Anchoring method utilizing self-drilling and self-anchoring extendable anchor rod applicable to soft and weak coal rocks

Abstract

The present invention provides a self-drilling and self-anchoring extendable anchor rod applicable to soft and weak coal rocks and an anchoring method thereof, which are suitable for supporting soft and weak coal rock mass in roadways.

Claims

1. An anchoring method utilizing a self-drilling and self-anchoring extendable anchor rod applicable to soft and weak coal rocks, comprising: drilling a hole at a designed position to be from - of a designed hole length; selecting an intermediate rod body having a head, a body, and a tail end; wherein the head and the tail end have male threading and the body has external threading; selecting a connecting sleeve having internal female threading and external threading; selecting a tail rod body having a head, a body, and a tail end; wherein the head and the tail end have male threading and the body has external threading; selecting a drill bit, having an aperture with female threading and engaging the male threading of the intermediate rod body with the female threading, thereby inserting the head end of the intermediate rod body into the aperture; connecting a drilling apparatus by mounting the tail end of the intermediate rod body into the drilling apparatus, and drilling into the hole; disconnecting the drilling apparatus, extending the intermediate rod body into the hole by combining a plurality of connecting sleeves to connect a plurality of intermediate rod bodies, connecting the drilling apparatus after each sleeve and intermediate rod body is attached, drilling into the hole, and repeating until the plurality of intermediate rod bodies and the plurality of sleeves extends to near the designed hole length; connecting the tail rod body to a last connecting sleeve of the plurality of connecting sleeves, the plurality of intermediate rod bodies, and the drill bit to form a combined rod body; connecting the tail rod body to the drilling apparatus to drill the combined rod body into the hole until the designed hole length is reached and the exposed length of tail rod body is from 30 mm-150 mm; the external threading on the plurality of intermediate rod bodies and the external threading on the plurality of sleeves having a limited dust discharge function within the hole and promoting a frictional anchoring force at the drill bit end, promoting hole enclosure wall collapse, engaging with enclosure wall material and dust within the hole, and resulting in a radial anchoring force axially along the combined rod body; fitting a tightening device on the tail rod body, the tightening device comprising a tapered rubber plug, a tray, and a nut; wherein the tapered rubber plug, the tray, and the nut are fitted sequentially over tail end of the tail rod body and the nut undergoes a first tightening; performing a second tightening on the nut from 1 hour to 2 hours after the first tightening, to mitigate stress relaxation of the combined rod body; using a torque wrench to measure tension on the nut from 12 to 24 hours after the first tightening and if tension is below a threshold tension, performing a third tightening to meet the threshold tension.

2. The method of claim 1, wherein the diameter of a drill bit in the initial drilling process exceeds the diameter of the combined rod body by 1 mm-10 mm.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic assembly diagram of the anchor rod of the present invention;

(2) FIG. 2 is a structural diagram of the drill bit of the present invention;

(3) FIG. 3 is a structural diagram of the intermediate rod bodies of the present invention;

(4) FIG. 4 is a structural diagram of the connecting sleeve of the present invention;

(5) FIG. 5 is a structural diagram of the tail rod body of the present invention;

(6) FIG. 6 is a structural diagram of the tapered rubber plug of the present invention;

(7) FIG. 7 is a schematic diagram of the drilled hole of the present invention.

(8) In the figures: 1drill bit; 2intermediate rod bodies; 3connecting sleeve; 4tail rod body; 5tapered rubber plug; 6tray; 7nut; 8grouting hole; 9connecting male thread; 10hexagonal connector; 11female thread of drill bit; 12connecting female thread; 13tightening thread; 14female thread of rubber plug.

EMBODIMENTS

(9) Hereunder the present invention will be further detailed with reference to the accompanying drawings and examples.

(10) The mechanical structure of the self-drilling and self-anchoring extendable anchor rod is described as follows.

(11) As shown in FIG. 1, the self-drilling and self-anchoring extendable anchor rod applicable to soft and weak coal rocks of the present invention comprises a drill bit 1, a combined rod body, and a tightening device; the combined rod body comprises a plurality of intermediate rod bodies 2, a plurality of connecting sleeves 3, and a tail rod body 4, wherein, the plurality of intermediate rod bodies 2 are connected together via the plurality of connecting sleeves 3, the tail end of the last intermediate rod body 2 is connected to the tail rod body 4 via a connecting sleeve 3. FIG. 1 shows the situation in which one intermediate rod body 2 is used. The tightening device is connected to the tail rod body 4 through a threaded connection, and the tightening device comprises a tapered rubber plug 5, a tray 6 and a nut 7 arranged on the tail rod body sequentially.

(12) FIG. 2 is a structural diagram of the drill bit 1. Connecting female threads 12 are arranged within drill bit 1.

