A waterproof system and technology for multi - layer structures of tunnels in high halite - containing rock strata

Abstract

A multi-structure waterproof system for tunnels in high-salt rock formations includes an annular system and a longitudinal system. The annular system includes a grouting ring, a primary support, a first waterproof layer, a water-proof concrete layer, a second waterproof layer and a second lining arranged in sequence. The longitudinal system includes a water-blocking tenon and a transition section, and the transition section is arranged at the junction of the halite rock formation and the non-halite rock formation. The annular system blocks groundwater from entering the structure to avoid cl-corrosion of the structure and resist water pressure and halite expansion force; the longitudinal system inhibits groundwater flow to prevent structural damage caused by halite dissolution around the tunnel; and the use of this system can reduce the design grade of the second lining structure concrete and avoid the problem of excessive hydration heat and cracks in high-grade concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and in particular to a multi-structure waterproofing system and process for a tunnel in a high-salt rock formation. Background Art

[0002] In the construction of tunnel projects, similar conditions to rock salt rock formations are often encountered. For example, the Chengdu-Kunming Railway opened to traffic in 1970, the Nanluliangshan Tunnel of the Central and Southern Shanxi Railway Channel opened in June 2013, and the Jiaozishan Tunnel of the Yongguang Line of the Chengdu-Kunming Railway double-track opened on September 23, 2016. All of them have problems such as lining corrosion, water seepage in the tunnel, or cracking of the side walls. The engineering geological environment of these projects is mainly sulfate formations containing gypsum and calcium glauberite, but relatively less rock salt, and the groundwater conditions are well developed.

[0003] At present, the Friendship Tunnel of the Laos-China Railway has discovered rock salt rock formations at both ends of the cross-border section, which are more than 1,300 meters long. The NaCl content of this formation is as high as 80%, with high purity. The seepage water in the tunnel is slightly salty to extremely salty, which is rare at home and abroad, and there is no mature engineering construction experience to draw on. Objectively, during the concrete pouring process or use of the tunnel concrete structure, invisible fine cracks or visible cracks and other defects are inevitably produced, which provide a good channel for groundwater infiltration. The salt rock bottom layer has strong solubility and strong corrosiveness under the action of groundwater, which will affect the tunnel's waterproofing system for a long time. Summary of the invention

[0004] The purpose of the present invention includes providing a multi-structure waterproof system for tunnels in high-salt rock formations, which blocks groundwater from entering the structure through an annular system to avoid cl - The system can resist the erosion of the structure and water pressure and the expansion force of halite rock; through the longitudinal system, the flow of groundwater can be suppressed to prevent the structural damage caused by the dissolution of halite rock around the cave; at the same time, the use of this system can reduce the design grade of the secondary lining structure concrete and avoid the problem of cracks caused by excessive hydration heat of high-grade concrete.

[0005] Another object of the present invention is to provide a multi-structure waterproofing process for tunnels in high-salt rock formations, which is conducive to orderly construction.

[0006] The embodiments of the present invention are implemented by the following technical solutions:

[0007] A multi-structure waterproofing system for a tunnel in a high-salt rock formation comprises an annular system and a longitudinal system. The annular system comprises a grouting ring, a primary support, a first waterproof layer, a water-proof concrete layer, a second waterproof layer and a secondary lining which are arranged in sequence. The longitudinal system comprises a water-blocking tenon and a transition section. The transition section is arranged at the junction of the halite rock formation and the non-halite rock formation.

[0008] Preferably, the grouting ring is the radial grouting around the surrounding rock. The cement slurry material is prepared by mixing with brine, and the grouting pipe includes epoxy-coated steel pipe.

[0009] Preferably, the primary support is made of C30 corrosion-resistant early high-strength shotcrete, the water-proof concrete layer is made of C35 corrosion-resistant polymer concrete, the secondary lining is made of C40 corrosion-resistant impermeable concrete. The water-proof concrete layer is plain concrete, and the secondary lining is reinforced concrete. The steel bars are epoxy-coated steel bars.

[0010] Preferably, the mix proportion of the C30 corrosion-resistant early high-strength shotcrete includes the following components by weight fraction: 352 parts of cement, 118 parts of strengthening admixture, 855 parts of sand, 790 parts of crushed stone, 8.46 parts of water reducer, 2.35 parts of air-entraining agent, 56.4 parts of preservative, 23.5 parts of accelerating agent, and 118 parts of water;

[0011] Among them, the strengthening admixture includes the following components by weight fraction: 20 - 25 parts of silica fume, 20 - 25 parts of fly ash, 10 - 15 parts of modified nano material, and 7 - 10 parts of nano carbon fiber;

[0012] Among them, the modified nano material includes modified nano CaCO3 and modified nano TiO2, and the ratio of modified nano CaCO3:modified nano TiO2 = 1:0.5 - 2.

[0013] Preferably, the mix proportion of the C35 corrosion-resistant polymer concrete includes the following components by weight ratio: 308 parts of cement, 88 parts of fly ash, 44 parts of expansion agent, 44 parts of polymer emulsion, 736 parts of sand, 1017 parts of crushed stone, 5.28 parts of water reducer, 120 parts of water, and 1.23 parts of defoaming agent;

[0014] Among them, the polymer emulsion includes at least one of styrene-acrylic emulsion, acrylic emulsion, SBR latex, and acrylate.

[0015] Preferably, the mix proportion of the C40 corrosion-resistant impermeable concrete includes the following components by weight ratio: 255 parts of cement, 42 parts of expansion agent, 746 parts of sand, 1029 parts of sand and gravel, 6.38 parts of water reducer, 0.58 parts of air-entraining agent, and 150 parts of water.

[0016] Preferably, the contour shapes of the water-proof concrete layer and the secondary lining away from the surrounding rock surface are circular. The water-proof concrete layer includes the arch wall water-proof concrete layer at the arch wall and the invert water-proof concrete layer at the tunnel bottom. The thickness of the invert water-proof concrete layer is greater than that of the arch wall water-proof concrete layer. The secondary lining includes the arch wall secondary lining at the arch wall and the invert secondary lining at the tunnel bottom. The water-proof concrete layer is one slab every 10 m or 12 m longitudinally, and the secondary lining is one slab every 10 m or 12 m longitudinally. The length of each slab of the water-proof concrete layer is the same as that of the secondary lining.

[0017] Preferably, the first longitudinal construction joint of the arch wall water-proof concrete layer and the inverted arch water-proof concrete layer is staggered from the second longitudinal construction joint of the arch wall secondary lining and the inverted arch secondary lining, and the first circumferential construction joint between the water-proof concrete layer plates is staggered from the second circumferential construction joint between the secondary lining plates. The embedded rubber water stop belts are arranged at the first longitudinal construction joint, the second longitudinal construction joint, the first circumferential construction joint, and the second circumferential construction joint.

[0018] Preferably, the first waterproof layer includes laying the first geotextile and the EVA waterproof board in a full circle, and the primary support, the first geotextile, the EVA waterproof board, and the water-proof concrete layer are arranged in sequence;

[0019] The second waterproof layer includes laying the self-adhesive waterproof board in a full circle, and the water-proof concrete layer, the self-adhesive waterproof board, and the secondary lining are arranged in sequence.

[0020] Preferably, the water-blocking tenons are arranged at the bottom of the inverted arch water-proof concrete layer, arranged at intervals along the longitudinal direction of the tunnel. The upper end surface of the water-blocking tenon is connected to the bottom surface of the inverted arch water-proof concrete layer, and the tenon body of the water-blocking tenon penetrates through the primary support and is distributed.

