Research On Upper Bound Solution Of Ultimate Bearing Capacity Of Double-layer Foundation Based On Improved Radial Movement Algorithm

As one of the important research topics in the field of soil mechanics,the ultimate bearing capacity of foundations has attracted the attention of countless scholars for a long time.Usually,for the convenience of analysis,the traditional method assumes that the foundation is a singlelayer soil with uniform soil parameters.However,due to natural factors or artificial factors such as foundation treatment,we often use double-layer soil foundation in practical applications.The limit of this type of doublelayer foundation is The issue of carrying capacity has received more and more attention.For the bearing capacity of double-layer soil foundation,people mainly use various modified empirical formulas to calculate,and this paper uses the upper limit method of limit analysis,considering three different situations where the soil layer boundary is located,and establishes a new multi-rigid block failure mechanism by establishing a new multirigid block failure mechanism.to calculate the ultimate bearing capacity of double-layer foundations.At the same time,in some areas of our country,various engineering problems caused by earthquakes have gradually increased,so the research on the ultimate bearing capacity of double-layer foundations under earthquake loads also has certain value.At present,the research results that comprehensively consider the ultimate bearing capacity of double-layer foundations in view of the above factors are still relatively limited,and more in-depth research is needed.This paper focuses on the double-layer soil foundation,based on the upper limit method of limit analysis,and extends the improved radial movement algorithm(IRMO),a new global optimization algorithm,to the determination of the critical slip surface of the double-layer foundation and the calculation of the ultimate bearing capacity of the foundation.The main work The content is as follows:(1)Based on the upper limit method of limit analysis theory,a multi-rigid block translational bilateral failure mechanism of double-layer foundation is established,the physical parameters of each rigid block are calculated,and the maneuvering allowable velocity field considering the two possibilities of the relative motion directions of the rigid blocks is deduced,and the comprehensive calculation The internal force dissipation and external force work,and the upper limit solution formula of the ultimate bearing capacity of the double-layer foundation is obtained from the principle of virtual work.(2)Determine a reasonable objective function of the algorithm,build a mathematical model of the critical sliding surface of the double-layer foundation,apply the improved radial movement algorithm(IRMO)to the calculation of the upper limit solution of the ultimate bearing capacity of the double-layer foundation,and use the parameter matrix to participate in the search calculation of multiple sliding surfaces.The corresponding calculation program of ultimate bearing capacity under vertical load of double-layer foundation is compiled to achieve the purpose of accurately calculating the upper limit solution of ultimate bearing capacity and determining the critical sliding surface of foundation.(3)The calculation method in this paper is compared and analyzed with the IRMO algorithm’s example of the ultimate bearing capacity of the homogeneous foundation and the calculation formula of the homogeneous foundation of Terzag,and it is compared with the theoretical calculation method of the limit analysis upper limit solution method and the slip line method,and various empirical correction calculations.The method and the field test of the double-layer foundation bearing capacity are compared and analyzed,and the feasibility of the IRMO algorithm calculation is verified from multiple angles.Inferiority analysis was carried out to verify the stability and efficiency of the search results of the IRMO algorithm.(4)The influence of parameters such as internal friction angle,,cohesion,,upper soil layer thickness H and overload q in different soil layers of double-layer foundation was analyzed.The influence of the thickness of the upper soil and the overload on the bearing capacity of the foundation will also change under the condition of different soil parameters.The effect of each parameter on the ultimate bearing capacity of the doublelayer foundation is discussed.(5)The quasi-static method is used to consider the horizontal and vertical effects of the earthquake load,and the single-side failure mechanism of the double-layer foundation under the earthquake load and the mathematical model of the critical sliding surface of the double-layer foundation under the earthquake load are re-established,and the limit of the double-layer foundation under the earthquake load is deduced.The formula for the upper limit solution of bearing capacity is formulated,and the solution program for the ultimate bearing capacity of double-layer foundation under earthquake load is compiled according to the corresponding objective function.The change of the bearing capacity and bearing capacity coefficient of the foundation with the seismic force coefficient under the methods of different scholars is compared by using a classic example,and the parameter sensitivity analysis is carried out on the horizontal and vertical seismic force coefficients.Increasing the horizontal seismic force coefficient will significantly reduce the foundation.Bearing capacity,increasing the vertical seismic force coefficient will increase the bearing capacity of the foundation.