High-pressure rock roadway excavation pre-splitting anchor injection deformation control structure and method

Abstract

The application discloses a pre-splitting anchor injection deformation control structure and method for high ground pressure rock roadway excavation, which comprises a roadway penetrating in a rock mass, two pre-splitting rock zones symmetrically arranged on the two sides below the roadway, the pre-splitting rock zones being arranged along the length of the roadway, the pre-splitting rock zone being a rock zone full of gravel and densely distributed cracks, the side wall surface of the roadway being sequentially provided with a concrete wall protection layer and a concrete anchor spraying layer, and a plurality of high-strength anchor rods, a lower arch part anchor cable, a high-pressure grouting anchor cable and an arch nest reinforcing grouting anchor cable being perpendicularly arranged in the inner wall of the roadway and extending into the rock mass, the application combines roadway support reinforcement and roadway blasting pressure relief two roadway reinforcement means, the pre-splitting rock zone is advanced along with the advancing face construction in the construction process, the influence of pre-splitting rock zone construction on support is avoided, the design of the arch nest reinforcing grouting anchor cable can secondarily reinforce the integrity and effectiveness of the roadway support system, and the method can make the roadway omit conventional steel support and other measures.

Description

Technical Field

[0001] This invention relates to the field of roadway support in mining engineering, and more specifically, to a pre-splitting anchoring deformation control structure and method for excavating high-pressure rock roadways. Background Technology

[0002] In underground coal mining design, development roadways and mining area roadways are generally arranged in the relatively hard rock mass above and below each layer of the roof. After continuous mining of the working faces on both sides of the mining area, the width of the protective coal pillars gradually decreases or the bearing capacity gradually weakens. Roadways that are affected by strong mining activities due to roof fractures in the goaf are prone to bulging, spalling, and floor heave. The original roadways need to be widened and reinforced multiple times to meet the requirements of use. In order to solve the problems of bulging and spalling that occur in the roadways during mining operations, the two most common measures are: one is to use pressure relief to alleviate the high stress concentration of the surrounding rock of the roadway, and the other is to strengthen the support to improve the resistance of the surrounding rock of the roadway to damage.

[0003] For hard rock masses, blasting for roadway pressure relief is effective and adaptable. However, the cracking and damage effects of blasting can destroy the integrity of the surrounding rock, weaken the performance of the support structure, and even cause it to fail. "Blasting pressure relief" and "support reinforcement" are contradictory yet unified. How to achieve the "synergistic dual effect" of the two is a very important research topic. The invention patent with authorization announcement number CN109630134B discloses a "roadway structure and a one-time roadway support method for high ground stress soft rock roadways". In this method, pressure relief holes are set at intervals and diagonally downward on both sides of the roadway. Explosives and detonators are loaded into them and then detonated to create a pressure relief zone below the roadway. This method provides effective protection for the roadway by creating a pressure relief zone. However, this method does not consider how the roadway can be supported simultaneously with blasting pressure relief. Furthermore, the original support structure of the roadway in this scheme may be damaged or even fail due to blasting. Therefore, it is necessary to propose a roadway and corresponding construction method that can be constructed efficiently, cost-effectively, and with reliable reinforcement quality. Summary of the Invention

[0004] One objective of this invention is to provide a pre-splitting anchoring deformation control structure and method for high-pressure rock tunnel excavation. This method allows for the creation of a pre-splitting rock zone beneath the tunnel during tunnel excavation, saving on conventional tunnel bottom reinforcement measures. Furthermore, the method for creating the pre-splitting rock zone does not affect the construction efficiency and quality of the anchoring system. When the tunnel is adjacent to the mining area, arch-socket reinforcement grouting anchors are used to reinforce the tunnel, further improving the integrity and stability of the anchoring system.

[0005] To achieve these objectives and other advantages according to the invention, according to one aspect of the invention, the invention provides a pre-splitting anchoring deformation control structure and method for high-pressure rock tunnel excavation, comprising:

[0006] The tunnel runs through the rock mass, and two pre-fractured rock zones are symmetrically arranged on both sides below the tunnel. The pre-fractured rock zones are set along the length of the tunnel. The pre-fractured rock zones are rock mass zones filled with gravel and dense cracks. The sidewall surface of the tunnel is successively provided with a concrete retaining layer and a concrete shotcrete layer, and multiple high-strength anchors, lower arch anchor cables, high-pressure grouting anchor cables, and arch socket reinforcement grouting anchor cables are anchored perpendicular to the inner wall of the tunnel and extend into the rock mass.

