Water-rich mountain tunnel excavation construction in combination of permanent and temporary sewage discharge and construction method

Abstract

The application provides a sewage discharge and precipitation structure and construction method for permanent and temporary combination in water-rich mountainous tunnel excavation construction, which comprises a temporary left side ditch, a temporary right side ditch, a gabion reverse filtration facility arranged in the temporary left side ditch and the temporary right side ditch, a clean water direct discharge and precipitation pool arranged outside the tunnel, a clean water guide and discharge ditch, a clean water direct discharge and precipitation ditch and a waste water guide and discharge ditch, a temporary partition wall arranged in a water passing culvert, a temporary cofferdam arranged in the water passing culvert and located at a downstream position of the temporary partition wall, and an overflow port arranged close to an upper end position of the temporary partition wall. The application can not only avoid the cutting of the conventional tunnel waste water treatment on the operation site, but also can realize the low-cost, high-efficiency and safe treatment of the sewage in the water-rich tunnel excavation support under the condition of large water inflow and flow rate by means of the existing permanent engineering entity structure and temporary construction structure inside and outside the tunnel and by means of the diversion and purification of the sewage source of the tunnel.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of tunnel construction environmental protection technology, and particularly relates to a sewage discharge and precipitation structure for permanent and temporary combined use in water-rich mountainous tunnel excavation construction and a construction method. BACKGROUND

[0002] The environmental protection and water and soil conservation of water-rich mountainous tunnels are common problems in the field of highway engineering construction. Research results show that the main pollutants in highway tunnel construction wastewater are oil, solid suspended particles in water, and the pH is alkaline. According to the requirements of the national "Integrated Wastewater Discharge Standard (GB 8978-1996)", the main problem of tunnel construction wastewater is that the suspended solids are over-standard. The alkaline pH is mainly due to the alkaline nature of tricalcium silicate, dicalcium silicate, calcium hydroxide and other substances produced by the hydrolysis of cement products such as concrete. These substances dissolved in water cause the pH to rise, but most of them are within the allowable discharge index. Oil is generally disposed of by setting up an oil separation tank. The solid suspended particles in water are generally discharged after natural precipitation by setting up a sedimentation tank.

[0003] During the tunnel excavation construction of a water-rich tunnel, water gushing often occurs. If the water gushing from the mountain is not treated, and the production wastewater during the tunnel construction process is allowed to mix with it, the solid suspended matter concentration of the water flowing out of the tunnel will be too high. If the untreated wastewater is directly discharged into the external environment, especially when the construction site is close to water source protection areas and drinking water intake points, the environmental impact of direct wastewater discharge will be even worse. Because it will cause a large amount of solid sediments to deposit in the riverbed, which will cause many problems related to riverbed sediments. Long-term accumulation will have an immeasurable impact on the survival and reproduction of aquatic benthic organisms. At the same time, because the wastewater contains a large amount of inorganic matter, it will reduce the quality of organic matter in the surrounding water source, thereby affecting crop yields, especially rice yields. A large amount of construction wastewater discharged into nearby water areas will not only have an ecological impact on water quality, but also affect the landscape of the water body, thereby causing ecological damage.

[0004] Currently, common wastewater treatment methods in construction projects include chemical precipitation, mechanical treatment, and natural sedimentation. Chemical precipitation primarily involves adding flocculants to construction wastewater, followed by sedimentation and separation in sedimentation tanks. There are three main types of flocculants: inorganic, organic, and microbial. Inorganic flocculants offer advantages such as cost-effectiveness and ease of use, but they require high dosages, produce high residue levels, and are still more expensive than natural sedimentation. While organic polymer flocculants offer low dosages, low scum production, strong flocculation ability, easy floc separation, and excellent oil and suspended solids removal, residual monomers in these polymers can have teratogenic, carcinogenic, and mutagenic effects. Improper dosage control can result in ineffective sedimentation or even secondary pollution, limiting their application. While microbial flocculants offer no secondary pollution and are easy to use, they require high production costs, and current fermentation production processes leave much to be desired. Furthermore, the composition and flocculation effects of these flocculants lack a certain degree of stability, hindering their development. Generally speaking, the chemical sedimentation method requires a separate sewage storage system, which occupies a large area. Factors influencing the coagulation effect (chemical dosage) during the water treatment process are complex, including water temperature, pH and alkalinity, the nature and concentration of impurities in the water, and external hydraulic conditions. Therefore, regular chemical dosage tests are required before chemical addition, and chemical additives are often required. This is costly and difficult to manage, making it unsuitable for sewage treatment during tunnel excavation construction.

[0005] Mechanical treatment is to use mechanical dewatering measures to treat the sludge in the pool, such as purchasing a sludge dewatering machine, but it has the following disadvantages: (1) The one-time investment is large. A certain number of mechanical equipment must be purchased according to the water flow. The machinery needs to be placed in a confined space, so a special protective shed or small factory building needs to be built; and a certain size of water collection pool is required to store sewage for centralized treatment, otherwise the efficiency of the machinery cannot be fully utilized. (2) The site layout is difficult, which is not conducive to the utilization of land resources; (3) The tunnel is constantly flooded 24 hours a day, so the sludge dewatering machine needs to be kept in a state of being able to operate at any time. Therefore, it is necessary to consider the water treatment method and the corresponding mechanical operation management measures during the power outage; (4) The dewatering machine is noisy during operation, which does not meet the noise control requirements for areas near villages; (5) The water content of the sludge is still relatively high after dewatering, and it is difficult to separate when the solid-liquid density difference is very small; (6) If the sludge contains gravel, it is easy to wear the centrifugal liquid damage equipment, and the use process will continue to generate power costs, and the subsequent maintenance costs are also relatively high. Based on the above reasons, the application of mechanical treatment in sewage treatment during tunnel excavation construction is limited.

