Deep high stress large chamber yielding type combined support structure and construction method

Abstract

This invention provides a pressure-yielding combined support structure and construction method for deep, high-stress large chambers, belonging to the field of mining construction technology. It includes: a large chamber composed of multiple support units, each unit comprising short anchor cables, a steel mesh, long anchor cables, a steel grid, and a reinforced concrete layer; the short anchor cables are anchored along their entire length to the shallow part of the surrounding rock, the steel mesh is laid on the surface of the surrounding rock and secured by the short anchor cables; the long anchor cables are full-length prestressed anchor cables, with their anchored sections connected to the surrounding rock, and a double-pallet structure at their free ends; the steel grid is fixed through the double-pallet structure and connected to the steel mesh laid on the outer side; by controlling the shallow fracture zone with short anchor cables and achieving the dual functions of active support and full-length anchoring with long anchor cables, combined with the pressure-yielding energy absorption of the arc-shaped gaskets at the steel grid connections and the double-pallet structure, the technical problems of easy damage to the support structure in deep large chambers, difficulty in applying prestress, and poor overall stability are effectively solved, achieving controllable release of surrounding rock deformation and long-term structural stability.

Description

Technical Field

[0001] This invention belongs to the field of mining construction technology, specifically relating to a pressure-relief combined support structure and construction method for deep high-stress large chambers. Background Technology

[0002] As shallow mineral resources are gradually depleted, mining operations are extending to deeper areas. Deep engineering projects generally face a complex environment characterized by "high stress, high pressure, high temperature, high humidity, and high risk of disturbance," especially below kilometer-deep wells, where the rock mass is under high stress and its failure mode exhibits obvious nonlinear large deformation characteristics, posing a great challenge to the stability control of roadways and chambers.

[0003] To meet the demands of large-scale mining, the cross-sectional dimensions of major underground functional chambers are increasing, with some large chambers having spans exceeding 10 meters and heights exceeding 15 meters, forming typical large-section, large-volume underground spatial structures. Under deep, high-stress conditions, these large chambers experience high stress concentration in the surrounding rock, large deformation, and wide-ranging damage. Traditional single-method anchor bolt support, shotcrete, or ordinary anchor cable support are insufficient to effectively control surrounding rock deformation, easily leading to engineering problems such as anchorage failure, shotcrete layer cracking, grid distortion, and even chamber instability and collapse.

[0004] In existing technologies, support methods for shallow or medium-depth tunnels mainly include end anchoring of ordinary anchor cables, steel arch support, and reinforced concrete lining. However, although ordinary end anchoring cables can be prestressed, the anchoring section is prone to failure once the surrounding rock cracks, making it difficult to adapt to the large deformation characteristics of deep surrounding rock. Ordinary full-length anchoring cables can continue to function after the surrounding rock deforms, but it is difficult to apply prestress and cannot provide active support for the surrounding rock. In addition, traditional steel gratings are mostly rigid connections, lacking pressure relief and buffering capacity, and are prone to overall instability under high stress.

[0005] Therefore, there is an urgent need to develop a method suitable for deep, high-stress large chambers that can take into account both active support and pressure relief energy absorption, ensuring construction safety and long-term stability. Summary of the Invention

[0006] Based on the above-mentioned technical problems, the purpose of this invention is to provide a pressure-yielding combined support structure and construction method for deep high-stress large chambers. By controlling the shallow fracture zone with short anchor cables and achieving the dual functions of active support and full-length anchoring with long anchor cables, combined with the pressure-yielding and energy-absorbing arc-shaped gaskets at the steel grid connection and the double-pallet structure, the technical problems of easy damage to the support body of deep large chambers, difficulty in applying prestress, and poor overall stability are effectively solved, and the controllable release of surrounding rock deformation and long-term stability of the structure are achieved.

