Mechanism of Rigid Pile Composite Foundation Influenced by Marine Soft Soil

Rigid pile composite foundation is greatly influenced by soft marine clay.But it is neglected by many engineers due to the unclear influence mechanism,which causes serious engineering accidents.Based on the comprehensive analysis and research results of typical construction examples in recent years,the characteristics of consolidation settlement,structure and low-permeability of marine soft soil and the mechanism of rigid pile composite foundation influenced by the soft marine clay were researched.In combined with computational analysis of several construction examples and its field test data,the rationality of research conclusions is verified.The results prove that rigid pile composite foundation should not be directly used in marine soft soil.It is necessary to fully consider the influence of consolidation settlement,high sensitivity,compacting disturbance,and clear treatment effect after the field test construction.There are two different failure mode of composite foundation caused by consolidation settlement due to the different bearing stratum of the pile tips.If pile tips are suspended on the soft soil layer,it causes significant penetrating deformation of pile tips and plastic deformation of the soft soils among piles;if pile tips are embed into the harder soil layer,pile bodies would firstly be destroyed by strength failure and then soft soils among piles would be destroyed.The settlement soils of composite foundation do not converge for a long time and even accelerate subsidence in macroscopically.Because of the disturbance of construction,the marine soft soil pushed by foundation piles could be regarded as fluid.According to the property that the fluid always flows to the path with the least resistance,there are three different soil discharge paths: soil discharge upward along the plastic zone at the pile side,soil discharge upward along the whole site,and soil discharge laterally along the weak area around the site.Since the bearing capacity of marine soft soil foundation between piles is very low,sufficient soil arch height should be ensured under the action of upper load.Finally,the countermeasures and suggestions in the engineering practice of rigid pile composite foundation in marine soft soil area are proposed.