Application Of PHC Pile Net Composite Foundatuon Flexible Structure In Bridge Head Roadbed Reinforcement Project

With the rapid development of highway construction,the settlement of soft soil foundation under complex geological conditions generally occurs,which seriously affects the safety and comfort of vehicle driving,increases the operating cost and maintenance of roads and structures,diminishes the service level of roads,and also damages the social and economic benefits of road construction seriously.In today’s highway construction,it has become an urgent problem to control the settlement of highway soft foundation.PHC pile-net composite foundation has the characteristics of small settlement,high bearing capacity,short construction period and so on.Which has been widely used in the treatment of soft soil foundation.In this paper,the settlement law and settlement calculation theory of PHC pile-net composite foundation on soft soil foundation of the bridgehead approach road were systematically studied by combining the settlement theory calculation with finite element numerical simulation analysis and field test.Based on the soil arching effect,cushion diaphragm effect,pile compaction effect,accelerated consolidation effect,anti-liquefaction effect,pile group effect and lateral restraint effect,the mechanism of flexible structure of PHC pile-net composite foundation and the theoretical calculation method of foundation settlement were summarized in detail.Combined with the engineering practice,the PHC pile-net composite foundation of the south section of the second route(Tonggang Road)in Huanghua Port Estuary was studied by field test.The surface settlement characteristics and settlement law of the composite foundation were analyzed systematically by the test results,which compared with the theoretical calculation results.For the purpose of controlling settlement,the optimal design of PHC pilenet composite foundation was carried out.The influence of the key factors such as pile length,pile diameter,pile spacing and composite cushion thickness on the settlement of PHC pile-net composite foundation under embankment load was studied by using the method of single factor variation.Which provided valuable reference for further study on the settlement of PHC pilenet composite foundation.