Construction method for deeply-buried high-ground-stress metal mine soft rock roadway supporting structure

Abstract

The invention provides a construction method for a deep-buried high-ground-stress metal mine soft rock roadway supporting structure, belongs to the technical field of soft rock roadway supporting, and solves the problem that large-deformation disasters occur frequently due to the fact that a traditional low-stress passive support is difficult to bear stress of metal mine deep-buried engineering soft rock. The method comprises the following steps: excavating or blasting a construction working surface of roadway surrounding rock; point measurement lofting is conducted on the long anchor rod and the short anchor rod, a W-shaped steel belt is laid after positioning lofting, and holes are cleaned after drilling is completed; anchoring ends of the long anchor rod and the short anchor rod are anchored by adopting an anchoring agent, the anchoring agent is pushed to the bottom of a hole along the wall of the drill hole, the long anchor rod and the short anchor rod are respectively pushed after the anchoring agent is pushed and positioned, and prestress is respectively applied to the long anchor rod and the short anchor rod. When the surrounding rock of the roadway deforms, the high-stress energy absorption structure layer can provide high-strength support, compensate and improve the bearing capacity of the surrounding rock of the roadway, and meanwhile, the extrusion resistance and impact resistance of the support structure can be improved, so that the safety of the roadway is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft rock roadway support, and particularly relates to a construction method for a support structure of a soft rock roadway in a deep-buried high in-situ stress metal mine. Background Art

[0002] In the metal mines in the northwest region, a large amount of manpower and material resources have been invested in the research of mine rock mechanics and roadway support, and many research results have been obtained. However, the large deformation and failure phenomena of deep surrounding rocks and support structures are still very common, the repair rate remains high, seriously affecting production efficiency and economic benefits, and threatening the lives of underground workers.

[0003] Since the mining in the mining areas of the northwest region has entered the deep mining stage, the mechanical behavior characteristics of deep rock masses will change significantly compared with those of shallow parts. Especially under the combined action of high in-situ stress and various geological structures, the rock mass stability shows significant characteristics different from that of the surrounding rocks in other non-metal mining areas, that is, "the strength of a single rock block is high, that is, hard rock in geology; the overall stability of the rock mass is poor, that is, soft rock in engineering". Therefore, in this geological environment, with the increase of mining depth, the surrounding rock comes under pressure quickly, has a large deformation, and a long duration, showing obvious rheological characteristics. If the traditional "double-layer bolt-net shotcrete + U-shaped steel arch frame" support for hard rock, which is "strong roof and hard support", is still used, it is still impossible to fundamentally solve the problems of large deformation disasters and frequent accidents of surrounding rocks in deep mining.

[0004] For the traditional support technology for hard rock, if ordinary bolt support is used for high in-situ stress fractured soft rock, on the one hand, the dense drill holes formed in the originally fractured surrounding rock during the bolt drilling process seriously damage the already low surrounding rock strength; on the other hand, ordinary bolts are made of PR materials, which belong to low-stress support materials. Since it is difficult for them to withstand the "fast, large, long" (coming under pressure quickly, large deformation, long duration) stress brought by the surrounding rock, the phenomenon of bolt fracture and failure often occurs, and finally the occurrence of large deformation disasters, often resulting in the situation of digging first and then lying, supporting first and then repairing, seriously affecting the construction period and the safety of workers. For U-shaped steel arch frames and steel pipe beams, etc., they are all passive supports, and the support force they can provide is limited, and they cannot withstand the "fast, large, long" stress brought by the surrounding rock, and the phenomenon of passive support distortion and failure often occurs.

[0005] In view of the above reasons, in order to achieve less or no repair of the roadway during the operation period and finally realize the safe, sustainable and efficient production of the mining area, an improved technical solution for the deficiencies of the existing technology is needed. Summary of the Invention

[0006] The object of the present invention is to provide a construction method for a support structure of a soft rock roadway in a deep-buried high in-situ stress metal mine, so as to solve the problem of frequent occurrence of large deformation disasters caused by the fact that traditional low-stress passive supports are difficult to withstand the stress of soft rock in deep-buried projects of metal mines.