[0021] Preferably, the water-blocking tenon and the inverted arch water-proof concrete layer are configured to be integrally cast simultaneously.

[0022] Preferably, the transition section has a preset longitudinal length along the axial direction of the tunnel, the transition section is arranged in the area belonging to the non-salt formation, and the tunnel structure of the transition section is the same as that of the tunnel structure in the salt rock formation.

[0023] Preferably, a stop wall is arranged at one end of the transition section far from the salt rock formation. The stop wall is arranged in a ring shape and is cast integrally with the secondary lining of the transition section.

[0024] A multi-structure waterproof technology for tunnels in high-salt rock formations includes the following steps:

[0025] S1, primary support operation;

[0026] S2, pouring the inverted arch water-proof concrete layer;

[0027] S3, pouring the secondary lining structure concrete at the inverted arch;

[0028] S4, pouring the filling layer of the inverted arch secondary lining;

[0029] S5, pouring the arch wall water-proof concrete layer;

[0030] S6, pouring the secondary lining concrete at the arch wall.

[0031] Preferably, construction preparation is also carried out before step S1, and grouting is carried out to stop water;

[0032] Between step S1 and step S2, grouting operation and hanging the EVA waterproof board at the primary support of the inverted arch are also carried out in sequence;

[0033] Between step S2 and step S3, a self-adhesive waterproof board is also laid on the inverted arch water-proof concrete layer;

[0034] Between step S4 and step S5, an EVA waterproof board is also hung at the arch wall;

[0035] Between step S5 and step S6, a self-adhesive waterproof board is also laid at the arch wall water-proof concrete layer;

[0036] After step S6, concrete curing is also carried out.

[0037] Preferably, when the construction area needs to pass through a non-salt area from a salt rock area and enter the next salt rock area, both ends of the non-salt area on the construction path are constructed according to steps S1-S6.

[0038] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects: It blocks groundwater from entering the structure through the annular system, avoids the erosion of the structure by cl - and resists water pressure and rock salt expansion force; through the longitudinal system, it inhibits the flow of groundwater and prevents the erosion of the surrounding rock salt in the tunnel from causing structural damage; at the same time, using this system can reduce the concrete design grade of the secondary lining structure and avoid the problem of excessive hydration heat cracks in high-strength concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings required to be used in the embodiment will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0040] Figure 1 It is a schematic diagram of the overall structure of the multi-structural waterproof system for tunnels in high salt rock strata provided by the embodiment of the present invention;

[0041] Figure 2 It is a schematic diagram of the structure between the primary support, the water-proof concrete layer and the secondary lining provided by the embodiment of the present invention;

[0042] Figure 3 It is a first schematic diagram of the water-stop tenon provided by the embodiment of the present invention;

[0043] Figure 4 It is a second schematic diagram of the water-stop tenon provided by the embodiment of the present invention;

[0044] Figure 5 It is a first schematic diagram of the cooperation between the self-propelled long trestle and the fully enclosed formwork provided by the embodiment of the present invention;

[0045] Figure 6This is the second structural schematic diagram of the self-propelled long trestle cooperating with the fully enclosed formwork provided by the embodiment of the present invention;

[0046] Figure 7 This is the schematic diagram of the transition section between the high salt-bearing rock formation and the non-salt formation provided by the embodiment of the present invention;

[0047] Figure 8 This is the structural schematic diagram of the first longitudinal construction joint and the second longitudinal construction joint provided by the embodiment of the present invention;

[0048] Figure 9 This is the structural schematic diagram of the first circumferential construction joint and the second circumferential construction joint provided by the embodiment of the present invention;

[0049] Figure 10 This is the flow chart of the multi-structure waterproofing process for the tunnel in the high salt-bearing rock formation provided by the embodiment of the present invention.

[0050] Icon: 100 - grouting ring, 200 - primary support, 300 - first waterproof layer, 400 - water-blocking concrete layer, 410 - arch wall water-blocking concrete layer, 420 - invert water-blocking concrete layer, 430 - first longitudinal construction joint, 440 - first circumferential construction joint, 500 - second waterproof layer, 600 - secondary lining, 610 - arch wall secondary lining, 620 - invert secondary lining, 630 - second longitudinal construction joint, 640 - second circumferential construction joint, 700 - water-blocking tenon, 800 - transition section, 900 - self-propelled long trestle, 910 - fully enclosed formwork, 911 - stop board, 912 - intermediate long formwork, 913 - feeding window, 914 - concrete area to be poured, 20 - salt rock formation, 21 - non-salt formation. Detailed implementation manners

[0051] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0052] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0054] In the description of the present invention, it should be noted that if terms such as "upper", "lower", "left", "right", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0055] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, if terms such as "set", "installed", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] The embodiments of the present invention are achieved through the following technical solutions:

[0057] Embodiment 1

[0058] Please refer to Figures 1 to 9 , this embodiment provides a multi - structure waterproof system for tunnels in high - halite - rock formations, including a circumferential system and a longitudinal system. The circumferential system includes a grouting ring 100, a primary support 200, a first waterproof layer 300, a water - isolating concrete layer 400, a second waterproof layer 500, and a secondary lining 600 arranged in sequence. The longitudinal system includes a water - blocking tenon 700 and a transition section 800. The transition section 800 is arranged at the junction of the halite - rock formation 20 and the non - halite - rock formation 20.

[0059] In the Friendship Tunnel of the China-Laos Railway, halite rock formations 20 have been found at both ends of the cross-border section. The NaCl content in this formation is as high as 80%, with a relatively high purity. The seepage water in the tunnel is weakly salty to extremely salty, which is rare both at home and abroad. The inventor found in the research that objectively, during the concrete pouring process or in the use process of the tunnel concrete structure, invisible micro-cracks or visible cracks and other defects will inevitably occur. These defects provide good channels for the penetration of groundwater. The halite rock formation 20 has three characteristics of "strong solubility, strong corrosiveness, and expansibility" under the action of groundwater. Although the groundwater exposed during the construction process can be grouted and sealed, in terms of the current construction technology level, it is objectively difficult to completely stop the groundwater injection effectively by relying solely on grouting (even chemical grouting), and it is very difficult to achieve no water seepage; more importantly, after the tunnel is completed, the groundwater environment may change. The absence of groundwater activity during the construction process does not mean that there will be no change in the groundwater activity path during the long-term use process. That is, in the presence of water, the halite rock formation 20 will inevitably face phenomena such as dissolution, crystallization, or expansion.

[0060] The inventor found in the research that for the waterproof project in the tunnel, it mainly adopts the form of primary support 200 + waterproof layer + secondary lining 600. Among them, the existing waterproof layers all adopt forms such as waterproof boards or sprayed waterproof coatings. In addition, as disclosed in CN110748359A, a tunnel waterproof and drainage construction process is provided. It improves the waterproof ability by using waterproof concrete for pouring the secondary lining 600 in combination with waterstops and waterproof boards, but it increases the material requirements for the secondary lining 600, including waterproof requirements and support requirements.

[0061] According to the requirements of the durability design code for concrete structures in high-salt formations, the secondary lining 600 structure reaches C50. The inventor found that theory and practice have proved that the higher the concrete grade, the greater the probability of cracks occurring, which just provides a channel for the penetration of groundwater. Accordingly, the inventor provides a multi-structural waterproof system for tunnels in high-halite rock formations. After the primary support 200 is constructed, an additional barrier is added to prevent the groundwater that seeps in through the defects of the primary support 200 and the waterproof board, so that the secondary lining 600 can serve (operate) in a non-wet-dry alternating environment, which can optimize the design grade of the structure, thereby reducing the probability of cracks occurring in high-grade concrete.

