A method for supporting construction of a chamber overbreak

Abstract

This invention provides a construction method for over-excavation support in a tunnel. The method includes: constructing a steel arch frame along the tunnel wall; determining the placement location of the filling component based on the geological conditions of the tunnel and the over-excavated area above the steel arch frame; measuring the radial distance at the placement location of the filling component; selecting airbags and fiberglass cloth; applying epoxy resin to the surface of the fiberglass cloth; wrapping multiple layers of fiberglass cloth around the surface of the airbags; placing the airbags in the gaps; inflating the airbags to cause them to expand and slide between the layers of fiberglass cloth wrapped around their surfaces; stopping inflation and maintaining the internal air pressure of the airbags when the fiberglass cloth is in close contact with the surrounding rock; after the epoxy resin cures, it forms a closed ring-shaped filling component together with the fiberglass cloth; detaching the airbags from the filling component and removing them, leaving the filling component in the gaps to form local support for the over-excavated area. This invention solves the problem that due to over-excavation of the tunnel, the surrounding rock above the steel arch frame is suspended, and the support structure cannot form effective contact support with the surrounding rock.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering support technology, and in particular to a method for over-excavation support construction in tunnels. Background Technology

[0002] Drill-and-blast method is widely used in tunnel excavation due to its mature technology, relatively low cost, and ability to create chambers of various shapes and sizes. However, in practical construction, a significant engineering contradiction has been found between the drilling speed and the blasting accuracy of the chamber: if drilling efficiency is prioritized, the blasting accuracy will be greatly reduced, leading to severe over-excavation of the chamber cross-section. Statistical data shows that when the over-excavation exceeds 15% of the design cross-sectional area, a 20-50cm gap will form between the steel arch and the surrounding rock, preventing the support structure from forming effective contact support with the surrounding rock. Current technologies mostly address over-excavation by backfilling the over-excavated gap above the steel arch with concrete.

[0003] For example, a concrete filling device for tunnel steel support, disclosed in publication number CN111502702A, involves an airbag on a steel arch frame to seal the gap between the steel arch frame and the surrounding rock. The airbag has several grouting holes, through which concrete is injected into the grouting area. After the concrete hardens, the airbag is deflated and disassembled, completing the concrete filling of the gap between the steel arch frame and the surrounding rock. This method can effectively fill the over-excavated gap between the steel arch frame and the surrounding rock with concrete, solving the problem of the support structure not forming effective contact support with the surrounding rock. However, the concrete grouting operation has a long construction period, requires a large amount of consumable materials for the support, and the filled concrete is prone to cracking and spalling during the tunnel support period.

[0004] For example, a tunnel support structure and method disclosed in publication number CN109578012A uses steel arch frames and airbags installed along the surface of the surrounding rock for rock support. The inflated airbags fill the gap between the steel arch frames and the surrounding rock. While this method effectively fills the over-excavated voids in the tunnel using inflated airbags, the airbags have high deformability and low stiffness, making them unable to withstand significant surrounding rock pressure. Therefore, they cannot restrain the deformation of the surrounding rock, easily leading to support failure. Furthermore, after inflation, the airbags come into direct contact with the over-excavated area of ​​the surrounding rock, causing friction between the rock and the airbag surface. This can easily lead to localized thinning of the airbags, resulting in uneven air pressure, decreased airtightness, and support failure. Summary of the Invention

[0005] The purpose of this invention is to provide a construction method for over-excavation support in a chamber, which is applicable to rapid temporary support in over-excavation areas of a chamber.

[0006] The technical solution of this invention is: a method for constructing over-excavation support in a chamber, comprising:

[0007] Step 1: Install and build steel arch frames along the rock wall of the chamber, with multiple steel arch frames installed at intervals along the longitudinal direction of the chamber;

[0008] Step 2: Determine the location of the filling component based on the geological conditions of the chamber and the over-excavated area above the steel arch; measure the radial distance between the surrounding rock and the steel arch at the location of the filling component.