[0006] The principle of natural sedimentation is to allow wastewater to settle naturally in a tank without the use of chemicals or other measures. This method is widely used due to its low cost. After suspended solids are fully settled in the sedimentation tank, they can fully meet national comprehensive sewage discharge standards. In actual construction, a common practice is to install a separate tertiary sedimentation tank at the tunnel entrance. To ensure effective sedimentation, the sewage in the sedimentation tank must flow at a relatively slow rate, allowing sufficient time for suspended solid particles to settle. However, for tunnels with large water inflows, the sewage flow rate and flow rate are correspondingly high, requiring a larger sedimentation tank area and volume; otherwise, effective sedimentation will not be achieved. The installation of a large foundation pit or water tank within the tunnel entrance poses certain safety risks. The construction and use of a large sedimentation tank will hinder traffic and pedestrian access, hindering on-site construction. Furthermore, the excavation of a deep pit and its prolonged waterlogging can negatively impact the stability of the surrounding strata, particularly at the tunnel entrance. In summary, the volume and floor space of a sedimentation tank are positively correlated with sedimentation efficiency. Larger tanks improve sedimentation efficiency. However, larger tanks have significant negative impacts on layout, cost, safety risks, and ground stability. In actual construction, to avoid these negative issues, tertiary sedimentation tanks are typically very small, but this ineffectively achieves adequate sedimentation efficiency. Therefore, simply installing sedimentation tanks to allow natural sedimentation cannot solve the sewage treatment problem associated with tunnel construction. Summary of the Invention

[0007] In response to the above problems, the present invention provides a permanent and temporary sewage discharge sedimentation structure and construction method for the excavation and construction of water-rich mountain tunnels. The present invention uses the permanent engineering physical structures and temporary construction structures inside and outside the tunnel to divert and clean the tunnel's clean and dirty water sources. This not only avoids the disruption of the work site by conventional tunnel wastewater treatment, but also achieves low-cost, efficient and safe treatment of sewage in the excavation and construction of water-rich tunnels when the water flow rate and flow rate are large.

[0008] The present invention is achieved through the following technical solutions.

[0009] On the one hand, the present invention provides a permanent and temporary sewage discharge and sedimentation structure for use in the excavation and construction of a water-rich mountain tunnel, comprising a central ditch and a central ditch inspection well disposed within the tunnel, a lower pilot pit disposed near the tunnel face for collecting all sewage upstream of the tunnel, and a water culvert adjacent to the tunnel entrance, characterized in that it also includes:

[0010] The temporary left ditch and the temporary right ditch are respectively arranged at left and right sides of the tunnel hole, the gabion reverse filtration facility is arranged in the temporary left ditch and the temporary right ditch, the clean water direct discharge sedimentation tank, the clean water lead and discharge ditch, the clean water direct discharge ditch and the waste water lead and discharge ditch are arranged outside the tunnel, the temporary partition wall is arranged in the water passing culvert, the temporary cofferdam is arranged in the water passing culvert and located at a downstream position of the temporary partition wall, and the overflow port is arranged close to a top position of the temporary partition wall;

[0011] The temporary right ditch is connected with the drainage hole in the secondary lining of the tunnel, and is used for discharging clean water flowing out of the mountain above the secondary lining of the tunnel; the temporary left ditch is connected with the lower pit, and is used for discharging sewage collected in the lower pit; one end of the clean water lead and discharge ditch is connected with the drainage port of the temporary right ditch in the tunnel hole, and the other end is connected with the clean water direct discharge sedimentation tank; one end of the waste water lead and discharge ditch is connected with the drainage port of the temporary left ditch and the central water ditch in the tunnel hole, and the other end is connected with the water passing culvert upstream of the temporary partition wall; and the water outlet end of the clean water direct discharge sedimentation tank is connected with the water passing culvert downstream of the temporary cofferdam through the clean water direct discharge ditch;

[0012] In the above structure, the central water ditch, the central water ditch inspection well, the lower pit and the water passing culvert are permanent engineering entity structures which exist in the tunnel or are needed to be constructed by themselves; and the temporary left ditch, the temporary right ditch, the gabion reverse filtration facility, the clean water direct discharge sedimentation tank, the clean water lead and discharge ditch, the clean water direct discharge ditch and the waste water lead and discharge ditch, the temporary partition wall and the overflow port are temporary structures which are constructed temporarily, and can be removed or changed to other uses after the tunnel excavation construction is completed and a large amount of waste water is not generated.

[0013] As a specific technical solution, the gabion reverse filtration facility arranged in the temporary left ditch is arranged every 50 m to 100 m, and the gabion reverse filtration facility arranged in the temporary right ditch is arranged every 150 m to 200 m.

[0014] As a specific technical solution, the gabion reverse filtration facility comprises a plurality of layers of gabion baskets stacked in a trapezoidal shape, and sandbags are arranged close to the gabion baskets and located at a downstream position of the gabion baskets.

[0015] As a specific technical solution, the gabion reverse filtration facility is arranged adjacent to the central water ditch inspection well and located upstream of the central water ditch inspection well.

[0016] As a specific technical solution, the clean water lead and discharge ditch comprises a clean water horizontal underground ditch connected with the temporary right ditch in the left and right tunnel holes, and a clean water lead and discharge open ditch connected with the clean water horizontal underground ditch at one end and connected with the clean water direct discharge sedimentation tank at the other end; and the waste water lead and discharge ditch comprises a waste water horizontal underground ditch connected with the temporary left ditch and the central water ditch in the same tunnel, and a waste water lead and discharge open ditch connected with the waste water horizontal underground ditch at one end and connected with the water passing culvert upstream of the temporary partition wall at the other end.

[0017] As a specific technical scheme, a layer of reinforcing mesh is arranged in the overflow port, and the height of the overflow port from the bottom of the temporary partition wall is determined according to the maximum water inflow in the tunnel and the water storage capacity allowed by the carrying capacity of the water passing culvert.

[0018] As a specific technical scheme, the structure further comprises a water collecting pool arranged on the temporary right side ditch drainage route and located upstream of the gabion reverse filtration facility, and a water pump is arranged in the water collecting pool.

[0019] As a specific technical scheme, a sewage pump is arranged in the lower pit, and the outlet end of the sewage pump is connected to the temporary left side ditch through a sewage discharge pipe.

[0020] As a specific technical scheme, the structure further comprises a top drainage ditch arranged on the top of the tunnel portal, and the outlet end of the top drainage ditch is connected to the clean water drainage ditch.

[0021] As a specific technical scheme, the structure further comprises a waste water pool inlet underground drainage ditch and a drop platform; one end of the waste water pool inlet underground drainage ditch is connected to the waste water drainage open ditch, and the other end extends into the water passing culvert and is connected to the drop platform.

