Experimental study on static and dynamic mechanical properties of composite structure of anchor plate and cushion

When the bolt support system is subjected to the impact load,the impact load causes the instantaneous increase of the force between surrounding rock and supporting plate,resulting in the overload bending and tearing of supporting plate,and the fracture and collapse of surrounding rock in the contact area. Using the method of laboratory test,the static and dynamic load test bench for the composite structure of supporting plate and cushion is built. The static and dynamic load mechanical properties of five composite structures are tested respectively. The static load displacement curve,impact force time history curve and strain time history curve of the composite structure are obtained,and the mechanical response law of the composite structure under different impact loads is studied. The effects of cushion material and thickness on the impact resistance of composite structure are analyzed. The test results show that the cushion has a certain effect on the deformation shape of the supporting plate under static load. The high stiffness of cushion will increase the deformation of supporting plate and reduce the peak load of the composite structure. The thickness of cushion mainly affects the deformation capacity of the composite structure and has little effect on its bearing capacity. The peak value of the impact force of supporting plate is basically the same under different impact energy,the supporting plate has reached the peak bearing capacity under low impact energy,and the peak bearing capacity of dynamic load is basically the same as the maximum bearing capacity of static load. Under different impact energy,the deformation of supporting plate is obviously different. The deformation of the upper diagonal of supporting plate is relatively small,while the deformation of the upper midline of supporting plate is relatively large. The cushion can reduce the impact force peak value of the composite structure. Compared with the bolt support system without cushion,the impact force peak value of the composite structure increased by 21.45%,17.55%,25.40% and 2.80% respectively when the pine,rubber cushion,waste belt and foam aluminum cushion were used. The impact force time increased by 41.94%,24.52%,47.74% and 65.16% respectively. The cushion could reduce the impact force peak,prolong the impact time and effectively absorb the impact kinetic energy. The cushion thickness has a great impact on the impact force and strain of the composite structure. The greater the cushion thickness,the more impact kinetic energy absorbed,the smaller the impact force peak value,the longer the impact force action time,and the better the cushion performance. The appropriate cushion material and thickness can effectively reduce the damage effect of impact load on the supporting plate structure. Overall,compared with the use of pallets alone,the four cushions have a certain degree of energy absorption and impact reduction. However,different cushions have different effects on the impact resistance of composite structures,and the energy absorbing effect of cushion is superior to inferior foam aluminum,pine,worn belts and rubber mats.