A method for constructing a large-span column-free underground cavern using a super-strong prestressed structure

Abstract

The present invention provides a method for constructing a large-span column-free underground cavern using a super-strong prestressed structure, wherein the large-section excavation is divided into a small-section excavation, and the overall area is divided into a spandrel excavation area, a middle excavation area, and a side excavation area; first, the left spandrel area is excavated, a middle rock column is reserved, and the upper area of ​​the middle rock column is reinforced by grouting. After the deformation of the cavern is stable, the middle rock column is excavated, a longitudinal bearing beam is erected, and a super-strong prestressed anchor cable is installed; the middle spandrel area and the right spandrel area are excavated in sequence; then, the left middle area of ​​the cavern is excavated, ordinary prestressed anchor cables are installed at the tunnel vault, and then radial system anchor rods are installed at the vault, and anchor spraying support is performed, and the right middle area is excavated; the left side area and the right side area are excavated, ordinary prestressed anchor cables and radial system anchor rods of the vault are installed, and initial support and secondary lining are performed. The present invention transfers the vault load of the large-span underground cavern to the internal stable surrounding rock, and realizes the self-stabilization of the surrounding rock as a whole.

Description

Technical Field

[0001] The invention belongs to the technical field of building structures, and in particular relates to a method for constructing a large-span column-free underground cavern by utilizing a super-strong prestressed structure. Background Art

[0002] In recent years, geotechnical anchoring technology has achieved rapid development in many fields of civil construction. In projects such as slope reinforcement and underground cavern support, the advantages of this technology have been fully demonstrated, providing impetus for theoretical and technological innovation of prestressed anchoring technology. In more than a century of development, anchoring technology has achieved many new results in theoretical research, technological innovation, and engineering application, which has greatly promoted the emergence of new anchoring structures, new geotechnical anchoring equipment, and new anchor materials, thereby reacting to geotechnical anchoring technology, enabling it to play a better role in engineering practice.

[0003] In order to meet the growing demand for underground space use, how to use prestressed anchoring technology for large-span, column-free underground caverns, improve design concepts, and how to provide reasonable and effective support have become urgent issues that need to be addressed. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for constructing a large-span column-free underground cavern by utilizing a super-strong prestressed structure. Through the bearing effect of the continuous longitudinal beam anchored by super-strong prestressed anchor cables, the vault load of the large-span underground cavern is transferred to the internal stable surrounding rock, thereby realizing the self-stabilization of the surrounding rock as a whole.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for constructing a large-span column-free underground cavern by using a super-strong prestressed structure, the method comprising the following steps:

[0007] Step S1, according to the on-site topography, geological conditions and functional zoning, the large-section excavation is divided into small-section excavation, and the overall area is divided into a spandrel excavation area, a middle spandrel area, and a side excavation area, the spandrel excavation area includes a left spandrel area, a middle spandrel area, and a right spandrel area, the middle excavation area includes a left middle area and a right middle area, and the side excavation area includes a left side area and a right side area;

[0008] Step S2, first excavate the left spandrel area, reserve the middle rock column, grouting reinforce the upper area of ​​the middle rock column, after the cavern deformation is stable, excavate the middle rock column, set up the longitudinal bearing beam, and install the super-strong prestressed anchor cable; sequentially excavate the middle spandrel area and the right spandrel area, and follow the excavation and support steps of the left spandrel area;

[0009] Step S3, then excavate the left middle area of ​​the cavern, install common prestressed anchor cables at the tunnel vault, then install radial system anchor rods at the vault, and perform anchor spraying support. After completing the excavation of the left middle area, excavate the right middle area, and follow the excavation and support steps of the left middle area;

[0010] Step S4, excavate the left side area, install ordinary prestressed anchor cables at the tunnel arch and then install radial system anchor rods at the arch, and perform anchor spraying support. After completing the excavation of the left side area, excavate the right side area and follow the excavation and support steps of the left side area; finally, complete all the initial support and secondary lining operations.

