A construction method for a tunnel with extremely irregular local partial encroachment and severe dissolution

Abstract

The application discloses a construction method for extremely irregular local partial invasion and serious dissolution tunnels, and is characterized in that the construction operation is as follows: 1) surveying and measuring, evaluating the invasion range, severity and damage of the vertically hung objects; 2) excavating the invasion rock; 3) making the targeted and suitable steel skeleton and L-shaped formwork; 4) connecting the adjacent circulating rough steel bars; 5) supporting the formwork trolley; and 6) treating the invasion karst cave and the normal surrounding rock mass. From the safe tunnel with protected roof to the serious karst cave, the L-shaped formwork must be made for the lining pouring formwork, and the steel skeleton needs to be anchored on the contact surface of the karst cave.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction, specifically a method for constructing tunnels with highly irregular local encroachment and severe erosion. Background Technology

[0002] The western region, rich in energy and resources, has become the main battleground for the construction of highways, high-speed railways, and strategic hydropower station tunnels. Due to its geological evolution, including multiple marine transgressions and sedimentation, it has many karst caves, making tunnel construction exceptionally difficult.

[0003] Karst formations are characterized by complex and varied spatial distribution and extremely poor rock mass stability. Therefore, it is necessary to implement advanced support, initial support, secondary lining, and drainage systems to ensure safety, reliability, technical feasibility, economic rationality, and high quality.

[0004] Bridges or tunnels are constructed within the tunnel, using either a transverse support beam and raft foundation or an anchor mesh sprayed with steel structure to create an arched road, with a tunnel above it. Both methods are for non-intrusive giant karst caves. For the construction of extremely irregular, severely karstified tunnels, some methods involve completely filling the tunnel with concrete and then proceeding with normal tunnel construction. However, filling from the inside out results in poor construction quality, is extremely unsafe, and is very expensive. Summary of the Invention

[0005] Therefore, to address the aforementioned shortcomings, this invention provides a construction method for tunnels with highly irregular local erosion and severe karstification. When advancing from a protected, safe tunnel towards a severely eroded karst cave, the lining pouring formwork must be L-shaped, and the reinforcing steel frame must be anchored to the contact surface with the karst cave.

[0006] This invention is implemented by constructing a method for constructing tunnels with extremely irregular local erosion and severe dissolution, characterized by the following construction operations: 1) Conduct surveys and measurements to assess the extent and severity of the encroachment and the hazard posed by the hanging object; Before each cycle, it is necessary to conduct surveys and measurements, assess the climate inside the cave, and evaluate the hazards of soluble hanging objects such as stalactites, stalactites, stone flags, stone curtains, stone waterfalls, cave shields, and calcium slabs caused by construction disturbance. At the same time, the excavation range of the intruding rock should be designed. 2) Excavation of intrusive rock; Based on the extent and severity of the intrusive rock, determine the excavation method, and ensure that the excavation space is sufficient for one cycle of installation; mechanical excavation can be used, or low-explosive-consumption blasting with a maximum charge in the smallest section can be employed; the contact surface between the steel reinforcement cage and the rock mass should be rough and located within the radial plane of the tunnel; a foundation similar to an arch can be constructed using a pneumatic drill. 3) Construct targeted and appropriate steel reinforcement cages and L-shaped formwork; The formwork trolley stands on the tunnel invert arch with its front end cantilevered and equipped with a liftable formwork support device. The liftable and retractable L-shaped formwork support structure ensures the axial stability of the formwork. Each cycle of the steel frame can be made in multiple sections, and some steel bars can be welded to the ends and bolted to the steel bar connection plate; 4) Connection of adjacent cyclic thick steel bars; To increase overall stability, at least one thick steel bar should run through each adjacent cycle; corrugated pipes can be installed first, and grouting can be performed after the steel bar is inserted. 5) Formwork trolley; The invert arch pouring and backfilling, steel arch frame erection and concrete spraying follow closely after the karst cave treatment; in order to avoid exposure to corrosive hanging objects such as stalactites, stalactites, stalactites, stalactites, stalactites, cave shields, and calcium slabs, and to require good working environment conditions, a specially made steel reinforcement skeleton and "L"-shaped formwork support trolley for the extremely irregular local intrusion and severe corrosion of the tunnel lining are used. The front end of the support trolley is cantilevered and equipped with a liftable support device. The liftable and retractable L-shaped support structure ensures that the workers have a protective roof and are safe. The formwork trolley is located in the tunnel and is stabilized by hydraulic pressure against the tunnel walls on all sides and in front and behind it. Based on the concrete pump truck, concrete can be poured from the top of the "L" shaped formwork in reverse, and then the concrete surface can be vibrated. 6) Treatment of intrusive karst caves and surrounding normal rock mass; Because of the soluble rock mass, calcium carbonate is easy to solidify and also easy to dissolve. Therefore, a certain space needs to be left between the initial support and the surrounding rock, and filled with 0.01m of non-soluble gravel to form its passage. After the steel arch frame is erected, the gravel can be put directly in. Its water enters the ditch through the drainage pipe at the bottom of the wall. Therefore, a certain compensation space should be left in the excavation outline of the soluble tunnel. To avoid formwork bursting during pouring, the space can be arranged from the skeleton towards the rock mass, with gravel, stones, and concrete piled up in ascending order of particle size.

