A kind of off-wall energy-absorbing lining composite structure suitable for high ground stress large deformation tunnel

Abstract

The application discloses a kind of off-wall energy-absorbing lining composite structures suitable for high ground stress large deformation tunnel.The composite structure includes initial support layer, basalt fiber composite foam filling layer and secondary lining layer; during the excavation of high ground stress large deformation tunnel, a layer of concrete is sprayed on the surface of surrounding rock, and the initial support structure is formed after the concrete solidifies; under the premise of ensuring the clearance of tunnel, secondary lining is carried out on the outside of initial support, and off-wall lining space is formed between secondary lining and initial support; basalt fiber composite foam is used to fill the off-wall lining space, and basalt fiber composite foam filling layer is formed between initial support and secondary lining.The application provides an off-wall energy-absorbing lining composite structure suitable for high ground stress large deformation tunnel, which has low construction difficulty, is green and environmentally friendly, has low cost, is easy to expand, and can effectively ensure the construction quality and safety of high ground stress large deformation tunnel.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a detached energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation. Background Technology

[0002] With the continuous development of my country's transportation infrastructure, there is an increasing number of long tunnel projects being constructed in areas with harsh geological environments, high ground stress, and weak surrounding rock. Currently, facing the problem of large deformation in high ground stress tunnels, conventional and effective deformation control measures include increasing the excavation radius and steel frame curvature at the sidewalls to improve the structural stress state and resist horizontal stress in the surrounding rock. Meanwhile, in the large deformation sections, a "circular" or "elliptical" cross-section is typically used. This structural form is dominated by compressive stress, making it less prone to stress concentration, and the overall stress distribution of the cross-section is better, which is beneficial to the stability of the surrounding rock. However, the aforementioned "circular" cross-section also has many disadvantages, such as low space utilization, high construction costs, the need to re-fabricate the lining formwork trolley and the difficulty of assembling it inside the tunnel, and the size effect of surrounding rock deformation.

[0003] Based on the above issues, considering structural stress and construction costs, and taking into account the "circular" and "elliptical" cross-sectional shapes of different large deformation sections of the tunnel, and under the premise of ensuring tunnel clearance, a uniform "elliptical" secondary lining layer is constructed for all large deformation sections of the tunnel. A detached lining space is formed between the secondary lining layer and the initial support layer. The detached lining space is filled with a basalt fiber composite foam filling layer, so that a lightweight, plastic, and energy-absorbing basalt fiber composite foam filling layer is formed between the initial support layer and the secondary lining layer, thereby improving structural stress and effectively controlling tunnel deformation. Summary of the Invention

[0004] This invention addresses the shortcomings of existing large deformation section construction schemes by disclosing a detached energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation. The purpose of this invention is to provide a detached energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation, characterized by low construction complexity, ease of construction, environmental friendliness, low cost, easy scalability, and effective assurance of construction quality and safety.

[0005] This invention is achieved through the following technical solution:

[0006] A detached energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation is characterized in that: the composite structure includes an initial support layer, a basalt fiber composite foam filling layer, and a secondary lining layer.

[0007] During the excavation of tunnels with high ground stress and large deformation, a layer of concrete is sprayed onto the surface of the surrounding rock, and the initial support structure is formed after the concrete solidifies.

[0008] Under the premise of ensuring tunnel clearance, secondary lining is carried out on the outside of the initial support, and a space for detached lining is formed between the secondary lining and the initial support.

[0009] Basalt fiber composite foam is used to fill the space of the detached lining, forming a basalt fiber composite foam filling layer between the initial support and the secondary lining.

[0010] Furthermore, the basalt fiber composite foam is made by mixing 10-25 wt% fly ash, 0.1-3 wt% basalt fiber, and the balance polyurethane rigid foam. The polyurethane rigid foam is a mixture of polyether and polymeric MDI. The fly ash is Class II fly ash, and the basalt fiber has a length of 10-20 mm.

[0011] Furthermore, the initial support layer uses sprayed C30 early high-strength fiber concrete. The concrete thickness is 25-27cm for level 1, 2 and 3 deformations, and an additional 25-27cm plus 21cm is sprayed for level 4 extremely severe deformation.

[0012] The thickness of the basalt fiber composite foam filling layer is 10-15cm for level 1, 15-20cm for level 2, and 20-30cm for level 3; for level 4 extremely severe deformation, two layers of basalt fiber composite foam filling layer are set, with the first layer being 20-30cm and the second layer being 10cm.

