Study On The Subgrade Diseases In Permafrost Of Qinghai-tibet

The study of ultimate bearing capacity of buildings or structures mainly includes two aspects: one is the strength and stability problem;the other is the deformation problem.Therefore,in order to ensure the safety of the superstructure of the building and the normal use function,in the foundation design,the foundation not only to meet the upper building through the foundation of the foundation soil pressure shall not exceed the allowable value of the bearing capacity of the foundation,and require deformation Should be within the allowable range.Due to the simple construction of the square foundation,the bearing capacity is high,the stability is good,the settlement is small and uniform.Therefore,in the current application is very broad,widely used in railway bridges,highway bridges,rail transportation,building structures and waterway.The foundation bearing capacity of the shallow foundation belongs to the three-dimensional space problem.In the past,the scholars used the simplified method to study the square foundation,and regarded it as the basis of the two-dimensional bar,multiplied by the correction coefficient before the obtained bearing capacity coefficient,Linear superposition of the way to get the ultimate bearing capacity of the theoretical calculation formula,in this regard to contribute to the Prandtl,too sand base Vesic and other scholars.Because the formula is linearly superimposed and ignores the lateral earth pressure of the soil,the theoretical value of the final solution is caused by some error.In this paper,by using the upper limit method in the limit analysis theorem,the square foundation is regarded as the three-dimensional model,and the velocity displacement field of the maneuver permit is established.Considering the influence of the lateral earth pressure,the ground overload and the soil weight,For the active,transition and passive three zones,the power and internal energy dissipation of each zone are calculated respectively.Finally,the upper limit solution of the ultimate bearing capacity of the foundation is deduced by virtual work principle.The three bearing capacity coefficients N_r,N_C,and N_q in the formula of bearing capacity of sandfoundation are compared with the coefficients of several predecessors,which proves the rationality and applicability of the upper limit solution.In this paper,the large-scale general finite element software ANSYS is used tosimulate the bearing capacity of foundation.The numerical simulation results are compared with those of Li Wei's theory.The results of this paper are compared with K₀= 0 and K₀? 0,Applicability of Simulation to Analysis of Bearing Capacity ofFoundation.