Method for draining water from deep water-rich tunnel by construction inclined shaft

Abstract

This invention relates to a method for purifying water from deep, water-rich tunnels using a construction inclined shaft. The method includes the following steps: preliminary purification of the tunnel surface at the support face, including preliminary purification of the tunnel surface along the slope and against the slope; the installation of multi-stage sedimentation tanks within the main tunnel; the installation of water storage tanks and pumping stations; and further purification of tunnel wastewater in an external sedimentation tank. This method effectively removes tunnel construction wastewater through a preliminary purification system on the surface and through internal and external sedimentation and purification systems, ensuring a good construction environment. It has the advantages of being simple and practical, having good drainage and filtration effects, low pollution control costs, and enabling on-site recycling and reuse of wastewater with good overall performance.

Description

Technical Field

[0001] This invention relates to a method for purifying water in deep, water-rich tunnels using a construction inclined shaft. Background Technology

[0002] With the rapid development of my country's expressway industry, expressways are gradually extending into mountainous areas. The unique and complex geological structure of mountainous areas results in tunnels that are much deeper and longer, with abundant groundwater within the tunnels, making construction more difficult. On the other hand, the main line construction of mountain tunnels usually involves excavating from both sides of the mountain until completion. However, to accelerate the construction progress of extra-long tunnels, auxiliary inclined shafts are set up on the mountainside at the upper middle part of the main tunnel to increase the construction face in the middle of the main tunnel. This can speed up the construction progress. These auxiliary inclined shafts are also widely used in the construction of urban subway tunnels.

[0003] When constructing water-rich tunnels with steep longitudinal slopes using inclined shafts, a drainage method needs to be developed by considering factors such as the tunnel's water inflow and the overall longitudinal slope of the inclined shaft. However, the usual method is to discharge wastewater from the tunnel entrances on both sides. There is little research and practice on how to accelerate the drainage process within the main tunnel section of a steep longitudinal slope inclined shaft, and how to treat and reuse construction wastewater to minimize environmental damage. The common practice is to pump wastewater from the main tunnel section into the surface through the inclined shaft, where it undergoes sedimentation and purification. However, this method has the following shortcomings:

[0004] 1. If the wastewater generated is not properly treated, it will seriously pollute the water environment of the area. Traditional sedimentation tanks are used for wastewater treatment, but the treated wastewater does not meet discharge standards. Furthermore, the area is mountainous, making it difficult to select a site for large-scale wastewater treatment equipment.

[0005] 2. The underground drainage distance of the tunnel's inclined shaft is long, with the maximum drainage distance at the shortest mileage being no less than 500 meters. Conventional tunnel groundwater drainage systems cannot meet the requirements, resulting in poor drainage efficiency and ineffective removal of surface water, leading to sewage overflow, muddy ground, and significant impact on construction. Drainage is time-consuming, labor-intensive, and has high pollution control costs. This is especially true in water-rich tunnels where the water flow is large, and conventional drainage systems cannot meet the requirements for timely drainage and waterless tunnel construction.

[0006] 3. Construction in complex geological formations results in groundwater with high sediment content. Ordinary groundwater drainage systems are prone to blockage and have poor filtration and sedimentation effects. The dredging and transportation of sediment within the main tunnel line is a major undertaking. Conventional groundwater drainage systems cannot meet the sedimentation and filtration requirements, and the filtered groundwater still cannot meet the requirements for direct discharge.

[0007] 4. In tunnel construction at high burial depths, the vertical lifting of sewage inside the tunnel requires high equipment head, which conventional groundwater drainage systems cannot meet. Summary of the Invention

[0008] The purpose of this invention is to provide a method for purifying water in deep, water-rich tunnels using a construction inclined shaft, overcoming the above-mentioned shortcomings. This method effectively removes tunnel construction wastewater through a preliminary purification system on the ground and through sedimentation and purification systems inside and outside the tunnel, ensuring a good construction environment. It has the advantages of being simple and practical, having good drainage and filtration effects, low pollution control costs, and enabling on-site recycling and reuse of wastewater with good utilization results.

[0009] Therefore, the present invention provides a method for purifying water in deep, water-rich tunnels using a construction inclined shaft, comprising the following steps:

[0010] (1) Preliminary water purification tunnel surface construction on the support surface, including preliminary water purification tunnel surface construction along the slope and preliminary water purification tunnel surface construction against the slope:

[0011] (a) Construction of the preliminary water purification tunnel surface along the slope: A preliminary water purification surface is set up 5-10m away from the construction support surface. A sloping trench is excavated downwards from the ground 1.8-2m away from the bottom side of the tunnel, forming a water purification trench with an inverted trapezoidal cross-section. The depth of the water purification trench is 1-1.5m lower than the corresponding ground surface of the tunnel, and the angle between the sloping surface and the corresponding ground surface of the tunnel is 30°. 0 ~50 0 The length of the purification water trench is 15-21m. A 0.5-2cm gravel filter layer is filled in the 5-7m section closest to the construction support surface, extending 2-4cm above the corresponding tunnel surface. A 0.3-0.7cm coarse sand filter layer is filled in the 5-7m section behind the gravel filter layer, parallel to the corresponding tunnel surface. A 0.1-0.3cm fine sand filter layer is filled in the 5-7m section behind the coarse sand filter layer, parallel to the corresponding tunnel surface. A 2-4cm thick gravel filter layer covers the upper surfaces of the coarse and fine sand filter layers. A retaining wall is installed between the outer edge of the water inlet of the purification water trench and the corresponding tunnel side, or between the outer edges of the water inlets of both purification water trenches. The upper surface of the retaining wall is 3-5cm above the corresponding tunnel surface, forming the initial purified water tunnel surface.

