Construction Method for Solution Cavity Section of Long and Water-rich Karst Tunnel

Abstract

The present invention discloses a construction method for the solution cavity section of a long and water-rich karst tunnel, which is divided into two cases: the treatment of large karst collapse cavities at the vault and the treatment of karst pipeline water. For the treatment of large karst collapse cavities at the vault, it includes the following steps: A1, advanced geological prediction; A2, advanced support for large karst collapse cavities; A3, excavation and support of the tunnel body. For the treatment of karst pipeline water at the vault, arch waist or side wall, it includes the following steps: B1, conduct observations for one quarter. If there is no water in the karst pipeline, use pumped concrete to seal the dry karst cave at this place; B2, then it is further divided into the water gushing from the karst pipeline on the left side of the tunnel and the water gushing from the karst pipeline on the right side of the tunnel, with different drainage structures. It can quickly carry out the treatment of solution cavities and water disasters, ensuring fast and efficient excavation and safe and reliable operation in the later stage.

Description

Technical Field

[0001] The invention relates to a tunnel construction structure, and is specifically applicable to a long and large water-rich karst tunnel, in particular to a construction method of a karst cavity section. Background Art

[0002] With the rapid development of the national economy, the level of our transportation infrastructure is also constantly improving. As a very important part of the transportation field, tunnels are rapidly increasing in the trend of "long, large, and deep", accompanied by various water hazards encountered in the construction of long and rich karst tunnels, as well as the problem of cavity treatment during construction. Although there are relevant studies in the industry, they all remain at the conventional treatment and waterproofing methods, and cannot fundamentally solve the problem of rapid and efficient excavation of long and rich karst tunnels and safe and reliable operation in the later stage. Summary of the invention

[0003] The present invention aims to provide a method for constructing a cavity section specially used for a long and water-rich karst tunnel, which can quickly carry out cavity treatment and water hazard treatment, and ensure rapid and efficient excavation and safe and reliable operation in the later stage.

[0004] To this end, the technical solution adopted by the present invention is: a method for constructing a karst cavity section of a long and water-rich karst tunnel, wherein the long and water-rich karst tunnel adopts a single-hole double-line structure, the length of which is greater than 20 km, the side away from the flat guide is the right line of the tunnel, and the side close to the flat guide is the left line of the tunnel, and the method for constructing a karst cavity section of a long and water-rich karst tunnel is divided into two situations: treatment of large karst collapse cavities in the vault and treatment of karst pipeline water;

[0005] The treatment of the large karst collapse cavity of the vault includes the following steps:

[0006] A1. Advanced geological forecast;

[0007] During the construction of Changda Fushui karst tunnels, when encountering a large karst collapse cavity on the arch, the excavation of the face is suspended, and at least three of the following methods, including TSP, transient electromagnetic, geological radar, and horizontal drilling coring, are used to detect the surrounding rock in front of the face to determine the subsequent collapse cavity advance support and tunnel excavation support parameters;

[0008] A2. Advance support of large karst collapse cavity;

[0009] A2.1. If the water pressure in a large karst collapse cavity is too high, a small conduit is installed above the tunnel face after the water pressure is reduced, and then a steel frame is welded. The small conduit and the steel frame form a scaffold above the tunnel face. The scaffold is 2-3m beyond the end to be supported. Finally, a steel mesh is hung on the scaffold and concrete is sprayed to prevent the karst collapse cavity from further expanding.

[0010] A2.2. In view of the large scale of the karst collapse cavity, in order to ensure construction safety, the tunnel face is backfilled with backfill using cave slag on site;

[0011] A2.3. The backfilled slag body is trimmed to form a working platform. On the premise of ensuring construction safety, a slurry stop wall is constructed at the breach of the arch. The slurry stop wall is connected and reinforced with the contact surface between the primary support and the slag body with long anchor rods to ensure the stability of the slurry stop wall itself.

[0012] A2.4. When constructing the slurry stop wall, several steel pipes are reserved as concrete pumping pipes, sandblasting pipes and exhaust pipes. The top of the sandblasting pipe is higher than the top of the concrete pumping pipe, which is used to pump backfill the karst collapse cavity;

[0013] A2.5. Use concrete pumping pipes to backfill the karst collapse cavity with fine stone concrete, with the backfill thickness being 5m above the excavation contour line; then use sandblasting pipes to pump mortar to backfill the karst collapse cavity with mortar;

[0014] A2.6. Prepare the required large pipe shed in advance and drill grouting holes on the side walls of the large pipe shed. After the concrete and mortar have finally set, drill holes on the grouting wall within the 120° range of the excavation contour line, and then construct the large pipe shed by following the pipe. Set a steel cage in each large pipe shed and fix it by grouting.

