DEM Analyze On The Bearing Capacity Of Anisotropy Sandy Foundation Study

Sandy is a common foundation bed material.With the increasing of super engineering,such as high buildings,large hydropower stations,et.,the research of sandy foundation bed becomes more and more important.In nature state,the cohesion among sandy particles is very small or even not exists,and the shape of sandy particles is irregular.However,the anisotropy of sandy appears outstanding during the period of sedimentation,and then effect the mechanical property of sandy foundation bed.Therefore,study the sandy foundation bed's evolution law of force chains and the law of bearing capacity in different direction has great significance to offer the theory support for the construction of super engineering.This study was divided into three steps.Firstly,the evolution law of inner force chains in anisotropy sandy foundation bed was studied through a photoelastic experiment in laboratory.Moreover,the law of bearing capacity of sandy foundation bed with the different size of foundations was also studied.Secondly,analyze the evolution law of microcosmic force chains under the isotropy condition and different degree of anisotropy condition through the method of numerical simulation(PFC2D).Finally,a coefficient in Terzaghi K.theory was modified based on the results of the distinct element analysis.In conclusion,some achievements could be obtained:(1)The rang of force chains among photoelastic particles was increase with the increasing of foundation's size.The more big foundation size,the more weak force chains and the smaller settlement displacement under the same load.In practical,the bigger foundation size,the more stability to engineering.(2)With the increasing of load,the number of force chains was more and more and the strength was more and more big.The different arrange styles of photoelastic particles would lead to the big diversity of foundation bed in different directions.The settlement displacement under different arrange styles of photoelastic particles were all obeyed the same regular that the size of foundation more big the settlement displacement more small.(3)From the evolution law of force chains and the regular of load-displacement under the condition of different foundation sizes and arrange styles of photoelastic particles,it could be found the compressive deformation of photoelastic particles was primary effected by foundation size,the arrange style of photoelastic particles and the load.(4)The results of numerical simulation could be showed the foundation bed presented brittle failure under the condition of particles horizontal arrangement.The load-displacement curve obtained by numerical simulation was similar to the curve of loose sandy foundation bed under the condition of particles slant arrangement.Under the condition of particles vertical arrangement,the load-displacement curve was like to the curve of dense sandy foundation bed.The value of bear capacity and the types of particles arrangement could be described as: slant arrangement> vertical intersection arrangement> horizontal arrangement> vertical arrangement> horizontal intersection arrangement> random arrangement.(5)By comparing the ultimate bearing capacity obtained by load test and Terzaghi K.theory,it was found the variation tendency of ultimate bearing capacity with direction angel of particles was same,both them were increase firstly and then decrease.Compared with load test,the ultimate bearing capacity calculated by Terzaghi K.theory had a degree of deviation.Through fitting the internal friction angle and the direction angel of particles,deduce a formula which used the direction angel of particles to calculate the ultimate bearing capacity of sandy foundation by modifying the Terzaghi K.theory.