[0011] As a preferred embodiment, it is suitable for large-span column-free underground caverns with a span ratio of less than 1, a span of 30m~80m, and a lateral pressure coefficient of 1~3 in II~IV grade hard rock formations.

[0012] Preferably, the number of the super-strong prestressed anchor cables is determined according to the span of the cavern, including but not limited to 1 to 3 groups.

[0013] Preferably, according to the cave span and geological conditions, the length of the radial system anchor is 3m~10m, and the circumferential and longitudinal spacing is 1m~3m; the length of the super-strong prestressed anchor cable is 15m~35m, the circumferential and longitudinal spacing is 4m~8m, the prestressing is 1000kN~2500kN, and the longitudinal mid-rock column segmentation spacing is 4~10m.

[0014] Preferably, in step S2, in the initial stage of excavation of the middle rock columns in the left spandrel area, the middle spandrel area, and the right spandrel area, the bearing function of the middle rock columns is utilized to bear the loosening pressure of the upper area of ​​the middle rock columns and the surrounding rock, and the longitudinal bearing beams are erected every 6m in the longitudinal direction to complete the conversion of the spandrel load from being borne by the middle rock columns in the early stage to utilizing the longitudinal bearing beams and super-strong prestressed anchor cables; in the longitudinal direction, the middle rock columns are not completely demolished at one time, but a section of the middle rock columns is left every 6m, and a section of the longitudinal bearing beam is erected. After the super-strong prestressed anchor cables and the longitudinal bearing beams reach the bearing function, the remaining middle rock columns are demolished, and through successive replacement, a large-span column-free underground large space structure is constructed, and the force conversion of the large-span column-free structure is completed at the same time.

[0015] Preferably, in step S3, when excavating the left middle area and the right middle area, the longitudinal spacing between each heading face is not less than 10m; radial system anchors are installed to form a closed local bearing arch, and the loosening pressure of the surrounding rock is borne by the local bearing arch, and the loosening pressure of the surrounding rock at the arch shoulder is transmitted to the deep layer of the surrounding rock through the super-strong prestressed anchor cable, and the load of each local bearing arch part is shared by the ordinary prestressed anchor cable.

[0016] Preferably, in step S4, the left side area and the right side area are excavated, and radial system anchors are installed to form a local bearing arch in the excavation area. After the excavation of the cavern is completed, initial support and secondary lining are promptly applied to form a closed initial support.

[0017] The present invention has the following beneficial effects:

[0018] The present invention provides a method for constructing a large-span column-free underground cavern using a super-strong prestressed structure. Through the bearing effect of the continuous longitudinal beam anchored by the super-strong prestressed anchor cable, the vault load of the large-span underground cavern is transferred to the internal stable surrounding rock, thereby achieving self-stabilization of the surrounding rock as a whole. The large-span column-free underground cavern strengthens the bearing capacity of the load-bearing arch through the anchoring effect of the prestress, and at the same time transfers the loosening pressure of the vault surrounding rock to the inside of the surrounding rock through the longitudinal beam and anchor cable system. The present invention realizes the safe and efficient construction of large-span column-free underground caverns through innovative design ideas and improved construction methods, and the cavern span can reach 30m~80m.

[0019] 1. The present invention realizes the large-space formation of large-span column-free underground caverns, and can be tailored to the cross-sectional clearance for specific industrial facilities and civil facilities, with good social benefits and excellent scalability.

[0020] 2. The present invention provides a safe and efficient construction method for underground caverns, greatly reduces construction risks, effectively controls surrounding rock deformation, and has high safety.

[0021] 3. The present invention makes full use of the self-bearing capacity of the surrounding rock and the load transfer function of the prestressed anchor cable. The surrounding rock bears most of the load as a natural bearing arch, and the prestressed anchor cable bears the loosening pressure of the surrounding rock at the arch top, which greatly reduces the support materials, reduces the project cost, and has good economy.

