Prefabricated and assembled primary support structure for small-section mined tunnel

Abstract

The present invention discloses a prefabricated and assembled primary support structure for small-section mined tunnels, aiming to solve the technical problems of complex primary support steps, slow strength formation, and great harm to the human body caused by dust generated by shotcrete in small-section mined tunnels; this structure includes a number of assembly units arranged sequentially along the tunnel extension direction, and the assembly unit includes a crown, side plates, and an invert; the arch axis equations of the crown and the invert are: #imgabs0#, where y represents the longitudinal height of the arch, x represents the transverse span of the arch, f represents the rise of the arch, and l represents the span of the arch; and the ratio of the rise constant of the invert to the rise constant of the crown: C = (f 仰拱 / f 拱顶 ) takes a value of 0.3 to 0.5 to prevent foundation settlement and / or uplift deformation; the present invention is prefabricated outside the tunnel and assembled inside the tunnel, with a simple structure and fast construction speed, which can meet the construction conditions of small-section manually mined tunnels, quickly form a closed loop for the surrounding rock, enable the surrounding rock and the primary support to bear force together, and make the construction process green and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of traffic tunnel engineering, and particularly relates to a prefabricated and assembled primary support structure for a small-section mined tunnel. Background Art

[0002] The mined tunneling method is one of the main methods for urban underground engineering construction; it is applicable to: various formations with relatively small water content that are not suitable for open-cut construction, especially for urban areas where there are dense surface buildings, busy transportation, dense underground pipelines, and strict requirements for ground settlement, and it is more applicable for constructing shallowly buried underground structure projects. For soft formations with relatively large water content, this method can still be applicable after taking measures such as water blocking or dewatering; during the construction process of a mined tunnel, in accordance with the construction principle of the New Austrian Tunneling Method, various auxiliary measures are adopted during the construction process to reinforce the surrounding rock, fully mobilize the self-bearing capacity of the surrounding rock, and timely support and close the loop after excavation, so that it forms a combined support system with the surrounding rock, which is a comprehensive supporting construction technology for suppressing excessive deformation of the surrounding rock.

[0003] Currently, the mined tunneling method usually adopts the step-by-step excavation method. After the tunnel is excavated, concrete is initially sprayed immediately, and then steel frames, steel wire meshes, connecting bars, etc. are installed, and then sprayed concrete is used to close the loop.

[0004] However, during the process of implementing the technical solutions in the embodiments of the present application, the inventors of the present application found that the above-mentioned technology has at least the following technical problems: This primary support structure has a complex sequence, low efficiency of sprayed concrete, slow strength formation, and in addition, in a confined space, the generated dust is extremely harmful to the spraying personnel, especially more harmful to workers in small-section manually mined tunnels.

[0005] The information disclosed in this background art section is only used to deepen the understanding of the background art of the present disclosure, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0006] The inventors found through research that: when the arch axis equations of the crown and invert are , where y represents the longitudinal coordinate of the arch, x represents the transverse coordinate of the arch, f represents the arch rise constant, l represents the arch span constant, and the ratio of the arch rise constant of the invert to the arch rise constant of the crown: C = (f 仰拱 / f 拱顶 ) takes a value of 0.3 to 0.5; the compressive capacity of concrete is fully utilized to make the force of the primary support more reasonable and the support of the surrounding rock more stable.

[0007] In view of at least one of the above technical problems, the present disclosure provides a prefabricated and assembled primary support structure for a small-section mined tunnel, which simplifies the complicated procedures of the primary support and speeds up the construction process by prefabricating the inverted arch, the arch crown and the side plates.

[0008] According to one aspect of the present disclosure, there is provided a prefabricated and assembled primary support structure for a tunnel, including a plurality of assembled units arranged in sequence along the extension direction of the tunnel. The assembled unit includes an arch crown, a side plate and an inverted arch; the arch axis equation of the arch crown and / or the inverted arch is: , where y represents the longitudinal height of the arch, x represents the transverse span of the arch, f represents the arch rise constant, and l represents the span constant of the arch; and the ratio of the arch rise constant of the inverted arch to the arch rise constant of the arch crown: C = (f 仰拱 / f 拱顶 ) is 0.3 to 0.5 to prevent foundation settlement and / or uplift deformation.

[0009] In some embodiments of the present disclosure, the plate thicknesses of the inverted arch, the arch crown and the side plates are all 80 to 85 mm, the depth is 400 to 405 mm, and the concrete cover thickness is 15 to 20 mm.

[0010] In some embodiments of the present disclosure, the inverted arch, the arch crown and the side plates are all made of lightweight concrete, and the density grade of the lightweight concrete is 1500 kg / m 3 .

