A tunnel construction method for expanding a small cross section to a large cross section

Abstract

The application discloses a construction method for tunnel small-section sudden expansion to large-section, and provides two independent construction schemes: a far-hole blasting method and a vertical slot excavation method. The far-hole blasting method is to drill holes, charge and adopt a delay light blasting technology in a small-section with support, so that the light blasting holes at the boundary of the large and small sections are detonated in a lagging manner, the surrounding rock is disturbed little, and the overbreak and underbreak are controllable. The vertical slot excavation method is to only excavate and support in a vertical slot with a width of one excavation cycle footage, continue to advance one cycle footage according to the original small section to provide a working space for the vertical slot excavation, timely hang a net and spray mortar after slag removal, and drill and blast equipment and personnel are operated under the supported area. Both the two methods adopt non-continuous charging and smooth blasting technology, the main blasting hole is detonated first, and the light blasting hole is detonated last. The application avoids the installation and removal process of the temporary steel arch, eliminates the excavation risk of the triangular area, significantly improves the construction safety, and reduces the disturbance of the surrounding rock.

Description

Technical Field

[0001] This invention relates to the field of tunnel cross-section construction, and more specifically to a method for expanding a tunnel from a small cross-section to a large cross-section. Background Technology

[0002] To open up a passage to Tibet and South Asia and achieve interconnectivity between Sichuan, Yunnan, and Guizhou, the Hengduan Mountains will inevitably become a core intersection area. Due to the limitations of high mountain and canyon terrain, geological hazards, and ecological protection, interchanges and hubs need to be built underground. With the mining, hydropower and water conservancy development in the Hengduan Mountains region, and the implementation of strategies such as pumped storage, compressed air storage, supercomputing, underground storage, inter-basin water transfer, high-speed railways, and highways, a huge number of underground power plants, tunnels, underground interchanges and hubs will need to be built. This will inevitably lead to a sudden expansion of cross-sections several times, or even dozens of times, to serve as large ventilation, traffic diversion, branching, shunting, maintenance, power generation, power distribution, or the installation of water turbines, underground parking lots, or TBM launching and receiving shafts, etc.

[0003] 1. At present, tunnel construction technology has suddenly become the mainstream construction method. When a large section of a tunnel is suddenly excavated into a smaller section, it is easy to enter the smaller section for construction as long as the excavation gantry and the reinforcing steel arch are properly constructed. Moreover, the excavation gantry and the reinforcing steel arch are easy to manufacture and install.

[0004] The current mainstream construction technique for tunnels, which involves suddenly excavating from a small section to a large section, is the gradual widening method, which carries extremely high safety risks. When the small section reaches the interface between the small and large sections, it is then gradually widened to the large section. (See...) Figure 1 However, a triangular area was left behind, requiring the installation of temporary steel arches to prevent the roof from collapsing or even forming a landslide. Then, the steel arches in the triangular area were removed while the remaining triangular area was excavated. Therefore, the process was not only complex and cumbersome, but also involved workers remaining under exposed rock, compromising their safety and increasing costs.

[0005] Then turn around and dismantle the temporary steel arches one by one, excavating the corresponding triangular areas, see... Figure 2 .

[0006] The incremental expansion method requires the temporary steel arch frame to be dismantled before the triangular area can be excavated, leaving the work space exposed without support, making it difficult to guarantee safety. Summary of the Invention

[0007] Therefore, in order to overcome the above-mentioned shortcomings, the present invention provides a method for constructing a tunnel by suddenly expanding a small cross-section to a large cross-section.

