向家坝水电站地下厂房围岩稳定的黏弹塑性有限元分析

Viscoelasto-plastic finite element analysis of stability of surrounding rock for underground powerhouse of Xiangjiaba hydro-power station

考虑流变作用,建立三维有限元模型进行数值计算,以洞室变形和点抗滑安全系数为指标,针对向家坝水电站地下厂房围岩的特殊性进行稳定性研究,结果表明,随着围压的增高,流变速率逐渐减小,初始应变逐渐减小;软弱夹层处流变速率较其他岩体减小缓慢,且开挖后流变达到稳态状态时软弱夹层最终流变位移较大;黏弹塑性下围岩位移分布及变化规律与弹塑性一致,但黏弹塑性下计算位移明显要比弹塑性大;流变效应对岩体变形和稳定性,以及对支护结构有重要影响;黏弹塑性情况下,洞室围岩特征点抗滑安全系数比弹塑性条件下小,软弱夹层出露处和拱顶点抗滑安全系数较低,点抗滑安全系数分析还表明,软弱夹层对其稳定性影响明显,验证了位移分析结果。

A three-dimensional finite element model for numerical calculation is established considering rheology. According to particularity of the surrounding rock for underground cavern of Xiangjiaba hydro-power station, stability of surrounding rock is studied based on the indexes of cavern deformation and point safety factor against sliding. It is shown that the rheological speed rate and initial strain decrease gradually with confining pressure increasing. Compared with other rocks, the theological speed of soft interlayer decreases slowly. Finally rheological displacement of soft interlayer is larger than other states when rheology reaches a lower state. The displacement distribution and change law of surrounding rock of viscoelastic-plasticity and elastoplasticity are uniform; but the calculation displacement of viscoelasto-plasticity is larger. An important influence on rock deformation, stability and support structure is done by rheological effect. At the state of viscoelastic-plasticity, characteristic points＇ safety factors against sliding are less than characteristic points＇ safety factors of elastoplasticity, point safety factor against sliding of soft interlayer and cavern arch crown. It is also shown that the soft interlayer has an important influence on stability of surrounding rock for underground cavern by studying point safety factor against sliding; accordingly, the displacement analysis results are verified.