Construction method for comprehensive treatment of water gushing collapse of water-rich loess tunnel

Abstract

This invention discloses a construction method, specifically a method for the comprehensive treatment of water inrush and collapse in water-rich loess tunnels, belonging to the technical field of tunnel engineering collapse and water inrush treatment technology. It provides a construction method for the comprehensive treatment of water inrush and collapse in water-rich loess tunnels with significantly shortened construction time and effectively guaranteed treatment quality. This method first rapidly lowers the groundwater level, cuts off water hazard channels, and prevents continuous softening and collapse of the surrounding rock through multi-stage disaster control and drainage measures of interception, guidance, and drainage. Then, it employs an integrated high-rigidity temporary support system of arch protection, horizontal bracing, timber stacking, and counter-pressure to form a circumferential high-rigidity, vertically strong bearing, and overall closed-loop support system behind the water-rush and collapsed tunnel. Finally, it uses a composite curtain grouting construction process of double-stop grouting walls and collapse cavity backfilling to achieve the dense consolidation of loose collapsed material, the sealing of large-volume water inrush, and the filling of the arch collapse cavity, forming an overall reinforcement of the tunnel curtain and improving the strength and impermeability of the surrounding rock.

Description

Technical Field

[0001] This invention relates to a construction method, and more particularly to a construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels, belonging to the technical field of tunnel engineering collapse and water inrush treatment technology. Background Technology

[0002] When loess tunnels pass through water-rich strata, the loess is prone to sudden water inrush, mud inrush, large-scale flow-plastic collapse at the tunnel face, formation of large cavities in the arch, deformation and cracking of the initial support, and slippage of the sidewalls due to the well-developed vertical joints, loose structure, softening and disintegration of the loess when exposed to water, and extremely poor self-stability. Under the coupled effects of high groundwater pressure, large flow, construction disturbance, and stress redistribution, these tunnels are highly susceptible to sudden water inrush, mudslide, large-scale flow-plastic collapse at the tunnel face, formation of large cavities in the arch, deformation and cracking of the initial support, and slippage of the sidewalls. This can lead to a chain of disasters such as secondary collapse, continuous water inrush, slippage of the collapsed body, and settlement of the tunnel roof, posing a fatal threat to personnel safety and the overall stability of the project.

[0003] The commonly used temporary support methods after a collapse of a loess tunnel mainly include the following categories: 1. Weak drainage system and delayed disaster control: Most of the drainage systems are simple pumping systems without graded water collection, reverse filtration and seepage prevention, or dynamic flow regulation. They are unable to cope with large water inrushes of 6,000 m³ / d, resulting in continuous water damage, repeated softening of surrounding rock, and continuous expansion of the collapse area.

[0004] 2. Temporary supports are not stiff enough and have poor overall integrity: They are mostly scattered steel pipes, square timber, and local steel arch frames. They are not in a ring, have no horizontal bracing, no vertical support, weak resistance to lateral pressure, and poor resistance to deformation. They cannot resist the large lateral pressure of loess and are very prone to secondary collapse, sidewall slippage, and arch sinking.

[0005] 3. Limited, low-precision, and insufficient-frequency advanced detection: Relying solely on simple geological radar or short-range drilling cannot accurately locate collapsed cavities, water-rich areas, and weak interlayers, leading to blind grouting, uneven reinforcement, blind spots, and uncontrollable risks.

[0006] 4. The curtain grouting process is simple, the grouting is poor, and the consolidation is uneven: it mostly adopts a single backward grouting method, without sequence, without cavity backfilling, and without double grouting walls. The grout leakage is serious, the grouting pressure is insufficient, there are cavities, the reinforcement range is insufficient, the water inflow is poorly sealed, and it is impossible to consolidate the fluid-like collapsed body.

[0007] 5. Weak support parameters and poor long-term stability: The steel arch frame spacing is large, the locking feet are short, the secondary lining is thin, and the drainage is weak. The strength of the surrounding rock after grouting is limited, and it is prone to deformation, cracking, and erosion, resulting in insufficient long-term stability.

[0008] The invention disclosed in CN202011181632.4 is a method for treating tunnel collapses using a combination of pipe roof and pre-drilled small-diameter pipe grouting. The method includes the following steps: 1. Repairing the collapsed section; 2. Sealing the tunnel face; 3. Consolidating the collapsed section; 4. Long pipe roof grouting; 5. Double-layer pre-drilled small-diameter pipe grouting; 6. Excavation and treatment of the collapsed section. This invention, by combining long pipe roof and double-layer pre-drilled small-diameter pipe grouting, and by effectively cycling shotcrete, longitudinal grouting of small-diameter pipes, and double-layer pre-drilled small-diameter pipe grouting according to the excavation length, can further improve tunnel construction safety. While reinforcing the collapsed section as a whole, it can also reinforce the section under construction at short distances, preventing further disturbance from nearby construction. This method saves costs while effectively improving construction safety and efficiency. However, it has the following drawbacks: 1. It lacks a graded drainage system, making it unable to cope with large water inflows of 6000 m³ / d, leading to continuous softening of the surrounding rock; 2. The temporary support is weak, relying solely on pipe roofs and small guide pipes, which do not form a ring or provide vertical support, resulting in poor resistance to lateral pressure; 3. The grouting process is simplistic, lacking double grout-stopping walls and a three-sequence three-process approach, making it prone to grout leakage and uneven consolidation; 4. It lacks advanced and precise detection, leading to blind construction and uncontrollable risks. This invention integrates five core elements: advanced detection, graded drainage, high-rigidity temporary support, composite curtain grouting, and support reinforcement. It forms a closed-loop treatment for extreme conditions such as large water inflows in water-rich loess, fluidized bed collapses, and large cavities. In contrast, the patent only focuses on single advanced reinforcement and cannot adapt to the extreme conditions of this project. Patent CN202210737543.6 discloses a construction method for treating tunnel roof collapses at reverse exit, utilizing the slag at the roof collapse site to construct a slope from the tunnel to the surface of the roof collapse site. The slope is used for personnel and machinery passage. This invention creatively utilizes the slope constructed from the collapsed debris, allowing personnel and machinery to quickly reach the surface. It eliminates the need for small pilot tunnels located within the collapsed debris, which previously required manual labor. The entire construction process can now be carried out using large machinery, ensuring high safety. It also eliminates the traditional methods of grouting the collapsed debris and reinforcing the surrounding rock, as well as the need for advanced support, small pilot tunnels, and sidewall supports, significantly reducing project costs. For example, in a 20m collapse, traditional methods require at least three months for reinforcement and the establishment of a small pilot tunnel. This method is simple, safe, cost-effective, fast, and efficient. However, it has the following drawbacks: 1. It completely ignores drainage, making construction impossible under conditions of high water inflow, leading to continuous rock slippage; 2. Without temporary support, relying solely on the collapsed debris results in extremely poor stability and a high risk of secondary collapse; 3. Without grouting reinforcement, the collapsed material is loose, leading to poor long-term stability; 4. It is only suitable for shallow, small collapses and not for deep burial, high water pressure, large water inflow, or large cavities. This invention addresses extreme working conditions such as deep burial (152~156m), high water pressure, large water inrush of 6000m³ / d, fluidized bed collapse, and large cavity collapse, by constructing a five-core integrated system. In contrast, the patent is only applicable to shallow burial and small collapse, and the technical approach is completely different, with significant differences in adaptability.