[0008] This invention is implemented by constructing a method for expanding a tunnel from a small cross-section to a large cross-section, characterized in that: The construction methods for expanding a small cross-section to a large cross-section include remote hole blasting and vertical trench excavation. When conducting remote hole blasting: explosives are delivered to the expansion space remotely through drilling so that they can be excavated together with the small cross-section rock mass; in remote hole blasting, the expansion section, drilling, and loading are all carried out within a small cross-section with a support system, ensuring operational safety; Two completely different drilling methods can be used for remote hole blasting: parallel drilling and concentric drilling. In order to reduce disturbance to the surrounding rock and avoid or eliminate over- and under-excavation, the explosive charge structure adopts delayed blasting technology; the boundary between the large and small sections of the tunnel is implemented with smooth blasting technology, and the small section is detonated radially segment by segment. When the vertical trench is excavated, the excavation and support are limited to the vertical trench with one excavation cycle width. First, continue to advance one cycle according to the original small cross section to provide drilling equipment operating space for the sudden expansion space. To prevent roof falls or collapses, after clearing debris, it is necessary to check the roof and walls, remove any hazards, and apply netting and shotcrete as needed. Drilling and blasting equipment can be placed under the support for operation, and the main body of the drilling and blasting equipment and the operators can also be located within the supported small section as much as possible. To minimize disturbance to the surrounding rock and avoid or eliminate over- and under-excavation, delayed blasting technology can be adopted for the charge structure and segmented blasting; delayed blasting of explosives at the boundary between large and small sections. The explosives are detonated away from the center of the sudden expansion space, propagating towards both ends of the large and small sections, with delayed detonation of the corresponding smooth blasting holes at the boundary between the large and small sections, thereby minimizing disturbance to the surrounding rock and avoiding or eliminating over- and under-excavation. All holes are not continuously charged; the number of explosive charges in the smooth blasting holes is greater and shorter than in the main blasting holes. The main blasting holes on the side with the larger cross-section are detonated several sections in advance. After the main blasting holes are detonated, the last remaining smooth blasting holes are detonated.

[0009] The present invention has the following advantages: 1. Significantly improves operational safety: In the remote-hole blasting method, all processes such as drilling and charging are carried out within a small cross-section of the existing support system. Workers do not need to enter the large, unsupported cross-section space, which fundamentally avoids safety accidents such as roof falls and collapses.

[0010] In the vertical trench excavation method, drilling and blasting equipment can be placed below the supported area, and personnel should also stay within the supported small section as much as possible to further ensure the safety of construction personnel.

[0011] 2. Avoid or reduce over-excavation and under-excavation to minimize disturbance to the surrounding rock. The delayed blasting technique, with delayed detonation of the blast holes at the large and small cross-section boundaries, allows for controllable blasting energy and effectively reduces disturbance to the surrounding rock. All blast holes use discontinuous charges, and the blast holes have more but shorter charge cartridges, enabling precise blasting control and significantly improving over- and under-excavation issues.

[0012] 3. Simplify construction procedures and improve construction efficiency. The remote-hole blasting method eliminates the need for temporary support and dismantling within the suddenly expanded space, avoiding the complex process of installing temporary steel arches, dismantling them, and then turning around to excavate the triangular area, as in the traditional "gradual widening method." The vertical trench excavation method operates only within a vertical trench the width of one excavation cycle, without forming a triangular area, reducing overlapping and repetitive operations, and saving construction time.

[0013] 4. Reduce project costs This eliminates the need for installing and dismantling temporary steel arches, reducing material consumption and labor input. It also avoids the costs of subsequent lining repair or removal due to over- or under-excavation, thus lowering overall construction costs.

[0014] 5. Highly adaptable, allowing for flexible selection of process solutions. It offers two independent solutions: remote hole blasting (including parallel drilling and concentric drilling) and vertical trench excavation. The solution can be flexibly selected according to the actual surrounding rock conditions, equipment capacity, and construction period requirements, thus enhancing the technical adaptability.

[0015] 6. Improve the working environment and reduce the exposure time of exposed rock masses. Immediately after blasting and debris removal, the rock face should be sealed by tapping the sides and top, hanging netting and spraying grout, reducing the risk of weathering and instability of the surrounding rock, which is conducive to long-term structural stability. Attached Figure Description

[0016] Figure 1 Schematic diagram of the mainstream construction technique, enlarged excavation method; Figure 2 Schematic diagram of the mainstream construction technique, the triangular area U-turn excavation method; Figure 3 Schematic diagram of blasting for wide-hole enlargement in small cross-sections; Figure 4 Schematic diagram of blasting for wide-hole enlargement in small cross-sections; Figure 5 Schematic diagram of vertical trench excavation method continuing to advance in small cross sections; Figure 6 Schematic diagram of vertical slot drilling and blasting operation in a suddenly expanded space; Figure 7 Schematic diagram of the segmented setup of the vertical slot in the sudden expansion space. Detailed Implementation

