基于改进的Mohr-Coulomb强度准则下岩石锚杆极限抗拔承载力计算

A method for calculating ultimate pull-out capacity of rock bolt based on modified Mohr-Coulomb failure criterion

岩石锚杆基础作为风电机组基础的一种特殊基础型式,可以充分发挥原状岩体的力学性能,具有良好的抗拔性能。已有研究表明,小而非零拉伸截断改进的Mohr-Coulomb(简称M-C)强度准则更适用于描述岩体的破坏特性。基于小而非零拉伸截断改进的M-C强度准则,建立破坏面上单位面积的能量耗损率表达式。从塑性力学极限分析上限定理出发,构建岩楔体平移破坏机构。根据外部作用荷载和岩楔体自重所做的外功率与沿岩楔体圆破坏锥面的能量耗损率相等的条件,建立虚功率方程,并由此得到了岩石锚杆极限抗拔承载力的计算公式。经原型试验验证,推导公式所得计算值与实测值一致性较好,具有一定的可靠性,且能满足工程实际应用要求。

The rock bolt foundation is a special type of wind turbine foundation. It shows a good pull-out performance, and can well demonstrate mechanical properties of rock mass in its original state. Recent studies indicate that the modified Mohr-Coulomb（M-C） failure criterion with a small but not zero tension cut-off is more applicable for describing failure characteristics of rock masses. According to the modified M-C failure criterion, an expression is derived with the energy dissipation rate per unit area. Furthermore, the planar translational failure mechanism of rock wedge is put forward, which is based on the upper bound theorem for the limit analysis of soil plasticity mechanics. A virtual power equation is deduced, when the work rate of external loads to self-weight of rock wedge equals to the rate of energy dissipation along the sliding surface of rock wedge. Then a formula is developed for calculating ultimate pull-out capacity of rock bolt. The prototype test results show that the calculated values by this formula are in good agreement with the measured values, which indicates the formula with certain reliability can meet the requirements of engineering application.