[0009] The technical solutions of the two patents mentioned above only focus on a single process or local reinforcement, and have not formed an integrated treatment system that combines advanced detection, graded drainage, temporary support, composite curtain grouting, and support parameter enhancement. Furthermore, neither of them can be adapted to the extreme working conditions of this project, such as deep burial, high water pressure, 6000m³ / d large water inflow, fluidized bed collapse, and large cavity collapse. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a construction method for the comprehensive treatment of water inrush and collapse in water-rich loess tunnels that significantly shortens the construction cycle and effectively ensures the treatment quality.

[0011] The technical solution adopted to solve the above-mentioned technical problems is a construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels. The method involves first rapidly lowering the groundwater level, cutting off water hazard channels, and preventing continuous softening and collapse of the surrounding rock through multi-stage interception, guidance, and drainage measures. Then, an integrated high-rigidity temporary support system consisting of arch protection, horizontal bracing, timber stacks, and counter-pressure is used to form a circumferential high-rigidity, vertically strong bearing, and overall closed-loop support system behind the water-rush and collapsed tunnel. Finally, a composite curtain grouting construction process of double-layer grout-stopping walls and cavity backfilling is employed to achieve the compaction and consolidation of the loose collapsed body, the sealing of large-volume water inrush, and the filling of the arch cavity. This results in overall reinforcement of the tunnel curtain and improvement of the surrounding rock strength and impermeability, thus completing the comprehensive treatment of water inrush and collapse in water-rich loess tunnels. Among them, when carrying out the double grout stop wall sealing and cavity backfilling construction, a three-process composite grouting construction technology is adopted, which is B→D→A three-sequence zonal grouting + forward segmented grouting - drill rod retraction segmented grouting - bundled sleeve valve pipe grouting.

[0012] Furthermore, before implementing multi-level disaster control and drainage measures, a precise advance detection was conducted in front of the water-bearing and collapsed tunnel to obtain the precise location of the collapsed cavity, water-rich channels, weak interlayers, and loose bodies within a 50m range before and after the collapsed section. This provided a basis for the dynamic adjustment of subsequent grouting hole locations, grouting pressure, and grout mix ratio.

[0013] The preferred approach to the above scheme is to conduct advanced and precise detection after dredging, using a combined detection process of geological survey, HSP acoustic reflection, ground-penetrating radar, and advanced drilling.

[0014] Furthermore, after the composite curtain grouting is completed, the support parameters need to be comprehensively strengthened by increasing density, thickness, strong locking, and superior waterproofing to significantly improve the load-bearing capacity, rigidity, and durability of the integrated treatment structure and ensure the long-term safety and stability of the tunnel.

[0015] The preferred method of the above scheme is as follows: the densification construction uses steel arch frames made of I22a I-beams, with a spacing of 50cm between adjacent sets of steel arch frames; the thickening construction uses 60cm thick C30 reinforced concrete for secondary lining; the strong locking foot uses locking foot anchor pipes, which are welded together as a whole by φ89×6mm-6m wall foot, φ60×5mm-4m wall waist and φ60×5mm-3m arch foot; the superior waterproofing uses a full-coverage of 1.5mm EVA convex shell waterproof board + 20KN / m non-woven fabric + horizontal drainage pipes with a spacing of 4m for optimized waterproofing and drainage construction.

[0016] Furthermore, the multi-stage disaster control and drainage measures of interception-diversion-drainage include downstream water collection, diversion and seepage prevention, and graded pumping. During downstream water collection, a 2.0m×1.4m water collection well is set up downstream of the collapse section to collect the gushing water and serve as a permanent seepage ditch inspection well for later use. During diversion and seepage prevention, a φ500mm PE steel corrugated pipe is used to divert the gushing water, and a 20cm gravel filter layer + double-layer permeable geotextile is installed at the pipe opening to prevent silt blockage. During graded pumping, a 37kW fixed pump + a 7.5kW mobile pump are deployed in the tunnel, with a maximum drainage capacity of ≥6000m³ / d, and a stable capacity of 3400m³ / d during the stable period.