[0009] Step 3: Select the airbag and fiberglass cloth based on the radial distance measured in Step 2; apply the stirred epoxy resin to the surface of the fiberglass cloth.

[0010] Step 4: Wrap multiple layers of epoxy resin-coated fiberglass cloth around the outer surface of the airbag.

[0011] Step 5: Place the airbag from Step 4 into the gap between the surrounding rock and the steel arch in the corresponding over-excavated area.

[0012] Step 6: Inflate the airbag to make it expand, causing the multiple layers of fiberglass cloth wrapped around its surface to slip between layers; when the fiberglass cloth is in close contact with the surrounding rock, stop inflating the airbag and maintain the air pressure inside the airbag.

[0013] Step 7: Maintain the air pressure inside the airbag for a period of time to allow the epoxy resin to cure and form a closed-loop resin-based glass fiber filling component together with the glass fiber cloth.

[0014] Step 8: Release the gas inside the airbag to detach it from the filling component, remove the airbag, and leave the filling component in the gap between the steel arch and the surrounding rock in the over-excavated area to form local support for the over-excavated area.

[0015] In the above solution, resin-based glass fiber components with stronger toughness than airbags are used to fill the over-excavation gaps, which can avoid problems such as local wear of airbags and uneven air pressure leading to support failure. At the same time, airbags can be quickly (about 0.5 hours) recovered and reused, making them more suitable for rapid temporary support in over-excavated areas of chambers.

[0016] Preferably, when selecting the airbag, its diameter before expansion is smaller than the radial distance between the surrounding rock of the over-excavated area and the steel arch frame, so that the airbag can be placed into the gap after being wrapped with fiberglass cloth.

[0017] Preferably, the inflated airbag causes the fiberglass cloth wrapped around its surface to adhere tightly to the irregular surface of the surrounding rock in the over-excavated area.

[0018] Preferably, in step six, the air pressure inside the airbag is maintained for 10-20 minutes.

[0019] Preferably, in step three, the length of the fiberglass cloth is at least six times the measured radial distance, and the width of the fiberglass cloth is greater than the width of the steel arch and less than the length of the airbag.

[0020] Preferably, the epoxy resin is an A / B component resin, which can undergo interlayer slippage with the glass fiber cloth before curing; the curing time of the epoxy resin is 20-40 minutes.

[0021] Preferably, the fiberglass cloth can absorb epoxy resin, and after the epoxy resin is cured, the fiberglass cloth forms a filling component that can withstand the pressure of the surrounding rock and resist the deformation of the surrounding rock.

[0022] Preferably, in step four, rubber cable ties are used to temporarily secure the fiberglass cloth wrapped around the airbag.

[0023] Preferably, in step five, the airbag is connected to the air compressor via a hose; in step six, the air compressor is started to inflate the airbag.

[0024] Preferably, the method for constructing over-excavation support for the chamber further includes step nine, repeating steps two through eight above the steel arch frame in other over-excavated areas until the support for the over-excavated open area of ​​the chamber is completed.

[0025] Compared with related technologies, the beneficial effects of the present invention are as follows:

[0026] I. This invention effectively transmits the surrounding rock pressure to the steel arch frame through the filling components, solving the problem that due to over-excavation of the chamber, the surrounding rock above the steel arch frame is suspended, and the support structure cannot form effective contact support with the surrounding rock.

[0027] Second, the resin-based glass fiber support structure used in this invention has high strength, good rigidity, easy construction quality assurance, short resin curing time, and high construction efficiency, which can effectively achieve rapid and effective support for local and precise locations in the over-excavated area of ​​the chamber.

[0028] III. This invention employs a short-time, rapid-curing epoxy resin coating on fiberglass cloth, which is then wound around the surface of the airbag. During the inflation and expansion of the airbag, the fiberglass cloth wound around its surface stretches and expands, undergoes interlayer sliding, and maintains internal pressure for a period of time, providing support for the fiberglass cloth. After the epoxy resin cures to form an irregular cylindrical resin-based fiberglass-filled component, the gas inside the airbag can be released, and the airbag can be removed for reuse. The airbag has a short service life, high reusability, and can quickly and efficiently complete support work in a short time, effectively reducing support costs.