[0007] Preferably, multiple high-strength anchor bolts are spaced apart on both sides and the arch of the roadway. One end of each high-strength anchor bolt located within the rock mass is anchored with resin anchoring agent, and the other end located on the roadway sidewall is tightened and fixed to a W-shaped steel guard plate. Multiple lower arch anchor cables are anchored at the arch of the roadway, staggered and spaced apart from the multiple high-strength anchor bolts located at the arch of the roadway. One end of each lower arch anchor cable located within the rock mass is anchored with resin anchoring agent. The ends of multiple adjacent lower arch anchor cables located on the roadway sidewall are tightened together on an anchor cable steel strip. The W-shaped steel guard plate and the anchor cable steel strip are closely attached to the concrete retaining wall layer and embedded in the concrete shotcrete layer.

[0008] Preferably, each high-pressure grouting anchor cable is a hollow grouting anchor cable. One end of the high-pressure grouting anchor cable located in the rock mass is anchored with resin anchoring agent, and the other end of the high-pressure grouting anchor cable located on the sidewall of the roadway is anchored to the anchor cable support plate. The middle part of the high-pressure grouting anchor cable is anchored with cement material. The multiple high-pressure grouting anchor cables are divided into multiple top high-pressure grouting anchor cables and multiple side high-pressure grouting anchor cables. The top high-pressure grouting anchor cables are set at the arch of the roadway and vertically anchored upward in the rock mass. The side high-pressure grouting anchor cables are horizontally anchored in the rock mass from the sidewall.

[0009] Preferably, each arch cavity reinforcement grouting anchor cable is a hollow grouting anchor cable, and each arch cavity reinforcement grouting anchor cable is spaced apart between two adjacent lower arch anchor cables. One end of the arch cavity reinforcement grouting anchor cable is anchored to the anchor cable support plate on the roadway sidewall, the other end of the arch cavity reinforcement grouting anchor cable is anchored by resin anchoring agent, and the middle part of the arch cavity reinforcement grouting anchor cable is anchored by cement material.

[0010] Preferably, the concrete sprayed anchor layer includes a steel mesh, which is laid and fixed along the surface of the concrete retaining layer, and the steel bars used in the steel mesh have a diameter of ≥8mm.

[0011] Preferably, the construction method for the pre-splitting anchoring deformation control structure in the above-mentioned high-pressure rock tunnel excavation includes the following steps:

[0012] S1. During the forward excavation of the tunnel, blasting holes are drilled at the tunnel face. At the same time, at the bottom of the junction between the tunnel face and the tunnel sides, pre-splitting zone advance blasting holes are drilled obliquely downwards. Explosives and detonators are buried in the blasting holes at the tunnel face and the pre-splitting zone advance blasting holes, and sealed with stemming material. After the explosives at the tunnel face and the pre-splitting zone are detonated simultaneously, the rubble at the tunnel face is cleared.

[0013] S2. Concrete is sprayed onto the inner wall of the newly opened tunnel to form the concrete retaining layer;

[0014] S3. After the concrete retaining wall layer has initially set, drill holes with tools and install the high-strength anchor rods and the lower arch anchor cables. After they are in place, install the corresponding anchors and complete the tensioning operation of the anchor rods and anchor cables.

[0015] S4. The steel mesh is laid on the surface of the concrete retaining layer, and then concrete spraying is performed to form the concrete spray anchor layer;

[0016] S5. Repeat S1-S4. When the distance from the tunnel face is ≥30m, install and anchor the high-pressure grouting anchor cable, and use grouting equipment to perform high-pressure grouting with ultrafine cement.

[0017] S6. Repeat S5. When the horizontal distance L between the roadway and the mining face of the main roadway of the mining area is ≤50M, install and anchor the arch cavity reinforcement grouting anchor cable; and use grouting equipment to perform ultra-fine cement high-pressure grouting on the arch cavity reinforcement grouting anchor cable.

[0018] Preferably, the length of the pre-splitting zone advance blasting hole is ≥2m, it is inclined in front of the tunnel face, the angle formed by the pre-splitting zone advance blasting hole and the tunnel face is ≥5°, the pre-splitting zone advance blasting hole is inclined below the roadway floor, and the angle between the pre-splitting zone advance blasting hole and the outward extension line of the roadway floor is ≥5°.