[0017] The preferred method of the above scheme is to first perform the counter-pressure closure of the normal surface before implementing the integrated high-rigidity temporary support of arch protection + cross bracing + timber stack + counter-pressure. Specifically, φ8×20cm steel mesh is first laid on the collapsed body after dredging, then 12cm thick C25 concrete is sprayed, and finally sandbags are stacked on the outside to counter-pressure the slope to prevent the collapsed body from sliding.

[0018] Furthermore, the integrated high-rigidity temporary support system, consisting of arch support, horizontal bracing, timber piers, and counterweight, includes an I22a I-beam temporary arch support in front of the grout-stopping wall, anchorage at the arch foot and sidewall, horizontal bracing of the arch support, and horizontal timber pier reinforcement. The specific process involves... I22a I-beam temporary arch supports are installed in a 7m section in front of the grout-stopping wall, with I22a I-beams arranged in a full ring at 80cm longitudinal spacing and connected by φ22 steel bars in the circumference. Two φ60×5mm anchor pipes (L=4m) are installed at the arch foot and side wall, and are obliquely anchored into the rock. I22a I-beam horizontal bracing is installed between the arch supports, forming a closed ring to create an overall load-bearing system. Two 2m×2m solid wood horizontal stacks are symmetrically installed laterally, with a longitudinal net distance of 0.5m, fixed with horseshoe nails and wedges, and the bottom rests on a solid foundation to directly transfer the load of the arch. 28cm thick C25 concrete is sprayed on the outside of the temporary arch supports and horizontal bracing to improve the overall rigidity.

[0019] The preferred method of the above scheme is a composite curtain grouting of double grout-stopping wall sealing + cavity backfilling, which includes a double grout-stopping wall sealing with 2m thick C30 concrete grout-stopping wall at both the upstream and downstream sides and a double grout-stopping wall with φ22 double-layer steel mesh inside, and a secondary supplementary grouting to fill the cavity with fly ash pumped through φ108 pipe roof to the cavity at the top of the arch, to ensure that the cavity is dense.

[0020] Furthermore, the three-process composite grouting construction, consisting of B→D→A three-sequence zone grouting + forward segmented grouting - drill pipe retraction segmented grouting - bundled sleeve valve grouting, is carried out according to the following steps. Forward-moving segmented grouting involves drilling in 3-5m sections, using high-pressure air drilling, skip-hole coarse reinforcement, and sealing large voids; backward-moving segmented grouting involves drilling to the designed depth and then retracting to perform segmented grouting for mid-to-deep dense reinforcement; bundled sleeve valve grouting uses φ42×4mm sleeve valve bundles to reinforce weak areas and eliminate blind spots; the grout and parameter requirements are cement-water glass double-liquid grout with W:C=0.8-1:1 and C:S=1:1, grouting pressure 2.0-4.0MPa, diffusion radius 2m, and final hole spacing 2-3.5m; the grouting completion standard is 5-10 minutes after pressure stabilization or when the grout volume reaches 1.5 times the design value, to form a dense consolidation of loose collapsed bodies, seal large-flow water inflows, fill the arch collapse cavity, and provide overall curtain reinforcement, thereby improving the strength and impermeability of the surrounding rock.

[0021] The beneficial effects of this invention are as follows: The construction method provided in this application first rapidly lowers the groundwater level, cuts off water hazard channels, and prevents the surrounding rock from continuously softening and collapsing through multi-stage disaster control and drainage measures of interception, guidance, and drainage. Then, an integrated high-rigidity temporary support method of arch protection + horizontal bracing + timber stacking + counterpressure is used to form a circumferential high-rigidity + vertical high-bearing + overall closed-loop support system behind the water-bearing and collapsed tunnel. Finally, a composite curtain grouting construction process of double grout-stopping wall sealing + collapse cavity backfilling is adopted to achieve the dense consolidation of loose collapsed body, the sealing of large-flow water inflow, and the filling of the arch collapse cavity, forming an overall reinforcement of the tunnel curtain and improving the strength and impermeability of the surrounding rock, thus completing the comprehensive treatment of water-bearing and collapsed tunnels in water-rich loess. This effectively solves the treatment failure problem of using a single treatment measure in the prior art. The above-mentioned construction method of this application can achieve the purpose of rapid water control, temporary collapse stabilization, and consolidation and water blocking, thereby significantly shortening the construction cycle and effectively ensuring the treatment quality. The above-mentioned technical solution of this application is particularly suitable for the treatment of tunnel collapse sections in typical composite strata of water-rich loess + gravel + loose sandstone. When the maximum water inflow reaches 6000m³ / d, the collapse body is in a fluid plastic state and continues to slide, a large collapse cavity is formed at the arch, the initial support deforms and cracks, and the conventional technology completely fails, the above-mentioned construction method of this application is more suitable for treatment. Attached Figure Description

[0022] Figure 1This is a cross-sectional view of the temporary support for the collapsed section of the tunnel involved in the construction method for the comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to the present invention. Figure 2 This is a schematic diagram of the longitudinal section of the composite curtain grouting in the collapsed section of a water-rich loess tunnel, which is involved in the construction method of the present invention for the comprehensive treatment of water inrush and collapse in water-rich loess tunnels. Figure 3 This is a detailed drawing of the temporary support transverse connection structure involved in the construction method of the present invention for the comprehensive treatment of water inrush and collapse in water-rich loess tunnels.

