Underground cavern main cavern cross-hole excavation method in mountainous area
Patent Information
- Application Number
- CN202610465154.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-09
- Publication Date
- 2026-09-18
AI Technical Summary
[0005]本申请提供一种山区地下洞库主库穿心开挖方法，解决传统山区地下洞库开挖施工进度慢、安全风险高、成本高的技术问题，实现加快施工进度、降低工程成本、保障施工安全的效果，同时为后续同类山区地下洞库工程施工提供技术参考
1、施工进度大幅提升：本申请通过先开挖两条小断面引洞再贯通穿心导洞的方式，实现主库的早期贯通，穿心导洞为后续主库扩挖提供了多个作业面与洞内交通运输通道，山区地下洞库主库的上、下半断面分序扩挖可同步开展施工操作，相比传统挑顶扩挖的单一作业面，施工效率提升 50% 以上，有效缩短工程工期；
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Figure CN122774081A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a construction method for underground engineering in mountainous areas, and in particular to a method for excavating the main body of an underground cavern in mountainous areas. Background Technology
[0002] In the field of engineering construction, the demand for underground caverns in mountainous areas is increasing due to special construction needs such as national defense, energy, and warehousing. Mountainous underground cavern projects are affected by complex terrain, variable geological conditions, and limited construction sites, making excavation the core focus and challenge of the project. Problems such as tight construction schedules, high safety risks, and difficulty in controlling construction costs are particularly prominent.
[0003] The efficiency of underground cavern excavation in mountainous areas directly determines the overall project schedule, while construction safety is the fundamental guarantee for the smooth implementation of the project. Traditional underground cavern excavation in mountainous areas often adopts the construction scheme of starting from the approach tunnel and gradually expanding the excavation upwards to form the main cavern cross-section. This scheme has the problems of a single working face, slow construction progress, and difficulty in controlling the stability of the surrounding rock during the expansion process. It not only has low construction efficiency and increases the project construction cost, but also poses a high risk of construction safety, making it difficult to meet the construction needs of underground cavern projects in mountainous areas with tight schedules and high safety requirements.
[0004] Therefore, there is an urgent need to develop an underground cavern excavation method that is adapted to the geological and topographical conditions of mountainous areas, so as to achieve multiple goals such as accelerating construction progress, reducing construction costs and improving construction safety, and to provide a new technical solution for the construction of underground cavern projects in mountainous areas. Summary of the Invention
[0005] This application provides a method for core-excavation of the main body of an underground cavern in mountainous areas, solving the technical problems of slow construction progress, high safety risks, and high costs associated with traditional underground cavern excavation methods in mountainous areas. It achieves the effects of accelerating construction progress, reducing project costs, and ensuring construction safety, while also providing technical reference for subsequent similar underground cavern projects in mountainous areas. The specific technical solution is as follows: Firstly, a method for through-core excavation of the main chamber of an underground cavern in a mountainous area is provided, comprising the following steps: excavating two approach tunnels and setting initial support for the approach tunnels within them, the two approach tunnels being located on both sides of the pre-designed main chamber of the underground cavern in the mountainous area; excavating connecting tunnels between the two approach tunnels and the pre-designed main chamber of the underground cavern in the mountainous area, and reinforcing the surrounding rock of the connecting tunnels; starting from the connecting tunnels on both sides of the pre-designed main chamber of the underground cavern in the mountainous area, excavating a through-core guide tunnel that runs through the pre-designed main chamber of the underground cavern in the mountainous area and connects the connecting tunnels on both sides, and setting initial support for the inner wall of the through-core guide tunnel, wherein the arch of the through-core guide tunnel is at the same height as the designed arch of the main chamber of the underground cavern in the mountainous area; excavating the main chamber of the underground cavern in the mountainous area using the through-core guide tunnel as the working passage, and setting initial support for the main chamber within the main chamber of the underground cavern in the mountainous area; and constructing secondary reinforced concrete lining for the main chamber of the underground cavern in the mountainous area, the two approach tunnels, and the connecting tunnels.
[0006] In one embodiment, in the step of excavating two pilot tunnels, the excavation location and direction of the two pilot tunnels are determined, and the pilot tunnels are excavated using the drill-and-blast method or mechanical excavation method. The cross-sectional width of the pilot tunnel is 3~5m and the height is 3.5~6m.