[0062] The water-blocking concrete layer 400 is formed by pouring concrete. Compared with ordinary waterproof boards, it has better anti-seepage and anti-crack capabilities. By adding the water-blocking concrete layer 400 to undertake part of the anti-seepage and anti-crack tasks, the design grade of the secondary lining 600 can be optimized, and the original concrete strength requirement of the secondary lining 600 can be reduced. Thereby reducing the probability of cracks occurring in the secondary lining 600 and improving the overall anti-seepage ability. Among them, the tunnel adopts a circular structure end face to enhance the structural resistance.

[0063] Preferably, the concrete strength of the primary support 200, the concrete strength of the water-proof concrete layer 400, and the concrete strength of the secondary lining 600 are set to increase in sequence. After the tunnel construction is completed, it mainly relies on the secondary lining 600 for support ultimately. The concrete strength of the secondary lining 600 should be selected to be greater than that of the primary support 200 to reduce the overall material cost. The concrete strength of the water-proof concrete layer 400 is selected to be between that of the primary support 200 and the secondary lining 600, weighing both the overall material cost and the stability during the construction process. In more practical applications, this is not the only selection method. Following the design concept that the concrete strength of the primary support 200, the concrete strength of the water-proof concrete layer 400, and the concrete strength of the secondary lining 600 increase in sequence, it is mainly based on actual needs.

[0064] Please refer to Figure 3 and Figure 4 , at the bottom of the invert water-proof concrete layer 420, a number of water-blocking tenons 700 are arranged at intervals, and the water-blocking tenons 700 are distributed circumferentially along the tunnel. For example, a water-blocking tenon 700 is arranged every 50 m. Through the water-blocking tenons 700, the free flow of groundwater in the salt rock section is inhibited, making the groundwater in a saturated state, reducing the risk of tunnel bottom corrosion, so as to achieve the purpose of controlling the structural settlement and ensuring the safe use of the structure. By the water-blocking tenons 700, the flow of groundwater near the water-proof concrete layer 400 is blocked, thereby inhibiting the free flow of groundwater longitudinally in the salt rock section and reducing the risk of tunnel bottom corrosion.

[0065] In a preferred implementation manner, the water-blocking tenons 700 are fixed circumferentially along the tunnel at the bottom position of the cast water-proof concrete layer 400. The water-blocking tenons 700 are made of waterproof materials. For example, a concrete material (polymer concrete) consistent with the material of the water-proof concrete layer 400 can be selected to improve the anti-seepage and anti-cracking performance.

[0066] In a preferred implementation manner, the water-blocking tenons 700 are integrally cast with the invert water-proof concrete layer 420 at the same time, simplifying the construction process. This integral casting also means that the water-blocking tenons 700 and the invert water-proof concrete layer 420 are cast with concrete of the same material.

[0067] When the first waterproof layer 300 is provided, the installation of the water-blocking tenons 700 is involved. Specifically, in the excavation section, according to the excavation situation, the location of the tunnel bottom water-blocking tenons 700 needs to be determined through on-site survey. The construction sequence of the water-blocking tenons 700 is as follows: after the tunnel is excavated, the sections near the range of the water-blocking tenons 700 should be promptly constructed with shotcrete with wire mesh and steel grid protection. Note that no steel frame is provided within the range of the water-blocking tenons 700; use a manual pneumatic pick to excavate to the designed cross-section of the water-blocking tenons 700 (deeper into the surrounding rock than the surface of the primary support 200); construct the first waterproof layer 300 between the primary support 200 and the water-proof concrete layer 400 in the sections near the range of the water-blocking tenons 700 (where the geotextile and the waterproof board are not provided within the range of the water-blocking tenons 700); select to cast the water-blocking tenons 700 and the water-proof concrete layer 400 together.

[0068] The multi - structure waterproof system for tunnels in high - salt - content rock salt strata, when applied to the rock salt strata 20, is additionally provided with a transition section 800 design. Specifically, in actual situations, the distribution of the rock salt strata 20 is inconsistent, and there may be a cross - distribution of the rock salt strata 20 and non - salt strata 21. For example, in the rock salt strata 20 where tunnel construction is required, there are various forms such as rock salt strata 20 + non - salt strata 21, rock salt strata 20 + non - salt strata 21 + rock salt strata 20, non - salt strata 21 + rock salt strata 20 + non - salt strata 21, or various combinations of the above several forms.

[0069] It should be avoided to adopt the multi - structure waterproof system for tunnels in high - salt - content rock salt strata provided by this embodiment in the non - salt strata 21. For tunnel construction in the non - salt strata 21, the structure of primary support 200 + secondary lining 600 can be adopted.

[0070] Please refer to Figure 7 , in the present invention, in the junction area between the rock salt strata 20 and the non - salt strata 21, a transition section 800 is set. Preferably, the transition section 800 belongs to the area of the non - salt strata 21, and tunnel construction at the transition section 800 follows the construction system of the rock salt strata 20. Thus, the transition section 800 also has good abilities of preventing groundwater seepage and cracking. Through the transition section 800, the possible water seepage of the non - salt strata 21 to the rock salt strata 20 is weakened, and the intrusion of salt - containing groundwater from the rock salt section to the non - salt section during the transition is weakened.

[0071] The non - salt strata 21 includes a transition section 800 and other non - salt sections, and a stop - end wall is set at the intersection of the transition section 800 and other non - salt sections.

[0072] In summary, the multi - structure waterproof system for tunnels in high - salt - content rock salt strata provided by this embodiment blocks groundwater from entering the structure through an annular system, avoids the erosion of the structure by Cl -, and resists water pressure and the swelling force of rock salt; through the longitudinal system, it inhibits the flow of groundwater and prevents the dissolution of rock salt around the tunnel caused by the structure damage; at the same time, adopting this system can reduce the concrete design grade of the secondary lining structure and avoid the problem of excessive hydration heat and cracks in high - grade concrete.

[0073] Preferably, the grouting ring 100 is for radial grouting around the surrounding rock. Cement slurry materials are mixed with brine, and the grouting pipe includes epoxy - coated steel pipes.

[0074] Use brine to mix the slurry materials for water - stop grouting of the surrounding rock in the rock salt strata 20. It is used to reduce (even prevent) the dissolution of the rock salt strata 20 by the water in the cement slurry. Among them, saturated brine is the best choice for brine.

[0075] The salt rock formation 20 is afraid of water. Especially the flow of water will cause the dissolution to accelerate, so that the tunnel structure will be deformed and damaged. At the same time, the supersaturated salt rock solution will recrystallize, resulting in volume expansion and further crack development. Therefore, the treatment of water is the core issue.

[0076] Since Cl- only corrodes steel bars and does not react with CaO, SiO2, Fe2O3, Al2O3, etc. in cement, saturated brine is used to prepare the grouting material. Not only will the salt rock not be corroded during the grouting process, but it will also promote the shortening of the thickening time of the grouting material. Laboratory tests show that when the salt content is about 26%, the brine reaches the saturation state.

[0077] If the tunnel foundation is continuously dissolved and discharged, solution cavities will surely be formed, leading to foundation settlement and even structural deformation and damage. To ensure the stability of the foundation, the steel pipe grouting process is adopted. To prevent the corrosion of the steel pipe by brine, it needs to be treated with an epoxy coating to form a composite foundation. The epoxy-coated steel pipe grouts and consolidates the tunnel foundation.

