Numerical study on the formation of pressure arch in bolted gravel plate

Pressure arches form in and affect the stability of fractured rock reinforced by rockbolts; however, no direct indicator of pressure arch presently exists. A sophisticated model was developed using the 3D particle flow code (PFC3D) to perform gravel bolting tests that allow pressure arches visualization to investigate their formation and influencing factors. The results suggested that a pressure arch can be formed in bolted gravel through interlocking between gravel particles. The whole load of the gravel contained in the filling box is carried by the pressure arch. The formation conditions of a pressure arch are obtained. The rockbolt spacing should be less than 2.5 times the average gravel size. The thickness of the gravel pack should not be less than 2.5 times the rockbolt spacing. Besides, the thickness of the gravel pack should be similar to 0.6 times the side length of the gravel pack. The plate size should not be less than 0.6 times the rockbolt spacing. The formation of a pressure arch is insensitive to the rockbolt elastic modulus. The specific function of rockbolts in bolted gravel is to help form a pressure arch by exerting supporting and surface-retaining effects to stabilize the gravel particles below the pressure arch. Some suggestions were made for rockbolt support in extremely fractured rock in mining roadways.