【作者】 张壮路；

【导师】 虎维岳； 董书宁；

【作者基本信息】 煤炭科学研究总院 ， 矿产普查与勘探， 2009， 博士

【摘要】 自然界中的渗流现象天然地存在于两种不同的介质中:孔隙介质和裂隙(缝)介质。流体渗流模拟的连续介质方法通常适用于多孔地质体,目前常用的地下水模拟方法均基于地下水是在连续的地质体中流动,这并不一定适用于裂隙岩体;由于裂隙分布及其特征与孔隙差异较大,若流体渗流主要受裂隙的控制,对于一定尺寸的裂隙岩体,多孔介质假设则较难刻划裂隙岩体的渗流特征。当煤层周围赋存有含水层时,巷道的开挖及煤层的开采会造成岩体应力重新分布,特别是煤层被采出之后,其上覆岩层与底板岩层的原始应力平衡状态会遭到破坏,形成垮落带、裂隙带(导水裂隙带)、弯曲整体移动带三个带,将导致岩体的渗透性能发生变化。从水文地质、工程地质、开采扰动、岩体力学等诸多方面入手,研究采动条件下裂隙网络的渗流场及其演变规律,研究顶板冒裂诱发工作面涌水规律及其主要影响因素,对于正确认识由于采动而引起的工作面的涌水机理,评价和预测工作面涌水及其工作面涌水量非常必要。本文分两大部分进行了渗流与应力耦合模型预测工作面顶板涌水量的理论和应用研究。第一部分重点就采动裂隙岩体渗透性及工作面顶板涌水量预测进行了理论分析和数学推导,推导和讨论了裂隙岩体渗透特征,研究了采动应力场,对工作面回采过程中覆岩的垮落过程进行了数值模拟,并对应力场与渗流场的相互关系进行耦合研究。对裂隙岩体中所存在的渗流场与应力场之间的相互影响称为耦合作用,其主要表现在以下两个方面:a、当裂隙岩体中有渗流发生时(即存在渗流场),地下水渗流在裂隙岩体中引起的渗流作用力(包括静水压力和动水压力)将改变岩体中原始存在的应力状态(即裂隙岩体赋存的应力场环境);b、裂隙岩体中应力状态的改变,又将影响岩体结构,进而改变裂隙岩体的渗透性能,表现为裂隙岩体中地下水渗流场的改变。第二部分针对榆阳煤矿2301工作面开采过程中遇到的顶水开采的具体问题,研究了煤层顶板含水层的富水特性及采动覆岩运动破坏规律,预测了采动工作面的涌水量,数值模拟计算和根据经验公式计算得出导水裂隙带高度65m,已经发育到真武洞砂岩含水层内,开采直接沟通该含水层:为防止基岩风化带潜水含水层导入工作面内,需留设的防水安全煤岩柱的高度是111.35m,而煤层顶板距基岩风化带含水层底板距离为163.09m,可以实现安全开采。并通过与实际涌水量进行对比,检验了计算方法的正确性,为矿井安全生产提供了依据。通过理论分析与模拟实验研究,根据采动对上覆岩层的破坏特征尤其是对渗透特征的改变,首次将裂隙带划分为网络裂隙区、方向裂隙区和离层裂隙区;首次提出了考虑多层含水层充水及含水层弹性释水的垮落法工作面涌水量计算公式,计算方法更精确、符合实际。更多还原

【Abstract】 Seepage exists naturally in two different kinds of media: porous medium and fracture medium. Continuous medium method simulating liquid seepage is generally suitable to porous geological bodies, groundwater simulation method commonly used at present is based on continuous movement of groundwater in geological bodies and is not certainly suitable to fractured rocks. Since the distribution and characteristics of fractures are considerably different from those of pores, if liquid seepage is mainly controlled by fractures, assumption of porous medium has difficulty in characterizing seepage of fractured rocks.When an aquifer exist around a coal seam, excavation of roadways and extraction of coal seam may induce redistribution of rock stress, particularly after extraction of coal seam, the equilibrium status of original stress in rocks of overlying strata and floor is destroyed, forming three zones: collapsed zone, fractured zone and bending zone, inducing variation of rock permeability. From the aspects such as hydrogeology, engineering geology, mining disturbance and rock mechanics etc, to study the seepage field and the evolution regularities of fracture network, the regularities of inflow induced by collapse and fracturing of roof at working face and their main inflowing factors, is very necessary for correctly understanding inflow mechanism induced by mining disturbance at working face, evaluating and predicting inflow and inflow volume at working face. The paper consists of tow parts studying the theory and application of prediction of inflow volume in roof at working face by seepage-stress coupling model.The first part focuses on theorical analysis and mathematical derivation for prediction of permeability of disturbed fractured rocks and inflow volume in roof at working face, derived and discussed characteristics of permeability in fractured rocks, studied stress field under mining disturbance, conducted numerical simulation for collapse process of overlying rocks during stopping at working face, studied the relation between stress field and seepage field. The coupling effect formed due to multual impact of seepage field and stress field in fractured rocks was represented by two following aspects: a. when seepage occurred in fractured rocks(i.e. when seepage field existed), seepage action( including static pressure and dynamic pressure) induced by groundwater seepage in fractured rocks would change the original stress status in rocks(i.e. stress field environment in fractured rocks); b.the change of stress status in fractured rocks would impact the structure of rocks, so changing the performance of permeability in fractured rocks, which was represented by variation of groundwater seepage field in fractured rocks.The second part of the paper studied water abundance characters of roof aquifer of coal seam and regularities of movement and destruction of disturbed overlying rocks on the basis of the actual problem of roof water encountered during extraction at working face 2301 in Yuyang mine, predicted the inflow volume at disturbed working face. From calculation of numerical simulation and empirical equation, the height of water-conducting fracture zone was 65 m, and the zone had developed into Zhenwudong sandstone aquifer, and mining directly connected the aquifer. In order to prevent water from phreatic aquifer in weathered zone of bedrock from coming into working face, water prevention pillars of 111.35 m height were left, while the distance from the roof of coal seam to the floor of aquifer in weathered zone of bedrock was 163.09 m, therefore safe mining could be realized. Through comparison with actual inflow volume, the calculation method was proved correct, providing basis for safe production of mine.Through theorical analysis and study of simulation test, on the basis of destruction characteristics of overlying rocks and variation of permeability characteristics due to mining, we subdivided for first time the fracture zone into network fracture zone, directional fracture zone and separated layer fracture zone, firstly proposed formula for calculation of water inflow at collapsed working face in consideration of water filling of multiple aquifers and elastically desaturation of aquifer. The calculation method is more accurate and more corresponding to the actuality.更多还原