Study Of Double-layer Rock Beams Structure

A significant beam structure exists in the stope overlying stratified rock. So the analysis of stresses and deformation failure of the beam and composite structure is the foundation of research of overlying strata's structure.By similar materials simulation experiment and theoretical analysis, rock beam's breaking rule under deadweight and the mechanical interaction between rock beams in different combination conditions were studied. The main contents are listed below. Constructed the system of rock beam similar material simulation experiment. Selected the appropriate materials and determined the ratio of the experimental. Measured the physical and mechanical parameters of the specimen. Conducted breaking experiments of single rock beam with different materials and analyze the experimental results by theory. Conducted breaking experiments of double-layer rock beams in different combination conditions and analyzed the experimental results by theory. Conducted numerical simulation about rock beams'breaking experiments.The results got from single rock beams'breaking experiment agreed with the theoretical results, indicated that rock specimens made from selected material lined with the requirements of Mechanics of Materials, analyze the experiment results of selected material by theory of mechanics of materials was suitable.Through double-layer rock beams'breaking experiment and theoretical analysis, such conclusions were got as below. The interlaminar shear strength determine the composite structure's formation. In the combination of top-hard-bottom-soft with no cementation between two layers, there is no mechanical interaction between rock beams, the two layers move respectively and have the same broken span as single beam. In the combination of top-hard-bottom-soft with weak cementation between two layers, shear stress at the interface is less than the interlaminar shear strength within a certain span, the two layers combined to a composite structure and move together, surpass the span, shear stress at the interface become greater than the interlaminar shear strength, the composite structure is broken, the two layers separate from each other and move respectively until broken and have the same broken span as single beam. In the combination of top-hard-bottom-soft with strong cementation between two layers, the two layers combined to a composite structure and move together till broken, the broken span is affected by mechanical properties of specimens. In the combination of top-soft-bottom-hard, the top layer load to the bottom, but the load is a part not all of the deadweight of the top layer, it is determined by thickness, density and elastic modulus of the two layers. Mechanical formulas are concluded for each condition to introduce mechanics interaction between rock beams.By FLAC^3D numerical simulation software, deformation and failure law of single rock beam and the mechanics relationship between rock beams were simulated, numerical simulation results of rock specimen breaking experiment are the same as similar material simulation results.