[0023] The markings in the diagram are: 1. Steel arch frame, 2. Anchor pipe, 3. Secondary lining, 4. Water collection well, 5. Collapsed body, 6. Horizontal timber stack. Detailed Implementation

[0024] like Figure 1 , Figure 2 as well as Figure 3The invention illustrates a construction method for the comprehensive treatment of water inrush and collapse in water-rich loess tunnels, which significantly shortens the construction cycle and effectively ensures the treatment quality. The construction method involves first rapidly lowering the groundwater level, cutting off water hazard channels, and preventing the continuous softening and collapse of the surrounding rock through multi-stage disaster control and drainage measures such as interception, guidance, and drainage. Then, an integrated high-rigidity temporary support system consisting of arch protection, horizontal bracing, timber stacks, and counter-pressure is used to form a circumferential high-rigidity, vertical high-bearing capacity, and overall closed-loop support system behind the water-bearing and collapsed tunnel. Finally, a composite curtain grouting construction process of double grout-stopping wall closure and cavity backfilling is adopted to achieve the compaction and consolidation of the loose collapsed body, the sealing of large-flow water inflow, and the filling of the arch-top cavity. This results in the overall reinforcement of the tunnel curtain and the improvement of the strength and impermeability of the surrounding rock, completing the comprehensive treatment of water-bearing and collapsed tunnels in water-rich loess. In particular, during the double grout-stopping wall closure and cavity backfilling construction, a three-stage composite grouting construction process is adopted, consisting of three-sequence zonal grouting (B→D→A), forward segmented grouting, drill rod retraction segmented grouting, and cluster sleeve valve grouting. The construction method provided in this application first rapidly lowers the groundwater level, cuts off water hazard channels, and prevents the surrounding rock from continuously softening and collapsing through multi-stage interception, diversion, and drainage measures. Then, an integrated high-rigidity temporary support system consisting of arch protection, horizontal bracing, timber stacks, and counter-pressure is used to form a circumferential high-rigidity, vertically strong load-bearing, and overall closed-loop support system behind the water-bearing and collapsed tunnel. Finally, a composite curtain grouting construction process of double-layer grout-stopping walls and cavity backfilling is employed to achieve the dense consolidation of the loose collapsed body, the sealing of large-volume water inflow, and the filling of the arch cavity, thus forming an overall reinforcement of the tunnel curtain and improving the strength and impermeability of the surrounding rock, completing the comprehensive treatment of water-bearing and collapsing tunnels in water-rich loess. This effectively solves the treatment failure problem inherent in existing technologies using single treatment measures. The construction method described in this application can achieve rapid water control, temporary stabilization of the collapse, and consolidation and water blocking, thereby significantly shortening the construction period and effectively ensuring the quality of treatment. The technical solution described in this application is particularly suitable for treating tunnel collapse sections in typical composite strata of water-rich loess, pebbles, and loose sandstone. When the maximum water inflow reaches 6000 m³ / d, the collapse body exhibits a fluid-like state and continuous sliding, a large cavity forms at the arch, and the initial support deforms and cracks, making conventional techniques completely ineffective, the construction method described in this application is more suitable for treatment. It possesses outstanding substantive features and significant progress. Furthermore, considering the actual conditions at the production site, to ensure the subsequent stability of the treated working face, this application, before implementing multi-level disaster control and drainage measures, conducts advanced and precise detection in front of the water-inrushed collapse tunnel. This obtains the precise locations of the cavity, water-rich channels, weak interlayers, and loose material within a 50m radius before and after the collapse section, providing a basis for the dynamic adjustment of subsequent grouting hole locations, grouting pressure, and grout mix ratio. The advanced and precise detection is conducted after dredging, using a combined detection process of geological survey + HSP acoustic reflection + ground-penetrating radar + advanced drilling.After the composite curtain grouting is completed, comprehensive reinforcement construction is required, including densification, thickening, strong locking, and improved waterproofing, to significantly enhance the load-bearing capacity, rigidity, and durability of the integrated treatment structure, ensuring the long-term safety and stability of the tunnel. Specifically, densification is achieved using steel arch frames 1 made of I22a I-beams, with a spacing of 50cm between adjacent sets of steel arch frames 1; thickening is achieved using 60cm thick C30 reinforced concrete for secondary lining 3; strong locking is achieved using anchor pipes 2, welded together from φ89×6mm-6m wall bases, φ60×5mm-4m wall waists, and φ60×5mm-3m arch bases; and improved waterproofing is achieved by fully laying 1.5mm EVA convex shell waterproofing membrane + 20KN / m non-woven fabric + horizontal drainage pipes spaced 4m apart for optimized drainage and waterproofing.

