Impact of the intermediate stress component in a plastic potential function on rock mass stability around a sequentially excavated large underground cavity
Impact of the intermediate stress component in a plastic potential function on rock mass stability around a sequentially excavated large underground cavity
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DOI：
10.1016/j.ijrmms.2020.104223
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发表时间：
2020-03
影响因子：
7.2
通讯作者：
A. Sainoki;Duncan Maina;A. Schwartzkopff;Y. Obara;M. Karakus
中科院分区：
文献类型：
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作者：
A. Sainoki;Duncan Maina;A. Schwartzkopff;Y. Obara;M. Karakus
虽然考虑中间主应力分量的塑性势函数在弹塑性分析中得到了广泛的应用，但它对开挖引起的应力重分布的影响还没有得到充分的检验和验证。本研究不仅对弹塑性模型的解析解进行了检验，而且基于大型洞室开挖和深部地应力的连续测量进行了实例研究。解析解表明，屈服函数相同时，不同塑性势函数的体积塑性应变增量存在明显差异。具体地说，当σ2/σ1大于0.6时，德鲁克-普拉格(DP)塑性势函数产生的体积应变速率增量大于莫尔-库仑(MC)势函数的体积应变速率增量，从而表明围岩中围岩应力的增加。对具有不同势函数的大型洞室开挖的数值分析表明，在应力监测点，两种势函数产生了相似的开挖引起的应力变化，但围岩的破坏状态转变是不同的。当采用MC势函数时，围岩在整个开挖阶段不断发生破坏，而采用DP势函数的模型，随着开挖阶段的进行，由于与中间主应力分量相关的破坏岩体的体积膨胀而发生卸荷。这被发现与现场观测更一致。因此，我们得出结论，塑性势函数中的中间主应力对体积塑性应变的演化起着至关重要的作用，从而对岩体结构的整体稳定性产生影响，特别是对于裂隙岩体，当中间应力与小主应力值相比相对较大时。
Although plastic potential functions considering an intermediate principal stress component are widely employed for elasto-plastic analyses, its effect on excavation-induced stress re-distribution is not adequately examined and verified based on in-situ stress measurements. The present study addressed this issue by not only examining the analytical solutions of elasto-plastic models but also conducting a case study based on large cavern excavation and the continual measurement of the in-situ stress at a great depth. The analytical solutions indicate a clear difference in volumetric plastic strain increment between different plastic potential functions with the same yield function. Specifically, whenσ2/σ1exceeds 0.6, the Drucker–Prager (DP) plastic potential function produces an increase in volumetric strain rate larger than that of the Mohr–Coulomb (MC) potential function, hence suggesting the increase in confining stress in the surrounding rock mass. For the case study, the numerical analyses of the large cavern excavation with the different potential functions demonstrated that both the potential functions yield comparable excavation-induced stress change at the stress monitoring point, however the failure state transition of the surrounding rock mass is non-identical. When the MC potential function is employed, the surrounding rock mass continuously undergoes failure throughout the excavation stages, whilst for the model with the DP potential function, unloading takes place due to the volumetric expansion of failed rock masses associated with the intermediate principal stress component, as the excavation stage proceeds. This was found to be more consistent with field observations. Thus, we concluded that the intermediate principal stress in a plastic potential function plays a vital role in the evolution of volumetric plastic strain, thereby exerting an influence on the overall stability of rock mass structures, especially for a fractured rock mass and when the intermediate stress is relatively large, compared to the minor principal stress value.