[0007] The present invention has the following advantages: The present invention provides a construction method for tunnels with extremely irregular local erosion and severe dissolution, the characteristics of which are as follows; To ensure safety, reliability, ease of operation, high quality, and low cost, a specific tunnel lining steel reinforcement cage and "L"-shaped formwork are constructed. Its specific characteristics are as follows: 1. The steel reinforcement cage and L-shaped formwork are fabricated outside the tunnel or inside the tunnel where secondary lining has already been constructed. The fabrication is safe, reliable, and of high quality. 2. The process of handling the encroachment and installing the steel reinforcement cage and "L"-shaped formwork, as well as pouring and dismantling the formwork, is carried out from the outside or from the already completed secondary lining tunnel into the encroaching karst cave. The equipment and workers do not need to be exposed to karst materials such as stalactites, stalactites, stalactites, stalactites, stalactites, stalactites, cave shields, and calcium plates, thus ensuring construction safety. 3. Before each cycle, a survey and measurement should be conducted to create a targeted and appropriate steel reinforcement cage and "L" shaped formwork; 4. Short-cycle advance is required for handling encroachment, as well as for the installation of the reinforcing steel cage and L-shaped formwork, and for pouring and demolding. 5. To ensure that the concrete reaches the top or has a certain thickness, the length of the steel reinforcement cage and L-shaped formwork must be controlled within a certain range to avoid voids or insufficient thickness due to the slope of the concrete flow. 6. The steel reinforcement cage and L-shaped formwork are located outside the initial support of a typical karst tunnel; 7. Anchor the steel reinforcement cage with anchor bolts of a certain length, depending on the extent and severity of the corrosion. 8. Treatment of intrusion and non-intrusion contact surfaces: ensure that the surface is rough and within the radial plane of the tunnel, and anchor the steel reinforcement cage on the surface, and couple the surface with the L-shaped formwork. 9. Before the lining is lowered, well-graded insoluble crushed stone, preferably gravel, can be used to fill the sides and top of the lining to avoid impact from soluble falling objects during operation.

[0008] 10. The L-shaped formwork is supported by a liftable cantilever support structure at the front end of the support trolley; 11. Water outside the protective roof flows along the protective roof towards the bottom of the tunnel wall in the soluble surrounding rock or cavities. The soluble water is then guided to a ditch from the bottom of the tunnel wall, so there is no need to construct a circumferential water diversion facility. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the contact surface between the steel reinforcement cage and the rock mass; Figure 2 This is a diagram illustrating the fabrication and installation of an L-shaped template; Figure 3 These are structural diagrams of each section of the steel reinforcement cage; Figure 4 This is a schematic diagram of the connection between adjacent cyclic thick steel bars; Figure 5 This is a schematic diagram of the formwork support trolley structure; Figure 6 It is a diagram of the steel reinforcement skeleton and "L"-shaped template of a tunnel lining with extremely irregular local encroachment and severe dissolution. Detailed Implementation

[0010] The following will be combined with the appendix Figures 1-6 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.

[0011] To address the aforementioned limitations of existing methods, this invention provides a construction method for tunnels with extremely irregular local erosion and severe dissolution. The characteristics of this construction method are as follows: To ensure safety, reliability, ease of operation, high quality, and low cost, a specific tunnel lining steel reinforcement cage and "L"-shaped formwork are constructed. Its specific characteristics are as follows: 1. The steel reinforcement cage and "L"-shaped formwork are fabricated outside the tunnel or inside the tunnel where secondary lining has been constructed. The fabrication is safe, reliable, and of high quality. 2. The process of handling the encroachment and installing the steel reinforcement cage and L-shaped formwork, as well as pouring and dismantling the formwork, is carried out from the outside or from the already completed secondary lining tunnel into the encroaching karst cave. The equipment and workers do not need to be exposed to karst materials such as stalactites, stalactites, stalactites, stalactites, stalactites, stalactites, cave shields, and calcium plates, thus ensuring construction safety. 3. Before each cycle, a survey and measurement should be conducted to create a targeted and appropriate steel reinforcement cage and L-shaped formwork; 4. Short-cycle advance is required for handling encroachment, as well as for the installation of the reinforcing steel cage and L-shaped formwork, and for pouring and demolding. 5. To ensure that the concrete reaches the top or has a certain thickness, the length of the steel reinforcement cage and the "L" shaped formwork must be controlled within a certain range to avoid voids or insufficient thickness due to the slope of the concrete flow. 6. The steel reinforcement cage and the "L"-shaped formwork are located outside the initial support of a typical karst tunnel; 7. Anchor the steel reinforcement cage with anchor bolts of a certain length, depending on the extent and severity of the corrosion. 8. Treatment of intrusion and non-intrusion contact surfaces: ensure that the surface is rough and within the radial plane of the tunnel, and anchor the steel reinforcement cage on the surface, and couple the surface with the L-shaped formwork. 9. Before the lining is lowered, well-graded insoluble crushed stone, preferably gravel, can be used to fill the sides and top of the lining to avoid impact from soluble falling objects during operation.