[0022] 4. The construction method of the present invention has clear procedures, the construction of each part does not interfere with each other, the large-span underground cavern vault has a better support structure, and has good feasibility.

[0023] 5. The present invention proposes an advanced concept of realizing a column-free structure in the surrounding rock through regional excavation, which greatly improves the design and construction level of large-span column-free caverns in this field and makes the original design theory take a solid step forward. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the embodiments of the present invention.

[0025] Figure 1 This is a schematic diagram of a large-span column-free underground cavern structure using a super-strong prestressed structure according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the spandrel area of ​​an underground cavern excavated according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of ultra-strong prestressed anchor cables for driving a rock column during excavation according to an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the structure of the middle area of ​​an underground cavern excavated according to an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the structure of the areas on both sides of the underground cavern excavated according to an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the longitudinal bearing beam structure for excavating a rock column in an embodiment of the present invention;

[0031] Figure 7 This is a plan excavation diagram of a large-span column-free underground cavern according to an embodiment of the present invention.

[0032] Description of reference numerals:

[0033] 1. Super strong prestressed anchor cable; 2. Longitudinal load-bearing beam; 3. Radial system anchor rod; 4. Local load-bearing arch; 5. Ordinary prestressed anchor cable; 6. Initial support; 7. Secondary lining; 8. Left spandrel area; 9. Middle spandrel area; 10. Right spandrel area; 11. Left middle area; 12. Right middle area; 13. Left side area; 14. Right side area; 15. Upper area of ​​middle rock column. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] This embodiment provides a method for constructing a large-span column-free underground cavern using a super-strong prestressed structure. Figures 1 to 7 As shown, the method comprises the following steps:

[0036] Step S1, according to the on-site topography, geological conditions and functional zoning, the large-section excavation is divided into small-section excavation, and the overall area is divided into a spandrel excavation area, a middle excavation area and a side excavation area. The spandrel excavation area includes a left spandrel area 8, a middle spandrel area 9 and a right spandrel area 10, the middle excavation area includes a left middle area 11 and a right middle area 12, and the side excavation area includes a left side side area 13 and a right side side area 14.

[0037] Step S2, first excavate the left spandrel area 8, reserve the middle rock column, and grouting reinforce the upper area 15 of the middle rock column (i.e., the spandrel). After the deformation of the cavern is stable, excavate the middle rock column, erect the longitudinal bearing beam 2, and install the super-strong prestressed anchor cable 1; sequentially excavate the middle spandrel area 9 and the right spandrel area 10, following the excavation and support steps of the left spandrel area 8.

[0038] Step S3, then excavate the left middle area 11 of the cavern, install ordinary prestressed anchor cables 5 at the tunnel vault, then install radial system anchor rods 3 at the vault, and perform anchor spraying support. After completing the excavation of the left middle area 11, excavate the right middle area 12, and follow the excavation and support steps of the left middle area 11.

[0039] Step S4, excavate the left side area 13, install ordinary prestressed anchor cables 5 at the tunnel vault, then install radial system anchor rods 3 at the vault, and perform anchor spraying support. After completing the excavation of the left side area 13, excavate the right side area 14, and follow the excavation and support steps of the left side area 13; finally, complete all the construction of the initial support 6 and the secondary lining 7.

[0040] Furthermore, it is suitable for large-span column-free underground caverns with a span-to-span ratio of less than 1, a span of 30m~80m, and a lateral pressure coefficient of 1~3 in grade II~IV hard rock formations.

[0041] Furthermore, the width of the left shoulder area 8, the middle shoulder area 9, and the right shoulder area 10 is about 8m, the width of the left middle area 11 and the right middle area 12 is about 15m, the excavation width of the left side area 13 at the leftmost end of the cavern and the right side area 14 at the rightmost end of the cavern is about 15m, and the total width of the section is 84m.

[0042] Furthermore, the number of the super-strong prestressed anchor cables is determined according to the span of the cavern, including but not limited to 1 to 3 groups.

