复合土钉墙变形的简化计算方法

CALCULATION MODEL OF SOIL PRESSURE DISPLACEMENT BASED ON MINDLIN SOLUTION

  • 摘要: 复合土钉墙的侧向变形计算是其设计的关键指标,目前规范还没有相应的计算方法。该文假定复合土钉墙的最终侧向变形为部分土压力作用下微型桩的变形与土钉本身在其影响范围内土压力拉拔变形的叠加,把前者等效为一个多跨简支梁变形,建立了利用土钉和微型桩的水平刚度的大小来分配相应位置的微型桩所受到的侧向土压力的计算模型;推导了土钉的水平刚度系数的计算公式,研究表明土钉的水平刚度系数主要受到相应位置钉土间的剪切变形系数和潜在滑动面以外土钉长度L1的影响;提出了按照悬臂梁或水平受荷桩计算微型桩的水平刚度系数的方法;讨论了该文提出的复合土钉变形计算方法中主要参数的计算模式,包括土压力、钉土间剪切变形系数等。通过工程的实测资料对该文计算理论进行验证,结果表明了该文复合土钉墙变形计算简化方法的有效性。该文所提出的复合土钉墙变形计算方法可以利用工程实践中大量的土钉抗拔实测资料,比较容易地推算复合土钉墙开挖后的变形情况,从而为复合土钉墙变形的预测和控制提供了设计和施工方面的依据和参考。

     

    Abstract: The lateral displacement of composite soil nailing is a key parameter for design, but the calculation method is not specified in the code. This paper adopts the assumption that the final lateral displacement of the composite soil nailing wall is the sum of the micro-pile deformation under partial soil pressure and the pull-out deformation of soil nail in its effective range, and the former is equivalent to that of a multi-span beam under partial soil pressure. Then the calculation model of the lateral soil pressure applied to the micro-pile is proposed by the magnitudes of the horizontal stiffness of the soil nail and the micro-pile. The formula of horizontal stiffness coefficient of soil nailing is derived, which is mainly affected by the shear deformation coefficient among the nailing soil at the corresponding position and the soil nail length (L1) outside the potential sliding surface. The horizontal stiffness coefficient of the micro-pile is calculated as per the cantilever beam or lateral load bearing pile. Some parameters presented in practical calculation method of soil nailing displacement are discussed including soil pressure style, shear displacement coefficient and calculation method of overall stability. One engineering example is used to demonstrate the validity of the proposed method .With the result derived from pullout tests, the practical calculation method can serve as a theoretical basis in the predictive control of soil nailing displacement.

     

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