Anchor bolt length determination method based on monitoring of roof rock stratum horizontal extrusion force

Patent metadata

Field	Value
Publication number	US-11067392-B2
Application number	US-201917043778-A
Country	US
Kind code	B2
Filing date	May 14, 2019
Priority date	Dec 14, 2018
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

An anchor bolt length determination method based on monitoring of a roof rock stratum horizontal extrusion force includes drilling a borehole in the middle of a roadway roof to determine a surrounding rock fracturing scope by a borehole television. The method includes selecting the number and locations of horizontal extrusion force measuring points according to the surrounding rock fracturing scope. The method includes monitoring and recording a change of the horizontal extrusion force over time in the borehole by a device for monitoring a roof rock stratum horizontal extrusion force. The method includes selecting a location with the largest horizontal extrusion force as a center of a anchoring segment of an anchor bolt to determine a distance between the anchoring center and the roof. The method includes calculating a total length of the anchor bolt.

First claim

The invention claimed is:

1. An anchor bolt length determination method based on monitoring of a roof rock stratum horizontal extrusion force, comprising the following steps:
at step (1), drilling a borehole in the middle of a roadway roof to determine a surrounding rock fracturing scope by a borehole television;
at step (2), selecting the number and locations of horizontal extrusion force measuring points according to the surrounding rock fracturing scope;
at step (3), monitoring and recording a change of the horizontal extrusion force of each horizontal extrusion force measuring point over time in the borehole;
at step (4), selecting a location with the largest horizontal extrusion force as a center of an anchoring segment of an anchor bolt to determine a distance between the anchoring center and the roof; and
at step (5), calculating a total length of the anchor bolt;
wherein at step (3), the change of the horizontal extrusion force of each horizontal extrusion force measuring point over time in the borehole is monitored and recorded by a device for monitoring a roof rock stratum horizontal extrusion force comprising a pressure measuring segment, a connecting rod, a hydraulic pump, a pressure gauge, a high-pressure oil pipe, a pressure control valve, a tray, a push rod and a connection casing; the connecting rod is connected with the pressure measuring segment, a front end of the push rod is connected with the connecting rod, a rear end of the push rod passes through the tray, and the connection casing is connected with the tray; the high-pressure oil pipe is connected with the hydraulic pump and protrudes to the pressure measuring segment through inner cavities of the push rod and the connection casing; the pressure measuring segment comprises a main pipe, a hydraulic bladder, a fixing ring, a barrier sheet, an outer pillow housing and a connection sleeve; both ends of the hydraulic bladder are sleeved on the main pipe by the fixing rings, and an oil inlet is disposed on the main pipe to be in communication with the hydraulic bladder; the outer pillow housing is sleeved on the main pipe, the connection sleeve is wrapped around an outer side of the outer pillow housing, and the barrier sheet is disposed between the fixing ring and the outer pillow housing.

2. The anchor bolt length determination method based on monitoring of a roof rock stratum horizontal extrusion force according to claim 1 , wherein at step (1), the borehole is 2-5 m in depth and 70-100 mm in diameter; at step (2), the horizontal extrusion force measuring points are disposed at a portion 1 m or more from the roof and mutually spaced less than 0.5 m.

3. The anchor bolt length determination method based on monitoring of a roof rock stratum horizontal extrusion force according to claim 1 , wherein each of the high- pressure oil pipes is divided into a plurality of segments and the high-pressure oil pipes are mutually connected by an oil pipe joint, one segment is connected on the hydraulic pump, one segment is disposed in inner cavities of the push rod and the connecting rod, and another segment is disposed in the pressure measuring segment; the oil pipe joint is disposed in the connection casing; the pressure control valve and the pressure gauge are further disposed on the high-pressure oil pipe connected on the hydraulic pump; two or more pressure measuring segments are connected on the connecting rod, and one communicating high-pressure oil pipe is disposed for each pressure measuring segment; a design length margin of the high-pressure oil pipe is placed in the connection casing.