[0029] Fourth, the resin-based glass fiber filling component in this invention is a rapidly deployable filling component. It can quickly complete the support of the over-excavated area of ​​the chamber during the initial stage of chamber excavation when the surrounding rock stress is released and the deformation is large. During the support period, the component can withstand large surrounding rock pressure and resist surrounding rock deformation. While maximizing the self-supporting capacity of the chamber surrounding rock, it can improve the support quality and ensure the stability of the support system.

[0030] Fifth, unlike existing technologies that rely on airbags to directly contact and support the surrounding rock, this invention uses resin-based glass fiber components, which are more resilient than airbags, to fill the over-excavation gaps, thus avoiding problems such as localized wear of airbags and uneven air pressure that could lead to support failure. Attached Figure Description

[0031] Figure 1 A schematic diagram of the steel arch frame to be erected inside the tunnel;

[0032] Figure 2 A schematic diagram for cutting fiberglass cloth;

[0033] Figure 3 This is a schematic diagram of applying epoxy resin to the surface of fiberglass cloth.

[0034] Figure 4 A schematic diagram of wrapping fiberglass cloth around the surface of an airbag;

[0035] Figure 5 A schematic diagram for the installation of the infill component;

[0036] Figure 6 A schematic diagram showing the interlayer slippage of the fiberglass cloth on the surface of the inflated airbag;

[0037] Figure 7 This is a schematic diagram of the overall support structure after construction.

[0038] Figure 8 The flowchart is for the construction method of over-excavation support for the chamber provided by the present invention.

[0039] In the attached diagram: 1. Steel arch frame; 2. Surrounding rock; 3. Airbag; 4. Fiberglass cloth; 5. Rubber cable ties; 6. Epoxy resin; 7. Hoses; 8. Air compressor; 9. Filling components. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. For ease of description, the terms "upper," "lower," "left," and "right" used below only indicate that they correspond to the upper, lower, left, and right directions in the accompanying drawings and do not limit the structure.

[0041] like Figure 8As shown, the construction method for over-excavation support of a chamber provided in this embodiment includes the following steps:

[0042] S1, as Figure 1 As shown, multiple steel arch frames 1 are erected at intervals along the longitudinal direction of the chamber, and the steel arch frames 1 are adjusted to fit as closely as possible to the rock wall of the surrounding rock 2.

[0043] S2. Determine the location of the filling component 9 (i.e., the location requiring support) based on the geological conditions of the chamber and the size of the over-excavated area above the steel arch frame 1. Measure the radial distance between the surrounding rock 2 and the steel arch frame 1 at the location requiring support.

[0044] S3. Based on the measured radial distance, select the airbag 3 and fiberglass cloth 4. The airbag 3 is made of rubber, giving it good inflation and expansion capabilities, surface deformation performance, and gas sealing performance. This allows its diameter to expand several times after being filled with high-pressure gas, and ensures that the fiberglass cloth 4 wrapped around its surface can tightly adhere to the surrounding rock surface of the irregular over-excavated area after inflation. It also maintains its internal air pressure after inflation stops. Before inflation, the diameter of the airbag 3 is smaller than the radial distance between the surrounding rock 2 in the over-excavated area and the steel arch 1, allowing it to be placed into this gap after the fiberglass cloth 4 is wrapped around it.

[0045] The fiberglass cloth 4 is rectangular, and its length is at least six times the radial distance of the measured gap. The width of the fiberglass cloth 4 is greater than the width of the steel arch 1 and less than the length of the airbag 3. The length of the fiberglass cloth 4 is determined by the geological conditions of the over-excavated area above the steel arch 1 and the radial distance of the over-excavated area. The length of the fiberglass cloth 4 needs to ensure that, although interlayer slippage occurs when the airbag 3 is inflated, the fiberglass cloth 4 wrapped around the surface of the airbag 3 can still form a closed ring after the airbag 3 is inflated. If the geological conditions of the area are poor, the length of the fiberglass cloth 4 can be increased to adjust the number of layers of winding, ensuring that the formed filling component has a good support effect.

