黄土深基坑降水诱发的地基附加应力和沉降简化计算

Simplified calculation of foundation additional stress and settlement caused by precipitation of loess deep foundation pit

为预测黄土地区深基坑降水导致的地层不均匀沉降,确保坑周建筑物安全,基于弦线模量法、弹性半无限体理论和剪切位移法,将坑周土体以降水曲线为界分为疏干区和饱和区,综合考虑绕渗区内渗流力在水平方向的分量和桩-土界面侧摩阻力对土体的约束作用,推导降水引起地基附加应力和地面沉降的理论计算公式,将理论计算值与工程实际监测数据对比分析。研究结果表明:改进后的计算方法能反应出浸润曲线以下土层所受附加应力的衰减效应;地面沉降受侧摩阻力的约束作用主要局限于1倍的最大水位沉降范围内;弦线模量计算得到的沉降值精度高于规范算法,能够较好地预测黄土地区降水期间坑周地面沉降量。研究结果可为计算类似黄土深基坑潜水层降水诱发地面沉降提供参考。

In order to predict the uneven settlement of stratum caused by the precipitation of deep foundation pit in loess area,thus ensure the safety of the buildings around the pit,based on the chord modulus method,elastic semi-infinite element theory and shear displacement method,the soil around the pit was divided into the drained zone and the saturated zone by the precipitation curve.Comprehensively considering the component of seepage force in horizontal direction in the by-pass seepage zone and the constraint effect of lateral friction resistance located in soil-pile interface towards soil,the theoretical calculation formula of foundation additional stress and ground settlement caused by precipitation was deduced,and the theoretical calculation values were compared with the actual monitoring data of project.The results showed that the improved calculation method could reflect the attenuation effect of additional stress on soil layer under infiltration curve.The constraint effect of ground settlement by lateral friction resistance was mainly limited to the range of 1 times the maximum drawdown of water level.The accuracy of settlement value calculated by the chord modulus based on the structural parameters was much higher than that of the normative algorithm,which could better predict the amount of ground settlement around the pit during the precipitation period in loess area.