The object of the invention is a multichamber structural element manufacturing method which for forming a multichamber structural element with chamber profiles (1) extending radially from the center defined by the connection of the chamber profiles (1) comprises the following steps: at least three chamber profile preforms (2) are provided, wherein each chamber profile preform (2) comprises two walls (3) made of a sheet of metal material and arranged with respect to each other in substantially parallel planes with a gap retained between them, wherein the edges of the individual walls (3) converge, and wherein a valve element (6) is arranged on at least one wall (3); the unconnected wall (3) edges of each of the chamber profile preforms (2) are sealed with a seal (5) for forming a closed hermetic empty inner space of the chamber profile preform (2); a fluid under pressure is introduced through the valve element (6) into the inner space of the chamber profile preform (2) for forming a deformed chamber profile (1), at least three chamber profile preforms (2) or chamber profiles (1) are connected in the area of the corresponding inner edges of the chamber profile preform (2) or the chamber profile (1), proximal with respect to the connection axis (4), along at least part of the inner edges. The object of the invention is also a multichamber structural element.

An internally injected replacement support room-type coal pillar recovery method is provided. During the recovery, the room-type coal pillars with an aspect ratio greater than 0.6 are divided into two parts: reserved coal pillars and pre-mined coal pillars. After the mining of the pre-mined coal pillars, a cemented filling material is injected into a goaf surrounded by the reserved coal pillars, and is stabilized to replace the coal pillars for support, and the reserved coal pillars are recovered. A mechanical model of the reserved coal pillars in a support overburden stage is established based on the Winkler beam theory, to obtain displacement and stress conditions of a roof of the reserved coal pillar in a support stage. A theoretical reserve-width of the reserved coal pillars is obtained according to a first strength theory of the roof and a criterion of ultimate strength of the reserved coal pillars.

An internally injected replacement support room-type coal pillar recovery method is provided. During the recovery, the room-type coal pillars with an aspect ratio greater than 0.6 are divided into two parts: reserved coal pillars and pre-mined coal pillars. After the mining of the pre-mined coal pillars, a cemented filling material is injected into a goaf surrounded by the reserved coal pillars, and is stabilized to replace the coal pillars for support, and the reserved coal pillars are recovered. A mechanical model of the reserved coal pillars in a support overburden stage is established based on the Winkler beam theory, to obtain displacement and stress conditions of a roof of the reserved coal pillar in a support stage. A theoretical reserve-width of the reserved coal pillars is obtained according to a first strength theory of the roof and a criterion of ultimate strength of the reserved coal pillars.

A underground support includes a first row of panels, and a second row of panels configured to be secured to the first series of panels to define an interior space for receiving construction aggregate or concrete. Each panel of the first row of panels and the second row of panels includes a body having a top edge, a bottom edge positioned opposite from the top edge, a left edge, and a right edge positioned opposite from the left edge, with the top edges of the panels of the first row of panels configured to abut the bottom edges of the panels of the second row of panels.

A underground support includes a first row of panels, and a second row of panels configured to be secured to the first series of panels to define an interior space for receiving construction aggregate or concrete. Each panel of the first row of panels and the second row of panels includes a body having a top edge, a bottom edge positioned opposite from the top edge, a left edge, and a right edge positioned opposite from the left edge, with the top edges of the panels of the first row of panels configured to abut the bottom edges of the panels of the second row of panels.

A plate for cribbing stacks having a top surface and a bottom surface, first, second, third, and fourth side surfaces connecting the top and bottom surfaces; a first level attached to the first side surface; and a second level attached to the second side surface, the first and second side surfaces being in a non-parallel relationship; and wherein the top and bottom surfaces and the first, second, third, and fourth side surfaces are arranged so that the first and second levels indicate when the plate is horizontal.

A plate for cribbing stacks having a top surface and a bottom surface, first, second, third, and fourth side surfaces connecting the top and bottom surfaces; a first level attached to the first side surface; and a second level attached to the second side surface, the first and second side surfaces being in a non-parallel relationship; and wherein the top and bottom surfaces and the first, second, third, and fourth side surfaces are arranged so that the first and second levels indicate when the plate is horizontal.

An equipment system for a self-retaining mining method mainly comprises a transition support, an end support, a following support, and a fast-retracting support. Working face gateroads do not need to advance in mining, and a coal mining machine may be used to cut a neat coal wall at the end of a district. The entry rib is automatically formed after roof caving, thus forming a gateroad in a re-mining process. The coal mining machine is under digital control when its end cuts the coal, automatically enabling the end to laterally cut the coal wall to form a vertical straight line, which is used as the entry rib of the gateroad. A scrapper conveyor works in coordination with an arc-shaped coal grabbing plate of the coal mining machine to clean up float coal at the end as much as possible.

A system or method for a structural mine roof support includes a roof support apparatus that includes a cylindrical cladding defining a hollow interior, a plurality of bamboo sections disposed in the hollow interior and coaxial with an axis of the cylinder. Also, a roof support apparatus with a cylindrical cladding defining a hollow interior, a plurality of bamboo sections disposed in the hollow interior and coaxial with an axis of the cylinder, and voids between adjacent bamboo sections, the voids being injected with a filler material, e.g., polyurethane foam, to maintain axial positioning of the bamboo sections when under load. The support apparatus configured to load and to yield in a predetermined fashion to control a mine roof from sudden failure.