[0046] Calculate the length of fiberglass cloth 4 based on the radial distance and cut it accordingly (e.g.) Figure 2 As shown). Mix the A / B components of epoxy resin in a 1:2 ratio and stir until homogeneous. Apply the stirred epoxy resin 6 to the surface of the fiberglass cloth 4 (as shown). Figure 3 (As shown). The application rate is 250-400g / ㎡.

[0047] The A / B component ratio of the epoxy resin 6 needs to allow for a certain curing time. This time is sufficient to prevent curing during the inflation of the airbag 3, allowing the fiberglass cloth 4 to slip between layers as the airbag 3 expands. However, once the fiberglass cloth is tightly bonded to the surrounding rock surface and inflation stops, the epoxy resin 6 can cure rapidly. The curing time is approximately half an hour.

[0048] The fiberglass cloth 4 can absorb the coated epoxy resin 6 well. After the epoxy resin 6 is cured, it can form a circular or elliptical resin-based fiberglass filled component 9 with high strength and good rigidity, which can withstand greater surrounding rock pressure and has a better ability to resist deformation of the surrounding rock 2.

[0049] S4, as Figure 4 As shown, multiple layers of fiberglass cloth 4 coated with epoxy resin 6 are wrapped around the outer surface of the airbag 3 and temporarily secured with rubber cable ties 5, which are elastically expandable and contractible. During wrapping, the short sides of the rectangular fiberglass cloth 4 are laid out along the length of the airbag 3, and the long sides of the rectangular fiberglass cloth 4 are wrapped around the side of the airbag 3. The ends of the fiberglass cloth 4 are adhered to the previous layer of fiberglass cloth 4. A PE film with low moisture permeability can be wrapped around the airbag 3 as a release liner before the fiberglass cloth 4 is wrapped around it, making it easier for the airbag 3 to detach from the fiberglass cloth 4.

[0050] S5, such as Figure 5 As shown, the airbag 3 from step S4 is placed in the gap between the steel arch frame 1 and the surrounding rock 2 in the corresponding over-excavation area, with the length direction of the airbag 3 aligned with the longitudinal direction of the chamber and perpendicular to the vertical plane formed by the steel arch frame 1. The airbag 3 is then connected to the air compressor 8 via a hose 7.

[0051] S6, turn on the air compressor 8 to inflate the airbag 3, causing it to expand slowly. The slowly expanding airbag 3 causes the multiple layers of fiberglass cloth 4 wrapped around its surface to stretch and expand slowly, resulting in interlayer slippage. The beginning and end ends of the fiberglass cloth 4 are displaced by a certain distance due to this interlayer slippage (e.g., ...). Figure 6 (As shown).

[0052] As the airbag 3 inflates, the multi-layered fiberglass cloth 4 slowly expands and stretches, causing interlayer slippage. The beginning and end of the fiberglass cloth 4 are displaced by a certain distance due to this interlayer slippage. Although the interlayer slippage of the fiberglass cloth 4 slightly reduces the number of winding layers, the length of the long strip of fiberglass cloth is at least six times the measured radial distance. This length ensures that the beginning and end of the fiberglass cloth 4 still overlap after the interlayer slippage, forming a closed ring-shaped filling component 9.

[0053] Once the fiberglass cloth 4 is tightly attached to the surrounding rock 2, stop inflating the airbag 3 and maintain the internal air pressure of the airbag 3 for a period of time.

[0054] S7, maintain the internal air pressure of the airbag 3 for a period of time (e.g., 15 minutes), and after the epoxy resin 6 has cured, it will form the filling component 9 together with the fiberglass cloth 4 (e.g., Figure 7 (As shown).

[0055] S8, release the gas inside the airbag 3 to shrink it. The shrunken airbag 3 detaches from the filling component 9. Remove the airbag 3 for reuse. Leave the filling component 9 in the gap between the steel arch frame 1 and the surrounding rock 2 in the over-excavated area to form local support for the over-excavated area.

