Blasting excavation method for air cushion type surge chamber

Abstract

The invention discloses a blasting excavation method for an air cushion type surge chamber, belongs to the technical field of blasting construction of underground caverns of water conservancy and hydropower engineering, and mainly solves the technical problems of poor surrounding rock stability, difficulty in water seepage control and insufficient forming precision in construction of the air cushion type surge chamber in a traditional excavation method. According to the technical scheme, the method is characterized by comprising the steps that excavation is conducted in five layers in the vertical direction, middle pilot tunnels are adopted in the first top arch layer to conduct expanding excavation on the two sides in advance, the side wall safety distance is controlled, and before construction, drainage holes are drilled in a water seepage crack area for pouring to form a drainage curtain; half-range excavation and alternate supporting are carried out on the second layer of upper-layer side wall, the third layer of middle-layer side wall and the fourth layer of lower-layer side wall; the fifth bottom plate layer is excavated in a half-range horizontal smooth blasting mode, and a protective layer is reserved; and after each layer is excavated, systematic anchoring and shotcreting support is immediately carried out, and blasting rock ballast is mechanically loaded and transported. The method is mainly used for high-precision blasting construction of the air cushion type surge chamber of the large hydropower station, and surrounding rock stability and structural safety under the high osmotic pressure environment are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water conservancy and hydropower engineering underground cavern blasting construction, and particularly relates to a gas cushion type surge chamber blasting excavation method. BACKGROUND

[0002] In the construction of gas cushion type surge chambers in water conservancy and hydropower engineering, the traditional blasting excavation method has several technical limitations. In terms of surrounding rock stability control, the conventional vertical layering method (usually 3 layers) is difficult to adapt to the stress distribution characteristics of large-span caverns (span > 20 meters), especially when the cavern height exceeds 40 meters. The unloading rebound caused by lower layer excavation will lead to shear slip of the upper layer supported side wall, and the measured interface displacement can reach 25-40 mm. This deformation is caused by stress redistribution at the layering interface. The existing technology relies on increasing the density of system anchors to control deformation, but the anchoring force transmission is affected by the rheological properties of the rock mass, and the supporting effectiveness decreases by more than 30% after the excavation period exceeds 7 days.

[0003] The water seepage pressure management problem is prominent. The surrounding rock of high water head surge chamber often develops a fracture network with a permeability coefficient of 10 -4 ~10 -3 cm / s. Although traditional pre-grouting can reduce seepage, the uniaxial compressive strength of the grouted rock mass increases by 35%-60%, and its brittleness leads to brittle fracture under the action of blasting vibration. Engineering measurements show that the blasting damage depth in the grouting area reaches 0.8-1.2 meters, which is 70% higher than that of the original rock mass, and the damage area and the non-grouting area are prone to form hydraulic fracturing channels. The existing technology attempts to reduce the overall charge to control vibration, but it leads to oversized rock fragments (> 60 cm, accounting for more than 35%), increasing the cost of mechanical crushing.

[0004] The essence of these problems lies in the fact that the mechanical response of layering excavation and the coupling effect of seepage field-stress field are not systematically coordinated; the blasting energy release and the spatial variation of rock mass strength lack an adaptive mechanism; and the vibration cumulative damage and time-dependent deformation control have not established a feedback path. The existing technology improves a single link (such as optimizing the number of layers or improving the grouting formula), but fails to integrate the dynamic correlation system of excavation procedure, seepage pressure control, and blasting parameter adjustment. SUMMARY

[0005] It is an object of embodiments of the present application to solve at least the above problems and / or deficiencies, and to provide at least the advantages stated hereinafter.

[0006] It is another object of the present application to provide a gas cushion type surge chamber blasting excavation method to solve the problems of traditional full-face excavation method in large-section gas cushion type surge chambers under complex hydrogeological conditions, such as high risk of surrounding rock instability, high risk of water inrush and mud burst, and damage to the formed drainage curtain and surrounding rock caused by blasting vibration, which makes it difficult to ensure excavation safety, forming quality and long-term stability.

[0007] To solve the above-mentioned invention purposes, the application adopts the following technical solutions to achieve them: A gas cushion type pressure regulating chamber blasting excavation method, comprising the following steps: The gas regulating chamber excavation is divided into 5 layers along the vertical direction, from top to bottom, they are the first layer of top arch layer, the second layer of upper layer side wall, the third layer of middle layer side wall, the fourth layer of lower layer side wall and the fifth layer of bottom plate layer; The first layer adopts the construction procedure of first expanding excavation on both sides of the middle pilot hole, first excavating the middle pilot hole along the chamber axis, and then expanding excavation to both sides; Before the construction of the first layer of top arch layer, drill drainage holes in the water seepage fracture development area and form a drainage curtain by grouting to reduce the seepage pressure of surrounding rock; The second layer, the third layer and the fourth layer adopt half-width excavation, one side is excavated first, and the other side is excavated after the support is completed; The fifth layer adopts half-width horizontal light blasting excavation, and a protective layer is reserved; After each layer is excavated, systematic anchor shotcrete support is immediately carried out to ensure that the surrounding rock is stable before the next layer construction.

