软土地区浅埋矩形顶管施工地表变形与数值模拟研究

Study on surface deformation and numerical simulationof shallow buried rectangular pipe jacking in soft soil area

浅埋矩形顶管在软土地区施工过程中常伴随着较大的地表变形,借助有限元数值模拟分析和现场实时监测手段,研究了矩形顶管施工期间地表变形演化规律,重点探讨了地层损失、掌子面压力及管土摩阻力等因素对地面扰动的影响。结果表明,土体采用修正剑桥本构模型或Drucker-Prager本构模型所计算结果更合理。土体采用Drucker-Prager本构模型下的计算结果与实测结果对比,两者拟合程度较好,数值模拟能够较好地反映实际施工过程中的地表变形。掌子面压力和管土摩阻力过大是造成地表隆起的重要原因,软土浅埋顶管施工中掌子面压力宜取1.2倍理论计算值,同时应采取有效的减摩措施。地表沉降主要集中在顶管正上方,显著影响范围为中轴线两侧各2倍顶管宽度。

It is often accompanied by large surface deformation in the construction process of shallow buried rectangular pipe jacking in soft soil area.Therefore,the means of finite element numerical simulation analysis and field real-time monitoring are used to research the evolution law of surface deformation during rectangular pipe jacking construction.The effects of formation loss,face pressure and pipe soil friction on surface disturbance is emphatically discussed.The results show that the modified Cam-Clay model or Drucker-Prager constitutive model is more reasonable for soil mass.The calculated results of the Drucker-Prager constitutive model are compared with the measured results,and the results are in good agreement with each other.The numerical simulation can well reflect the surface deformation in the actual construction process.The high pressure of the face pressure and the high pipe soil friction are the important reasons for the surface uplift.In the construction of shallow buried pipe jacking in soft soil,the face pressure should be 1.2 times of the theoretical calculation value.Meanwhile,effective measures should be taken to reduce friction.The surface settlement is mainly concentrated above the pipe jacking,and the significant influence range is 2 times of the pipe jacking width on both sides of the central axis.