Method for constructing a prefabricated shaft structure

Abstract

The application discloses a construction method of an assembled shaft structure and belongs to the technical field of underground engineering and building construction. In view of the problems of low construction efficiency, poor quality controllability, insufficient structural integrity and waterproof performance of a traditional shaft, the main body of the shaft is divided into multiple hollow square prefabricated components, which are hoisted and assembled one by one from bottom to top, the adjacent square prefabricated components are matched through tenon and mortise, are positioned through positioning pin rods inserted into reserved holes, are locked and fixed through bent bolts penetrating through embedded steel corrugated pipes, waterproof rubber sealing pads are arranged at joints, and grouting holes and exhaust holes are embedded, grouting is carried out on the joints after assembly, an assembled shaft main body is formed, and finally, grouting is carried out on the gap behind the wall. The application is mainly applied to the construction of shaft structures of urban underground space, mines, tunnel ventilation and various vertical passage projects.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering and building construction technology, and specifically relates to a construction method for a prefabricated vertical shaft structure. Background Technology

[0002] Vertical shafts are widely used in underground engineering, such as urban underground space development, mining, and tunnel ventilation. Traditional shaft construction methods mainly rely on cast-in-place concrete technology and early prefabrication technology, which have the following prominent problems and limitations in practical applications.

[0003] The construction process of cast-in-place concrete shafts has the following problems: (1) Long construction cycle and low efficiency: It requires multiple cyclical processes such as formwork, steel bar binding, concrete pouring, curing, and formwork removal. The construction speed is constrained by the concrete setting and hardening time, and rapid construction cannot be achieved. (2) Large fluctuations in project quality: On-site operations are significantly affected by weather, environment, and manual operation level. The density, uniformity, and overall quality of concrete are difficult to be stably and accurately controlled, and common quality defects such as cracks and leakage are easy to occur. (3) Large environmental impact and resource consumption: On-site wet operations generate a large amount of construction waste, noise, and dust, which is not friendly to the surrounding environment. At the same time, the formwork and support system consume a lot of materials and have a low turnover rate, which does not meet the requirements of green construction and sustainable development. (4) High operational safety risks: The cast-in-place construction of deep shafts is a high-risk operation. Personnel need to work in narrow deep foundation pits for a long time and face safety threats such as falling from heights, being struck by objects, and collapse.

[0004] The traditional prefabricated shaft construction process has the following problems: (1) Insufficient structural integrity and waterproof performance: The simple block prefabrication, on-site bolt connection or grouting connection adopted in the early stage has weak connection nodes between components, making it difficult to form an overall rigidity and reliable water-stopping system equivalent to the cast-in-place structure. Under complex water and soil pressure and seismic action, it is easy to become a weak link in structural safety and seepage prevention. (2) Stringent construction accuracy requirements and poor fault tolerance: The requirements for the dimensional accuracy of prefabricated components and the accuracy of on-site hoisting and positioning are extremely high. Once cumulative errors occur, it will lead to assembly difficulties and even secondary processing, affecting the construction progress and quality. (3) Limited adaptability and flexibility: The size and form of traditional prefabricated components are relatively fixed, making it difficult to flexibly adapt to the needs of shaft projects with different geological conditions, diameters and depths, and the design versatility is not strong. (4) Immature vertical bearing and connection technology: The shaft structure mainly bears vertical pressure and lateral soil pressure. The existing horizontally developed prefabricated technology (such as the socket connection used for pipe gallery) often cannot be directly and effectively transformed into a safe and reliable vertical force bearing and connection system.

[0005] Therefore, developing a prefabricated shaft structure and its supporting construction method that is fast, efficient, quality-controllable, environmentally friendly, safe, reliable, and achieves good integrity and excellent waterproof performance has become a key technical problem urgently needing to be solved in this field. This invention aims to overcome the shortcomings of the prior art and provide an innovative solution. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of long construction period, uncontrollable quality, high safety risk and great environmental impact.

[0007] The purpose of this invention is to provide a construction method for a prefabricated shaft structure, comprising the following steps: S1: The underground excavation method is adopted to complete the excavation of the straight section at the bottom of the shaft for connecting the main structure and the secondary lining structure. S2: The inverted shaft wall method is adopted for construction, and the vertical shaft body is excavated to the top of the straight section of the underground excavation, so that the shaft body is connected to the straight section of the underground excavation. S3: The main body of the shaft is divided longitudinally into multiple hollow square prefabricated components. During assembly, each square prefabricated component is hoisted into the shaft body one by one from bottom to top. Adjacent square prefabricated components are connected by tenons and mortises. The tenon is set on the end face of one square prefabricated component, and the mortise is set on the corresponding end face of the adjacent square prefabricated component. The tenon has a first reserved hole, and the mortise has a second reserved hole corresponding to the first reserved hole. Positioning is achieved by inserting positioning pins into the first and second reserved holes. Adjacent square prefabricated components are locked and fixed by passing bent bolts through the corrugated steel pipes embedded in the square prefabricated components. Waterproof rubber sealing gaskets are set at the joints between longitudinally adjacent square prefabricated components. Grouting holes and venting holes are also embedded at the joints. After assembly, grouting is performed on the joints through the grouting holes to make the joints tight and form the prefabricated shaft body. S4: After the prefabricated shaft body is formed, grouting is performed on the gap between the outer wall of the shaft and the surrounding soil.

[0008] Preferably, in the construction method of the prefabricated shaft structure, in step S3, the joint between longitudinally adjacent square prefabricated components is divided into several independent grouting chambers, and each grouting chamber is independently equipped with grouting holes and venting holes.

[0009] Preferably, in the construction method of the prefabricated shaft structure, in step S3, the grout used for grouting the joint is epoxy resin grout. The epoxy resin grout is made by mixing liquid A and liquid B in a mass ratio of 3:1. Liquid A is modified epoxy resin, and liquid B is modified amine. Quartz powder is added to the epoxy resin grout, and the mass ratio of the sum of the masses of liquid A and liquid B to the mass of quartz powder is 1:0.5.

[0010] Preferably, in the construction method of the prefabricated shaft structure, in step S3, when grouting the joint, the grouting pressure is 0.4 MPa, the grouting speed is controlled at 300-350 kg / h, and the grouting time of each grouting chamber is no more than 45 minutes.

[0011] Preferably, in the construction method of the prefabricated shaft structure, in step S3, when hoisting the square prefabricated component, a distance sensor is installed on the hoisting equipment to monitor the distance between the outer wall of the square prefabricated component and the shaft wall in real time during the lowering process; when the monitored distance is less than the preset safety distance, the lowering speed of the hoisting equipment is reduced until the monitored distance is greater than or equal to the preset safety distance, and then the lowering continues at the current lowering speed.

[0012] Preferably, in the construction method of the prefabricated shaft structure, in step S3, at least three distance sensors are evenly installed circumferentially on the lifting device. Each distance sensor is used to monitor the distance between the outer wall of the square prefabricated component and the shaft wall in different directions. When the distance in any direction is less than the preset safety distance, the lowering speed of the lifting device is reduced until the distance in all directions is greater than or equal to the preset safety distance, and then the lowering continues at the current lowering speed.

[0013] Preferably, in the construction method of the prefabricated shaft structure, in step S3, the preset safety distance is determined based on the one-sided gap between the outer wall of the square prefabricated component and the shaft wall, and the preset safety distance is set to 1 / 3 of the one-sided gap; wherein, the one-sided gap is equal to the difference between the inner diameter of the shaft body and the outer diameter of the square prefabricated component, and then divided by 2.

[0014] Preferably, in the construction method of the prefabricated shaft structure, in step S4, when grouting the gap between the outer wall of the shaft and the surrounding soil, the gap is divided into multiple grouting sections along the longitudinal direction of the shaft. The height of each grouting section is equal to the height of one or more square prefabricated components. Grouting is carried out section by section from bottom to top. After each section is completed, the grout solidifies until the compressive strength reaches more than 70% of the design value before the adjacent section is grouted.

[0015] Preferably, in the construction method of the prefabricated shaft structure, in step S4, When performing backfill grouting for each grouting section, an intermittent grouting process is adopted, including the following steps: Step A: Inject a first set amount of grout at the first grouting pressure, then pause grouting to allow the injected grout to initially fill the gap behind the wall and expel air bubbles; Step B: Inject a second set amount of grout at a second grouting pressure, wherein the second grouting pressure is greater than the first grouting pressure; Step C: Repeat the pause grouting operation in Step A and the grouting operation in Step B until the total grouting volume of the grouting section reaches the theoretical grouting volume; The sum of the first set amount and the second set amount is equal to the theoretical grouting amount, or the first set amount accounts for 30% to 50% of the theoretical grouting amount, and the remaining amount is injected in batches as the second set amount.

[0016] Preferably, in the construction method of the prefabricated shaft structure, in step S4, the grout pressure in the gap behind the wall is monitored in real time each time grouting is paused. When the grout pressure drops to a preset pressure value, the pause ends and the next grouting begins; the preset pressure value is less than the first grouting pressure.