[0012] (b) Preliminary Tunnel Ground Construction on the Reverse Slope: The ground on one side of the tunnel floor, 5-7m away from the construction support surface, is leveled to form a horizontal surface. This horizontal surface occupies 35-40% of the tunnel floor width and is 15-21m long. A purification trench is formed by excavating 1-1.2m downwards at this horizontal surface. A water collection and sedimentation well is excavated 3-4.5m below the bottom edge of the purification trench on the outer side, away from the construction support surface. The diameter of the water collection and sedimentation well occupies 85-90% of the top width of the purification trench. A water collection and sedimentation well is excavated 5-7m away from the construction support surface. The purification water trench is filled with a gravel filter layer of 0.5-2cm particles to a height of 2-4cm above the corresponding ground level of the tunnel. 5-7m behind the gravel filter layer, the drainage purification water trench is filled with a coarse sand filter layer of 0.3-0.7cm particles to a height parallel to the corresponding ground level of the tunnel. 5-7m behind the coarse sand filter layer, the drainage purification water trench is filled with a fine sand filter layer of 0.1-0.3cm particles to a height parallel to the corresponding ground level of the tunnel. A 2-4cm thick gravel filter layer covers the upper surface of the coarse and fine sand filter layers, forming the initial purification water tunnel floor.

[0013] (2) Setting up multi-level sedimentation tanks in the main tunnel: Set up 3 to 5 levels of sedimentation tanks on the same side of the main tunnel near the bottom of the inclined shaft and the ground outlet of the purified water tunnel. The water that has been initially purified by the ground of the preliminary purified water tunnel is introduced into the 3 to 5 levels of sedimentation tanks for sedimentation and purification through the water diversion ditch.

[0014] (3) The construction of water storage tanks and pumping stations:

[0015] (a) A water collection tank with a volume of 40m³ is set up every 260m in the inclined shaft that connects the ground to the main line of the tunnel. The water collection tank is located in the vehicle shelter in one side wall of the inclined shaft. Each water collection tank is equipped with 3 15KW sewage treatment pumps or 2 160KW high-pressure horizontal centrifugal pumps to send the sedimented water in the water storage tank to the upper water storage tank. The sewage filtered by the sedimentation tank in the tunnel is pumped out to the sedimentation tank on the ground outside the tunnel using a staged pump.

[0016] (b) A pumping station shall be installed at the widened position of the left line of the tunnel on the reverse slope near the inclined shaft opening, in order to pump the sedimentation water in the sedimentation well into the main sedimentation chamber.

[0017] (c) A main line fixed pump station and a main water collection tank shall be set up at the tunnel widening position near the inclined shaft on the left line of the tunnel along the slope. The main water collection tank shall be used to store the sedimentation water in the sedimentation tanks of the left and right lines along the slope and the sedimentation wells of the water collection tanks against the slope. Two 630KW high-pressure horizontal centrifugal pumps shall be set up in the main line fixed pump station to send the sedimentation water in the main water collection tank to the adjacent upper water collection tank.

[0018] (4) As the tunnel construction support face advances, the filter material and adsorbed mud and sand in the original preliminary purified water surface, or the water collection sedimentation well filled with sediment can naturally form the tunnel surface foundation. After the new preliminary purified water surface is re-established 5 to 10 meters away from the new construction support face, a water diversion ditch is set on the original preliminary purified water surface. The water diversion ditch connects the water outlet of the newly established preliminary purified water surface with the inlet of the sedimentation pool in the tunnel. The new preliminary purified water surface can continue to be formed on the new construction support face until the tunnel project is completed.

[0019] (5) The sedimentation tank outside the tunnel further purifies the tunnel sewage: the sedimented water after being initially purified inside the tunnel main line, filtered by the tunnel surface, the sedimentation tanks of level 3 to 5 inside the tunnel and the water collection sedimentation well, is pumped to the sedimentation tank outside the tunnel by the fixed pumping station of the main line and the level 5 pump in the inclined shaft, and then further purifies the tunnel sewage.

[0020] (6) Reuse of purified water: The water purified by the sedimentation tank on the ground outside the tunnel is stored in a water storage tank. The water storage tank is connected to the automatic spray dust removal system in the factory area or tunnel to provide water for the spray dust removal system, or to the automatic car wash platform in the factory area. The treated water is used to clean vehicles entering and leaving the factory area, or to use water trucks and fog cannons to carry out cooling and dust removal operations on the sidewalks outside the factory area and inside the tunnel.