[0008] Preferably, in the gas cushion type pressure regulating chamber blasting excavation method, the middle pilot hole blasting adopts a staged charging structure: A diameter of 35-40mm cartridge is used for continuous charging of the slotting hole to form an effective free face; A diameter of 28-32mm cartridge is used for continuous charging of the caving hole to control the rock fragmentation size; A diameter of 20-25mm cartridge is used for interval charging of the peripheral hole without coupling; In the grouting reinforcement area of the drainage curtain, a buffer hole is added between the slotting hole and the peripheral hole, and a shock-absorbing charging structure with a 30%-50% reduced linear charge density is used.

[0009] Preferably, in the gas cushion type pressure regulating chamber blasting excavation method, the setting of the buffer hole and the shock-absorbing charging include the following operations: The buffer hole column is arranged in parallel along the outside of the excavation contour line 0.8 to 1.2 meters away, and the hole spacing is 1.2 to 1.5 times the caving hole; The interval charging structure of bamboo blank fixed small-diameter cartridge is used, and the linear charge density is reduced by 30% to 50% compared with the caving hole; The initiation timing is set as four-stage millisecond initiation of the slotting hole, the caving hole, the buffer hole and the peripheral hole, and the delay time of adjacent segments is greater than 50 milliseconds; According to the detection results of the core sampling strength of the grouting area, the buffer hole charge density is dynamically adjusted: when the uniaxial compressive strength increases by more than 40%, the linear charge density is reduced by 50%; when the increase is 20% to 40%, the linear charge density is reduced by 30%.

[0010] Preferably, in the air cushion type pressure regulating chamber blasting excavation method, the side wall expansion blasting adopts a differential charging strategy: The main collapse area adopts a continuous charging structure to ensure that the rock is fully broken, and the main collapse area refers to the blasting area outside 1.5 meters from the design contour line; The contour control area adopts interval uncoupling charging to reduce the damage to the formed surface, and the contour control area refers to a range of 0.3 to 1.5 meters from the design contour line; The strength mutation zone is located at the junction of the high-strength zone and the low-strength zone, extends along the contour line for 2 to 3 meters wide, and implements variable density charging in this zone: the line charging density in the high-strength zone is reduced by 30% to 40% of the reference value, and the low-strength zone maintains the reference charging density. The charging boundary dynamically shifts according to the diffusion radius of the curtain grouting, and the shift amount is controlled within 0.3 to 0.5 meters; the high-strength zone is the core influence area of the drainage curtain grouting, and the uniaxial compressive strength is increased by more than 40% compared with the original rock mass, and the boundary is determined by drilling core strength detection; the low-strength zone is the original rock mass area not covered by the drainage curtain.

[0011] Preferably, in the air cushion type pressure regulating chamber blasting excavation method, the half-width excavation blasting implements energy gradient release control: The main blasting area adopts continuous charging to achieve efficient rock breaking; The pre-splitting area adopts interval uncoupling charging to form a flat fracture surface; A transition hole row is added between the pre-splitting hole and the main blasting hole, and a line charging density between the main blasting hole and the pre-splitting hole is used to form a stress transmission buffer zone.

[0012] Preferably, in the air cushion type pressure regulating chamber blasting excavation method, the implementation of the transition hole row includes the following operations: A single row of transition holes is arranged parallel to the contour line between the pre-splitting hole and the main blasting hole, 0.6 to 0.8 meters away from the pre-splitting hole and 0.4 to 0.6 meters away from the main blasting hole; An interval charging structure is used to fix the cartridge, and the line charging density is 50% to 70% of the main blasting hole; The initiation timing is set to three-stage millisecond initiation of the pre-splitting hole, the transition hole, and the main blasting hole, and the inter-stage delay is greater than 30 milliseconds.

[0013] Preferably, in the air cushion type pressure regulating chamber blasting excavation method, the bottom layer protection layer blasting implements rock integrity control: Horizontal light blasting technology is used to reduce the damage of blasting vibration to the floor; The reserved protection layer absorbs the impact of blasting energy; In the seepage active area, the encryption shock absorption hole arrangement is implemented; The encryption shock absorption hole arrangement includes the following steps: The area with pore water pressure > 0.2 MPa is determined as the densification and shock absorption area by advanced borehole pressure monitoring; The reference area shock absorption hole spacing is 1.0 meters, The hole spacing in the densification and shock absorption area is reduced to 0.5 meters and arranged in a quincunx shape to form a stress dissipation network; The shock absorption hole penetrates the protective layer to 0.5 meters below the bedrock, and the hole is filled with water-permeable sand and gravel; When the real-time monitoring seepage pressure value rises above 0.3 MPa, a drainage and pressure relief hole is added in the center of the quincunx hole network.

[0014] Preferably, the air cushion type pressure regulating chamber blasting excavation method further comprises a reliability guarantee system for initiation in a water permeable environment: In the drainage curtain construction section, the blasting network uses a double circuit non-electric detonating tube system, the main circuit is laid along the high wall, and the standby circuit is laid along the inner wall of the borehole; All detonating tube joints are wrapped with water-repellent buffer mortar, and a waterproof sealing cover is installed outside the detonator; For the top arch dripping area, a quick-setting waterproof coating capsule is sleeved outside the initiation charge, which forms a sealed protective layer within 10 seconds of contact with water.

