深部软弱岩体峰后等效力学模型及数值计算研究

Equivalent mechanical model for post-peak behaviors of deep soft rock and numerical computation

软弱岩体给深部开采工程中的巷道支护等带来一系列棘手的问题,深入研究深部软弱岩体峰后非线性破坏行为,对于保证深部巷道围岩的安全稳定性具有十分重要的意义。基于连续介质理论及量化GSI围岩评级系统,依据Hoek-Brown强度准则,通过理论分析并结合前人的研究成果详细论证了等效节理岩体应变软化模型在深部岩体力学理论上的科学性与可行性。采用程序语言在FLAC3D中编写等效节理岩体应变软化模型,分别采用常规弹塑性模型与应变软化模型对比分析深部围岩开挖面空间效应曲线;结合深部竖井支护工程设计及现场应用等进行了算例验证。得出结论如下:等效节理岩体应变软化模型所体现软弱岩体峰后强度参数衰减规律表明:岩体峰后行为受岩体质量等级和围压的影响较大,围岩在峰后卸载过程中软化参数并不是恒定值,而是随着围压的大小而变化;通过对深部软弱围岩开挖面空间约束效应曲线的计算可知,基于Mohr-Coulomb和Hoek-Brown强度准则的理想弹塑性模型计算结果基本一致,弹塑性模型与应变软化模型的计算结果相差较大,主要体现在中等地质指标范围;现场实际应用表明,等效节理岩体应变软化模型能够较为真实的反映深部软弱岩体的峰后力学行为,并在围岩地质强度指标与岩体连续介质理论之间建立联系,便于工程应用,并可为类似工程提供借鉴。

Based on the continuum theory, quantitative GSI rock rating system and Hoek-Brown strength criterion and by using the FLAC3D program as the development platform, the conventional plastic model and strain-softening model are adopted to comparatively analyze the spatial excavation surface effect curves of deep rock. Combined with engineering design and field applications of deep shaft support, numerical validation is performed. The equivalent strain softening model for jointed soft rock reflecting attenuation of the post-peak strength parameters shows that:the post-peak behaviors of rock mass are dominated by quality grade and confining pressure, and during unloading after the peak, the process of softening parameter is not a constant value and varies with the size of the confining pressure. By computing the excavation face spatial constraint response curves of deep soft rock, the calculated results based on Mohr-Coulomb and Hoek-Brown criterion ideal elastoplastic models are basically the same. The results of the elastoplastic model are quite different from those of the strain-softening model, mainly in the middle range of geological indices. Practical application shows that the equivalent strain softening model for jointed rock more truly reflects the post-peak mechanical behaviors of the deep soft rock, and furthermore, the link between the geological strength indices and the continuum theory is established for engineering applications so as to provide a reference for similar projects.