[0012] 10. The L-shaped formwork is supported by a liftable cantilever support structure at the front end of the support trolley; 11. Water outside the protective roof flows along the protective roof towards the bottom of the tunnel wall in the soluble surrounding rock or cavities. The soluble water is then guided to a ditch from the bottom of the tunnel wall, so there is no need to construct a circumferential water diversion facility.

[0013] Therefore, each cycle is protected by the previous cycle, ensuring safety and improving construction conditions. It is not only easy to operate and meets quality standards, but also inexpensive and efficient in terms of progress.

[0014] The following is a detailed explanation of the construction method for tunnels with extremely irregular local encroachment and severe erosion. (a) Construction Basis: The construction of the lining is to prevent falling objects from causing injury or damage to personnel and ensure the safety of workers. When advancing from a safe tunnel with a protected lining to a severely encroaching karst cave, the lining pouring formwork must be made into an L-shaped formwork, and the steel reinforcement cage must be anchored to the contact surface with the karst cave.

[0015] (ii) Controlled blasting excavation and lining support method for tunnel arch sections: 1. Conduct surveys and measurements to assess the extent and severity of the encroachment and the hazard posed by the hanging object; Before each cycle, it is necessary to conduct surveys and measurements, assess the climate inside the cave, and evaluate the hazards of soluble hanging objects such as stalactites, stalactites, stone flags, stone curtains, stone waterfalls, cave shields, and calcium slabs caused by construction disturbance. At the same time, the excavation range of the intruding rock should be designed.

[0016] 2. Excavation of intrusive rock; Based on the extent and severity of the intrusive rock, determine the excavation method, ensuring the excavation space is sufficient for one cycle of installation. Mechanical excavation or low-explosive-consumption blasting with a smaller maximum charge per section can be used.

[0017] The contact surface between the steel reinforcement cage and the rock mass is rough and located within the radial plane of the tunnel. A foundation similar to an arch can be formed using a pneumatic drill. Figure 1 The contact surface between the steel reinforcement cage and the rock mass.

[0018] 3. Construct targeted and appropriate steel reinforcement cages and L-shaped formwork; Figure 2 L-shaped formwork fabrication and installation. The formwork trolley stands on the tunnel invert arch, with the front end cantilevered, and is equipped with a liftable formwork support device. The liftable and retractable L-shaped formwork structure ensures the axial stability of the formwork. Figure 3 Structural diagram of each section of the steel reinforcement cage.

[0019] Each cycle of the steel frame can be made in multiple sections, and some of the steel bars can be welded to the ends and bolted to the steel bar connection plate.

[0020] 4. Connection of adjacent cyclic thick steel bars; To increase overall stability, at least one thick steel bar should run through each adjacent cycle. Corrugated pipes can be installed first, and grouting can be performed after the steel bar is inserted.

[0021] 5. Formwork trolley; The invert arch pouring and backfilling, steel arch frame erection and concrete spraying follow closely after the karst cave treatment. To avoid exposure to corrosive hanging objects such as stalactites, stalactites, stone flags, stone curtains, stone waterfalls, cave shields, and calcium slabs, and to require relatively good working environment conditions, a specially designed steel reinforcement skeleton and "L"-shaped formwork support trolley were constructed for the extremely irregular, locally intrusive, and severely corrosive tunnel lining. The front end of the support trolley is cantilevered and equipped with a liftable support device. The liftable and retractable L-shaped support structure ensures the safety of the workers with a protective roof.

[0022] The formwork trolley is located in the tunnel and is stabilized by hydraulic pressure from the tunnel walls on all sides and in front and behind it. Figure 5 Schematic diagram of the formwork trolley structure Based on the concrete pump truck, concrete can be poured from the top of the L-shaped formwork in reverse, and then the concrete surface is vibrated.

[0023] 6. Treatment of intrusive karst caves and surrounding normal rock mass; Because calcium carbonate in soluble rock masses is easily consolidated and dissolved, a certain space needs to be left between the initial support and the surrounding rock, filled with 0.01m of non-soluble gravel to form a channel. After the steel arch frame is erected, the gravel can be placed directly inside. Water enters the drainage ditch through the drainage pipes at the bottom of the wall; therefore, a certain amount of compensation space should be left in the excavation outline of the soluble tunnel.