[0015] Preferably, the air cushion type pressure regulating chamber blasting excavation method further comprises the following steps: At the interface between adjacent excavation layers on the excavated side, micro-expansion quick-setting resin high-strength prestressed anchor rods are arranged in a ring shape, with an inclination angle of 10°-15°, and penetrating 3-5 meters into the unexcavated rock mass of the lower layer; The prestress compensation system is installed within 24 hours after each layer is excavated, which includes a hydraulic jack and a pressure sensor, and dynamically adjusts the tension of the high-strength prestressed anchor rod according to the convergence monitoring data of the surrounding rock; When the sidewall convergence rate exceeds 0.5 mm / d, the automatic compensation mode is started, and the prestress of the high-strength prestressed anchor rod is increased to 120%-150% of the design value; For the water permeable section of the drainage curtain, the free section of the high-strength prestressed anchor rod is wrapped with a water-permeable resin filter membrane, and its permeability coefficient is kept ≥1×10 -3 cm / s.

[0016] Preferably, in the air cushion type pressure regulating chamber blasting excavation method, a vibration monitoring and protection system is arranged on the inner side of the sidewall after the support is completed: A distributed vibration sensor network is installed every 5 meters along the axis direction of the hole to real-time collect the blasting vibration speed and frequency components; A blasting vibration cumulative damage model is established, and when the rock mass damage factor D is monitored to be > 0.25, an encryption self-advancing hollow grouting anchor rod is implemented in the damage area before the next cycle of blasting, with a length penetrating the current excavation layer and deep into the lower rock mass by 2 meters; In the influence area of the drainage curtain, a water-permeable polyurethane foam cushion layer is laid between the supporting layer and the surrounding rock, and the dynamic elastic modulus is controlled in the range of 0.5-1.0 GPa.

[0017] Compared with the prior art, the application has the advantages and beneficial technical effects that: The overall framework of layering, blocking, curtain first and excavation second, and timely support provides a systematic safety solution for high water pressure and large section pressure regulating chamber excavation, effectively isolates the water seepage threat, controls the mutual disturbance between excavation steps, and ensures the feasibility and fundamental safety of engineering construction under complex conditions.

[0018] The application ingeniously solves the problem of easy blasting damage in high-strength grouting area by introducing a buffer hole and a shock-absorbing charge structure in the middle pilot hole blasting, which maximizes the protection of the integrity and impermeability of the drainage curtain while ensuring excavation efficiency, creating a dry and stable working environment for subsequent excavation.

[0019] The application precisely designs the layout parameters, charge structure and initiation sequence of the buffer hole, and dynamically correlates the charge density with the rock mass strength, ensuring that the buffer hole can efficiently perform the expected function, significantly attenuating the blasting stress wave, and creating ideal conditions for smooth blasting of the surrounding holes, thereby obtaining a high-quality excavation contour surface.

[0020] The application uses a variable-density charge strategy at the junction between high and low strength rock masses, and dynamically adjusts the boundary line according to the grouting diffusion range, achieving precise matching of blasting energy and rock mass blast resistance, effectively avoiding defects in the formed surface caused by uneven strength, and obtaining a smooth, stable and controlled overbreak and underbreak side wall contour.

[0021] The application sets up a transition hole column between the main blast hole and the pre-splitting hole, creating a buffer zone for gradient release of blasting energy, smoothing the transmission of explosive stress waves, significantly reducing the disturbance and damage to the retained area rock mass, and effectively controlling flying stones, protecting the surrounding rock and ensuring construction safety.

[0022] The application precisely designs the spacing, charge and initiation network of the transition hole column, and can flexibly adjust the layout scheme according to the rock mass conditions, ensuring that the buffer zone can work reliably under different geological conditions, greatly improving the adaptability and effectiveness of the half-width excavation energy control technology.

[0023] The application forms a multiple protection mechanism for the floor foundation by combining horizontal smooth blasting, a protective layer and an encrypted shock-absorbing hole network based on seepage pressure monitoring, not only controlling the direct damage of blasting to the floor rock mass, but also effectively dissipating vibration energy and guiding pore water pressure, fundamentally ensuring the stability and bearing safety of the floor structure.

[0024] The present application adopts double circuit laying, multiple waterproof sealing and rapid setting waterproof capsule, etc.

[0025] The present application pre-sets inclined high-strength prestressed anchor rods at the interfaces of each layer and is equipped with a prestressed dynamic compensation system, actively strengthens the mechanical connection of the interlayer rock mass, can timely inhibit the deformation of the surrounding rock, reduces the'stacked pancake effect' of the layered excavation to the minimum, and ensures the overall stability of the high side wall during the construction period and the operation period.

[0026] The present application combines real-time vibration monitoring, intelligent damage assessment and active reinforcement measures to build an intelligent protection system of perception-evaluation-response, realizes the awareness and control of the cumulative damage of the surrounding rock caused by blasting, can timely repair the damage and prevent its cumulative deterioration, and significantly improves the long-term safety margin of the project.

[0027] Other advantages, objects and features of the embodiments of the present application will be apparent to those skilled in the art from the following description, and will be understood by those skilled in the art through research and practice of the embodiments of the present application. DETAILED DESCRIPTION

[0028] To further illustrate the technical means adopted by the present application and its effects, the present application will be further described below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present application, and are not limiting to the present application.