[0007] In one embodiment, the initial support of the pilot tunnel adopts a combined support method of shotcrete, installation of anchor bolts and steel mesh.
[0008] In one embodiment, the connecting tunnel is located along the length extension of the main underground cavern in a pre-designated mountainous area and is orthogonally connected to the access tunnel.
[0009] In one embodiment, the excavation cross-section of the through-hole is rectangular, with a width of 4-6m, and is constructed using mechanical excavation or drill-and-blast methods.
[0010] In one embodiment, the steps for excavating the main section of an underground cavern in a mountainous area include: using a pilot tunnel as the working channel, expanding the upper half of the main section of the underground cavern in the mountainous area to both sides and above, and promptly carrying out initial support, with steel arch frames added to the support structure; after the expansion and support of the upper half of the main section of the underground cavern in the mountainous area is completed and the surrounding rock tends to be stable, advancing from both ends of the main section of the underground cavern in the mountainous area towards the middle to expand the lower half of the section, and promptly carrying out initial support.
[0011] In one embodiment, the excavation height of the upper half of the main section of the underground cavern in the mountainous area is 1 / 2 to 2 / 3 of the designed cross-sectional height of the main section. The excavation advance is controlled at 1 to 2 m per cycle. The steel arch frame is an I16 to I20 steel arch frame, and the spacing of the steel arch frame is 0.6 to 1.0 m.
[0012] In one embodiment, the criteria for determining the stability of the surrounding rock before the expansion of the lower half of the main section of the underground cavern in the mountainous area are: the circumferential displacement rate of the surrounding rock is less than 0.5 mm / d and the subsidence rate of the arch is less than 0.3 mm / d.
[0013] In one embodiment, support anchors are used to reinforce the surrounding rock of the main underground cavern in the mountainous area. The support anchors are hollow grouting anchors with a length of 3-5m, a spacing of 1.0-1.5m, and a quincunx arrangement. The grouting pressure is controlled at 0.8-1.2MPa.
[0014] In one embodiment, during the secondary lining construction of the underground cavern main lining in the mountainous area, a waterproof membrane and waterstop are pre-laid, and the entire structure is poured using a formwork trolley. The lining concrete is C30~C40 reinforced concrete, and the curing time is no less than 28 days.
[0015] Compared with the prior art, this application has the following beneficial effects: 1. Significantly improved construction progress: This application achieves early completion of the main storage facility by first excavating two small-section pilot tunnels and then connecting the through tunnel. The through tunnel provides multiple working faces and internal transportation channels for the subsequent expansion excavation of the main storage facility. The upper and lower half sections of the main storage facility in the mountainous underground cavern can be expanded in sequence and construction operations can be carried out simultaneously. Compared with the single working face of the traditional top-opening expansion excavation, the construction efficiency is increased by more than 50%, effectively shortening the project period. 2. Significantly enhanced construction safety assurance capabilities: This application follows the construction principle of "first breakthrough, then expansion; first support, then excavation". The small-section pilot tunnel and the through-hole tunnel are supported in a timely manner after excavation. The upper and lower half sections of the main underground cavern in the mountainous area are expanded in sequence and reinforced support structures are added to effectively control the deformation of the surrounding rock and avoid safety accidents such as the collapse of the surrounding rock. At the same time, the breakthrough of the through-hole tunnel realizes the two-way flow of ventilation and drainage in the tunnel, improves the construction working environment, and reduces construction safety risks. 3. Effective reduction in project costs: This application shortens the construction period by carrying out simultaneous construction on multiple work fronts, reducing on-site work time for construction equipment and personnel, and lowering costs such as labor and equipment rental. At the same time, the reasonable sequential excavation and support method reduces the amount of over-excavation of surrounding rock and reduces the consumption of support materials such as concrete and steel. Compared with traditional construction methods, the overall project cost is reduced by 20% to 30%. 4. Simple and applicable construction process: The construction steps of this application are clear, and the excavation and support technologies used are conventional and mature technologies for underground engineering. Construction personnel can easily operate them without the need for special equipment. It is applicable to underground cavern projects in mountainous areas with different geological conditions, and is especially suitable for underground cavern projects with tight construction schedules and high excavation safety risks. It has good engineering promotion value. Attached Figure Description