[0015] A3. Excavation and support of the tunnel;

[0016] Carry out tunnel excavation and support according to construction and safety distance restriction requirements;

[0017] For water treatment in vault, haunch or sidewall karst pipes, the following steps are included:

[0018] B1. During the construction of a long and water-rich karst tunnel, if a karst pipe appears on the vault, waist or side wall, observe it for one quarter. If there is no water in the karst pipe, the dry cave at that location is sealed with pumped concrete;

[0019] B2. If water is gushing from the karst pipe on the left side of the tunnel, a transverse drainage channel should be set up at the gushing point to divert the water to the horizontal drainage ditch;

[0020] If the water is gushing from the karst pipeline on the right side of the tunnel, the drainage structure for the water gushing below the arch line is as follows: including excavating a J1 drainage corridor of more than 15m along the karst pipeline, and reserving a pedestrian inspection port on the right side of the J1 drainage corridor, expanding the J1 drainage corridor away from the right side and setting a drop sill corresponding to the outlet, setting a sand settling tank at the lower end of the drop sill, and then leading it to the horizontal drainage ditch through an artificial culvert located under the main tunnel; the drainage structure for the water gushing above the arch line is as follows: including burying The drainage pipe inside the concrete retaining wall of the main tunnel is used to connect the water gushing points above the arch line to the J2 drainage corridor at a position more than 15m inside the right line side. A pedestrian inspection port is reserved on the right line side of the J2 drainage corridor. The J2 drainage corridor is expanded away from the right line side and is provided with a waterfall. A sedimentation tank is set at the lower end of the waterfall, and then the water is led to the flat guide drainage ditch through an artificial culvert located below the main tunnel. The main tunnel and the flat guide of the tunnel both adopt a herringbone slope structure, and each water gushing point adopts down-slope drainage.

[0021] As a preferred embodiment of the above scheme, in step A2.6, after the large pipe rack is constructed, a small pipe with a large external insertion angle is used to strengthen the support.

[0022] More preferably, in step A2.6, the steel cage is composed of four main bars arranged in an annular direction and fixing rings arranged at intervals in the longitudinal direction, and is cylindrical as a whole.

[0023] It is further preferred that, in step A2, the grouting wall is 3m thick, and the long anchor rod between the grouting wall and the contact surface between the primary support and the tunnel slag body is 5m long; when the grouting wall is constructed, 5 Φ125mm steel pipes are reserved as concrete pumping pipes, sandblasting pipes and exhaust pipes; C30 fine stone concrete is used to backfill the karst collapse cavity; in order to install the large pipe shed, the drill bit diameter is 5-10mm larger than the diameter of the large pipe shed, and the drilling external insertion angle is 1-3°; the large pipe shed is Φ108 hot-rolled seamless steel pipe with a circumferential spacing of 40cm and a length of 30m; the grouting holes drilled on the large pipe shed have a hole diameter of 10-16mm, a hole spacing of 15-20cm, a plum blossom-shaped arrangement, the front end is processed into a cone, and 100cm is left at the tail as a grouting section without drilling; the main reinforcement diameter of the steel cage is 18mm, and the steel bars are connected with 5cm long Φ42 steel pipes every 1m apart.

[0024] Further preferably, in step A2, the large pipe shed is installed on site by hammering or drilling, and after the installation of the large pipe shed is completed, the sand and gravel in the large pipe shed are promptly cleaned with high-pressure water, the holes are sealed with reinforced stirrups, and the hole and surrounding cracks are sealed with plastic mud from the reinforced stirrups to the hole mouth; concrete is sprayed near the large pipe shed and on the working face to prevent the working face from collapsing; a ball valve is installed at the tail of the large pipe shed to connect the grouting pipe and exhaust.

[0025] It is further preferred that in step A2, after the large pipe shelf is installed, first check whether the conduit opening meets the sealing standard, and conduct a water pressure test with a pressure of 0.5-1.0 MPa. The large pipe shelf is grouting with cement slurry with a construction ratio of 1:1 by weight. During the grouting process, the surrounding rock conditions of the face are observed in time, and the grouting operation is terminated when either the grouting volume or the pressure reaches the design requirements.

[0026] More preferably, in step B2, for the drainage structure on the left line side of the main tunnel, a grit chamber is provided just below the water gushing point, and the grit chamber is located at the front end of the lateral drainage channel.

[0027] It is further preferred that the artificial culvert adopts a frame culvert or a circular culvert, the drainage pipe adopts a φ100 cm HDPE pipe laid in the concrete retaining wall, the J1 drainage corridor and the J2 drainage corridor are 18m away from the inner wall of the main tunnel, the reserved pedestrian inspection opening is 5m long, the sedimentation tank is 2m deep and 5m wide, the waterfall is 4m wide and 3m high, and it is a 4-6 level waterfall.

[0028] Further preferably, the flat drainage ditch is 3 m wide and 1.3-1.4 m deep.