[0011] In some embodiments of the present disclosure, the inner sides of the ends of the inverted arch and the arch crown are provided with extended sections with a length of 40 to 45 mm and a thickness of 40 to 45 mm to prevent excessive deformation of the surrounding rock.

[0012] In some embodiments of the present disclosure, the maximum cross-sectional size of the tunnel is 2×2 m.

[0013] In some embodiments of the present disclosure, the inverted arch, the side plates and the arch crown are all prefabricated parts.

[0014] One or more technical solutions provided in the embodiments of the present application have at least any one of the following technical effects or advantages:

[0015] 1. Due to the adoption of the assembled arch crown, inverted arch and side plate structure, a rapid support system is realized during the small-section mined construction process to support and protect the surrounding rock, effectively solving the complexity of the existing technology in the installation steps of initially spraying concrete, and then installing steel frames, steel wire meshes, connecting bars, etc. during the surrounding rock support process, greatly accelerating the rate of surrounding rock support and improving the overall process of tunnel construction.

[0016] 2. Due to the adoption of the arch axis equation , the prefabrication of the invert, crown and side plates is realized, which solves the harm of dust generated by on-site shotcrete to personnel during the construction process, and improves the construction safety and environmental protection. Description of the Drawings

[0017] Figure 1 It is a three-dimensional structural schematic diagram of a prefabricated and assembled primary support structure in an embodiment of the present application.

[0018] Figure 2 It is a planar structural schematic diagram of a prefabricated and assembled primary support structure in an embodiment of the present application.

[0019] Figure 3 It is a schematic diagram of the selection of the arch axis of the prefabricated crown in an embodiment of the present application.

[0020] Figure 4 It is a schematic diagram of the construction cross-section in an embodiment of the present application.

[0021] In the above figures, 1, prefabricated crown; 2, prefabricated invert; 3, prefabricated side plate.

[0022] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", "vertical", "horizontal", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application. The "first", "second", etc. involved in the present application are used to distinguish the described objects and do not have any sequential or technical meanings. The "connection" and "coupling" involved in the present application, unless otherwise specified, both include direct and indirect connections (couplings).

[0023] By providing a prefabricated and assembled primary support structure for a small-section mined tunnel in an embodiment of the present application, the technical problems of complex construction procedures, low shotcrete efficiency, slow strength formation, and great harm to the physical health of construction personnel in the existing small-section mined primary support construction are solved.

[0024] The technical solution of the embodiment of the present application is to solve the above-mentioned existing technical problems, and the general idea is as follows:

[0025] Through the arch axis equation , where y represents the longitudinal coordinate of the arch, x represents the transverse coordinate of the arch, f represents the arch rise constant, l represents the arch span constant; and the ratio of the arch rise constant of the invert to the arch rise constant of the crown: C = (f 仰拱 / f 拱顶is 0.3 to 0.5, calculate the structural curves of the inverted arch and the crown, and prefabricate them in advance using lightweight concrete for backup.

[0026] Divide the construction team members into an excavation shift and a mucking shift, and divide the tunnel section into three parts: I, II, and III. During tunnel excavation, the excavation shift first excavates part II, and the mucking shift conducts mucking operations. After the excavation is completed, the mucking shift moves the side plates into the tunnel, and the excavation shift erects the side plates. Then the excavation shift excavates part I, and the mucking shift conducts mucking operations. After the excavation is completed, the mucking shift moves the crown into the tunnel, and the excavation shift erects the crown on the side plates. Finally, the excavation shift excavates part III, and the mucking shift backfills the inverted arch primary support of the previous cycle with muck. After the excavation is completed, the mucking shift moves the inverted arch into the tunnel, and the excavation shift installs the inverted arch under the side plates to close the surrounding rock into a ring. Repeating the above steps can complete the excavation and initial support of the tunnel.

[0027] To better understand the technical solution of this application, the above technical solution will be described in detail below in conjunction with the specification drawings and specific implementation manners.

[0028] Example 1

[0029] This example discloses a prefabricated and assembled primary support structure for a small-section mined tunnel. Refer to Figures 1 to 2 , including a number of assembly units arranged in sequence along the tunnel length direction to form an integral support structure;