[0013] The secondary lining layer adopts a cast-in-place reinforced concrete structure with a thickness of 45cm for Grade I, 50cm for Grade II, 55cm for Grade III, and 60cm for Grade IV.

[0014] In the process of excavating a tunnel with high ground stress and large deformation, this invention involves spraying a layer of concrete onto the surrounding rock, which solidifies to form the initial support structure. While ensuring tunnel clearance, a secondary lining is constructed on the outside of the initial support structure, creating a space between the secondary lining and the initial support structure that is detached from the wall. This space is then filled with basalt fiber composite foam, resulting in a lightweight, malleable, and energy-absorbing basalt fiber composite foam filling layer between the initial support and the secondary lining. This improves structural stress and effectively controls tunnel deformation.

[0015] Faced with the problem of large deformation in tunnels under high ground stress, the conventional and effective deformation control measures are to increase the excavation radius and steel frame curvature of the sidewalls, improve the stress state of the structure, and resist the horizontal stress of the surrounding rock. However, this method also has many disadvantages, such as low space utilization, high construction cost, the need to remake the lining formwork trolley and the difficulty of assembling it inside the tunnel, and the size effect of the surrounding rock deformation.

[0016] This invention aims to improve structural stress and effectively control tunnel deformation by adding a lightweight, malleable, and energy-absorbing basalt fiber composite foam filling layer between the traditional secondary lining and primary support structure in the tunnel's high deformation section, while ensuring tunnel clearance. Furthermore, the basalt fiber composite foam is a high-performance composite material prepared from rigid polyurethane foam, fly ash, and basalt fiber. It overcomes the shortcomings of rigid polyurethane foam, such as low strength, poor toughness, and low energy absorption efficiency, and possesses excellent waterproof, thermal insulation, and corrosion resistance properties. It also boasts advantages such as simple and easy manufacturing process, environmental friendliness, low cost, and easy scalability.

[0017] This invention addresses the challenges of constructing tunnels under high ground stress and large deformation by providing a detached energy-absorbing lining composite structure suitable for tunnels under high ground stress and large deformation. This structure is characterized by low construction complexity, ease of construction, environmental friendliness, low cost, easy scalability, and effective assurance of construction quality and safety. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention.

[0019] In the diagram: 1-Initial support layer, 2-Basalt fiber composite foam filling layer, 3-Secondary lining layer. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments. These specific embodiments are further explanations of the principles of the present invention and are not intended to limit the present invention in any way. Any technology that is the same as or similar to the present invention does not exceed the scope of protection of the present invention.

[0021] Refer to the attached diagram.

[0022] As shown in the figure, the present invention provides a detached energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation, specifically comprising: an initial support layer 1, a basalt fiber composite foam filling layer 2, and a secondary lining layer 3.

[0023] During the excavation of a high-stress, large-deformation tunnel, a layer of concrete is sprayed onto the surrounding rock. After the concrete solidifies, the initial support layer 1 is formed. Under the premise of ensuring tunnel clearance, a secondary lining layer 3 is constructed on the outside of the initial support layer 1, and a space between the secondary lining layer 3 and the initial support layer 1 is formed. The space between the secondary support layer 1 and the secondary lining layer 3 is filled with a basalt fiber composite foam filling layer 2, which has lightweight, plastic, and energy-absorbing properties, thereby improving the structural stress and effectively controlling tunnel deformation.

[0024] The specific construction process includes the following steps:

[0025] First, based on the main influencing factors of large deformation of soft rock, such as geological structure, lithology, rock hardness, rock layer thickness, rock mass integrity, rock layer occurrence, hydrogeological conditions, initial geostress state, adverse geology, and special soil and rock conditions, as well as the characteristics and deformation features of the surrounding rock at the tunnel face during the construction stage, the large deformation level of different large deformation sections of the tunnel is determined.

[0026] Secondly, based on the different large deformation levels of the tunnel as determined above, as well as the survey and design data including surrounding rock parameters and stress field magnitude, the parameters of the tunnel excavation outline, initial support layer 1, and secondary lining layer 3 are determined.

[0027] For high ground stress and large deformation tunnels, the control parameters of each layer of the pre-designed detached energy-absorbing lining composite structure under various levels of deformation potential are detailed in Table 1 below. Specific measures should be determined comprehensively based on the surrounding rock conditions, combined with field tests, theoretical analysis, and engineering analogies.