[0016] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the steps of a method for excavating the main chamber of an underground cavern in a mountainous area according to an embodiment of this application. Figure 2 This is a schematic diagram of two pilot tunnels after excavation according to an embodiment of this application; Figure 3 This is a schematic diagram of the connection hole after excavation according to an embodiment of this application; Figure 4 This is a schematic diagram of the excavation of a through-hole pilot tunnel according to an embodiment of this application; Figure 5 This is a schematic diagram of the upper half of the main section of an underground cavern in a mountainous area, according to an embodiment of this application, showing the excavation and support. Figure 6 This is a schematic diagram of the lower half of the cross-section of the main storage area of an underground cavern in a mountainous area, according to an embodiment of this application; Figure 7 This is a schematic diagram of the secondary lining of the main chamber of an underground cavern in a mountainous area, according to an embodiment of this application. Figure 8 This is a schematic diagram of the connecting hole and the secondary lining of the connecting hole according to an embodiment of this application. Detailed Implementation
[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0018] Please see Figure 1 and Figure 2 , Figure 1 This is a flowchart illustrating the steps of a method for excavating the main shaft of an underground cavern in a mountainous area, according to an embodiment of this application. Figure 2This is a schematic diagram of the excavation of two pilot tunnels according to an embodiment of this application. As shown in the figure, the main tunnel excavation method for underground caverns in mountainous areas according to this embodiment includes the following steps S1 to S5. In step S1, the excavation and support of two pilot tunnels 1 in the mountainous cavern are carried out: two pilot tunnels 1 are excavated, and initial support for the pilot tunnels 1 is set in the pilot tunnels 1. The two pilot tunnels 1 are located on both sides of the pre-designed main tunnel 2 of the underground cavern in the mountainous area. Specifically, according to the engineering design drawings and geological survey data, the excavation location and direction (excavation axis) of the two pilot tunnels 1 are determined. The small-section pilot tunnels 1 are excavated by drilling and blasting or mechanical excavation. The excavation process follows the principle of "short advance and fast support". The excavation section of tunnel 1 has a width of 3-5m and a height of 3.5-6m. The excavation advance is controlled at 1.5m / cycle. Immediately after excavation, initial support for tunnel 1 is carried out using a combination of shotcrete, anchor bolts, and steel mesh. For example, C25 concrete is shotcreted to a thickness of 10cm, Φ22 mortar anchor bolts are installed with a length of 3.5m and a spacing of 1.0m×1.0m, and Φ6 steel mesh is laid with a mesh spacing of 20cm×20cm to ensure the stability of the surrounding rock of tunnel 1.
[0019] Please refer to the following: Figure 3 This is a schematic diagram of the excavation of a connecting tunnel according to an embodiment of this application. As shown in the figure, in step S2, the connecting tunnel 3 is excavated and supported: the connecting tunnel 3 between the two approach tunnels 1 and the main underground cavern 2 in the mountainous area is excavated, and the surrounding rock of the connecting tunnel 3 is reinforced. The connecting tunnel 3 is located in the length extension direction of the main underground cavern 2 in the mountainous area and is orthogonally connected to the approach tunnels 1. Specifically, the connecting tunnel 3 is excavated between the intersection of the approach tunnels 1 and the main underground cavern 2 in the mountainous area, and Φ25 hollow grouting anchor rods are added to the connecting tunnel 3 for reinforcement support. The grouting pressure is controlled at 0.8~1.0MPa to prevent the surrounding rock of the connecting tunnel 3 from breaking and collapsing.
[0020] Please refer to the following: Figure 4This is a schematic diagram of the excavation of a through-tunnel according to an embodiment of this application, where the shaded area around the through-tunnel represents the area to be excavated in subsequent steps. As shown in the figure, in step S3, the through-tunnel 4 is excavated and supported as follows: starting from the connecting tunnels 3 on both sides of the pre-designed main underground cavern 2 in the mountainous area, the through-tunnel 4 is excavated in opposite directions, connecting the pre-designed main underground cavern 2 and the connecting tunnels 3 on both sides. The inner wall of the through-tunnel 4 is initially supported, wherein the arch of the through-tunnel 4 is at the same height as the designed arch of the main underground cavern 2 in the mountainous area. The excavation cross-section of the through-tunnel 4 is a rectangular cross-section with a width of 4~6m, and is constructed using mechanical excavation or drill-and-blast methods. Specifically, starting from the connecting tunnels 3 on both sides, the main storage tunnel 4 is excavated in opposite directions. The arch of the tunnel 4 is flush with the designed arch of the main storage. The excavation cross section is a rectangular section of 5m×6m. Mechanical excavation method is used to avoid the disturbance of the surrounding rock by drilling and blasting. After the excavation is completed, the initial support is carried out in time. The support method is the same as that of the pilot tunnel 1, and the main storage tunnel 4 is completed.