[0029] It is further preferred that an emergency rescue station is set up in the middle section of the main tunnel where the surrounding rock is good and there is no water gushing, and the emergency rescue station includes a personnel evacuation passage and a smoke exhaust passage; the personnel evacuation passage includes an evacuation platform set up in the emergency rescue station on both sides of the double lines, a number of evacuation transverse passages set up at intervals, and a longitudinal evacuation passage is also set on the outside of the right line, the evacuation transverse passages of the left line are respectively connected to the horizontal guide, and the evacuation transverse passages of the right line are respectively connected to the evacuation longitudinal passages, and the longitudinal evacuation passages are then connected to the horizontal guide through the tunnel top evacuation communication passage; the smoke exhaust passage includes a number of main tunnel smoke exhaust shafts set up at intervals in the emergency rescue station on the main tunnel arch, and a longitudinal smoke exhaust duct is also set between the left line and the horizontal guide, each main tunnel smoke exhaust shaft is connected to the longitudinal smoke exhaust duct through its corresponding transverse smoke exhaust duct, and the longitudinal smoke exhaust duct is then connected to the main tunnel inclined shaft for discharge through the horizontal guide smoke exhaust duct, the horizontal guide smoke exhaust shaft, and the communication smoke exhaust duct. An emergency rescue station is chosen to be set up in the middle section of the main tunnel where the surrounding rock is good and there is no water gushing. The rescue station is set in the center and avoids the water gushing point, providing a reliable and safe escape channel for evacuation and rescue in case of emergency in the tunnel. The personnel evacuation channel is divided into left and right lines, and the personnel of the two lines finally converge at the flat guide; multiple evacuation transverse channels are set up, and passengers getting off different carriages of the train can choose the nearest channel to escape, and the personnel can be evacuated in an orderly manner according to the prescribed route, ensuring timely and efficient evacuation; several main tunnel smoke exhaust shafts are set up at intervals in the main tunnel arch and in the emergency rescue station, and each main tunnel smoke exhaust shaft is connected to the longitudinal smoke exhaust duct through its corresponding transverse smoke exhaust duct, and the longitudinal smoke exhaust duct is then connected to the main tunnel inclined shaft for discharge through the flat guide smoke exhaust duct, the flat guide smoke exhaust shaft, and the connecting smoke exhaust duct in turn; the smoke exhaust channel and the personnel evacuation channel are separated from each other and do not interfere with each other, and use the existing main tunnel inclined shaft for discharge to reduce the construction volume.

[0030] Beneficial effects of the present invention:

[0031] (1) For large karst collapse cavities on the arch, including dry karst cavities and water-gushing karst cavities, large water-gushing cavities need to be treated after the water pressure is reduced. Comprehensive use of advanced geological prediction and large karst collapse cavity advance support can ensure smooth progress and construction safety;

[0032] (2) In terms of specific treatment methods for the large karst collapse cavity on the vault, a scaffolding formed by a small pipe and a steel frame is set up above the tunnel face, and a steel mesh is hung on the scaffolding to spray concrete to prevent the karst collapse cavity from further expanding; the tunnel face is backfilled with counterpressure using the slag on site and repaired to form a working platform, which is then stabilized and reinforced with a grout-stopping wall and long anchor rods, and steel pipes are reserved for double-layer pumping backfilling. A large pipe shed with a built-in steel cage is used for grouting and fixing, etc., to ensure efficient and reliable treatment of the large karst collapse cavity on the vault;

[0033] (3) The drainage structure is divided into the left side of the main tunnel and the right side of the main tunnel. The right side of the main tunnel is further divided into water gushing below the arch line and water gushing above the arch line. Different situations are handled to minimize the construction workload and ensure timely and efficient drainage. At the same time, it can ensure that the gushing water is discharged in time during the later operation process.

[0034] (4) In the drainage structure, drainage corridors, reserved pedestrian inspection ports, waterfalls, sand settling tanks and artificial culverts are added to lead the discharged water to the horizontal drainage ditch through the underground artificial culvert. The function is reliable, maintenance is convenient, drainage is timely, and siltation caused by excessive sediment can be prevented;

[0035] (5) The tunnel main tunnel and horizontal guideway both adopt a herringbone slope structure, and each water gushing point adopts down-slope drainage. If a large amount of water gushing occurs during the later operation, no artificial pump is required to assist in drainage, which has obvious advantages over reverse slope drainage. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the layout of concrete pumping pipes and sandblasting pipes.

[0037] Figure 2 This is the front view of the arrangement of light steel and large pipe racks on the mortar stop wall.

[0038] Figure 3 It is a side view of the arrangement of light steel and large pipe racks on the slurry stop wall.

[0039] Figure 4 This is a schematic diagram of the exploded view of the steel cage built into the large pipe shed.

[0040] Figure 5 This is the emergency rescue station structure for the Changda Fushui karst tunnel.

[0041] Figure 6 It is a drainage structure for water gushing below the arch line on the right side of the main tunnel.

[0042] Figure 7 It is a common drainage structure with water gushing both above and below the arch line on the right side of the main tunnel.

