低渗透泥质弱胶结软岩高压气体致裂注浆重构改性机理研究

Traditional grouting method has poor grouting quality in low-permeability and weak-cementation argillaceous soft rock strata in the western mining area of China, which frequently brings about serious problems of large deformation and failure of roadways constructed in these strata. In order to solve this problem, a new approach of high pressure gas fracturing-grouting is proposed to reconstruct and strengthen the weak-cementation argillaceous soft rock strata in this project. A real-time system of true triaxial gas/liquid-solid coupling loading is developed to match with X-ray CT scanning system. By using this self-developed testing system, a series of visualized true triaxial mechanical experiments of gas fracturing-grouting in low-permeability and weak-cementation argillaceous soft rock specimens are carried out. Then, the evolution of fracture propagation under high pressure gas, the nonlinear infiltration and diffusion with stress-flow coupling of cement slurry after gas fracturing, and the macro-microscopic mechanical behavior of the composite specimens after fracturing-grouting treatment are systematically investigated. Based on the experimental observations, a multi-scale model capable of accurately representing gas fracturing behavior of low-permeability and weak-cementation argillaceous soft rock is established, and the governing equations of nonlinear seepage-stress coupling of cement slurry and the constitutive equations of the reconstructed specimens with fracturing-grouting treatment are deduced. Finally, a prediction and evaluation method of grouting quality and a new systematic theory for high pressure gas fracturing-grouting in low-permeability and weak-cementation argillaceous soft rock are proposed. The anticipated outcome of this project would provide new theoretical reference for solving the issue of grouting and strata control in the weak-cementation argillaceous soft rock strata in western China.

针对当前我国西部矿井开拓面临的弱胶结软岩地层渗透性低、传统注浆方法效果差、围岩大变形失稳灾害频发的重大问题，提出利用高压气体致裂注浆进行低渗透泥质弱胶结软岩重构改性的新思路。通过研制一套与CT扫描系统配套的岩石真三轴气/液-固耦合实时加载装置，系统开展一系列低渗透泥质弱胶结软岩真三轴高压气体致裂注浆过程的可视化精细力学试验，揭示高压气体作用下低渗透泥质弱胶结软岩裂隙扩展演化规律、气压致裂后浆液非线性渗透扩散特征以及“压裂-注浆”重构复合体宏细观力学行为，构建能够准确描述低渗透泥质弱胶结软岩高压气体致裂过程的多尺度力学模型，推导基于气压致裂裂隙场的浆液渗流-应力耦合非线性扩散方程以及“压裂-注浆”重构复合体本构方程，发展低渗透泥质弱胶结软岩高压气体致裂注浆改性效果预测评价方法，形成一套系统的低渗透泥质弱胶结软岩高压气体致裂注浆新理论，为解决我国西部地区弱胶结软岩地层注浆难题提供新的理论基础。

低渗透软岩地层是我国矿产资源开发以及重大交通、水利工程建设中的“卡脖子”难题之一。注浆改性技术是进行此类特殊地层脆弱工程地质力学行为调控和实现围岩稳定性与灾害控制的主要途径。但是，传统的注浆方法在低渗透软岩地层应用中普遍存在可注性低、注浆改性效果差、围岩大变形失稳灾害频发等问题。为此，本项目尝试提出与探索了低渗透软岩地层高压气体致裂注浆重构改性的新方法与新理论。项目综合采用实验室宏细观力学试验、理论分析、多场/多尺度耦合数值模拟、现场监测等相结合的研究方法，重点围绕低渗透软岩高压气体致裂裂隙扩展演化规律与机理、裂隙软岩注浆浆液渗透扩散与注浆重构体力学行为强化规律等两个关键科学问题开展了深入研究，查明了真三轴应力环境与流体压力对低渗透软岩裂隙扩展演化的影响规律，提出了改进的低渗透软岩动态脉冲气体致裂方法来增强裂隙网络复杂程度；获得了裂隙软岩注浆浆液渗透扩散规律以及注浆重构体强度力学特性与破坏模式，发现了浆-岩粘结界面微观结构特征以及界面过渡区力学性质是控制注浆重构体宏观变形与破坏行为的关键因素之一，提出了浆-岩界面过渡区结构优化和改性方法；构建了基于微裂纹演化的低渗透软岩渗流-应力-损伤耦合细观本构模型、基于裂隙非均匀分布的注浆浆液渗流模型以及基于细观力学的注浆重构体强度预测模型，提出了低渗透软岩高压气体致裂宏-细观非线性数值方法以及高压气体致裂注浆重构改性效果预测评价方法，从理论上建立了新型高压气体致裂注浆改性方法的适用条件。研究成果初步形成了低渗透软岩地层高压气体致裂注浆理论框架，丰富了我国软岩地层注浆理论与方法，为解决采矿工程、岩土工程中软岩地层注浆改性与围岩大变形控制等“卡脖子”难题提供了一条新的理论与技术途径，具有良好的推广应用前景。