[0017] The following will be combined with the appendix Figures 1-7 This invention will be described in detail, and the technical solutions in the embodiments of this invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0018] This invention provides an improved method for constructing a tunnel by suddenly expanding from a small cross-section to a large cross-section, which is described below in conjunction with the appendix. Figures 3-7 Provide a detailed explanation; To avoid forming triangular areas, the number of temporary support removal procedures in triangular areas is reduced to minimize or eliminate safety accidents. There are two construction methods for expanding a small cross-section to a large cross-section: remote hole blasting and vertical trench excavation.

[0019] The basic principle of remote-hole blasting, compared to conventional drilling blasting, involves delivering explosives remotely through a borehole to the expansion space, allowing for excavation along with the small-section rock mass. In remote-hole blasting, the expansion portion, drilling, and explosive loading are all carried out within a supported small-section, ensuring operational safety. See [link to relevant documentation]. Figure 3 .

[0020] For long-hole blasting, there are two completely different drilling methods: parallel drilling and concentric drilling. The former is easier to master, has a longer total hole length, and allows for multiple people to load explosives. Figure 3 The latter, conversely, see Figure 4 .

[0021] To minimize disturbance to the surrounding rock and avoid or eliminate over- and under-excavation, delayed blasting technology is employed in the explosive charge structure. Smooth blasting is used at the boundary between the large and small sections of the tunnel, with delayed blasting performed radially segment by segment for each small section.

[0022] In the vertical trench excavation method, excavation and support are limited to the vertical trench within the width of one excavation cycle. The process begins by continuing one cycle along the original small cross-section.

[0023] To prevent roof falls or collapses, after clearing debris, it is necessary to check the roof and walls, remove any hazards, and apply netting and shotcrete as needed. Drilling and blasting equipment can be placed under the support for operation, and the main body of the drilling and blasting equipment and the operators can also be located within the supported small section as much as possible.

[0024] To minimize disturbance to the surrounding rock and avoid or eliminate over- and under-excavation, delayed blasting technology can be used in the charge structure and segmented blasting. The explosives at the boundary between the large and small sections are detonated with a delay. The explosives propagate from a distance away from the center of the expansion space towards both ends of the large and small sections, with the corresponding smooth blasting holes at the boundary between the large and small sections detonating with a delay. This achieves the goal of minimizing disturbance to the surrounding rock and avoiding or eliminating over- and under-excavation. See [link to relevant documentation]. Figure 7 .

[0025] All holes are not continuously charged; the number of explosive charges in the smooth blasting holes is greater and shorter than in the main blasting holes. The main blasting holes on the side with the larger cross-section are detonated several sections in advance. After the main blasting holes are detonated, the last remaining smooth blasting holes are detonated.

[0026] This invention discloses a construction method for rapidly expanding a tunnel from a small cross-section to a large cross-section, belonging to the field of tunnel cross-section construction. Addressing the problems of traditional gradual enlargement methods, such as the need for temporary steel arches, worker exposure to exposed rock, complex processes, cumbersome procedures, and high safety risks, this invention provides two independent construction schemes: remote-hole blasting and vertical trench excavation. The remote-hole blasting method involves remote drilling and charging within a supported small cross-section, employing delayed blasting technology to delay the detonation of the smooth blasting holes at the boundary between the large and small cross-sections, achieving safe expansion with minimal disturbance to the surrounding rock and controllable over- and under-excavation. The vertical trench excavation method involves excavation and support only within a vertical trench the width of one excavation cycle. First, one cycle of advance is continued along the original small cross-section to provide working space for the vertical trench excavation. After debris removal, mesh is promptly applied and shotcrete is applied. Drilling and blasting equipment and personnel operate within the supported area. Both methods employ discontinuous charging and smooth blasting technology, with the main blasting hole detonated first, followed by the smooth blasting hole. This invention avoids the installation and dismantling of temporary steel arch frames, eliminates the risk of excavation in triangular areas, significantly improves construction safety, reduces disturbance to surrounding rock, reduces over- and under-excavation, simplifies the process, and is suitable for engineering scenarios requiring sudden cross-sectional expansion, such as underground powerhouses, tunnel chambers, and hub interchanges. It has good economic efficiency and promotional value.

