1.4. 1 research methods
The stratum is controlled by sedimentary environment, and the lithology, lithofacies and their combination characteristics of sedimentary rocks have cyclic changes in the longitudinal direction, and have thickening, thinning and even pinching out in the transverse direction, that is, sedimentary phase transition phenomenon; Under the action of late tectonic movement, sedimentary rocks are deformed and destroyed, which further complicates the structure of sedimentary rocks. The stability of coal seam roof is determined by the mechanical properties of coal seam roof rock (body) and the development degree of cracks. The mechanical properties of rock mass are controlled by the structure and combination characteristics of rock mass. Therefore, to evaluate the stability of coal seam roof, it is necessary to consider the influence of sedimentary rock combination structure on roof stability, including roof lithology change, fault structure and fracture process under mining conditions, groundwater, in-situ stress and other factors. Because of the complexity of the mechanical effect of rock mass structure, it is difficult to reveal its essence by a single means, so a comprehensive study must be made by combining indoor experimental research, theoretical analysis, field observation and theoretical calculation. This book uses the sedimentary-tectonic research method to evaluate the stability of coal seam roof, and combines computer technology to realize quantitative data processing and mapping.
1.4.2 research idea flow (figure 1.6)
See figure 1.6 for the flow of research ideas.
1.4.3 main research contents
1) analyzes and studies the sedimentary environment and sedimentary facies of this layer, including roof lithology difference, cementation type, rock formation combination mode, bedding, ancient river erosion and so on.
2) Analyze the development law of regional geological structures such as faults, joints and folds, as well as the distribution of secondary minor faults, joints and cracks and the characteristics of sliding structures. The reservoir prediction method in oil and gas exploration is combined with the characteristics of coalfield seismic data, and the seismic attribute technology and coherence/variance technology are integrated and applied to the structural interpretation of seismic data. Using three-dimensional seismic data, the small faults with a drop of about 5m in the mining area are identified, which improves the accuracy and reliability of existing seismic interpretation and provides accurate geological data for coal mine safety production.
3) The mechanical properties and strength characteristic parameters of rock mass are shown in the aspects of compressive strength, shear strength, tensile strength, bending strength and firmness of rock mass. Deformation characteristic parameters are mainly manifested in elastic modulus, Poisson's ratio, rheology and so on. The rock mass with high strength is stable relative to the rock mass with low strength, and the rock mass with small deformation is stable relative to the rock mass with large deformation.
4) Using analytic hierarchy process to evaluate the roof stability, by determining the different factors that affect the roof stability and assigning weights, using analytic hierarchy process to evaluate the roof stability in different regions and with different influencing factors.
Figure 1.6 Flow chart of research ideas
5) Using motion fuzzy clustering method to analyze roof stability.
6) Study on the method of predicting the stability of coal seam roof with multi-source information. Attribute parameters sensitive to faults and fracture development zones are extracted from 3D seismic data volume, and the geological structure and fracture development zones of coal seam are explained by combining coherent volume/variance volume technology. Through seismic inversion, the wave impedance data volume is obtained to explain the lithology of coal seam roof and fracture development zone. Using GIS platform, the prediction and evaluation model is established after the multi-source information such as three-dimensional earthquake, surface drilling, logging and mine engineering is compounded and comprehensively analyzed.