[0021] As a preferred embodiment of the present invention, the ratio of gravel with a particle size of 0.5 to less than 0.7 cm to gravel with a particle size of 0.7 to less than 1 cm to gravel with a particle size of 1 to 2 cm in the gravel filter layer is 20:30:70.

[0022] As a preferred embodiment of the present invention, the ratio of sand particles with a diameter of 0.3 to less than 0.5 cm to sand particles with a diameter of 0.5 to 0.7 cm in the coarse sand filter layer is 40:60.

[0023] As a preferred embodiment of the present invention, the ratio of sand particles with a diameter less than 0.2 cm to sand particles with a diameter of 0.2 to 0.3 cm in the fine sand filter layer is 30:70.

[0024] As a preferred embodiment of the present invention, the upper end of the water diversion ditch is provided with a perforated cement cover plate, the inlet end of the water diversion ditch is connected to the surface water outlet of the preliminary purified water, and the outlet end of the water diversion ditch is connected to the inlet of the sedimentation tank inside the cave.

[0025] As a preferred embodiment of the present invention, the upper end of the water collection sedimentation well is sealed with a load-bearing steel plate.

[0026] As a preferred embodiment of the present invention, the external ground sedimentation tank is located on the ground next to the inclined wellhead. The external ground sedimentation tank consists of a primary sedimentation tank, a secondary sedimentation tank, a tertiary sedimentation tank, and a horizontal flow dissolved air flotation (DAF) machine. Each sedimentation tank is constructed of reinforced concrete or welded steel plates. The bottom surface of each sedimentation tank is provided with a 30-50cm thick sand filter layer. The outlet of the sewage treatment pump at the top of the inclined well is connected to the upper end of the primary sedimentation tank. The filter outlet at the lower end of the primary sedimentation tank is connected to the inlet at the upper end of the secondary sedimentation tank via a pump. The filter outlet at the lower end of the secondary sedimentation tank is connected to the inlet at the upper end of the tertiary sedimentation tank via a pump. The filter outlet at the lower end of the tertiary sedimentation tank is connected to the inlet of the horizontal flow DAF machine via a pump. The purified water outlet of the horizontal flow DAF machine is connected to a water storage tank via a pump.

[0027] As a preferred embodiment of the present invention, the sand particles in the sand filter layer at the lower end of the primary sedimentation tank have a diameter of 3-5 mm.

[0028] As a preferred embodiment of the present invention, the sand particle size in the sand filter layer at the lower end of the secondary sedimentation tank is 50% 3-5mm, and the remainder is sand particles with a particle size of less than 3mm. The sand particle size in the sand filter layer at the lower end of the tertiary sedimentation tank is sand particles with a particle size of less than 1.5mm.

[0029] As a preferred technical solution of the present invention, the primary sedimentation tank, secondary sedimentation tank and tertiary sedimentation tank in the sedimentation tank outside the cave can be distributed in a stepped manner according to the terrain.

[0030] The beneficial effects of this invention compared to the prior art are as follows:

[0031] (1) This invention establishes a preliminary purified water surface 5-10m away from the construction support surface. The gravel filter layer, coarse sand filter layer, and fine sand filter layer within the preliminary purified water surface directly and non-poweredly purify the tunnel wastewater generated at the construction support surface. This ensures that a large amount of mud and sand in the tunnel wastewater remains on the ground outside the construction support surface. As the construction support surface advances, the filter material and adsorbed mud and sand within the original preliminary purified water surface, or the sedimentation wells filled with sediment, naturally form the foundation of the tunnel surface. After establishing a new preliminary purified water surface 5-10m away from the new construction support surface, a water diversion ditch is constructed on the original preliminary purified water surface. This ditch connects the outlet of the new preliminary purified water surface to the inlet of the sedimentation tank inside the tunnel, allowing for the continued formation of a new preliminary purified water surface on the new construction support surface until the tunnel project is completed. This invention enables the preliminary purification of tunnel wastewater generated at the construction support surface without power, and avoids the need for extensive manpower and resources to excavate and remove the adsorbed mud and sand within the preliminary purified water surface.

[0032] (2) The present invention has a good sedimentation and filtration effect. The present invention sets up a preliminary purification water surface. It has been measured that the preliminary purification water surface can filter 80-85% of the mud and sand in the sewage. Then the sewage is further purified by sedimentation in the cave sedimentation tank, water collection sedimentation well and each water collection chamber, so that the sand content of the sewage is reduced to 5-8%. Finally, it is filtered by the sedimentation tank on the ground outside the cave and purified by the horizontal flow dissolved air flotation machine. The purified water fully meets the Class II standard of the National Surface Water Environmental Quality Standard and can meet the requirements for reuse.

[0033] (3) This invention is applicable to the treatment and drainage of deep and long tunnels from inclined shafts, and can solve the problem of groundwater discharge in deep tunnels. This invention has a simple structure, low investment, convenient operation and maintenance, small space occupation, does not affect the transportation of tunnel excavated soil, and has significant water-saving effect and low treatment cost. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the wastewater sedimentation and filtration system of the present invention;

[0035] Figure 2 This is a schematic cross-sectional view of the main tunnel line on the left side near the inclined shaft of the present invention.

