水泥土桩复合土钉支护的失稳破坏及稳定性验算

土钉支护的特点是随挖随支，其锚固体强度随时间逐渐提高，在继续开挖过程中，基坑临空高度持续加大，使基坑边壁发生相应侧移变形，土钉开始发挥作用，因此其对施工开挖速度有较为严格的限制。水泥土桩复合土钉在施工过程中，由于水泥土桩强度和刚度的预先形成，限制了开挖施工阶段的失稳破坏，并使基坑边壁的直立开挖高度相应提高，在继续开挖和土钉施工过程中基坑边壁的侧移特征、土钉应力的分布特征均发生变化，因此水泥土桩复合土钉支护结构的失稳破坏及设计计算模式相应发生变化。本文基于水泥土桩的强度和刚度对土钉支护结构的影响，分析研究了水泥土桩复合土钉的失稳破坏特征，及稳定性验算要求，为建立水泥土桩复合土钉的设计计算理论奠定基础。

Unstable failures and stability computations for composite retaining of cement-soil pile and soil nailing (CRCSPSN)

Foundation excavation immediately followed by retaining is the character of soil nailing. The anchor strength increases gradually with time passing by, and then during subsequent excavation, soil nails begin to play its role with the displacements of pit side, which are caused by the increasing height of it. So excavation speed must be strictly controlled. Unstable failures are restricted and upright unretaining excavation height is heightened during the construction of CRCSPSN for the strength and stiffness of cement-soil pile coming into being in advance, and during continual excavation and construction of soil nailing, the characteristics of displacements of pit side and the distributing of soil nail stress are all changed. So the calculation and unstable failure analysis modes are all changed correspondingly. In this paper, based on the influence of the strength and stiffness of cement-soil pile to soil nailing, unstable failure patterns and requirements for stability computations are analyzed and studied, which establishes the basis for design of CRCSPSN.