[0027] This invention addresses the long-standing pain points in tunnel construction, such as high safety risks, complex processes, cumbersome procedures, and high costs associated with the sudden expansion from a small cross-section to a large cross-section. It provides a systematic solution with significant engineering application value.

[0028] I. Solving the Problem of Sudden Cross-Section Enlargement under Complex Geological Conditions. Located in the Hengduan Mountains and other mountainous areas of Southwest China, the terrain is rugged with high mountains and deep valleys, and geological disasters are frequent, leading to a surge in demand for sudden cross-section enlargement in underground engineering projects. The remote-hole blasting method and vertical trench excavation method provided by this invention can be used safely with a support system, effectively addressing harsh conditions such as unstable surrounding rock and limited working space. It is particularly suitable for engineering scenarios requiring cross-section enlargement several times, or even dozens of times, compared to underground powerhouses, pumped-storage power stations, compressed air storage chambers, TBM launching and receiving shafts, and underground interconnection hubs.

[0029] II. Significantly Reduces Construction Costs and Time. Traditional construction methods require the installation and dismantling of numerous temporary steel arch frames, resulting in repetitive procedures and high material consumption. This invention eliminates the need for temporary support structures, reducing dismantling work and lowering material and labor inputs. Simultaneously, by controlling over- and under-excavation through smooth blasting and delayed detonation techniques, it reduces the amount of subsequent lining repairs, thereby reducing overall project costs by approximately 15% to 25%.

[0030] III. Enhancing Construction Safety. All blasting and drilling operations are completed within the supported small cross-section, eliminating the need for workers to enter exposed and expanding spaces, thus preventing major safety accidents such as roof falls and collapses. This provides reliable technical support for high-risk tunnel construction, including deep-buried and high-stress tunnels.

[0031] IV. High adaptability and broad prospects for promotion. The two schemes can be flexibly selected based on equipment conditions and surrounding rock grade, requiring no complex equipment modifications and are easy to promote. This technology can provide a safe and efficient excavation method for numerous projects such as hub interchanges, underground storage, and hydropower development, possessing significant social benefits and industry demonstration value.

[0032] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A construction method for tunneling from a small cross-section to a large cross-section, characterized in that ； The construction methods for expanding a small cross-section to a large cross-section include remote hole blasting and vertical trench excavation. When conducting remote hole blasting: explosives are delivered to the expansion space remotely through drilling so that they can be excavated together with the small cross-section rock mass; in remote hole blasting, the expansion section, drilling, and loading are all carried out within a small cross-section with a support system, ensuring operational safety; Two completely different drilling methods can be used for remote hole blasting: parallel drilling and concentric drilling. In order to reduce disturbance to the surrounding rock and avoid or eliminate over- and under-excavation, the explosive charge structure adopts delayed blasting technology; the boundary between the large and small sections of the tunnel is implemented with smooth blasting technology, and the small section is detonated radially segment by segment. When the vertical trench is excavated, the excavation and support are limited to the vertical trench with one excavation cycle width. First, continue to advance one cycle according to the original small cross section to provide drilling equipment operating space for the sudden expansion space. To prevent roof falls or collapses, after clearing debris, it is necessary to check the roof and walls, remove any hazards, and apply netting and shotcrete as needed. Drilling and blasting equipment can be placed under the support for operation, and the main body of the drilling equipment and the operators can also be located within the supported small section as much as possible. In order to reduce disturbance to the surrounding rock and avoid or eliminate over- and under-excavation, delayed time-blasting technology can be adopted for charge structure and segmented blasting; Delayed detonation of explosives at the boundary between large and small cross sections; Detonation is carried out at both ends of the large and small cross sections, away from the center of the sudden expansion space. The blasting holes at the boundary between the large and small cross sections are detonated with a delay, so as to reduce the disturbance to the surrounding rock and avoid or eliminate over- and under-excavation. All holes are discontinuously charged, and the number of charge rolls in the blast holes is greater and shorter than that in the main gun holes; The main blast holes on the side with the large cross section are detonated several sections in advance. After the main blast holes are detonated, the last remaining light blast holes are detonated.

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