[0017] The present invention has at least the following beneficial effects: This invention divides the main body of a vertical shaft longitudinally into multiple hollow square prefabricated components, employing a construction mode of factory prefabrication and on-site modular assembly. This avoids the formwork, rebar tying, curing, and formwork removal processes required for cast-in-place concrete, thus shortening the construction cycle. Through tenon and mortise joint connections, positioning pins inserted into pre-drilled holes for positioning, bent bolts for locking, and grouting of joints for tightness, the prefabricated shaft body forms an integral load-bearing structure. On-site assembly reduces the number of personnel and working time in the deep foundation pit, lowering safety risks such as falls from heights and collapses. Factory prefabrication reduces construction waste, noise, and dust generated by on-site wet work, achieving green construction.

[0018] This invention divides the joints between longitudinally adjacent square precast components into several independent grouting chambers. Each grouting chamber has its own independent grouting hole and vent hole. Adjacent grouting chambers are not interconnected or intersecting, thus achieving independent grouting of the joints in different zones. During the grouting process, the grout is confined within its own independent grouting chamber, avoiding the problem of incomplete filling caused by grout cross-flow during long-distance joint grouting. Independent grouting in each chamber allows for control of grouting pressure and volume according to actual conditions, ensuring that all joint areas are fully filled. This improves the density and uniformity of the grouting, guaranteeing the structural integrity and waterproofing reliability.

[0019] This invention utilizes epoxy resin grout as a joint grouting material. It is composed of modified epoxy resin component A and modified amine component B mixed in a 3:1 mass ratio, with quartz powder incorporated into the grout. The total mass ratio of component A and component B to quartz powder is 1:0.5, forming a grout suitable for low-temperature environments. This grout maintains a suitable viscosity at 5°C, has a workable time that meets construction requirements, and gradually develops strength after curing. The addition of quartz powder adjusts the grout's fluidity, prevents sedimentation, and improves the grout's compactness. This grout can fully fill joint gaps at low temperatures, forming a reliable bonding layer after curing, ensuring the joint's mechanical properties and waterproofing effect.

[0020] This invention limits the key process parameters of joint grouting: the grouting pressure is 0.4 MPa, the grouting speed is controlled at 300–350 kg / h, and the grouting time for each grouting chamber is no more than 45 minutes. The grouting pressure of 0.4 MPa ensures that the grout can overcome the joint resistance and fully fill the gap between the tenon and mortise; the grouting speed of 300–350 kg / h avoids grout turbulence and air bubble entrainment caused by excessive speed, and also avoids initial setting of the grout during the grouting process caused by excessively slow speed; the grouting time for each grouting chamber is no more than 45 minutes, ensuring that the grouting operation is completed within the operable time of the grout, preventing the grout from solidifying during the grouting process, and guaranteeing grouting quality and construction efficiency.

[0021] This invention utilizes a distance sensor mounted on the lifting device to monitor the distance between the outer wall of the precast square component and the manhole wall in real time during the lowering process. When the detected distance falls below a preset safety distance, the lowering speed of the lifting equipment is promptly reduced to decrease the component's sway amplitude and gradually bring it back to its normal position. Lowering continues at the current speed once the detected distance returns to a safe range. This proactive control of the lowering speed prevents the component from colliding with the manhole wall due to excessive swaying during lifting, protecting the component from damage. It also ensures the continuity and efficiency of the lifting operation without requiring complex hardware modifications to the lifting equipment.

[0022] This invention achieves omnidirectional monitoring of the gap between the precast square component and the manhole wall by uniformly arranging at least three distance sensors circumferentially on the lifting equipment's lifting device. Each distance sensor monitors the distance between the outer wall of the precast square component and the manhole wall in different directions. When the distance in any direction is less than a preset safety distance, the lowering speed is reduced until the distance in all directions returns to the safe range, after which the lowering continues at the current speed. This solution eliminates the blind spots inherent in single-direction monitoring, ensuring that any deviation of the component in any direction can be detected and triggered in a timely manner, effectively preventing the component from colliding with the manhole wall in the unmonitored direction and improving the safety of the lifting process.

[0023] This invention establishes a reasonable control threshold by determining the preset safety distance based on the one-sided gap between the outer diameter of the square prefabricated component and the inner diameter of the well body, and setting it to 1 / 3 of the one-sided gap. This setting method correlates the timing of triggering deceleration with the actual gap between the component and the well wall. The preset safety distance is smaller than the one-sided gap, ensuring that speed adjustment is triggered before the component's swing amplitude reaches the point of colliding with the well wall, thus creating a safety margin. The 1 / 3 ratio balances safety and construction efficiency, avoiding the risk of late triggering and collision after deceleration due to an excessively small preset safety distance, and also avoiding the problem of frequent deceleration triggering and reduced construction efficiency due to an excessively large preset safety distance, making the control logic more reasonable.

[0024] This invention employs layered control of the grouting behind the wall, dividing the gap along the vertical shaft into multiple grouting sections. The height of each grouting section is equal to the height of one or more square precast components, and grouting is carried out segment by segment from bottom to top. After each section is completed, the grout is allowed to solidify until its compressive strength reaches more than 70% of the design value before the next adjacent section is grouted. Layered grouting avoids the problem of incomplete filling caused by excessive grouting height at once, ensuring that the grout in each section uniformly fills the gap behind the wall. Allowing the grout to solidify before grouting the next section avoids lateral pressure from unsolidified grout on the assembled components, preventing component deformation or displacement, and ensuring structural stability and the quality of the grouting behind the wall.

[0025] This invention employs an intermittent grouting process for each grouting section. First, a first predetermined amount of grout is injected at a first grouting pressure. Grouting is then paused to allow the injected grout to initially fill the gaps behind the wall and expel air bubbles. Next, a second predetermined amount of grout is injected at a second grouting pressure (greater than the first), and this pause and grouting process is repeated until the total grout volume reaches the theoretical grouting volume. The low-pressure grouting stage allows the grout to slowly fill the gaps, avoiding air bubbles and turbulence generated by high-speed grouting. The pause stage allows the grout to settle, allowing air bubbles to rise and be expelled, and the gaps to be initially filled. The high-pressure grouting stage further densifies the grout, ensuring no voids. Through layer-by-layer filling and densification, the uniformity and density of the grouting behind the wall are improved.

[0026] This invention monitors the grout pressure within the gap behind the wall in real time during each grouting pause. The pause ends when the grout pressure drops to a preset value, which is lower than the first grouting pressure. During the air bubble discharge process, the grout pressure continuously decreases. When the pressure drops to the preset value, it indicates that the air bubbles have been largely discharged, at which point the pause ends and the next grouting cycle begins. This scheme links the pause time to the air bubble discharge status, using pressure monitoring for quantitative judgment. This avoids the uncertainty of relying on experience to determine the pause time, ensuring both sufficient air bubble discharge and dense grouting, while preventing excessively long pauses that could affect construction efficiency. This achieves precise control of the pause duration for intermittent grouting.

[0027] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the prefabricated shaft structure provided by the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of the upper surface of the square prefabricated component provided by the present invention.

[0030] Figure 3This is a schematic diagram of the lower surface of the square prefabricated component provided by the present invention.

[0031] Figure 4 This is a structural schematic diagram of two adjacent square prefabricated components provided by the present invention.

[0032] Figure 5 This is a schematic diagram of the vent hole between two adjacent square prefabricated components provided by the present invention.

[0033] Figure 6 This is a schematic diagram of the positioning pin between two adjacent square prefabricated components provided by the present invention.

[0034] Reference numerals: 1. Square precast component; 2. Grouting hole; 3. First reserved hole; 4. Grouting chamber; 5. Tenon; 6. Waterproof rubber sealing gasket; 9. Positioning pin; 11. Second reserved hole; 12. Mortise and tenon; 13. Vent hole; 14. Bent bolt. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0036] like Figures 1 to 6 As shown, the present invention provides a construction method for a prefabricated vertical shaft structure, comprising the following steps: S1: The underground excavation method is adopted to complete the excavation of the straight section at the bottom of the shaft for connecting the main structure and the secondary lining structure. S2: The inverted shaft wall method is adopted for construction, and the vertical shaft body is excavated to the top of the straight section of the underground excavation, so that the shaft body is connected to the straight section of the underground excavation. S3: The main body of the shaft is divided longitudinally into multiple hollow square prefabricated components 1. During assembly, each square prefabricated component 1 is hoisted into the shaft body one by one from bottom to top. Adjacent square prefabricated components are connected by tenons 5 and mortises 12. The tenon 5 is set on the end face of one square prefabricated component, and the mortises 12 are set on the corresponding end faces of adjacent square prefabricated components. The tenon has a first reserved hole 3, and the mortises 12 have a second reserved hole 11 corresponding to the first reserved hole. Positioning is achieved by inserting positioning pins 9 into the first reserved hole 3 and the second reserved hole 11. Adjacent square prefabricated components are locked and fixed by passing bent bolts 14 through the steel corrugated pipes embedded in the square prefabricated components. Waterproof rubber sealing gaskets 6 are set at the joints between longitudinally adjacent square prefabricated components. Grouting holes 2 and venting holes 13 are also embedded at the joints. After assembly, grouting is performed on the joints through the grouting holes to make the joints tight and form the prefabricated shaft body. S4: After the prefabricated shaft body is formed, grouting is performed on the gap between the outer wall of the shaft and the surrounding soil.