[0007] The specific technical solution is as follows: A deep, high-stress large-chamber pressure-relief combined support structure includes: a large-chamber composed of multiple support units, each support unit comprising short anchor cables, steel mesh, long anchor cables, steel grid, and a reinforced concrete layer; the short anchor cables are anchored along their entire length to the shallow part of the surrounding rock, the steel mesh is laid on the surface of the surrounding rock and reinforced by the short anchor cables; the long anchor cables are prestressed anchor cables with their entire length anchored, their anchored sections connected to the surrounding rock, and their free ends equipped with a double-pallet structure; the steel grid is fixed by the double-pallet structure and connected to the steel mesh laid on the outer side; the reinforced concrete layer is poured on the outer side of the steel grid and steel mesh to form an integral support structure; the steel grid is composed of multiple sections of grid arch frames connected by bolts, and an arc-shaped washer is provided between the bolt head and nut at the connection of adjacent sections; the double-pallet structure includes a first pallet and a second pallet, the distance between the first pallet and the second pallet is 300mm, and the second pallet is an arc structure with its bottom protruding towards the surrounding rock.

[0008] In addition, the deep high-stress large chamber pressure-relief combined support structure provided by the present invention may also have the following additional technical features: In the above technical solution, the long anchor cable is also equipped with grouting holes and grout outlet holes.

[0009] A construction method for pressure-relief combined support in deep, high-stress large chambers includes the following steps: S1: The main chamber will be excavated in 4 layers, with each layer having an excavation height of 5m, using smooth blasting technology; S2: After each layer of excavation is completed, short anchor cables are installed and steel mesh is laid to form the initial support; S3: Construction of long anchor cables, wherein the long anchor cables are Φ21.6×10000mm mining full-length anchored prestressed anchor cables, with a row spacing of 1.2m×2m, an anchor cable tray of 350×350×20mm, a preload of 200kN, an end anchorage length of not less than 2.0m, and the ends are anchored with resin anchoring agent. The free section is anchored with resin or mortar. Ten double-tray long anchor cables are evenly installed across the entire cross section, with a double tray spacing of 300mm. S4: Construction steel grating, steel grating spacing 1000mm, adjacent steel grating arch frames are connected by steel bars with a spacing not greater than 1000mm, steel grating is locked by double-pallet long anchor cables reserved in step S3 and connected to the steel mesh laid on the outside; S5: Repeat steps S2-S4 to complete all layer construction; S6: The reinforced concrete layers are poured from bottom to top to form an integral support structure.

[0010] In the above technical solution, in step S2, the short anchor cable is made of Ф17.8×6000mm steel strand with a spacing of 1m×2m, the anchor cable tray is 300×300×16mm, and the steel mesh is made of Ф10 round steel with a mesh spacing of 150×150mm.

[0011] In the above technical solution, step S3, the construction process of the full-length anchored prestressed anchor cable includes drilling positioning, drilling, hole inspection, resin filling, anchor cable insertion, pre-tensioning, and hole sealing grouting.

[0012] In the above technical solution, after the construction of the long anchor cable in step S3 is completed, the anchor cable is sealed and protected by spraying 30mm thick concrete.

[0013] In the above technical solution, in step S5, the arc-shaped pad is compressed into a flat shape when the steel grid is subjected to a large impact load, thereby achieving the function of pressure absorption.

[0014] In the above technical solution, after the steel grating is completed, a trial assembly is carried out. The allowable deviation for the perimeter assembly is ±3cm, and the plane warping is less than 2cm.

[0015] In the above technical solution, the gap formed between the tray and the rock surface is filled with grout during anchor cable grouting, forming a tight fit with the rock surface.

[0016] The present invention provides a pressure-relief combined support structure and construction method for deep high-stress large tunnels, which, compared with the prior art, has the following advantages: 1. The main chamber is excavated in four layers. After each layer is excavated, short anchor cables and steel mesh are first installed to form initial support, which effectively controls the shallow surrounding rock fracture zone and ensures the safety of personnel and equipment during construction. After the excavation of each layer is completed, long anchor cables are installed in a unified manner to realize the assembly line operation of drilling, cable threading, tensioning and grouting, which greatly improves construction efficiency.