[0043] Furthermore, according to the cavern span and geological conditions, the length of the radial system anchor rod 3 is 3m~10m, and the circumferential and longitudinal spacing is 1m~3m; the length of the super-strong prestressed anchor cable 1 is 15m~35m, the circumferential and longitudinal spacing is 4m~8m, the prestressing is 1000kN~2500kN, and the longitudinal mid-rock column segmentation spacing is 4~10m.

[0044] Further, in step S2, after the excavation of each of the left shoulder area 8, the middle shoulder area 9, and the right shoulder area 10 is completed, grouting reinforcement is first performed on the upper area 15 of the middle rock column inside the excavation area. After the rock pressure is reasonably released during the excavation process, the lower part of the middle rock column in the longitudinal direction of the tunnel is excavated. The excavation length in the longitudinal direction is 6m, and a 400mm×300mm longitudinal bearing beam 2 is erected in the excavation section.

[0045] Further, in step S2, in the initial stage of excavation of the middle rock columns of the left spandrel area 8, the middle spandrel area 9, and the right spandrel area 10, the bearing effect of the middle rock columns is utilized to bear the loosening pressure of the upper area 15 of the middle rock columns and the surrounding rock, and the longitudinal bearing beams 2 are erected every 6m in the longitudinal direction to complete the conversion of the spandrel load from being borne by the middle rock columns in the early stage to utilizing the longitudinal bearing beams 2 and the super-strong prestressed anchor cable 1; in the longitudinal direction, the middle rock columns are not completely demolished at one time, but a section of the middle rock columns is left every 6m, and a section of the longitudinal bearing beam 2 is erected. After the super-strong prestressed anchor cable 1 and the longitudinal bearing beam 2 reach the bearing effect, the remaining middle rock columns are demolished, and through successive replacement, a large-span column-free underground large space structure is constructed, and the force conversion of the large-span column-free structure is completed at the same time.

[0046] Furthermore, in step S2, during the excavation of the area where the arch shoulder is located, monitoring and measurement are strengthened, and excavation can be continued only after the deformation of the surrounding rock is stabilized; in the initial stage of excavation, the pressure of the upper rock mass is borne by the middle rock column. After the super-strong prestressed anchor cable 1 is installed, the loosening pressure of the surrounding rock is mainly transmitted to the interior of the rock mass by the super-strong prestressed anchor cable 1 and the longitudinal bearing beam 2.

[0047] Furthermore, in step S3, when the left middle area 11 and the right middle area 12 are excavated, the longitudinal spacing between the tunnel faces is not less than 10m; radial system anchor rods 3 are installed to form a closed local bearing arch 4, and the loosening pressure of the surrounding rock is borne by the local bearing arch 4, and the loosening pressure of the surrounding rock at the arch shoulder is transmitted to the deep layer of the surrounding rock through the super-strong prestressed anchor cable 1, and the load of each local bearing arch part is shared through the ordinary prestressed anchor cable 5. When the left middle area 11 and the right middle area 12 are excavated, the surrounding rock in the middle area serves as the main bearing structure and isolation barrier to ensure normal excavation on the left and right sides of the small section in the middle area.

[0048] Furthermore, in step S4, the left side area 13 and the right side area 14 are excavated, and radial system anchors 3 are installed to form a local bearing arch 4 in the excavation area. After the excavation of the cavern is completed, initial support 6 and secondary lining 7 are promptly applied to form a closed initial support 6.