[0037] The prefabricated shaft structure construction method of the present invention first involves step S1, employing the mining method of underground excavation to complete the excavation of the straight section at the bottom of the shaft, which serves as the connection to the main structure, and the secondary lining structure. Specifically, at the designed bottom location of the shaft, the mining method is used to excavate a straight horizontal tunnel section. The cross-sectional dimensions of the tunnel are determined according to the requirements of the main structure. After excavation, a secondary lining structure is constructed within the tunnel to form a stable and permanent structure. One end of this straight underground excavation section connects to the bottom of the shaft body constructed subsequently, while the other end connects to the underground main structure, serving as a transitional connection between the shaft and the main structure.

[0038] After completing S1, proceed to step S2, using the inverted shaft wall method to excavate the vertical shaft above the straight section of the underground excavation, connecting the shaft to the straight section. In practice, the vertical shaft is excavated in sections from the surface downwards. After each section is excavated to a certain depth, a shaft wall support structure is promptly constructed to prevent collapse. Using the inverted shaft wall method, excavation proceeds from top to bottom, with each section followed by the construction of a reinforced concrete shaft wall to form a temporary support structure. This process is repeated until the shaft reaches above the completed straight section of the underground excavation, connecting the shaft to the straight section and creating a complete vertical shaft excavation space.

[0039] After the well body excavation is completed, step S3 is performed to hoist and assemble the prefabricated shaft. The main body of the shaft is divided longitudinally into multiple hollow square prefabricated components, each of which is prefabricated in the factory. During prefabrication, tenons or mortises are set on the end faces of the square prefabricated components. The tenon is set on the end face of one square prefabricated component, and the mortis is set on the corresponding end face of the adjacent square prefabricated component. A first reserved hole is set in the tenon, and a second reserved hole corresponding to the first reserved hole is set in the mortis. Corrugated steel pipes are pre-embedded inside the square prefabricated components on the non-contact side for inserting bent bolts. Grouting holes and venting holes are pre-embedded at the joints of the square prefabricated components, with the grouting holes set at the lower end of the joint and the venting holes set at the upper end of the joint.

[0040] During assembly, hoisting equipment is used to lift the square prefabricated components one by one into the shaft from bottom to top. First, the bottommost square prefabricated component is hoisted to the bottom of the shaft, aligning it with the secondary lining structure of the straight section excavated in the cut-and-cover mine. During hoisting, precise positioning is achieved by inserting locating pins into the first and second pre-drilled holes. The locating pins are spindle-shaped, with the diameters at both ends smaller than the diameter at the middle, guiding the alignment of adjacent square prefabricated components. Adjacent square prefabricated components are connected by tenons and mortises, achieving initial alignment.

[0041] After positioning, bent bolts are used to pass through the pre-embedded corrugated steel pipes inside the square precast components and lock and fix the adjacent square precast components. The bent bolts are set on the non-soil-adjacent side of the components and evenly distributed in the middle of the span. Waterproof rubber gaskets are installed at the joints between longitudinally adjacent square precast components. During assembly, the gaskets are compressed to form the first waterproof measure for the joints.

[0042] After assembly, grouting is performed on the joints through pre-embedded grouting holes. During grouting, grout is injected through the grouting holes and flows along the joint gaps. Air inside the joint is expelled through the vent holes until grout is discharged from the vent holes, at which point grouting stops, ensuring the joint is sealed. After grouting is completed, the grouting holes and vent holes are sealed with sealing material. At this point, the main body of the prefabricated shaft is formed.

[0043] Finally, in step S4, after the prefabricated shaft body is formed, grouting is performed on the gap between the outer wall of the shaft and the surrounding soil. During grouting, the grouting pipe is inserted into the gap between the outer wall of the shaft and the soil, and grout is injected to fill the gap, making the shaft and the surrounding soil form a whole, thus enhancing the stability and waterproof performance of the shaft.

[0044] This invention divides the main body of a vertical shaft into multiple square prefabricated components, employing a construction mode of factory prefabrication and on-site assembly. The prefabricated components are produced in a high-standard factory environment, ensuring high precision and uniform quality, thus avoiding common quality defects caused by wet on-site work. During construction, positioning pins, bolt locking, and joint grouting are used to create a unified load-bearing structure for the prefabricated vertical shaft. On-site assembly reduces the number of workers and working time in deep foundation pits, lowering safety risks. The site is dust-free, noise-free, and generates minimal construction waste, achieving green construction. This invention transforms vertical shaft engineering from on-site construction to a factory manufacturing plus on-site assembly construction mode, improving construction efficiency, project quality, construction safety, and environmental protection.

[0045] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S3, the joint between longitudinally adjacent square prefabricated components is divided into several independent grouting chambers 4, and each grouting chamber is independently equipped with grouting holes and venting holes.

[0046] During the actual construction, in the prefabrication stage of the square precast components, based on the design length of the joint and the grouting process requirements, the joint between longitudinally adjacent square precast components is divided circumferentially into multiple independent grouting chambers. These grouting chambers are not interconnected or intersecting, forming independent closed spaces. Each grouting chamber is independently equipped with an injection hole and an vent hole. The injection hole is located at the lower end of the joint within that chamber, and the vent hole is located at the upper end. To achieve independent sealing between the grouting chambers, a radial dividing groove can be installed at regular intervals along the circumference at the end face joint of the square precast component. Water-swellable rubber strips or plastic spacers are embedded in the groove. This dividing groove intersects with the waterproof rubber sealing gasket, dividing the joint into multiple non-interconnected fan-shaped chambers. An injection hole is pre-embedded at the lowest point of each chamber, and an vent hole is pre-embedded at the highest point.

[0047] After the prefabricated square components are assembled to form the main body of the prefabricated shaft, grouting is carried out at the joints. During grouting, each grouting chamber is grouted independently. Taking one grouting chamber as an example, the grouting equipment is connected to the grouting hole, and grout is injected into the chamber through the hole. During grouting, the grout gradually fills the joint space within the chamber from the bottom to the top, and air inside the chamber is expelled through the vent. When grout is expelled from the vent, it indicates that the joint in that chamber has been completely filled with grout; grouting is then stopped, and the grouting hole and vent are sealed with sealing material. After grouting one chamber is completed, the same grouting operation is performed on the other chambers in sequence until the joints of all chambers are grouted.

[0048] Because the grouting chambers are not interconnected, each chamber is grouted independently, and the grout is confined within its own chamber, preventing cross-contamination to adjacent chambers. The grouting pressure and volume for each chamber can be controlled separately according to the actual conditions of that section, ensuring that all joints in each area are fully filled.

[0049] One approach is to use integral joint grouting, which involves setting one or a few grouting holes throughout the joint between longitudinally adjacent square precast components, and injecting grout into the entire joint through these holes. However, due to the large length of the joint, cross-flow of the grout can easily occur, resulting in incomplete filling in some areas and excessive grout in others. This can lead to voids or uneven filling within the joint after grouting, affecting its mechanical properties and waterproofing effectiveness. Furthermore, it is impossible to control the grouting pressure and volume in different areas during the entire joint grouting process, making it difficult to guarantee the grouting quality in each area of ​​the joint.

[0050] This invention divides the joints between longitudinally adjacent square precast components into several independent grouting chambers. Each grouting chamber has its own independent grouting hole and vent hole, and adjacent grouting chambers are not interconnected or intersecting. During grouting, grouting operations are performed independently in each grouting chamber, confining the grout within its own independent chamber and avoiding the problem of incomplete filling caused by grout cross-flow. Independent grouting in each chamber allows for control of grouting pressure and volume according to the actual conditions of each section, ensuring that the joints in each area are fully filled. This zoned independent grouting improves the density and uniformity of the joint grouting, ensuring the structural integrity and waterproof reliability.

[0051] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S3, the grout used for grouting the joint is epoxy resin grout. The epoxy resin grout is made by mixing liquid A and liquid B in a mass ratio of 3:1. Liquid A is modified epoxy resin, and liquid B is modified amine. Quartz powder is added to the epoxy resin grout, and the mass ratio of the sum of the masses of liquid A and liquid B to the mass of quartz powder is 1:0.5.

[0052] During actual construction, the grout is prepared before the joint grouting operation. First, prepare liquid A and liquid B. Liquid A is modified epoxy resin, and liquid B is modified amine, with a mass ratio of 3:1. Simultaneously, prepare quartz powder, using ordinary angular powder of 400 mesh, with a water content not exceeding 0.5%. During preparation, pour half of liquid A into the quartz powder and stir evenly. Then, pour in the remaining liquid A and stir evenly. Finally, pour liquid B into the mixture and continue stirring to form a homogeneous epoxy resin grout. Using this preparation sequence can extend the grout's grouting time.