[0022] On the other hand, the application provides a construction method of a sewage discharge and sedimentation structure in a water-rich mountainous tunnel excavation construction, characterized by comprising the following steps:

[0023] S1, parameter design of the sewage discharge structure

[0024] According to the normal water inflow and the maximum water inflow in the peak period of the tunnel, and combining with the entity engineering drawing calculation and determination of the design parameters of the sewage discharge structure;

[0025] S2, construction of the in-tunnel drainage structure

[0026] The permanent side ditch and the cable ditch in the delayed construction tunnel form a temporary left side ditch and a temporary right side ditch by controlling the natural height difference between the road surface leveling layer and the two side inverted arch filling layers when the road surface leveling layer and the two side inverted arch filling layers are filled; then, the gabion reverse filtration facility is arranged in the temporary left side ditch and the temporary right side ditch; the temporary right side ditch is connected to the drainage hole in the secondary lining of the tunnel, and the temporary left side ditch is connected to the lower pit.

[0027] S3, construction of the out-tunnel drainage facility

[0028] The water purification guide and discharge ditch, the water purification direct discharge ditch, the water purification direct discharge sedimentation tank and the waste water guide and discharge ditch are constructed outside the tunnel hole; wherein, one end of the water purification guide and discharge ditch is connected with the drainage outlet of the temporary right side ditch in the tunnel hole, and the other end is connected with the water purification direct discharge sedimentation tank; one end of the waste water guide and discharge ditch is connected with the drainage outlets of the temporary left side ditch and the central water ditch in the tunnel hole, and the other end is connected with the water passing culvert upstream of the temporary cofferdam; the water outlet end of the water purification direct discharge sedimentation tank is connected with the water passing culvert downstream of the temporary cofferdam through the water purification direct discharge ditch;

[0029] S4, permanent and temporary combined construction of the sedimentation tank

[0030] The height of the overflow port and the temporary cofferdam is calculated and determined, so that the water storage capacity of the water passing culvert is greater than the maximum water inflow in the tunnel, then the backfill height of the backfill soil on the top of the water passing culvert is reduced, so that the self weight G1 of the reduced part of the backfill soil on the top of the water passing culvert is greater than the sum of the water storage gravity G2 under the water storage capacity of the water passing culvert, the self weight G3 of the temporary partition wall and the self weight G4 of the temporary cofferdam, then according to the construction sequence from downstream to upstream, a temporary cofferdam is first built at the water outlet position of the permanent water passing culvert across the tunnel, then a temporary partition wall is built at the middle position of the water passing culvert, and an overflow port is reserved at the upper end of the temporary partition wall, so that a first stage sedimentation tank is formed between the temporary partition wall and the upstream surface of the water passing culvert, and a second stage sedimentation tank is formed between the temporary cofferdam and the temporary partition wall.

[0031] S5, sewage discharge detection and acceptance

[0032] The sewage in the tunnel hole is discharged, and the clean water in the water passing culvert downstream of the temporary cofferdam is detected.

[0033] As a specific technical scheme, the temporary partition wall is brick-laid and does not undergo plastering treatment.

[0034] The present application has the following beneficial effects:

[0035] 1) In the water-rich mountainous tunnel excavation construction, because the construction site is very compact, the present application can reduce the cutting of the tunnel waste water treatment measures on the construction site by means of the permanent engineering entity structures such as the central water ditch, the central water ditch inspection well, the lower guide pit and the water passing culvert inside and outside the tunnel, and the temporary left side ditch, the temporary right side ditch, the gabion reverse filtration facility, the water purification direct discharge sedimentation tank, the water purification guide and discharge ditch, the water purification direct discharge ditch and the waste water guide and discharge ditch, the temporary partition wall and other temporary construction structures, so as to ensure that the construction conditions and site layout of the tunnel excavation construction site are not affected.

[0036] 2) The present invention sets up a temporary left ditch, a temporary right ditch and gabion stone cage filtration facilities in a water-rich tunnel with limited space, which not only realizes the diversion of clean water and sewage in the tunnel, but also can filter the water body; in addition, the present invention uses the adjacent water culvert outside the tunnel as a carrier, and forms a secondary wastewater sedimentation tank outside the tunnel by constructing a temporary structure. In this way, by diverting and filtering from the source in the tunnel, and then sedimenting and recycling outside the tunnel, the water outflow in the tunnel → water filtration in the tunnel → water outflow in the tunnel → sedimentation outside the tunnel → water use in the tunnel is realized, that is, the diversion and gradual purification of the water body from the inside to the outside of the tunnel are completed, thereby connecting the tunnel water body into a whole, so as to achieve the purpose of efficiently utilizing existing water resources, maximizing the cost savings of construction water, and improving work efficiency.

[0037] 3) By utilizing a nearby water culvert outside the tunnel instead of a new sewage sedimentation tank, the present invention can reduce the construction cost of a new sedimentation tank and eliminate the problem of traditional sedimentation tanks occupying a large area. It also solves the problem of being unable to treat sewage in the tunnel in a low-cost, efficient and safe manner due to the large flow rate and flow velocity of the gushing water during the excavation construction of a water-rich mountain tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of drainage and sedimentation in the hole of the sewage discharge and sedimentation structure of the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of drainage and sedimentation outside the cave in the sewage discharge and sedimentation system of the present invention;

[0040] Figure 3 It is a structural schematic diagram of the gabion stone cage filtration facility in the structure of the present invention;

[0041] Figure 4 Schematic diagram of the installation of gabion stone cage in the structure of the present invention;

[0042] Figure 5 This is a schematic diagram of the structure of the water culvert in the structure of the present invention;

[0043] Figure 6 for Figure 5 Cross-sectional view at AA in the middle;

[0044] Figure 7 Schematic diagram of the construction of a temporary right ditch and a temporary left ditch in the structure of the present invention;

[0045] The meanings of the symbols in the above figure are: temporary left ditch 1, temporary right ditch 2, central ditch 3, central ditch inspection well 4, water culvert 5, gabion stone cage filtration facility 6, gabion stone cage 601, sandbag 602, clean water direct discharge sedimentation tank 7, clean water diversion and drainage ditch 8, clean water horizontal culvert 801, clean water diversion and drainage open ditch 802, wastewater diversion and drainage ditch 9, wastewater horizontal culvert 901, wastewater diversion and drainage open ditch 902, clean water direct discharge ditch 10, temporary partition wall 11, overflow outlet 12, lower pilot pit 13, collection pool 14, sewage pump 15, drainage hole 16, tunnel roof drainage ditch 17, drop platform 18, wastewater inlet pool culvert 19, tunnel secondary lining 20, left tunnel 21, right tunnel 22, heading face 23, temporary cofferdam 24, road surface leveling layer 25, invert arch filling layer 26. DETAILED DESCRIPTION