[0049] This embodiment divides the large-section excavation into multiple small-section excavations, and carries out the initial load through the local bearing arch, and carries the load at the spandrel through the super-strong prestressed anchor cable 1, and transfers the loose pressure outside the tunnel to the deep layer of the surrounding rock, and finally reaches the state of joint load-bearing of the bearing arch and the super-strong prestressed anchor cable. The stress state at the spandrel undergoes one force conversion and two loads, a total of three force state conversions. The first force conversion is to excavate the middle rock column, set up the longitudinal bearing beam 2, and install the super-strong prestressed anchor cable 1. The spandrel is carried by the middle rock column and gradually converted to the longitudinal bearing beam 2; the second time is when the middle area 11 on the left and the middle area 12 on the right of the middle area are excavated, and the load of this area is gradually transferred to a part of the spandrel; the third time is after the initial support 6 and the secondary lining 7 are completed, the load is added to the spandrel, and the three stress state changes at the spandrel are completed. Finally, the surrounding rock loosening pressure is transferred to the super-strong prestressed anchor cable 1, and the super-strong prestressed anchor cable 1 transfers the surrounding rock shallow layer loosening pressure to the surrounding rock deep layer.

[0050] It can be seen from the above technical solutions that the method for constructing a large-span column-free underground cavern using a super-strong prestressed structure provided in this embodiment transfers the vault load of the large-span underground cavern to the internal stable surrounding rock through the bearing effect of the continuous longitudinal beam anchored by the super-strong prestressed anchor cable, thereby realizing the self-stabilization of the surrounding rock as a whole. The large-span column-free underground cavern strengthens the bearing capacity of the load-bearing arch through the anchoring effect of the prestress, and at the same time transfers the loosening pressure of the vault surrounding rock to the interior of the surrounding rock through the longitudinal beam and the anchor cable system. The present invention realizes the safe and efficient construction of large-span column-free underground caverns through innovative design ideas and improved construction methods, and the cavern span can reach 30m~80m.

[0051] This embodiment realizes the large-space cavern formation of large-span column-free underground caverns, and can tailor-make the cross-sectional clearance for specific industrial facilities and civil facilities, with good social benefits and excellent scalability. It provides a safe and efficient construction method for underground caverns, greatly reduces construction risks, effectively controls the deformation of surrounding rocks, and has high safety. It makes full use of the self-bearing capacity of surrounding rocks and the load transfer function of prestressed anchor cables. The surrounding rock bears most of the load as a natural bearing arch, and the prestressed anchor cables bear the loosening pressure of the surrounding rock on the arch top, which greatly reduces the support materials, reduces the project cost, and has good economy. The construction method of this embodiment has clear procedures, and the construction of each part does not interfere with each other. The arch top of the large-span underground cavern has a good support structure and has good feasibility. It proposes the advanced concept of realizing the surrounding rock column-free structure through regional excavation, which greatly improves the design and construction level of large-span column-free caverns in this field, and makes the original design theory take a solid step forward.

[0052] The above embodiments of the present invention are described in detail through examples, but the contents described are only exemplary embodiments of the embodiments of the present invention and cannot be considered to limit the scope of implementation of the embodiments of the present invention. The protection scope of the embodiments of the present invention is defined by the claims. Anyone who utilizes the technical solutions described in the embodiments of the present invention, or who, inspired by the technical solutions of the embodiments of the present invention, designs similar technical solutions within the essence and protection scope of the embodiments of the present invention to achieve the above technical effects, or who makes equal changes and improvements to the scope of application, shall still fall within the scope of protection covered by the patent of the embodiments of the present invention.

