桩筏复合地基负摩阻段分析及桩土应力比计算

Analysis on Negative Friction Segment of Pile-raft Composite Foundation and Calculation of Its Pile-soil Stress Ratio

通过对桩筏复合地基桩顶负摩阻段桩-土相互作用分析,得到桩顶负摩阻段桩间土中附加应力计算方法。在此基础上,利用弹簧组模型对桩筏复合地基桩-土-垫层相互作用进行分析,得出桩顶处桩和桩间土竖向有效应力及桩顶刺入变形计算方法。分析垫层对应力调节、沉降控制的影响。结果表明:在桩与桩间土间摩擦力作用下,桩间土竖向有效应力随深度增加衰减,并在某一深度衰减到较小水平,可不考虑该位置以下桩土相互作用对桩顶处桩土应力比的影响。垫层模量对桩顶处桩、土应力调节起重要作用,并对桩顶上刺量影响显著。垫层模量越小刺入量越大,且随模量减小刺入量增长速度加快。

The calculating method of the additional stresses in the inter-pile soil in the pile-top negative-friction segment of pile-raft composite foundation is obtained by analyzing the interaction of pile soil in the negative friction segment at the top of the pile.On this basis,the pile-soil-cushion interaction of the composite pile-raft foundation is simulated with the spring-set model,the calculating method of the vertical effective stresses of the pile and inter-pile soil on the pile-top plane and the penetration distance from the pile-top is created.The influence of cushion on stress regulation and settlement control is analyzed.The research results show as follows： Under the action of the friction between the pile and inter-pile soil,the vertical effective stress of inter-pile soil decays with depth and to a low level at a certain depth below which the influence of pile-soil interaction on the pile-soil stress ratio at the pile top can be neglected;the modulus of the cushion plays an important role in pile-soil stress adjustment at the pile top and exerts obvious influence on the penetration amount at the pile top;the smaller the modulus of cushion,the more the penetration amount,and the penetration amount growth accelerates along with decreasing of the modulus of cushion.