Application of Resin Bolt Support Technology in Jinfeng Gold Mine

Fung underground gold mine ore deposits break fold development, formation fragmented, partially erect occurrence even reversed. The fault zone is essentially a strong tectonic strain zone and a strong mineralized alteration zone, and the intra-band rock is strongly deformed. The surrounding rock of the ore body and the top and bottom plates is mainly composed of thin to medium-thick layer sandstone and thin layer of clay rock. The clay rock is very soft and broken. It is softened and muddy when it is soft, and it is easy to collapse. The engineering geological conditions are complex.
The support method used by the Jinfeng underground mine to start the main slope is the pipe joint anchor + steel mesh. The pipe-type anchor rod body has a wall thickness of 3 mm, a diameter of Φ 47.5 mm, a length of 2.4 m, and a slit width of 15 mm. Pipe joint anchor support has many advantages, such as convenient installation, timely support resistance, and the anchor does not lose its support resistance when the surrounding rock is significantly displaced, but there are also some problems, including low anchoring force. The pull-out anchor of Jinfeng Gold Mine is generally 6~10t, which is much lower than the pull-out force of resin anchors of the same length. The hole diameter is stricter, the aperture is larger, and the anchoring force is lower. Small, the bolt is easy to bend, it is difficult to enter the borehole completely, the anchoring depth is reduced, the anchoring force is reduced; the bolt is in contact with the air, and it is easy to oxidize and rust, especially in the roadway with larger groundwater, the bolt is more rusted and more serious. Due to the above shortcomings of the pipe joint anchor, its reliability in the application of roadway roof support and permanent roadway support is very poor. In view of this, Jinfeng Company's underground mines have introduced resin anchors, which are mainly used for roadway roofs and some underground projects with long service life, such as main ramps, underground substations, and wind wells.
1 resin anchor rod working principle and parameters selection resin anchor rods are made of rods with different strength materials and their accessories together with the matching resin anchoring agent. According to the design anchor length, the rod body is inserted into the chisel hole, after stirring, the anchoring agent Produces a chemical reaction that bonds the rod body to the rock mass in a certain period of time. After waiting for the installation time, install the pallet on the threaded end and tighten the nut to apply a certain pre-tightening force to the surrounding rock, so that the surrounding rock is in a three-direction stress state, thus improving the stress state of the surrounding rock and making the surrounding rock The strength is improved to strengthen the surrounding rock and prevent its movement, thereby improving the integrity and stability of the roadway [1]. Specifically, the resin anchor rod supports and reinforces the surrounding rock through the functions of “suspension, composite beam, extrusion reinforcement arch, and reduction of span”.
In order to determine the reasonable supporting parameters, on-site engineering geological survey was carried out on the surrounding rock of Jinfeng underground mine. According to the survey results, the Q value of the on-site rock mass is generally between 0.1 and 15, wherein the Q value is 0.4. The proportion of rock mass in the range of ~4 is large, and the proportion of rock mass in other Q values ​​is small.
The width of Jinfeng underground mine roadway is 4.5~5m, the height is 5~5.5m, and the excavation support ratio (ESR) is between 1.6~4. The diameter of the resin anchor is 25mm. According to the updated Barton's Qsupportchart[2] (see Figure 1), the support parameters of the Jinfeng underground mine roadway are as follows: the bolt spacing is 1.1~1.5m, within the same row. The spacing between the bolts is 1.1-1.3m, the thickness of the shotcrete is 65-75mm, the large value is selected when the rock mass is good, and the small value is selected when the rock mass is poor.
The length of the bolt is selected in the following two ways:
(1) According to Barton's bolt length calculation formula, the maximum length of the bolt is 1.72m.

Where: L———the length of the bolt, m;

B———the roadway span, m;
ESR———Excavation support ratio.
(2) According to Lang's proposed rock bolt net specification, the bolt length is twice the bolt spacing. The spacing of the bolts selected based on the Q value is 1.1 to 1.3 m, so the corresponding length of the bolt is 2.2 to 2.6 m. The rock bolt network specification was developed by Lang during the development of TheSnowyMountainHydroelectricScheme and is still widely used to determine the bolt length and spacing of "permanent" diverticulum [3]. For mine roadways, the length of the bolt can be smaller.
Combining the results obtained by the above two methods, it is also considered that all the roadways of Jinfeng underground mine need to spray a layer of 65-75mm thick concrete before installing the bolts, and finally determine the length of the bolts of Jinfeng underground mine support is 2. 4m.

2 resin anchor construction technology

After the blasting of the roadway, a layer of 65-75 mm thick concrete is sprayed in time. When the uniaxial compressive strength of the shotcrete reaches 1 MPa, the resin anchor is installed. The construction sequence of the anchor rods is from the outward direction to the head row by row, and the middle of the row is from the middle to the arch.