[0043] Figure 8 It is the drainage structure of the Changda Water-Rich Karst Tunnel. DETAILED DESCRIPTION

[0044] The present invention will be further described below by way of embodiments and in conjunction with the accompanying drawings:

[0045] like Figure 5 The long and water-rich karst tunnel shown adopts a single-hole double-line structure, the side away from the flat guide C is the right line of the tunnel, and the side close to the flat guide C is the left line of the tunnel.

[0046] The construction method of the karst cavity section of Changda Fushui karst tunnel is divided into two cases: the treatment of large karst collapsed cavities on the arch and the treatment of karst pipeline water. The large karst collapsed cavities on the arch include dry karst cavities and gushing karst cavities. For large gushing karst cavities, it is necessary to wait until the water pressure is reduced before treatment. Outside the arch, the dry large karst collapsed cavities at the arch waist, side walls and other locations are directly treated by backfilling, and the gushing karst cavities at the arch waist, side walls and other locations are uniformly treated according to the karst pipeline.

[0047] The treatment of the large karst collapse cavity of the vault includes the following steps:

[0048] A1. Advanced geological forecast.

[0049] During the construction of a long and rich karst tunnel, when encountering a large karst collapse cavity on the arch, the excavation of the heading face is suspended, and at least three of TSP, transient electromagnetic, geological radar, and horizontal drilling coring are used to detect the surrounding rock in front of the heading face to determine the subsequent collapse cavity advance support and tunnel excavation support parameters.

[0050] A2. Advance support of large karst collapse cavity.

[0051] A2.1. If the water pressure in a large karst collapse cavity is too high, a small conduit can be installed above the face after the water pressure is reduced, and then a steel frame can be welded. The small conduit and the steel frame form a scaffold above the face, and the scaffold is 2-3m beyond the end to be supported. Finally, a steel mesh is hung on the scaffold and concrete is sprayed to prevent the karst collapse cavity from further expanding. For the remaining water-gushing cavities and dry cavities, a small conduit can be directly installed above the face, and then a steel frame can be welded. The small conduit and the steel frame form a scaffold above the face, and the scaffold is 2-3m beyond the end to be supported. Finally, a steel mesh is hung on the scaffold and concrete is sprayed.

[0052] A2.2. In view of the large scale of the karst collapse cavity, in order to ensure construction safety, the tunnel face is backfilled with cave slag on site, local materials are used, waste is utilized, construction is convenient, and costs are saved.

[0053] A2.3. The backfilled slag body is trimmed to form a working platform. On the premise of ensuring construction safety, a slurry stop wall is constructed at the breach of the arch. The slurry stop wall is connected and reinforced with the contact surface between the primary support and the slag body with long anchor rods to ensure the stability of the slurry stop wall itself.

[0054] A2.4. When constructing the mortar stop wall, reserve several steel pipes as concrete pumping pipes 19, sandblasting pipes 20 and exhaust pipes ( Figure 1 ), wherein the top of the sandblasting pipe is higher than the top of the concrete pumping pipe, which is used to pump backfill the karst collapse cavity.

[0055] A2.5. Use concrete pumping pipes to backfill the karst collapse cavity with fine stone concrete, with the backfill thickness being 5m above the excavation contour line; then use sandblasting pipes to pump mortar to backfill the karst collapse cavity with mortar.

[0056] A2.6. Prepare the required large pipe shed 22 in advance, and drill grouting holes 22a on the side wall of the large pipe shed; after the concrete and mortar are finally set, drill holes in the grouting wall 21 within 120° of the excavation contour line, and then use the following pipe method to construct the large pipe shed 22. A steel cage 23 is set in each large pipe shed, and grouting is performed to fix it. Light steel 24 and long guide tube 25 are pre-buried in the grouting wall 21. The long guide tube 25 is a guide for driving the large pipe shed 22. The inner diameter of the long guide tube 25 is larger than the outer diameter of the large pipe shed 22, forming a casing form; the light steel 24 is arranged at intervals along the extension direction of the long guide tube 25, and the long guide tube 25 is supported below the long guide tube 25, such as Figure 2 , Figure 3 , Figure 4 shown.

[0057] It is best to use small pipes with large external angles to strengthen support after the large pipe rack is constructed in step A2.6.

[0058] Preferably, in step A2.6, the steel cage 23 is composed of four main bars 23a arranged in an annular direction and fixing rings 23b arranged at intervals in the longitudinal direction, and is cylindrical in shape as a whole, such as Figure 4 shown.

[0059] Preferably, in step A2, the grouting wall is 3m thick, and the long anchor rod between the grouting wall and the contact surface between the primary support and the tunnel slag body is 5m long; when constructing the grouting wall, 5 Φ125mm steel pipes are reserved as concrete pumping pipes, sandblasting pipes and exhaust pipes; C30 fine stone concrete is used to backfill the karst collapse cavity; in order to install the large pipe shed, the drill bit diameter is 5-10mm larger than the diameter of the large pipe shed, and the drilling external insertion angle is 1-3°; the large pipe shed is Φ108 hot-rolled seamless steel pipe, with a circumferential spacing of 40cm and a length of 30m; the grouting holes drilled on the large pipe shed have a hole diameter of 10-16mm, a hole spacing of 15-20cm, and a plum blossom-shaped arrangement, the front end is processed into a cone, and 100cm is left at the tail as a grouting section without drilling; the main reinforcement of the steel cage has a diameter of 18mm, and the steel bars are connected with a 5cm long Φ42 steel pipe every 1m.

