基于H-B准则的公路桥梁桩基嵌岩深度计算

A calculation method for Rock-socketed depth of highway bridge pile based on Hoek-Brown strength criterion

基于Hoek-Brown强度准则,推导了在微小转动下嵌岩段桩侧法向应力及水平摩阻力计算模型,采用静力平衡原理建立了水平荷载作用下公路桥梁桩基嵌岩深度的计算公式,提出了嵌岩深度计算的新方法。参数敏感性及影响因素分析表明:(1)水平荷载引起的力矩HM、桩径d、岩层上覆压力σv、岩石单轴抗压强度σc、岩体类别参数0m、岩体地质力学分类指标RMR均对嵌岩深度有一定影响,在HM、d不变的情况下,岩体质量和岩石单轴抗压强度对嵌岩深度的确定最为敏感;(2)岩体质量越差,所需嵌岩深度越大;岩体质量越好,岩层上覆压力对嵌岩深度影响越小,反之越大。(3)嵌岩深度随岩石单轴抗压强度的提高呈非线性缓慢地减小,在相同的单轴抗压强度下,岩体质量越好,嵌岩深度越小,反之越大。

Based on the Hoek-Brown strength criterion, a calculation model of pile lateral normal stress and horizontal friction under small rotation is obtained. Using static equilibrium principle, a calculation formula for the rock-socketed depth of the highway bridge pile foundation under horizontal load is established. Furthermore, a new calculation method of rock-socketed depth is proposed. The analyses of parameter sensitivities and influence factors show that： （1） the torque MH caused by horizontal load, pile diameter d, strata overlying pressure бv, rock uniaxial compressive strength бc, rock mass category parameter M0 and the rock geomechanical classification index RMR have certain influences on the rock-socketed depth. While MH, d are unchanged, the rock quality and rock uniaxial compressive strength are the most sensitive factor to determine of rock-socketed depth. （2） The worse the rock mass quality is, the greater the rock-socketed depth is; the better the rock mass quality is, the smaller the influence of overlying pressure on the rock-socketed depth is, vice versa. （3） The rock-socketed depth nonlinearly decreases slowly with the increasing of rock uniaxial compressive strength, and under the same uniaxial compressive strength ,the better the rock mass quality is, the smaller the rock-socketed depth is, vice versa.