The mechanical properties and design-calculation methods of pile-net composite foundation were analyzed

with the condition of pile’s end into and not into the hard soil layer. A mathematical model for the optimal design of pile-net composite foundation was established by taking pile diameter

pile length

pile cap length

pile cap thickness and pile spacing as design variables. The foundation bearing capacity

settlement

tensile strength of reinforced geotextile

bending capacity and shearing capacity of pile cap were constraint conditions

and engineering cost was the objective function to be optimized. By introducing the perturbation weighting and reducing parasitic operations

the perturbation-weighted symbiotic organisms search (PWSOS) algorithm was proposed to increase the convergence speed and accuracy of the symbiotic organisms search algorithm. Based on the perturbation-weighted symbiotic organisms search

the global optimization of the mathematical model of the pile-net composite foundation was carried out

and the optimal reinforcement scheme that meet the requirements was the output. The results show that the optimal design scheme has better economic benefit and the perturbation-weighted symbiotic organisms search algorithm has better performance.