[0060] Preferably, in step A2, the large pipe shed is installed on site by hammering or drilling, and after the large pipe shed is installed, the sand and gravel in the large pipe shed are cleaned with high-pressure water in time, and the hole is sealed with reinforced stirrups. The hole and surrounding cracks are sealed with plastic mud from the reinforced stirrups to the hole mouth; concrete is sprayed near the large pipe shed and on the working surface to prevent the working surface from collapsing; a ball valve is installed at the tail of the large pipe shed to connect the grouting pipe and exhaust.

[0061] In step A2, after the large pipe shelf is installed, first check whether the conduit opening meets the sealing standard and conduct a water pressure test with a pressure of 0.5 to 1.0 MPa. Cement slurry is used for grouting of the large pipe shelf with a construction ratio of 1:1 by weight. During the grouting process, observe the surrounding rock conditions of the face in a timely manner. When either the grouting volume or the pressure reaches the design requirements, the grouting operation is terminated.

[0062] A3. Excavation and support of the tunnel body.

[0063] According to the construction and safety distance restriction requirements, tunnel excavation and support are carried out.

[0064] For water treatment in vault, haunch or sidewall karst pipes, the following steps are included:

[0065] B1. During the construction of a long and water-rich karst tunnel, if a karst pipe appears on the arch, waist or side wall, observation should be carried out for one quarter. If there is no water in the karst pipe, the dry cave at that location should be sealed with pumped concrete.

[0066] B2. If water gushes from the karst pipeline on the left side of the tunnel, since the left line of the main tunnel is close to the horizontal guide C, a transverse drainage channel is set at the gushing point to divert the water to the horizontal guide drainage ditch 15, which has a simple structure. Preferably, a grit chamber 18 is also set just below the gushing point, and the grit chamber 18 is located at the front end of the transverse drainage channel.

[0067] If the water is gushing from the karst pipe on the right side of the tunnel, it can be divided into water gushing below the arch line and water gushing above the arch line. The drainage structure for water gushing below the arch line is: combined with Figure 6 — Figure 8 As shown, the J1 drainage corridor 11, which is excavated more than 15m along the karst pipeline, needs to be excavated first along the karst pipeline to form enough space to arrange the reserved pedestrian inspection port 12, the water drop 13, and the sand settling tank 18. A pedestrian inspection port 12 is reserved on the right side of the J1 drainage corridor 11 to facilitate maintenance. The J1 drainage corridor 11 is expanded and excavated away from the right side and a water drop 13 corresponding to the outlet is set. A sand settling tank 18 is set at the lower end of the water drop 13, and then connected to the flat drainage ditch 15 through an artificial culvert 14 located below the main tunnel.

[0068] like Figure 8As shown, the drainage structure for water gushing above the arch line on the right line side of the main tunnel is: including a drainage pipe 16 buried in the concrete retaining wall of the main tunnel, and the drainage pipe 16 is used to connect the water gushing point above the arch line to the J2 drainage corridor 17 at a position more than 15m inside the right line side. A pedestrian inspection port 12 is reserved on the right line side of the J2 drainage corridor 17. The J2 drainage corridor 17 is expanded away from the right line side and is provided with a drop sill 13. A sand settling tank 18 is set at the lower end of the drop sill 13, and then connected to the flat drainage ditch 15 through an artificial culvert 14 located below the main tunnel. During the specific construction, it is still necessary to excavate along the karst pipeline to find the water gushing point above the arch line. After installing the drainage pipe 16, the water gushing point of the arch is blocked. The drainage pipe 16 serves to drain the water gushing point of the arch to the J2 drainage corridor 17. If there is water gushing above the arch line and water gushing below the arch line on the same section on the right side of the main tunnel, the two water gushing places share the same drainage gallery, waterfall, sedimentation tank and artificial culvert to further simplify the structure. The artificial culvert 14 is preferably a frame culvert or a circular culvert, and the drainage pipe 16 is laid in the concrete retaining wall with a φ100cm HDPE pipe. The J1 drainage gallery 11 and the J2 drainage gallery 17 are 18m away from the inner wall of the main tunnel, and the reserved pedestrian inspection port 12 is 5m long, the sedimentation tank 18 is 2m deep and 5m wide, and the waterfall 13 is 4m wide and 3m high, which is a 4-6 level waterfall, but not limited to this.