[0007] The technical solution of the present invention is as follows: A construction method for a support structure of a soft rock roadway in a deep-buried high in-situ stress metal mine includes the following steps: Step 1: Excavate or blast the construction surface of the roadway surrounding rock according to the design requirements. When the excavation or blasting reaches the design size, spray concrete to form a plain sprayed concrete layer to seal the rock surface. Step 2: Taking the circumferential distance of the roadway as the spacing and the axial distance as the row spacing, measure and set out the positions of long bolts and short bolts. The long bolts and short bolts are arranged alternately in sequence. After the positioning and setting out, lay the W-shaped steel strip. The W-shaped steel strips are connected into a ring to make the hole positions on the W-shaped steel strip coincide with the hole positions of the positioning and setting out, and then start drilling. After the drilling is completed, clean the holes. The long bolts and short bolts have the same structure but different lengths, and are made of NPR material. One end of the long bolts and short bolts is the anchoring end, and a tray is provided at the end opposite to the anchoring end. A locking device is provided at the position where the tray is arranged, and a constant resistor is sleeved between the tray and the anchoring end. Step 3: Anchor the anchoring ends of the long bolts and short bolts with anchoring agents. Push the anchoring agents along the borehole wall to the bottom of the hole. After the anchoring agents are pushed and positioned, push the long bolts and short bolts respectively, and apply prestress to the long bolts and short bolts respectively.

[0008] As a further improvement of the present invention, in Step 1, after forming the plain sprayed concrete layer, lay a flexible net. The flexible net is laid closely against the rock surface and fixed, and safety protection for propping is carried out after the flexible net is laid.

[0009] As a further improvement of the present invention, in Step 2, the error range of the hole distance of the position measurement and setting out of the long bolts and short bolts is +150 mm; the error range of the drilling depth is +50 mm; the error range of the drilling angle is +5".

[0010] As a further improvement of the present invention, in Step 3, the anchoring agent is a resin anchoring agent.

[0011] As a further improvement of the present invention, in Step 3, the tensile force of the long bolts is not less than 300 kN, and the tensile force of the short bolts is not less than 200 kN; the pull-out resistance of the long bolts is not less than 350 kN, and the pull-out resistance of the short bolts is not less than 250 kN.

[0012] The beneficial effects of the present invention are as follows: On the one hand, this construction method adopts an active support technology different from the original passive support; on the other hand, different from the traditional support materials that only provide low stress, this active support technology adopts NPR materials with a constant resistance coupling energy absorption structure that can provide high stress, that is, a surrounding rock support layer composed of different NPR components, which is the energy absorption layer. The NPR components used in this construction method are all constructed from new NPR materials, and the new NPR materials all have the characteristics of high constant resistance, high elongation rate, and rapid energy absorption. Through the above excellent characteristics, they can continuously provide high support force for the roadway surrounding rock on the basis of high elongation rate, effectively controlling the occurrence of large deformation disasters of the surrounding rock.

[0013] The main support structures formed in this construction method include: an energy absorption layer composed of NPR components such as NPR long bolts, NPR short bolts, flexible nets, and W-shaped steel strips; a plain shotcrete layer is laid on the surface. When the roadway surrounding rock deforms, the high-stress energy absorption structure layer can provide high-strength support, compensate for and improve the bearing capacity of the roadway surrounding rock itself, and at the same time can also improve the anti-extrusion and anti-impact capabilities of the support structure, thereby ensuring the safety of the roadway. Description of the Drawings

[0014] Figure 1 It is the cross-sectional view of the roadway bolt support of the present invention; Figure 2 It is the cross-sectional profile view of the roadway bolt support of the present invention; Figure 3 It is the circumferential plane expansion view of the roadway bolt support of the present invention; Figure 4 It is the schematic diagram of the bolt structure in the present invention.

[0015] In the figure: 1 - roadway surrounding rock; 2 - long bolt; 3 - short bolt; 4 - flexible net; 5 - plain shotcrete layer; 6 - W-shaped steel strip; 7 - lock; 8 - tray; 9 - constant resistor; 10 - anchorage end. Detailed Embodiments

[0016] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0017] Example 1, The implementation steps in this example are summarized as follows: preparation work before construction → excavation / blasting of the construction working surface → spraying concrete to form a plain shotcrete layer → laying a flexible net + temporary support → determining the bolt position → fixing the W-shaped steel strip → positioning the drill rig → drilling → clearing the hole → reaming the hole → installing the anchoring agent → inserting the bolt → stirring and anchoring → installing the constant resistor → placing the tray → installing the anchor → tensioning and anchoring.

[0018] (1) Preparation work before construction Before the construction starts, corresponding preparatory work shall be done first, including the preparation of corresponding construction machinery, construction materials, construction personnel, etc., and it shall be confirmed that all preparations are complete and perfect before the construction.

