Based on a large number of field investigations and the analysis of the "analogous hyperbolic" overall movement model proposed by the author, this paper further extends it to three-dimensional space, and proposes a full-space "analogous hyperboloid"three-dimensional movement model of the mining strata.There are two types of hyperboloids, "quasi-single-leaf"and "quasi-double-leaf", which can approximately describe the three-dimensional movement and surface subsidence characteristics of full-space mining strata under different lithological conditions.The "analogous single leaf hyperboloid" model is a horizontal moving boundary model of the spatial rock layer, which is implicit in the thick loose layer overlying rock; the "analogous double leaf hyperboloid" model is the vertical movement of the spatial surface subsidence and the overlying fissure arch and caving arch.The boundary models are approximately symmetrical with the "origin" in the main key layer, and are embodied in external forms such as surface subsidence under mining disturbance and arch caving of the surrounding rock in the stope. Through theoretical analysis, similar model test and 3DEC numerical simulation, this paper deduces and proves in detail the "analogous hyperboloid" model of spatially mined rock strata movement and surface subsidence under the condition of near-horizontal coal seam mining in thick loose layers.At the same time, this study analyzed the composition conditions, influencing factors and overall migration law of the co-asymptotic conical surface "analogous hyperboloid" model.Results show that under the condition of near-horizontal coal seam mining with thin bedrock and thick loose layer, the "quasi-hyperboloid" theoretical model is in good alignment with the 3DEC simulation results, indicating that the overlying rock migration and surface subsidence in space mining are "analogous hyperboloid" feature.

Based on the fracture mechanics theory of the isotropic Hoek-Brown strength criterion, this paper established the initiation conditions of the bifurcated microcrack along bedding which begins with the meso-fracture mechanism of laminated rocks. Then the author substituted the critical angle which indicates that the initial crack most likely causes the fracture of the rock into above established conditions and derived the anisotropy expression of the parameter m₁ for the weak plane of bedding leading to the crack deflection. Through introducing the correction coefficient for the mixed fracture of the rock along the bedding and the matrix, this paper obtained the anisotropic modified model of Hoek-Brown strength criterion. Compared with the established anisotropic Hoek-Brown model and shale triaxial test results, the validity of the model was proved. The modified model inherits the fracture mechanics analysis of the isotropic Hoek-Brown strength criterion for the selection of rock failure characteristic quantity, and reflects the microscopic failure mechanism of the rock, also considers the effect of bedding anisotropy. The parameters in the modified criterion have a clear physical meaning. The parameter m in the model is related to the angle of the bedding plane, the tensile strength, compressive strength and friction coefficient of bedding and matrix. The change in the friction coefficient of the bedding plane will cause the position of the minimum value of m and the rock strength characteristics changed.

Rock heterogeneity (such as mineral inclusions, micro-cracks, micro-voids and other microstructures) significantly affects its nonlinear mechanical behavior and failure process. This paper utilizes the Fast Fourier transform-based(FFT) numerical method which does not require meshing of complex microstructure but directly obtains the microstructure of heterogeneous materials through the pixels of the image. In addition, the method can be naturally combined with digital image processing (DIP). An actual-microstructure-based FFT method is thereby developed to simulate the elastoplastic behavior of the heterogeneous rocks under external load. The influence of microstructure on the nonlinear behavior is discussed as well as the internal relationship between the microstructure and the macroscopic mechanical properties. The results show that the real-microstructure-based FFT method can well predict the nonlinear behavior before and after the peak strength of the rocks under different depths and confining pressures. The shape, size and distribution of microstructure directly determine the distribution of stress field in clay rock. The actual-microstructure-based FFT method proposed in this paper can reasonably consider the rock heterogeneity, and provides an important tool for studying the influence of the rock microstructure characteristics on the nonlinear mechanical behavior.