[0053] In the prepared epoxy resin slurry, the combined mass ratio of component A and component B to the mass ratio of quartz powder is 1:0.5. After mixing at 5℃, the slurry has a viscosity of less than 7500 mPa·s and a workable time of 80 min. After curing, the pure epoxy resin achieves a compressive strength of 15-20 MPa after 7 days at 5℃, and a compressive strength of 50 MPa after 15 days.

[0054] After the prefabricated square components are assembled to form the main body of the prefabricated shaft, the prepared epoxy resin grout is injected into the grouting holes of the joints through grouting equipment. During the grouting process, the grout flows along the joint gaps, filling the gaps between the tenons and mortises, and air in the joints is discharged through the vent holes. Because the grout maintains a suitable viscosity at low temperatures, it can flow fully and fill small gaps. After grouting is completed, the grout gradually solidifies within the joints, forming a stable bonding layer.

[0055] Using ordinary cement-based grout or ordinary epoxy resin grout for joint grouting presents the following problems. Ordinary cement-based grout exhibits increased viscosity and decreased fluidity at low temperatures, making it difficult to fully fill joint gaps. Furthermore, its slow curing speed and gradual strength development negatively impact subsequent processes. Ordinary epoxy resin grout has a shortened workable time at low temperatures, is prone to initial setting during grouting, and its excessively high viscosity leads to filling difficulties. After curing, its bond strength is insufficient to meet the joint's stress requirements.

[0056] This invention uses a mixture of modified epoxy resin (component A) and modified amine (component B) at a mass ratio of 3:1, with quartz powder incorporated. The total mass ratio of component A and component B to quartz powder is 1:0.5. This grout maintains a suitable viscosity at a low temperature of 5°C, allowing it to flow fully and fill joint gaps. The workable time is 80 minutes, meeting the time requirements for joint grouting. After curing, it achieves initial strength in 7 days and reaches 50 MPa in 15 days, ensuring the joint can withstand corresponding loads during subsequent construction. The addition of quartz powder adjusts the grout's fluidity, prevents sedimentation, and improves the grout's compactness. This grout can fully fill joint gaps at low temperatures and forms a reliable bonding layer after curing, guaranteeing the joint's mechanical properties and waterproofing effect.

[0057] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S3, when grouting the joint, the grouting pressure is 0.4 MPa, the grouting speed is controlled at 300-350 kg / h, and the grouting time of each grouting chamber is no more than 45 min.

[0058] During actual construction, after the square prefabricated components are assembled and form the main body of the prefabricated shaft, joint grouting is carried out. Before grouting, the theoretical grouting volume is calculated based on the volume of each grouting chamber, serving as a reference for grouting completion. The grouting equipment uses a grouting pump with pressure regulation and flow control functions, which is connected to the grouting holes of the grouting chamber.

[0059] Start the grouting pump and adjust its operating parameters to maintain the grouting pressure at 0.4 MPa. During grouting, keep the grouting pressure stable to ensure the grout can overcome joint resistance and fully fill the gap between the tenon and mortise. Simultaneously control the grouting speed, keeping the injection rate within the range of 300 to 350 kg / h. The grouting speed should not be too fast to avoid grout turbulence and air bubble entrainment; nor should it be too slow to prevent initial setting of the grout during the grouting process.

[0060] During grouting, the amount of grout injected is monitored in real time, and the start time is recorded. When the grout volume reaches the theoretical grout volume, check if grout is being discharged from the vent holes. Grouting is stopped once it is confirmed that the joint has been fully filled with grout. If the grouting time exceeds 45 minutes and the grout volume has not reached the theoretical grout volume, the grouting equipment and grouting holes must be checked for blockages. Grouting can continue after troubleshooting. The grouting time for each grouting chamber should be controlled within 45 minutes to ensure that the grouting operation is completed within the operable time of the grout.

[0061] After grouting is completed in one grouting chamber, the same grouting operation is performed on the other grouting chambers in sequence until the joints of all grouting chambers are grouted. After grouting is completed, the grouting holes and vent holes are sealed with sealing material.

[0062] When the grouting pressure is too low, the grout cannot overcome the joint resistance and is difficult to fully fill the gaps; when the grouting pressure is too high, it may damage the precast components or cause the sealing gasket to fail. When the grouting speed is too fast, the grout is prone to turbulence and air bubbles, resulting in incomplete filling; when the grouting speed is too slow, the grout may initially set during the grouting process, affecting the continuity of grouting. When the grouting time is too long, the grout may exceed the workable time and solidify during the grouting process, leading to grouting failure.

[0063] This invention defines key process parameters for joint grouting: a grouting pressure of 0.4 MPa, a grouting speed controlled at 300-350 kg / h, and a grouting time of no more than 45 minutes for each grouting chamber. The 0.4 MPa grouting pressure allows the grout to overcome joint resistance and fully fill the gap between the tenon and mortise, while avoiding damage to the component due to excessive pressure. The 300-350 kg / h grouting speed avoids grout turbulence and air bubble entrainment caused by excessive speed, and also avoids initial setting of the grout during the grouting process due to excessively slow speed. The 45-minute grouting time for each chamber ensures that the grouting operation is completed within the grout's operable time, preventing the grout from solidifying during the grouting process. By clearly defining these process parameters, the stability and controllability of joint grouting quality are improved.

[0064] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S3, when hoisting the square prefabricated component, a distance sensor is installed on the hoisting device to monitor the distance between the outer wall of the square prefabricated component and the shaft wall in real time during the lowering process; when the monitored distance is less than the preset safety distance, the lowering speed of the hoisting device is reduced until the monitored distance is greater than or equal to the preset safety distance, and then the lowering continues at the current lowering speed.

[0065] During construction, distance sensors are installed on the lifting equipment's lifting gear. These sensors, either laser or ultrasonic, are oriented towards the well wall and measure the distance between the outer wall of the square precast component and the well wall at the location of the lifting gear. Three distance sensors (laser or ultrasonic) are installed, evenly spaced at 120° intervals along the circumference of the lifting gear. Each sensor's measurement direction is perpendicular to the outer wall of the square precast component, and the sensor is installed at a height of 0.5m to 1.0m below the lifting gear, close to the component's center of gravity. When the component tilts during lifting, the change in the distance measured by the sensors reflects the degree of proximity between the component's bottom and the well wall. Furthermore, tilt sensors can be added to the lifting gear to fuse tilt data with distance data for further calculation, determining the offset of the component's bottom.

[0066] At the start of the hoisting operation, the hoisting equipment lifts the square precast component and slowly lowers it from the wellhead. During the lowering process, distance sensors collect real-time distance data between the outer wall of the square precast component and the well wall, and transmit the data to the control unit. The control unit compares the real-time monitored distance value with a preset safety distance.

[0067] When the monitored distance is greater than or equal to the preset safety distance, it indicates that the square precast component is in a safe state, and the hoisting equipment continues to lower it at the current speed. When the monitored distance is less than the preset safety distance, it indicates that the square precast component has shifted towards the well wall, posing a collision risk. The control unit issues a command to the hoisting equipment to reduce the lowering speed. After the lowering speed is reduced, the swing amplitude of the square precast component decreases, and it gradually returns to its normal position.

[0068] While the speed is decreasing, the distance value continues to be monitored. When the monitored distance value recovers to a level greater than or equal to the preset safety distance, it indicates that the square precast component has returned to a safe position. The control unit then issues a command to allow the hoisting equipment to continue lowering at the reduced speed, without returning to the initial speed, to avoid the component swinging again due to increased speed. During subsequent lowering, the distance sensor continues to monitor, and if the distance value falls below the preset safety distance again, the above speed reduction operation is repeated.

[0069] Through the above control methods, the square prefabricated components maintain a safe distance from the well wall throughout the entire lowering process, thus avoiding collisions.

[0070] When hoisting control is achieved through manual observation and experience-based judgment, operators visually assess the distance between the precast square component and the well wall from the wellhead or inside the well, relying on experience to determine if there is a risk of collision. If component misalignment is detected, operators manually adjust the lowering speed or pause the lowering process. This control method depends heavily on the operator's experience and reaction speed; the accuracy of judgment is significantly affected by human factors. Furthermore, limited visibility in deep well environments increases the difficulty of observation, making it hard to detect misalignment promptly and take control measures, thus posing a collision risk.

[0071] This invention utilizes a distance sensor mounted on the lifting equipment to monitor the distance between the outer wall of the precast square component and the manhole wall in real time during the lowering process. When the detected distance falls below a preset safety distance, the lowering speed is automatically reduced until the distance returns to a safe range, at which point the lowering continues at the current speed. This solution achieves automatic monitoring and control of the lifting process, independent of operator experience and reaction time, ensuring accurate judgment and timely response. By actively controlling the component's swing state through speed adjustment, collisions with the manhole wall are avoided, protecting the component from damage. Simultaneously, it ensures the continuity of lifting operations and construction efficiency without requiring complex hardware modifications to the lifting equipment.