[0036] Figure 3 yes Figure 1 Schematic diagram of the cross-sectional structure of the middle AA section;

[0037] Figure 4 yes Figure 1 Schematic diagram of the cross-sectional structure of the middle BB section;

[0038] Figure 5 This is a schematic diagram of the sedimentation tank on the ground outside the cave according to the present invention. Detailed Implementation

[0039] To make the technical means, creative features, and achieved objectives and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. However, the following embodiments are only preferred embodiments of this invention and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0040] Example 1: Location: The Dabashan Tunnel, a key control project on the G69 National Expressway (Ankang to Langao, Shaanxi-Chongqing border), has a main left line length of 13.593km and a right line length of 13.561km. Section AL-C20 is responsible for constructing the middle section (the latter half within Shaanxi Province) of the Dabashan Tunnel, with a maximum burial depth of approximately 1112m. The designed maximum water inflow in the middle section is 25,600 m³ / d, while the actual inflow reaches 56,200 m³ / d. Construction enters the main tunnel through Construction Shaft No. 2 (1582m long, with a combined longitudinal slope of -9.6%), which handles drainage, ventilation, and transportation for the main tunnel construction. Due to the steep longitudinal slope of the shaft, the large water inflow, and stringent local environmental protection requirements, the method of this invention was adopted for construction drainage and sewage treatment. This effectively solved the difficulties in construction drainage and sewage treatment during the construction of the water-rich tunnel, improved the tunnel construction progress, and enhanced environmental protection during tunnel construction.

[0041] like Figures 1 to 5 As shown, a method for purifying water in deep, water-rich tunnels using a construction inclined shaft includes the following steps:

[0042] (1) The construction of the main tunnel is divided into the construction of the left main tunnel 10 and the right main tunnel 11. The left and right main tunnels are connected by the connecting passage 8. The construction inclined shaft 15 (1582m long, with a comprehensive longitudinal slope of -9.6%) enters the left main tunnel 10. The tunnel surface that is gradually higher than or equal to the ground of the connecting passage 8 is the downslope surface, such as the tunnel surface of the left support surface 12 and the right support surface 13, which are downslope surface, and the sewage flows downslope to the connecting passage. The tunnel surface that is gradually lower than the ground of the connecting passage is the upslope surface, such as the tunnel surface of the support surface 14 in the left main tunnel, which is upslope surface, and the sewage flows to the support surface 14.

[0043] The preliminary water purification tunnel surface construction at the support surface includes both downslope and upslope preliminary water purification tunnel surface construction:

[0044] like Figures 1 to 3 As shown, (a) Preliminary purification water tunnel surface construction along the slope: A preliminary purification water surface is constructed 5-10m away from the left support face 12 and the right support face 13. For simplicity, only the left support face 12 is described in detail. The right support face 13 has the same structure as the left support face 12, so it will not be described again. A sloping trench is excavated downwards from the ground 1.8-2m away from the left side of the tunnel bottom to form a purification water trench 2 with an inverted trapezoidal cross-section. The depth of the purification water trench 2 is 1-1.5m lower than the corresponding ground surface of the tunnel, and the angle between the sloping surface and the corresponding ground surface of the tunnel is 30°. 0 ~50 0The length of the purification water trench 2 is 15-21m. In the purification water trench 5-7m from the construction support surface, a crushed stone filter layer 201 with particles of 0.5-2cm is filled to be 2-4cm higher than the corresponding ground surface of the tunnel. In the drainage purification water trench 5-7m behind the crushed stone filter layer 201, a coarse sand filter layer with particles of 0.3-0.7cm is filled to be parallel to the corresponding ground surface of the tunnel. In the drainage purification water trench 5-7m behind the coarse sand filter layer, a fine sand filter layer 202 with particles of 0.1-0.3cm is filled to be parallel to the corresponding ground surface of the tunnel.

[0045] The ratio of gravel with a particle size of 0.5 to less than 0.7 cm to gravel with a particle size of 0.7 to less than 1 cm to gravel with a particle size of 1 to 2 cm in the gravel filter layer is 20:30:70.

[0046] The ratio of sand particles with a diameter of 0.3 to less than 0.5 cm to sand particles with a diameter of 0.5 to 0.7 cm in the coarse sand filter layer is 40:60.

[0047] The ratio of sand particles smaller than 0.2 cm to sand particles between 0.2 and 0.3 cm in the fine sand filter layer is 30:70.

[0048] A 2-4cm thick gravel filter layer 201 is laid on the upper surface of the coarse and fine sand filter layer. A water retaining wall 3 is provided between the outer side of the water inlet of the purification water ditch and the corresponding side of the tunnel, or between the outer sides of the water inlets of the two purification water ditches. The upper surface of the water retaining wall 3 is 3-5cm higher than the corresponding ground surface of the tunnel, forming the ground surface of the preliminary purification water tunnel.