[0029] It should be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0030] According to one of the schemes of the present application, a gas cushion type surge chamber blasting excavation method, a gas cushion type surge chamber blasting excavation method, characterized in that, comprising the following steps: The gas conditioning chamber is divided into 5 layers along the vertical direction, from top to bottom, the first layer is the top arch layer, the second layer is the upper side wall, the third layer is the middle side wall, the fourth layer is the lower side wall, and the fifth layer is the bottom plate layer; The first layer adopts the construction procedure of first expanding excavation on both sides of the middle pilot hole, first excavates the middle pilot hole along the axis of the chamber, then expands excavation to both sides, and ensures that the upper and lower side walls are expanded with a safe distance; Before the construction of the first layer top arch layer, drainage holes are drilled in the water seepage fracture development area and drainage curtain is formed by grouting to reduce the seepage pressure of the surrounding rock; The second layer, the third layer and the fourth layer are excavated in half, one side is excavated first, and the other side is excavated after the support is completed; The fifth layer is excavated by half-width horizontal light blasting, and a protection layer is reserved; Immediately after each layer is excavated, systematic anchor-shot supporting is performed to ensure that the surrounding rock is stable before the next layer is constructed; The blasting stone is mechanically loaded and transported.

[0031] For example, for the water-permeable and broken Ordovician slate geology: Layered excavation: Before the top arch layer of the first layer is excavated, drainage holes with a dip angle of 75° and a spacing of 0.8 m are drilled along the left side of the crack development area (0+36~0+40.7 m), and a drainage curtain is formed by injecting quick-setting chemical slurry; The middle pilot hole is excavated first, and the safety distance is controlled to be 5 m when the two sides are excavated; The second to fourth layers are excavated by half-width (the upstream side is supported first and then the downstream side); The fifth layer is excavated by half-width horizontal light blasting, and a protection layer of 1.2 m is reserved.

[0032] Dynamic support: anchor-shot support is completed within 2 hours after each layer is blasted, and the rock mass is stable before the next layer is excavated.

[0033] In the scheme, the drainage curtain actively blocks the water seepage path to avoid water-rock coupling weakening the strength of the surrounding rock; Layered half-width excavation reduces the superposition effect of blasting vibration and protects the existing supporting structure; The protection layer design ensures the integrity of the bottom plate rock mass and reduces the repair cost in the later period.

[0034] According to one of the embodiments of the present application, the middle pilot hole blasting adopts a staged charging structure: The cut hole uses a diameter of 35-40 mm cartridge to form an effective free face; The caving hole uses a diameter of 28-32 mm cartridge to control the rock fragmentation size; The peripheral hole uses a diameter of 20-25 mm cartridge to form an effective free face; For the drainage curtain grouting reinforcement area, a buffer hole is added between the cut hole and the peripheral hole, a shock-absorbing charging structure with a reduced line charge density of 30%-50% is used, and the blasting vibration is inhibited to trigger the brittle fracture of the rock mass in the grouting area.

[0035] The undercut hole is continuously charged with a 35-40 mm diameter cartridge to form an effective free surface, the caving hole is continuously charged with a 28-32 mm diameter cartridge to control the rock fragmentation size, and the peripheral hole is charged with a 20-25 mm diameter cartridge in an interval and decoupling manner. For the drainage curtain grouting reinforcement area, a buffer hole is additionally arranged between the undercut hole and the peripheral hole, a shock absorption charging structure with reduced linear charge density is adopted to inhibit the blasting vibration from triggering the brittle failure of the rock mass in the grouting area. Compared with the closest prior art, the traditional method does not provide a buffer hole and shock absorption charging in the grouting area, which leads to a significant increase in the blasting damage depth. The influence of the blasting vibration on the grouting reinforcement area is effectively controlled, the rock mass damage is reduced, and the stability of the excavation surface is improved.

[0036] According to one of the embodiments of the present application, the setting of the buffer hole and the shock absorption charging include the following operations: The buffer hole row is arranged in parallel along the outside of the excavation contour line of the drainage curtain grouting area at a distance of 0.8-1.2 m, and the hole spacing is 1.2-1.5 times that of the caving hole; The interval charging structure of the small-diameter cartridge is fixed by bamboo blanks, and the linear charge density is reduced by 30%-50% compared with the caving hole; The initiation timing is set as four-stage millisecond initiation of the undercut hole, the caving hole, the buffer hole, and the peripheral hole, and the delay time of adjacent segments is greater than 50 ms; The buffer hole charge density is dynamically adjusted according to the strength detection results of the rock core sampling in the grouting area: when the uniaxial compressive strength increases by more than 40%, the linear charge density is reduced by 50%; and when the increase is 20%-40%, the linear charge density is reduced by 30%.

[0037] The buffer hole row is arranged along the outside of the excavation contour line of the drainage curtain grouting area, the hole spacing is a multiple of the caving hole, the interval charging structure of the small-diameter cartridge is fixed by bamboo blanks, the linear charge density is reduced compared with the caving hole, the initiation timing is set as four-stage millisecond initiation, the delay time of adjacent segments is greater than 50 ms, and the buffer hole charge density is dynamically adjusted according to the strength detection results of the rock core sampling in the grouting area. Compared with the closest prior art, the traditional method does not dynamically adjust the charging parameters according to the rock mass strength, which is easy to cause excessive damage or insufficient fragmentation. The present scheme can optimize the blasting energy release, adapt to the rock mass strength variation, and enhance the blasting control precision and the surrounding rock protection effect.