[0069] like Figure 6 As shown, during the construction of the flat guide C, large water gushing points will also appear, which poses a great safety hazard to the construction workers. The traditional treatment method is to drill holes and pump water. The present invention adopts the method of avoiding large water gushing points for construction, and regards it as the unexcavated section C1 of the original flat guide, and does not perform excavation construction. At a position 30-50m before and after the water gushing point, a turn is formed to form a horizontal guide section C2 that avoids the gushing point and is parallel to the unexcavated section C1 of the original flat guide; the tunnel main hole and the flat guide C both adopt a herringbone slope structure, and each water gushing point adopts down-slope drainage. The entire drainage structure does not require a pump, avoiding the problems of heavy workload, high cost and low efficiency caused by reverse slope drainage.

[0070] For tunnels longer than 20 km, emergency rescue stations are specially designed to ensure that personnel can be evacuated and rescued in time when an emergency occurs in the tunnel. Emergency rescue stations are set up in the middle section of the tunnel with good surrounding rock and no water inrush. Emergency rescue stations are divided into personnel evacuation channels and smoke exhaust channels.

[0071] like Figure 5As shown, the personnel evacuation passage includes an evacuation platform 9 set up in the emergency rescue station on both sides of the double track, and a number of evacuation transverse passages 1 set up at intervals in the emergency rescue station on both sides of the double track. An evacuation longitudinal passage 2 is also set up on the outside of the right track. The evacuation transverse passages 1 of the left track are respectively connected to the horizontal guide C nearby, and the evacuation transverse passages 1 of the right track are respectively connected to the evacuation longitudinal passages 2 nearby. The evacuation longitudinal passages 2 are then connected to the horizontal guide C through the tunnel top evacuation communication passage 3, so that all the personnel on the right and left tracks can be evacuated and rescued using the horizontal guide.

[0072] Preferably, the total length of the emergency rescue station is 550m, and an evacuation cross passage 1 is set up every 50m on both sides of the double line, with a total of 22 evacuation cross passages 1 for the double line, 11 on one side; and the evacuation cross passages 1 on the A and left lines are set up accordingly.

[0073] The smoke exhaust channel includes several main tunnel smoke exhaust shafts 4 arranged at intervals in the main tunnel arch and in the emergency rescue station, and a longitudinal smoke exhaust duct 5 is also arranged between the left line and the horizontal guide C. Each main tunnel smoke exhaust shaft 4 is connected to the longitudinal smoke exhaust duct 5 through its corresponding horizontal smoke exhaust duct 6. The longitudinal smoke exhaust duct 5 is then connected to the main tunnel inclined shaft 10 through the horizontal guide smoke exhaust duct, the horizontal guide smoke exhaust shaft 7, and the communication smoke exhaust duct 8 in turn for discharge. Finally, the existing main tunnel inclined shaft 10 is directly used for smoke exhaust.

[0074] Preferably, a main tunnel smoke exhaust shaft 4 is provided at every 100 m on the main tunnel arch, and each main tunnel smoke exhaust shaft 4 is located between two adjacent smoke exhaust shafts 4. In a train accident, smoke exhaust is required when a fire occurs to ensure that the personnel in the rescue passage do not become unconscious due to excessive smoking.

[0075] A protective door partition wall (not shown in the figure) is arranged in each evacuation horizontal passage 1, at the intersection of the tunnel top evacuation communication passage 3 and the flat guide C, at the intersection of the longitudinal smoke exhaust duct 5 and the flat guide C, and at the intersection of the communication smoke exhaust duct 8 and the flat guide C. The protective door partition walls are provided with protective door openings and air valve holes.

[0076] An emergency rescue station is chosen to be set up in the middle section of the main tunnel where the surrounding rock is good and there is no water gushing. The rescue station is set in the center and avoids the water gushing point, providing a reliable and safe escape channel for evacuation and rescue in case of emergency in the tunnel. The personnel evacuation channel is divided into A and left line, and the personnel of the two lines finally converge at the flat guide; multiple evacuation transverse channels are set up, and passengers getting off different carriages of the train can choose the nearest channel to escape, and the personnel can be evacuated in an orderly manner according to the prescribed route, ensuring timely and efficient evacuation; several main tunnel smoke exhaust shafts are set up at intervals in the main tunnel arch and in the emergency rescue station, and each main tunnel smoke exhaust shaft is connected to the longitudinal smoke exhaust duct through its corresponding transverse smoke exhaust duct, and the longitudinal smoke exhaust duct is then connected to the main tunnel inclined shaft for discharge through the flat guide smoke exhaust duct, the flat guide smoke exhaust shaft, and the connecting smoke exhaust duct in turn; the smoke exhaust channel and the personnel evacuation channel are separated from each other and do not interfere with each other, and use the existing main tunnel inclined shaft for discharge to reduce the construction volume.