[0024] To avoid formwork bursting during pouring, the space is constructed by stacking gravel and stones in ascending order of particle size from the framework towards the rock mass. Concrete can also be used.

[0025] 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 method for constructing tunnels with extremely irregular local erosion and severe dissolution, characterized in that; The construction procedure is as follows; 1) Conduct surveys and measurements to assess the extent and severity of the encroachment and the hazard posed by the hanging object; Before each cycle, it is necessary to conduct surveys and measurements, assess the climate inside the cave, and evaluate the hazards of stalactites, stalactites, stone flags, stone curtains, stone waterfalls, cave shields, calcium slabs, and soluble hanging objects under construction disturbance. At the same time, the excavation range of the intruding rock should be designed. 2) Excavation of intrusive rock; Based on the extent and severity of the intrusive rock, the excavation method is determined, and the excavation space is designed to accommodate one cycle of installation. Mechanical excavation or low-explosive-consumption blasting with the largest single charge in the smallest section is employed. The contact surface between the steel reinforcement cage and the rock mass is rough and located within the radial plane of the tunnel. A foundation similar to an arch is constructed using a pneumatic drill. 3) Construct targeted and appropriate steel reinforcement cages and L-shaped formwork; The steel reinforcement cage and L-shaped formwork are fabricated outside the tunnel or inside the tunnel where the secondary lining has been constructed; the steel reinforcement cage and L-shaped formwork are located outside the initial support of ordinary karst tunnels; in order to ensure the pouring reaches the top or a certain thickness, the length of the steel reinforcement cage and L-shaped formwork must be controlled within a certain length to avoid voids or insufficient thickness due to the slope of concrete flow. The formwork trolley stands on the tunnel invert arch with its front end cantilevered and equipped with a liftable formwork support device. The L-shaped formwork support structure, which can be raised and lowered, ensures the axial stability of the formwork. Each cycle of the steel reinforcement cage consists of multiple sections, with some steel reinforcement ends welded to bolt-connected steel reinforcement connection plates. Depending on the extent and severity of the corrosion, anchor bolts of a certain length are used to anchor the steel reinforcement cage. 4) Connection of adjacent cyclic thick steel bars; To increase overall stability, at least one thick steel bar should run through each adjacent cycle; corrugated pipes should be installed first, and grouting should be performed after the steel bar is inserted. 5) Construction of the formwork trolley; The invert arch pouring and backfilling, steel arch frame erection and concrete spraying follow closely after the karst cave treatment; in order to avoid exposure to stalactites, stalactites, stone flags, stone curtains, stone waterfalls, cave shields, calcium slabs and other corrosive hanging objects, and to require good working environment conditions, a steel reinforcement skeleton and L-shaped formwork support trolley are made for the extremely irregular local intrusion and severe corrosion of the tunnel lining. The front end of the support trolley is cantilevered and equipped with a liftable support device. The L-shaped support structure can be raised and lowered to ensure the safety of the workers with a protective roof. The formwork trolley is located in the tunnel and is stabilized by hydraulic pressure against the tunnel walls on all sides and in front and behind it. Concrete is poured from the top of the L-shaped formwork in reverse direction using a concrete pump truck, and then the concrete surface is vibrated. The process of handling intrusion, installing the steel reinforcement cage and "L"-shaped formwork, as well as pouring and dismantling the formwork, is carried out from the outside or from inside the already completed secondary lining tunnel into the intrusion karst cave. As a result, the equipment and workers do not need to be exposed to the karst materials such as stalactites, stalactites, stalactites, stalactites, stalactites, cave shields, and calcium slabs, thus ensuring construction safety. Short-cycle advance is required to handle encroachment, as well as the installation of the steel reinforcement cage and L-shaped formwork, and the pouring and demolding processes. The intrusion and non-intrusion contact surfaces are treated to ensure that the surface is rough and within the radial plane of the tunnel, and the steel reinforcement skeleton is anchored on the surface, and the surface is coupled to the L-shaped formwork. 6) Treatment of intrusive karst caves and surrounding normal rock mass; Because of the soluble rock mass, calcium carbonate is easy to solidify and also easy to dissolve. Therefore, a certain space needs to be left between the initial support and the surrounding rock, which is filled with non-soluble gravel with a particle size of 0.01m to form its channel. After the steel arch frame is erected, the gravel can be put directly in. Its water enters the ditch through the drainage pipe at the bottom of the wall. A certain compensation space should be left in the excavation outline of the soluble tunnel. To avoid bursting during pouring, the space is constructed by stacking gravel, stones, and concrete from the skeleton towards the rock mass, with the particle size increasing.

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