[0038] According to one of the embodiments of the present application, the side wall expansion blasting adopts a differential charging strategy: The main caving area adopts a continuous charging structure to ensure sufficient rock fragmentation, and the main caving area refers to the blasting area outside the design contour line by 1.5 m; The contour control area adopts an interval and decoupling charging to reduce the damage to the formed surface, and the contour control area refers to a range of 0.3-1.5 m from the design contour line; Aiming at the strength difference between the influence area and the non-influence area of the drainage curtain, the strength mutation zone is located at the junction of the high strength area and the low strength area, extends along the contour line for 2-3 meters wide, and the variable density charging is implemented in the zone: the linear charging density in the high strength area is reduced by 30-40% of the reference value, the linear charging density in the low strength area is maintained at the reference value, the charging boundary is dynamically offset according to the grouting diffusion radius of the curtain, and the offset amount is controlled within 0.3-0.5 meters; the high strength area is the core influence area of the drainage curtain grouting, the uniaxial compressive strength of which is increased by more than 40% compared with the original rock mass, and the boundary is determined by drilling core strength detection; the low strength area is the original rock mass area not covered by the drainage curtain, and the reference rock mass strength characteristics are maintained.

[0039] The main collapse area adopts continuous charging structure to ensure that the rock is fully broken, the contour control area adopts interval decoupling charging to reduce the damage of the formed surface, the variable density charging is implemented for the strength mutation zone, the linear charging density in the high strength area is reduced, the linear charging density in the low strength area is maintained at the reference value, and the charging boundary is dynamically offset according to the grouting diffusion radius of the curtain. Compared with the closest prior art, the traditional method adopts uniform charging parameters, which cannot adapt to the spatial variation of rock mass strength, resulting in uneven quality of the contour surface. The scheme can improve the quality of the side wall excavation and forming, reduce the overbreak and underbreak phenomenon, and ensure the dimensional accuracy and long-term stability of the cavern structure.

[0040] According to one of the embodiments of the present application, the half-width excavation blasting implements energy gradient release control: The main blasting area adopts continuous charging to achieve efficient rock breaking; The pre-splitting area adopts interval decoupling charging to form a flat fracture surface; A transition hole row is additionally arranged between the pre-splitting hole and the main blasting hole, the linear charging density between the main blasting hole and the pre-splitting hole is used, a stress transmission buffer zone is formed, and the generation of blasting flyrock and the deformation of the contour surface are simultaneously inhibited.

[0041] The main blasting area adopts continuous charging to achieve efficient rock breaking, the pre-splitting area adopts interval decoupling charging to form a flat fracture surface, and a transition hole row is additionally arranged between the pre-splitting hole and the main blasting hole. The transition hole uses the linear charging density between the main blasting hole and the pre-splitting hole, thereby forming a stress transmission buffer zone. Compared with the closest prior art, the traditional method usually only sets the main blasting hole and the pre-splitting hole, lacks the intermediate energy transition zone, and the blasting stress wave is violently applied to the contour surface. By gradient release of blasting energy, the generation of blasting flyrock and the deformation of the contour surface are simultaneously inhibited, and the flatness and safety of the excavation surface are improved.

[0042] According to one of the embodiments of the present application, the implementation of the transition hole row includes the following operations: A single row of transition holes is arranged parallel to the contour line between the pre-splitting hole and the main blasting hole, which is 0.6-0.8 meters away from the pre-splitting hole and 0.4-0.6 meters away from the main blasting hole; The interval charging structure is fixed by bamboo blanks, and the linear charging density is 50% to 70% of the main blast hole; The initiation timing sequence is set as three-stage differential initiation of the pre-splitting hole, the transition hole and the main blast hole, and the delay between the segments is greater than 30 milliseconds; The buffer width is dynamically adjusted according to the surrounding rock conditions: when the rock mass integrity is poor, the transition hole column is widened to 1.2 meters in double-row arrangement, and the charging density gradient decreases.

[0043] The single-row transition hole is arranged between the pre-splitting hole and the main blast hole in parallel contour lines, and the spacing thereof from the pre-splitting hole and the main blast hole is strictly controlled. The interval charging structure is fixed by bamboo blanks, and the linear charging density is set as a proportion of the main blast hole. The initiation timing sequence is three-stage differential initiation and ensures sufficient delay between the segments. In addition, the buffer width and arrangement mode are dynamically adjusted according to the integrity of the surrounding rock. Compared with the closest prior art, the blasting parameters of the traditional method are relatively fixed and lack the ability of dynamic adjustment according to the rock mass conditions. The adaptability of blasting energy control is improved, and the optimization for different rock mass integrity is realized, so that a high-quality fracture surface is more reliably formed and the blasting hazards are controlled.

