压入式沉井施工对环境影响的现场监测研究

结合工程实例，介绍软土中压入式沉井的施工技术并研究其对周边环境的影响。对沉井压沉过程中周边土体及管线的监测数据进行分析，结果表明：压沉施工能有效控制沉井的几何姿态，保持下沉速度稳定，但具有一定的挤土效应；沉井下沉初期挤土效应占主导地位，开挖效应随下沉深度的增加逐渐显著；土体水平位移和地表沉降均随沉井下沉深度H的增加而增大；地表沉降呈三角形分布，影响范围约为1.7H；土体分层沉降中，淤泥质粉质黏土的单位沉降量最大；管线沉降可控制在毫米级。基于对无量纲化地表沉降数据的拟合分析，提出了分别采用指数函数和二折线表示的压入式沉井周边地表沉降经验公式，并用工程实例验证了其合理性。

Field measurement and analysis of influence of jacked open caisson construction on environments

Based on the engineering case of a pipe-jacking working shaft sunk with the aid of caisson jacks in soft clay, the construction technology is presented and the effects on surrounding environment are studied. According to analysis of the soil mass and pipeline monitoring data during the jacked sinking process, some conclusions are drawn as follows. The jacked open caisson construction method can control the attitude of the open caisson and stabilize the sinking speed effectively; but it also squeezes the soil. At the preliminary stage of open caisson sinking, the compacting effect is significant and the excavation effect becomes more notable as the open caisson sinking deeper. The subsurface horizontal displacements and surface settlements grow along with the increase of the sinking depth H. The ground surface settlement profile is of spandrel type with an influence zone of 1.7H. Among layered settlements the unit settlement of the soft silty clay is the largest. The pipeline settlements are controlled in the millimeter level. Based on data fitting of the dimensionless surface settlements, an empirical method either in the form of exponential function or bilinear curve to predict the ground surface settlement caused by jacked open caisson construction is proposed, which is verified through two case studies.