深井大断面沿空留巷底鼓动态演化机理及其分类防控

Due to the facts that it is an inevitable trend to exploit deep coal and adopt large-section roadway, that the gob-side entry retaining is one of the directions of coal mining development, and that floor heave phenomenon is common in the gob-side entry retaining, the research on floor heave is of important theoretical value and engineering significance and its result has wide application prospect. An integrated research method of theoretical research, laboratory test, numerical simulation and field survey, etc. is to be applied to carrying out the following innovative research work: (1) to systematically study the mechanical mechanism and evolution of the roof, ribs and floor in the gob-side entry retaining, and to reveal function mechanism of surrounding rock condition and stress environment in the roof and floor to floor heave, and to establish mechanical model of surrounding rock and its constitutive relations in different stages of the gob-side entry retaining with large section in deep mine under typical geological conditions; (2) to reveal spatial-temporal interaction among exploiting activity, surrounding rock, roadway support (basic support, reinforcing support, roadside support) and stress environment, and the dynamic evolution mechanism of floor heave; (3) to put forward overall categories and subcategories of the gob-side entry retaining and the principle of stability control on floor heave, to design controlling parameters of floor heave on the basis of nonlinear large deformation theory, and to establish basic theory of controlling floor heave in the gob-side entry retaining with large section in deep mine which suits the state of China.

煤矿开采向深部发展和采用大断面回采巷道是必然趋势，沿空留巷技术是煤矿开采发展方向之一，底鼓现象在沿空留巷中十分普遍,开展本项目研究具有重要理论价值和工程意义，研究成果具有广阔的应用前景。本项目采用理论研究、实验室试验研究、数值模拟和现场实测等综合研究方法，拟开展如下创新性研究工作：（1）应用系统的思想研究沿空留巷顶板、两帮与底板围岩变形力学机制及转化，揭示顶板和两帮的围岩性态及应力环境对底鼓的作用机制,构建典型地质条件下的深井大断面沿空留巷在不同阶段的围岩结构模型及其本构关系；（2）揭示开采活动、沿空留巷围岩、沿空留巷支护体（基本支护、加强支护及巷旁支护）、应力环境之间的时-空互动关系及底鼓动态演化机理；（3）提出深井大断面沿空留巷整体分类和次分类方法以及底板岩层稳定控制原则，以非线性大变形理论为主要理论基础进行底鼓控制分类设计，建立适合我国国情的深井大断面沿空留巷底鼓防控基础理论。

沿空留巷技术是煤矿开采发展方向之一，底鼓现象在沿空留巷中十分普遍，深井大断面沿空留巷底鼓控制尚存在诸多难题。因此，以淮南典型地质条件为背景，数值模拟研究了留巷跨度、充填体宽度、采高、采深等因素对围岩变形特征影响；利用自行设计研发的两向四面可调加载试验装置，模拟研究了深井大断面沿空留巷分阶段底板受力与应力演化特征，并采用分形几何理论，分析描述了底板裂隙场演化及顶底、帮底协调变形特征。应用岩石蠕变力学、损伤力学、断裂力学等，构建了沿空留巷不同阶段的底板力学模型，计算出不同区域底板的作用力，推导出巷道支护体上弹性变形地压、塑性变形地压及松动地压计算式，并引入等效载荷的概念，建立了底板等效载荷分布力学模型，推导出留巷不同阶段底鼓变形计算式。将弹性变形区围岩材料的畸变特性视为Burgers体，采用拉普拉斯变换，计算出巷道支护体上的流变压力。采用弹塑性力学中的J积分理论，推导出巷道关键点位置宏观裂纹失稳扩展准则。基于损伤力学理论，推导出底板梁的蠕变损伤断裂判据。应用关键层理论和顶板载荷条带分割模型，确定了顶板硬岩层的位置及其所控的软岩层组、破断顺序，以及顶板垮断极限层位置，计算出本工作面及相邻工作面的采动应力，研究了顶板、两帮与底板围岩变形力学机制及转化，分析了深井大断面沿空留巷顶板和两帮的围岩性态及应力环境对底鼓的作用机制。基于此，提出了主分类按顶板、帮部围岩岩性不同分为“硬顶硬煤型”、“软顶硬煤型”、“硬顶软煤型”、“软顶软煤型”，以及次分类按底板岩性、分层厚度分为“硬底“、“软底”的分类方案，并研究了不同类别底板分阶段底鼓演化特征，提出了“软弱顶帮加强支护、厚硬顶板切顶卸压、硬顶硬底同控及软弱底板注浆加固、巷旁支护与顶板强度匹配”等底鼓防控原则，确定了“掘巷期间软弱煤帮条件下加固帮角围岩、一次留巷前坚硬顶板条件下切顶卸压及二次采动影响前超前加强支护”等分类防控措施，工程实践应用效果良好。