4. The anchor bolt length determination method based on monitoring of a roof rock stratum horizontal extrusion force according to claim 3 , wherein monitoring and recording the change of the horizontal extrusion force over time in the borehole by the device for monitoring a roof rock stratum horizontal extrusion force comprises the following steps:
at step a, connecting the connecting rod with the pressure measuring segment, connecting the high-pressure oil pipes in the inner cavities of the connecting rod and the pressure measuring segment by the oil pipe joint, fixing the tray, and mounting the connection casing;
at step b, pushing the connecting rod and the pressure measuring segment into the borehole by the push rod, and after the tray and the roof are fixed, dismounting the connection casing and the push rod;
at step c, connecting the exposed high-pressure oil pipes, and connecting the hydraulic pump, the pressure control valve and the pressure gauge;
at step d, turning on a switch on the pressure control valve, performing pressurization by injecting oil using the hydraulic pump, and after the reading of the pressure gauge reaches 5-6 MPa, stopping pressurization and returning hydraulic oil; emptying air in the high-pressure oil pipe by repeating this step 2-5 times;
at step e, performing pressurization by injecting oil using the hydraulic pump, and after the reading of the pressure gauge reaches 5-6 MPa, closing the pressure control valve;
at step f, performing pressurization for a plurality of pressure measuring segments respectively by injecting hydraulic oil according to steps d and e;
at step g, dismounting the hydraulic pump, and monitoring and storing monitoring data of the pressure gauge; and
at step h, opening the pressure control valve to discharge the hydraulic oil; connecting the connection casing with the push rod to take out the connecting rod and the pressure measuring segment from the borehole.

5. The anchor bolt length determination method based on monitoring of a roof rock stratum horizontal extrusion force according to claim 1 , wherein the high-pressure oil pipe is connected with the oil inlet on the main pipe by an oil pipe joint, internal threads is disposed at inner sides of pipe walls at both ends of the main pipe respectively to be mated with an external thread of the connecting rod, and external threads is disposed at outer sides of pipe walls at both ends of the main pipe respectively to be mated with an internal thread of the barrier sheet; a through-hole is disposed in the tray, and the connecting rod passes through the through-hole of the tray; the connection casing is connected with an external thread at a convex position of the tray;
the push rod pushes the connecting rod and the pressure measuring segment by the connection casing.

6. The anchor bolt length determination method based on monitoring of a roof rock stratum horizontal extrusion force according to claim 1 , wherein the outer pillow housing is divided into four parts of same shape, and the combination body of the outer pillow housing is a cylindrical housing; the outer pillow housing is sleeved on the main pipe when the hydraulic bladder contracts, and expands in four parts when the hydraulic bladder is liquid-filled to expand; both ends of the connection sleeve are closely attached to the main pipe, and the connection sleeve tightly presses both ends of the outer pillow housing to be in contact with the main pipe.

7. The anchor bolt length determination method based on monitoring of a roof rock stratum horizontal extrusion force according to claim 1 , wherein at step (5), calculation of a length of the anchor bolt comprises calculation of an anchoring segment length L a1 of the anchor bolt, a free segment length L a2 of the anchor bolt and a total length L a of the anchor bolt, wherein the free segment length of the anchor bolt is

L

a
⁢

⁢
2

Assignees

• Univ Shandong Science & Tech

Inventors

• Tan Yunliang
• Zhou Kai
• Yu Fenghai
• Zhao Tongbin

Classifications

• E21D21/0093

  Accessories · CPC title

• G01B21/02 Primary

  for measuring length, width, or thickness (G01B21/10 takes precedence) · CPC title

• E21B49/00

  Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells · CPC title

• E21F17/00

  Methods or devices for use in mines or tunnels, not covered elsewhere (mine lighting F21, H05B) · CPC title

• E21F17/185 Primary

  Rock-pressure control devices with or without alarm devices; Alarm devices in case of roof subsidence (props with load-measuring devices E21D15/46) · CPC title