo etc,while the traditional Terzaghi one-dimensional seepage consolidation model cannot accurately reflect the foundation consolidation process under the operation of underground building silo facilities(mainly for loading and unloading grain).Therefore,it is necessary and urgent to carry out the settlement mechanism and mathematical model analysis of underground building storehouse under loading and unloading load.This paper is based on the the ministry of science and technology of the People's Republic of China's project "development of new type and technical system of ecological grain storage"(201413007),taking a semi-underground building silo construction project in haikou as an example,by means of ABAQUS numerical simulation,the settlement mechanism and analytical solution of storehouse foundation under loading and unloading load are studied.The specific research contents and conclusions have the following aspects:(1)By the generalized trapezoidal load Fourier series expansion,a subroutine is written with Maple--the computational software,the analytical expression of nonlinear one-dimensional consolidation under loading and unloading is established,the correctness of the analytical solution is verified by the one-dimensional consolidation solution of Terzaghi.Based on the analytical expression of one-dimensional nonlinear consolidation,the pore pressure dissipation curve of foundation soil under the cyclic load of rectangle,triangle and trapezoid is drawn.(2)Based on the law of volume change of foundation soil,darcy's law,water movement equation and balance equation,considering the influence of consolidation coefficient,large deformation and other factors on soil consolidation,on the basis of analytical expression of one-dimensional nonlinear consolidation,Fourier series expansion based on generalized trapezoidal load and with the help of Maple calculation software,the analytical expression of nonlinear three-dimensional consolidation is deduced.(3)Through comparative analysis of the results of triaxial consolidation test,three-dimensional consolidation analytic solution calculation,and Biot consolidation equation numerical calculation,it is found that the calculation curves of both solutions are above the test curve,and the three-dimensional analytical solution curve is closer to the test curve.It can be seen that the calculation formula of three-dimensional analytical solution is more accurate than the Biot consolidation equation for soil consolidation.(4)Based on the theoretical calculation,the finite element simulation software Abaqus is used to conduct numerical simulation calculation on the settlement and consolidation process of saturated soil in underground building storehouse foundation under different periods and under different action load forms(constant load,rectangle,trapezoid,triangle),and the simulation results show that:a.The action form of the maximum settlement load of underground building storehouse foundation is constant load,while the action form of the minimum settlement load is triangle load.b.After 50 years,consolidation degree under different loads: under constant load,soil consolidation reaches the maximum and is basically completed;Under the action of rectangular load,the degree of foundation consolidation reaches more than 80%;Under trapezoidal load,the degree of foundation consolidation reaches 80%;When the triangle load is applied,the degree of foundation consolidation reaches 60%.c.Combined with the field monitoring data and simulation results,it is found that the trapezoidal load action mode is more consistent with the settlement and consolidation of foundation soil under loading and unloading load.The paper further clarifies the evolution process of subgrade settlement of underground buildings under loading and unloading load,and the established analytical solutions of nonlinear one-dimensional and three-dimensional consolidation under generalized trapezoidal load have good applicability and high accuracy,and have strong reference significance.