[0072] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S3, at least three distance sensors are evenly arranged circumferentially on the lifting device. Each distance sensor is used to monitor the distance between the outer wall of the square prefabricated component and the shaft wall in different directions. When the distance in any direction is less than the preset safety distance, the lowering speed of the lifting device is reduced until the distance in all directions is greater than or equal to the preset safety distance, and then the lowering continues at the current lowering speed.

[0073] During actual construction, three distance sensors are evenly installed circumferentially on the lifting equipment's lifting device. The three sensors are arranged at a 120° angle on the lifting device, each facing a different direction. Each distance sensor independently measures the distance between the outer wall of the square precast component and the well wall in its respective direction.

[0074] At the start of the hoisting operation, the hoisting equipment lifts the square precast component and slowly lowers it from the wellhead. During the lowering process, three distance sensors operate simultaneously, collecting distance data in their respective directions and transmitting the data to the control unit. The control unit compares the real-time monitored distance values ​​in each of the three directions with preset safety distances.

[0075] When the distance values ​​in all three directions are greater than or equal to the preset safety distance, it indicates that the square precast component is in a safe state in all directions, and the hoisting equipment continues to lower it at the current speed. When the distance value in any direction is less than the preset safety distance, it indicates that the square precast component has shifted in that direction, posing a collision risk. The control unit issues a command to the hoisting equipment to reduce the lowering speed. After the lowering speed is reduced, the swaying amplitude of the square precast component decreases, and it gradually returns to its normal position.

[0076] While the speed is decreasing, the distance values ​​in all three directions are continuously monitored. Only when the distance values ​​in all directions return to a level greater than or equal to the preset safety distance does it indicate that the square precast component has been completely centered and is in a safe state in all directions. At this point, the control unit issues a command to have the hoisting equipment continue to lower the component at the reduced speed, without returning to the initial speed, to avoid the component swinging again due to increased speed.

[0077] If, during the deceleration process, the distance value in any direction remains below the preset safe distance, the deceleration will continue until the distance values ​​in all directions return to the safe range. During subsequent descent, the three distance sensors will continuously monitor the area; if the distance value in any direction falls below the preset safe distance again, the deceleration process will be repeated.

[0078] Through the above control methods, the square prefabricated components maintain a safe distance from the well wall in all directions during the entire lowering process, avoiding collisions with the well wall from unmonitored directions due to blind spots in monitoring in a single direction.

[0079] This invention achieves omnidirectional monitoring of the gap between the component and the well wall by uniformly arranging at least three distance sensors along the circumference of the lifting equipment's lifting device. Each distance sensor monitors the distance in a different direction. The three sensors are arranged at a 120° angle, covering the entire circumference, and any deviation in any direction can be detected promptly. When the distance in any direction is less than a preset safety distance, deceleration control is triggered, and the speed is only restored after the distance in all directions has returned to the safe range. This solution eliminates the blind spots of single-direction monitoring, ensuring that the component's deviation can be detected and controlled promptly regardless of the direction, effectively preventing the component from colliding with the well wall in the unmonitored direction and improving the safety of the lifting process.

[0080] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S3, the preset safety distance is determined based on the one-sided gap between the outer wall of the square prefabricated component and the shaft wall, and the preset safety distance is set to 1 / 3 of the one-sided gap; wherein, the one-sided gap is equal to the difference between the inner diameter of the shaft body and the outer diameter of the square prefabricated component, and then divided by 2.

[0081] The preset safety distance is set to one-third of the clearance on one side. This means that when the component shifts from the center position towards the well wall, deceleration control is triggered when the shift reaches one-third of the clearance on one side. At this point, the remaining two-thirds of the clearance between the outer wall of the component and the well wall serves as a safety margin, ensuring that the component has enough space to return to its correct position during deceleration and avoid collision.

[0082] The preset safety distance is proportional to the clearance on one side. When the shaft diameter and clearance are large, the preset safety distance increases accordingly, and the triggering timing is advanced; when the shaft diameter and clearance are small, the preset safety distance decreases accordingly, and the triggering timing is delayed. This setting method ensures that the control threshold matches the actual size of the shaft.

[0083] During the hoisting operation, distance sensors monitor the distance between the outer wall of the square precast component and the well wall in real time. The control unit compares this distance value with a preset safety distance. When the monitored distance is less than the preset safety distance, the lowering speed is reduced; when the monitored distance recovers to be greater than or equal to the preset safety distance, the lowering continues at the current speed.

[0084] When the preset safety distance is set too large, the component will trigger deceleration before it has made a significant deviation, resulting in frequent triggering and affecting construction efficiency. When the preset safety distance is set too small, the component will trigger deceleration only when it is close to the well wall. Even after deceleration, it may still collide due to inertia, resulting in insufficient safety margin.

[0085] This invention determines the preset safety distance based on the one-sided gap between the outer diameter of the square prefabricated component and the inner diameter of the shaft, setting it to one-third of this one-sided gap. This setting method correlates the control threshold with the actual dimensions of the shaft. The preset safety distance being less than the difference ensures that speed adjustment is triggered before the component's swing amplitude reaches the point of impact with the shaft wall, thus creating a safety margin. The one-third setting balances safety and construction efficiency, avoiding both the risk of late triggering and collision after deceleration due to an excessively small preset safety distance, and the problem of frequent deceleration due to an excessively large preset safety distance, which affects construction efficiency. Furthermore, this setting method is applicable to shaft projects of different diameters, exhibiting good versatility.

[0086] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S4, when grouting the gap between the outer wall of the shaft and the surrounding soil, the gap is divided into multiple grouting sections along the longitudinal direction of the shaft. The height of each grouting section is equal to the height of one or more square prefabricated components. Grouting is carried out section by section from bottom to top. After each section is completed, the grout solidifies until the compressive strength reaches more than 70% of the design value before the adjacent section is grouted.

[0087] During actual construction, after the main body of the prefabricated shaft is formed, the gap between the outer wall of the shaft and the surrounding soil is divided longitudinally into multiple grouting sections based on the total depth of the shaft and the height of the square prefabricated components. The height of each grouting section is equal to the height of one or more square prefabricated components. Typically, four or six components constitute one grouting section, which facilitates the organization of grouting operations and the control of grouting pressure.

[0088] Grouting operations begin with the bottommost grouting section. First, backfill grouting is performed on this section. The grouting pipe is inserted into the corresponding backfill gap, and cement-based grout or a specialized backfill grouting material is injected to fill the gap between the shaft wall and the surrounding soil. During grouting, the grouting pressure and volume are controlled to ensure the grout evenly fills the backfill gap within the grouting section. After grouting is completed, grouting operations are stopped, and the curing phase begins.

[0089] During the curing phase, the grout in this grouting section gradually solidifies and hardens, and its compressive strength gradually increases. The development of the grout's compressive strength is monitored by placing test blocks cured under the same conditions on-site or by using non-destructive testing methods. When the compressive strength of the grout in this section reaches more than 70% of the design value, it indicates that the grout has sufficient strength to withstand the lateral pressure generated during the construction of the upper grouting section, without damaging the solidified grout layer or adversely affecting the shaft components.

[0090] At this point, the grouting operation begins on the adjacent section above, i.e., the second grouting section from bottom to top. Backwall grouting is performed on the second grouting section, injecting grout to fill the gaps behind the wall. After grouting is completed, the curing stage begins again. Once the compressive strength of the grout in this section reaches more than 70% of the design value, the third grouting section is then performed. This process is repeated, completing the backwall grouting operation for all grouting sections from bottom to top.

[0091] By using layered grouting and segmented curing, each grouting layer forms a stable support layer after solidification, providing a support foundation for the next grouting layer. At the same time, it avoids excessive lateral pressure on the assembled components from the unsolidified grout, preventing deformation or displacement of the components.

[0092] The one-time integral grouting method, which involves grouting the entire back wall gap throughout the shaft depth after the prefabricated shaft body is formed, presents the following problems: Due to the significant shaft depth, the back wall gap may be uneven, making it difficult to ensure uniform grout filling of the entire gap during a one-time grouting process. This can easily lead to problems such as grout segregation, incomplete filling, and localized voids. Furthermore, during the one-time grouting process, a large amount of uncured grout exerts significant lateral pressure on the assembled components, potentially causing component deformation, displacement, or joint cracking, thus affecting structural safety.

[0093] This invention divides the gap behind the shaft wall into multiple grouting sections along the longitudinal direction of the shaft. The height of each grouting section is equal to the height of one or more square precast components, and grouting is carried out section by section from bottom to top. After each section is completed, the grout is allowed to solidify until its compressive strength reaches more than 70% of the design value before the next adjacent section is grouted. Layered grouting avoids the problem of incomplete filling caused by excessive grouting height at one time, ensuring that the grout in each section uniformly fills the gap behind the shaft wall. Allowing the grout to solidify before grouting the next section avoids lateral pressure from unsolidified grout on the assembled components, preventing component deformation or displacement. Through segmented construction and segmented curing, the density and structural stability of the grout behind the shaft wall are guaranteed, improving the overall quality of the shaft.