[0021] As described above, the through-core excavation method for the main underground cavern 2 in this embodiment achieves early connection of the main underground cavern 2 by first excavating two small-section guide tunnels 1 and then connecting the through-core guide tunnel 4. The through-core guide tunnel 4 provides multiple working faces and internal transportation channels for the subsequent expansion excavation of the main cavern.
[0022] In step S4, the main cavern 2 of the underground cavern in the mountainous area is expanded and supported: using the through-tunnel 4 as the working channel, the main cavern 2 is excavated, and initial support is installed within it. Support anchors 5 are used to reinforce the surrounding rock of the main cavern 2. These anchors are hollow grouting anchors, 3-5m long, spaced 1.0-1.5m apart in a staggered pattern, with grouting pressure controlled at 0.8-1.2MPa. The expansion and support of the main cavern 2 is divided into the upper half-section expansion and support, and the lower half-section expansion and support. This sequential expansion of the upper and lower sections of the main cavern 2 allows for simultaneous construction operations, increasing efficiency by over 50% compared to the traditional single-face excavation method, effectively shortening the project duration.
[0023] Please refer to the following: Figure 5This is a schematic diagram of the upper half-section excavation and support of the main section of an underground cavern in a mountainous area, according to an embodiment of this application. The shaded area in the diagram represents the area to be excavated in subsequent steps. As shown, during the upper half-section excavation of the main section 2 of the underground cavern in the mountainous area, the through-tunnel 4 serves as the working passage, and the upper half-section of the main section 2 is excavated to both sides and upwards. Initial support is provided in a timely manner, and steel arch frames are added to the support structure. The excavation height of the upper half-section of the main section 2 is 1 / 2 to 2 / 3 of the designed cross-section height of the main section. The excavation advance is controlled at 1 to 2 meters per cycle. The steel arch frames are I16 to I20 steel arch frames, and the spacing between the steel arch frames is 0.6 to 1.0 meters. Specifically, using the through-tunnel 4 as the working passage, the upper half of the main section of the underground cavern 2 in the mountainous area is expanded to both sides and above, with an expansion height of 10m. The project is carried out simultaneously in 5 sections, with each section expanding by 1.0m per cycle. After the expansion, I18 type steel arch frames are added at a spacing of 0.8m to form a coordinated support with anchor bolts and shotcrete. The thickness of the shotcrete is increased to 15cm.
[0024] As mentioned above, after the upper half of the main section of the underground cavern 2 in the mountainous area was excavated and supported, and the surrounding rock stabilized, the lower half of the section was excavated. Please refer to the following: Figure 6 This diagram illustrates the lower half-section excavation and support of the main section of an underground cavern 2 in a mountainous area, according to an embodiment of this application. As shown, the lower half-section excavation proceeds from both ends of the main section 2 towards the middle, with initial support implemented promptly. The stability criteria for the surrounding rock before the lower half-section excavation of the main section 2 are: a surrounding rock circumferential displacement rate of less than 0.5 mm / d and an arch crown settlement rate of less than 0.3 mm / d. Specifically, deformation monitoring of the upper half-section support structure of the main section 2 is conducted for 20 days. Monitoring data shows a surrounding rock circumferential displacement rate of 0.3 mm / d and an arch crown settlement rate of 0.2 mm / d. After reaching the stability criteria, the lower half-section excavation of the main section 2 is carried out, proceeding from both ends towards the middle. After the excavation is completed, C25 concrete is sprayed for support with a thickness of 12 cm, completing the full-section excavation and initial support of the main section.