[0044] According to one of the embodiments of the application, the floor layer protection layer blasting implements rock mass integrity control: The horizontal light blasting technology is used to reduce the damage of blasting vibration to the floor; The reserved protection layer absorbs the impact of blasting energy; In view of the poor permeability difference of the floor rock mass caused by the drainage curtain grouting, the encryption shock absorption hole arrangement is implemented in the seepage active area to form a local stress dissipation network and block the propagation of blasting vibration waves to the foundation bearing rock mass; The encryption shock absorption hole arrangement includes the following steps: The area with pore water pressure > 0.2 MPa is marked as an encryption shock absorption area through advanced borehole seepage pressure monitoring; The shock absorption hole spacing in the reference area is 1.0 meters, The hole spacing in the encryption shock absorption area is reduced to 0.5 meters and arranged in a plum blossom shape to form a stress dissipation network; The shock absorption hole penetrates the protection layer to 0.5 meters below the bedrock, and the hole is filled with water-permeable sand and gravel to simultaneously realize vibration wave scattering and pore water drainage; When the real-time monitoring seepage pressure value rises to more than 0.3 MPa, a drainage pressure relief hole is additionally arranged in the center of the plum blossom hole network.

[0045] The horizontal light blasting technology is adopted and a protective layer is reserved, aiming at the poor permeability difference of the floor rock mass caused by the drainage curtain grouting, the seepage pressure is monitored through the advanced drilling, the high-porosity water pressure area is delimited as the encryption shock absorption area, the spacing between the shock absorption holes is reduced in the area and the quincunx arrangement is adopted to form a local stress dissipation network, the depth of the shock absorption hole requires penetrating the protective layer to a certain depth below the bedrock, the hole is filled with water permeable material to simultaneously realize the vibration wave scattering and the pore water drainage, and the drainage pressure relief hole is additionally arranged as necessary according to the real-time monitoring data. Compared with the closest prior art, the traditional floor blasting often ignores the coupling effect of the seepage field and the stress field, and the protection of the foundation rock mass is insufficient. The propagation of the blasting vibration wave to the key bearing rock mass is effectively blocked, and the damage risk of the blasting to the floor rock mass is significantly reduced through the drainage of the pore water pressure, so that the long-term stability and integrity of the floor are ensured According to one of the embodiments of the present application, it further comprises a reliability guarantee system for detonation in a water permeable environment: In the drainage curtain construction section, the blasting network adopts a double-loop non-electric detonation tube system, the main loop is laid along the high position of the wall, and the standby loop is laid along the inner wall of the drill hole; All detonation tube joints are wrapped with water-repellent buffer mortar, and a waterproof sealing cover is additionally installed outside the detonator; For the top arch dripping area, a quick-setting waterproof coating capsule is sleeved outside the detonating charge, which can form a sealed protective layer within 10 seconds after encountering water.

[0046] In the drainage curtain construction section, the blasting network adopts a double-loop non-electric detonation tube system, the main loop is laid along the high position of the wall to avoid water accumulation, and the standby loop is laid along the inner wall of the drill hole as a redundant guarantee, all detonation tube joints are wrapped with water-repellent buffer mortar to prevent moisture, and a waterproof sealing cover is additionally installed outside the detonator, for the top arch dripping area, a quick-setting waterproof coating capsule is sleeved outside the detonating charge, which can form a sealed protective layer after encountering water. Compared with the closest prior art, the traditional method usually adopts a single loop and the waterproof measures are simple and crude, which cannot cope with the extreme conditions of continuous water seepage and accidental soaking. The reliability of the detonation network in a humid or dripping environment is greatly improved, ensuring the success rate and construction safety of the blasting operation.

[0047] According to one of the embodiments of the present application, it further comprises the following steps: The micro-expansion quick-setting resin high-strength prestressed anchor rod is arranged in a ring shape on the excavated side at the interface between adjacent excavation layers, the high-strength prestressed anchor rod is inclined downward at an angle of 10°-15° and penetrates into the unexcavated rock mass of the lower layer by 3-5 meters, which is used to enhance the interlayer bonding and overall stability; The prestress compensation system is installed within 24 hours after each layer is excavated, the system includes a hydraulic jack and a pressure sensor, and the high-strength prestressed anchor rod tension is dynamically adjusted according to the surrounding rock convergence monitoring data; When the sidewall convergence rate exceeds 0.5 mm / d, the automatic compensation mode is started, and the prestress of the high-strength prestressed anchor rod is increased to 120%-150% of the design value. For the water seepage section of the drainage curtain, the free section of the high-strength prestressed anchor rod is wrapped with a water-permeable resin filter membrane, and the permeability coefficient is kept greater than or equal to 1*10 -3 cm / s, and stress transmission and pore water pressure dissipation are simultaneously achieved.

[0048] At the interface between adjacent excavation layers, the high-strength prestressed anchor rod is arranged on the excavated side in a ring shape, and the high-strength prestressed anchor rod is inclined downward into the unexcavated rock mass of the lower layer to a certain depth, which is used for pre-anchoring and enhancing the interlayer combination. A prestress compensation system containing a hydraulic jack and a pressure sensor is installed within a specified time after each layer is excavated. The system can dynamically adjust the tension of the high-strength prestressed anchor rod according to the surrounding rock convergence monitoring data. When the sidewall convergence rate exceeds a set threshold, the compensation mode is automatically started to increase the prestress of the high-strength prestressed anchor rod. For the water seepage section of the drainage curtain, the free section of the high-strength prestressed anchor rod is wrapped with a water-permeable resin filter membrane, which effectively dissipates pore water pressure while transmitting stress. Compared with the closest prior art, the traditional method is passive reinforcement after deformation occurs, and the interlayer anchoring and seepage pressure control are independent of each other. Active and collaborative control of interlayer deformation and seepage pressure is achieved, which significantly improves the overall stability of the high sidewall during the excavation process.

