黏性土地基中竖向圆孔的极限稳定深度研究

Research on stable limit depth of vertical cylinder hole in cohesive soil ground

工程中经常遇到打设竖向圆孔的问题,在黏性土地基中打设竖向圆孔,需要知道无护壁措施条件下竖向圆孔的极限稳定深度。首先进行坡面竖直边坡的极限平衡分析,假设破坏面为过坡趾的平面滑动面,建立滑动体极限平衡方程,得出边坡的极限稳定高度,结果与Taylor圆弧滑动面分析方法的结果比较吻合;然后将平面滑动面扩展到轴对称的含圆柱体竖向孔地基极限平衡分析,假定破坏面为通过圆柱体竖向孔底边缘的倒圆台侧表面,建立滑动体的极限平衡状态方程,得到和土坡极限平衡解答统一的c_u/yh(c_u为土体不排水抗剪强度,y为重度,h为竖向孔深度)和h/r(r为竖向孔半径)关系,利用该关系可以分析地基中竖向圆孔的稳定,为地基中竖向孔的设计提供依据;通过数值方法建立竖向孔不同几何参数的数值模型,计算含竖向孔地基能够维持稳定的c_u/yh下限值,和倒圆台滑动体极限平衡解答符合较好,进一步验证了所提极限平衡分析方法的合理性。

Vertical circular holes are often encountered in practices. The limit depth of without supporting is important for a stable vertical cylinder hole in cohesive soil. Firstly, if the failure surface is planar and pass through the slope toe, the stable limit height of the slope can be obtained by limit equilibrium analysis of vertical slope, and compared with Taylor＇s results by circular sliding surface. Secondly, planar sliding surface is extended to the axisymmetric problem for vertical cylinder hole in cohesive soil. Assuming the failure surface is an inverted round estrade, and a relationship between cu/yh and h/r can be solved by limit equilibrium analysis, and provide the basis in engineering design. Thirdly, vertical cylinder hole with different geometrical parameters are numerically modeled and the lower limiting values of cu/yh are summarized. The results show that limit equilibrium method results coincided well with the numerical analysis results.