[0019] (2) Excavation / Blasting of the construction working face Whether it is the excavation / blasting during the tunneling process of mine exploitation or the chamber excavation / blasting after removing the original support of the roadway, construction survey shall be carried out for each cycle to control the excavation section size, and the excavation contour line shall be drawn with red paint or corresponding marks shall be made. According to the measured contour, a method combining pneumatic pick rock drill and weak blasting technology shall be adopted to minimize the disturbance of blasting vibration to the surrounding rock mass, and overbreak and underbreak shall be strictly controlled during the chamber excavation. After the excavation is completed, the loose and easily fallen parts of the chamber wall surrounding rock shall be cleaned by machinery.

[0020] (3) Spraying concrete to form a plain sprayed concrete layer, laying a flexible mesh and temporary support After the roadway is excavated to the designed size and the loose and easily fallen parts of the chamber wall surrounding rock are cleaned, 50 - 100 mm of C20 concrete shall be sprayed to seal the rock surface. If the surrounding rock at the site is observed to be intact, this step can be omitted. Then, a high-strength polyester fiber flexible mesh (mesh size 50 mm × 50 mm or 100 mm × 100 mm) shall be laid flat on the whole chamber excavation surface. The flexible mesh must be closely attached to the rock surface, and local parts shall be fixed with 1.2 m long anchor bolts. Laying the flexible mesh can prevent local surrounding rock from loosening and falling. After laying the flexible mesh, hydraulic props shall be used for jacking and safety protection to prevent large-area collapse caused by the instantaneous deformation of the surrounding rock.

[0021] (4) Measurement and lofting, determining the bolt positions, fixing the W-shaped steel strip, and positioning the drill rig According to the requirements of the interval and row spacing of the bolt layout design (the circumferential distance of the roadway is the interval, and the axial distance is the row spacing), measurement and lofting of the bolt positions shall be carried out for accurate positioning, and marks shall be made with red paint. Then, the W-shaped steel strip shall be laid, so that the hole positions on the W-shaped steel strip coincide with the positioned hole positions, and it shall be fixed with temporary support to prevent the W-shaped steel strip from falling and hurting people. After the above work is completed, the drill rig is positioned and ready to start drilling.

[0022] (5) Drilling and hole cleaning Before drilling, the rock surface shall be further processed to remove dangerous rock blocks, and it shall be checked and rechecked by a special person. The drilling direction shall be perpendicular to the rock surface or intersect with the rock layer at a large angle as much as possible. When the included angle is too small, the drilling angle shall be locally adjusted. The error range of the bolt hole spacing is +150 mm; the error range of the drilling depth is +50 mm; the error range of the drilling angle is +5". For drilling construction, it is preferably to use a bolt drill rig first, and an impact-rotary drill rig (such as YT28 rock drill) shall be used below the middle arch waist. The drill bit diameter shall be preferably 30 - 32 mm (matching the NPR bolt with a diameter of 21.8 mm).

[0023] The drilling depth shall meet the design requirement that the exposed length of the bolt is 150 - 250 mm after the bolt installation is completed and the prestress is applied. After the drilling is completed, high-pressure air is used for hole cleaning to facilitate the smooth and efficient installation of the anchoring agent in the follow-up.

[0024] (6) Installation of NPR bolts The long bolts and short bolts are made of NPR (Negative Poisson’s Ratio) material. The bolts can also be replaced by cable bolts. The structures of the long bolts and short bolts are as Figure 4 shown. The installation of the long bolts and short bolts includes the pushing and positioning of the anchoring agent and the bolt, the stirring of the anchoring agent, the installation of accessories (W-shaped steel strip, tray, constant resistor, locking device), and the application of prestress.

[0025] 1) Pushing and positioning of the anchoring agent and the bolt The anchoring end of the bolt is anchored with a resin anchoring agent. The specification and model of the anchoring agent shall match the hole diameter. The anchoring length of the bolt shall not be less than 100 cm, generally 100 - 150 cm, and can be adjusted according to the actual situation of the prestress application on site.

[0026] The anchoring agent is pushed in by a PE pipe. Slowly push 2 - 3 sections of the anchoring agent along the hole wall until the bottom of the hole. After reaching the bottom of the hole and pulling out the PE pipe, it shall be ensured that the anchoring agent does not slip. During the pushing process, situations such as the rupture of the anchoring agent and the inability to push it in shall be avoided. The pushing of the long bolts and short bolts is carried out after the pushing and positioning of the anchoring agent is completed. The pushing of the long bolts and short bolts is preferably carried out manually. If it is impossible to push manually, a drill can be used for "rotary pushing".

[0027] 2) Stirring of the resin anchoring agent The resin anchoring agent is stirred by a hand-held drill. When it is not easy to operate with a hand-held drill, a bolt drill can be used. During the stirring process, the bolt shall be pushed in smoothly and evenly, and the phenomenon of pulling back the bolt shall not occur. The stirring shall be completed before the anchoring agent gels. The stirring time for CZS and CKB series of anchoring agents is 30 s.