After repeated exploration and testing on site, Jinfeng Gold Mine realized the mechanized installation of resin anchors, reduced the labor intensity of workers, improved the installation efficiency of bolts, and enabled timely and effective support of roadways. The installation of the resin anchor is completed by the Boomer282 trolley. The specific installation procedure is as follows:
(1) placing four resin anchoring agents in a sausage-like string together in a PVC plastic tube;
(2) Place the PVC plastic pipe with resin anchoring agent on the left arm of the trolley, and slowly push the PVC plastic pipe into the borehole with the left arm of the trolley. When the front end of the PVC pipe is about 10cm away from the bottom of the hole, the propulsion is stopped, the left arm cooling water valve is opened, and the resin anchoring agent is pushed to the bottom of the hole with high-pressure water.
(3) Retract and remove the PVC plastic pipe, and install the anchor rod body together with its accessories on the right arm of the trolley.
(4) Operate the right arm of the trolley so that the anchor rod is aligned with the orifice and the angle is the same. Open the rock drill to advance and rotate the handle, so that the anchor rod body rotates into the borehole, and the anchor rod stops propelling when it is 5~8cm long outside the hole. Continue to rotate the anchor rod to make the resin coil in the hole evenly stir and stop rotating. After the anchor rod stops propelling, the anchoring agent stirring time is controlled to be 10~20s; from the bolt to the drilling hole to the end of the stirring, the time does not exceed 40s;

(5) After the resin anchoring agent is fully solidified, the rock drill rotates again to first break the nut coupling pin, and then tighten the nut to make the anchor piece close to the shotcrete.
3 resin bolt support should pay attention to the problem 3.1 The best three-way "resistance of resin anchor" when using resin bolt support, drilling, anchor, resin roll diameter "three-way" between A reasonable match is the key to achieving maximum anchoring power and maximum technical and economic benefits. Australia, the United Kingdom and other countries with advanced resin bolting support technology have conducted some research on this, and believe that the anchoring force is the largest when the diameter of the drill hole is 4 to 5 mm away from the diameter of the left-handed rebar without longitudinal reinforcement. The research results of Yang Zhenmao, Ma Nianjie and others show that appropriately increasing the diameter of the bolt does not significantly increase the cost of support, and the breaking strength of the bolt can be greatly improved. The diameter of the resin anchoring agent is preferably 3 to 5 mm smaller than the diameter of the borehole [4].
In combination with the current Jinfeng company's ongoing research on replacing the original diameter Φ25mm resin anchor with a diameter Φ22mm resin anchor, the author believes that this study can not directly consider the pull-out force of Φ22mm resin anchor can not meet the design requirements, but also should The breaking force and price of the two different diameter bolts are comprehensively compared, and the rock mass structure and its occurrence conditions, the complexity of the occurrence environment, the variability and the uncertainty are also considered.
3.2 Bolt quality The anchor rod body is made of rebar. The precision, length and strength of the material of the anchor rod body and nut, the tail thread of the rod body and the nut thread should meet the standard requirements. Otherwise, when the anchor is stressed, especially when the pressure of the surrounding rock of the roadway is large, the bolt is easily damaged and failed, thereby causing accidents such as roofing and sheeting.
The anchor tray is an important component for supporting bolts. If the shape of the pallet does not meet the requirements, the nut and the tray will be closed tightly, resulting in a decrease in the torque of the bolt and a decrease in the preload. If the size and material of the pallet do not meet the requirements, when the surrounding rock stress of the roadway increases, the pallet may be deformed or even pulled out, which greatly reduces the support function of the bolt.