[0025] Accordingly, in order to improve the convenience of construction and ensure the reliability of the treatment effect, the multi-stage disaster control and drainage measures of this application include downstream water collection, diversion and seepage prevention, and graded pumping. During downstream water collection, a 2.0m×1.4m water collection well 4 is set up downstream of the collapse section to collect the gushing water and serve as a permanent seepage ditch inspection well in the later stage. During diversion and seepage prevention, a φ500mm PE steel corrugated pipe is used to divert the gushing water, and a 20cm gravel filter layer + double layer of permeable geotextile is set at the pipe opening to prevent silt blockage. During graded pumping, a 37kW fixed pump + a 7.5kW mobile pump are deployed in the tunnel, with a maximum drainage capacity of ≥6000m³ / d and a stable capacity of 3400m³ / d. Before implementing the integrated high-rigidity temporary support system of arch support, horizontal bracing, timber piers, and counter-pressure, a counter-pressure sealing of the normal surface is first carried out. Specifically, this involves laying a φ8×20cm steel mesh on the cleared collapsed section 5, then spraying 12cm thick C25 concrete, and finally stacking sandbags on the outer side to counter-pressure the slope to prevent further collapse. The integrated high-rigidity temporary support system of arch support, horizontal bracing, timber piers, and counter-pressure in this application includes an I22a I-beam temporary arch support in front of the grout-stopping wall, anchorage at the arch foot and side wall, horizontal bracing of the arch support, and horizontal timber piers 6 for reinforcement. The specific process is as follows... I22a I-beam temporary arch supports are installed in a 7m section in front of the grout-stopping wall, with I22a I-beams arranged in a full ring at 80cm longitudinal spacing and connected by φ22 steel bars in the circumference. Two φ60×5mm-4m anchor pipes are installed at the arch foot and side wall, and are obliquely anchored into the rock. I22a I-beam horizontal bracing is installed between the arch supports, forming a closed ring to create an overall load-bearing system. Two 2m×2m solid wood horizontal timber stacks are installed symmetrically in the transverse direction, with a longitudinal net distance of 0.5m, fixed with horseshoe nails and wedges, and the bottom rests on a solid foundation to directly transfer the load of the arch. 28cm thick C25 concrete is sprayed on the outside of the temporary arch supports and horizontal bracing to improve the overall rigidity. The composite curtain grouting of this application, consisting of double-layer grout-stopping walls and cavity backfilling, includes a double-layer grout-stopping wall with 2m thick C30 concrete grout-stopping walls at both upstream and downstream, reinforced with φ22 double-layer steel mesh, and secondary supplementary grouting by pumping fly ash into the cavity at the top of the arch through φ108 pipe roofs to ensure cavity compaction. The three-stage composite grouting process—B→D→A three-sequence zonal grouting, forward segmented grouting, drill rod retraction segmented grouting, and cluster sleeve valve grouting—is carried out according to the following steps. Forward-moving segmented grouting involves drilling in 3-5m sections, using high-pressure air drilling, skip-hole coarse reinforcement, and sealing large voids; backward-moving segmented grouting involves drilling to the designed depth and then retracting to perform segmented grouting for mid-to-deep dense reinforcement; bundled sleeve valve grouting uses φ42×4mm sleeve valve bundles to reinforce weak areas and eliminate blind spots; the grout and parameter requirements are cement-water glass double-liquid grout with W:C=0.8-1:1 and C:S=1:1, grouting pressure 2.0-4.0MPa, diffusion radius 2m, and final hole spacing 2-3.5m; the grouting completion standard is 5-10 minutes after pressure stabilization or when the grout volume reaches 1.5 times the design value, to form a dense consolidation of loose collapsed bodies, seal large-flow water inflows, fill the arch collapse cavity, and provide overall curtain reinforcement, thereby improving the strength and impermeability of the surrounding rock.

[0026] In summary, the technical solution provided in this application also has the following advantages: 1. Highly efficient drainage and disaster control: Three-level linkage and graded drainage quickly cut off water hazard channels, curb the continuous softening of surrounding rock, control the expansion of landslides from the source, and solve the pain points of traditional drainage lagging and ineffective disaster control.

[0027] 2. Temporary support is safe and reliable: The innovative integrated high-rigidity closed-loop support of "counter-pressure + arch protection + cross bracing + timber stack + concrete wrapping" significantly improves the resistance to lateral pressure, deformation and settlement, completely eliminates secondary collapse, and provides a stable working space for high-pressure grouting.

[0028] 3. Advanced detection and precise early warning: High-frequency detection accurately locates collapsed cavities, water-rich areas, and weak interlayers, dynamically optimizes construction parameters, eliminates the risk of blind construction, and achieves controllable risks.

[0029] 4. Curtain grouting for solidification: Double grout-stopping wall + cavity backfilling + three-sequence + three-process composite grouting ensures uniform grout diffusion, dense void filling, efficient water inrush sealing, and uniform surrounding rock reinforcement, effectively consolidating fluid-plastic collapse and solving the problems of grout leakage, voids, and uneven reinforcement in traditional grouting.

[0030] 5. Enhanced support for long-term stability: Comprehensive densification of steel arch frames, reinforcement of locking feet, thickening of secondary lining, and optimization of drainage and waterproofing significantly improve the structural bearing capacity and durability, ensuring the long-term safety and stability of the tunnel.

[0031] 6. Complete system and strong adaptability: The five core modules are organically integrated to form a closed-loop treatment system of detection, drainage, support, grouting and protection, which is accurately adapted to the extreme working conditions of large water inrush, large collapse and large cavity collapse in water-rich loess tunnels, and has significant innovation and practicality.

[0032] The technical solution of this application will be further described below through specific embodiments: This invention aims to overcome the five major defects of existing technologies: weak drainage, poor support, shallow detection, scattered grouting, and weak support. It provides a comprehensive treatment method for water inrush and collapse in water-rich loess tunnels. The core of this method is advanced and precise detection, tiered disaster control and drainage, high-rigidity temporary support, composite curtain grouting, and comprehensive reinforcement of support parameters. This achieves: 1. Rapid water control: Tiered drainage cuts off water hazard channels and curbs the continuous softening of the surrounding rock; 2. Temporary collapse stabilization: High-rigidity closed-loop support resists large lateral pressure and prevents secondary collapse; 3. Precise early warning: Multi-method high-frequency detection locates water-rich areas in the collapse cavity and dynamically guides construction; 4. Consolidation and water blocking: Double-layer grout-stopping walls + three-sequence + composite grouting achieve dense consolidation and seal the water inrush; 5. Long-term stability: Comprehensive reinforcement of support parameters improves structural bearing capacity and durability. Ultimately, this forms a safe, efficient, controllable, and durable integrated treatment system, solving the problems of large water inrushes, large collapses, and large cavities in water-rich loess tunnels.

[0033] This invention is a comprehensive treatment method for water inrush and collapse in loess tunnels, which is implemented in sequence through five core steps: advanced detection, graded drainage, temporary support, curtain grouting, and support reinforcement, forming a closed-loop treatment system.