Claims

1. A construction method for the solution cavity section of a long and water-rich karst tunnel. The long and water-rich karst tunnel adopts a single-tunnel double-track structure with a length greater than 20 km. The side away from the parallel adit (C) is the right tunnel line, and the side close to the parallel adit (C) is the left tunnel line. The construction method for the solution cavity section of the long and water-rich karst tunnel is divided into two cases: the treatment of large karst collapse cavities at the vault and the treatment of karst pipeline water. It is characterized in that: For the treatment of large karst collapse cavities at the vault, it includes the following steps: A1. Advanced geological prediction; During the construction of the long and water-rich karst tunnel, when a large karst collapse cavity is encountered at the vault, the excavation of the heading face is suspended, and at least three of TSP, transient electromagnetic method, ground penetrating radar, and horizontal drilling coring are adopted to detect the surrounding rock in front of the heading face to determine the subsequent advanced support parameters for the collapse cavity and the support parameters for the tunnel body excavation. A2. Advanced support for large karst collapse cavities; A2.

1. If the water pressure in the large karst collapse cavity is too high, after the water pressure drops, install small pipes above the heading face, and then weld steel frames. The small pipes and the steel frames form a shed above the heading face, and the shed extends 2 - 3 m beyond the end to be supported. Finally, hang a steel mesh and spray concrete on the shed to prevent the karst collapse body from expanding further. A2.

2. In view of the large scale of the karst collapse body, to ensure construction safety, the heading face is backfilled with tunnel muck on site. A2.

3. Trim the backfilled tunnel muck body to form a working platform. On the premise of ensuring construction safety, construct a grouting stop wall at the breach at the vault. Long bolts are used to connect and reinforce the contact surfaces between the grouting stop wall, the initial support, and the tunnel muck body to ensure the stability of the grouting stop wall itself. A2.

4. When constructing the grouting stop wall, reserve several steel pipes as concrete pumping pipes, sandblasting pipes, and exhaust pipes. The top of the sandblasting pipe is higher than the top of the concrete pumping pipe, which is used for pumping and backfilling the karst collapse cavity. A2.

5. Use the concrete pumping pipe to backfill the karst collapse cavity with fine aggregate concrete, and the backfill thickness is 5 m above the excavation contour line; then use the sandblasting pipe to pump mortar for mortar backfilling of the karst collapse cavity. A2.

6. Process the required large pipe shed in advance and drill grouting holes on the side wall of the large pipe shed; after the concrete and mortar have set, drill holes in the 120° range of the excavation contour line for the grouting stop wall, and then construct the large pipe shed by the pipe following method. A steel reinforcement cage is set in each large pipe shed and grouted for fixation. A3. Tunnel body excavation support; According to the requirements of construction and safety distance limitations, carry out tunnel body excavation support. For the treatment of karst pipeline water at the vault, arch waist, or side wall, it includes the following steps: B1. During the construction of the long and water-rich karst tunnel, when karst pipelines appear at the vault, arch waist, or side wall, conduct observations for one quarter. If there is no water in the karst pipeline, block the dry karst cave at this place with pumped concrete. B2. If the karst pipeline on the left side of the tunnel gushes water, set up a transverse drainage channel at the water gushing point to lead the water to the parallel adit drainage ditch (15). If there is water gushing from the karst pipeline on the right side of the tunnel, the water drainage structure for the water gushing below the springing line is as follows: It includes a J1 drainage corridor (11) excavated along the karst pipeline for more than 15 m, and a pedestrian inspection opening (12) is reserved on the right-line side of the J1 drainage corridor (11). On the side of the J1 drainage corridor (11) far from the right line, it is excavated and widened to set a drop weir (13) corresponding to the water outlet. A grit chamber (18) is set at the lower end of the drop weir (13), and then it is led to the pilot tunnel drainage ditch (15) through an artificial culvert (14) located below the main tunnel; the water drainage structure for the water gushing above the springing line is as follows: It includes a drainage pipe (16) buried in the concrete retaining wall of the main tunnel. The drainage pipe (16) is used to connect the water gushing point above the springing line to a J2 drainage corridor (17) at a position more than 15 m inside the right-line side. A pedestrian inspection opening (12) is reserved on the right-line side of the J2 drainage corridor (17). On the side of the J2 drainage corridor (17) far from the right line, it is excavated and widened to set a drop weir (13). A grit chamber (18) is set at the lower end of the drop weir (13), and then it is led to the pilot tunnel drainage ditch (15) through an artificial culvert (14) located below the main tunnel; both the main tunnel and the pilot tunnel (C) of the tunnel adopt a herringbone slope structure, and each water gushing point adopts drainage along the slope.

2. The construction method for the solution cavity section of a long water-rich karst tunnel according to claim 1, characterized in that: In step A2.6, after the large pipe shed is constructed, small pipes with a large external insertion angle are used for enhanced support.

3. The construction method for the solution cavity section of a long water-rich karst tunnel according to claim 1, characterized in that: In step A2.6, the steel reinforcement cage is composed of four main reinforcements arranged circumferentially and fixed rings arranged at intervals longitudinally, and is in an overall cylindrical shape.