(13) As shown in FIGS. 3 and 5, each of the intermediate rod bodies 2 has connecting male threads 9 on its head end and a composite joint consisting of connecting male threads 9 and a hexagonal connector 10 on its tail end, and the tail rod body 4 has connecting male threads 9 on its head end and tightening threads 13 on its tail end; the intermediate rod bodies 2 and the tail rod body 4 have threading (e.g. steel screw threading) on their surfaces, and are hollow in the axial direction and have a grouting hole 8 respectively; the connecting male threads 9 on the top end and the bottom end of the intermediate rod bodies 2 have a length of 10150 mm, the hexagonal connector 10 has a length of 1080 mm, the tightening threads 13 have a length of 30150 mm, and the tail rod body 4 has a length of 4003,500 mm.

(14) As shown in FIG. 4, the connecting sleeve 3 has connecting female threads 12 matching the intermediate rod body 2, the connecting sleeve 3 has a length of 40160 mm, and the diameter of the connecting sleeve 3 is 105130% of the diameter of the intermediate rod body 2.

(15) As shown in FIG. 6, the tapered rubber plug 5 has female threads of rubber plug 14 on the inside to increase the friction with the tail rod body 4.

(16) The length of each section of rod body is arranged to be within a range of 4001,600 mm, so as to control the total length of the assembled anchor rod while avoiding frequent extension because each section of rod body is too short; to ensure good connection while avoiding waste of material and time resulted from excessively long extension sections, the connecting male threads on the top end and the bottom end of the intermediate rod bodies have a length of 15100 mm, the hexagonal connector has a length of 1035 mm, the connecting sleeve has a length of 50150 mm, and the tightening threads have a length of 30150 mm.

(17) The outer diameter of the drill bit 1 is greater than the diameter of the anchor rod body by 38 mm, the drill bit 1 has an opening connected with the rod body, a plurality of sharp knives that protrude and are inclined to the center are arranged around the opening, the top of each sharp knife is at 35 mm from the center of the drill bit, spiral grooves configured to discharge the dust or debris produced during drilling from the drill bit are arranged on the side surface of the drill bit 1, and the spiral grooves have a width of 58 mm and a depth of 35 mm. A plurality of pawls are arranged at the clearance between the grooves on the side surface of the drill bit 1, and each pawl comprises a groove cavity, a circular shaft, a high-strength baffle plate and a strong spring, wherein, the groove cavity provides a space for rotation of the high-strength baffle plate, the bottom side of the groove cavity is movably connected with the high-strength baffle plate via the circular shaft, the strong spring is arranged between the high-strength baffle plate and the bottom of the groove cavity, the high-strength baffle plate is ejected by the strong spring and can rotate within the groove cavity via the circular shaft.

(18) An anchoring method utilizing the self-drilling and self-anchoring extendable anchor rod applicable to soft and weak coal rocks, comprising the following steps: a. using a drill rod to drill a hole at a designed position to designed hole length, and withdrawing the drill rod; at this point, the hole may collapse partially; b. selecting required quantity of intermediate rod bodies 2 and connecting sleeves 3 according to the designed hole length, utilizing the connecting sleeves to assemble the intermediate rod bodies 2 and the tail rod body 4 together to form an anchor rod body; the assembling and drilling process is as follows: mounting adrill bit 1 to the front end of the first intermediate rod body 2, inserting the head end of the rod body into the hole, mounting the rear end of the rod body to a drilling apparatus and then drilling, extending the rod body utilizing the connecting sleeves 3 and intermediate rod bodies 2 in the drilling process, and extending the rod body with the tail rod body 4 in the last extension, mounting the tail end of the newly combined rod body to the drilling apparatus and drilling after each extension, until the hole is drilled to its entire length; since the anchor rod body formed by the intermediate rod bodies 2 and the connecting sleeves 3 having threading (e.g. steel screw threading) on their surfaces, which does not have a dust discharge function, therefore, no coal dust or rock dust is discharged in the drilling process, and a great deal of coal and rock dust exists between the self-drilling section and the rod body of the anchor rod for drilling hole; thus, end anchoring force is generated at the end of the rod body owing to friction, and, in the shallow section of the hole, since the hole drilled out in soft and weak coal rock mass collapses, shrinks and deforms quickly, the rod body is pressed to generate anchoring force; c. shutting down the drilling apparatus when the exposed length of the tail rod body 4 is 30150 mm, separating the drilling apparatus from the tail rod body 4, fitting the tapered rubber plug 5, the tray 6 and the nut 7 over the tightening threads 13 on the tail end of the tail rod body 4 sequentially, and tightening up the nut for post-tensioning; thus, a primary installation is finished; d. at 12 h after construction, the hole collapse, shrinkage and deformation are developed more fully and the anchoring force is higher; then, tightening up the nut with a wrench for secondary post-tensioning; such tightening can also prevent prestress relaxation of the self-drilling and self-anchoring extendable anchor rod incurred by construction of other self-drilling and self-anchoring extendable anchor rods nearby; e. at 1224 h after construction, underground worker checking the post-tensioning force on the self-drilling and self-anchoring extendable anchor rod with a torque-indicating wrench, and post-tensioning up the self-drilling and self-anchoring extendable anchor rod again if the post-tensioning force does not meet the requirement, so as to maintain the post-tensioning force.