The raw materials, appearance, diameter, length, consistency of resin mortar, solid-state ratio, compressive strength, gel time, waiting time, thermal stability, etc., the effect of resin anchoring agent on the anchoring performance of resin anchor Very big.
To this end, Jinfeng Company has established strict quality inspection and acceptance standards for supporting materials and products. The standards specify the shape, specifications, materials, performance indicators and allowable deviations of the products. All supporting materials and products must have a factory certificate, quality identification documents, etc. In addition, the mine regularly conducts on-site sampling inspection and material inspection of supporting materials and products to ensure the quality of supporting materials and products.
3.3 Bolt installation quality The bolt hole is too deep, the anchor rod can not reach the bottom of the hole, the anchoring agent at the bottom of the hole can not be stirred, the anchoring effect can not be produced, and the anchoring length is reduced, the anchoring force is reduced; the hole is too shallow, it will make The pallet cannot be installed, and the prestressing cannot be applied, and the effect of actively reinforcing the surrounding rock cannot be achieved. For this reason, the Jinfeng company's ground pressure control program stipulates that when drilling the bolt hole, it must be marked on the drill pipe to ensure that the drilling depth meets the design requirements.
If the dust and water in the anchor eye are not cleaned, it is equivalent to adding dust and water to the anchoring agent, which will weaken the strength of the anchoring agent. To this end, Jinfeng's ground pressure control program stipulates that the rock powder, accumulated water or other impurities in the bolt hole must be blown clean by pressing air or water before installation.
Resin anchors have their specific gel time and waiting for installation time. When the resin anchor is installed, the stirring time of the resin coil is too short, and the resin clay and the curing agent are not uniformly mixed, which will greatly reduce the adhesion between the anchoring agent and the surrounding rock and the anchoring agent and the metal rod. The stirring time is too long, exceeding the gel time, affecting the chemical reaction between the resin cement and the curing agent, and the adhesion between the anchoring agent and the metal rod body and the surrounding rock is greatly reduced; and if the waiting time is less than the installation time When the tray is tightened, the strength of the anchoring agent has not been fully developed, and the applied pre-stress does not reach the design value, which also reduces the anchoring performance of the resin anchor.
To this end, Jinfeng Company has specifically formulated a standard operating procedure for resin bolt installation, which stipulates that the driver of the trolley must strictly follow the specified mixing time of the resin anchoring agent and wait for the installation time to install the resin anchor. .
Another point to note is that when the surrounding rock is particularly loose and broken, the amount of resin anchoring agent should be appropriately increased, so that the resin anchoring agent can densely fill the annular space between the rod body and the hole wall to ensure that the resin anchor is sufficient. Anchoring force. In May 2015, a landslide occurred on the southern slope of the Jinfeng Open-pit Mine, causing cracking of the shotcrete in the 480-500 mRL section of the main slope of the underground mine, and the surrounding rock was seriously damaged. A large number of resin anchors were used in repairing the main ramp, but the number of resin anchors in each bore was still 4 knots. After the pull-out inspection of these resin anchors, it was found that their anchoring force was only 16-60 kN. Later, the resin anchors were re-punched, and 8 resin anchors were placed in each hole, and the pull-out resistance reached 200 kN or more.
4 Technical effects and economic benefits The technical parameters of the resin anchor and the original used pipe anchor are shown in Table 1.

Technically, the anchoring capacity of the resin anchor is more than twice that of the pipe-type anchor, and the hole diameter is smaller than that of the pipe-stitched anchor. The yield strength and tensile strength of the material are better than the pipe-type anchor. The roof management of Jinfeng Gold Mine Roadway and the extension of the service life of key roadway projects are of great significance. From the economic analysis, the price of resin anchors (including anchoring agent) is 24 yuan/set higher than that of pipe-stitched anchors, and 38,000 sets/a of resin anchors are consumed according to the roadway support. Jinfeng uses resin. The annual increase cost of the bolt is about 912,000 yuan, but the annual cost of roadway repair is about 1.5 million yuan, and the economic benefits are considerable.
Compared with pipe-stitched anchors, resin anchors have the advantages of timely support, strong anti-corrosion ability, large anchoring force, active support for rock mass, safety and reliability. Resin anchor combined with wet-spraying concrete effectively controls the deformation of the roof of the roadway, reduces the occurrence of roof fall accidents, improves the stability of underground mine shafts, greatly reduces the maintenance work of the roadway, and prolongs the service life of key projects. It provides a favorable guarantee for the safe and normal production of Jinfeng Underground Mine.
references:
[1] Li Longshui. Talking about the problems that should be paid attention to in the application of resin bolt support in mine roadway [J]. Energy and Environment, 2014(5): 53-56.
[2]Songlco_ar. ApplicationofRockMassClassificationSys-temsForfutureSupportDesignofthed_mTunnelNear
Alanya[C]//AThesisSubmittedtothegraduateSchoolof
NaturalandAppliedSciencesofMiddleEastTechnicalUni-
Versity, September, 2004: 24-24.
[3] B. H. G. Brady, E. T. Brown. RockMechanicsforUnder-
groundMining[R]. ThirdEdition, 2004: 333.
[4] Yang Zhenmao, Ma Nianjie, Guan Shanyue, et al. Reasonable matching of bolt drilling, rod body and resin coil diameter [J]. Journal of Rock Mechanics and Engineering, 2003(4), 659-663.

Article source: Mining Technology; 2017.17(3)

Author: Zhang walrus, Wu Yanpei; Guizhou Jinfeng Mining Co., Ltd., Guiyang 550001

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The Hydraulic Filter Element is used in the hydraulic system to filter out particulate debris and rubber impurities to ensure the cleanliness of the hydraulic system.