基于Hoek-Brown破坏准则的浅埋条形锚板抗拔力上限分析

Upper bound solution of ultimate pullout capacity of strip plate anchor based on Hoek-Brown failure criterion

现有的锚板极限承载力研究大多是采用线性或非线性Mohr-Coulomb破坏准则在砂质地基中进行的,然而Mohr-Coulomb破坏准则并不适合分析岩质地基中的抗拔结构。采用Hoek-Brown破坏准则构建了一个曲线型的破坏机制,根据极限分析上限定理求出了条形锚板抗拔力的表达式。通过变分计算,得到了极限状态下条形锚板的抗拔力和岩体破裂面的上限解。为了证明所采用方法的有效性,当材料参数B=1时,采用与Mohr-Coulomb破坏准则等效的土体参数,计算了曲线型破坏机制下条形锚板的极限抗拔力,并与已有计算结果进行了比较。结果表明,采用曲线型破坏机制得到的锚板极限抗拔力与直线型多块体破坏机制的结果基本一致,证明了所采用的曲线形破坏机制是正确的。参数研究表明:在其他参数不变的情况下,锚板极限抗拔力和破坏面都随岩体参数B的增大而减小。

The existing studies of ultimate pullout capacity of plate anchor which employed linear and nonlinear Mohr-Coulomb failure criterion have been achieved in sand. However, the Mohr-Coulomb failure criterion is unsuitable for calculating the ultimate pullout capacity of plate anchor in rock foundation. Based on the Hoek-Brown failure criterion, a curved failure mechanism is constructed and the expression of pullout capacity of plate anchor is derived in the framework of upper bound theorem of limit analysis. The upper bound solutions of ultimate pullout capacity and failure surface for plate anchor are obtained with the help of variational calculation. To evaluate the validity of this method, the ultimate pullout capacity of curved failure mechanism is calculated by using equivalent parameters of Molar-Coulomb criterion when parameter B=1. The solutions are compared with the results presented in the existing literatures. The good agreement between the results of curved failure mechanism and the solutions computed by linear multiple blocks failure mechanism shows the upper bound solutions calculated by curved failure mechanism is effective. According to the results of parameters analysis, both the ultimate pullout capacity and failure surface decrease with the increase of rock parameter B when other parameters are fixed.