Combined maintenance method and system for construction of composite wall of combined hub station through cover-excavation top-down method

Abstract

The invention discloses a comprehensive maintenance method and system for construction of a composite wall of a comprehensive hub station through a cover-excavation top-down method, and relates to the technical field of rail traffic engineering construction. The technical problems of low maintenance efficiency, unbalanced temperature and humidity control, easiness in cracking and leakage and the like of the laminated wall under the working condition of top-down excavation are solved; the comprehensive system comprises mold curing, intelligent temperature and humidity control, cooling temperature control, heat preservation and moisture preservation and monitoring early warning, automation, refinement and traceability of the curing process are achieved, the moisture preservation and heat preservation period of the laminated wall is prolonged, the internal and external temperature difference is strictly controlled to be smaller than or equal to 25 DEG C, the concrete surface moisture content is controlled to be larger than or equal to 80%, and the impervious concrete curing period is controlled to be larger than or equal to 14 d. According to the construction method, the integrity and the anti-cracking and anti-seepage performance of the wall body are remarkably improved, the construction requirements of the large cover-excavation top-down composite wall are met, the construction convenience and the maintenance quality reliability can be effectively improved, and remarkable economic and social benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of rail transit engineering construction technology, specifically to a comprehensive maintenance method and system for composite wall construction in integrated hub stations using the cut-and-cover reverse construction method. Background Technology

[0002] The cut-and-cover construction method is widely used in the construction of urban subway stations due to its advantages such as small construction area and minimal impact on the surrounding environment. As the core load-bearing and waterproof structure of the cut-and-cover station, the composite wall is composed of underground continuous wall and post-cast concrete wall. Its construction quality directly affects the safety and durability of the station structure.

[0003] For example, Chinese invention patent application number CN201410311428.8 discloses a method for constructing composite walls in a cut-and-cover subway station and a mobile side wall formwork trolley. The construction method mainly includes the following steps: S1: construction of diaphragm walls; S2: construction of the top slab and the side walls below the top slab; S3: construction of the middle slab and the side walls above and below the middle slab; S4: construction of the middle section side walls of the first basement level; S5: construction of the first-phase foundation slab; S6: construction of the middle section side walls of the second basement level; S7: construction of the second-phase foundation slab. This method constructs the side walls below the top slab simultaneously with the construction of the top slab, and constructs the side walls above and below the middle slab simultaneously with the construction of the middle slab. It has the advantages of high construction efficiency and good construction quality of the middle section side walls. The mobile side wall formwork trolley mainly includes side wall formwork, supports and a movable base. The side wall formwork has a concrete pouring port and a chute plate is fixed on the top of the side wall formwork. The trolley has the advantages of reliable side wall formwork assembly quality and convenient concrete pouring of the side wall section at the connection with the top slab and middle slab.

[0004] For example, Chinese invention patent application number CN201910623854.8 discloses a construction method for a cut-and-cover composite wall system, including the following steps: a. construction of an underground continuous retaining wall (1); b. construction of a top slab (2) and a side wall (5) below the top slab; c. construction of a middle slab (3), a side wall (6) above the middle slab, and a side wall (7) below the middle slab; d. construction of a bottom slab (4) and a side wall (9) above the bottom slab; e. construction of a first middle side wall (8); f. construction of a second middle side wall (10). This invention belongs to the rail transit equipment industry and solves the defects of complex construction technology, difficulty in ensuring construction quality, and easy leakage in the construction of composite walls in existing subway station construction. It further enhances the integrity, load-bearing capacity, and seismic performance of the composite wall, and the construction process is safe and reliable.

[0005] For example, Chinese invention patent application number CN202510147432.3 discloses an intelligent curing method and system driven by sensing the internal temperature and humidity field of concrete. The method comprises the following steps: obtaining the surface tensile strength and elastic modulus of concrete at different ages with the same concrete mix proportion; obtaining a fitting function for the surface tensile strength of concrete based on concrete maturity theory and the surface tensile strength of concrete at different ages; predicting the fitting function for the elastic modulus using the elastic modulus at different ages; obtaining the internal surface control temperature difference of concrete at different ages by utilizing the relationship between the surface tensile strength and the surface tensile stress of concrete, combined with the fitting function for the surface tensile strength and the predicted fitting function for the elastic modulus; and intelligently controlling the temperature and humidity of the concrete curing environment based on the internal surface control temperature difference of concrete at different ages.

[0006] Under existing technologies for cut-and-cover reverse construction, the construction of composite walls suffers from several drawbacks. Firstly, the curing methods are simplistic, primarily due to the segmented pouring of the wall during reverse construction and frequent formwork turnover. Traditional curing methods struggle to ensure continuous moisture retention and insulation, leading to excessive water loss from the concrete surface. Secondly, temperature and humidity control is unbalanced, with high temperatures in summer causing excessively high concrete temperatures upon placement and low temperatures in winter leading to frost damage. Furthermore, when the wall thickness is significant, the internal and external temperature differences can exceed limits, resulting in temperature stress cracks. Thirdly, traditional curing focuses only on overall moisture retention, neglecting detailed interface curing, which can lead to problems such as poor bonding and leakage. Fourthly, temperature difference monitoring is lagging: existing curing methods rely heavily on manual inspections, making it impossible to monitor internal temperature and strain changes in real time and dynamically adjust curing measures. To address these technical problems, this invention provides a comprehensive curing method and system for composite wall construction in integrated hub stations using the cut-and-cover reverse construction method. Summary of the Invention

[0007] To address the aforementioned technical problems in the existing technology, this invention provides a comprehensive maintenance method and system for the construction of composite walls in integrated hub stations using the cut-and-cover reverse construction method.

