Who knows the production process of coal mine support?

From the establishment of Jinpushan Coal Mine to 1993, coal roadway and semi-coal roadway have always adopted traditional support methods. I-beam trapezoidal shed support and "top anchor (coal seam anchor)+side wall (stone wall)" are used in the semi-coal roadway 1994 to 1998 in No.9 Mine. From 1998, the combined support of "top anchor (resin anchor)+side anchor (w steel belt+resin anchor)" was adopted in the smooth blasting face of No.9 coal mine, and the combined support of "top anchor (resin anchor+concrete anchor)+side anchor (resin anchor)" was adopted in the fully mechanized excavation face of No.9 coal roadway in 2003. With the continuous popularization and deepening of bolt support technology, underground monitoring technology has also been improved.

1 bolt support technology in semi-coal roadway

1. 1 Mechanism of bolt support

Through theoretical analysis and underground test, it is found that the essence of bolt support is to make the bolt support body (including bolt, joist, metal mesh and anchor cable) and surrounding rock form a bearing structure through restraint, thus improving the bearing capacity of surrounding rock itself, especially after the plastic failure of surrounding rock, which can greatly improve the residual strength of surrounding rock and ensure the safe use of roadway.

1.2 design method of bolt support in semi-coal rock roadway

The design method of bolt support in semi-coal roadway of Jinpushan Coal Mine is a brand-new dynamic information design method based on the measured geomechanical data underground. This dynamic information design method has two characteristics: first, the design is not completed at one time, but a dynamic process; Second, the design makes full use of the information provided in each process. The dynamic information design method includes five parts: test site investigation and geomechanics evaluation, initial design, underground comprehensive monitoring, information feedback and design modification, and daily monitoring. Among them, the investigation of the test site includes in-situ stress, surrounding rock strength, surrounding rock structure and anchorage performance tests, and then carries out geomechanical evaluation on this basis to provide reliable design parameters for the preliminary design. The preliminary design is mainly based on numerical calculation method, combined with analytical method and empirical method, and a more reasonable preliminary design is determined according to surrounding rock parameters and existing measured data. Finally, the preliminary design is applied to the support of underground semi-coal roadway, and the displacement of surrounding rock and bolt stress are monitored in detail, and the preliminary design is verified or revised according to the monitoring results. After normal construction, daily monitoring should be carried out to ensure the safety of roadway. To sum up, the dynamic information design method is a dynamic, controllable and gradual improvement process, which conforms to the complex and changeable natural conditions of coal mines and is an advanced and practical design method.

1.2. 1 geomechanical test of surrounding rock of roadway

The rapid geomechanics testing system of roadway surrounding rock developed by Beijing Mining Research Institute of China Coal Research Institute is used to measure underground geostress and roadway surrounding rock strength.

1.2. 1. 1 geostress test

In-situ stress measurement adopts hydraulic fracturing measurement method, and the measuring instrument is SYY-56 hydraulic fracturing stress measuring device. Small hole drilling (56 mm) is adopted, and the maximum measurement depth is 30 m, which can be used for rapid and large-area underground geostress measurement. The same borehole can also be used to measure the strength of surrounding rock of roadway. The instrument consists of a separator, an imprint device, a positioner, a manual pump, an explosion-proof oil pump and a recorder.

1.2. 1.2 roadway surrounding rock strength test

Wqcz-Ⅱ surrounding rock strength tester is used to test the strength of underground surrounding rock. The device consists of surrounding rock strength tester, probe, hand pump, high pressure pipe, telescopic rod and so on. The diameter of the probe is d 56 mm, and the measuring depth is 30 m, which is very suitable for rapid underground measurement. The determination of rock mass strength is carried out in the surrounding rock drilling of underground roadway. The piston in the probe moves under the drive of high-pressure oil, so that the terminal thimble is pressed against the borehole wall. According to the critical pressure of thimble destroying the shaft wall, the uniaxial compressive strength of rock mass at this time can be obtained through simple calculation. In order to determine the compressive strength of rock stratum along the length of borehole, a test underground monitoring profile is taken every 200 mm~300 mm Surrounding rock strength test and in-situ stress measurement are carried out simultaneously. * * * Set up four stations and add the test results to the corresponding tables to provide theoretical calculation parameters for the preliminary design.