[0019] Preferably, the pre-splitting zone pre-blasting hole extends from the end into the hole and is sequentially configured as a blasting pressure relief section and a blasting hole sealing section.

[0020] Preferably, after the high-pressure grouting anchor cable and the arch socket reinforcement grouting anchor cable are completed, high-pressure grouting operations need to be carried out regularly.

[0021] The present invention has at least the following beneficial effects:

[0022] First, during the tunnel excavation process, pre-blasting is carried out in the decompression zone below the tunnel to avoid damage to the anchor bolts, anchor cables, and tunnel when decompression is carried out after the tunnel is completed. Furthermore, the pre-fractured rock zone generated after blasting does not affect the construction and work of the anchoring structure above the tunnel.

[0023] Secondly, the pre-splitting and depressurization should be carried out before the construction of anchor bolts and cables, so that the anchor bolts and cables are more in line with the stress redistribution in the roadway after depressurization, the anchor bolt system can fully exert its effect, and can work better in coordination with the pre-splitting area.

[0024] Third, a combined anchor-spray and prestressed high-pressure grouting anchor cable support system was adopted, and a construction schedule was developed based on the distance from the tunnel face, ensuring both construction progress and excellent tunnel support performance.

[0025] Fourth, the pre-fractured rock zone effectively prevents floor heave and eliminates the need for conventional steel supports in the roadway, saving costs.

[0026] Fifth, secondary reinforcement grouting is carried out on the arch cavity reinforcement anchor cable. This method can effectively fill the newly generated cracks between the rock mass above the tunnel arch cavity and the anchoring system due to the continuous excavation of the mining face.

[0027] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part will be understood by those skilled in the art through study of the invention and over time. Attached Figure Description

[0028] Figure 1 An elevation view of the tunnel face and the pre-blasting hole in one technical solution of the present invention; a plan view of the tunnel face, the pre-splitting rock zone and the pre-blasting hole;

[0029] Figure 2 This is a plan view of the tunnel face, pre-splitting rock zone, and advanced blasting holes in one technical solution of the present invention;

[0030] Figure 3 This is a schematic diagram of an anchor bolt and anchor cable in one technical solution of the present invention;

[0031] Figure 4 This is a cross-sectional view of the tunnel and surrounding rock mass in one technical solution of the present invention;

[0032] Figure 5 This is a plan view of the rock mass where the tunnel is located in one technical solution of the present invention;

[0033] Figure 6 This is a schematic diagram of construction within a tunnel according to one technical solution of the present invention;

[0034] Figure 7 This is a diagram showing the development of the tunnel arch in one embodiment of the present invention;

[0035] Figure 8 This is a side view of a tunnel sidewall in one embodiment of the present invention. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can implement it based on the description.

[0037] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0038] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are conventional methods, and the components and parts described are commercially available. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "setting" should be interpreted broadly. For example, they can refer to fixed connection or setting, detachable connection or setting, or integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The terms "lateral," "longitudinal," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0039] like Figures 1-8 As shown, the present invention provides a pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation, comprising:

[0040] A tunnel 1 runs through the rock mass 10. Two pre-fractured rock zones 2 are symmetrically arranged on both sides below the tunnel 1. The pre-fractured rock zones 2 are continuous along the length of the tunnel 1 and are rock mass zones filled with gravel and dense cracks. The sidewalls of the tunnel 1 are sequentially provided with a concrete retaining layer 6 and a wire mesh concrete anchor spray layer 61. Multiple high-strength anchor bolts 31, lower arch anchor cables 32, high-pressure grouting anchor cables 4, and arch-reinforcement grouting anchor cables 5 are anchored perpendicularly to the inner wall of the tunnel 1, extending into the rock mass. In this technical solution, the tunnel 1 cross-section can be arched or rectangular. The pre-fractured rock zone 2 is a continuous rock mass fragmentation and crushing area formed by drilling downwards at the junction of the excavation face and the two sides of the tunnel 1, charging explosives, and detonating them simultaneously with the explosives at the excavation face. The distance between the pre-fractured rock zone 2 and the tunnel 1 is ≥2m. The appearance of the pre-splitting rock zone 2 causes the concentrated tangential stress, which was originally concentrated on the sides and bottom of the tunnel 1, to be transferred to the outside of the pre-splitting rock zone 2. The rock pillars on the sides become self-supporting rock rings, and the bottom plate of the tunnel 1 does not need additional reinforcement or manual cleaning in the future. The number and size of the pre-splitting rock zone 2 need to be initially designed according to the mechanical characteristics of the rock mass 10 and the tunnel 1. The high-strength anchor bolts 31 and the lower arch anchor cables 32 are anchored at the ends with resin anchoring agent to meet the initial support strength requirements. The tunnel 1 excavation process and the tunnel 1 reinforcement process will inevitably disturb the surrounding rock mass 10. In addition to the anchoring function, the high-pressure grouting anchor cable 4 makes the rock mass 10 outside the tunnel 1 actually become a "surrounding rock-grouting material combination" by the subsequent high-pressure injection of grouting material, which further improves the integrity of the anchoring system of the tunnel 1 and reduces the probability of anchor bolt and anchor cable failure.

