沿充填体掘巷高支承压力下底板应力演化及其变形机制

At present, roadway protection without coal-pillars is mainly achieved through the gob-side entry retaining and roadway driving along goaf technology. Once the gob-side entry retaining suffers the mining twice, it is difficult to maintain the roadway. A coal pillar must be set up in roadway driving along goaf technology, which causes permanent loss. To realize the thick coal-seam mining without pillar, the technology of roadway driving along backfill in fully-mechanized caving face was raised in domestic and carried out in some coal mines. Post-peak creep sliding along the fracture surface led to intense floor heave in roadway driving along backfill. Due to lack the research to evolution of floor stress and its deformation mechanism with high abutment pressure in roadway driving along backfill, intense floor heave will pose a major threat to personnel, transport, ventilation, etc. The post-peak creep features of floor rock and its constitutive equation can be obtained by 3D creep experiment in roadway driving along backfill. Floor mechanics model in roadway driving along backfill is built and the distribution characteristics of floor abutment pressure is analyzed by using post-peak creep constitutive equation to study the different mining conditions, the thickness of coal rock layer as well as the elastic modulus. Moreover, it also can reveal the main factors affecting the stability of floor and the influence rules of each factor. The evolution of floor stress and deformation characteristics is analyzed during the whole process of twice excavation by the similar simulation and numerical model based on the creep equation in order to reveal the mechanism of floor heave. Achievements can provide scientific basis for mining engineering of roadway driving along backfill. At the same time, roadway driving along backfill is a special case of roadway driving along goaf, the study of which will supplement the mechanism theory of floor heave in roadway driving along goaf.

目前无煤柱护巷主要有沿空留巷和沿空掘巷，沿空留巷受两次采动，巷道维护困难；沿空掘巷需留设煤柱，造成永久损失。为实现厚煤层的无煤柱开采，国内提出了并在若干矿山采用了沿充填体掘巷，该方法由于沿破裂面滑移的峰后蠕变致使沿充填体掘巷底鼓强烈，对井下安全造成重大威胁。为此，本项目拟进行沿充填体掘巷高支承压力下底板应力演化及其变形机制的研究。拟通过三轴蠕变实验得到沿充填体掘巷底板岩石峰后蠕变特性和本构方程；建立沿充填体掘巷底板力学模型，并运用蠕变方程分析不同的开采条件、煤岩层厚度及弹性模量等对底板支承压力的分布规律，探明影响底板稳定的主要因素并揭示各因素的影响规律；采用相似模拟和基于蠕变方程的数值模型分析“二次掘采”全过程底板应力演化及变形破坏特征，揭示底鼓机理。研究成果可为沿充填体掘巷工程实际提供科学依据，同时，沿充填体掘巷作为沿空掘巷的一种特例，该研究将对沿空掘巷底鼓机理方面的理论进行补充。

沿充填体掘巷能够实现厚煤层的无煤柱开采，该方法由于沿破裂面滑移的峰后蠕变致使沿充填体掘巷底鼓强烈，对井下安全造成威胁。本项目针对沿充填体掘巷高支承压力下底板应力演化及其变形机制的问题进行深入研究，探究了底板稳定性的影响因素及其作用规律，系统研究了沿充填体掘巷“二次掘采”全过程底板支承压力演化过程，并揭示了底鼓机理，同时提出了相应的控制对策。得出了以下主要结论：.（1）得到沿充填体掘巷底板岩石峰后蠕变特性，通过分析蠕变整个过程，理论推导得到中粒砂岩粘弹塑性蠕变力学模型的本构方程；.（2）建立了沿充填体掘巷底板力学模型，得到底板岩层中任意一点的应变分量；.（3）通过数值模拟探究了埋深、侧压系数、围岩厚度、围岩岩性、充填体强度、基本顶断裂线位置等因素对底板稳定性的影响规律，结果表明埋深、直接底和充填体强度对稳定性的影响较为突出，而当基本顶在充填体上部破断时，底鼓量最大；.（4）通过相似模拟和数值模拟探讨了沿充填体掘巷“掘采”全过程中底板支承压力演化过程及底板变形规律。研究得到：“一次掘巷”过程中，作用在两帮下方底板的支承压力出现不对称分布；“一次回采”过程中，底板出现两个支承压力峰值，且实体煤下方底板支承压力略高于充填体下方底板的支承压力；“二次掘巷”过程中，充填体帮底板同时受到卸压和高支承压力的影响，巷道产生明显底鼓；“二次回采”过程中，巷道围岩二次变形，引起底板鼓起量进一步增大，并在工作面超前5m处时底鼓量达到最大值。.（5）沿充填体掘巷底鼓主要由底板帮角处的剪切滑移和底板中部的拉伸变形构成，由此提出了加固底板和底板卸压两种底板稳定性控制措施。