1.2.2 underground comprehensive monitoring

Underground comprehensive monitoring is an important part of bolt support technology in semi-coal roadway. After the initial design of bolt support is carried out underground, the deformation of surrounding rock, the distribution and magnitude of bolt (cable) stress are monitored in all directions, and the displacement and stress information of supporting body and surrounding rock are obtained, so as to judge the rationality and reliability of the initial design of bolt support and the stability and safety of surrounding rock of roadway. Then according to the monitoring information, the initial design is modified to make it gradually reasonable. According to the specific situation of semi-coal roadway in Jinpushan Coal Mine, the comprehensive monitoring content of bolt support is determined.

Adopt (1) cross layout method to install the surface displacement monitoring section, drill holes vertically and horizontally in the middle of the top and bottom plates, drive wooden stakes and measure nails. Generally, two monitoring sections are arranged at each station, with an axial spacing of 0.6 m ~ 1.0 m along the roadway.

(2) Using roof abscission instrument to test the internal and external displacement values within the anchorage range of roof strata. The anchor head of the deep base point of the separation indicator should be fixed in the stable rock stratum, and the shallow base point should be fixed at the end position of the anchor rod. The roof separation indicator should be installed as close as possible to the working face to detect the whole process of roof separation.

(3) There are two forms to monitor the stress of anchor (cable): one is an anchor dynamometer to measure the working resistance of end anchor (cable), and the other is an anchor dynamometer to measure the stress distribution of extended anchor and full-length anchor.

There are many kinds of anchor dynamometer, such as KS anchor dynamometer, which is composed of force-transmitting oil pressure pillow and vibrating wire pressure sensor, and the receiving instrument is KSE- 1 mine frequency meter; CH90A anchor dynamometer is a kind of resistance strain dynamometer, and the stress of anchor is obtained by measuring strain. YGS-200/300 anchor (cable) dynamometer is hydraulic, and it does not need supporting instruments to read the load directly. In Jinpushan Coal Mine, the instrument is used to measure the stress of end anchor bolt. The measuring instrument is a special instrument for measuring the stress of anchor rod in intrinsically safe underground roadway, which mainly includes force measuring anchor rod, static resistance strain gauge and transfer switch. When in use, it should be installed in the design position of ordinary anchor (to be tested), and the stress of anchor can be determined by measuring the strain values of different parts of anchor.

1.2.3 information feedback and modification of initial design

Measurement of information feedback index 1.2.3. 1

Because there are a lot of downhole measurement data, it is necessary to select aldehydes from many data. Modify and adjust the feedback information index of the initial design. This index should be simple and easy to operate, and it is the key data that affects the support parameters. Therefore, according to the geological and production conditions of Jinpushan roadway, five indexes are selected from three aspects: roof separation value, relative proximity of two sides and bolt stress. Among them, the roof separation value includes two roof separation values inside and outside the anchorage zone. Two indexes are selected for anchor stress, including 1 full-length anchor and 1 end anchor. The index data of feedback information must be determined accurately, because it is an important index related to the safety and economy of roadway bolt support.

1.2.3.2 Modify the standard of initial design.

By comparing the measured data with the information feedback index, the rationality of the initial design of support can be judged, and the initial design can be modified if necessary. According to the conditions of semi-coal roadway in Jinpushan Coal Mine, the criteria for modifying its initial design are determined.

(1) Do not modify the initial design. If the measured value is less than the feedback index value, the initial design will not be modified.

(2) The initial design should be modified. If one or several measured values are greater than the feedback index value, the initial design needs to be modified. First, if the delamination value of the anchorage zone is greater than the feedback index value, one anchor rod will be added in each row or the row spacing 100 mm will be reduced. Second, if the stress of the anchor rod is greater than the feedback index value, the diameter of the anchor rod will be increased by 2 mm, and if the diameter exceeds 22 mm, a stronger material will be replaced. Thirdly, if the separation value outside the anchorage zone is greater than the information feedback index value, the length of the anchor rod is increased by 200 mm; ; If the anchor length is greater than 2.4 m, increase the anchor density and reduce the row spacing of a row of anchors. Fourthly, if the distance between the two sides is greater than the feedback index value, the length of the side anchor rod will increase by 200mm；; ; When the anchor length is greater than 2 m, the row spacing of 1 anchor is increased or decreased in each row. After the modified support design is implemented underground, on-site monitoring is needed to evaluate the support effect and the safety of the roadway.

1.2.4 Daily monitoring

After the normal construction of bolt support, daily monitoring should be carried out to ensure the safety of roadway. Daily monitoring includes three parts.