[0049] When in use, the sewage generated from the left and right support surfaces enters the gravel filter layer 201 in the ground of the preliminary purification water tunnel along the water retaining wall 3, filtering out most of the mud and sand. Then it enters the coarse sand filter layer and the fine sand filter layer 202 in sequence. The preliminary purification water tunnel ground can filter and retain 80-85% of the mud and sand in the sewage.

[0050] like Figure 2 , 4As shown, (b) the left and right reverse slope tunnels 6 are located to the left of the connecting passage 8. The preliminary purification water tunnel surface construction on the reverse slope is as follows: the reverse slope ground 141 on one side of the tunnel bottom edge, about 5 to 7 m away from the reverse slope construction support surface 14, is leveled to form a horizontal ground. The horizontal ground occupies 35 to 40% of the tunnel ground width and is 15 to 21 m long. The purification water trench 2 is formed by digging 1 to 1.2 m down at the horizontal ground. A water collection and sedimentation well 17 is dug on the outer side of the purification water trench, away from the construction support surface, 3 to 4.5 m lower than the bottom edge of the purification water trench. The diameter of the water collection and sedimentation well 17 occupies 85 to 90% of the top width of the purification water trench. The upper end of the water collection and sedimentation well is sealed with a load-bearing steel plate so as not to affect the support surface construction. A 0.5-2cm gravel filter layer is filled into the purification water trench 5-7m from the construction support surface, up to 2-4cm above the corresponding tunnel ground level. A 0.3-0.7cm coarse sand filter layer is filled into the drainage purification water trench 5-7m behind the gravel filter layer, up to parallel with the corresponding tunnel ground level. A 0.1-0.3cm fine sand filter layer is filled into the drainage purification water trench 5-7m behind the coarse sand filter layer, up to parallel with the corresponding tunnel ground level. A 2-4cm thick gravel filter layer is then laid on top of the coarse and fine sand filter layers, forming the initial purification water tunnel ground.

[0051] When in use, the wastewater generated from the reverse slope towards the construction support surface 14 first enters the gravel filter layer 201 in the preliminary purification water tunnel floor, filtering out most of the mud and sand. Then it enters the coarse sand filter layer and the fine sand filter layer 202 in sequence. The preliminary purification water tunnel floor can filter and retain 80-85% of the mud and sand in the wastewater. Then it is filtered into the water collection sedimentation well 17 for further sedimentation and purification.

[0052] (2) Setting up of multi-stage sedimentation tanks in the main tunnel: Three to five stages of sedimentation tank 1 will be set up on the same side of the main tunnel as the ground outlet of the purified water tunnel, near the lower end of inclined shaft 15. Water that has undergone preliminary purification at the ground of the pre-purified water tunnel will be introduced into the three to five stages of sedimentation tank 1 through a drainage ditch for sedimentation and purification. The scale of the three to five stages of sedimentation tanks in the tunnel should be determined according to the tunnel's water inflow, and the location of the sedimentation tanks should be comprehensively selected to reduce drainage resistance.

[0053] For example, a five-stage sedimentation tank 1 is installed at the widened section of the left tunnel of the Dabashan Tunnel. The outer wall of the sedimentation tank is constructed at 3m intervals from the corresponding tunnel wall. Waterproof membrane is laid on the outer wall, sides, bottom, and corresponding tunnel wall on the same side of the sedimentation tank. The area of ​​the sedimentation tank is: length * width * height = 50 * 3 * 3.5 = 525 m³. The inlet of the five-stage sedimentation tank 1 is connected to the end edge of the tunnel surface for preliminary water purification via a drainage ditch. Four walls are installed in the middle of the five-stage sedimentation tank, with a gate 16 in the middle of each wall. A DN300 overflow pipe is installed on one side of each wall at a distance of 30cm from the top. The overflow pipes of adjacent walls are staggered to form the five-stage sedimentation tank, simultaneously achieving water collection. When the water inflow in the tunnel exceeds 1200 m³ / h, the gates on the adjacent walls of the inlet are opened, forming a three-stage sedimentation tank, meeting the requirements for 5 minutes of water storage and preliminary re-sedimentation.

[0054] (3) The construction of water storage tanks and pumping stations:

[0055] (a) A water collection tank with a volume of 40m³ is set up every 260m in the inclined shaft 15 that connects the ground to the main line of the tunnel. The water collection tank is located in the passing tunnel 4 inside one side wall of the inclined shaft. The water collection tank is used for water storage and sedimentation and purification of sewage. Each water collection tank is equipped with 3 15KW sewage treatment pumps or 2 160KW high-pressure horizontal centrifugal pumps to send the sedimented water in the water collection tank to the upper water collection tank. The sewage filtered by the sedimentation tank in the tunnel is pumped out to the sedimentation tank 7 on the ground outside the tunnel using a staged pump.

[0056] (b) A pumping station 9 shall be installed at the widened position of the left line of the tunnel on the reverse slope near the inclined shaft opening, for pumping the sedimentation water in the sedimentation well 17 into the main water collection chamber 5.