[0025] In step S5, secondary lining construction involves constructing reinforced concrete secondary linings for the main underground cavern 2, the two approach tunnels 1, and the connecting tunnel 3, forming the secondary lining support 6. Please refer to the following: Figure 7This is a schematic diagram of the secondary lining of the main chamber of an underground cavern in a mountainous area, according to an embodiment of this application. As shown in the figure, after the deformation monitoring data of the surrounding rock of the main chamber 2 in the mountainous underground cavern reaches the stability standard, the secondary lining of the main chamber with reinforced concrete is carried out first. Before construction, a waterproof membrane and a waterstop are laid, and the entire structure is poured using a formwork trolley. The lining concrete is C30~C40 reinforced concrete, and the curing time is not less than 28 days. Please refer to the following: Figure 8 This is a schematic diagram of the secondary lining of the connecting tunnel and the connecting tunnel according to an embodiment of this application. As shown in the figure, secondary lining construction is then carried out on the two approach tunnels 1 and the connecting tunnel 3 to complete the excavation and lining construction of the entire underground cavern in the mountainous area. Specifically, the loose ballast on the initial support surface is cleaned, EVA waterproof membrane and embedded waterstop are laid, and C30 reinforced concrete secondary lining is poured as a whole using a 12m long formwork trolley. The lining thickness is 80cm, and the concrete is kept moist and cured for 28 days after pouring until the strength reaches the design requirements. After the secondary lining of the main cavern 2 of the underground cavern in the mountainous area is completed, secondary lining construction is carried out on the two approach tunnels 1 and the connecting tunnel 3. C25 reinforced concrete is poured, with a lining thickness of 30cm. The pouring is done in sections, each section being 10m long. After the construction is completed, the excavation and lining of the entire underground cavern is finished.
[0026] The core-excavation method for the main cavern 2 in this embodiment of the underground cavern project in mountainous areas shortens the construction period by simultaneously constructing multiple working faces (two approach tunnels 1 being excavated simultaneously, excavation from both sides towards each other starting from the connecting tunnels 3 on both sides, and excavation from both sides towards the center using the core guide tunnel 4 as the working channel). This reduces the on-site working time of construction equipment and personnel, and lowers costs such as labor and equipment rental. Simultaneously, the reasonable sequential excavation and support method reduces over-excavation of the surrounding rock and reduces the consumption of support materials such as concrete and steel. Compared with traditional construction methods, the overall project cost is reduced by 20% to 30%. Furthermore, the construction steps of this embodiment are clear, and the excavation and support technologies used are conventional and mature technologies for underground engineering. These are easy for construction personnel to operate, require no special equipment, and are suitable for underground cavern projects in mountainous areas with different geological conditions. They are particularly suitable for underground cavern projects with tight construction schedules and high excavation safety risks, and have good engineering promotion value.
[0027] In summary, this application provides a method for the core excavation of the main section of an underground cavern in mountainous areas. By first excavating two small-section guide tunnels and then connecting them through the core tunnel, the main section can be connected early. The core tunnel provides multiple working faces and internal transportation channels for the subsequent expansion excavation of the main section. The upper and lower sections of the main section of the underground cavern in mountainous areas can be expanded in sequence and construction operations can be carried out simultaneously. Compared with the single working face of traditional top-opening expansion excavation, the construction efficiency is increased by more than 50%, effectively shortening the construction period. This application follows the construction principle of "connection first, then expansion; support first, then excavation". The small-section guide tunnels and the core tunnel are supported in a timely manner after excavation. The upper and lower sections of the main section of the underground cavern in mountainous areas are expanded in sequence and reinforced support structures are added to effectively control the deformation of the surrounding rock and avoid safety accidents such as the collapse of the surrounding rock. At the same time, the connection of the core tunnel enables two-way circulation of ventilation and drainage in the cavern, improving the construction working environment and reducing construction safety risks. This application shortens the construction period by simultaneously constructing multiple work faces, reducing on-site work time for construction equipment and personnel, and lowering costs such as labor and equipment rental. Simultaneously, the rational sequential excavation and support method reduces over-excavation of surrounding rock and minimizes the loss of support materials such as concrete and steel. Compared to traditional construction methods, the overall project cost is reduced by 20% to 30%. The construction steps of this application are clear, and the excavation and support technologies used are conventional and mature underground engineering techniques. These are easy for construction personnel to operate, require no special equipment, and are suitable for underground cavern projects in mountainous areas with varying geological conditions. They are particularly suitable for underground cavern projects with tight construction schedules and high excavation safety risks, and have significant potential for widespread application.