[0049] According to one embodiment of the present application, a vibration monitoring and protection system is arranged in a ring shape on the inside of the completed support sidewall: A distributed vibration sensor network is installed every 5 meters along the tunnel axis direction to real-time collect the blasting vibration velocity and frequency components; A blasting vibration cumulative damage model is established, and when the rock mass damage factor D is greater than 0.25, a self-advancing hollow grouting anchor rod is implemented in the damage area before the next cycle of blasting, and the anchor rod length penetrates the current excavation layer and penetrates the lower layer rock mass by 2 meters; For the influence area of the drainage curtain, a water-permeable polyurethane foam cushion layer is laid between the support layer and the surrounding rock, and the dynamic elastic modulus is controlled in the range of 0.5-1.0 GPa, and vibration wave scattering and water seepage drainage are simultaneously achieved.

[0050] Distributed vibration sensor network is installed along the hole axis direction at certain intervals to collect blasting vibration velocity and frequency components in real time, to establish a blasting vibration cumulative damage model for quantitative evaluation, and to implement advanced reinforcement by densifying self-advancing hollow grouting anchor in the damage area before the next cycle of blasting when the monitored rock mass damage factor exceeds the critical value. The anchor length penetrates the current excavation layer and extends into the underlying rock mass. For the influence area of drainage curtain, a specific dynamic elastic modulus range of water-permeable polyurethane foam cushion is laid between the support layer and the surrounding rock. Compared with the closest prior art, the traditional method mainly relies on experience and post-processing, and cannot provide early warning and active protection for invisible cumulative damage. Real-time monitoring, quantitative evaluation and active protection of blasting vibration cumulative damage are achieved, effectively protecting the long-term integrity of the surrounding rock and the initial support structure.

[0051] Although embodiments of the present application have been disclosed in connection with the above description and the accompanying drawings, it should be understood that they are not intended to limit the application to the specific form set forth, but on the contrary, it is intended to cover all modifications, equivalents and alternatives falling within the spirit and scope of the application as defined by the appended claims.

Claims

1. A method for blasting excavation using an air cushion pressure regulating chamber, characterized in that, Includes the following steps: The controlled atmosphere chamber is excavated vertically into 5 layers, from top to bottom: the first layer is the top arch layer, the second layer is the upper side wall, the third layer is the middle side wall, the fourth layer is the lower side wall, and the fifth layer is the bottom slab layer. The first layer adopts the construction procedure of first excavating the central pilot tunnel and then expanding the excavation to both sides. The central pilot tunnel is first excavated along the tunnel axis, and then the excavation is expanded to both sides. Before the construction of the first layer of the top arch layer, drainage holes were drilled and grouting was carried out in the area of ​​water seepage fissures to form a drainage curtain, thereby reducing the seepage pressure of the surrounding rock. Layers II, III, and IV are excavated in half-width manner, with one side being excavated first and the other side being excavated after the support is completed; Layer V is excavated using half-width horizontal light blasting, with a protective layer reserved; After each layer is excavated, systematic anchor spraying support is immediately carried out to ensure the stability of the surrounding rock before proceeding to the next layer.

2. The air-cushion type pressure regulating chamber blasting excavation method as described in claim 1, characterized in that, The blasting of the pilot tunnel employs a staged charge structure: The slotted hole uses a continuously loaded explosive cartridge with a diameter of 35-40mm to form an effective free surface; The rock fragmentation size is controlled by continuously loading explosive cartridges with a diameter of 28-32mm into the collapse hole. The peripheral holes are filled with non-coupled drug cartridges with a diameter of 20-25mm at intervals; For the drainage curtain grouting reinforcement area, buffer holes are added between the slotted holes and the surrounding holes, and a shock-absorbing charge structure with a 30% to 50% reduction in linear charge density is adopted.

3. The air cushion type pressure regulating chamber blasting excavation method as described in claim 2, characterized in that, The installation of buffer holes and the application of shock-absorbing explosives include the following operations: In the drainage curtain grouting area, a row of buffer holes is arranged in parallel at a distance of 0.8 to 1.2 meters outside the excavation outline, with the hole spacing being 1.2 to 1.5 times that of the collapse holes; The use of bamboo blanks to fix small-diameter medicine rolls in an intermittent loading structure reduces the density of linear medicine loading by 30% to 50% compared to the method of using a chipping hole. The detonation sequence is set to a four-stage micro-differential detonation: slotted hole, collapse hole, buffer hole, and peripheral hole, with a delay time of more than 50 milliseconds between adjacent segments; The charge density in the buffer holes is dynamically adjusted based on the strength test results of the rock core samples taken from the grouting area: when the uniaxial compressive strength increases by more than 40%, the charge density is reduced by 50%; when the increase is between 20% and 40%, it is reduced by 30%.