[0046] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0047] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Example 1

[0048] For the permanent and temporary sewage discharge sedimentation structure during the excavation of the Fushui Mountain Tunnel, please refer to Figures 1 to 3 , including a central ditch 3 and a central ditch inspection well 4 set in the tunnel, a lower pilot pit 13 set near the tunnel face 23 for collecting all sewage from upstream in the tunnel, a water culvert 5 near the tunnel entrance, a temporary left ditch 1 and a temporary right ditch 2 set on the left and right sides of the tunnel respectively, a gabion stone cage filtration facility 6 set in the temporary left ditch 1 and the temporary right ditch 2, a clean water direct discharge sedimentation tank 7, a clean water diversion ditch 8, a clean water direct discharge ditch 10 and a wastewater diversion ditch 9 set outside the tunnel, a temporary partition wall 11 set in the water culvert 5, a temporary cofferdam 24 set in the water culvert 5 and located downstream of the temporary partition wall 11, and an overflow port 12 set near the top of the temporary partition wall 11;

[0049] The temporary right ditch 2 is connected to the drainage hole 16 in the secondary lining of the tunnel to discharge the clean water flowing out of the mountain above the secondary lining of the tunnel; the temporary left ditch 1 is connected to the lower pilot pit 13 to discharge the sewage collected in the lower pilot pit 13; one end of the clean water diversion ditch 8 is connected to the drainage outlet of the temporary right ditch 2 in the tunnel, and the other end is connected to the clean water direct discharge sedimentation tank 7; one end of the wastewater diversion ditch 9 is connected to the drainage outlet of the temporary left ditch 1 and the central ditch 3 in the tunnel, and the other end is connected to the water culvert 5 upstream of the temporary partition wall 11; the water outlet of the clean water direct discharge sedimentation tank 7 is connected to the water culvert 5 downstream of the temporary cofferdam 24 through the clean water direct discharge ditch 10;

[0050] Usually during the tunnel excavation construction process, the main sources of water in the cave are: 1. the gushing water generated by the face when the tunnel passes through the bad geological section; 2. the bedrock fissure water, which mainly flows out from the drainage holes of the secondary lining, and this type of water is usually relatively clear; 3. the wastewater generated during the construction of the drilling rig; 4. the wastewater used for dust reduction after the tunnel blasting; 5. the wastewater used to clean the rock surface before the tunnel is sprayed with concrete and the water from the mountain seepage; 6. the wastewater generated during the spraying of concrete and grouting; In the present invention, the main sources of sewage collected in the lower pilot pit are: the gushing water generated by the face when the tunnel passes through the bad geological section, the wastewater generated during the construction of the drilling rig, the wastewater used for dust reduction after the tunnel blasting, the wastewater generated during the spraying of concrete and grouting Wastewater; In the above structure of the present invention, the sewage collected in the lower pilot pit is discharged to the outside of the tunnel through the temporary left ditch 1, and the clean water flowing out of the mountain above the secondary lining of the tunnel is discharged to the outside of the tunnel through the temporary right ditch 2. In this way, the sewage is separated and discharged through the left and right side ditches, which can avoid the secondary pollution of the usable water body due to the intersection of water bodies; and the temporary left ditch and the temporary right ditch are provided with gabion stone cage filtration facilities 6, which can preliminarily filter the water bodies in the temporary left ditch 1 and the temporary right ditch 2, so that the water bodies do not contain large-grained sand and mud before flowing out of the tunnel; after the wastewater in the temporary left ditch 1 in the tunnel is discharged to the outside of the tunnel, it will be combined with the water discharged from the central ditch 3 and passed through the wastewater diversion ditch Discharged into the water culvert; Since a temporary partition wall 11 and a temporary cofferdam 24 are sequentially arranged in the water culvert, two sedimentation tanks can be formed before and after the temporary partition wall, and an overflow port 12 is provided near the upper end of the temporary partition wall, so as to ensure that the water flow can slowly pass through the temporary partition wall 11, so that the water flow is fully precipitated in the upper pool before entering the next sedimentation tank, and finally the water body is purified and flows out through the temporary cofferdam 24; During the wastewater sedimentation process, it can be decided whether to adopt other coagulation measures according to the situation, such as the coagulation sedimentation method, that is, adding flocculants to the water to destroy the stability of the sol, so that the colloid and suspended particles in the water are flocculated into larger flocs, so as to be separated from the water out, achieving the purpose of water purification; and too much sediment will reduce the wastewater capacity of the sedimentation tank, so after a period of use, mechanical means such as excavators, forklifts, etc. can be used to properly clean the sediment at the bottom of the tank to ensure the normal use of the sedimentation tank; at the same time, the clean water in the temporary right ditch in the tunnel is discharged to the outside of the tunnel and then discharged into the clean water direct discharge sedimentation tank through the clean water diversion ditch, and after sedimentation and purification in the clean water direct discharge sedimentation tank, it is discharged into the water culvert downstream of the temporary cofferdam; finally, the clean water and sewage discharged by diversion in the tunnel will be collected in the water culvert downstream of the temporary cofferdam after sedimentation and purification treatment by the structure of the present invention, and can still be pumped for other water use such as construction production, dust reduction cleaning and structure maintenance in the tunnel.

[0051] Further, in a preferred embodiment, see Figure 1 、 Figure 3and Figure 4 Since the temporary left ditch 1 is for discharging sewage, and the temporary right ditch 2 is for discharging clean water, the gabion stone cage anti-filtration facility 6 set in the temporary left ditch 1 is set every 50 m~100 m, and the gabion stone cage anti-filtration facility 6 set in the temporary right ditch 2 is set every 150 m~200 m; the gabion stone cage anti-filtration facility 6 includes a multi-layer gabion stone cage 601 stacked in a trapezoidal shape, and sandbags 602 are placed adjacent to the gabion stone cage 601 at the downstream position of the gabion stone cage 601; preferably, the stones filled in the gabion stone cage must be dense, the gaps between the stones are filled with graded crushed stones, and the height of the filling stones should be higher than the mesh box 2 cm; sandbags should be stacked layer by layer to ensure a neat and beautiful appearance; sandbags should be filled with sand with good permeability and low mud and powder content; in actual application, this gabion stone cage filtration facility should be cleaned manually in time according to the thickness of the sediment after filtration, and the sediment should be removed to the bottom of the ditch; the reason for setting up single-sided sandbags is to prevent the overflow of water from the ditch in the cave due to excessive water inflow and untimely filtration.

