考虑无井阻和土体非线性的真空-堆载联合预压复合地基固结分析

Consolidation Analysis of Vacuum-surcharge Preloading Composite Foundation Considering Nonlinearity of Soil and no Well Resistance

针对真空-堆载联合预压复合地基固结问题,考虑土体的非线性,通过引入对数模型,给出真空-堆载联合预压复合地基非线性固结问题的解析解。运用算例分析讨论了复合地基固结性状的变化规律。结果表明,真空-堆载联合预压复合地基非线性固结问题可看作是真空荷载和堆载两者叠加的效果,其按应力定义的固结度与按变形定义的固结度不同;按应力定义的固结度,当土体压缩指数与渗透指数之比小于1时,增大真空荷载值或堆载值,固结加快,当其大于1时,情况则相反;土体压缩指数与渗透指数之比、井径比、涂抹区大小越大,桩土模量比越小,固结越慢;在时间因子较小时,扰动区土体超静孔压增长速度明显大于未扰动区;距离桩体越远,超静孔压消散越慢。

Aiming at the consolidation problem of vacuum-surcharge preloading composite foundation,considering the nonlinearity of soil,a logarithmic model was introduced.Then,the analytical solution of the nonlinear consolidation problem of vacuum-surcharge preloading composite foundation was given.The variation law of consolidation behavior of composite foundation was discussed by numerical example analysis.The results show that the non-linear consolidation problem of vacuum-surcharge preloading composite foundation can be regarded as the superposition effect of vacuum load and surcharge.The consolidation degree defined by stress is different from that defined by deformation.According to the degree of consolidation defined by stress,when ratio of compression index to permeability index of soil is less than 1,the value of vacuum load or heap load is increased,and the consolidation is accelerated.When ratio of compression index to permeability index of soil is greater than 1,the situation is opposite.The greater the values of ratio of compression index to permeability index of soil,to pile diameter,and to the disturbance area are,the smaller the pile-soil modulus ratio is,and the slower the consolidation is.When the time factor is small,the growth rate of excess pore pressure in disturbed zone is obviously larger than that in undisturbed zone.The farther away from the pile is,the slower dissipation of the excess pore pressure is.