[0028] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.
[0029] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.
Claims
1. A method for excavating the main body of an underground cavern in a mountainous area, characterized in that, Includes the following steps: Two access tunnels were excavated, and initial support for the access tunnels was installed inside the access tunnels. The two access tunnels were located on both sides of the main underground cavern of the pre-designated mountain area. Excavate connecting tunnels between the two aforementioned inlet tunnels and the main underground cavern of the pre-designated mountain area, and reinforce the surrounding rock of the connecting tunnels; Starting from the connecting tunnels on both sides of the main underground cavern in the mountainous area, a through-hole guide tunnel is excavated from opposite directions to penetrate the main underground cavern in the mountainous area and connect the connecting tunnels on both sides. The inner wall of the through-hole guide tunnel is initially supported. The arch of the through-hole guide tunnel is at the same height as the designed arch of the main underground cavern in the mountainous area. Using the through-tunnel as the working channel, the main underground cavern of the mountainous area is excavated, and the initial support of the main cavern is set up inside the main underground cavern of the mountainous area. The main underground cavern in the mountainous area, the two access tunnels, and the connecting tunnel were constructed with reinforced concrete secondary lining.
2. The method for excavating the main body of an underground cavern in a mountainous area according to claim 1, characterized in that, In the step of excavating the two pilot tunnels, the excavation location and direction of the two pilot tunnels are determined, and the pilot tunnels are excavated using the drill and blast method or mechanical excavation method. The cross-sectional width of the pilot tunnel is 3~5m and the height is 3.5~6m.
3. The method for excavating the main body of an underground cavern in a mountainous area according to claim 1, characterized in that, The initial support for the pilot tunnel adopts a combined support method of shotcrete, anchor bolts, and steel mesh.
4. The method for excavating the main body of an underground cavern in a mountainous area according to claim 1, characterized in that, The connecting tunnel is located along the length extension of the main underground cavern in the pre-designated mountainous area and is orthogonally connected to the access tunnel.
5. The method for excavating the main body of an underground cavern in a mountainous area according to claim 1, characterized in that, The excavation cross-section of the through-hole is rectangular, with a width of 4-6m, and is constructed using mechanical excavation or drill-and-blast methods.
6. The method for excavating the main body of an underground cavern in a mountainous area according to claim 1, characterized in that, The steps for excavating the main storage chamber of the underground cavern in the mountainous area include: Using the through-hole as the working channel, the upper half of the main section of the underground cavern in the mountainous area is expanded and excavated to both sides and above, and initial support is carried out in a timely manner, with steel arch frames added to the support structure. After the upper half of the main section of the underground cavern in the mountainous area is excavated and supported and the surrounding rock becomes stable, the lower half of the main section is excavated from both ends toward the middle, and initial support is carried out in a timely manner.
7. The method for excavating the main body of an underground cavern in a mountainous area according to claim 6, characterized in that, The excavation height of the upper half of the main section of the underground cavern in the mountainous area is 1 / 2 to 2 / 3 of the designed cross-sectional height of the main section. The excavation advance is controlled at 1 to 2 m per cycle. The steel arch frame is an I16 to I20 steel arch frame, and the spacing of the steel arch frame is 0.6 to 1.0 m.
8. The method for excavating the main body of an underground cavern in a mountainous area according to claim 6, characterized in that, The criteria for determining the stability of the surrounding rock before the expansion of the lower half of the main section of the underground cavern in the mountainous area are: the circumferential displacement rate of the surrounding rock is less than 0.5 mm / d, and the subsidence rate of the arch is less than 0.3 mm / d.
9. The method for excavating the main body of an underground cavern in a mountainous area according to claim 1, characterized in that, The surrounding rock of the main underground cavern in the mountainous area is reinforced by using support anchor bolts. The support anchor bolts are hollow grouting anchor bolts with a length of 3-5m, a spacing of 1.0-1.5m, and a quincunx arrangement. The grouting pressure is controlled at 0.8-1.2MPa.
10. The method for excavating the main body of an underground cavern in a mountainous area according to claim 1, characterized in that, During the secondary lining construction of the underground cavern in the mountainous area, waterproof membranes and waterstops were pre-laid, and the entire structure was poured using a formwork trolley. The lining concrete was C30~C40 reinforced concrete, and the curing time was no less than 28 days.