[0041] In this technical solution, as the main roadway of the mining area approaches roadway 1, the deformation rate of roadway 1 is much lower than that of roadway 1 without reinforcement or with simple steel frame reinforcement due to the pre-splitting rock bands 2 set on both sides below. When the distance L between the mining face of the main roadway 7 and roadway 1 is less than a certain level, in order to compensate for the impact on the original anchoring system, the arch socket reinforcement grouting anchor cable 5 is constructed and high-pressure grouting is carried out to further strengthen the anchoring system and fill it. As the mining face of the main roadway 7 approaches, new cracks may be generated between the rock mass 10 above the arch socket of roadway 1 and the anchoring system.

[0042] In another technical solution, multiple high-strength anchor bolts 31 are spaced apart on both sides of the tunnel 1 and at the arch of the tunnel 1. One end of each high-strength anchor bolt 31 located within the rock mass 10 is anchored with resin anchoring agent, and the other end located on the sidewall of the tunnel 1 is tightened and fixed to a W-shaped steel guard plate 310. Multiple lower arch anchor cables 32 are anchored at the arch of the tunnel 1, staggered and spaced apart from the multiple high-strength anchor bolts 31 located at the arch of the tunnel 1. One end of each lower arch anchor cable 32 located within the rock mass is anchored with resin anchoring agent. Multiple adjacent lower arch anchor cables 32 are anchored at one end on the sidewall of the tunnel... The W-steel guard plate 310 and the anchor cable 320 are tightly attached to the concrete retaining wall layer 6 and embedded in the concrete sprayed anchor layer 61. The high-strength anchor rod 31 and the lower arch anchor cable 32 are constructed simultaneously with the excavation of the tunnel 1. First, holes are drilled from the tunnel 1 to the corresponding positions of the surrounding rock mass 10 and resin anchoring agent is placed in them. The corresponding high-strength anchor rod 31 and lower arch anchor cable 32 are then placed in and fixed to the fixed W-steel guard plate 310 and anchor cable 320 respectively with corresponding locking devices. Then, a high preload is applied by the locking devices.

[0043] In another technical solution, each high-pressure grouting anchor cable 4 is a hollow grouting anchor cable. One end of the high-pressure grouting anchor cable 4 located in the rock mass 10 is anchored with resin anchoring agent, and the other end of the high-pressure grouting anchor cable 4 located on the side wall of the tunnel 1 is anchored to the anchor cable support plate. The middle part of the high-pressure grouting anchor cable 4 is anchored with cement material. The multiple high-pressure grouting anchor cables 4 are divided into multiple top high-pressure grouting anchor cables 41 and multiple side high-pressure grouting anchor cables 42. The top high-pressure grouting anchor cables 41 are set at the arch of the tunnel 1 and vertically anchored upward in the rock mass 10. The side high-pressure grouting anchor cables 42 are horizontally anchored in the rock mass 10 from the side of the tunnel.

[0044] In another technical solution, each arch-reinforcement grouting anchor cable 5 is a hollow grouting anchor cable. Each arch-reinforcement grouting anchor cable 5 is spaced apart between two adjacent lower arch anchor cables 32. One end of the arch-reinforcement grouting anchor cable 5 located on the side wall of the roadway 1 is anchored to the anchor cable support plate, and the other end of the arch-reinforcement grouting anchor cable 5 is anchored with resin anchoring agent. The middle part of the arch-reinforcement grouting anchor cable 5 is anchored with cement material. The arch-reinforcement grouting anchor cables 5 are evenly distributed. When the mining face of the main roadway 7 of the mining area approaches, the high-pressure grouting process used by the arch-reinforcement grouting anchor cables 5 can effectively fill the additional cracks in the rock mass 10 on both sides of the arch of the roadway 1 caused by stress changes.

