Concrete core sand pile is a new kind of pile used to process soft soil foundation,and it is widely used in practical engineering.Compared with other piles,the pile effectively reduces the differential settlement of composite foundation.At the same time,the concrete core sand and gravel piles can increase the frictional resistance between the pile sides and make the deeper depth of load transmission,which plays a good role in the reinforcement of deep soft soil foundations.In this paper,analytical methods and numerical simulation methods are used to study the consolidation of concrete core sand-gravel pile composite foundation under vacuum preloading conditions.The main research work is as follows:(1)In order to solve the problem of consolidation of composite cores with inhomogeneous distribution of initial core pores under vacuum under vacuum preloading conditions,a vertical flow in annular sand and gravel piles was considered and the initial pore pressure was distributed along the depth.Based on the knot model,the analytical solution of the consolidation of the concrete core sand-gravel pile composite foundation was deduced.Finally,the degeneracy studies and case studies of understanding were performed to verify the rationality of the solution.(2)Under the vacuum combined surcharge preload conditions,taking into ac count the vacuum-induced initial pore pressure along the depth change is a functio n of depth;at the same time,considering the additional stress caused by the surch arge is also a function of depth,given the vacuum combined surcharge Analytical solution of the consolidation degree of composite core sand-stone pile composite foundation under pre-compression,the influence of factors such as the penetration of pile,the compressive modulus and permeability of pile and soil on the degree of consolidation.(3)The finite element software simulation analysis of the three-dimensional sand drainage consolidation model and Terzaghi one-dimensional consolidation mod el,and the theoretical calculation results are in good agreement with each other,i ndicating the rationality of the finite element software modeling and the theoretical solution of this paper Correctness.(4)A two-dimensional finite element calculation model was established in th e finite element software.The consolidation process of the composite core of conc rete core and gravel pile under two different conditions of vacuum preloading and vacuum combined with preloading was simulated.The graph of the relationship b etween the degree of consolidation and the change of time in the case is compare d with the deduced analytical solution. |