4. The construction method for the solution cavity section of a long water-rich karst tunnel according to claim 1, characterized in that: In step A2, the grouting stop wall is 3 m thick, and the long anchor rods between the grouting stop wall and the contact surfaces of the primary support and the tunnel muck are 5 m long; when constructing the grouting stop wall, 5 steel pipes with a diameter of Φ125 mm are reserved as concrete pumping pipes, sandblasting pipes and exhaust pipes; the karst collapse cavity is backfilled with C30 fine aggregate concrete; in order to install the large pipe shed, the drill bit diameter is 5 - 10 mm larger than the large pipe shed diameter, and the external insertion angle of the drilling is 1 - 3°; the large pipe shed is a Φ108 hot-rolled seamless steel pipe, with a circumferential spacing of 40 cm and a length of 30 m; the grouting holes drilled on the large pipe shed have a diameter of 10 - 16 mm, a hole spacing of 15 - 20 cm, and are arranged in a plum blossom shape. The front end is processed into a conical shape, and 100 cm is reserved at the tail as a grouting stop section without drilling; the main reinforcement diameter of the steel reinforcement cage is 18 mm, and the steel bars are connected with 5 cm long Φ42 steel pipes at an interval of 1 m.

5. The construction method for the solution cavity section of a long water-rich karst tunnel according to claim 1, characterized in that: In step A2, the large pipe shed is installed on-site by being driven in with a hammer or jacked in with a drill rig. After the installation of the large pipe shed is completed, the sand and gravel inside the large pipe shed are promptly cleaned with high-pressure water, and the holes are sealed using reinforcing stirrups. The section from the reinforcing stirrups to the hole opening is sealed with plastic clay to block the hole opening and surrounding fissures; shotcrete is sprayed near the large pipe shed and at the working face to prevent the collapse of the working face; a ball valve is installed at the tail of the large pipe shed for connecting the grouting pipe and exhausting air.

6. The construction method for the solution cavity section of a long and water-rich karst tunnel according to claim 1, characterized in that: in step A2, after the installation of the large pipe shed is completed, first check whether the orifice of the conduit reaches the airtight standard, conduct a water pressure test with a pressure of 0.5 - 1.0 MPa. The large pipe shed grouting uses cement slurry with a construction ratio of 1:1 by weight. During the grouting process, observe the surrounding rock conditions of the heading face in a timely manner, and end the grouting operation when either the slurry absorption amount or the pressure reaches the design requirements.

7. The construction method for the solution cavity section of a long and water-rich karst tunnel according to claim 1, characterized in that: in step B2, for the water drainage structure on the left line side of the main tunnel, a grit chamber (18) is also provided directly below the water gushing point, and the grit chamber (18) is located at the front end of the transverse drainage channel.

8. The construction method for the solution cavity section of a long and water-rich karst tunnel according to claim 1, characterized in that: the artificial culvert (14) adopts a frame culvert or a circular culvert, the drainage pipe (16) is a φ100 cm HDPE pipe laid in the concrete retaining wall, the J1 drainage corridor (11) and the J2 drainage corridor (17) are 18 m away from the inner wall of the main tunnel, the reserved pedestrian inspection opening (12) is 5 m long, the grit chamber (18) is 2 m deep and 5 m wide, and the drop weir (13) is 4 m wide and 3 m high, with a 4 - 6 - level drop.

9. The construction method for the solution cavity section of a long and water-rich karst tunnel according to claim 1, characterized in that: the pilot tunnel drainage ditch (15) is 3 m wide and 1.3 - 1.4 m deep.

10. The construction method for the solution cavity section of a long and water-rich karst tunnel according to claim 1, characterized in that: an emergency rescue station is provided in the middle section of the main tunnel with good surrounding rock and no water gushing. The emergency rescue station includes a personnel evacuation passage and a smoke exhaust passage; the personnel evacuation passage includes evacuation platforms (9) provided on both sides of the double track inside the emergency rescue station, a number of evacuation cross passages (1) arranged at intervals, an evacuation longitudinal passage (2) is also provided on the outer side of the right line. The evacuation cross passages (1) on the left line are respectively connected to the pilot tunnel (C) nearby, and the evacuation cross passages (1) on the right line are respectively connected to the evacuation longitudinal passage (2) nearby. The evacuation longitudinal passage (2) is then connected to the pilot tunnel (C) through the tunnel roof evacuation connection passage (3); the smoke exhaust passage includes a number of main tunnel smoke exhaust shafts (4) arranged at intervals on the crown of the main tunnel inside the emergency rescue station, a longitudinal smoke exhaust duct (5) is also provided between the left line and the pilot tunnel (C). Each main tunnel smoke exhaust shaft (4) is connected to the longitudinal smoke exhaust duct (5) through its corresponding transverse smoke exhaust duct (6), and the longitudinal smoke exhaust duct (5) is then discharged into the main tunnel inclined shaft (10) through the pilot tunnel smoke exhaust duct, the pilot tunnel smoke exhaust shaft (7), and the connection smoke exhaust duct (8) in sequence.

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