Claims

1. A method for constructing a large-span column-free underground cavern using a super-strong prestressed structure, characterized in that: The method comprises the following steps: Step S1, according to the on-site topography, geological conditions and functional zoning, the large-section excavation is divided into small-section excavation, and the overall area is divided into a spandrel excavation area, a middle spandrel excavation area and a side excavation area, the spandrel excavation area includes a left spandrel area (8), a middle spandrel area (9) and a right spandrel area (10), the middle excavation area includes a left middle area (11) and a right middle area (12), and the side excavation area includes a left side area (13) and a right side area (14); Step S2, first excavate the left spandrel area (8), reserve the middle rock column, and reinforce the upper area of ​​the middle rock column (15) by grouting. After the deformation of the cavern is stable, excavate the middle rock column, erect the longitudinal bearing beam (2), and install the super-strong prestressed anchor cable (1); sequentially excavate the middle spandrel area (9) and the right spandrel area (10), and follow the excavation and support steps of the left spandrel area (8); Step S3, then excavate the left middle area (11) of the cavern, install common prestressed anchor cables (5) at the tunnel vault, then install radial system anchor rods (3) at the vault, and perform anchor spraying support. After the excavation of the left middle area (11) is completed, excavate the right middle area (12), and follow the excavation and support steps of the left middle area (11); Step S4, excavating the left side area (13), installing common prestressed anchor cables (5) at the tunnel vault, then installing radial system anchor rods (3) at the vault, and performing anchor spraying support. After the excavation of the left side area (13) is completed, the right side area (14) is excavated, and the excavation and support steps of the left side area (13) are followed; finally, the initial support (6) and the secondary lining (7) are all completed; In step S2, at the initial stage of excavation of the middle rock columns of the left spandrel area (8), the middle spandrel area (9), and the right spandrel area (10), the bearing function of the middle rock columns is utilized to bear the loosening pressure of the upper area (15) of the middle rock columns and the surrounding rock. By erecting longitudinal bearing beams (2) every 6 m in the longitudinal direction, the spandrel load is transformed from being borne by the middle rock columns in the early stage to being borne by the longitudinal bearing beams (2) and the super-strong prestressed anchor cables (1). In the longitudinal direction, the middle rock columns are not completely removed at once, but a section of the middle rock columns is left every 6 m, and a section of the longitudinal bearing beams (2) is erected. After the super-strong prestressed anchor cables (1) and the longitudinal bearing beams (2) have achieved their bearing function, the remaining middle rock columns are removed. By replacing them one by one, a large-span column-free underground large space structure is constructed, and the force conversion of the large-span column-free structure is completed at the same time.

2. The method for constructing a large-span column-free underground cavern using a super-strong prestressed structure according to claim 1 is characterized in that: It is suitable for large-span column-free underground caverns with a span-to-span ratio of less than 1, a span of 30m~80m, and a lateral pressure coefficient of 1~3 in II~IV grade hard rock formations.

3. The method for constructing a large-span column-free underground cavern using a super-strong prestressed structure according to claim 1 is characterized in that: The number of the super-strong prestressed anchor cables (1) is determined according to the span of the cavern, including but not limited to 1 to 3 groups.

4. The method for constructing a large-span column-free underground cavern using a super-strong prestressed structure according to claim 1 is characterized in that: According to the cave span and stratum conditions, the length of the radial system anchor rod (3) is 3m~10m, and the circumferential and longitudinal spacing is 1m~3m; the length of the super-strong prestressed anchor cable (1) is 15m~35m, and the circumferential and longitudinal spacing is 4m~8m, the prestressing force is 1000kN~2500kN, and the longitudinal mid-rock column segmentation spacing is 4~10m.

5. The method for constructing a large-span column-free underground cavern using a super-strong prestressed structure according to claim 1 is characterized in that: In step S3, when excavating the left middle area (11) and the right middle area (12), the longitudinal spacing between the tunnel faces is not less than 10 m; radial system anchor rods (3) are installed to form a closed local bearing arch (4), and the loosening pressure of the surrounding rock is borne by the local bearing arch (4). The loosening pressure of the surrounding rock at the arch shoulder is transmitted to the deep layer of the surrounding rock through the super-strong prestressed anchor cable (1), and the load of each local bearing arch part is shared by the ordinary prestressed anchor cable (5).

6. The method for constructing a large-span column-free underground cavern using a super-strong prestressed structure according to claim 1 is characterized in that: In step S4, the left side area (13) and the right side area (14) are excavated, and radial system anchors (3) are installed to form a local bearing arch (4) in the excavation area. After the excavation of the cavern is completed, initial support (6) and secondary lining (7) are promptly applied to form a closed initial support (6).

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