[0078] For the obvious water leakage parts on the surface of the initial support 200 of the wall, local radial grouting is adopted to block water and prevent the loss of salt rock. For example, the circumferential spacing of the grouting holes is 1m, the longitudinal spacing is 1m, and they are arranged staggeredly, and the grouting depth is 5m. It should be noted that in the technical solution of this embodiment, it is preferably to grout first and then spray concrete, which is beneficial to the sealing of the initial support 200 and the maintenance of the tunnel in the salt rock formation 20. However, in the case of urgent construction period, it is possible to spray (the initial support 200) concrete first and then grout, which is beneficial to improving the construction speed.

[0079] Preferably, the initial support 200 uses C30 corrosion-resistant early high-strength shotcrete, the water-proof concrete layer 400 uses C35 corrosion-resistant polymer concrete, the secondary lining 600 uses C40 corrosion-resistant impermeable concrete, the water-proof concrete layer 400 is plain concrete, the secondary lining 600 is reinforced concrete, and the steel bars use epoxy-coated steel bars.

[0080] The water-proof concrete layer 400 is formed by pouring plain concrete, and the secondary lining 600 is formed by pouring reinforced concrete. The salt rock formation 20 contains a large amount of halides and sulfate minerals of potassium, sodium, calcium, and magnesium. When reinforced concrete reacts with halides, it will cause the corrosion of steel bars, weaken the performance of steel bars, and the volume of the rust substance generated is larger than the volume of the original steel bars, which will further expand the cracks in the concrete.

[0081] After the entire waterproof system is established, if water in the tunnel surrounding rock may seep into the secondary lining 600, it must first pass through the water-proof concrete layer 400. On the basis of adding the water-proof concrete layer 400, the water-proof concrete layer 400 is cast with plain concrete, and the secondary lining 600 is cast with reinforced concrete. The water-proof concrete layer 400 with a plain concrete structure comes into contact with the brine in the surrounding rock first. The absence of steel bars can enhance the resistance to brine erosion. The secondary lining 600 uses reinforced concrete, which has better mechanical properties and is beneficial to the long-term stability of the overall tunnel.

[0082] The secondary lining 600 is cast with epoxy-coated steel bars, which can prevent the erosion of salt ions, delay corrosion, and has the characteristic of low cost compared with using stainless steel.

[0083] The primary support 200 uses C30 early high-strength shotcrete to improve the early mechanical properties of the primary support 200, which is beneficial to form an effective initial support. The water-proof concrete layer 400 uses C35 polymer concrete, which has high tensile and flexural strengths, good ductility, adhesiveness and impermeability, and is beneficial to the water-proof concrete layer 400's resistance to brine in the surrounding rock. By setting the water-proof concrete layer 400, the groundwater seeping in through the defects of the primary support 200 and the waterproof board is blocked, enabling the secondary lining 600 to serve (operate) in a non-wet-dry alternating environment, which can optimize the design grade of the secondary lining 600 structure. Thus, the secondary lining 600 changes from C50 determined according to the durability design code of concrete structures in the original high-salt formation to a relatively lower C40 concrete strength, reducing the probability of crack generation.

[0084] Moreover, the secondary lining 600 uses C40 corrosion-resistant and impermeable concrete to improve the corrosion resistance and impermeability of the secondary lining 600 concrete, which is beneficial to the long-term stability of the tunnel.

[0085] Preferably, the contour shapes of the water-proof concrete layer 400 and the secondary lining 600 away from the surrounding rock surface are circular. The water-proof concrete layer 400 includes the arch wall water-proof concrete layer 410 at the arch wall and the invert water-proof concrete layer 420 at the tunnel bottom. The thickness of the invert water-proof concrete layer 420 is greater than that of the arch wall water-proof concrete layer 410. The secondary lining 600 includes the arch wall secondary lining 610 at the arch wall and the invert secondary lining 620 at the tunnel bottom. The water-proof concrete layer 400 is one slab every 10m or 12m longitudinally, and the secondary lining 600 is one slab every 10m or 12m longitudinally. The length of each slab of the water-proof concrete layer 400 is the same as that of the secondary lining 600.

[0086] The water-stop concrete layer 400 is cast in two parts separately according to the structural construction method. One is the arch wall water-stop concrete layer 410 located at the arch wall (the side wall and the arch crown of the lining are collectively called the arch wall), and the other is the invert water-stop concrete layer 420 located at the invert position. Since the arch wall water-stop concrete layer 410 mainly aims at preventing the infiltration of brine in the surrounding rock, and the invert water-stop concrete layer 420 is used to slow down the seepage of groundwater at the tunnel bottom, the anti-seepage pressure at the invert water-stop concrete layer 420 is greater than that at the arch wall water-stop concrete layer 410. Therefore, the thickness of the arch wall water-stop concrete layer 410 is designed to be less than that of the invert water-stop concrete layer 420. For example, the thickness of the arch wall water-stop concrete layer 410 is 30 cm, and the thickness of the invert water-stop concrete layer 420 is selected as 100 cm, which is equivalent to thickening the invert water-stop concrete layer 420. The second lining 620 of the tunnel invert is protected by the relatively thick invert water-stop concrete layer 420.

[0087] Preferably, please refer to Figure 8 and Figure 9 , the first longitudinal construction joint 430 between the arch wall water-stop concrete layer 410 and the invert water-stop concrete layer 420 is staggered from the second longitudinal construction joint 630 between the arch wall second lining 610 and the invert second lining 620, and the first circumferential construction joint 440 between the plates of the water-stop concrete layer 400 is staggered from the second circumferential construction joint 640 between the plates of the second lining 600. The embedded rubber waterstops are provided at the first longitudinal construction joint 430, the second longitudinal construction joint 630, the first circumferential construction joint 440, and the second circumferential construction joint 640.

[0088] Preferably, the first waterproof layer 300 includes a first geotextile and an EVA waterproof board laid in a full circle, and the primary support 200, the first geotextile, the EVA waterproof board, and the water-stop concrete layer 400 are arranged in sequence. The second waterproof layer 500 includes an anti-adhesive waterproof board laid in a full circle, and the water-stop concrete layer 400, the anti-adhesive waterproof board, and the second lining 600 are arranged in sequence.

[0089] It can be understood that it is also possible to simply provide a single layer on both sides of the water-stop concrete layer 400 when adding the waterproof layer.

[0090] For the surface of the water-retaining concrete layer 400 away from the surrounding rock, that is, the inner surface, that is, the side close to the secondary lining 600, smooth treatment is carried out in order to obtain a smooth surface. The smooth surface refers to a surface that is smooth, unobstructed and has no concavities or convexities. On the basis of the smooth surface, an anti-adhesive waterproof board is used to form the second waterproof layer 500, which overcomes the defect that the anti-adhesive waterproof board cannot be used due to the uneven surface of the primary support 200 in ordinary tunnels. The anti-adhesive waterproof board has good puncture resistance, and good flame retardancy, durability, water resistance, corrosion resistance, and antibacterial properties. Among them, the water-retaining concrete layer 400, the anti-adhesive waterproof board, and the secondary lining 600 are arranged in sequence. The anti-adhesive waterproof board is different from the ordinary EVA + geotextile form. It has no ordinary waterproof hot-melt washers and no geotextiles. The anti-adhesive waterproof board is directly bonded to the water-retaining concrete layer 400, enhancing the installation efficiency. The anti-adhesive waterproof is integrated with the secondary lining 600 structure through the chemical reaction of pouring, which is equivalent to the skin of the secondary lining 600 structure, effectively improving the adverse situation of the water seepage path formed between the water-retaining concrete layer 400 and the secondary lining 600 due to the waterproof board.