4. The air cushion type pressure regulating chamber blasting excavation method as described in claim 1, characterized in that, Differentiated charge strategy was adopted for the sidewall excavation blasting: The main collapse zone uses a continuous charge structure to ensure that the rock is fully broken. The main collapse zone refers to the blasting area more than 1.5 meters away from the design outline. The contour control zone uses spaced, decoupled explosive charges to reduce damage to the forming surface. The contour control zone refers to the area 0.3 to 1.5 meters away from the design contour line. The intensity abrupt change zone is located at the boundary between the high-intensity zone and the low-intensity zone, extending 2 to 3 meters wide along the outline. Variable density charging is implemented within this zone: the charging density in the high-intensity zone is reduced by 30% to 40% of the baseline value, while the low-intensity zone maintains the baseline charging density. The charging boundary line dynamically shifts according to the curtain grouting diffusion radius, with the shift controlled within 0.3 to 0.5 meters. The high-intensity zone is the core influence area of ​​the drainage curtain grouting, where its uniaxial compressive strength is increased by more than 40% compared to the original rock mass, and its boundary is determined by core sampling strength testing. The low-intensity zone is the original rock mass area not covered by the drainage curtain.

5. The air cushion type pressure regulating chamber blasting excavation method as described in claim 1, characterized in that, Energy gradient release control is implemented in half-width excavation and blasting: The main blasting zone employs continuous charging to achieve efficient rock mass fracturing; The pre-splitting zone uses intermittent, decoupled explosive charges to create a smooth fracture surface; A transition hole row is added between the pre-splitting hole and the main blasting hole, and a linear charge density between the main blasting hole and the pre-splitting hole is adopted to form a stress transmission buffer zone.

6. The air cushion type pressure regulating chamber blasting excavation method as described in claim 5, characterized in that, The implementation of the transition hole array includes the following operations: A single row of transition holes is arranged along the parallel contour line between the pre-splitting hole and the main blasting hole, with a distance of 0.6 to 0.8 meters from the pre-splitting hole and 0.4 to 0.6 meters from the main blasting hole; The structure uses bamboo blanks to fix the explosive cartridges at intervals, and the density of the linear explosive charge is 50% to 70% of that of the main blast hole. The detonation sequence is set to a three-stage micro-delay detonation of pre-splitting hole, transition hole, and main detonation hole, with an inter-stage delay of more than 30 milliseconds.

7. The air cushion type pressure regulating chamber blasting excavation method as described in claim 1, characterized in that, Blasting of the base layer protective layer to control rock mass integrity: Horizontal blasting technology is used to reduce damage to the base plate caused by blasting vibration; A protective layer is reserved to absorb the impact of blasting energy; In areas with active seepage, denser vibration damping holes should be installed. The installation of the dense vibration damping holes includes the following steps: By monitoring the seepage pressure through advanced borehole drilling, areas with pore water pressure > 0.2 MPa are designated as dense vibration reduction zones; The spacing between damping holes in the reference area is 1.0 meter. The spacing between holes in the encrypted damping zone is reduced to 0.5 meters, and they are arranged in a quincunx pattern to form a stress dissipation network; The shock-absorbing holes penetrate the protective layer to 0.5 meters below the bedrock, and are filled with permeable sand and gravel. When the real-time monitoring of the seepage pressure value rises above 0.3 MPa, drainage and pressure relief holes are added in the center of the plum blossom-shaped perforated mesh.

8. The air cushion type pressure regulating chamber blasting excavation method as described in claim 1, characterized in that, It also includes a detonation reliability assurance system for water-permeable environments: In the drainage curtain construction section, the blasting network adopts a dual-circuit non-electric detonating cord system, with the main circuit laid high along the tunnel wall and the backup circuit laid along the inner wall of the borehole. All detonating cord joints are wrapped with water-repellent buffer sealant, and a waterproof sealing cover is installed on the outside of the detonator. For the dripping area of ​​the top arch, a quick-setting waterproof coating capsule is installed on the outside of the detonation charge, which forms a sealed protective layer within 10 seconds of contact with water.

9. The air cushion type pressure regulating chamber blasting excavation method as described in claim 1, characterized in that, It also includes the following steps: At the interface of adjacent excavated layers, micro-expansion rapid-curing resin high-strength prestressed anchors are circumferentially installed on the excavated side. The high-strength prestressed anchors are inclined at an angle of 10°-15° and penetrate 3-5 meters into the lower unexcavated rock mass. A prestressing compensation system is installed within 24 hours after each layer is excavated. The system includes hydraulic jacks and pressure sensors, and dynamically adjusts the tension of high-strength prestressed anchor bolts based on the surrounding rock convergence monitoring data. When the convergence rate of the sidewall exceeds 0.5 mm / d, the automatic compensation mode is activated to increase the prestress of the high-strength prestressed anchor to 120%-150% of the design value. For seepage sections of the drainage curtain, a permeable resin filter membrane is wrapped around the free section of the high-strength prestressed anchor bolt, maintaining a permeability coefficient ≥1×10⁻⁶. -3 cm / s.

10. The air-cushion type pressure regulating chamber blasting excavation method as described in claim 1, characterized in that, A vibration monitoring and protection system is installed circumferentially on the inner side of the already supported sidewall: A distributed vibration sensor network is installed every 5 meters along the tunnel axis to collect the blasting vibration velocity and frequency components in real time. Establish a cumulative damage model for blasting vibration. When the rock mass damage factor D > 0.25 is monitored, densified self-propelled hollow grouting anchors are implemented in the damaged area before the next blasting cycle. The anchor length penetrates the current excavation layer and extends 2 meters into the lower rock mass. For the area affected by the drainage curtain, a permeable polyurethane foam pad is laid between the support layer and the surrounding rock, and its dynamic elastic modulus is controlled within the range of 0.5-1.0 GPa.