Abstract: Provided is a fracturing relief method for stress concentration of remaining ore pillars in an overlying goaf, including first, performing directional fracturing on a roof to optimize the stress of the roof and reduce the source of force; secondly, performing pulse fracturing on a coal pillar to produce a crack network, weaken the stiffness of the coal pillar and reduce the bearing capacity of the coal pillar; and finally, performing pulse fracturing on a floor strata of the coal pillar to reduce the ability of transferring stress concentration thereof. A drilling machine is used for separately constructing fracturing drill holes in a roadway to a set depth at an interval in a direction oblique to the coal pillar in an upper goaf. The roof, the coal pillar and the floor can be fractured by an oblique fracturing hole in a sublevel retreating manner. The position of the directional fracturing of the roof is approximately 1 m above the middle of a main roof above the coal pillar.

Abstract: Provided is a fracturing relief method for stress concentration of remaining ore pillars in an overlying goaf, including first, performing directional fracturing on a roof to optimize the stress of the roof and reduce the source of force; secondly, performing pulse fracturing on a coal pillar to produce a crack network, weaken the stiffness of the coal pillar and reduce the bearing capacity of the coal pillar; and finally, performing pulse fracturing on a floor strata of the coal pillar to reduce the ability of transferring stress concentration thereof. A drilling machine is used for separately constructing fracturing drill holes in a roadway to a set depth at an interval in a direction oblique to the coal pillar in an upper goaf. The roof, the coal pillar and the floor can be fractured by an oblique fracturing hole in a sublevel retreating manner. The position of the directional fracturing of the roof is approximately 1 m above the middle of a main roof above the coal pillar.

Abstract: A stress-transfer method in tunnel with high ground pressure based on fracturing ring. According to the stress source of the tunnel, fracturing by drilling holes to form artificial weaken zones in surrounding rocks, that's named fracturing ring. The fracturing ring is the weaken zone with some width, whose inner boundary is the protective circle. The fracturing ring with small width is called the cutting and interruption circle and the cutting or interruption arc. The radius of the protective circle is determined by setting a certain width of safety coal pillar barriers at the edge of a support body. The radius of the fracturing ring is determined by the surrounding rock structure and the stress conditions as well as the construction technology. Usually, the higher the stress, the wider the radius of the fracturing ring. The cutting and interruption circle or arc could cut off all of the targeted rock which transmits the stress.

Abstract: A method for determining a segmentation threshold of a digital image of a rock-soil material is disclosed. The method comprises the following steps: S1: acquiring a gray-level histogram curve of an SEM image of the rock-soil material; S2: determining a value range of a segmentation threshold T according to the gray-level histogram curve; S3: acquiring second derivatives of the gray-level histogram curve; and S4: determining the segmentation threshold T according to the second derivatives of the gray-level histogram curve and the value range of the segmentation threshold T. The present invention can rapidly and accurately determine the segmentation threshold of the digital image of the rock-soil material, and accurately distinguish a pore or fissure structure from a surface soil skeleton structure of the rock-soil material in the digital image.

Abstract: A long-distance drilling and hydrofracturing integrated device and method in underground mine are provided. The device includes a drill bit, a hydrofracturing rod, an anti-impact rod, a hole sealing rod, a high-pressure sealed drill rod and a crawler drill rod feeder sequentially connected end to end. In the method, the drill rod and the hydrofracturing rod are delivered to a designated position while drilling, the drill rod does not need to be taken out, only a crawler drill needs to be improved, high-pressure water holes are added to the rod feeder, and the high-pressure water enters the drill rod from the high-pressure water holes and reaches the hydrofracturing portion. When the hydrofracturing is completed, the drill rod is withdrawn by the crawler drill, reaches another hydrofracturing point, and a hole sealing operation can also be performed.

Abstract: A long-distance drilling and hydrofracturing integrated device and method in underground mine are provided. The device includes a drill bit, a hydrofracturing rod, an anti-impact rod, a hole sealing rod, a high-pressure sealed drill rod and a crawler drill rod feeder sequentially connected end to end. In the method, the drill rod and the hydrofracturing rod are delivered to a designated position while drilling, the drill rod does not need to be taken out, only a crawler drill needs to be improved, high-pressure water holes are added to the rod feeder, and the high-pressure water enters the drill rod from the high-pressure water holes and reaches the hydrofracturing portion. When the hydrofracturing is completed, the drill rod is withdrawn by the crawler drill, reaches another hydrofracturing point, and a hole sealing operation can also be performed.

Abstract: A stress-transfer method in tunnel with high ground pressure based on fracturing ring. According to the stress source of the tunnel, fracturing by drilling holes to form artificial weaken zones in surrounding rocks, that's named fracturing ring. The fracturing ring is the weaken zone with some width, whose inner boundary is the protective circle. The fracturing ring with small width is called the cutting and interruption circle and the cutting or interruption arc. The radius of the protective circle is determined by setting a certain width of safety coal pillar barriers at the edge of a support body. The radius of the fracturing ring is determined by the surrounding rock structure and the stress conditions as well as the construction technology. Usually, the higher the stress, the wider the radius of the fracturing ring. The cutting and interruption circle or arc could cut off all of the targeted rock which transmits the stress.