[0028] 3) Installation of accessories The installation of accessories shall start after the waiting time for the installation of the anchoring agent specified in the specifications. For CZS and CKB series of anchoring agents, the installation of accessories starts 15 minutes after the stirring is completed. The installation sequence of accessories is: W-shaped steel strip, tray, constant resistor, locking device. During the installation process, the W-shaped steel strip shall be ensured to be connected into a loop to give full play to the integrity of the structural network formed by the NPR long bolts and short bolts.

[0029] 4) Application of prestress The tensile force applied by the long anchor rod shall not be less than 300 kN, and the tensile force applied by the short anchor rod shall not be less than 200 kN; the uplift resistance applied by the long anchor rod shall not be less than 350 kN, and the uplift resistance applied by the short anchor rod shall not be less than 250 kN; for the equipment used in tensioning, the gauges of the hydraulic press shall be calibrated and rechecked in advance; the prestress tensioning shall be implemented after the installation of the accessories is completed; the pneumatic cable tensioning machine shall be used for the construction of the anchor rod tensioning.

[0030] Before applying prestress, the anchor rod body shall be perpendicular to the tray (if an anchor rod axial force meter is installed, the anchor rod must be located as much as possible at the center of the axial force meter, and care must be taken not to affect the accuracy of the measurement due to the eccentric installation of the axial force meter) to effectively apply the prestress. When the prestress of the anchor rod is applied to the specified value, it must be tensioned in place at one time and no secondary tensioning is allowed. The stroke of the tensioning jack does not exceed 10 cm each time (the maximum stroke is 12 cm).

Claims

1. A construction method for a soft rock tunnel support structure in a deep buried high ground stress metal mine, characterized in that: The following steps are involved: Step 1: excavating or blasting the construction working surface of the tunnel surrounding rock (1) according to the design requirements, spraying concrete when the excavation or blasting reaches the designed size, forming a plain sprayed concrete layer (5) to seal the rock surface; Step 2: With the circumferential distance of the tunnel as the spacing and the distance in the axial direction as the row spacing, the point measurement and layout of the long anchor rods (2) and the short anchor rods (3) are carried out, the long anchor rods (2) and the short anchor rods (3) are arranged alternately in sequence, and after positioning and layout, W-shaped steel belts (6) are laid, and the W-shaped steel belts (6) are connected into a ring so that the hole positions on the W-shaped steel belts (6) coincide with the hole positions of the positioning and layout, and drilling is started. After the drilling is completed, the holes are cleaned; The long anchor rod (2) and the short anchor rod (3) have the same structure but different lengths and are made of NPR material. One end of the long anchor rod (2) and the short anchor rod (3) is an anchoring end (10), and the end opposite to the anchoring end (10) is provided with a tray (8). A lock (7) is provided at the location where the tray (8) is provided, and a constant resistor (9) is sleeved between the tray (8) and the anchoring end (10). Step 3: The anchoring ends (10) of the long anchor rod (2) and the short anchor rod (3) are anchored with an anchoring agent, and the anchoring agent is pushed into the bottom of the hole along the wall of the borehole. After the anchoring agent is pushed into position, the long anchor rod (2) and the short anchor rod (3) are pushed in respectively, and prestress is applied to the long anchor rod (2) and the short anchor rod (3).

2. A construction method for a soft rock tunnel support structure for a deep buried high ground stress metal mine according to claim 1, characterized in that: In step one, after the plain sprayed concrete layer (5) is formed, the flexible net (4) is laid, the flexible net (4) is laid closely to the rock surface and fixed, and after the flexible net (4) is laid, top support and safety protection are performed.

3. The construction method for a soft rock tunnel support structure for a deep buried high-in-situ stress metal mine according to claim 1, characterized in that: In step 2, the error range of the hole spacing for measuring the position of the long anchor rod (2) and the short anchor rod (3) is +150 mm; the error range of the drilling depth is +50 mm; and the error range of the drilling angle is +5".

4. The construction method for a soft rock tunnel support structure for a deep buried high-in-situ stress metal mine according to claim 1, characterized in that: In step three, the anchoring agent is a resin anchoring agent.

5. The construction method for a soft rock tunnel support structure for a deep buried high-in-situ stress metal mine according to claim 1, characterized in that: In step three, the tensioning force of the long anchor rod (2) is not less than 300 kN, and the tensioning force of the short anchor rod (3) is not less than 200 kN; the pull-out force of the long anchor rod (2) is not less than 350 kN, and the pull-out force of the short anchor rod (3) is not less than 250 kN.

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