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基于三剪统一强度准则,采用更符合脆性岩石峰后强度特性的弹-脆-塑性模型,推导了考虑第二主应力和脆性软化共同影响的隧道围岩应力解,并与广义Hoek-Brown强度准则解进行了比较。研究结果表明:第二主应力、围岩材料模型、脆性软化均对围岩应力大小及分布具有显著影响。本文准则参数b=0时的应力解析解与广义Hoek-Brown强度准则应力解的峰值和分布规律均有较好的一致性,说明了本文应力解的合理性;当岩体强度具有明显的第二主应力效应时,广义Hoek-Brown强度准则已不再适用,但本文准则参数b>0时的应力解则具有很好的适用性。同时,理想弹-塑性模型低估了围岩塑性区范围,在准则参数b分别为0、0.05、0.1的情况下,弹-脆-塑性模型的围岩塑性区半径R相比理想弹-塑性模型平均可以增大45.5%;考虑第二主应力效应可以更加充分发挥岩石材料的强度潜能,随着准则参数b的增大,即第二主应力σ2效应的增大,围岩塑性区半径R和临界支护力py均不断减小,相比准则参数b=0时最大值分别减小了18.9%和10.8%。峰后粘聚力cr对围岩应力的影响也很显著,随着峰后粘聚力cr的增加,塑性区半径R不断减小,cr=0.11 MPa时的塑性区厚度比cr=0.055 MPa时减小43.3%。
Based on the triple shear unified strength criterion, the stress-solution of tunnel surrounding rock considering the combination of second principal stress and brittleness softening is deduced by using the elastic-brittle-plastic model which is more in line with the post-peak strength of brittle rock. The standard solution is compared. The results show that the second principal stress, the surrounding rock material model and the brittle softening all have a significant effect on the stress and distribution of surrounding rock. In this paper, the stress analytical solution of parameter b = 0 is in good agreement with the peak value and distribution law of generalized Hoek-Brown strength criterion, which shows the rationality of stress solution in this paper. When the strength of rock mass is obviously The generalized Hoek-Brown strength criterion is no longer applicable in the case of two principal stress effects, but the stress solution of parameter b> 0 in this paper has good applicability. At the same time, the ideal elastic-plastic model underestimates the plastic zone of the surrounding rock. When the criterion parameter b is 0, 0.05 and 0.1 respectively, the radius R of the plastic zone in the elastic-brittle-plastic model is lower than that of the ideal elastic-plastic model The average increase of 45.5%. Considering the effect of the second principal stress, the strength potential of rock material can be fully utilized. With the increase of the criterion parameter b, ie the increase of the second principal stress σ2, the radius R The critical support force, py, decreases continuously, decreasing by 18.9% and 10.8% respectively when compared with the criterion parameter b = 0. After the peak cohesion cr impact on the surrounding rock stress is also significant, with the peak cohesion cr increases, plastic zone radius R decreases, cr = 0.11 MPa when the plastic zone thickness than cr = 0.055 MPa Reduce 43.3%.