[0045] In another technical solution, the concrete sprayed anchor layer 61 includes a steel mesh 610, which is laid and fixed along the surface of the concrete retaining layer 6. The steel bars used in the steel mesh 610 have a diameter of ≥8mm. The close spacing of the steel bars in the steel mesh 610 ensures that the concrete sprayed anchor layer 61 provides good protection for the inner wall of the tunnel 1 and effectively prevents rock blocks from collapsing in the tunnel 1.

[0046] In another technical solution, the construction method of the pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation includes the following steps:

[0047] S1. During the forward excavation of the tunnel 1, blasting holes 110 are drilled at the excavation face of the tunnel 1. At the same time, at the bottom of the junction between the excavation face 11 and the side walls on both sides of the tunnel 1, pre-splitting zone advance blasting holes 20 are drilled obliquely downward. Explosives and detonators are buried in the blasting holes 110 and the pre-splitting zone advance blasting holes 20, and sealed with stemming material. After the explosives in the excavation face 11 and the pre-splitting zone are detonated at the same time, the rubble of the excavation face 11 is cleared.

[0048] S2. Concrete is sprayed onto the inner wall of the newly opened tunnel 1 to form the concrete retaining layer 6;

[0049] S3. After the concrete retaining layer 6 has initially set, drill holes with tools and install the high-strength anchor rod 31 and the lower arch anchor cable 32. After they are in place, install the corresponding anchors and complete the tensioning operation of the anchor rods and anchor cables.

[0050] S4. The steel mesh 610 is laid on the surface of the concrete retaining layer 6, and then concrete spraying is performed to form the concrete spray anchor layer 61;

[0051] S5. Repeat S1-S4. When the distance from the tunnel face 1 is ≥30m, install and anchor the high-pressure grouting anchor cable 4, and use grouting equipment to perform high-pressure grouting with ultrafine cement.

[0052] S6. Repeat S5. When the horizontal distance L between the roadway 1 and the mining face of the main roadway 7 is ≤50M, install and anchor the arch-reinforcement grouting anchor cable 5; and use grouting equipment to perform ultra-fine cement high-pressure grouting on the arch-reinforcement grouting anchor cable 5.

[0053] In this technical solution, the concrete retaining wall layer 6 and the concrete sprayed anchor layer 61 use sprayed concrete with a strength grade of not less than C30 and an initial setting time of not more than 30 minutes. Specifically, step S2 involves first drilling corresponding anchor holes into the rock mass 10 using a drilling rig and cleaning the holes. Then, the end of the anchor cable or anchor rod is used to push the resin anchoring agent cartridge into the anchor hole. The end of the anchor cable or anchor rod in the tunnel 1 is fixed with a mixer and the resin anchoring agent is rotated and stirred for an appropriate time. Finally, the corresponding anchor is installed in the tunnel 1 and the anchor cable is tensioned to the designed preload using a tensioning device. Specifically, in step S5, the high-pressure grouting anchor cable 4 requires additional grouting equipment. Furthermore, besides further reinforcing the existing anchoring system as a full-anchoring anchor cable, another purpose of the high-pressure grouting anchor cable 4 is to fill cracks in the rock mass 10 with cement grout. Therefore, it needs to maintain a distance of more than 30m from the tunneling face 1 to ensure the normal development of the working face and to prevent the "surrounding rock-grouting material assembly" formed after grouting from developing secondary cracks due to the tunneling work of the roadway 1. This ensures the effectiveness of the anchoring system and greatly reduces the probability of failure.

[0054] In another technical solution, the length of the pre-splitting zone advance blasting hole 20 is ≥2m, it is inclined in front of the tunnel face 1, the angle formed between the pre-splitting zone advance blasting hole 20 and the tunnel face 1 is ≥5°, the pre-splitting zone advance blasting hole 20 is inclined below the bottom plate of the roadway 1, and the angle between the pre-splitting zone advance blasting hole 20 and the outward extension line of the bottom plate of the roadway 1 is ≥5°. The pre-splitting zone advance blasting hole 20 must be arranged and drilled at intervals strictly according to the design position of the pre-splitting rock zone 2.

[0055] In another technical solution, the pre-splitting zone pre-blasting hole 20 extends from the end into the hole and is sequentially configured as a blasting pressure relief section 201 and a blasting hole sealing section 202. The blasting pressure relief section 201 is filled with emulsion explosives and detonators. Then, the blasting hole sealing section 202 is filled with stemming material. The emulsion explosives in the blasting pressure relief section 201 are detonated by detonators. The rock mass around the blasting pressure relief section 201 is pulverized, the cracks around the pulverized rock block area are dense, and the pre-splitting rock zone 2 is extended and lengthened.