[0091] Specifically, the water-retaining concrete layer 400 includes an arch wall water-retaining concrete layer 410 and an inverted arch water-retaining concrete layer 420. The side wall arch wall water-retaining concrete layer 410 is concreted by a trolley, and has a fully enclosed pouring cavity, and a smooth surface can be obtained.

[0092] Different from conventional tunnels, a water-retaining concrete layer 400 is added. The salt rock section is equivalent to constructing the inverted arch twice, and the curvature and depth are increased. Conventional equipment and processes cannot meet the requirements. To ensure the structural quality and meet the requirements of the process and traffic organization at the same time, (and for the smooth treatment of the inverted arch water-retaining concrete layer 420), a salt rock formation 20 up-type tunnel bottom fully enclosed anti-floating combined device is proposed for concrete pouring. The salt rock formation 20 up-type tunnel bottom fully enclosed anti-floating combined device includes a self-propelled long trestle 900 and a fully enclosed formwork 910.

[0093] Please refer to Figure 5 and Figure 6 where Figure 5 is the cross-sectional view of the tunnel axial view, Figure 6 is the cross-sectional view of the tunnel radial view. The self-propelled long trestle 900 and the fully enclosed formwork 910 are used for concrete pouring of the inverted arch water-retaining concrete layer 420. The fully enclosed formwork 910 is provided with a stop board 911 and an intermediate long formwork 912 distributed along the tunnel axis. The intermediate long formwork 912 is separated from the wall surface of the tunnel operation area by a preset distance. The fully enclosed formwork 910 and the wall surface of the tunnel operation area enclose a concrete pouring area 914. The self-propelled long trestle 900 is used to assist the movement of the intermediate long formwork 912.

[0094] The fully enclosed formwork 910 and the self-propelled long trestle 900 cooperate with each other. The fully enclosed formwork 910 includes a stop board 911 and an intermediate long formwork 912. The intermediate long formwork 912 is distributed along the axial direction of the tunnel. The intermediate long formwork 912 is separated from the wall surface of the tunnel operation area by a preset distance, and this preset distance is set according to the established dimensions pre-researched by the water-proof concrete layer 400. The fully enclosed formwork 910 and the wall surface of the tunnel operation area enclose a concrete area to be poured 914, and concrete is filled in the concrete area to be poured 914 to construct the water-proof concrete layer 400. By adopting the self-propelled long trestle 900, it only needs to be assembled once and moves back and forth by a trolley, which has the beneficial effects of simple operation and reasonable use of space compared with the short trestle. It should be noted that the cooperation between the fully enclosed formwork 910 and the self-propelled long trestle 900 is not limited to the construction of the water-proof concrete layer 400 at the inverted arch, but can also be used for the construction of other inverted arch layers.

[0095] The self-propelled long trestle 900 includes a front approach bridge, a main bridge, a rear approach bridge and a traveling mechanism. One end of the front approach bridge is connected to the front end of the main bridge, and one end of the rear approach bridge is connected to the rear end of the main bridge. The traveling mechanism is used for the movement of the main bridge.

[0096] Preferably, the concrete area to be poured 914 is concreted by the method of pouring into the formwork window by window. The intermediate long formwork 912 is provided with a number of through feeding windows 913 along the distribution plane. Each feeding window 913 is equipped with a channel connected to the main hopper at the top of the trolley. The feeding window 913 is used for the concrete to be poured into the formwork window by window. Each window feeds at the same time, and the feeding speed and quantity are basically the same and uniform, which is convenient for controlling the thickness layering of the concrete during the construction process. Or, when the existing site cannot meet the requirements of feeding all windows at the same time and uniformly, layered symmetric feeding or batch-by-batch feeding can be adopted. Through the cooperation of the fully enclosed formwork 910 and the self-propelled long trestle 900 for pouring, the shape size and construction quality of the pouring structure (the arch wall water-proof concrete layer 410) are ensured, and the self-propelled long trestle 900 is used to meet the parallel flow operation of each process in the tunnel, accelerating the construction progress.

[0097] Preferably, a stop wall is provided at one end of the transition section 800 away from the salt rock formation 20. The stop wall is annularly arranged and is cast integrally with the secondary lining 600 of the transition section 800.

[0098] The above salt rock system is used for the salt rock formation 20. In fact, the construction site conditions are complex, and there will be an alternating situation of salt rock sections and non-salt rock sections along the preset construction direction of the tunnel. Please refer to Figure 8, at this time, a transition section 800 is set in the salt rock system. The transition section 800 is arranged at the junction of the salt rock formation 20 and the adjacent non-salt formation 21, and the transition section 800 is located in the area of the non-salt formation 21. The tunnel structure of the transition section 800 is the same as that of the tunnel structure in the salt rock formation 20. Before pouring the transition section 800, full-ring grouting reinforcement is carried out. After the structure pouring reaches the design strength, backfilling grouting is carried out behind the small-range full-ring structure to achieve blocking the cross-boundary of brine.

[0099] In the arch wall structure area, the arch wall structure area includes 5 processes such as a layer of waterproofing, the arch wall water-proof concrete layer 410, a second layer of waterproofing, the second lining 600 steel bars, and the second lining 600 structure, and operates according to 4 working sections.

[0100] In the technical solution of the embodiment of the present invention, regarding the processes of each working area -

[0101] Excavation process area: The bench method is used for drill and blast excavation, and controlled blasting is implemented to reduce the damage of blasting to the surrounding rock and the influence on the newly poured structure; strictly control the bench length to ensure that the closed-loop distance of the primary support 200 from the heading face is less than 40 m to ensure construction safety; after excavation, the primary support is promptly constructed, and a large manipulator is used to apply wet shotcrete technology to ensure construction quality and improve construction efficiency.

[0102] Grouting area: To avoid the formation of cavities due to the corrosion of the salt rock at the tunnel bottom and improve the bearing capacity of the foundation, for the section with a salt content of less than 50%, radial grouting with steel pipe with holes at the tunnel bottom is used to block water. Around the tunnel bottom, φ42 small pipes (anti-corrosion coating) with a length of 5 m are used, with a spacing of 1 m × 1 m (circumferential × longitudinal), arranged staggeredly to seal the fissures in the surrounding rock; for obvious water leakage parts on the surface of the primary support 200 of the wall, local radial grouting is adopted to block water to prevent the loss of rock salt. The grouting orifices are arranged staggeredly, with a circumferential spacing of 1.0 m and a longitudinal spacing of 1.0 m, and the grouting depth is 5 m.