[0017] 2. Short anchor cables are anchored along their entire length in the shallow part of the surrounding rock to control the fractured zone formed by blasting disturbance; long anchor cables are prestressed anchor cables with full-length anchorage, which can not only apply active support prestress, but also continue to play a suspension role after the surrounding rock deforms. They have the dual advantages of end anchorage and full-length anchorage, and are suitable for the complex deformation characteristics of deep high-stress environments.

[0018] 3. The free end of the long anchor cable is equipped with a double tray structure, in which the second tray is an arc-shaped structure with the bottom protruding towards the surrounding rock, forming a line contact with the uneven rock surface, avoiding the loss of preload due to the uneven rock surface; the gap between the tray and the rock surface is filled with grout to form a tight fit, which significantly improves the anchoring effect and durability of the anchor cable.

[0019] 4. The steel grating consists of multiple sections of grating arches connected by bolts, with arc-shaped gaskets installed at the joints. When the surrounding rock undergoes large deformation or is subjected to impact loads, the arc-shaped gaskets are compressed from an arc shape to a flat shape, allowing the surrounding rock to deform to a certain extent to release pressure, reducing the load intensity borne by the support structure, and preventing brittle failure of the support structure due to excessive stress, thus realizing the support concept of "absorbing energy by yielding pressure".

[0020] 5. The steel grating is locked by double-pallet long anchor cables and welded to the outer steel mesh to form an integral support skeleton within the layers; through continuous construction of anchor cables and steel grating between each layer, a reinforced concrete layer is finally poured to form a three-dimensional spatial joint support system from shallow to deep and from inside to outside, which significantly improves the deformation resistance and long-term stability of the large chamber under the action of high ground stress in a kilometer-deep well. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the chamber support structure and the number of excavation layers of the present invention; Figure 2 for Figure 1 Enlarged view of a portion at point A; Figure 3 This is a schematic diagram of the single-layer blasting sequence of the present invention; Figure 4 This is a schematic diagram of the structure of the full-length anchorage prestressed anchor cable of the present invention; Figure 5 This is a schematic diagram of the steel grating connecting bolts and arc-shaped gaskets of the present invention; in, Figures 1 to 5 The correspondence between the reference numerals and component names in the attached drawings is as follows: 10 Long anchor cable, 11 Short anchor cable, 12 Steel mesh, 13 Steel grating, 14 Reinforced concrete layer, 15 First tray, 16 Second tray, 17 Arc-shaped gasket. Detailed Implementation

[0022] The following are specific implementation cases and appendices. Figure 1-5 The present invention will be further described, but the present invention is not limited to these embodiments.

[0023] A pressure-relief combined support structure for deep, high-stress large chambers, such as Figure 1-5 As shown, it includes: a large chamber composed of multiple support units, each support unit including short anchor cables 11, steel mesh 12, long anchor cables 10, steel grid 13, and a reinforced concrete layer 14; the short anchor cables 11 are anchored along their entire length to the shallow part of the surrounding rock, the steel mesh 12 is laid on the surface of the surrounding rock and compressed by the short anchor cables 11; the long anchor cables 10 are prestressed anchor cables with full-length anchorage, their anchorage section is connected to the surrounding rock, and the free end is provided with a double-pallet structure; the steel grid 13 is fixed by the double-pallet structure and connected to the steel mesh 12 laid on the outside; the reinforced concrete layer 14 is poured on the outside of the steel grid 13 and the steel mesh 12 to form an integral support structure; the steel grid 13 is composed of multiple grid arch frames connected by bolts, and an arc-shaped washer 17 is provided between the bolt head and nut at the connection of adjacent two sections; the double-pallet structure includes a first pallet 15 and a second pallet 16, the distance between the first pallet 15 and the second pallet 16 is 300mm, the second pallet 16 is an arc structure, and its bottom protrudes towards the surrounding rock.