[0057] (c) A main line fixed pump station and a main water collection tank 5 shall be set up at the tunnel widening position near the inclined shaft on the left line of the tunnel along the slope. The main water collection tank 5 shall be used to store the sedimentation water in the sedimentation tanks of the left and right lines along the slope and the sedimentation wells of the water collection tanks against the slope. Two 630KW high-pressure horizontal centrifugal pumps shall be set up in the main line fixed pump station to send the sedimentation water in the main water collection tank to the adjacent upper-level water collection tank.

[0058] (4) As the tunnel construction support face advances, the filter material and adsorbed mud and sand in the original preliminary purified water surface, and the water collection sedimentation well filled with sediment naturally form the foundation of the tunnel surface. After the new preliminary purified water surface is re-established 5 to 10 meters away from the new construction support face, a water diversion ditch is set on the original preliminary purified water surface. The water diversion ditch connects the water outlet of the newly established preliminary purified water surface with the inlet of the sedimentation pool in the tunnel. The new preliminary purified water surface can continue to be formed on the new construction support face until the tunnel project is completed.

[0059] The upper end of the water diversion ditch is covered with a perforated cement cover to avoid affecting the construction of the support surface and to introduce wastewater from the corresponding ground surface into the water diversion ditch. The inlet end of the water diversion ditch is connected to the surface outlet of the preliminary purified water, and the outlet end of the water diversion ditch is connected to the inlet of the sedimentation tank inside the tunnel.

[0060] (5) The sedimentation tank outside the tunnel 7 further purifies the tunnel sewage: the sedimented water after the initial purification of the water inside the main tunnel, the sedimentation tanks of level 3 to 5 inside the tunnel and the water collection sedimentation well is pumped to the sedimentation tank outside the tunnel by the fixed pumping station of the main line and the level 5 pump in the inclined shaft, and then the tunnel sewage is further purified by sedimentation and filtration.

[0061] The sedimentation tank outside the tunnel is located on the ground next to the inclined shaft opening. The sedimentation tank consists of a primary sedimentation tank 71, a secondary sedimentation tank 72, a tertiary sedimentation tank 73, and a horizontal flow dissolved air flotation unit 21. Each sedimentation tank is constructed of reinforced concrete or welded steel plates. The bottom surface of each sedimentation tank is equipped with a sand filter layer with a thickness of 30-50cm. The sand filter layer at the bottom of the primary sedimentation tank has a sand particle size of 3-5mm. The sand filter layer at the bottom of the secondary sedimentation tank has 50% sand particles with a diameter of 3-5mm, and the remainder are sand particles with a diameter of less than 3mm. The sand filter layer at the bottom of the tertiary sedimentation tank has sand particles with a diameter of less than 1.5mm. The outlet of the sewage treatment pump located at the top of the inclined shaft is connected to the upper end of the primary sedimentation tank 71. The filter outlet located at the lower end of the primary sedimentation tank is connected to the inlet at the upper end of the secondary sedimentation tank via pump 20. The filter outlet located at the lower end of the secondary sedimentation tank is connected to the inlet at the upper end of the tertiary sedimentation tank via pump 20. The filter outlet located at the lower end of the tertiary sedimentation tank is connected to the inlet of the horizontal flow dissolved air flotation machine 21 via pump 21. The purified water outlet of the horizontal flow dissolved air flotation machine is connected to the water storage tank via pump 21. The horizontal flow dissolved air flotation machine is a commercially available product.

[0062] The sediment in each sedimentation tank and water collection tank can be removed regularly along with the slag and soil.

[0063] (6) Reuse of purified water: The water purified by the sedimentation tank on the ground outside the tunnel is stored in a water storage tank. The water storage tank is connected to the automatic spray dust removal system in the factory area or tunnel to provide water for the spray dust removal system, or to the automatic car wash platform in the factory area. The treated water is used to clean vehicles entering and leaving the factory area, or to use water trucks and fog cannons to carry out cooling and dust removal operations on the sidewalks outside the factory area and inside the tunnel.

[0064] During use, the wastewater generated by the construction support surface first passes through the preliminary purification water surface. The gravel filter layer, coarse sand filter layer, and fine sand filter layer in the preliminary purification water surface directly and non-poweredly purify the tunnel wastewater generated by the construction support surface. This causes a large amount of mud and sand in the tunnel wastewater to be retained in the ground outside the construction support surface. As the construction support surface moves forward, the filter material and adsorbed mud and sand in the original preliminary purification water surface, or the water collection and sedimentation well filled with sediment, can naturally form the foundation of the tunnel ground. After the new preliminary purification water surface is set up 5 to 10 meters away from the new construction support surface, a water diversion ditch is set up on the original preliminary purification water surface. The water diversion ditch connects the outlet of the new preliminary purification water surface to the inlet of the sedimentation tank in the tunnel, and a new preliminary purification water surface can continue to be formed on the new construction support surface. The water, after initial surface filtration and purification, enters the sedimentation tank or collection well inside the tunnel for a second sedimentation purification. After a third sedimentation purification in the main collection tank or inclined well collection tank of each pumping station, it enters the multi-stage sedimentation tank outside the tunnel for a fourth sedimentation purification. Finally, it undergoes a fourth purification by a horizontal flow dissolved air flotation machine, thus meeting the national standard for Class II water quality for pollution discharge.