[0103] Inverted arch process area: Different from conventional tunnels, a water-proof concrete layer 400 is added. In the salt rock section, it is equivalent to constructing the inverted arch twice, and the curvature and depth are increased. Conventional equipment and processes cannot meet the requirements. To ensure the structural quality and meet the requirements of processes and traffic organization at the same time, (and for the smooth treatment of the water-proof concrete layer 420 of the inverted arch), a method of a self-propelled long trestle 900 in cooperation with a fully enclosed formwork 910 is proposed; the inverted arch structure area includes 6 processes such as tunnel bottom grouting, a first layer of waterproofing, the water-proof concrete layer 400, a second layer of waterproofing, the second lining 600 steel bars, and the second lining 600 structure, and operates in 4 working sections. (1) The tunnel bottom grouting and the first waterproof layer 300 working area are located under the front bridge of the self-propelled long trestle 900, and the tunnel bottom grouting and the laying of the first waterproof board are completed at one time; (2) In the water-proof concrete layer 400 working area, the water-proof concrete layer 400 is poured. The moving trolley on the main bridge of the self-propelled long trestle 900 hoists the formwork of the water-proof concrete layer 400 to the water-proof concrete layer 400 working area, fixes the formwork of the water-proof concrete layer 400, pours the concrete and vibrates it, and then cures the concrete with the formwork. After reaching the curing period, the formwork of the water-proof concrete layer 400 is lifted and demoulded for curing; (3) In the second lining 620 working area of the inverted arch, the second waterproof layer 500 is first constructed, the inverted arch steel bars are tied, and then the inverted arch formwork is hoisted into place, the stop board 911 is installed, the concrete is poured and vibrated, and the concrete is cured with the formwork. After reaching the curing period, the inverted arch formwork is lifted and demoulded for curing; (4) In the filling working area, the filling formwork is in place, the stop board 911 is closed, the concrete is poured and vibrated, and cured until it is strong; (5) After the concrete in the filling working area reaches the design strength, the self-propelled long trestle 900 is moved forward to the next cycle position.

[0104] Arch wall structure area: The arch wall structure area includes 5 processes such as a first layer of waterproofing, the arch wall water-proof concrete layer 410, a second layer of waterproofing, the second lining 600 steel bars, and the second lining 600 structure, and operates in 4 working sections.

[0105] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0106] 1. By setting the water-proof concrete layer 400, the groundwater infiltrating through the primary support 200 and the defects of the waterproof board is blocked, so that the second lining 600 serves and operates in a non-wet and dry alternating environment, optimizing the design grade of the concrete strength of the second lining 600 structure, thereby reducing the probability of crack generation and improving the anti-seepage and anti-cracking capabilities;

[0107] 2. The water-proof concrete layer 400 is poured with plain concrete, and the second lining 600 is poured with reinforced concrete, and the overall anti-seepage, anti-corrosion, and anti-cracking effects are good;

[0108] 3. A number of water-blocking tenons 700 are provided to limit the flow range of groundwater, which is beneficial to the long-term anti-seepage of the tunnel inverted arch;

[0109] 4. Through the cooperation of the self-propelled long trestle 900 and the fully enclosed formwork 910, and the smooth treatment of the arch wall water-proof concrete layer 410 by the existing trolley, the second waterproof layer 500 can be partially set with an anti-adhesive waterproof board, which has the advantages of good flame retardancy, durability, water resistance, corrosion resistance and antibacterial property;

[0110] 5. The cooperation of the self-propelled long trestle 900 and the fully enclosed formwork 910 can ensure the shape size and construction quality of the arch wall water-proof concrete layer 410 and enable precise construction;

[0111] 6. A transition section 800 is provided at the junction of the salt rock formation 20 and the non-salt formation 21 to weaken the intrusion of the salt-containing groundwater in the salt rock section into the non-salt section during the transition from the salt rock section to the non-salt section;

[0112] 7. The secondary lining 600 is poured with epoxy-coated steel bars, which can prevent the erosion of salt ions, delay corrosion, and has the characteristic of low cost compared with the use of stainless steel materials.

[0113] Example 2

[0114] This example provides a mix proportion of C30 early high-strength shotcrete. Preferably, this example proposes a new C30 early high-strength shotcrete to cope with the environment of the salt rock formation 20. The mix proportion of the C30 early high-strength shotcrete includes the following components by weight fraction: 352 parts of cement, 118 parts of enhanced admixture, 855 parts of sand, 790 parts of crushed stone, 8.46 parts of water reducing agent, 2.35 parts of air-entraining agent, 56.4 parts of preservative, 23.5 parts of accelerating agent, and 118 parts of water. Among them, the enhanced admixture includes the following components by weight fraction: 20 - 25 parts of silica fume, 20 - 25 parts of fly ash, 10 - 15 parts of modified nano-material, and 7 - 10 parts of nano-carbon fiber. Among them, the modified nano-material includes modified nano-CaCO3 and modified nano-TiO2, and the ratio of modified nano-CaCO3:modified nano-TiO2 = 1:0.5 - 2.

[0115] The early high-strength shotcrete provided in this example introduces enhanced admixtures on the basis of traditional concrete, mainly introducing nano-carbon fiber and modified nano-materials; these nano-materials have extremely small sizes and can quickly fill the gaps in the concrete, increasing the packing density of the paste material, reducing the porosity, making the concrete more dense, alleviating the chloride ion penetration in the early stage of the concrete, and effectively improving the impermeability of the concrete.

[0116] The introduced carbon nanofibers are intertwined vertically and horizontally in the hydration products of concrete, overlapping with each other to form a three-dimensional network structure, which can improve the integrity of concrete. Moreover, the carbon nanofibers are distributed in the C-S-H gel, and the single fiber filaments are wrapped by C-S-H gel particles, playing the role of molecular chains, enhancing the toughness and integrity of the gel body, thereby improving the crack resistance of concrete. In addition, the carbon nanofibers can also bridge the microvoids and microcracks inside the concrete, effectively preventing the further development of microcracks and further promoting the crack resistance performance of concrete.

[0117] The nano-TiO2 and nano-CaCO3 were modified, which can effectively avoid the combination of nano-TiO2 and nano-CaCO3 with a large number of water molecules during the mixing process with water, making the hydration of cement more thorough, improving the compressive strength and elastic modulus of concrete, and greatly enhancing its weather resistance and dispersibility. At the same time, the modified nano-materials are more evenly dispersed when blended with the matrix, better increasing the compactness of the concrete structure, thereby better resisting chloride ion diffusion and resisting chloride salt and sulfate erosion, improving the compactness of shotcrete, and thus improving the impermeability and anti-corrosion performance of concrete.

[0118] Experimental method: The GB / T-50080-2016 "Standard Test Method for Properties of Ordinary Concrete Mixtures", GB / T-50081-2019 "Acceptance Standard for Construction Quality of Railway Concrete Engineering", GB / T-50082-2009 "Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete" and TB-10424-2018 "Acceptance Standard for Construction Quality of Railway Concrete Engineering" were used to measure the concrete strength, electric flux and chloride ion diffusion coefficient.

[0119] The technical indexes of the C30 early high-strength shotcrete in this example are compared with those of ordinary shotcrete as shown in the following table:

[0120]

[0121] Through the comparison of the above technical index parameters, the C30 early high-strength shotcrete has the following advantages: the concrete is denser, the concrete rebound rate is small, and the impermeability performance is better; the initial setting time of the concrete is fast, the early strength is higher, and the purpose of safe and rapid support can be achieved; the later strength growth is more guaranteed, the electric flux is smaller, and the total alkali content and sulfur trioxide content are smaller.

[0122] Example 3

[0123] This embodiment provides a C35 polymer concrete to cope with the environment of the salt rock formation 20. The mix proportion of the C35 polymer concrete includes the following components in weight ratio: 308 parts of cement, 88 parts of fly ash, 44 parts of expansive agent, 44 parts of polymer emulsion, 736 parts of sand, 1017 parts of crushed stone, 5.28 parts of water reducing agent, 120 parts of water, and 1.23 parts of defoaming agent; wherein the polymer emulsion includes at least one of styrene-acrylic emulsion, acrylic emulsion, SBR latex, and acrylate.