[0024] The above technical solution utilizes prestressed anchor cables with full-length anchorage. This process differs from both ordinary steel strand full-length and end-anchored anchor cables. Ordinary steel strand full-length anchored anchor cables offer full-length anchorage, allowing them to continue suspension and reinforcement even in the event of cracking in underground engineering. However, they are difficult to prestress and cannot provide active support to the rock mass. End-anchored anchor cables fully utilize the characteristics of prestressed anchor cables, providing active support to the rock mass, but they fail once the rock mass cracks, making them unsuitable for underground engineering conditions. Full-length anchored prestressed anchor cables combine the advantages of both while avoiding their disadvantages. The construction sequence is: drilling positioning → drilling → hole inspection → resin filling → anchor cable insertion → pre-tensioning → grouting.

[0025] Specifically, traditional anchor cable trays are made of ordinary steel plates. Their biggest drawback is that during anchor cable pre-tensioning, the unevenness of the rock surface prevents the tray surface from adhering tightly to the rock surface, resulting in insufficient pre-tensioning force and consequently anchor cable failure or reduced effectiveness. In the embodiments of this invention, an arc-shaped tray is used, with holes at the bottom for the anchor cable to pass through. The bottom of the tray protrudes above the rock surface, thus changing the contact between the tray and the rock surface from surface contact to line contact. This better adapts to the unevenness of the rock surface. At the same time, the gap formed between the tray and the rock surface is filled with grout during anchor cable grouting, forming a tight fit with the rock surface.

[0026] By dividing the large chamber into four layers for excavation, short anchor cables 11 and steel mesh 12 are constructed after each layer is excavated to form initial support, effectively controlling the shallow surrounding rock fracture zone and ensuring the safety of personnel and equipment during construction. After the excavation of each layer is completed, long anchor cables 10 are constructed uniformly to realize the streamlined operation of drilling, cable threading, tensioning, and grouting, which greatly improves construction efficiency.

[0027] The short anchor cable 11 is anchored along its entire length in the shallow part of the surrounding rock to control the fractured zone formed by blasting disturbance; the long anchor cable 10 is a prestressed anchor cable with full-length anchorage, which can not only apply active support prestress, but also continue to play a suspension role after the surrounding rock deforms. It has the dual advantages of end anchorage and full-length anchorage, and is suitable for the complex deformation characteristics of deep high-stress environment.

[0028] A double-pallet structure is set at the free end of the long anchor cable 10. The second pallet 16 is an arc-shaped structure with its bottom protruding towards the surrounding rock, forming a line contact with the uneven rock surface to avoid loss of preload due to the unevenness of the rock surface. The gap between the pallet and the rock surface is filled with grout to form a tight fit, which significantly improves the anchoring effect and durability of the anchor cable.

[0029] The steel grating 13 is made up of multiple sections of grating arches connected by bolts, with arc-shaped gaskets 17 installed at the joints. When the surrounding rock undergoes large deformation or is subjected to impact loads, the arc-shaped gaskets 17 are compressed from an arc shape to a flat shape, allowing the surrounding rock to deform to a certain extent to release pressure, reducing the load intensity borne by the support structure, and preventing brittle failure of the support structure due to excessive stress, thus realizing the support concept of "absorbing energy by yielding pressure".

[0030] The steel grating 13 is locked by double-pallet long anchor cables 10 and welded to the outer steel mesh 12 to form an overall support skeleton within the layers. Through continuous construction of anchor cables and steel grating 13 between each layer, a reinforced concrete layer 14 is finally poured to form a three-dimensional spatial joint support system from shallow to deep and from inside to outside, which significantly improves the deformation resistance and long-term stability of the large chamber under the action of high ground stress in a kilometer-deep well.

[0031] In an embodiment of the present invention, the long anchor cable 10 is also provided with grouting holes and grout outlet holes.

[0032] In an embodiment of the present invention, a construction method for a pressure-relief combined support system in a deep, high-stress large chamber includes the following steps: S1: The main chamber is buried 1200m below the ground surface. The chamber is 30m long, 15m wide and 20m high. In order to achieve steady excavation of the chamber, it is divided into 4 layers for step-by-step excavation. Each layer is 5m high. The excavation adopts smooth blasting technology and adopts the method of drilling more holes and using less explosives to reduce the blasting disturbance to the surrounding rock and reduce the difficulty of subsequent support.

