Research On The Relationship Between Two-Leg Sublevel Caving Shield Support And Surrounding Rocks And Adaptability

With the maturity and popularization of fully-mechanized sublevel caving technique, fully mechanized sublevel caving face begins to develop towards automation and informationization. Two-leg sublevel caving shield is a new type hydraulic support and has been developed according to these development requirements. The new support has high support ability and good roof control effect in practice, and further improves the technology level of mechanized sublevel caving technique in China.Using analog simulation method that gives a research on dynamic function law of two-leg sublevel caving shield and surrounding rocks, it has been analyzed to the influence of top-coal hardness and main structure and parameters of the support on the function process. The study shows that in fully mechanized sublevel caving face the movement of top-coal has characteristics of "two-zone destabilization", its dynamic developing process influences the stability of the relationship between two-leg sublevel caving shield and surrounding rocks. Thus, two-zone destabilization which influences roof control effect of the support is the key factor. Increasing the working resistance of support and reducing the beam pre-to-post ratio can increase the stability of the relationship between support and surrounding rocks, and improve the roof control quality in tip-to-face area.The dissertation has analyzed the influence of the two-leg sublevel caving shield on roof control effect in tip-to-face area after the beam pre-to-post ratio, working resistance and the shield beam pressure have been simulated in ABQUS. After reducing pre-to-post ratio of the beam, increasing working resistance of the balance jack and/or pressure of the shield beam, the support resistance of the prop has been increased, the tensile stress has been reduced and shear stress in top-coal of tip-to-face has been increased. As a result, the stability of top-coal has been increased and roof sinkage has been reduced in tip-to-face area. According to the preceding result, the control effect of support horizontal resistance on roof fall of tip-to-face has further been studied using UDEC3.0.The study shows that hard top-coal of tip-to-face is mainly destroyed by tension, while the soft coal is mainly destroyed by shear. Support horizontal force can soften tension degree and increase shear capability in of top-coal in tip-to-face area, and prevent the development of the end caving arch. Therefore, the stability of top-coal in tip-to-face area can be maintained.The rotation deformation relationship between immediate roof above medium stability and main roof was studied by analog and numerical simulation method, and the determination method of turning angle of the immediate roof was put forward. Through making immediate roof the upper boundary of top-coal and support system, the mechanical model was constructed which reflects the core elements of the relationship between the two-leg sublevel caving shield and surrounding rocks system. According to the mechanical model, the determination method of the working resistance of the support was analyzed and the computational formula of the working resistance was induced.According to the analog and numerical simulation analysis result, the mechanical process of "two-zone destabilization" of top-coal and its influence on support applicability have been analyzed. The dissertation defines the determination factor for support applicability and induces the determination formula. By in-situ measurement the influence of support state on support applicability has been analyzed. The result shows that the influence of support on roof fall of tip-to-face gradually visualizes and enhances with the increase of upward or downward angle of the top beam, by which giving the control index of support state.The practical case has been studied in two-leg sublevel caving shield. The result of practical case showed the shape status and roof of tip-to-face were stable which met expectation effects. The efficiency of support is better than before. Therefore, this type of support can improve the efficiency of production and reliability of working face. However, when the working face enters into the fault zone, it shows that it is difficult to control the support, which could cause the roof fallen of tip-to-face. Therefore, it is necessary to select the appropriate support type according to geological condition of the top-coal in order to make most of its advantage and increase the production efficiency.The dissertation has 209 figures, 19 tables and 139 references including 24 foreign references.