[0094] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S4, when performing back-wall grouting for each grouting section, an intermittent grouting process is adopted, including the following steps: Step A: Inject a first set amount of grout at a first grouting pressure, and then pause grouting to allow the injected grout to initially fill the gap behind the wall and expel air bubbles; Step B: Inject a second set amount of grout at a second grouting pressure, wherein the second grouting pressure is greater than the first grouting pressure; Step C: Repeat the pause grouting operation in step A and the grouting operation in step B until the total grouting volume of the grouting section reaches the theoretical grouting volume; wherein the sum of the first set amount and the second set amount is equal to the theoretical grouting volume, or the first set amount accounts for 30% to 50% of the theoretical grouting volume, and the remaining amount is used as the second set amount for batch grouting.

[0095] After the main body of the prefabricated shaft is formed, grouting is performed on the gap between the outer wall of the shaft and the surrounding soil. During construction, the gap is divided into multiple grouting sections along the longitudinal direction of the shaft, and the height of each grouting section is equal to the height of one or more square prefabricated components. The grouting operation is carried out section by section from bottom to top. After each section is completed, the grout is allowed to solidify until the compressive strength reaches more than 70% of the design value before the adjacent section is grouted.

[0096] When performing backfill grouting for each grouting section, an intermittent grouting process is adopted. First, the theoretical grouting volume is calculated based on the backfill gap volume of the grouting section, and the theoretical grouting volume is divided into a first set volume and a second set volume. The first set volume accounts for 30% to 50% of the theoretical grouting volume, and the remaining part is used as the second set volume.

[0097] After grouting begins, the grouting pipe is inserted into the corresponding back wall gap of the grouting section. A pressure sensor is installed at the end of the grouting pipe to monitor the grout pressure in the back wall gap in real time. The grouting pump is started, and its operating parameters are adjusted to maintain the grouting pressure at the first grouting pressure. The first grouting pressure uses a relatively low pressure value to inject the grout into the back wall gap at a slower rate. When the injected grout volume reaches the first set amount, the grouting pump is turned off, and grouting is paused.

[0098] During the pause phase, the injected grout gradually settles under gravity, initially filling the voids in the gap behind the wall. Simultaneously, air bubbles carried within the grout gradually rise and are expelled. Pressure sensors continuously monitor the grout pressure within the gap behind the wall. As air bubbles are expelled and the grout settles, the grout pressure gradually decreases. The pause ends when the grout pressure drops to a preset pressure value. The preset pressure value is lower than the first grouting pressure.

[0099] After the pause, start the grouting pump and adjust its operating parameters to maintain the grouting pressure at the second grouting pressure. The second grouting pressure is higher than the first grouting pressure, using a higher pressure to inject the grout into the gap behind the wall at a faster speed. Inject the remaining second set amount in batches. After each batch of grout is injected, repeat the above pause-and-restart operation: grouting is paused after injecting a certain amount, and grouting resumes when the pressure drops to the preset value, until the total amount of grout injected in that grouting section reaches the theoretical grouting volume. After grouting is completed, seal the grouting holes with sealing material.

[0100] Through the intermittent grouting process described above, the gaps behind the wall in each grouting section are filled and compacted layer by layer to form a uniform grouting layer.

[0101] This embodiment employs staged control of grouting pressure. The low-pressure stage allows the grout to slowly fill the gaps, reducing turbulence and air bubble entrainment; the high-pressure stage further compacts the grout, increasing the filling density. This embodiment introduces a pause for air release. After each injection of a certain amount of grout, grouting is paused to allow the injected grout to settle and allow air bubbles to rise and escape, preventing air bubbles from remaining in the grout layer. This embodiment controls the pause duration through grout pressure monitoring. During air bubble expulsion, the grout pressure continuously decreases. When the pressure drops to a preset value, it indicates that the air bubbles have been largely expelled, at which point the pause ends and the next stage of grouting begins. This control method directly links the pause duration to the air bubble expulsion status, avoiding the problems of insufficient air release or excessively long waiting times that may occur with fixed pause times.

[0102] The intermittent grouting process in this embodiment enables the gap behind the wall to be filled and compacted layer by layer. Compared with continuous grouting, the air bubble content in the grouting layer is reduced and the filling uniformity is improved, thereby enhancing the support effect and waterproof performance of the grouting layer behind the wall.

[0103] In a preferred embodiment, in the construction method of the prefabricated shaft structure, in step S4, each time grouting is paused, the grout pressure in the gap behind the wall is monitored in real time. When the grout pressure drops to a preset pressure value, the pause ends and the next grouting begins; the preset pressure value is less than the first grouting pressure.

[0104] During actual construction, when using an intermittent grouting process for backfilling the grouting section, a pause phase is initiated after each batch of grout is injected. Before the pause phase begins, a pressure sensor is installed in the backfill gap or at the end of the grouting pipe to monitor the grout pressure in the backfill gap in real time. The pressure sensor is connected to ground-based data acquisition equipment to transmit the monitored pressure data to the control unit in real time.

[0105] When the pause phase begins, the grouting pump stops working and no longer injects grout into the gap behind the wall. At this time, the grout in the gap behind the wall gradually settles under the action of gravity, filling the voids in the gap, while air bubbles carried in the grout gradually rise and are expelled. As the grout settles and the air bubbles are expelled, the grout pressure in the gap behind the wall gradually decreases.

[0106] The control unit receives pressure data transmitted from the pressure sensor in real time and compares the real-time pressure value with a preset pressure value. The preset pressure value is determined based on the first grouting pressure and is set to a value less than the first grouting pressure, such as 50% or 60% of the first grouting pressure. This preset pressure value reflects the pressure state when the air bubbles have been basically expelled and the grout has initially stabilized.

[0107] During the initial pause phase, the grout pressure gradually decreases from the initial grouting pressure. When the real-time pressure value exceeds the preset pressure value, it indicates that air bubbles have not been completely expelled and the grout is still settling. The control unit remains paused and continues monitoring. When the real-time pressure value drops to the preset pressure value, it indicates that air bubbles have been largely expelled and the grout has initially stabilized. At this point, the control unit issues a command to end the pause and start the grouting pump to begin the next grouting cycle.

[0108] After the next grouting begins, the next batch of grout is injected at the second grouting pressure. After grouting is completed, the process enters a pause phase again, repeating the pressure monitoring and pause termination judgment process described above. By monitoring the pressure, the duration of each pause phase is directly correlated with the air bubble discharge status. The pause automatically ends when the pressure drops to a preset value, without the need for manual judgment.

[0109] Throughout the intermittent grouting process, the duration of each pause is automatically determined based on the actual air release of the grout, ensuring that air bubbles are fully expelled while avoiding excessively long pauses that could affect construction efficiency.

[0110] Specifically, the preset pressure value can be set to 0.2 MPa. When the grout pressure drops from the first grouting pressure of 0.3 MPa to 0.2 MPa, it indicates that the air bubbles have been basically expelled, at which point the pause ends and the next grouting begins.

[0111] In intermittent grouting, a fixed pause time is set for each grouting interruption, such as 5 minutes. This timed pause method has two problems: if the pause time is set too short, air bubbles will not be fully expelled before the next grouting begins, leaving residual air bubbles in the grout layer and affecting the density; if the pause time is set too long, the grout will have been fully degassed but will still be waiting, affecting construction efficiency. Since the fluidity of the grout and the degassed rate are affected by various factors such as temperature, grout mix ratio, and backfill gap conditions, a fixed pause time is difficult to adapt to changes in actual working conditions.

[0112] This invention monitors the grout pressure in the gap behind the wall in real time during each grouting pause. The pause ends and the next grouting session begins when the grout pressure drops to a preset value. The preset pressure value is lower than the first grouting pressure. The grout pressure monitoring determines the air bubble discharge status. During air bubble discharge, the grout pressure continuously decreases. When the pressure drops to the preset value, it indicates that the air bubbles have been largely discharged and the grout has initially stabilized. This scheme directly links the pause time to the air bubble discharge status, using pressure monitoring for quantitative judgment. This avoids the uncertainty of setting pause times based on experience, ensuring sufficient air bubble discharge and dense grouting while preventing excessively long pauses that could affect construction efficiency. This achieves precise control of the pause time for intermittent grouting.

[0113] The following specific embodiment is provided to further illustrate the construction method of the prefabricated shaft structure provided by the present invention.

[0114] This embodiment provides a construction method for prefabricated shaft structures, applicable to urban underground spaces, mines, tunnel ventilation, and various vertical passage projects.

[0115] First, step S1 is performed: Using the mining method, a straight section of the shaft bottom is excavated and lined with secondary lining to connect to the main structure. At the designed bottom of the shaft, a straight horizontal tunnel is excavated using the mining method. The tunnel's cross-sectional dimensions are determined according to the requirements of the main structure. After excavation, a secondary lining structure is constructed within the tunnel to form a stable, permanent structure. One end of this straight tunnel connects to the bottom of the shaft to be constructed subsequently, while the other end connects to the underground main structure, serving as a transitional connection between the shaft and the main structure.