[0034] I. Advanced and Precise Detection (Encryption + Multiple Methods + Dynamic Early Warning) Detection combination: After dredging, a combination of geological survey + HSP acoustic reflection + ground-penetrating radar + advanced drilling is used to detect the collapse section within a 50m range before and after it; to accurately locate the collapse cavity, water-rich channels, weak interlayers, and the range of loose material. Dynamic adjustment: Optimize grouting hole location, pressure, and grout mix ratio based on detection results to avoid blind construction.

[0035] II. Tiered disaster control and drainage (interception-diversion-drainage three-level linkage) Downstream water collection: A 2.0m×1.4m water collection well is set up downstream of the collapsed section, which will later be used as a permanent seepage ditch inspection well; Water diversion and seepage prevention: φ500mm PE steel corrugated pipe is used to divert the gushing water. The pipe opening is equipped with a 20cm crushed stone filter layer + double layer of permeable geotextile to prevent silt blockage. Staged drainage: A 37kW fixed pump + a 7.5kW mobile pump are deployed inside the tunnel, with a maximum drainage capacity of ≥6000m³ / d, and a stable capacity of 3400m³ / d during the stable period; Core functions: rapidly lower the groundwater level, cut off water hazard channels, prevent the surrounding rock from continuously softening and collapsing, and create a dry working environment for subsequent processes.

[0036] III. High-rigidity temporary support (arch support + cross bracing + timber stack + counter-pressure integrated) Counter-pressure sealing of the working face: After dredging, lay φ8@20cm steel mesh, spray 12cm thick C25 concrete, and stack sandbags on the outside to counter-pressure the slope toe to prevent collapse and slippage; I22a I-beam temporary arch supports are installed in a 7m section in front of the grout-stopping wall, with I22a I-beams arranged in a full ring at 80cm longitudinal spacing and connected by φ22 steel bars in the circumference. Two φ60×5mm anchor pipes (L=4m) are installed at the arch foot and side wall, and are obliquely anchored into the rock. I22a I-beam horizontal bracing is installed between the arch supports, forming a closed ring to create an integrated load-bearing system. Two 2m×2m solid wood stacks are symmetrically installed laterally, with a longitudinal clearance of 0.5m, fixed with horseshoe nails and wedges, and the bottom is placed on a solid foundation to directly transfer the load of the arch. 28cm thick C25 concrete is sprayed on the outside of the temporary arch supports and horizontal bracing to improve the overall rigidity. A circumferentially strong stiffness + vertically strong load-bearing capacity + overall closed-loop support system is formed to resist the large lateral pressure of loess, prevent secondary collapse, and provide a safe and stable working space for high-pressure grouting.

[0037] IV. Composite Curtain Grouting (Double Grout-Stopping Wall + Collapse Cavity Backfill + Three Sequences + Three Processes) Double grout-stopping wall sealing: 2m thick C30 concrete grout-stopping walls are set at the upstream and downstream ends, with φ22 double-layer steel mesh inside; fly ash is pumped into the arch collapse cavity through φ108 pipe roof to fill it, and secondary replenishment is made after grouting to ensure the cavity is dense. Three-sequence grouting zones: Grouting construction is carried out in the order of B→D→A; Three-process composite grouting: Forward segmented grouting: segmented grouting of 3-5m, high-pressure air drilling, skip-hole rough reinforcement, and sealing of large voids; Drill rod retraction segmented grouting: drilling to the design depth and then retracting for segmented grouting, medium-deep layer compaction and reinforcement; Bundled sleeve valve tube grouting: φ42×4mm sleeve valve tube bundle, to reinforce weak areas and eliminate blind spots. Grout and parameters: Cement-water glass two-component grout (W:C=0.8~1:1, C:S=1:1), grouting pressure 2.0~4.0MPa, diffusion radius 2m, final hole spacing 2~3.5m; End criteria: Pressure stabilizes for 5-10 minutes or grouting volume reaches 1.5 times the design value; It consolidates loose collapsed rock, seals large-flow water inrush, fills the collapsed cavity of the arch, and forms an overall reinforced curtain, thereby improving the strength and impermeability of the surrounding rock.

[0038] V. Comprehensive reinforcement of support parameters (densification + thickening + strong locking + superior waterproofing) The steel arch frame has been reinforced: the spacing between I22a I-beams has been adjusted from the original design of 80cm to 50cm; Locking anchor pipe reinforcement: wall base φ89×6mm (L=6m), wall waist φ60×5mm (L=4m), arch foot φ60×5mm (L=3m), welded into a whole; Secondary lining thickening: 60cm thick C30 reinforced concrete across the entire cross section; Optimized waterproofing and drainage: Full coverage with 1.5mm EVA convex shell waterproof membrane + 20KN / m non-woven fabric, and the spacing of horizontal drainage pipes is increased to 4m; Significantly improve the structural bearing capacity, stiffness, and durability to ensure the long-term safety and stability of the tunnel.

[0039] like Figure 1 As shown, the "strong support + anchoring" system at the tunnel face of the collapsed section consists of: I22a I-beam arch frames (80cm spacing) installed outside the existing initial support, with horizontal bracing forming a closed loop; and 28cm of C25 concrete poured outside the temporary support to form the core support system. Two rows of timber supports are installed inside the tunnel face, each 200cm wide, with a net distance of ≥300cm between the two rows. The tops of the timber supports are tightly attached to the temporary support concrete, forming a "double-column" support structure that directly bears the arch load. The bottom is a C25 cast-in-place concrete working platform, with embedded I22a temporary support I-beam horizontal bracing, connecting the bottoms of the two rows of timber supports into a whole to prevent overturning. Two φ60×5 anchor pipes (L=4m) are installed at the arch feet on both sides of the tunnel, driven obliquely into the surrounding rock to anchor the initial support arch feet to the deep rock mass, preventing the arch frame from sinking or expanding outwards.

