Intelligent Optimization Design Method For Pile-net Composite Foundation

In recent years,with the rapid development of traffic construction in China,the treatment of soft soil foundation has become increasingly prominent,which is mainly manifested as the insufficient bearing capacity of foundation,long deformation and stability time,and large settlement.Pile-net composite foundation has low settlement and high stability,which can be economically and effectively treated soft soil foundation.Supported by the national natural science foundation of China(51278186)and the national key research and development program(2016YFC0800203),this paper optimized the design of pile-net composite foundation.The main work and results are as follows:(1)A new meta-heuristic algorithm-Symbiotic Organisms Search(SOS)algorithm was introduced,and a weighted perturbation strategy and less parasitic operations were introduced to improve the algorithm,so as to construct a new symbiotic biological search algorithm,namely the Perturbation-Weighted Symbiotic Organisms Search(PWSOS)algorithm.(2)An optimal design method of pile-net composite foundation based on the Perturbation-Weighted Symbiotic Organisms Search(PWSOS)algorithm.The stress and deformation characteristics of pile-net composite foundation are analyzed when the pile is not driven into hard soil and when the pile is driven into hard soil.A mathematical model for optimal design of pile-net composite foundation is established with pile diameter,pile length,length and thickness of pile cap and pile spacing as design variables,foundation bearing capacity,settlement,tensile strength of reinforced body,bending and shear resistance of pile cap as constraints,and engineering cost as objective function.Based on PWSOS algorithm,the mathematical model of optimal design is optimized globally,and the optimal design scheme of pile-net composite foundation is obtained.(3)The agent model of Kriging settlement is introduced to establish the optimal design model and calculation method of pile-net composite foundation.The settlement agent model of pile-net composite foundation is established based on Kriging model,and the calculation results and finite element analysis results of the settlement agent model are compared to verify its reliability.Based on the Kriging settlement agent model,a mathematical model for optimal design of pile-net composite foundation is established with engineering cost as the objective function and foundation settlement and bearing capacity as constraints.PWSOS algorithm is used to optimize the model globally,and an economic and effective reinforcement scheme is obtained.(4)The effects of soil filling height,compressive modulus,pile lateral friction and pile tip resistance on pile-net composite foundation are analyzed.Through comprehensive tests,the composite foundation of pile net in deep soft soil area with different filling height,compression modulus,undrained shear strength and pile spacing is designed,and the rule of pile length changing with undrained shear strength of pile net composite foundation is obtained.The design chart of pile net composite foundation in deep soft soil area with different parameters is given.