(1) Spot check of anchoring force. In the process of roadway excavation and construction, assign special personnel to conduct random inspection on the anchoring force of the anchor rod, with the sampling ratio not less than 10% and the time interval not exceeding 2 d. Only nondestructive drawing shall be done during random inspection, and the drawing shall be stopped after reaching the specified value.

(2) Roof abscission monitoring. Roof abscission indicator is not only used for comprehensive monitoring, but also used for daily monitoring. Roadway every 25 m~30 m, install a roof indicator. Within 30 m from the heading face, observe the roof separation value. Beyond 30 m, unless the separation layer is loose, there is still an obvious growth trend. Generally, you can stop the specific data and observe the colors of the two scales instead. The leaders and technicians on duty are responsible for observation, and the rest of the staff should also pay attention to observation at any time, so as to find abnormal phenomena as soon as possible and ensure safety.

(3) Detection of bolt pre-tightening torque. In the process of roadway excavation, assign a special person to sample the pre-tightening force of the anchor nut with a torque indicating wrench at a ratio of not less than 30% and a time interval of not more than 1 d, and it is qualified after reaching the specified value.

1.3 bolt supporting materials and monitoring instruments for semi-coal rock roadway

Bolt supporting materials include bolt body, anchoring agent, tray, nut, steel keel, metal anchor cable, etc. In recent years, the use of high-strength and high-rigidity bolt materials has become the main form of bolt support in semi-coal rock roadway. It plays an important role in ensuring the safe state of roadway, improving the reliability of support and construction speed, and accelerating the rapid advancement of coal mining face.

In the aspect of mine pressure monitoring, LBY roof abscission instrument, YGS anchor (cable) dynamometer, CM-200 dynamometer anchor and other instruments were purchased and applied to bolt support technology.

2 monitoring software for ground pressure of bolt support in semi-coal roadway of Jinpushan Coal Mine

In order to reduce the workload of engineers and technicians, LAMD software is compiled, which is convenient for technicians to timely and accurately process a large number of ground pressure monitoring data, judge the rationality of the initial design, and make modifications when necessary.

2. 1 software composition

Database system: input, store and output the ground pressure monitoring data to be processed. Drawing system: according to the monitoring data provided by the database, draw various monitoring curves of mine pressure. Judgment system: to judge the rationality of the initial design of bolt support.

2.2 System functions

The main functions provided by the system include: processing the observation data of roadway surface displacement, roadway roof separation, full-length anchor dynamometer anchor and end anchor, analyzing the data processing results, and expressing the observation results intuitively in a graphical way; According to the observation results, the initial design is verified, and when the initial design does not meet the requirements, various suggestions for modifying the initial design are put forward.

Application and prospect of bolt support in semi-coal roadway

Application of bolt support in 3. 1 semi-coal roadway

Bolt support in semi-coal roadway in Jinpushan is widely used in 90 1 return air roadway, 903 belt roadway, 903 return air roadway, 902 return air roadway and 90 1 mining roadway.

3.2 the prospect of bolt support

It will be further popularized in 3# coal mining roadway and large section cavern, and strive to realize bolt-mesh support for all roadway support. In order to provide more detailed information for the preliminary design of bolt support, in-situ stress test should be supplemented in the mine. Optimizing the size of coal pillar in roadway supported by bolt can improve the resource recovery rate under the condition of ensuring the stability of roadway. Develop the rapid excavation technology and technology of coal roadway and semi-coal roadway, and improve the speed of roadway formation with bolt support.

4 conclusion

(1) Field monitoring is an important part of bolt support technology. After the implementation of bolt support, the displacement and stress information of various roadway surrounding rocks and supporting bodies are obtained to the maximum extent, which is the necessary basis for judging the stability of roadway surrounding rocks and verifying and modifying the initial design.

(2) After the underground bolt support is implemented, comprehensive monitoring should be carried out, including roadway surface displacement, roof separation and bolt (cable) stress.

(3) After the normal construction of bolt support, long-term daily monitoring should be carried out, including roof separation and sampling of bolt anchoring force. , to ensure the safety of roadway.

(4) According to the conditions of semi-coal roadway in Jinpushan Coal Mine, five information feedback indexes are determined, and the corresponding index values are given on the basis of a large number of monitoring data. In the future application, we can judge whether the initial design is reasonable by comparing the measured data with the feedback index value, and give the corresponding design method.

(5) The compilation of monitoring software for bolt support in semi-coal rock roadway in Jinpushan Coal Mine improves the speed and accuracy of monitoring data processing, reduces the workload of engineers and technicians, and is of great significance to promote the daily and standardization of ground pressure monitoring.