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针对天然沉积软黏土中施工扰动导致原位土结构性损伤和强度降低的特征,根据圆孔扩张过程中产生的塑性剪切应变以及实测的渗透系数与不排水强度随径向距离的变化规律,提出对数式的原位扰动度函数以描述塑性损伤区的屈服强度变化;基于结构性剑桥模型屈服准则,采用屈服应力比和灵敏度分别表征初始结构稳定性和结构强度可变性大小,并与扰动函数相结合,推导了考虑土结构性损伤的软黏土柱孔扩张弹塑性解,表达式中灵敏度值为1时退化为不考虑结构损伤的传统解。进而通过竖井和沉桩施工引起的超静孔隙水实测结果与理论计算值的对比,验证了本文理论解的有效性;并分析了土结构及其损伤对柱孔扩张效应的影响,结果表明:屈服应力比越大,塑性区半径越小,径向应力越大,超静孔压随径向距离先增大后减小;灵敏度越大,径向应力越小,超静孔压越大。分析推导结果对准确预测挤土效应与合理揭示孔压静力触探等原位试验测试机理具有实用价值。
Aiming at the characteristics of structural damage and strength reduction of native soil caused by construction disturbances in natural sedimentary soft clay, according to the plastic shear strain and the variation law of measured permeability coefficient and undrained strength with radial distance in the process of circular hole expansion, Based on the yield criterion of structural Cambridge model, the yield stress ratio and sensitivity are used to characterize the initial structural stability and the variability of structural strength, respectively, and are compared with the perturbation function The elastic-plastic solution of the soft clay column hole considering soil structural damage is deduced. When the sensitivity value is 1, the expression degenerates into the traditional solution without considering the structural damage. The validity of theoretical solution of this paper is verified by the comparison between the measured results of the excessively static pore water and the theoretical calculated values caused by the construction of the shaft and the pile sinking. The effect of the soil structure and its damage on the expansion of the column holes is also analyzed. The larger the yield stress ratio is, the smaller the radius of plastic zone is and the larger the radial stress is. The excess pore pressure first increases and then decreases with the radial distance. The greater the sensitivity is, the smaller the radial stress is and the larger the excess pore pressure is. It is of practical value to analyze the inference results to accurately predict the squeezing effect of soil and to reveal the mechanism of in situ test of pore pressure static penetration.