[0116] After completing step S1, proceed to step S2: Using the inverted shaft wall method, excavate the vertical shaft to above the straight section of the underground excavation, connecting the shaft to the straight section. Excavate the vertical shaft in sections from the surface downwards. After each section is excavated to a certain depth, promptly construct a shaft wall support structure to prevent collapse. Using the inverted shaft wall method, excavate section by section from top to bottom. After each section is excavated, construct a reinforced concrete shaft wall to form a temporary support structure. Repeat the above procedures until the shaft reaches above the completed straight section of the underground excavation, and connect the shaft to the straight section, forming a complete vertical shaft excavation space.

[0117] After the shaft excavation is completed, step S3 is performed: the main body of the shaft is divided longitudinally into multiple hollow square prefabricated components, without segmentation on the cross-section, with one component placed every 1.5 m along the longitudinal direction of the shaft. Due to the presence of structures such as the safety door opening of the rescue shaft and the platform slab brackets, the square prefabricated components are divided into four types: A, B, C, and D. Among them, the D-type square prefabricated components are equipped with brackets, and prefabricated platform slabs are erected on the brackets. The prefabricated platform slabs and brackets are connected by overlapping and fixed with bolts.

[0118] During prefabrication, tenons or mortises are provided on the end faces of the square prefabricated components. The tenon is located on the end face of one square prefabricated component, and the mortises are located on the corresponding end faces of adjacent square prefabricated components. The tenon and mortises between front and rear components form a joint, using a single-tenon short joint with a joint length of 95 mm. A first reserved hole is provided in the tenon, and a second reserved hole corresponding to the first reserved hole is provided in the mortis. Corrugated steel pipes are pre-embedded inside the square prefabricated components on the non-soil-adjacent side for inserting bent bolts. Grouting holes and vent holes are pre-embedded at the joints of the square prefabricated components. The grouting holes are located at the lower end of the joint, and the vent holes are located at the upper end of the joint. The pre-embedded bolt sleeves of the grouting holes facilitate connection to the grouting pump pipe, and an externally closable valve is connected during grouting to prevent grout leakage.

[0119] Two waterproofing measures are implemented at the joint. The first measure is to create a completely sealed groove for installing waterproof material at the joint, with a waterproof rubber gasket attached inside the groove. The second measure is to grout the joint later.

[0120] The joints between longitudinally adjacent square precast components are divided into several independent grouting chambers. Each grouting chamber has its own independent grouting hole and vent hole, and adjacent grouting chambers are not interconnected or intersecting. The grouting chamber is the smallest unit of grouting work. If the space of a chamber is too large and cannot be guaranteed to be filled within the specified time, the large chamber should be divided into smaller chambers or multiple grouting positions should be set up. The grouting work is generally designed according to the principles of slow expansion, simultaneous grouting and venting, and bottom-up. The grouting speed is controlled at 325 kg / h, and the grouting time for each grouting chamber is 45 minutes.

[0121] Before hoisting operations, a preset safety distance is determined based on the one-sided gap between the outer wall of the square precast component and the well wall. The preset safety distance is set to 1 / 3 of the one-sided gap; where the one-sided gap is equal to the difference between the inner diameter of the well body and the outer diameter of the square precast component, divided by 2. Three distance sensors are evenly arranged circumferentially on the lifting equipment's lifting device. Each distance sensor is used to monitor the distance between the outer wall of the square precast component and the well wall in different directions. In this embodiment, three distance sensors are evenly arranged circumferentially on the lifting equipment's lifting device, and each distance sensor is used to monitor the distance between the outer wall of the square precast component and the well wall in different directions.

[0122] During assembly, a gantry crane is used to assist in positioning, hoisting the square prefabricated components one by one into the shaft from bottom to top. First, the bottommost square prefabricated component is hoisted to the bottom of the shaft, aligning it with the secondary lining structure of the straight section excavated in the cut-and-cover mine. During the lowering of the square prefabricated components, the distance between the outer wall of the component and the shaft wall is monitored in real time. When the monitored distance is less than a preset safety distance, the lowering speed of the hoisting equipment is reduced until the monitored distance is greater than or equal to the preset safety distance, at which point the lowering continues at the current speed. In this embodiment, each distance sensor monitors the distance in its respective direction in real time. When the distance in any direction is less than the preset safety distance, the lowering speed of the hoisting equipment is reduced until the distance in all directions is greater than or equal to the preset safety distance, at which point the lowering continues at the current speed.

[0123] During hoisting, precise positioning is achieved by inserting locating pins into the first and second pre-drilled holes. The locating pins are spindle-shaped, with diameters at both ends smaller than the middle diameter. During assembly, they are inserted into pre-drilled holes within the components, which are located within the mortise and tenon joints. Adjacent square prefabricated components are connected via tenon and mortise joints to achieve initial alignment.

[0124] After positioning, bent bolts are used to pass through the pre-embedded corrugated steel pipes within the square precast components and lock and fix adjacent square precast components. M27 high-strength bolts are used, with a bolt mechanical performance grade of 6.8 and a nut mechanical performance grade of 6, with a tightening torque of 380 N·m. The bent bolts are placed on the non-soil-adjacent side of the components, evenly distributed across the mid-span, to help limit uncoordinated deformation between precast components. The upper and lower parts of the precast components are connected to the cast-in-place components. The cast-in-place structure should achieve precise casting of structures such as tenons, sealing grooves, and embedded parts, and precise pre-reservation of embedded parts such as grouting pipes, bent bolt holes, and positioning pin holes within the cast-in-place structure.

[0125] After assembling four precast square components, grouting is first performed on all longitudinal joints between these four components (i.e., mortise and tenon joint grouting). After the joint grout has cured for 12 hours, grouting is then performed on the corresponding backfill gaps between the four components (i.e., backfill grouting). The grout used for joint grouting is epoxy resin grout, composed of a mixture of component A and component B in a 3:1 mass ratio. Component A is modified epoxy resin, and component B is modified amine. Quartz powder is incorporated into the epoxy resin grout, and the mass ratio of the sum of components A and B to the quartz powder is 1:0.5. The grouting pressure is 0.4 MPa, the grouting speed is 325 kg / h, and the grouting time for each grouting chamber is 45 minutes. Joint grouting is carried out according to the principles of slow expansion, simultaneous grouting and drainage, and from bottom to top. During grouting, the grout is injected through the grouting holes and flows along the joint gaps. Air inside the joint is expelled through the vent holes. Grouting stops when the grout is discharged from the vent holes, thus ensuring a tight joint. After grouting is completed, the grouting holes and vent holes are sealed with sealing material. To achieve the aforementioned grouting speed, a screw-type metering grouting pump is recommended. This type of pump can stably output grout at a pressure of 0.4 MPa at a rate of 3 L / min, which meets the grouting speed requirements of this invention.

[0126] The specific properties of the epoxy resin grout used for joint grouting are as follows: the volatile content of both liquid A and liquid B is less than 1%, and the epoxy equivalent of liquid A is 190-210. The specific gravity of liquid A is 1-1.05 g / cm³, and that of liquid B is 1-1.05 g / cm³. An epoxy reactive diluent is used for liquid A. After mixing the two liquids, the viscosity after adding quartz powder at 5℃ is less than 7500 mPa·s, and the workable time is 80 min. After pure epoxy curing, under 5℃ curing conditions, its compressive strength reaches 18 MPa after 7 days and 50 MPa after 15 days. For the more critical bonding tensile strength of joint grouting, under the same conditions, it can reach 8 MPa after 7 days and 12 MPa after 15 days. The quartz powder used is ordinary angular powder with a 400-mesh particle size and a water content of no more than 0.5%. During preparation, pour half of solution A into the quartz powder and stir until homogeneous. Then pour in the remaining solution A and stir until homogeneous again. Next, pour solution B into the mixture and continue stirring to form a homogeneous epoxy resin slurry. This preparation sequence can extend the grouting time. After grouting is completed, it is recommended to retain samples under the same conditions to determine the appropriate backfilling timing.

[0127] The properties of grout for tenon and mortise joints are significantly affected by temperature. Higher temperatures result in lower viscosity but shorter setting time, reducing the workable time; lower temperatures result in higher viscosity but longer setting time, increasing the workable time. Given the high specific heat capacity of epoxy resin, in winter when temperatures are low, the grout is heated and grouting is performed during periods of higher external temperature; in summer when temperatures are high, the grout is cooled and grouting is performed during periods of lower external temperature. Grouting should be carried out as soon as the epoxy resin grout is prepared, and the length of the grouting pipe should be minimized to extend the grouting time and prevent quartz powder from settling before reaching the tenon and mortise joint. The grouting holes and vent holes in the tenons and mortise joints of precast components are marked with inkjet printing before the components leave the factory; the construction unit should perform grouting operations according to the design requirements and corresponding numbering.

