A method for installing an extensible reaming self-anchoring anchor rod in a coal mass, wherein said extensible reaming self-anchoring anchor rod, comprises a simple drill bit, an anchor rod body, and a pre-tightening device;
- wherein the anchor rod body comprises a plurality of hexagonal drilling rod sections, a plurality of connecting sleeves having hexagonal connecting sections, and an extension rod section;
- wherein the plurality of hexagonal drilling rod sections are connected with each other via the plurality of hexagonal connecting sleeves, and are connected at their tail end with the extension rod section via a connecting sleeve;
- wherein each of the drilling rod sections has a first outer diameter and an axial through-hole inside of the drilling rod section, a helical structure having a second outer diameter greater than the first outer diameter outside of the drilling rod section, top threads outside of the rod section head end, a hexagonal connecting portion at a tail end or the drilling rod section, and a plurality of grouting holes communicating with the interior through-holes in a side surface of the rod section;
- wherein each of the connecting sleeves has a connecting sleeve through-hole inside of it, a hexahedral connecting portion matching the hexagonal connecting portion of the drilling rod section in the interior at one end, and a threaded connecting portion matching the top threads of the extension rod section in the interior at the other end;
- and
- wherein the pre-tightening device comprises a stop-grouting plug, a tray, and a nut that are arranged sequentially on the anchoring threads of the extension rod section;
- said method comprising the following steps:
- a. assembling a drill bit on a first drilling rod section;
- b. connecting the hexagonal connecting portion at the tail end of the first drilling rod section to the hexagonal connecting sleeve of an onboard or individual jumbolter;
- c. starting the jumbolter and using the drill bit driven by the jumbolter to drill and ream a bore in a wall of the coal mass one operation, whereupon due to the outer diameter of the drill bit being smaller than the outer diameter of the helical rod body, the helical structure accomplishes secondary reaming and self-anchoring in the coal mass;
- d. discontinuing drilling leaving a tail part of the first drilling rod section exposed outside of the coal wall, and, optionally detaching the jumbolter from the tail part of the first drilling rod section;
- e. connecting a second extension drilling rod section to the first drilling read section via the top threads with the threaded connecting portion of the connecting sleeve, mounting the jumbolter on the tail part of the second drilling section, and using the jumbolter to drive the second drilling rod section into the wall of the coal mass;
- f. repeating steps d. and e.;
- g. mounting a pre-tightening device onto the anchoring threads of the extension rod section, connecting the hexahedral portion at the tail end of the extension rod section to the jumbolter,
- h. starting the jumbolter and drilling, and discontinuing drilling and finishing mounting of the extension rod section when the tray contacts with the wall of the coal mass;
- i. repeating steps d to h to achieve desired anchor depth;
- j. removing the jumbolter and tightening a nut on the tail end of the anchor to squeeze together the coal wall and the rod body in the radial direction to inhibit crack propagation and development in the wall of the coal mass;
- k. utilizing the through-hole and the grouting holes in the anchor rod body to inject grout behind the face of the wall of the coal mass;
- and
- optionally injecting additional grout as necessary for reinforcement.