[0056] S9, repeat steps two through eight above the steel arch frame 1 in other over-excavated areas until the support of the over-excavated exposed area of ​​the chamber is completed (e.g., Figure 7 (As shown).

[0057] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for supporting construction of a chamber overbreak, characterized in that, include: Step 1: Construct steel arch frames (1) along the rock wall of the chamber, with multiple steel arch frames (1) installed at intervals along the longitudinal direction of the chamber; Step 2: Based on the geological conditions of the chamber and the over-excavated area above the steel arch frame (1), determine the location of the filling component; measure the radial distance between the surrounding rock (2) and the steel arch frame (1) at the location of the filling component; Step 3: Select the airbag (3) and fiberglass cloth (4) based on the radial distance measured in Step 2; apply the stirred epoxy resin (6) to the surface of the fiberglass cloth (4); Step 4: Wrap multiple layers of glass fiber cloth (4) coated with epoxy resin (6) around the outer surface of the airbag (3); the glass fiber cloth (4) can absorb epoxy resin (6), and after the epoxy resin (6) is cured, the glass fiber cloth (4) forms a filling component (9) that can withstand the pressure of the surrounding rock (2) and resist the deformation of the surrounding rock (2). Step 5: Place the airbag (3) from step 4 into the gap between the surrounding rock (2) and the steel arch frame (1) in the over-excavated area at the corresponding location; Step 6: Inflate the airbag (3) to make it expand, causing the multi-layered glass fiber cloth (4) wrapped around its surface to slip between layers; when the glass fiber cloth (4) is in close contact with the surrounding rock (2), stop inflating the airbag (3) and maintain the air pressure inside the airbag (3); Step 7: Maintain the internal air pressure of the airbag (3) for a period of time so that the epoxy resin can be cured and together with the glass fiber cloth (4) form a closed ring-shaped resin-based glass fiber filling component (9). Step 8: Release the gas in the airbag (3) to separate the airbag (3) from the filling component (9), remove the airbag (3), and leave the filling component (9) in the gap between the steel arch frame (1) and the surrounding rock (2) to form local support for the over-excavated area.

2. The method for constructing over-excavation support for a chamber according to claim 1, characterized in that, When selecting the airbag (3), its diameter before expansion is smaller than the radial distance between the surrounding rock (2) of the over-excavated area and the steel arch frame (1), so that the airbag (3) can be placed into the gap after being wrapped with glass fiber cloth (4).

3. The method for constructing over-excavation support for a chamber according to claim 1, characterized in that, The inflated airbag (3) causes the fiberglass cloth (4) wrapped around its surface to adhere tightly to the irregular surface of the surrounding rock (2) in the over-excavated area.

4. The method for constructing over-excavation support for a chamber according to claim 1, characterized in that, In step six, maintain the internal air pressure of the airbag (3) for 10-20 minutes.

5. The method for constructing over-excavation support for a chamber according to claim 1, characterized in that, In step three, the length of the fiberglass cloth (4) is at least six times the measured radial distance, and the width of the fiberglass cloth (4) is greater than the width of the steel arch frame (1) and less than the length of the airbag (3).

6. The method for constructing over-excavation support for a chamber according to claim 1, characterized in that, The epoxy resin (6) is an A / B component resin, which can undergo interlayer slippage with the glass fiber cloth (4) before curing; the curing time of the epoxy resin (6) is 20-40 min.

7. The method for constructing over-excavation support for a chamber according to claim 1, characterized in that, In step four, the fiberglass cloth (4) is temporarily fixed to the airbag (3) by wrapping it with rubber cable ties (5).

8. The method for constructing over-excavation support for a chamber according to claim 1, characterized in that, In step five, the airbag (3) is connected to the air compressor (8) through the hose (7); in step six, the air compressor (8) is started to inflate the airbag (3).

9. The method for constructing over-excavation support for a chamber according to any one of claims 1-8, characterized in that, It also includes step nine, repeating steps two through eight above the steel arch frame (1) in other over-excavated areas until the support of the over-excavated open area of ​​the chamber is completed.

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