[0056] In another technical solution, after the high-pressure grouting anchor cable 4 and the arch socket reinforcing grouting anchor cable 5 are completed, high-pressure grouting operations need to be carried out periodically.

[0057] The following are specific on-site examples:

[0058] Specific implementation examples are as follows:

[0059] An on-site investigation of a deep mine in western Shandong revealed that some roadways suffered severe damage from the dynamic pressure of the coal face, resulting in extensive crushing of the roof concrete sprayed layer. Multiple anchor bolts and cables on the lower sidewalls and shoulders were broken, with the maximum displacement of the roadway sides reaching 1500mm. The roadway sides exhibited severe bulging and breakage, and the roadway floor showed varying degrees of deformation, with a maximum bulging of 800mm. This forced some roadways to undergo more than three repairs before the mining phase could begin, disrupting normal mine operations and posing significant safety hazards. Furthermore, the repairs consumed substantial manpower and resources, greatly hindering the construction of a safe and efficient mine.

[0060] The newly opened-1180 rock centralized transportation roadway adopts a straight wall semi-circular arch cross section and is a full rock roadway. The newly excavated roadway has an excavation width of 4.9m, an excavation arch height of 3.95m, and an excavation gross cross-sectional area of ​​16.77㎡. The rock roadway is reinforced by a pre-splitting anchor injection deformation control method, which aims to meet the needs of ventilation, pedestrian, transportation, and pipeline laying in the coal mining area.

[0061] The detailed parameters of the pre-splitting anchoring deformation control structure for the excavation of the -1180 rock centralized transport roadway are as follows:

[0062] I. Explosive pressure relief

[0063] The pressure relief hole has a diameter of 42mm, a depth of 3000mm, and a spacing of 1300mm. The pressure relief hole is inclined at 5° towards the front of the tunnel face and 10° downward towards the horizontal plane. The pressure relief hole is filled with 2KG of rock emulsion explosive.

[0064] II. Support system along the tunnel face

[0065] (1) High-strength anchor bolts

[0066] Anchor bolt material specifications: CRMG700 steel grade left-handed threaded steel bar anchor bolt, rod diameter Φ22mm, length 2.4m, yield strength not less than 266kN, ultimate tensile strength not less than 323kN, elongation after fracture not less than 17%, impact absorption energy not less than 100J, rod tail thread specification is M24, thread length 150mm, formed by thread rolling process.

[0067] Anchor bolt support plate specifications: 150×150×10mm arched high-strength support plate, steel grade Q235, matched with high-strength nuts, high-strength self-centering ball washers and anti-friction nylon washers, with mechanical properties matching the anchor bolt body, and a bearing capacity of not less than 346kN.

[0068] Anchor bolt arrangement: The spacing between anchor bolts is 900×900mm, with 12 bolts per row; the pre-tightening torque of the anchor bolts must reach 400N·m and must not exceed 600N·m. Anchoring method: Resin-extended anchoring, with a drilled hole diameter of 30mm, using one MSK2835 and one MSZ2860 resin anchoring agent, with an anchoring length of 1207mm. All anchor bolts are driven perpendicular to the rock face; considering construction needs, a 5° error is allowed.

[0069] W-steel guard plate specifications: W-steel guard plates are used for surface protection. Four-rib guard plate specifications: 8mm thickness, 280mm width, and 330mm length. Large support plates may be used if rock conditions permit.

[0070] (2) Anchor cable support for the lower arch

[0071] Anchor cable type and specifications: The anchor cable material is 21.8mm thick, 1x19 strands of high-strength, low-relaxation prestressed steel strand, with a length of 6300mm. The drilled hole diameter is 32mm, and three MSK2850 resin anchoring agents are used, with an anchoring length of 1470mm.

[0072] Anchor cable arrangement: Three anchor cables are arranged in each row on the top plate of the lower arch, with a row spacing of 1800mm and a spacing of 1200 / 800mm, and are driven perpendicular to the rock surface of the roadway. The initial tension of the anchor cables is designed to be 250kN.

[0073] The anchor cables are connected by a 2000mm×180mm×10mm high-strength three-hole T-shaped steel strip and matching pads and anchors. The lower arch anchor cables are supported in a timely manner with the excavation face. Three anchor cables are matched with one high-rigidity T-shaped steel strip.