[0052] Further, in a preferred embodiment, see Figure 1 The gabion stone cage filtration facility 6 is arranged in the temporary left ditch 1 and the temporary right ditch 2 adjacent to the central ditch inspection well 4, and is located upstream of the central ditch inspection well 4, so that when the water in the side ditches overflows and flows onto the leveling layer, the overflow can be introduced into the central ditch through the temporary arrangement of the channel steel retaining dam.

[0053] Further, in a preferred embodiment, see Figure 2 and Figure 5The clean water diversion and drainage ditch 8 includes a clean water horizontal culvert 801 connecting the temporary right ditch 2 in the left and right tunnels, one end of which is connected to the outlet end of the clean water horizontal culvert 801 and the other end is connected to the clean water direct discharge sedimentation tank 7. The wastewater diversion and drainage ditch 9 includes a wastewater horizontal culvert 901 connecting the temporary left ditch 1 and the central ditch 3 in the same tunnel, one end of which is connected to the outlet end of the wastewater horizontal culvert 901 and the other end is connected to the wastewater diversion and drainage open ditch 902 of the water culvert 5 upstream of the temporary partition wall 11; wherein, the clean water horizontal culvert 801 and the wastewater horizontal culvert 901 are in the form of culverts so as not to affect the passage of vehicles or personnel at the tunnel entrance, and the clean water horizontal culvert is buried above the wastewater horizontal culvert; the clean water diversion and drainage open ditch and the wastewater diversion and drainage open ditch should be set on the wall of the tunnel entrance site. In addition, a brick structure should be adopted and cement mortar should be applied on the outside; when the flow of natural rainwater and mountain water is large, the size of the open ditch can be increased, but the range of the open ditch should not exceed the construction red line, and when the rainwater and sewage in the field outside the tunnel are gathered, the wastewater or clean water discharged from the tunnel cannot overflow; and the open ditch should be arranged for manual cleaning in time according to the thickness of the sediment; in the present invention, the construction cost of the open ditch is low, and it is more convenient to clean the sediment. The wastewater, natural rainwater and mountain water after cleaning the site roads can also be collected into the open ditch for treatment; in addition, the direction of the horizontal convergence of the clean water transverse ditch and the wastewater transverse ditch is not fixed. It can be designed in combination with the elevation difference direction of the left and right tunnel entrances, the direction of the designed cross slope of the tunnel and the drainage direction of the water culvert to ensure that the water flow can converge from high to low.

[0054] Further, in a preferred embodiment, see Figure 2 The present invention also includes a wastewater inlet hidden drain ditch 19 and a drop platform 18; one end of the wastewater inlet hidden drain ditch 19 is buried and connected to the wastewater drainage open ditch 902, and the other end extends into the water culvert 5 and connects to the drop platform 18; usually, the culvert site is generally buried at a high depth and has a high height difference with the drainage system outside the tunnel, so a drop platform should be set to ensure that the water flow rate is buffered. The wastewater inlet hidden drain ditch can prevent excessive water flow from splashing and overflowing wastewater and affecting the surrounding environment; and a filter steel mesh is set at the water inlet of the wastewater inlet hidden drain ditch to prevent large-sized stones, large pieces of wood and garbage from entering the sedimentation tank; the parts where the isolation steel mesh is set should be regularly observed for obstructions and cleaned in time.

[0055] Furthermore, in a preferred embodiment, a layer of steel mesh is provided in the overflow port 12, and the height of the overflow port 12 from the bottom of the temporary partition wall 11 is determined by the maximum water inflow in the tunnel and the water storage capacity allowed by the bearing capacity of the water culvert.

[0056] Further, in a preferred embodiment, see Figure 1The present invention also includes a water collection pool 14 arranged on the drainage route of the temporary right ditch 2 and upstream of the gabion stone cage anti-filtration facility 6. A water pump is provided in the water collection pool 14. In this way, for water use in the tunnel construction that does not require high standards, such as road washing, mechanical equipment washing, maintenance, etc., the water accumulated in the water collection pool can be pumped out by the water pump to achieve the recycling of water in the tunnel; and the water collection pool 14 is located upstream of the gabion stone cage anti-filtration facility 6. The gabion stone cage anti-filtration facility 6 can be used to block the water formed by the side ditch to increase the water depth of the water collection pool, thereby facilitating water pumping and recycling.

[0057] Further, in a preferred embodiment, see Figure 1 A sewage pump 15 is provided in the lower guide pit 13 , and the water outlet of the sewage pump 15 is connected to the temporary left ditch 1 through a sewage discharge pipe.

[0058] Further, in a preferred embodiment, see Figure 2 The present invention also includes a roof drainage ditch 17 arranged at the top of the tunnel entrance, and the water outlet end of the roof drainage ditch 17 is connected to the clean water diversion ditch 8. Example 2

[0059] Below, the structure and construction method of the present invention are further described in detail by taking a tunnel of a certain project in Hezhou City as an example.

[0060] This split tunnel consists of a left tunnel from ZK74+071 to ZK78+259 and a right tunnel from YK74+050 to YK78+249, with an average length of 4,193.5 meters. It features four portals, five vehicular tunnels, and 11 pedestrian tunnels. The tunnel entrance is located in Beituo Town, Zhaoping County, Hezhou City, Guangxi Province, and passes through the mountainous terrain near Fengqing Village. The tunnel entrance is well-developed with surface water. A stream flows only 10 to 20 meters from the entrance, its water volume affected by atmospheric precipitation. A gully exists at the top of the right-line tunnel, affected by seasonal erosion. There is a drinking water source at the entrance, and there are no buildings or utility poles within 300 meters of the entrance, ensuring favorable construction conditions with no impact. The tunnel portal section features a steep, upslope slope with a significant drop in elevation, connecting the bridge and tunnel. A drinking water point is located at the entrance. After excavation, the tunnel walls and slopes are unstable, making them susceptible to collapse and fragmentation under conditions such as inappropriate blasting and surface water erosion. Surface and groundwater are slightly corrosive to concrete structures in Class II environments, slightly corrosive to concrete structures under Class B conditions, and slightly corrosive to steel bars in reinforced concrete structures under alternating dry-wet conditions. The tunnel site's normal water inflow during normal water conditions is 1874.19 m / day, with a maximum inflow of 6968 m / day. The entrance and exit portals are overlain by silty clay and highly weathered fine sandstone from a crusher. This thick overburden makes the natural slope stable, but similar to nearby artificial slopes, it is prone to shallow collapse. Disturbance can cause the tunnel portal and upslope to collapse. There are four water supply points for villagers at the entrance of the tunnel. The river gully system at the entrance of the tunnel is well developed and fed by rainwater. The river is deep and the terrain is undulating. The slope at the entrance is >45. Figures 1 to 3 The steps of tunnel wastewater treatment measures using the method of the present invention in this project are as follows:

[0061] S1. Parameter design of sewage discharge structure

[0062] Combined with the geological survey report, tunnel hydrogeological survey and on-site investigation, the normal water inflow of the tunnel and the maximum water inflow during peak periods are verified and determined. Based on the normal water inflow and the maximum water inflow during peak periods, and in combination with the actual engineering drawings of the tunnel, the design parameters of the sewage structure are calculated and determined;

[0063] S2. Construction of drainage structure in the tunnel

[0064] The drainage structure in the tunnel includes a central ditch 3, a central ditch inspection well 4, a lower pilot pit 13, a temporary left ditch 1, a temporary right ditch 2 and a gabion stone cage filter facility 6; wherein, the central ditch 3, the central ditch inspection well 4 and the lower pilot pit 13 are structural facilities that need to be constructed during the tunnel excavation construction, and they can be constructed according to conventional methods and steps, and the present invention will not be described in detail;

[0065] When constructing the above-mentioned drainage structure in the tunnel, the construction of the permanent side ditch and cable trench in the tunnel should be delayed. The permanent side ditch and cable trench can be constructed after the tunnel excavation is completed and sewage is no longer needed. For the construction of the temporary left ditch 1 and the temporary right ditch 2, please refer to Figure 7 , when constructing the pavement leveling layer 25 and the inverted arch filling layers on both sides, a temporary left ditch 1 and a temporary right ditch 2 can be formed by controlling the natural height difference between the pavement leveling layer and the inverted arch filling layers 26 on both sides; then, a gabion stone cage filtration facility 6 is set in the temporary left ditch 1 and the temporary right ditch 2 by hoisting; wherein, the temporary right ditch 2 is connected to the drainage hole 16 in the secondary lining of the tunnel, and the temporary left ditch 1 is connected to the lower pilot pit 13; at the same time, it should be verified whether the water-passing cross-sectional area of ​​the temporary left ditch 1 and the temporary right ditch 2 meets the drainage demand of the normal water inflow of the tunnel; if not, the initial pouring height of the inverted arch filling layers 26 on both sides can be reduced, thereby increasing the cross-sectional size of the side ditches on both sides; and the central ditch 3 is not used as a drainage function during the normal water inflow during the construction period. When the maximum water inflow during the peak period exceeds the drainage capacity of the drainage ditches on both sides, the central ditch is activated as a drainage auxiliary; usually, the gabion stone cage filtration facility 6 should be used every 50 to 100 m is set up in the temporary left ditch 1 and the temporary right ditch 2, and the cofferdam spacing can be dynamically adjusted according to the content of solid suspended particles in the sewage; if necessary, the central ditch 3 can also be equipped with gabion stone cage filter facilities 6 as an auxiliary for temporary drainage during peak hours to reduce sediment deposition in the central ditch 3 and facilitate dredging in the later period; for details, please refer to Figure 3 and Figure 4 The gabion stone cage filter facility 6 includes multiple layers of gabion stone cages 601 stacked in a trapezoidal shape, and sandbags 602 are placed adjacent to the gabion stone cages 601 and at the downstream position of the gabion stone cages 601; preferably, the stones filled in the gabion stone cages 601 must be dense, and the gaps between the stones are filled with graded gravel, and the height of the filling stones should be 2 cm higher than the mesh box; the sandbags 602 should be stacked layer by layer to ensure a neat and beautiful appearance; the sandbags 602 should be filled with sand with good permeability and low mud and powder content; in actual application, this gabion stone cage filter facility 6 should be considered After filtration, the thickness of the sediment is cleaned manually in time, and the sludge is removed to the bottom of the ditch. The reason for setting up sandbags on one side is to prevent the overflow of water from the ditch in the tunnel due to the untimely backfiltration caused by excessive water inflow. In addition, the height of the gabion stone cage 601 is determined according to the height between the side ditches on both sides and the leveling layer 25 of the road surface in the tunnel. The gabion stone cage 601 needs to be slightly higher than the leveling layer 25 of the road surface, and the sandbag 602 should be lower than the leveling layer 25 of the road surface to prevent the water from exceeding the leveling layer, overflowing the drainage ditches on both sides, and flowing into the road surface to cause pollution.

[0066] S3. Construction of drainage facilities outside the tunnel

[0067] See also Figure 2, the drainage facilities outside the tunnel include clean water diversion and drainage ditch 8, clean water direct discharge ditch 10, clean water direct discharge sedimentation tank 7 and waste water diversion and drainage ditch 9; the drainage facilities outside the tunnel are buried in the form of dark ditch and dark pipe within the scope of the tunnel entrance construction site to reduce the impact on the layout of the construction site and driving; specifically, the clean water diversion and drainage ditch 8 includes a clean water horizontal dark ditch 801 connecting the temporary right ditch 2 in the left and right tunnels, one end of which is connected to the outlet end of the clean water horizontal dark ditch 801 and the other end is connected to the clean water diversion and drainage open ditch 802 of the clean water direct discharge sedimentation tank 7; the waste water diversion and drainage ditch 9 includes a waste water horizontal dark ditch 901 connecting the temporary left ditch 1 and the central ditch 3 in the same tunnel, one end of which is connected to the outlet end of the waste water horizontal dark ditch 901 and the other end is connected to the waste water diversion and drainage open ditch 902 of the water culvert 5 upstream of the temporary partition wall 11; the water flow section of the dark ditch and dark pipe The volume should not be less than 150% of the drainage ditch in the tunnel, and at the same time, the length of the blind ditch and blind pipe should be as short as possible to reduce the adverse effects of silt accumulation. The part away from the construction site can be set up with an open ditch, and the size of the open ditch should be consistent with the size of the blind ditch and blind pipe. Among them, when constructing the clean water diversion ditch 8, the clean water direct discharge ditch 10, the clean water direct discharge sedimentation tank 7 and the wastewater diversion ditch 9, one end of the clean water diversion ditch 8 is controlled to be connected to the drainage outlet of the temporary right ditch 2 in the tunnel, and the other end is connected to the clean water direct discharge sedimentation tank 7; one end of the wastewater diversion ditch 9 is controlled to be connected to the drainage outlet of the temporary left ditch 1 and the central ditch 3 in the tunnel, and the other end is connected to the water culvert 5 upstream of the temporary partition wall 11; the water outlet of the clean water direct discharge sedimentation tank 7 is controlled to be connected to the water culvert 5 downstream of the temporary cofferdam 24 through the clean water direct discharge ditch 10;