[0124] In the present invention, the polymer emulsion can increase the flexural and tensile strength of the cement-based cementitious material; improve the impermeability and corrosion resistance of the bonded modified cement-based cementitious material to water, oil substances, and carbon dioxide, as well as the ability to resist the erosion and damage of other chemical substances. In addition, a blend treatment of multiple polymer emulsions can be adopted. Compared with using a single polymer emulsion, the modification effect on the cement-based cementitious material is better, which can enhance the mechanical properties of the blended latex, improve the mechanical properties of the cement mortar, and the chloride ion diffusion coefficient.

[0125] The impermeable and waterproof concrete prepared by the present invention has good impermeable and waterproof effects, thus effectively inhibiting the infiltration of chloride salts, delaying the corrosion of the concrete, and extending the service life of the concrete.

[0126] In the present invention, the defoaming agent is TYXP defoaming agent. The expansive agent is TYZY high-efficiency expansive agent. The cement is selected as low-heat cement.

[0127] A hydraulic cementitious material with low heat of hydration, which is made by grinding appropriate components of Portland cement clinker with an appropriate amount of gypsum, is abbreviated as low-heat cement, also known as high belite cement, and its code is P·LH. Low-heat Portland cement is a kind of cement with dicalcium silicate as the dominant mineral and a relatively low content of tricalcium aluminate. The production of this type of cement has the characteristics of low energy consumption and less harmful gas emissions. Through a large number of studies and experiments, it has been confirmed that this type of cement has advantages that cannot be compared with ordinary Portland cement, such as good workability, low heat of hydration, high late strength, high durability, and high corrosion resistance. When pouring concrete, due to the low heat of hydration, the generation of concrete cracks can be reduced.

[0128] In the present invention, the sand particle size range is 0.15 - 4.75 mm. The particle size of the crushed stone is 2.36 - 31.5 mm, and the continuous grading method is adopted. Specifically, 20% of 5 - 10 mm is incorporated, 50% of 10 - 20 mm is incorporated, and 30% of 16 - 31.5 mm is incorporated.

[0129] Experimental method: The strength, electric flux, and chloride ion diffusion coefficient of concrete were determined using GB / T - 50080 - 2016 "Standard Test Method for Properties of Ordinary Concrete Mixtures", GB / T - 50081 - 2019 "Acceptance Criteria for Construction Quality of Railway Concrete Engineering", GB / T - 50082 - 2009 "Standard Test Method for Long - term and Durability Properties of Ordinary Concrete", and TB - 10424 - 2018 "Acceptance Criteria for Construction Quality of Railway Concrete Engineering".

[0130] The technical indicators of C35 polymer concrete and C35 ordinary concrete in this embodiment are compared as follows:

[0131]

[0132] By comparing ordinary C35 concrete and polymer C35 concrete, the modification effect of polymer emulsion on concrete is mainly achieved by forming a film layer with high bonding strength between cement paste and aggregates, and then blocking the pores in the mortar. Therefore, polymer C35 concrete is denser and has better impermeability performance. However, under the condition of the same amount of cementitious materials, the early strength of ordinary C35 concrete is significantly higher than that of polymer C35 concrete, indicating that the early hydration rate in polymer C35 concrete is lower, the generated hydration heat is also lower, reducing the possibility of temperature crack generation, but the later strength is similar to that of ordinary C35. The chloride ion diffusion coefficient (56d) index of ordinary C35 concrete is much lower than the design requirement, and the electric flux data is also significantly inferior to that of polymer C35 concrete.

[0133] Example 4

[0134] This embodiment provides a C40 corrosion - resistant and impermeable concrete for tunnel construction in a salt rock formation 20. Its mix proportion includes the following components by weight ratio: 255 parts of cement, 42 parts of expansive agent, 746 parts of sand, 1029 parts of gravel, 6.38 parts of water - reducing agent, 0.58 parts of air - entraining agent, and 150 parts of water.

[0135] In the present invention, low - heat cement is selected for the cement. Due to the low hydration heat during concrete pouring, it can reduce the generation of concrete cracks.

[0136] Experimental method: The strength, electric flux, and chloride ion diffusion coefficient of concrete were determined using GB / T - 50080 - 2016 "Standard Test Method for Properties of Ordinary Concrete Mixtures", GB / T - 50081 - 2019 "Acceptance Criteria for Construction Quality of Railway Concrete Engineering", GB / T - 50082 - 2009 "Standard Test Method for Long - term and Durability Properties of Ordinary Concrete", and TB - 10424 - 2018 "Acceptance Criteria for Construction Quality of Railway Concrete Engineering".

[0137] The technical index comparison between ordinary C40 concrete and the C40 corrosion-resistant and impermeable concrete of this embodiment is shown in the following table:

[0138]

[0139] Through the comparison of the above technical index parameters, compared with ordinary C40 concrete, the C40 corrosion-resistant and impermeable concrete has the following advantages: due to the use of low-heat cement and expansion agent, the early strength is low, the hydration heat is reduced, and the generation of temperature cracks is reduced; the late strength growth is obvious, and the addition of the expansion agent reduces the shrinkage of the concrete, and there are obvious improvements and enhancements in durability indexes such as impermeability, chloride ion diffusion, and sulfate erosion resistance; while the durability indexes of ordinary C40 concrete are relatively lower. Through the comparison data, it is found that the chloride ion diffusion coefficient (56d) index of ordinary C40 concrete fails to meet the design requirements, and at the same time, the electric flux data is also inferior to that of the C40 corrosion-resistant and impermeable concrete.

[0140] Example 5

[0141] Please refer to Figure 10 , a multi-structure waterproof technology for tunnels in high halite rock formations. According to the multi-structure waterproof system for tunnels in high halite rock formations in Example 1, a construction technology is provided.

[0142] Specifically, it includes the following steps: S1, the operation of the primary support 200; S2, the pouring of the inverted arch water-proof concrete layer 420; S3, the pouring of the structural concrete of the secondary lining 600 at the inverted arch; S4, the pouring of the filling layer of the inverted arch secondary lining 620; S5, the pouring of the arch wall water-proof concrete layer 410; S6, the pouring of the concrete of the secondary lining 600 at the arch wall.

[0143] Through the above steps, the construction of the primary support 200, the water-proof concrete layer 400 (including separate construction at the inverted arch and the arch wall), and the secondary lining 600 is reasonably arranged to meet the actual construction requirements.

[0144] Preferably, it involves the installation of the first waterproof layer 300 and the anti-adhesive waterproof board. Under the above steps, a new technology is proposed, which specifically includes: construction preparation; grouting the surrounding rock to stop water; the operation of the primary support 200; grouting operation; hanging the EVA waterproof board at the primary support 200 of the inverted arch; pouring the inverted arch water-proof concrete layer 420; laying the anti-adhesive waterproof board on the inverted arch water-proof concrete layer 420; pouring the structural concrete of the secondary lining 600 at the inverted arch; pouring the filling layer of the inverted arch secondary lining 620; hanging the EVA waterproof board at the arch wall; pouring the arch wall water-proof concrete layer 410; laying the anti-adhesive waterproof board at the arch wall water-proof concrete layer 410; pouring the concrete of the secondary lining 600 at the arch wall; concrete curing.

[0145] And it also involves the installation of the water-blocking tenon 700 and the installation of the transition section 800.

[0146] The water-blocking tenons 700 are arranged at intervals at the bottom of the inverted-arch water-proof concrete layer 420. If they are arranged at an interval of 50 m, when using the 12-m long intermediate long formwork 912 for pouring the inverted-arch water-proof concrete layer 420, one water-blocking tenon 700 will be installed only every three or so intermediate long formworks 912. The water-blocking tenons 700 are cast with the same concrete as the water-proof concrete layer 400 and are cast simultaneously.