[0074] After completing the high-strength anchor bolts and lower arch anchor cable support, concentrated shotcrete construction will be carried out on the roadway surface. The thickness of the concrete sprayed layer shall not be less than 70mm, and the surrounding rock and anchor bolts and cables will be completely sealed.

[0075] III. High-pressure grouting anchor cables

[0076] High-pressure grouting anchor cables will begin grouting 30m after the excavation face. This includes three grouting anchor cables: the top high-pressure grouting anchor cable and the two side high-pressure grouting anchor cables. High-pressure grouting will be carried out in one shift per week.

[0077] (1) Top high-pressure grouting anchor cable

[0078] High-pressure grouting anchor cables are installed 30m behind the facing end. Grouting anchor cables and ordinary anchor cables are arranged alternately in alternating rows. Anchor cable type and specifications: The anchor cable material is Φ22mm, SKZ22-1 / 1860-5300 hollow grouting anchor cable, 1×8 strands of high-strength low-relaxation prestressed steel strand, length 5300mm, and borehole diameter Φ36mm.

[0079] The anchoring method and anchor plate specifications are the same as those for ordinary steel strand anchors. No more than two anchoring agents should be used in the hole.

[0080] Anchor cable arrangement: One anchor cable is placed in the center of the top slab, with a spacing of 1800mm, and driven perpendicular to the rock face. The initial tension of the anchor cable is designed to be 200kN. Before tensioning, a rubber sleeve and a rigid plastic tube are fitted. After tensioning, the rubber sleeve expands and seals the hole against the borehole wall.

[0081] (2) High-pressure grouting anchor cables on both sides

[0082] Anchor cable type and specifications: The anchor cable model, anchoring method, and anchor cable support plate specifications are the same as those of the top high-pressure grouting anchor cable.

[0083] Anchor cable arrangement: One anchor cable is installed per row per side, with a row spacing of 1800mm and a position 1000mm from the bottom plate, perpendicular to the tunnel side. Anchor cable design preload: The initial tension preload is 300kN.

[0084] The grouting material used is ultrafine cement for centralized high-pressure grouting, with a water-cement ratio of 0.6 and a grouting termination pressure of 8 MPa.

[0085] IV. Grouting Anchor Cables for Arch Reinforcement

[0086] When the working face is 50m away from the roadway, the arch cavity reinforcement grouting anchor cable construction begins, and one shift of concentrated high-pressure grouting is arranged every week.

[0087] Anchor cable type and specifications: The anchor cable model, anchoring method, and anchor cable support plate specifications are the same as those of the top high-pressure grouting anchor cable.

[0088] Anchor cable arrangement: one anchor cable in each row at the top and bottom arches, with a row spacing of 1800mm.

[0089] The grouting material used is ultrafine cement for centralized high-pressure grouting, with a water-cement ratio of 0.6 and a grouting termination pressure of 8 MPa.

[0090] V. Concrete Spraying

[0091] Mesh specifications: The mesh is made of 8# iron wire in a diamond shape, with a mesh size of 50×50mm and a length and width of 5000×1000mm. There are 2 pieces per row.

[0092] Concrete specifications: 70mm thick sprayed concrete layer, concrete strength not less than C30 (water:cement:sand:gravel = 1:2:5:3), 5% quick-setting water-reducing additive for grouting, full-section sealing of surrounding rock and prevention of exposed and corroded anchor rod and cable steel mesh.