[0033] S2: Excavation of each layer needs to proceed gradually from one side to the other. Each layer is expected to require 30 blasts, with each blast volume controlled at 75 cubic meters. 3 To reduce the exposed area of ​​the surrounding rock, a roof inspection and treatment are carried out after each blast. Following treatment, short anchor cables 11 (Ф17.8×6000mm) are installed. These short anchor cables 11 are anchored along their entire length using ordinary steel strand, with a spacing of 1m x 2m between sections. The anchor cable trays are 300x300x16mm. Simultaneously, short anchor cables 11 are reinforced with a steel mesh 12 made of Ф10 round steel, spaced 150x150mm apart. The main purposes of the short anchor cable 11 + steel mesh 12 construction are twofold: firstly, to control the shallow rock fracture zone after excavation; and secondly, to ensure safety during construction.

[0034] S3: After completing the excavation of the entire single layer according to step S2, uniformly construct Ф21.6×10000mm full-length prestressed anchor cables for mining. Ten long anchor cables are spaced 1.2m x 2m apart, with anchor cable trays of 350x350x20mm, a preload of 200kN, and an end anchorage length of no less than 2.0m. Resin anchoring agent is used for end anchoring, while resin or mortar anchoring is used for free sections. Ten double-tray long anchor cables 10 are evenly installed across the entire cross-section, with a double-tray spacing of 300mm (this invention is mainly used for later fixing of the steel grating 13). Simultaneously, to enhance the overall integrity of the support, anchor cable steel strips are added, with a width of 300mm and a thickness of 5mm. After all anchor cables in each layer are constructed, a 30mm layer of sprayed concrete is applied to initially seal the anchor cables.

[0035] The anchor cable construction process is as follows: drilling and positioning → drilling → hole inspection → resin filling → anchor cable insertion → pre-tensioning → hole sealing and grouting.

[0036] By implementing steps S2 and S3 separately, safety during construction was ensured, and by implementing step S3 uniformly, unified drilling, unified anchor cable insertion, and unified tensioning grouting were achieved, thus ensuring construction efficiency.

[0037] S4: After the single-layer anchor cable construction is completed, steel grating 13 is constructed. The spacing of steel grating 13 is 1000mm. Adjacent steel grating 13 arch frames are connected by steel bars with a spacing not exceeding 1000mm. The steel grating 13 is fixed by locking it with the 10 anchor cables reserved in step S3. At the same time, a steel mesh 12 made of Ф10 round steel is pressed on the outside of the steel grating 13. The steel grating 13 is erected, and the inner layer of steel mesh 12 is laid tightly on the outside of the steel grating 13 and welded to it. At the same time, the steel grating 13 is welded to the anchor cable tray to ensure the integrity of the support structure. The grating adopts a welded skeleton, and the welding is double-sided welding with a welding length of 5d. Each grating arch frame is divided into multiple sections, which are connected by bolts. At the same time, a set of arc-shaped washers 17 are placed under the bolt head and nut to play a pressure-relieving role. To ensure accurate positioning and stability of the steel frame, the bottom of each grating arch frame is fixed with locking anchor cables. After the steel grating 13 is processed, it should be placed on a flat ground for trial assembly. The allowable deviation for the perimeter assembly is ±3cm, and the warping of the plane should be less than 2cm. Before installing the steel frame, the centerline and elevation of the excavated section should be checked. The allowable deviations for both the lateral and elevation sides are ±5cm.

[0038] S5: After completing the support of one layer through steps S2-S4, excavate the next layer, and then install the anchor cables and steel grid 13 according to steps S2-S4 until the construction of 4 layers is completed.