[0030] The assembly unit includes a precast crown 1, precast side plates 3, and a precast inverted arch 2; in one assembly unit, there are two precast side plates 3 with the same structure and size, one precast crown 1, and one precast inverted arch 2; and the end parts of the precast side plates 3 are respectively matched with the precast crown 1 and the precast inverted arch 2 to support them respectively; the arch axis of the precast crown 1 is a parabola, and the arch axis of the precast inverted arch 2 is a reverse parabola (i.e., the opening direction of the parabola is opposite to that of the precast crown 1). The arch axis equation of the precast crown 1 is: , refer to Figure 3 , where y represents the longitudinal height of the arch, x represents the transverse span of the arch, f represents the rise constant of the arch, l represents the span constant of the arch, and the rise f and span l can be determined as known constants according to the design drawings before tunnel excavation; because the tensile strength of concrete is small, the above arch axis equation is used to prevent concrete from being damaged in tension and give full play to the compressive strength of concrete, reduce the amount of reinforcement, and reduce costs; the parabola equation of the arch axis of the precast inverted arch 2 is the same as that of the precast crown 1, except that the ratio of the rise constant of the inverted arch to the rise constant of the crown: C = (f 仰拱 / f 拱顶 ) is 0.3 to 0.5 to better solve the technical problems of foundation pit settlement and heave deformation.

[0031] An extended section with a length of 40 - 45 mm is provided inside the end of the precast arch crown 1 of the precast inverted arch 2, and the thickness is 40 - 45 mm. The purpose is to seal the surrounding rock, prevent excessive deformation of the surrounding rock, improve the overall bearing capacity of the structure, and increase the support resistance between the arch crown, the inverted arch and the side plates, preventing cutting failure caused by inward extrusion.

[0032] The plate thickness of the inverted arch, the arch crown and the side plates is all 80 - 85 mm, the depth is 400 - 405 mm, and the concrete cover thickness is 15 - 20 mm; all are made of lightweight concrete, and the density grade of the lightweight concrete is 1500 kg / m 3 , so that the largest block (precast arch crown 1, with a volume of 0.0832 m 3 ) of the precast assembled primary support structure with the largest tunnel section size (2×2 m) does not exceed 125 kg.

[0033] The precast inverted arch 2, the precast arch crown 1 and the precast side plates 3 are all precast components. According to the tunnel design structure dimensions and the corresponding arch axis equation in advance, the structures of the arch crown, the inverted arch and the side plates are obtained and precast outside the tunnel. When excavation is carried out, direct assembly can be carried out, shortening the support time and improving the tunneling efficiency.

[0034] During the tunnel excavation process, the construction team personnel are divided into an excavation shift and a mucking shift. The tunnel cross-section is divided into three parts: I, II, and III. See Figure 4 . During tunnel excavation, the excavation shift first excavates II, and the mucking shift carries out mucking operations. After the excavation is completed, the mucking shift moves the side plates into the tunnel, and the excavation shift erects the side plates. Then the excavation shift excavates I, and the mucking shift carries out mucking operations. After the excavation is completed, the mucking shift moves the arch crown into the tunnel, and the excavation shift erects the arch crown on the side plates. Finally, the excavation shift excavates III, and the mucking shift backfills the muck into the inverted arch primary support of the previous cycle. After the excavation is completed, the mucking shift moves the inverted arch into the tunnel, and the excavation shift installs the inverted arch under the side plates to close the loop for the surrounding rock. Repeating the above steps can complete the tunnel excavation and primary support.

[0035] Although some preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0036] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of this application and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A prefabricated and assembled primary support structure for a tunnel, characterized in that, It includes a number of assembled units arranged in sequence along the tunnel extension direction. The assembled unit includes a vault, side plates and an invert; the arch axis equations of the vault and / or the invert are: , where y represents the longitudinal height of the arch, x represents the transverse span of the arch, f represents the rise constant of the arch, l represents the span constant of the arch; and the ratio of the rise constant of the invert to the rise constant of the vault: C = (f 仰拱 / f 拱顶 ) takes a value of 0.3 to 0.5 to prevent foundation settlement and / or heave deformation.

2. The prefabricated and assembled initial support structure for a tunnel according to claim 1, characterized in that, The thickness of the invert, vault and side plates is 80 - 85 mm, the depth is 400 - 405 mm, and the concrete cover thickness is 15 - 20 mm.

3. The prefabricated and assembled initial support structure for a tunnel according to claim 1, characterized in that, The inverted arch, arch crown and side plates are all made of lightweight concrete, and the density grade of the lightweight concrete is 1500 kg / m 3 .

4. The prefabricated and assembled initial support structure for a tunnel according to claim 1, wherein The inner sides of the ends of the invert and vault are provided with extended sections that are 40 - 45 mm long and 40 - 45 mm thick to prevent excessive deformation of the surrounding rock.

5. The prefabricated and assembled initial support structure for a tunnel according to claim 1, characterized in that, The maximum cross-sectional dimension of the tunnel is 2×2 m.

6. The prefabricated and assembled initial support structure for a tunnel according to claim 1, wherein The invert, side plates and vault are all precast components.

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