深部软岩巷道围岩扩容与流变特性模拟研究及应用
Simulation study on dilatant and rheologic properties of soft rocks surrounding deep roadway and its application
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摘要: 深部软岩回采巷道围岩劣化、扩容和流变效应显著。 基于增量塑性流动理论和流变理论, 将改进伯格斯体、改进黏塑性体和应变软化塑性体串联建立了 BVS 模型,可描述围岩应变软化、塑 性扩容、蠕变三阶段、稳定与非稳定蠕变、流变损伤和流变扩容 6 个力学特性。 推导了该模型的三 维增量本构方程,并开发出可供FLAC3D调用的数值形式。 结合三维增量本构方程导出的参数辨识 公式和中煤能源新集口孜东煤矿岩样试验数据,辨识了 BVS 模型的 19 个输入参数,并采用试验数 据、理论解和数值计算结果相互印证的方式,对多种加载条件下单元件应力-应变响应、力学特性 和模型整体进行严格校核。 将 BVS 模型用于口孜东煤矿 121302 运输巷进行数值模拟计算,结果 表明:掘进扰动较弱;流变期间围岩大范围持续劣化,呈顶板下沉量较小、巷帮锚固体整体内移和剧 烈底臌的特点;回采影响强烈,使围岩大范围劣化,巷道断面强烈变形。 底板泥岩持续臌起驱动不 断扩容的底煤挤入巷道空间是发生剧烈底臌的主要原因;底板深度 1.5 m 处流变直接导致的软化 参量全程仅占比0~16%,但流变损伤引起应力调整,间接导致软化参量增大。 将数值模拟计算结 果与井下实测数据进行了对比分析,表明 BVS 模型基本能反映深部软岩回采巷道围岩变形与破坏 规律,但是 2 者还存在较大差异,仍需进一步完善 BVS 模型。Abstract: Surrounding rock deterioration,dilatancy and rheology are significant in deep soft rock roadways. Based on the incremental plastic flow theory and the rheological theory,a BVS model was established by connecting an im⁃ proved Burgers body,an improved viscoplastic body and a strain⁃softening plastic body in series,which can describe six mechanical properties of surrounding rock: strain softening, plastic dilatancy, three creep stages, steady and unsteady creep,rheological damage and rheological dilatancy. The three⁃dimensional incremental constitutive equations of the model were derived,and the numerical form that can be invoked by FLAC3D was developed. Combined with the parameter identification formulae derived from the three⁃dimensional incremental constitutive equations and the test data of rock samples from the Kouzidong Coal Mine,Xinji Mining Area,China,19 input parameters of the BVS model were identified. The test data,theoretical solutions and numerical results were mutually verified to strictly check the stress⁃strain response of each element under various loading conditions,each mechanical property,and whole model. The BVS model was applied to the numerical simulation of the 121302 headgate in the Kouzidong coal mine. The re⁃ sults show that the roadway disturbance is relatively weak. During the rheological period,the surrounding rock deterio⁃ rates in a large range,showing the characteristics of slight roof subsidence,shoulder corner coal dilatancy,whole wall inward migration and severe floor heave. The mining disturbance is significant, which induces the surrounding rock to deteriorate in a large range and the roadway section deforms strongly. The continuous heave of the floor mud⁃ stone drives the dilating bottom coal to squeeze into the roadway space, which is the main cause of the severe floor heave. The softening parameter directly caused by rheology at the depth of 1.5 m of the floor only accounts for 0-16% of the whole process,but the rheological damage causes stress adjustment,which indirectly leads an increase in the softening parameter. By comparing the numerical simulation results with the field measuring data,it is pointed out that the BVS model can basically describe the surrounding rock deformation and failure law of deep soft rock min⁃ ing roadways. However,there are still significant differences between them,and a further refinement of the BVS model is needed.