Machine Embroidery Designs,Embroidery Sewing Machine,Hat Embroidery Machine,Computer Embroidery Designs Ningbo World Wide Electric techonology CO.,Ltd , https://www.nbmy-sewmachine.com
If the roof being studied is at risk of bending and delamination, it is effective to support with the drill pipe. The amount of support can be calculated by beam or plate theory, and the anchor point of the design anchor should be placed on a solid rock with less deflection. If prestressed anchoring is used, the effect is better. At this time, prestressing can maintain sufficient positive pressure and interlaminar shear resistance between several layers, thereby increasing the stiffness and strength of the composite beam and increasing stability.
If the rock formation itself is impervious to water and there is pressure water or gas between the layers, then the bending and separation phenomena may aggravate and lurk the danger of water and gas suddenly ejecting. Pre-drilling drainage relief can increase the stability of the top (bottom) plate.
Bending and separation of layered rock mass
If the roof of the roadway is composed of a thin layer of rock with weak bonding force, when the width of the excavation body is large enough, the top plate may be significantly bent or even broken and collapsed. If the bending deformation develops upward, it will cause the multilayer to bend, the separation layer and the multilayer to collapse. This situation is common when mining layered deposits.