Optimization Design Method Of Composite Foundations Based On Settlements’ Surrogate Models

The optimization designs of the structure forms and design parameters which met the engineering safety,reliability and economy was a goal for engineer.However,when optimizing the complex composite foundations,it is difficult to establish a mathematical model for optimization design with clear expressions because of the lacking of clear formulas for settlements.The amount of computation will be too huge if the optimization models are established only by numerical simulatioin.So,an optimization design method of surrogate models of composite foundation settlements has been introduced with the support of National Natural Science Foundation(51278186)and National Key R&D Plan(2016Y-FC0800203),and several composite foundations with different geological conditions and forms were optimized by using this kind of optimization design method.The main works and results of this paper were as follows.(1)The optimization design of the cement mixing pile composite foundations in shore.Firstly,to establish the three dimension finite element models of the composite foundations and calculate the settlements and differential settlements of the composite foundations,many numerical experimentations are designed based on uniform design.Secondly,establish the surrogate models of the composite foundations based on the least squares support vector machine.Thirdly,establish the mathematical models of the composite foundations for optimization designs by considering the costs of the composite foundations as the object functions and the settlements as the constraints.Finally,search for the most economic strengthening scheme based on the genetic algorithms and export this scheme which satisfies the allowable settlements.(2)The optimization design of the cement mixing pile composite foundations in the deep-thick soft clay area.On the basis of orthogonal tests design,an optimization design method of soil-cement columns supported composite foundation was proposed based on the response surface methodology.Firstly,the schemes of numerical tests were designed based on the orthogonal tests design.Secondly,settlements of the composite foundations were calculated by using the finite element analysis,and the settlement’s surrogate models of composite foundations were established by response surface methodology.Then,the mathematical model of optimization design was established with the settlements of the composite foundations as controlled conditions and the engineering costs as the object functions.Finally,the global optimal of the mathematical models was searched out by the particle swarm optimization,and the most economical stabilizing layout of cement mixing pile composite foundation in the deep-thick soft clay area was exported.(3)The optimization design of the long-short-pile composite foundations.Firstly,design the multi-factorial uniform tests by considering the length of long piles and short piles,cement ratio and pile spacing as experimental factors.Secondly,on the basis of the test scheme,calculat the settlements and differential settlements of the long-short-pile composite foundations under the embankment loading based on finite element method,establish the radial basis function(RBF)surrogate models of composite foundations settlements.Then,establish the object function of the composite foudations optimization design,and search out the optimal solution by ant colony algorithm(ACA).Finally,export this optimal laout of reinforcement.