In mining engineering, the multi-scale failure behavior of surrounding rock under the complex stress environment is a fundamental influencing factor of disasters. This paper systematically summarizes our recent ten years' research progress of rock multi-scale failure mechanics, including macro/meso rock failure mechanics, roadway surrounding rock control and rock strata movement. In terms of laboratory research scale of rock mechanics, the propagation process of rock meso-crack under the thermal-mechanical coupling effect was studied by using the SEM test system, which reveals the meso-fracture mechanism of rock. The macro failure and mechanical properties of rock, coal and coal-rock combined body were experimentally investigated under different loading and unloading conditions. A non-linear model of coal and rock mass macro failure was established. In terms of roadway failure scale, the stress gradient failure mechanism of the surrounding rock of roadway was revealed, the theory of uniform strength support in deep roadway was established, which guides the direction of roadway support. Then the full-space collaborative control technology of roadway was proposed and applied on site. In terms of rock fracture mechanics and movement scale, the evolution of roof fracture modes of different thicknesses was studied by experiments, and four roof fracture modes and fracture mode partitions were obtained. Based on the theory of key strata, the analogous hyperbola model and the inner and outer analogous hyperbola model of overburden movement caused by mining were proposed. The evolution of the analogous hyperbola model with the variation of the key layer position and the dip angle of coal seam was analyzed. The above results will provide theoretical and technical support for the prevention and control of coal mining disasters in our country.

In this paper, a large number of coal mine roadway failure cases are investigated, and 6 types and 15 typical failure forms are extracted.The mechanical characteristics and stress distribution of surrounding rock of typical roadway shapes such as circular and rectangular are analyzed.At present, the technology of high-strength prestressed bolt support, full space collaborative support and concrete filled steel tube support have shown certain advantages in deep surrounding rock control.Furthermore, based on the gradient failure mechanism of roadway surrounding rock and the uniform strength beam support model of rectangular roadway proposed by the author's team, the conceptual model of uniform strength support control theory for surrounding rock of deep roadway is put forward.According to the stress characteristics of roadway surrounding rock, the stress state of surrounding rock can be effectively adjusted by means of slotting and pressure relief, grouting, bolt (cable)support and passive support with concrete filled steel tube.The goal that the surrounding rock at different locations can reach the equivalent stress intensity state which is safe and matches the ground stress ratio can be achieved, and the ideal state that the stress distribution tends to be uniform and the plastic zone range of surrounding rock is similar can be obtained.The supporting strength of roadway with different buried depth and different section shape is calculated, and the calculation formula of support strength required by uniform strength is given.The stress changes of surrounding rock of circular and rectangular roadways before and after uniform strength support are simulated, and the stress field of surrounding rock can be significantly improved after uniform strength support is verified.Uniform strength support control model provide theoretical and practical guidance for surrounding rock control of deep roadway to a certain extent.

Mine filling and tunnel spraying projects pose high requirements on the rheological properties of cement-based materials. The types, conditions of fine sands and the exposed environment have significant effects on the rheological properties. In this light, this paper uses coal gangue sand instead of quartz sand as the fine aggregate of cement-based material and investigates the effect of temperature and aggregate prewetting on the rheological properties of mortar and its mechanism. Results show that the shear stress-shear rate relationship of coal gangue mortar conforms to the characteristics of Herschel-Bulkley (H-B) model, with higher rheological index (higher than 1) and higher consistency than that of quartz sand mortar. The apparent viscosity of coal gangue mortar decreases with increasing temperature, but the effect of aggregate prewetting is not significant. The yield stress of coal gangue mortar at 30 ℃ is 2.99 Pa, 1.45 times higher than that at 10 ℃, and 2.13 times higher after prewetting. The thixotropic ring area of coal gangue mortar is higher than that of quartz sand mortar, and the thixotropic ring area of pre-wetting coal gangue mortar is 398.4 Pa/s, while that of dry coal gangue mortar is 283.3 Pa/s. The obtained results are expected to provide evidence for the rational utilization of coal gangue sand and the design and preparation of rheological materials served in complex environment.