[0068] S4. Permanent and temporary construction of sedimentation tanks

[0069] See also Figure 2 , Figure 5 and Figure 6, calculate and determine the height of the overflow port 12 and the temporary cofferdam 24, so that the allowable water storage capacity of the water culvert is greater than the maximum water inflow in the tunnel, and then reduce the backfill height of the backfill soil on the top of the water culvert 5, so that the self-weight G1 of the reduced backfill soil on the top of the water culvert is greater than the sum of the stored water gravity G2 under the allowable water storage capacity of the water culvert, the self-weight G3 of the temporary partition wall and the self-weight G4 of the temporary cofferdam. Taking advantage of the large cross-sectional dimensions of the culvert and the passage, a temporary cofferdam is first built at the outlet of the permanent water culvert 5 across the tunnel in the order of construction from downstream to upstream. A cofferdam 24 is then built, and a temporary partition wall 11 is then built in the middle of the water culvert 5. An overflow outlet 12 is reserved at the top of the temporary partition wall 11, so that a primary sedimentation tank is formed between the temporary partition wall 11 and the upstream surface of the water culvert, and a secondary sedimentation tank is formed between the temporary cofferdam and the temporary partition wall 11. In this way, the sewage flowing through the primary sedimentation tank can form a certain height of still water in the culvert and only slowly overflow through the overflow outlet, thereby fully playing the role of settling solid particles. Similarly, the sewage overflowing into the secondary sedimentation tank can be overflowed through the temporary cofferdam to precipitate the sewage again;

[0070] In the above, the design of the overflow port 12 and the temporary cofferdam 24 needs to take into account the large amount of water stored in the two-stage sedimentation tank in the culvert, and the gravity load of the culvert foundation due to the self-weight of the temporary partition wall 11 and the temporary cofferdam 24 exceeds the design value. Since the height of the overflow port 12 determines the allowable water storage capacity of the first-stage sedimentation tank, and the height of the temporary cofferdam 24 determines the allowable water storage capacity of the second-stage sedimentation tank, the height of the overflow port 12 and the height of the temporary cofferdam 24 jointly determine the allowable water storage capacity of the culvert. Before construction, the height of the overflow port 12 and the temporary cofferdam 24 should be calculated and determined so that the allowable water storage capacity of the culvert is greater than the maximum water inflow in the tunnel, and taking into account safety factors, in order to make the stored water gravity G2 under the allowable water storage capacity of the culvert, and the temporary When the additional load formed by the gravity G3 of the partition wall and the gravity G4 of the temporary cofferdam does not exceed the allowable bearing capacity of the culvert design, it can be achieved by reducing the backfill height of the backfill soil on the top of the water culvert 5 so that the deadweight G1 of the lowered backfill soil height is greater than the sum of the stored water gravity G2 under the allowable water storage capacity of the water culvert, the self-gravity G3 of the temporary partition wall and the self-gravity G4 of the temporary cofferdam; in addition, the thickness of the temporary partition wall 11 should be designed to withstand the water pressure difference on both sides. When the water pressure difference is large and the deadweight of the partition wall is difficult to withstand or it is not cost-effective to thicken the partition wall, gabion stone cages can be used to build it downstream of the partition wall to form support; and the temporary partition wall 11 is not plastered, so that the seepage between the bricks and the gaps can be used for further filtration.

[0071] S5. Wastewater discharge inspection and acceptance

[0072] Discharge the sewage in the tunnel hole and test the clean water in the water culvert 5 downstream of the temporary cofferdam 24. If the sedimentation effect is still not satisfactory, add a sandbag wall in the two-stage main sedimentation tank as a supplementary measure;

[0073] S6. Regular cleaning of the main sedimentation tank

[0074] Manual or mechanical access roads should be reserved upstream and downstream of the water culvert 5 to regularly clean the solid particles accumulated in the main sedimentation tank; the solid particles collected after cleaning should be collected and dried, and then dehydrated for centralized treatment.

[0075] S7. Regular monitoring of sewage discharge

[0076] The water quality downstream of the temporary culvert cofferdam should be monitored regularly, and any abnormalities should be dealt with in a timely manner.

Claims

1. A permanent and temporary sewage discharge sedimentation structure used in the excavation and construction of a water-rich mountain tunnel, comprising a central ditch (3) and a central ditch inspection well (4) arranged in the tunnel, a lower pilot pit (13) arranged near the tunnel face for collecting all sewage upstream of the tunnel, and a water culvert (5) adjacent to the tunnel entrance, characterized in that Also includes: A temporary left ditch (1) and a temporary right ditch (2) are respectively arranged on the left and right sides of the tunnel, a gabion stone cage anti-filtration facility (6) is arranged in the temporary left ditch (1) and the temporary right ditch (2), a clean water direct discharge sedimentation tank (7), a clean water diversion ditch (8), a clean water direct discharge ditch (10) and a wastewater diversion ditch (9) are arranged outside the tunnel, a temporary partition wall (11) is arranged in the water culvert (5), a temporary cofferdam (24) is arranged in the water culvert (5) and is located downstream of the temporary partition wall (11), an overflow port (12) is arranged near the top of the temporary partition wall (11), and a water collection tank (14) is arranged on the drainage route of the temporary right ditch (2) and is located upstream of the gabion stone cage anti-filtration facility (6); The temporary right ditch (2) is connected to the drainage hole (16) in the secondary lining of the tunnel to discharge the clean water flowing out of the mountain above the secondary lining of the tunnel; the temporary left ditch (1) is connected to the lower pilot pit (13) to discharge the sewage collected in the lower pilot pit (13); one end of the clean water drainage ditch (8) is connected to the drainage outlet of the temporary right ditch (2) in the tunnel, and the other end is connected to the clean water direct discharge sedimentation tank (7); one end of the wastewater drainage ditch (9) is connected to the temporary left ditch in the tunnel. The drain outlet of the ditch (1) is connected to the central ditch (3), and the other end is connected to the water culvert (5) upstream of the temporary partition wall (11); the water outlet of the clean water direct discharge sedimentation tank (7) is connected to the water culvert (5) downstream of the temporary cofferdam (24) through the clean water direct discharge ditch (10); a water pump is provided in the water collection tank (14); a sewage pump (15) is provided in the lower guide pit (13), and the water outlet of the sewage pump (15) is connected to the temporary left ditch (1) through a sewage discharge pipe.

