浅埋弱胶结岩层流变损伤破裂演化及致灾机理

As the increase of large scale mining, variety of disasters caused by shallow-strata weighting is on the rise. It is urgent to investigate shallow-strata weighting as well as disaster-causing mechanism. In order to establish a theory of weakly cemented shallow-strata failure developing and disasters prevention, theoretical analysis, laboratory experiments, numerical simulations and in-situ investigations will be adopted to make the following innovative researches: (1)X-ray diffraction and SEM scanning will be adopted to learn the component and micro-structure of weakly cemented shallowly buried rocks, and a rheologic experiment by combining digital speckle correlation method will be done to understand the mechanism of weakly cemented shallow rocks rheologic-damage deformation, from microcracks generating to expanding, and macrocracks is formed at last. Rheologic-damage constitutive relation of weakly cemented shallow rocks will be established.(2)Based on the investigations of weakly cemented shallow strata damaged extents, distributions and grad variations, a structural mechanical model considering damage developing for shallow strata can be established, and shallow strata fracturing span can be deduced by considering micro-structure and damage property. (3) To investigate the relations between shallow strata structure failure developing and stress field, and to obtain a mechanical criterion for determine the catastrophe of shallow strata, by considering the property and rheolgic feature of weakly cemented strata. The research will fill up gaps in shallowly buried and weakly cemented strata failure developing and disaster-causing mechanism at home and abroad, and will supply a theoritcal support for safe and scientific mining in the western shallowly buried region in our country.

随着开采规模扩大，我国西部矿区浅埋岩层运动诱发灾害日趋严重，深入解答浅埋岩层运动规律及其致灾机理已刻不容缓。本项目以建立浅埋弱胶结岩层破坏演化及灾害防治基础理论为目标，拟采用理论、试验、数值模拟与现场测试相结合方法开展如下创新性研究工作:(1)通过X光衍射与SEM扫描研究获得浅埋弱胶结岩石组份与细观结构特征，基于流变与数字散斑同步试验, 深入揭示浅埋弱胶结岩石流变损伤、微裂纹萌生、扩展演化成宏观裂纹力学机制，建立流变损伤本构关系;(2)揭示浅埋弱胶结覆岩损伤破裂分布、程度及梯度变化规律，建立浅埋覆岩损伤破裂演化结构力学模型,导出凸显细观结构及流变损伤特征的岩层破断步距计算式;(3)揭示浅埋弱胶结岩层"破断结构演化－应力场"之间关系,获得岩层破断结构失稳灾变力学判据。本项目将填补基于细观结构与流变损伤研究浅埋岩层破裂演化及致灾机理方面空白,为我国西部浅埋煤炭资源科学安全开采提供理论支持。

本项目按照计划任务书的要求，采用理论研究、实验室试验、数值模拟与现场监测相结合的方法，围绕浅埋弱胶结岩层流变损伤破裂演化及致灾机理开展研究，取得了如下创新性成果：.（1）弱胶结砂质泥岩主要矿物成分为石英、伊利石、绿泥石及钠长石，其黏土矿物成分占比高达52.76%，岩石单轴强度8.8~9.6MPa；低应力水平下，岩石内部因流变产生的损伤较少，应力水平临近其破坏强度时，岩石内部损伤急剧增加。（2）通过试验获取完整及破碎砂质泥岩的流变特性，建立了考虑损伤基质承载作用的岩石流变损伤本构模型。（3）研究得到弱胶结覆岩煤层开采时，基本顶下方弱胶结岩块相互挤压并逐渐形成岩梁结构与高位大范围弱胶结岩层整体联动破断特征，建立了浅埋煤层工作面弱胶结顶板破断结构模型，获得了不同运动阶段顶板岩层结构失稳力学判据。（4）考虑煤柱及下层煤巷道失稳易诱发采空区覆岩二次破断，研究了煤岩单体及组合体力学性能，建立了煤岩体受压损伤本构方程，探究了采空区与煤柱下巷道开掘支护时围岩应力影响规律。（5）基于弱胶结岩层联动失稳造成覆岩裂隙贯通而致灾，提出了以浅埋弱胶结覆岩导通性为核心的覆岩失稳致灾评价方法，为采场覆岩溃水溃砂灾害防治提供依据。.本项目发表SCI/EI论文24篇，其中SCI TOP期刊论文6篇，ESI高被引论文2篇；国内外学术报告15次；获得省部级一等奖2项、二等奖2项；授权国家发明专利10项；培养博士后2名，博士3名(已毕业2人)、硕士6名(已毕业5名)。研究成果为我国西部浅埋煤炭资源的科学、安全开采，提供了理论支持与科学依据，应用价值高。