[0128] The prefabricated components include embedded parts such as positioning pins and steel plates, all made of Q235 steel. A gantry crane is used for hoisting. Hoisting spikes are pre-embedded in the prefabricated components. The allowable load-bearing capacity of the spikes and hoisting heads is 32 t. The safety factor for steel failure of the spikes is 3.0, and the safety factor for steel failure of the hoisting heads is 4.0. During hoisting, the acute angle between the spike and the hoisting rope must not exceed 30°. The construction unit must design the hoisting plan according to this requirement. Before the production of molds and components, the supplier of the hoisting system should provide a hoisting plan and its corresponding complete calculations, which must be inspected and approved by the design unit. The spike material should meet the Charpy impact test requirement of greater than 27 J at -20 ℃, and there should be a clear allowable load mark on the upper surface of the spike head. The hoisting system should meet the requirements of current national standards. Thus, following step S3, the prefabricated shaft main body is formed.

[0129] Finally, step S4 is performed: After the prefabricated shaft body is formed, grouting is carried out on the gap between the outer wall of the shaft and the surrounding soil. The gap is divided into multiple grouting sections along the longitudinal direction of the shaft. The height of each grouting section is equal to the height of one or more square precast components. Grouting is carried out section by section from bottom to top. After each section is completed, the grout is allowed to solidify until its compressive strength reaches 75% of the design value before proceeding to the next section. In this embodiment, the backfilling is carried out in sections from bottom to top. After each section is completed, the grout is allowed to solidify until its compressive strength reaches 75% of the design value before proceeding to the next section. C20 plain concrete is used as the backfill material. Backfilling is carried out in 1.5 m increments. Each level of backfill concrete is allowed to solidify and harden until it exerts virtually no lateral pressure on the square precast components before the next level of concrete is added. The template trolley provides an auxiliary working surface for grouting of tenons and mortises. Four components are used as a grouting section, and grouting is carried out section by section from bottom to top. For each component, the principle of grouting is adopted first at the bottom and then at the top. As long as the gaps on the contact surface are sealed by the sponge sealing strip to form a closed cavity, the grouting operation can be carried out according to the design requirements.

[0130] When performing backfill grouting for each grouting section, an intermittent grouting process is adopted, including the following steps: Step A: Inject a first set amount of grout at a first grouting pressure of 0.3 MPa, and then pause grouting to allow the injected grout to initially fill the gap behind the wall and expel air bubbles; Step B: Inject a second set amount of grout at a second grouting pressure of 0.5 MPa, wherein the second grouting pressure is greater than the first grouting pressure; Step C: Repeat the pause grouting operation in Step A and the grouting operation in Step B until the total grouting volume of the grouting section reaches the theoretical grouting volume; wherein the sum of the first set amount and the second set amount is equal to the theoretical grouting volume, and the first set amount accounts for 40% of the theoretical grouting volume, with the remaining 60% injected in batches as the second set amount. In this embodiment, a first set amount of grout is injected at a first grouting pressure of 0.3 MPa, grouting is paused to allow the injected grout to initially fill the gaps behind the wall and expel air bubbles. Then, a second set amount of grout is injected at a second grouting pressure of 0.5 MPa. The above pause and grouting process is repeated until the total grouting volume of this grouting section reaches the theoretical grouting volume. The second grouting pressure is greater than the first grouting pressure.

[0131] Each time grouting is paused, the grout pressure in the gap behind the wall is monitored in real time. When the grout pressure drops to the preset pressure value of 0.2 MPa, the pause ends and the next grouting begins. The preset pressure value is less than the first grouting pressure.

[0132] After the backfilling is completed, the construction of the shaft structure is finished.

[0133] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Other modifications can be readily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A construction method for a prefabricated vertical shaft structure, characterized in that, Includes the following steps: S1: The underground excavation method is adopted to complete the excavation of the straight section at the bottom of the shaft for connecting the main structure and the secondary lining structure. S2: The inverted shaft wall method is adopted for construction, and the vertical shaft body is excavated to the top of the straight section of the underground excavation, so that the shaft body is connected to the straight section of the underground excavation. S3: The main body of the shaft is divided longitudinally into multiple hollow square prefabricated components. During assembly, each square prefabricated component is hoisted into the shaft body one by one from bottom to top. Adjacent square prefabricated components are connected by tenons and mortises. The tenon is set on the end face of one square prefabricated component, and the mortise is set on the corresponding end face of the adjacent square prefabricated component. The tenon has a first reserved hole, and the mortise has a second reserved hole corresponding to the first reserved hole. Positioning is achieved by inserting positioning pins into the first and second reserved holes. Adjacent square prefabricated components are locked and fixed by passing bent bolts through the corrugated steel pipes embedded in the square prefabricated components. Waterproof rubber sealing gaskets are set at the joints between longitudinally adjacent square prefabricated components. Grouting holes and venting holes are also embedded at the joints. After assembly, grouting is performed on the joints through the grouting holes to make the joints tight and form the prefabricated shaft body. S4: After the prefabricated shaft body is formed, grouting is performed on the gap between the outer wall of the shaft and the surrounding soil.

2. The construction method for the prefabricated vertical shaft structure according to claim 1, characterized in that, In step S3, the joint between longitudinally adjacent square precast components is divided into several independent grouting chambers, and each grouting chamber is independently equipped with grouting holes and venting holes.

3. The construction method for the prefabricated vertical shaft structure according to claim 1, characterized in that, In step S3, the grout used for grouting the joint is epoxy resin grout. The epoxy resin grout is made by mixing liquid A and liquid B in a mass ratio of 3:

1. Liquid A is modified epoxy resin and liquid B is modified amine. Quartz powder is added to the epoxy resin grout. The mass ratio of the sum of the masses of liquid A and liquid B to the mass of quartz powder is 1:0.

5.

4. The construction method for the prefabricated vertical shaft structure according to claim 1, characterized in that, In step S3, when grouting the joint, the grouting pressure is 0.4 MPa, the grouting speed is controlled at 300-350 kg / h, and the grouting time for each grouting chamber is no more than 45 min.

5. The construction method for the prefabricated vertical shaft structure according to claim 1, characterized in that, In step S3, when hoisting the square precast component, a distance sensor is installed on the hoisting equipment's lifting device. During the lowering process of the square precast component, the distance between the outer wall of the square precast component and the well wall is monitored in real time. When the monitored distance is less than the preset safety distance, the lowering speed of the hoisting equipment is reduced until the monitored distance is greater than or equal to the preset safety distance, and then the lowering continues at the current lowering speed.

6. The construction method for the prefabricated vertical shaft structure according to claim 5, characterized in that, In step S3, at least three distance sensors are evenly installed circumferentially on the lifting device's lifting gear. Each distance sensor is used to monitor the distance between the outer wall of the square precast component and the well wall in different directions. When the distance in any direction is less than the preset safety distance, the lowering speed of the lifting device is reduced until the distance in all directions is greater than or equal to the preset safety distance, and then the lowering continues at the current lowering speed.

7. The construction method for the prefabricated vertical shaft structure according to claim 6, characterized in that, In step S3, the preset safety distance is determined based on the one-sided gap between the outer wall of the square prefabricated component and the well wall. The preset safety distance is set to 1 / 3 of the one-sided gap. The one-sided gap is equal to the difference between the inner diameter of the well body and the outer diameter of the square prefabricated component, and then divided by 2.

8. The construction method for the prefabricated vertical shaft structure according to claim 1, characterized in that, In step S4, when grouting the gap between the outer wall of the shaft and the surrounding soil, the gap is divided into multiple grouting sections along the longitudinal direction of the shaft. The height of each grouting section is equal to the height of one or more square precast components. Grouting is carried out section by section from bottom to top. After each section is completed, the grout is allowed to solidify until the compressive strength reaches more than 70% of the design value before the adjacent section is grouted.

9. The construction method for the prefabricated vertical shaft structure according to claim 8, characterized in that, In step S4, when performing back-wall grouting for each grouting section, an intermittent grouting process is adopted, including the following steps: Step A: Inject a first set amount of grout at the first grouting pressure, then pause grouting to allow the injected grout to initially fill the gap behind the wall and expel air bubbles; Step B: Inject a second set amount of grout at a second grouting pressure, wherein the second grouting pressure is greater than the first grouting pressure; Step C: Repeat the pause grouting operation in Step A and the grouting operation in Step B until the total grouting volume of the grouting section reaches the theoretical grouting volume; The sum of the first set amount and the second set amount is equal to the theoretical grouting amount, or the first set amount accounts for 30% to 50% of the theoretical grouting amount, and the remaining amount is injected in batches as the second set amount.

10. The construction method of the prefabricated vertical shaft structure according to claim 9, characterized in that, In step S4, each time grouting is paused, the grout pressure in the gap behind the wall is monitored in real time. When the grout pressure drops to the preset pressure value, the pause ends and the next grouting begins. The preset pressure value is less than the first grouting pressure.

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