[0028] Table 1. Parameters of Composite Structure for Detached Energy-Absorbing Liner in High-Stress, Large-Deformation Tunnels

[0029]

[0030] During tunnel excavation, a layer of concrete is sprayed onto the surrounding rock. After the concrete solidifies, an initial support layer 1 is formed. A secondary lining layer 3 is then constructed on the outside of the initial support layer, and a space for detached lining is formed between the secondary lining layer 3 and the initial support layer 1.

[0031] The basalt fiber composite foam filling layer 2 is used to fill the space of the detached lining, so that a basalt fiber composite foam filling layer 2 with lightweight, plastic and energy-absorbing properties is formed between the initial support layer 1 and the secondary lining layer 3, so as to improve the structural stress and effectively control the tunnel deformation. In addition, the basalt fiber composite foam filling layer 2 also has excellent waterproof, heat insulation and anti-corrosion properties.

[0032] The basalt fiber composite foam filling layer 2 is a high-performance composite material prepared from polyurethane rigid foam, fly ash, and basalt fiber. It improves the shortcomings of polyurethane rigid foam such as low strength, poor toughness, and low energy absorption efficiency. This material has many advantages such as simple and easy process, green and environmentally friendly, low cost, and easy expansion.

[0033] The basalt fiber composite foam filling layer 2 has the following composition: 10-25 wt% fly ash, 0.1-3 wt% basalt fiber, and the remainder is rigid polyurethane foam.

[0034] Rigid polyurethane foam is a mixture of polyether and polymeric MDI (diphenylmethane diisocyanate), where the former is the blowing agent and the latter is the curing agent.

[0035] The fly ash is Class II fly ash, and the basalt fiber length is 10-20mm.

[0036] This invention's composite structure features low construction complexity, ease of construction, environmental friendliness, low cost, easy scalability, and effective assurance of construction quality and safety. During the excavation of tunnels with high ground stress and large deformation, a layer of concrete is sprayed onto the surrounding rock, forming an initial support layer after solidification. Considering structural stress and construction costs, based on the "circular" and "elliptical" cross-sectional shapes of different large deformation sections of the tunnel, and while ensuring tunnel clearance, an "elliptical" secondary lining layer is uniformly constructed on the outside of the initial support layer, creating a space between the secondary lining layer and the initial support layer. A basalt fiber composite foam filling layer is used to fill this space, forming a lightweight, plastic, and energy-absorbing basalt fiber composite foam filling layer between the initial support layer and the secondary lining layer. This improves structural stress and effectively controls tunnel deformation.

Claims

1. A detached energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation, characterized in that: The composite structure includes an initial support layer, a basalt fiber composite foam filling layer, and a secondary lining layer; During the excavation of tunnels with high ground stress and large deformation, a layer of concrete is sprayed onto the surface of the surrounding rock, and the initial support layer is formed after the concrete solidifies. Under the premise of ensuring tunnel clearance, secondary lining is carried out on the outside of the initial support layer, and a detached lining space is formed between the secondary lining layer and the initial support layer. Basalt fiber composite foam is used to fill the space of the detached lining, forming a basalt fiber composite foam filling layer between the initial support layer and the secondary lining layer; the basalt fiber composite foam is made by mixing 10-25wt% fly ash, 0.1-3wt% basalt fiber, and the balance polyurethane rigid foam; the polyurethane rigid foam is a mixture of polyether and polymeric MDI.

2. The detached-wall energy-absorbing lining composite structure for tunnels with high ground stress and large deformation as described in claim 1, characterized in that: The fly ash is Class II fly ash, and the basalt fiber length is 10-20mm.

3. The detached-wall energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation according to claim 1 or 2, characterized in that: The initial support layer is made of sprayed C30 early high-strength fiber concrete. The concrete thickness is 25-27cm for level 1, 2 and 3 deformations. For level 4 extremely severe deformation, the concrete thickness is increased to 25-27cm plus 21cm.

4. The detached-wall energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation according to claim 1 or 2, characterized in that: The thickness of the basalt fiber composite foam filling layer is 10-15cm for level 1, 15-20cm for level 2, and 20-30cm for level 3; for level 4 extremely severe deformation, two layers of basalt fiber composite foam filling layer are set, with the first layer being 20-30cm and the second layer being 10cm.

5. The detached-wall energy-absorbing lining composite structure suitable for tunnels with high ground stress and large deformation according to claim 1 or 2, characterized in that: The secondary lining layer adopts a cast-in-place reinforced concrete structure with a thickness of 45cm for Grade I, 50cm for Grade II, 55cm for Grade III, and 60cm for Grade IV.

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