[0040] like Figure 2 As shown in the figure, this diagram illustrates the longitudinal section construction process and composite curtain grouting system of the tunnel collapse section. It primarily showcases the complete layout of double grout-stopping walls, cavity backfilling, multi-sequence grouting, and face counter-pressure. (1) The left side is marked with secondary lining, initial support, and invert backfill structure. A temporary sump is set up to provide conditions for graded drainage. (2) Longitudinal arrangement of temporary support: Multiple I22a I-beam temporary arches are set up downstream of the collapse section and welded to the longitudinal connecting bars to form a whole. Lateral support is set up, the temporary support is wrapped with concrete, and support timber is set up on the outside to form a longitudinal continuous stress zone; (3) Double grout-stopping wall sealing system: 2m thick C30 reinforced concrete grout-stopping walls are set at the upstream and downstream ends, with φ22 double-layer steel mesh (spacing @40cm) inside to form a closed grouting cavity to prevent grout from running out or leaking. (4) Multi-sequence curtain grouting arrangement: B1 / B2, A1 / A2, D1 / D2 grouting sequence, covering the arch and sidewall loose body, and three-dimensional reinforcement is achieved through multi-sequence zoned grouting; (5) Backfilling of the collapsed cavity and counterpressure at the working face: A φ108×6mm pumping pipe is reserved for pumping fly ash to backfill the collapsed cavity at the top of the arch; counterpressure soil is set at the working face to prevent the collapse from sliding and to provide a safety guarantee for grouting construction.

[0041] like Figure 3 As shown, temporary supports are provided using I22a I-beam columns, arranged longitudinally along the tunnel at 80cm intervals, directly transferring vertical loads. The I-beam columns are longitudinally connected to the cross braces using φ22 V-shaped steel connecting bars, arranged crosswise at 1000 / 2000mm intervals (longitudinal / circumferential), connecting the individual I-beam columns into a stable truss structure to prevent column instability and collapse.

[0042] Example 1 1. Construction Preparation 1) Materials: I22a I-beams, φ60 / φ89 anchor pipes, φ42 sleeve valve pipes, φ108 pipe sheds, C25 / C30 concrete, cement, water glass, fly ash, solid wood boards, etc., all passed the on-site retesting; 2) Equipment: Dual-liquid grouting pump, down-the-hole drill, wet shotcrete machine, electric welding machine, ground-penetrating radar, borehole imaging instrument, total station, level, etc., all calibrated and qualified; 3) Technology: Re-measurement of centerline elevation, establishment of monitoring points, preparation of special plans, and technical briefing at each level; 4) On-site: Clear the collapsed area, install a drainage system, provide ventilation and lighting, and ensure safety protection is in place.

[0043] 2. Implementation of Advanced Detection 1) Employing joint detection methods to accurately locate collapsed cavities and water-rich areas; 2) Deploy monitoring points on the surface and inside the cave, and increase the frequency of monitoring; 3) Analyze the detection data and optimize the grouting parameters and construction plan.

[0044] 3. Graded drainage construction 1) Construct a seepage trench inspection well downstream and install a flow guide corrugated pipe; 2) Deploy and test drainage equipment in stages; 3) Dynamically adjust the pumping capacity to maintain a dry working environment inside the tunnel.

[0045] 4. Construction of high-rigidity temporary supports 1) Dredging the working face, laying netting, spraying concrete, and stacking sandbags for counterweighting; 2) Measure and lay out the lines, install the I22a temporary arch support, and install the cross bracing; 3) Construct anchor pipes and pour concrete on the outer side; 4) Stack vertical timber stacks, wedge hardwoods tightly, and reinforce with secondary hammering.

[0046] 5. Composite curtain grouting construction 1) Double-layer grout-stopping walls are poured upstream and downstream, and cured to the required standards; 2) Pipe shed installation and pumping fly ash to backfill collapsed cavities; 3) Implement forward grouting + backward grouting + sleeve valve pipe composite grouting according to the B→D→A sequence, and strictly control the grouting pressure, grout ratio and termination criteria; 6. Construction with reinforced support parameters 1) After the grouting reaches the standard, excavate the working face and erect I22a steel arch frames with a spacing of 50cm one by one; 2) Install reinforced anchor pipes and weld them securely; 3) Timely construction of the invert arch and initial support to form a closed ring; 4) Lay waterproof membrane, tie steel bars, and pour 60cm thick secondary lining; 5) Monitor the deformation of the surrounding rock throughout the process and dynamically adjust the construction parameters.

[0047] 7. Safety and Quality Control 1) Protective equipment should be worn when working inside the tunnel, which should be well-ventilated and a warning zone should be set up; 2) During high-pressure grouting, it is strictly forbidden to face the grouting port directly; real-time monitoring of surrounding rock deformation is required. 3) Strictly implement quality acceptance standards and inspect and accept each process step by step; 4) Keep good construction records, archive them for future reference, and ensure that the whole process is controllable.

Claims

1. A construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels, characterized by: The construction method involves first rapidly lowering the groundwater level, cutting off water hazard channels, and preventing the continuous softening and collapse of the surrounding rock through multi-stage interception, guidance, and drainage measures. Then, an integrated high-rigidity temporary support system consisting of arch protection, horizontal bracing, timber stacks, and counter-pressure is used to form a circumferential high-rigidity, vertically strong, and overall closed-loop support system behind the water-bearing and collapsed tunnel. Finally, a composite curtain grouting construction process combining double-layer grout-stopping walls and cavity backfilling is employed to achieve the compaction and consolidation of the loose collapsed body, the sealing of large-volume water inflows, and the filling of the arch-top cavity. This results in overall reinforcement of the tunnel curtain and an improvement in the strength and impermeability of the surrounding rock, completing the comprehensive treatment of water-bearing and collapsed tunnels in water-rich loess. Among them, when carrying out the double grout stop wall sealing and cavity backfilling construction, a three-process composite grouting construction technology is adopted, which is B→D→A three-sequence zonal grouting + forward segmented grouting - drill rod retraction segmented grouting - bundled sleeve valve pipe grouting.

2. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 1, characterized in that: Before implementing multi-level disaster control and drainage measures, a precise advance detection was conducted in front of the water-bearing and collapsed tunnel to obtain the precise location of the collapsed cavity, water-rich channels, weak interlayers, and loose bodies within a 50m range before and after the collapsed section. This provided a basis for the dynamic adjustment of subsequent grouting hole locations, grouting pressure, and grout mix ratio.

3. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 2, characterized in that: Advanced and precise detection is carried out after dredging, using a combined detection process of geological survey, HSP acoustic reflection, ground-penetrating radar, and advanced drilling.

4. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 1, characterized in that: After the composite curtain grouting is completed, the support parameters need to be comprehensively strengthened by increasing density, thickness, strong locking, and superior waterproofing to significantly improve the load-bearing capacity, rigidity, and durability of the integrated treatment structure and ensure the long-term safety and stability of the tunnel.

5. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 4, characterized in that: The densification construction uses steel arch frames (1) made of I22a I-beams, with a spacing of 50cm between two adjacent sets of steel arch frames (1); the thickening construction uses 60cm thick C30 reinforced concrete for secondary lining (3); the strong locking foot uses locking foot anchor pipes (2), which are welded together as a whole by φ89×6mm-6m wall foot, φ60×5mm-4m wall waist and φ60×5mm-3m arch foot; the superior waterproofing uses 1.5mm EVA convex shell waterproof board + 20KN / m non-woven fabric + horizontal drainage pipes with a spacing of 4m for waterproofing and drainage optimization construction.

6. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 1, characterized in that: The multi-level disaster control and drainage measures of interception-guidance-drainage include downstream water collection, diversion and seepage prevention and graded pumping. When collecting water downstream, a 2.0m×1.4m water collection well (4) is set up downstream of the collapse section to collect the gushing water and serve as a permanent seepage ditch inspection well in the later stage. When diverting and preventing seepage, a φ500mm PE steel corrugated pipe is used to divert the gushing water. A 20cm gravel filter layer + double-layer permeable geotextile is set at the pipe opening to prevent silt blockage. When pumping in stages, a 37kW fixed pump + 7.5kW mobile pump is set up in the tunnel. The maximum drainage capacity is ≥6000m³ / d and maintained at 3400m³ / d during the stable period.

7. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 1, characterized in that: Before implementing the integrated high-rigidity temporary support of arch protection + cross bracing + timber stack + counter-pressure, the constant surface counter-pressure closure is carried out. Specifically, φ8×20cm steel mesh is first laid on the dredged landslide body (5), then 12cm thick C25 concrete is sprayed, and finally sandbags are stacked on the outside to counter-pressure the slope foot to prevent the landslide body from sliding.

8. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 7, characterized in that: The integrated high-rigidity temporary support system consisting of arch support, horizontal bracing, timber piers, and counter-pressure includes an I22a I-beam temporary arch support in front of the grout-stopping wall, anchorage at the arch foot and side wall, horizontal bracing of the arch support, and horizontal timber piers (6) for reinforcement. The specific process is as follows: I22a I-beam temporary arch support, with I22a I-beams arranged in a full ring for 7m in front of the grout-stopping wall, with a longitudinal spacing of 80cm and circumferential φ22 steel bars for connection; two φ60×5mm-4m locking anchor pipes (2) are installed at the arch foot and side wall respectively, and are obliquely anchored into the rock; I22a I-beam horizontal bracing is installed between the arch support, forming a closed ring to form an overall load-bearing system; two 2m×2m solid wood horizontal stacks (6) are symmetrically installed laterally, with a longitudinal net distance of 0.5m, fixed with horseshoe nails, and wedges are tightened, with the bottom resting on a solid foundation to directly transfer the arch load; 28cm thick C25 concrete is sprayed on the outside of the temporary arch support and horizontal bracing to improve the overall rigidity.

9. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 8, characterized in that: The composite curtain grouting of double grout-stopping wall sealing and cavity backfilling includes double grout-stopping wall sealing with 2m thick C30 concrete grout-stopping walls at both the upstream and downstream sides, and double grout-stopping walls with φ22 double-layer steel mesh inside, and secondary supplementary grouting by pumping fly ash into the cavity at the top of the arch through φ108 pipe roof to ensure the cavity is dense.

10. The construction method for comprehensive treatment of water inrush and collapse in water-rich loess tunnels according to claim 9, characterized in that: The three-process composite grouting construction, consisting of three-sequence zonal grouting (B→D→A), forward segmented grouting, drill pipe retraction segmented grouting, and bundled sleeve valve grouting, is carried out according to the following steps. Forward-moving segmented grouting involves drilling in 3-5m sections, using high-pressure air drilling, skip-hole coarse reinforcement, and sealing large voids; backward-moving segmented grouting involves drilling to the designed depth and then retracting to perform segmented grouting for mid-to-deep dense reinforcement; bundled sleeve valve grouting uses φ42×4mm sleeve valve bundles to reinforce weak areas and eliminate blind spots; the grout and parameter requirements are cement-water glass double-liquid grout with W:C=0.8-1:1 and C:S=1:1, grouting pressure 2.0-4.0MPa, diffusion radius 2m, and final hole spacing 2-3.5m; the grouting completion standard is 5-10 minutes after pressure stabilization or when the grout volume reaches 1.5 times the design value, to form a dense consolidation of loose collapsed bodies, seal large-flow water inflows, fill the arch collapse cavity, and provide overall curtain reinforcement, thereby improving the strength and impermeability of the surrounding rock.

Images