2. The permanent and temporary sewage discharge sedimentation structure in the excavation construction of a water-rich mountain tunnel as claimed in claim 1 is characterized in that: The gabion gabion filtration facilities (6) arranged in the temporary left ditch (1) are arranged every 50m to 100m, and the gabion gabion filtration facilities (6) arranged in the temporary right ditch (2) are arranged every 150m to 200m; the gabion gabion filtration facilities (6) include multiple layers of gabion gabions (601) stacked in a trapezoidal shape, and sandbags (602) stacked adjacent to the gabion gabions (601) at a downstream position of the gabion gabions (601).

3. The permanent and temporary sewage discharge sedimentation structure in the excavation construction of a water-rich mountain tunnel as claimed in claim 1 is characterized in that: The gabion stone cage filtration facility (6) is arranged in the temporary left ditch (1) and the temporary right ditch (2) adjacent to the central ditch inspection well (4) and is located upstream of the central ditch inspection well (4).

4. The permanent and temporary sewage discharge sedimentation structure in the excavation construction of a water-rich mountain tunnel as claimed in claim 1 is characterized in that: The clean water drainage ditch (8) includes a clean water transverse culvert (801) connected to the temporary right ditch (2) in the left and right tunnels, and a clean water drainage open ditch (802) whose one end is connected to the outlet of the clean water transverse culvert (801) and whose other end is connected to the clean water direct discharge sedimentation tank (7); the waste water drainage ditch (9) includes a waste water transverse culvert (901) connected to the temporary left ditch (1) and the central ditch (3) in the same tunnel, and whose one end is connected to the outlet of the waste water transverse culvert (901) and whose other end is connected to the waste water drainage open ditch (902) of the water culvert (5) upstream of the temporary partition wall (11).

5. The permanent and temporary sewage discharge sedimentation structure in the excavation construction of a water-rich mountain tunnel as claimed in claim 4 is characterized in that It also includes a wastewater inlet hidden drainage ditch (19) and a drop platform (18); one end of the wastewater inlet hidden drainage ditch (19) is buried and connected to the wastewater drainage ditch (902), and the other end extends into the water culvert (5) and connects to the drop platform (18).

6. The permanent and temporary sewage discharge sedimentation structure in the excavation construction of a water-rich mountain tunnel as claimed in claim 1 is characterized in that: A layer of steel mesh is provided in the overflow port (12), and the height of the overflow port (12) from the bottom of the temporary partition wall (11) is determined by the maximum water inflow in the tunnel and the water storage capacity allowed by the bearing capacity of the water culvert.

7. The permanent and temporary sewage discharge sedimentation structure in the construction of a water-rich mountain tunnel as claimed in claim 1 is characterized in that It also includes a tunnel roof drainage ditch (17) arranged at the top of the tunnel entrance, wherein the water outlet end of the tunnel roof drainage ditch (17) is connected to the clean water diversion ditch (8).

8. The construction method of the permanent and temporary sewage discharge sedimentation structure in the excavation of the water-rich mountain tunnel is characterized by The steps include: S1. Parameter design of sewage discharge structure Calculate and determine the design parameters of the sewage structure based on the normal water inflow of the tunnel and the maximum water inflow during peak periods, combined with the actual engineering drawings of the tunnel; S2. Construction of drainage structure in the tunnel The permanent side ditch and cable trench in the tunnel are delayed in construction. When constructing the pavement leveling layer and the inverted arch filling layer on both sides, a temporary left ditch (1) and a temporary right ditch (2) are formed by controlling the natural height difference between the pavement leveling layer and the inverted arch filling layer on both sides; then, a gabion stone cage filter facility (6) is set in the temporary left ditch (1) and the temporary right ditch (2); wherein the temporary right ditch (2) is connected to the drainage hole (16) in the secondary lining of the tunnel, and the temporary left ditch (1) is connected to the lower pilot pit (13); S3. Construction of drainage facilities outside the tunnel A clean water drainage ditch (8), a clean water direct discharge ditch (10), a clean water direct discharge sedimentation tank (7), and a waste water drainage ditch (9) are constructed outside the tunnel; wherein one end of the clean water drainage ditch (8) is connected to the drainage outlet of the temporary right ditch (2) in the tunnel, and the other end is connected to the clean water direct discharge sedimentation tank (7); one end of the waste water drainage ditch (9) is connected to the drainage outlet of the temporary left ditch (1) and the central ditch (3) in the tunnel, and the other end is connected to the water culvert (5) upstream of the temporary partition wall (11); the water outlet of the clean water direct discharge sedimentation tank (7) is connected to the water culvert (5) downstream of the temporary cofferdam (24) through the clean water direct discharge ditch (10); S4. Permanent and temporary construction of sedimentation tanks Calculate and determine the heights of the overflow (12) and the temporary cofferdam (24) so ​​that the permissible water storage capacity of the water culvert is greater than the maximum water inflow in the tunnel. Then, reduce the backfill height of the backfill soil at the top of the water culvert (5) so that the self-weight G1 of the reduced backfill soil at the top of the water culvert is greater than the sum of the stored water gravity G2 under the permissible water storage capacity of the water culvert, the self-weight G3 of the temporary partition wall, and the self-weight G4 of the temporary cofferdam. Then, in accordance with the construction sequence from downstream to upstream, first build a temporary cofferdam (24) at the outlet position of the permanent water culvert (5) across the tunnel, and then build a temporary partition wall (11) at the middle position of the water culvert (5), and reserve an overflow (12) at the top of the temporary partition wall (11), so that a primary sedimentation tank is formed between the temporary partition wall (11) and the upstream surface of the water culvert, and a secondary sedimentation tank is formed between the temporary cofferdam and the temporary partition wall (11); S5. Wastewater discharge inspection and acceptance The sewage in the tunnel is discharged and the clean water in the water culvert (5) downstream of the temporary cofferdam (24) is tested.

9. The construction method of a permanent and temporary sewage discharge sedimentation structure in the excavation construction of a water-rich mountain tunnel as claimed in claim 8, characterized in that: The temporary partition wall (11) is constructed of bricks and is not plastered.

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