[0093] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation, characterized in that, include: The tunnel runs through the rock mass, and two pre-fractured rock zones are symmetrically arranged on both sides below the tunnel. The pre-fractured rock zones are set along the length of the tunnel. The pre-fractured rock zones are rock mass zones filled with gravel and dense cracks. The sidewall surface of the tunnel is successively provided with a concrete wall protection layer and a concrete shotcrete layer, and multiple high-strength anchors, lower arch anchor cables, high-pressure grouting anchor cables, and arch socket reinforcement grouting anchor cables are anchored perpendicular to the inner wall of the tunnel and extend into the rock mass. The concrete sprayed anchor layer includes a steel mesh, which is laid and fixed along the surface of the concrete retaining layer, and the steel bars used in the steel mesh have a diameter of ≥8mm. The construction method for pre-splitting anchoring deformation control structures in high-pressure rock tunnel excavation includes the following steps: S1. During the forward excavation of the tunnel, blasting holes are drilled at the tunnel face. At the same time, at the bottom of the junction between the tunnel face and the tunnel sides, pre-splitting zone advance blasting holes are drilled obliquely downwards. Explosives and detonators are buried in the blasting holes at the tunnel face and the pre-splitting zone advance blasting holes, and sealed with stemming material. After the explosives at the tunnel face and the pre-splitting zone are detonated simultaneously, the rubble at the tunnel face is cleared. S2. Concrete is sprayed onto the inner wall of the newly opened tunnel to form the concrete retaining layer; S3. After the concrete retaining layer has initially set, drill holes with tools and install the high-strength anchor rods and the lower arch anchor cables. After they are in place, install the corresponding anchors and complete the tensioning operation of the anchor rods and anchor cables. S4. The steel mesh is laid on the surface of the concrete retaining layer, and then concrete spraying is performed to form the concrete sprayed anchor layer; S5. Repeat S1-S4. When the distance from the tunnel face is ≥30m, install and anchor the high-pressure grouting anchor cable, and use grouting equipment to perform high-pressure grouting with ultrafine cement. S6. Repeat S5. When the horizontal distance L between the roadway and the mining face of the main roadway of the mining area is ≤50M, install and anchor the arch cavity reinforcement grouting anchor cable; and use grouting equipment to perform ultrafine cement high-pressure grouting on the arch cavity reinforcement grouting anchor cable.

2. The pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation as described in claim 1, characterized in that, Multiple high-strength anchor bolts are spaced apart on both sides and the arch of the roadway. One end of each high-strength anchor bolt located in the rock mass is anchored with resin anchoring agent, and the other end located on the roadway sidewall is tightened and fixed to a W-shaped steel guard plate. Multiple lower arch anchor cables are anchored at the arch of the roadway, staggered and spaced apart from the multiple high-strength anchor bolts located at the arch of the roadway. One end of each lower arch anchor cable located in the rock mass is anchored with resin anchoring agent. The ends of multiple adjacent lower arch anchor cables located on the roadway sidewall are tightened together on an anchor cable steel strip. The W-shaped steel guard plate and the anchor cable steel strip are closely attached to the concrete retaining wall layer and embedded in the concrete shotcrete layer.

3. The pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation as described in claim 2, characterized in that, Each high-pressure grouting anchor cable is a hollow grouting anchor cable. One end of the high-pressure grouting anchor cable located in the rock mass is anchored with resin anchoring agent, and the other end of the high-pressure grouting anchor cable located on the sidewall of the roadway is anchored to the anchor cable support plate. The middle part of the high-pressure grouting anchor cable is anchored with cement material. The multiple high-pressure grouting anchor cables are divided into multiple top high-pressure grouting anchor cables and multiple side high-pressure grouting anchor cables. The top high-pressure grouting anchor cables are set at the arch of the roadway and vertically anchored upward in the rock mass. The side high-pressure grouting anchor cables are horizontally anchored in the rock mass from both sides of the roadway.

4. The pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation as described in claim 3, characterized in that, Each arch cavity reinforcement grouting anchor cable is a hollow grouting anchor cable. Each arch cavity reinforcement grouting anchor cable is spaced apart between two adjacent arch cavity anchor cables. One end of the arch cavity reinforcement grouting anchor cable is anchored to the anchor cable support plate on the roadway sidewall, and the other end of the arch cavity reinforcement grouting anchor cable is anchored by resin anchoring agent. The middle part of the arch cavity reinforcement grouting anchor cable is anchored by cement material.

5. The pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation as described in claim 1, characterized in that, The length of the pre-splitting zone advance blasting hole is ≥2m, it is inclined in front of the tunnel face, the angle formed by the pre-splitting zone advance blasting hole and the tunnel face is ≥5°, the pre-splitting zone advance blasting hole is inclined below the roadway floor, and the angle between the pre-splitting zone advance blasting hole and the outward extension line of the roadway floor is ≥5°.

6. The pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation as described in claim 5, characterized in that, The pre-splitting zone's advanced blasting holes extend from the end into the hole and are sequentially configured as a blasting pressure relief section and a blasting hole sealing section.

7. The pre-splitting anchoring deformation control structure for high-pressure rock tunnel excavation as described in claim 6, characterized in that, After grouting is completed, the high-pressure grouting anchor cables and arch socket reinforcement grouting anchor cables need to undergo high-pressure grouting operations periodically.

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