[0147] Regarding the transition section 800, it will be set only at the junction of the salt rock formation 20 and the non-salt formation 21. Among them, according to the construction concept of first bottom then top in the lining construction, when the construction of the transition section 800 is required, the casting of the end wall of the transition section 800 is carried out between the pouring of the filling layer of the S8 inverted-arch secondary lining 620 and the hanging of the EVA waterproof board at the S9 arch wall.

[0148] The construction organization sequence adopted in this process is: from bottom (inverted arch) to top (side and top arch), from outside (surrounding rock side) to inside (tunnel center line), with the lower structure in advance and the upper structure coordinated for follow-up.

[0149] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi - structure waterproofing system for tunnels in high - salt rock formations, characterized in that: It includes an annular system and a longitudinal system. The annular system includes a grouting ring, a primary support, a first waterproof layer, a water-blocking concrete layer, a second waterproof layer, and a secondary lining arranged in sequence. The longitudinal system includes a water-blocking tenon and a transition section. The transition section is arranged at the junction of the rock salt formation and the non-rock salt formation. The primary support uses C30 corrosion-resistant early high-strength shotcrete. The water-blocking concrete layer uses C35 corrosion-resistant polymer concrete. The secondary lining uses C40 corrosion-resistant impermeable concrete. The water-blocking concrete layer is plain concrete, and the secondary lining is reinforced concrete. The steel bars use epoxy-coated steel bars. The water-blocking tenon is arranged at the bottom of the invert water-blocking concrete layer and is spaced longitudinally along the tunnel. The upper end surface of the water-blocking tenon is in contact with the bottom surface of the invert water-blocking concrete layer. The tenon body of the water-blocking tenon penetrates through the primary support and is distributed. The water-blocking tenon and the invert water-blocking concrete layer are configured to be cast integrally at the same time. The transition section has a longitudinal preset length along the tunnel axis. The transition section is arranged in the area of the non-salt formation. The tunnel structure of the transition section is the same as that of the tunnel in the rock salt formation. A stop wall is provided at one end of the transition section away from the rock salt formation. The stop wall is arranged in a ring shape and is cast integrally with the secondary lining of the transition section.

2. The multi-structural waterproofing system for tunnels in highly saline rock formations according to claim 1, wherein: The grouting ring is for radial grouting around the surrounding rock. Cement slurry materials are mixed with brine. The grouting pipe includes an epoxy-coated steel pipe.

3. The multi-structure waterproof system for tunnels in high-salt rock formations according to claim 1, characterized in that: The mix proportion of the C30 corrosion-resistant early high-strength shotcrete includes the following components by weight fraction: 352 parts of cement, 118 parts of enhanced admixture, 855 parts of sand, 790 parts of crushed stone, 8.46 parts of water reducer, 2.35 parts of air-entraining agent, 56.4 parts of preservative, 23.5 parts of accelerating agent, and 118 parts of water. Among them, the enhanced admixture includes the following components by weight fraction: 20 - 25 parts of silica fume, 20 - 25 parts of fly ash, 10 - 15 parts of modified nano material, and 7 - 10 parts of nano carbon fiber. Among them, the modified nano material includes modified nano CaCO3 and modified nano TiO2, and the ratio of modified nano CaCO3:modified nano TiO2 = 1:0.5 - 2.

4. The multi-structure waterproof system for tunnels in high-salt rock formations according to claim 1, characterized in that: The mix proportion of the C35 corrosion-resistant polymer concrete includes the following components by weight ratio: 308 parts of cement, 88 parts of fly ash, 44 parts of expansive agent, 44 parts of polymer emulsion, 736 parts of sand, 1017 parts of crushed stone, 5.28 parts of water reducer, 120 parts of water, and 1.23 parts of defoaming agent. Among them, the polymer emulsion includes at least one of styrene-acrylic emulsion, acrylic emulsion, SBR latex, and acrylate.

5. The multi - structure waterproofing system for tunnels in highly saline rock formations according to claim 1, characterized in that: The mix proportion of the C40 corrosion-resistant impermeable concrete includes the following components by weight ratio: 255 parts of cement, 42 parts of expansive agent, 746 parts of sand, 1029 parts of sand and gravel, 6.38 parts of water reducer, 0.58 parts of air-entraining agent, and 150 parts of water.

6. The multi - structure waterproofing system for tunnels in high - salinity rock formations according to claim 1, wherein: The contour shapes of the water - isolating concrete layer and the secondary lining away from the surrounding rock surface are circular. The water - isolating concrete layer includes the arch - wall water - isolating concrete layer at the arch - wall and the invert water - isolating concrete layer at the tunnel bottom. The thickness of the invert water - isolating concrete layer is greater than that of the arch - wall water - isolating concrete layer. The secondary lining includes the arch - wall secondary lining at the arch - wall and the invert secondary lining at the tunnel bottom. The water - isolating concrete layer is in one slab every 10m or 12m longitudinally, and the secondary lining is in one slab every 10m or 12m longitudinally. The length of each slab of the water - isolating concrete layer is the same as that of the secondary lining.

7. The multi-structure waterproofing system for tunnels in high-salt rock formations according to claim 6, characterized in that: The first longitudinal construction joint between the arch - wall water - isolating concrete layer and the invert water - isolating concrete layer is staggered from the second longitudinal construction joint between the arch - wall secondary lining and the invert secondary lining. The first circumferential construction joint between the slabs of the water - isolating concrete layer is staggered from the second circumferential construction joint between the slabs of the secondary lining. The first longitudinal construction joint, the second longitudinal construction joint, the first circumferential construction joint, and the second circumferential construction joint are all provided with embedded rubber waterstops.

8. The multi - layer structure waterproofing system for tunnels in high - salt rock formations according to claim 1, characterized in that: The first waterproof layer includes laying the first geotextile and EVA waterproof board in a full - circle manner. The primary support, the first geotextile, the EVA waterproof board, and the water - isolating concrete layer are arranged in sequence. The second waterproof layer includes laying the self - adhering waterproof board in a full - circle manner. The water - isolating concrete layer, the self - adhering waterproof board, and the secondary lining are arranged in sequence.

9. A waterproofing process for the multi - structure waterproofing system of high - salinity rock - formation tunnels described in any one of claims 1 - 8, characterized in that, It includes the following steps: S1, primary support operation; S2, pouring the invert water - isolating concrete layer; S3, pouring the concrete of the secondary lining structure at the invert; S4, pouring the filling layer of the invert secondary lining; S5, pouring the arch - wall water - isolating concrete layer; S6, pouring the concrete of the secondary lining at the arch - wall.

10. The waterproofing process of the multi - layer structure waterproofing system for tunnels in high - salt rock formations according to claim 9, characterized in that: Before step S1, construction preparation is also carried out, and grouting for water - stop is carried out; Between step S1 and step S2, grouting operation and hanging the EVA waterproof board at the primary support of the invert are also carried out in sequence; Between step S2 and step S3, laying the self - adhering waterproof board on the invert water - isolating concrete layer is also carried out; Between step S4 and step S5, hanging the EVA waterproof board at the arch - wall is also carried out; Between step S5 and step S6, laying the self - adhering waterproof board at the arch - wall water - isolating concrete layer is also carried out; After step S6, concrete curing is also carried out.

11. The waterproofing process of the multi - structure waterproofing system for tunnels in highly saline rock formations according to claim 9, characterized in that: When the area to be constructed needs to pass through a non - salt area from a salt rock area and enter the next salt rock area, construction at both ends of the non - salt area on the construction path is carried out according to steps S1 - S6.

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