[0039] S6: Carry out reinforced concrete construction, with reinforced concrete poured in layers from bottom to top.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pressure-relief combined support structure for deep, high-stress large chambers, characterized in that, include: The large tunnel is composed of multiple support units. Each support unit includes short anchor cables, steel mesh, long anchor cables, steel grid, and a reinforced concrete layer. The short anchor cables are anchored along their entire length to the shallow part of the surrounding rock. The steel mesh is laid on the surface of the surrounding rock and secured by the short anchor cables. The long anchor cables are prestressed anchor cables with full-length anchorage. Their anchorage section is connected to the surrounding rock, and the free end has a double-pallet structure. The steel grid is fixed by the double-pallet structure and connected to the steel mesh laid on the outside. The reinforced concrete layer is poured on the outside of the steel grid and steel mesh to form an integral support structure. The steel grid is composed of multiple grid arch frames connected by bolts. An arc-shaped washer is provided between the bolt head and nut at the connection of adjacent sections. The double-pallet structure includes a first pallet and a second pallet. The distance between the first pallet and the second pallet is 300mm. The second pallet is an arc structure with its bottom protruding towards the surrounding rock.

2. The deep high-stress large chamber pressure-relief combined support structure according to claim 1, characterized in that, The long anchor cable is also equipped with grouting holes and grout outlet holes.

3. A construction method for a pressure-yielding combined support structure for deep high-stress large chambers, based on the pressure-yielding combined support structure for deep high-stress large chambers as described in claim 2, comprising the following steps: S1: The main chamber will be excavated in 4 layers, with each layer having an excavation height of 5m, using smooth blasting technology; S2: After each layer of excavation is completed, short anchor cables are installed and steel mesh is laid to form the initial support; S3: Construction of long anchor cables, wherein the long anchor cables are Φ21.6×10000mm mining full-length anchored prestressed anchor cables, with a row spacing of 1.2m×2m, an anchor cable tray of 350×350×20mm, a preload of 200kN, an end anchorage length of not less than 2.0m, and the ends are anchored with resin anchoring agent. The free section is anchored with resin or mortar. Ten double-tray long anchor cables are evenly installed across the entire cross section, with a double tray spacing of 300mm. S4: Construction steel grating, steel grating spacing 1000mm, adjacent steel grating arch frames are connected by steel bars with a spacing not greater than 1000mm, steel grating is locked by double-pallet long anchor cables reserved in step S3 and connected to the steel mesh laid on the outside; S5: Repeat steps S2-S4 to complete all layer construction; S6: The reinforced concrete layers are poured from bottom to top to form an integral support structure.

4. The construction method for a pressure-bearing combined support system in a deep, high-stress large chamber according to claim 3, characterized in that, In step S2, the short anchor cable is made of Ф17.8×6000mm steel strand with a spacing of 1m×2m. The anchor cable tray is 300×300×16mm in size. The steel mesh is made of Ф10 round steel with a mesh spacing of 150×150mm.

5. The construction method for a pressure-bearing combined support system in a deep, high-stress large chamber according to claim 3, characterized in that, In step S3, the construction process of the full-length anchored prestressed anchor cable includes drilling positioning, drilling, hole inspection, resin filling, anchor cable insertion, pre-tensioning, and hole sealing grouting.

6. The construction method for a pressure-bearing combined support system in a deep, high-stress large chamber according to claim 3, characterized in that, After the long anchor cable construction in step S3 is completed, spray 30mm thick concrete to seal and protect the anchor cable.

7. The construction method for a pressure-bearing combined support system in a deep, high-stress large chamber according to claim 3, characterized in that, In step S5, when the steel grating is subjected to a large impact load, the arc-shaped gasket is compressed from an arc shape to a flat shape, thereby achieving the function of pressure absorption.

8. The construction method for a pressure-bearing combined support system in a deep, high-stress large chamber according to claim 3, characterized in that, In step S4, after the steel grating is completed, a trial assembly is performed. The perimeter assembly deviation is ±3cm, and the plane warping is less than 2cm.

9. The construction method for a pressure-bearing combined support system in a deep, high-stress large chamber according to claim 3, characterized in that, The gap between the tray and the rock surface is filled with grout during anchor cable grouting, forming a tight fit with the rock surface.

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