[0065] Compared with the prior art, the beneficial effects of the present invention are:

[0066] Table 1: Comparison of Average Wastewater Discharge and Purification Costs Per Meter of Tunnel Excavation

[0067]

[0068] Table 1 illustrates that the method of this invention reduces material usage by 9.09% and overall cost by 66.67% compared to traditional methods, demonstrating advantages in materials and low cost, thus improving economic efficiency. The national standard for pollution discharge treated by this invention is Class II water quality, which is two levels higher than the national standard for pollution discharge treated by traditional methods, resulting in excellent pollution control effects.

[0069] Example 2: Unlike Example 1, as follows Figure 5 As shown, the primary sedimentation tank 71, secondary sedimentation tank 72, and tertiary sedimentation tank 73 in the sedimentation pool outside the cave can be distributed in a stepped manner according to the terrain 18, thus eliminating the need for water pumps between each sedimentation tank. Water pumps can be replaced by water guide pipes 19. Specifically, the filtration outlet at the lower end of the primary sedimentation tank is connected to the inlet at the upper end of the secondary sedimentation tank via water guide pipe 19, and the filtration outlet at the lower end of the secondary sedimentation tank is connected to the inlet at the upper end of the tertiary sedimentation tank via water guide pipe. The rest is the same as in Example 1, and therefore will not be repeated.

[0070] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for dewatering a deep water-rich tunnel by means of a construction ramp, characterized in that, Includes the following steps: (1) Preliminary water purification tunnel surface construction on the support surface, including preliminary water purification tunnel surface construction along the slope and preliminary water purification tunnel surface construction against the slope: (a) Construction of the preliminary water purification tunnel surface along the slope: A preliminary water purification surface is set up 5-10m away from the construction support surface. A sloping trench is excavated downwards from the ground 1.8-2m away from the bottom side of the tunnel, forming a water purification trench with an inverted trapezoidal cross-section. The depth of the water purification trench is 1-1.5m lower than the corresponding ground surface of the tunnel, and the angle between the sloping surface and the corresponding ground surface of the tunnel is 30°-50°. The length of the purification water trench is 15-21m. A 0.5-2cm gravel filter layer is filled in the 5-7m section closest to the construction support surface, extending 2-4cm above the corresponding tunnel surface. A 0.3-0.7cm coarse sand filter layer is filled in the 5-7m section behind the gravel filter layer, parallel to the corresponding tunnel surface. A 0.1-0.3cm fine sand filter layer is filled in the 5-7m section behind the coarse sand filter layer, parallel to the corresponding tunnel surface. A 2-4cm thick gravel filter layer covers the upper surfaces of the coarse and fine sand filter layers. A retaining wall is installed between the outer edge of the water inlet of the purification water trench and the corresponding tunnel side, or between the outer edges of the water inlets of both purification water trenches. The upper surface of the retaining wall is 3-5cm above the corresponding tunnel surface, forming the initial purified water tunnel surface. (b) Preliminary Tunnel Ground Construction on the Reverse Slope: The ground on one side of the tunnel floor, 5-7m away from the construction support surface, is leveled to form a horizontal surface. This horizontal surface occupies 35-40% of the tunnel floor width and is 15-21m long. A purification trench is formed by excavating 1-1.2m downwards at this horizontal surface. A water collection and sedimentation well is excavated 3-4.5m below the bottom edge of the purification trench on the outer side, away from the construction support surface. The diameter of the water collection and sedimentation well occupies 85-90% of the top width of the purification trench. A water collection and sedimentation well is excavated 5-7m away from the construction support surface. The purification water trench is filled with a gravel filter layer of 0.5-2cm particles to a height of 2-4cm above the corresponding ground level of the tunnel. 5-7m behind the gravel filter layer, the drainage purification water trench is filled with a coarse sand filter layer of 0.3-0.7cm particles to a height parallel to the corresponding ground level of the tunnel. 5-7m behind the coarse sand filter layer, the drainage purification water trench is filled with a fine sand filter layer of 0.1-0.3cm particles to a height parallel to the corresponding ground level of the tunnel. A 2-4cm thick gravel filter layer covers the upper surface of the coarse and fine sand filter layers, forming the initial purification water tunnel floor. (2) Setting up multi-level sedimentation tanks in the main tunnel: Set up 3 to 5 levels of sedimentation tanks on the same side of the main tunnel near the bottom of the inclined shaft and the ground outlet of the purified water tunnel. The water that has been initially purified by the ground of the preliminary purified water tunnel is introduced into the 3 to 5 levels of sedimentation tanks for sedimentation and purification through the water diversion ditch. (3) The setting of water storage tanks and pumping stations: (a) A water collection tank with a volume of 40m³ is set up every 260m in the inclined shaft connecting the ground to the main line of the tunnel. The water collection tank is located in the vehicle-passing hole in one side wall of the inclined shaft. Each water collection tank is equipped with 3 15KW sewage treatment pumps or 2 160KW high-pressure horizontal centrifugal pumps to send the sedimented water in the water storage tank to the upper water storage tank. The sewage filtered by the sedimentation tank in the tunnel is pumped out to the sedimentation tank on the ground outside the tunnel using a staged pump. (b) A pumping station shall be installed at the widened position of the left line of the tunnel on the reverse slope near the inclined shaft opening, in order to pump the sedimentation water in the sedimentation well into the main sedimentation chamber. (c) A main line fixed pump station and a main water collection tank shall be set up at the tunnel widening position near the inclined shaft on the left line of the tunnel along the slope. The main water collection tank shall be used to store the sedimentation water in the sedimentation tanks of the left and right lines along the slope and the sedimentation wells of the water collection tanks against the slope. Two 630KW high-pressure horizontal centrifugal pumps shall be set up in the main line fixed pump station to send the sedimentation water in the main water collection tank to the adjacent upper water collection tank. (4) As the tunnel construction support face advances, the filter material and adsorbed mud and sand in the original preliminary purified water surface, and the water collection sedimentation well filled with sediment naturally form the tunnel surface foundation. After the new preliminary purified water surface is re-established 5 to 10 meters away from the new construction support face, a water diversion ditch is set on the original preliminary purified water surface. The water diversion ditch connects the water outlet of the newly established preliminary purified water surface with the inlet of the sedimentation pool in the tunnel. The new preliminary purified water surface can continue to be formed on the new construction support face until the tunnel project is completed. (5) The sedimentation tank outside the tunnel further purifies the tunnel sewage: the sedimented water after being initially purified inside the tunnel main line, filtered by the tunnel surface, the sedimentation tanks of level 3 to 5 inside the tunnel and the water collection sedimentation well, is pumped to the sedimentation tank outside the tunnel by the fixed pumping station of the main line and the level 5 pump in the inclined shaft, and then further purifies the tunnel sewage. (6) Reuse of purified water: The water purified by the sedimentation tank on the ground outside the tunnel is stored in a water storage tank. The water storage tank is connected to the automatic spray dust removal system in the factory area or tunnel to provide water for the spray dust removal system, or to the automatic car wash platform in the factory area. The treated water is used to clean vehicles entering and leaving the factory area, or to use water trucks and fog cannons to carry out cooling and dust removal operations on the sidewalks outside the factory area and inside the tunnel.

