金属矿海底基岩开采裂隙分形演化与突水混沌孕育机制

Inside the vast continental bedrock shelf along the coastline, there are abundant mineral resources, which provide a new direction for the sustainable development of mining industry in our country. But the conditions of undersea metal deposit are complicated, such as oblique or steep inclined ore body, effected by the upper water overlying strata of seabed, years mining in the same area, and constantly disturbing to the above strata. Then, in the mining process of undersea deposit, the laws of subsidence, deformation, failure of rock and water inrush of inoculation are very complex, and it is necessary to study the seepage evolution and water inrush mechanism during undersea mining in metal mine. Therefore, according to the technical conditions of undersea metal deposit, and through the research means, such as exploiting the similar simulation test platform for undersea mining, experimenting with the mean of similar simulation, analyzing the fractal characteristics of crack evolution, calculating with method of fluid-solid coupling, constructing the reforming cluster model of rock failure from micro-cracks extension to macroscopic rupture, establishing the chaotic modle of water-inrush evolution, and so forth, the subsidence characteristics of seabed rocks, crack expansion, and the cumulative damage characteristics are revealed. Meanwhile, the seepage evolutions of seawater and energy release of bedrock are researched, and the chaotic mechanisms of water inrush are explored during undersea mining. As well as, the critical depth of water inrush and the reasonably safe cover thickness of seabed can be obtained, and the water-inrush criterions can be established, so the theoretical basis of safely mining undersea deposits can be provided.

沿海岸海底基岩内矿产资源丰富，为我国矿业可持续发展提供了新的方向。但海底金属矿床赋存条件复杂，多为倾斜或急倾斜厚大矿体，多年在同一区域开采，上覆岩层处于持续不停的开采扰动过程中，并受覆岩上部海水影响，海底基岩矿床开采过程中的岩层沉降、裂隙渗流演化与突水孕育机制非常复杂。为此，本项目针对海底金属矿床赋存条件，通过海底开采模拟试验平台开发、相似模拟试验、裂隙演化分形特征分析、流固耦合数值计算、海底岩层裂隙从微观扩展至宏观破裂重整化群力学模型构建、岩层孕育突水混沌理论模型建立等手段，揭示金属矿海底基岩开采岩层沉降、裂隙扩张与累积损伤特性，研究海底开采岩层渗流演化与能量耗散规律，探索海底基岩开采突水混沌孕育机制，得出岩层突水的临界深度，确定金属矿海底开采合理安全隔层厚度，建立海底开采岩层突水判据，为海底金属矿床安全开采提供理论基础。

我国陆地浅部金属资源开采殆尽，海基矿产资源的开发将成为我国经济发展新的增长点，具有重要的战略意义。海底金属矿开采岩层破坏具有突发性、难以预测等特征，海底金属矿开采相关理论研究处于起步阶段。为此，项目针对金属矿海底基岩开采特征，开发了金属矿海底开采相似模拟试验平台，建立了海底开采流固耦合数值模型，构建了岩层裂隙演化与渗流突水重整化群力学模型，探索了岩层裂隙扩展与突水混沌孕育机制，确定了海底基岩开采安全隔层厚度确定，推演获得了海底开采岩层突水判据。主要创新研究成果如下：.(1)研究金属矿海底开采岩层裂隙分形演化机理，获得海底金属矿开采岩层破坏裂隙分形维数演化的四个阶段：裂隙孕育阶段、裂隙发育阶段、裂隙扩展阶段和破裂失稳阶段。海底矿床岩石力学试验得出，岩石破坏裂隙和声发射分形维数分别为1.4482和1.4693，两者相近；海底开采相似模拟试验揭示，随着开挖进行，岩层声发射分形维数逐渐增大，顶板岩层安全厚度小于40m后，声发射分形维数开始降低，呈现突水征兆；三山岛金矿海底开采岩层裂隙钻孔摄像和岩层变形多点位移计监测结果显示，其分形维数分别为1.2328和1.2685，岩层变形与裂隙扩展均处于裂隙发育的第二阶段，未达到破坏失稳的第四阶段。.(2)三山岛金矿海底开采岩层变形监测数据研究显示，海底金属矿开采岩层变形具有混沌特性，离开采区域越近，动力系统关联维数D越大，不同高度岩层变形过程表现出不同的混沌动力学特性。.(3)用3DEC流固耦合离散元计算程序，建立了金属矿海底开采岩层节理裂隙渗流演化数值模拟模型，分析了海底金属矿开采节理摩擦功和塑性应变能，揭示了海底金属矿开采岩层释放总能量。.(4)建立了金属矿海底开采岩层裂隙延伸扩展的Phase2数值模拟模型，用断裂力学分析，获得海底金属矿开采裂隙起裂条件与突水特征呈现的安全判踞。.(5)用混沌理论重整化群原理，揭示了岩层裂隙演化特征，得到海底金属矿开采裂隙不大规模扩展的安全系数为1.687，构建了金属矿海底开采岩层裂纹发育模型。