【作者】 张改玲；

【导师】 姜振泉；

【作者基本信息】 中国矿业大学 ， 地质工程， 2011， 博士

【摘要】 矿井溃砂地质灾害对煤矿井筒、巷道、采场等正常使用和安全生产构成了严重威胁。化学注浆固砂技术被普遍地应用于溃砂灾害治理中。注浆体的渗透性是其岩土工程性质的一个重要方面。本论文依托国家自然科学基金项目“矿井溃砂地质灾害化学注浆治理机制与过程监控(项目批准号:40772192)”,采用模型试验、高压渗透试验和微观分析等方法,对化学注浆浆液扩散规律、注浆固砂体渗透性分区、化学注浆固砂体的高压渗透性以及抗渗的微观机理进行了研究。主要工作和获得的认识如下:(1)在对数个矿区厚松散层的结构、层组特点、物质组成、物理力学性质等工程地质特性研究的基础上,重点分析了厚松散砂层的物理力学性质和渗透特性随着深度的变化,发现矿区深部砂层针对粒状注浆材料的可注性较差。(2)获得了半胶结砂岩化学注浆前和注浆后的渗透系数。注浆前半胶结砂岩的渗透系数和有效粒径及≥0.5mm粗粒含量呈近似指数函数关系;第一次注浆半胶结砂岩的可灌注性主要取决于试样的大开口孔隙率,第二次注浆后其抗渗性能趋于接近。(3)获得了化学浆液在半胶结砂岩柱体中的扩散规律,浆液渗透的界面呈中心略低,周边略高的曲面形状;注浆钻孔周边浆液随着时间基本上呈同心圆状扩展;在相同注浆压力下,浆液在不同渗透性介质中的扩散速度具有明显差异。(4)获得了化学浆液在松散砂中扩散浓度的变化。浆液的浓度随着距注浆孔距离有降低趋势,但是也存在局部富集现象。化学浆液浓度的分区必然会造成注浆砂体渗透性和抗渗性能的差异。(5)研制了气压控制式注浆试样制备装置。该装置可以模拟不同深度和不同压力环境下的双液或单液化学注浆。(6)进行了高围压和高渗透压差条件下的化学注浆固砂体的渗透试验研究。试验发现随着渗透压差的增大,渗透系数增大。但是,围压对渗透系数的影响表现出不同的特点,一般地,围压的增加导致含较大比例化学浆液的固砂体的渗透系数降低;高围压条件下,纯净的砂的化学注浆体,由于颗粒破裂,造成在高围压条件下渗透系数反而增加。(7)提出了化学注浆固砂体的微孔孔径结构的分类方案及其孔喉简化模型。化学注浆固砂体中的孔隙,主要是以大孔和超大孔为主,孔隙连通性好,少量半封闭孔隙,而化学注浆半胶结砂岩内存在着细颈瓶孔,连通性变差。孔喉结构模型揭示了化学注浆固砂体的防渗微观机理,明确了决定化学注浆固砂体抗渗性能的主要因素是孔隙的充填程度、颗粒内裂隙、浆液固结体内裂隙以及颗粒-浆液边界裂隙的发育程度。(8)获得了化学注浆固砂体的孔隙结构与渗透性的关系。随着浆液含量的增加,化学注浆固砂体的总孔隙体积、总孔比表面积增加,孔隙率增大,体积中值孔径、平均孔径减小;渗透系数随浆液含量增加而明显减小,渗透系数与孔隙喉道比、体积中值孔径、平均孔径成正比。更多还原

【Abstract】 Quicksand or sand and water inrush in underground coalmines have threatened the production safety, regular service of shafts, tunnels and panels. Chemical grouting technology for seepage prevention and strata enforcement technologies has widely utilized in the treatment of shaft rupture and quicksand hazards prevention. Permeability of grouted sand is one of important geotechnical properties, This dissertation focuses on the permeability and anti-seepage mechanism of chemically grouted sands, Which is a part of the project“Mechanism and process control of chemical grouting treatment for quicksand hazards in coalmines”supported by National Natural Science Foundation of China (NSFC) under Grant No. 40772192. Chemical grouts propagation and permeability partitioning features of grouted sand, high pressure permeability of chemically grouted sands and its micro-mechanism of anti-seepage were studied through scaled model test, permeability test under high cofining pressure and microanalysis. The main understandings are as follows:(1) The engineering geological characteristics of thick unconsolidated formations in coal mining areas, such as structure, layer group characteristics, composition, physical and mechanical properties were analyzed in detail. Permeability for sand in the thick unconsolidated layers changes with depth were investigated from the view of penetration and groutability. And sand granulometric composition in several deep coal mining areas indicates their poor groutability for granular grouts.(2) Semi-cemented sandstone specimen were simulated, and permeability before and after chemical grouting for the specimen has been tested. Results show that the permeability for the semi-cemented sandstone specimen mainly depends on the effective grain size and the content of coarse sand. Hydraulic conductivity and effective grain size and coarse particle content have an approximate relationship of exponential function. Grouting simulation tests indicate that groutability to semi- cemented sandstone for the first time under certain osmotic pressure difference depends largely on the porosity with large opening (the water absorption at atmospheric pressure). After the second grouting, impervious performance of chemically grouted semi- cemented sandstone tends to be equivalent.(3) A simulated grouting experiment was conducted on semi-cemented sandstone and results show that interface of grout penetration in sandstone column is a curved surface with the surrounding slightly below the center. Grouting infiltration over time around the grouting borehole is basically a concentric circle-shaped extension. Grouts diffusion rate in the different permeability media at same pumping pressures have significant differences.(4) Grouts diffusion concentration variation was gained using image processing technology. Results show that the concentration is generally decreasing with the distance of grouting hole. Howeverthere is also local enrichment for grouts. Partition of grouts concentration strongly implies the differences in permeability and anti-seepage behavior.(5) Apatent aerostatic pressure controlled equipment for preparing mechanically grouted sand was developed, Which can be used to simulate grouting into soil mass at different depth with different pumping pressure.(6) Static high pressure triaxial test system was used to conduct permeability test in confining pressure conditions for chemically grouted sands in different grouting conditions and different grouts-sand ratio under different osmotic pressure and different confining pressures. Results suggest that hydraulic conductivity increased with the increase of osmotic pressure. However, the influence of confining pressure on hydraulic conductivity relating to specimen composition and confining pressure exhibit different characteristics. That is, in general, hydraulic conductivity reduction was induced by the confining pressure increase in chemically grouted sand containing a higher proportion of grouts. Under high confining pressure, hydraulic conductivity for chemically grouted sand increased with the increase of confining pressure due to the rupture of particles.(7) A micro-strucure classification for chemically grouted sands and a simplified pore and throat network conceptual model have been proposed based on micro structural characteristics of chemically grouted sand. Micropores in chemically grouted sand mainly consist of large and super-large pores. Retro-mercuometric curve for semi-cemented sandstone show a sudden drop, which indicates the existence of thin-neck-bottle-shaped pores and poor connectivity. The conceptual model of pore throat is a complex network system. It is clearly indicated from the conceptual model that the decisive influencing factors on permeability of chemically grouted sand include the degree of filling, cracks and fissures within particles, grouts and particle-grouts boundaries (interfacial cracks).(8) The relationship between micro-structue and permeability of chemically grouted sands is analyzed and results show that the total pore volume, pore area, porosity increase with increasing chemical grouts content, and medium pore diameter in volume and average pore diameter decrease, which result in a obvious decrease in permeability. Permeability has a directly proportiona to cavity to throat size ration, medium pores diameter in volume and average pore diameter.更多还原