2. The method of claim 1, wherein: The ratio of gravel with a particle size of 0.5 to less than 0.7 cm to gravel with a particle size of 0.7 to less than 1 cm to gravel with a particle size of 1 to 2 cm in the gravel filter layer is 20:30:

70.

3. The method according to claim 1, characterized in that: The ratio of sand particles with a diameter of 0.3 to less than 0.5 cm to sand particles with a diameter of 0.5 to 0.7 cm in the coarse sand filter layer is 40:

60.

4. The method according to claim 1, characterized in that: The ratio of sand particles with a diameter less than 0.2 cm to sand particles with a diameter of 0.2 to 0.3 cm in the fine sand filter layer is 30:

70.

5. The method according to claim 1, characterized in that: The upper end of the water diversion ditch is covered with a perforated cement cover plate. The inlet end of the water diversion ditch is connected to the surface water outlet of the preliminary purified water, and the outlet end of the water diversion ditch is connected to the inlet of the sedimentation tank inside the cave.

6. The method according to claim 1, characterized in that: The upper end of the water collection sedimentation well is sealed with a load-bearing steel plate.

7. The method according to claim 1, characterized in that: The aforementioned outdoor sedimentation tank is located on the ground next to the inclined shaft opening. It consists of a primary sedimentation tank, a secondary sedimentation tank, a tertiary sedimentation tank, and a horizontal-flow dissolved air flotation (DAF) machine. Each sedimentation tank is constructed of reinforced concrete or welded steel plates. The bottom surface of each sedimentation tank has a 30-50cm thick sand filter layer. The outlet of the wastewater treatment pump at the top of the inclined shaft is connected to the upper end of the primary sedimentation tank. The filter outlet at the lower end of the primary sedimentation tank is connected to the inlet at the upper end of the secondary sedimentation tank via a pump. The filter outlet at the lower end of the secondary sedimentation tank is connected to the inlet at the upper end of the tertiary sedimentation tank via a pump. The filter outlet at the lower end of the tertiary sedimentation tank is connected to the inlet of the horizontal-flow DAF machine via a pump. The purified water outlet of the horizontal-flow DAF machine is connected to the water storage tank via a pump.

8. The method according to claim 7, characterized in that: The sand particles in the sand filter layer at the lower end of the primary sedimentation tank have a diameter of 3-5 mm.

9. The method according to claim 7, characterized in that: The sand filter layer at the lower end of the secondary sedimentation tank contains 50% sand particles with a diameter of 3-5 mm, and the remainder consists of sand particles with a diameter of less than 3 mm. The sand filter layer at the lower end of the tertiary sedimentation tank contains sand particles with a diameter of less than 1.5 mm.

10. The method according to claim 7, characterized in that: The primary, secondary, and tertiary sedimentation tanks in the sedimentation ponds outside the cave can be distributed in a stepped manner according to the terrain.

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