[0008] The present invention adopts the following technical solution:

[0009] This invention provides a comprehensive maintenance method for the construction of composite walls in a combined hub station using the cut-and-cover reverse construction method, comprising:

[0010] Step 1: Add a separate double-layer curing formwork to the outside of the single-sided formwork of the composite wall. The foundation surface for the composite wall construction is a concrete slab. The double-layer curing formwork uses a double-plate nailed structure, and the joints are filled with sealant. Double-sided tape is pasted on the bottom of the double-layer curing formwork to form a press-fit connection to prevent grout leakage. The inner layer of the double-layer curing formwork is flexibly connected to the coupler-type steel pipe frame via clips, while the outer formwork is rigidly connected to the coupler-type steel pipe frame via steel pipe couplers. The joints of the double-layer curing formwork are filled with sealant to form an embedded connection. The vertical poles of the pipe scaffold are spaced 800mm apart, and the horizontal poles are spaced 1200mm apart. They are connected to the outside of the double-layer curing formwork by clips. The bottom of the coupler-type steel pipe scaffold is supported on the concrete slab by an adjustable base. After the concrete has set and stabilized, the coupler-type steel pipe scaffold is removed, and the inner formwork is retained for wall curing with the formwork in place. When the center temperature of the composite wall reaches its peak and within 12 hours after the peak, and the concrete strength reaches more than 50% of the design strength, the double-layer curing formwork is removed. After the double-layer curing formwork is removed, subsequent moisture retention and heat preservation measures are immediately started.

[0011] Step 2: For the construction of the composite wall, low-temperature crack-resistant concrete is selected. When the ambient temperature is higher than 25℃, the temperature of the concrete entering the double-layer curing formwork is controlled to be <26℃, and the thickness of the composite wall is >400mm, cooling water pipes are pre-embedded in the composite wall before pouring, and temperature sensors are embedded in the composite wall. After removing the double-layer curing formwork, geotextile is directly covered on the surface of the composite wall, and a water-energy curing film is covered on the outside of the geotextile. An automatic spraying device is used to spray and atomize the surface of the composite wall to maintain the surface moisture content of the composite wall ≥80%. When the ambient temperature is lower than 10℃, after removing the double-layer curing formwork, thermal insulation material is covered to ensure that the surface temperature of the composite wall is ≥5℃ and the temperature difference between the inside and outside is ≤25℃.

[0012] Step 3: Roughen the joint surface of the composite wall construction to a depth of ≥10mm, apply a 1-2mm thick interface agent before pouring, and complete the layered concrete pouring within 30 minutes; over-pour concrete at the construction joint by 200mm, remove the over-poured part after removing the double-layer curing formwork to form a sloping structure with the inside higher than the outside, and at the same time remove the over-poured part to enhance the density of the interface bonding.

[0013] Step 4: Temperature and humidity sensors and strain sensors are installed on the surface, center, bottom, upper middle, and lower middle parts of the composite wall to form a grid monitoring network and collect temperature and strain data in real time. Based on the monitoring data, the cooling water flow, spraying frequency, and insulation coverage are dynamically adjusted through intelligent analysis on the cloud platform. When the temperature control unit detects that the temperature difference between the inside and outside of the double-layer curing template exceeds 20°C, an early warning is automatically activated and insulation measures are strengthened. When the surface moisture content is below 80%, the spraying frequency is automatically increased.

[0014] Furthermore, in step 1, the misalignment of the joints of the double-layer curing formwork is controlled within 1.5mm, the filling depth of the sealing material is ≥5mm, and the width of the bottom sealing tape is ≥30mm; the total cycle of concrete curing with formwork and subsequent moisture retention and heat preservation is ≥14d.

[0015] Furthermore, in step 2, the cooling water pipes are pre-embedded inside the composite wall in a Z-shaped arrangement. The two ends of the cooling water pipes extend out of the composite wall and connect to the cooling water pump pipeline. The horizontal spacing of the cooling water pipes is 1000mm, and the pipe diameter is 40mm. Water is circulated for pre-cooling 2-3 hours before pouring. The cooling water pipes are connected to the variable frequency water pump and flow valve. The inlet of the cooling water pump is connected to the outlet of the cooling tower, and the outlet is connected to the cooling water pipe through a valve. The data acquisition instrument is wirelessly connected to the cloud platform, and the audible and visual alarm is set in the duty room at the construction site with an audible and visual alarm intensity ≥80dB.

[0016] Furthermore, in step 2, the nozzle spacing of the automatic sprinkler device is 50-70cm, the atomized particle size is 70-90μm, and the spraying time interval is no more than 20min. The start-up and shutdown, atomization opening and spraying pressure of the sprinkler device are automatically controlled by monitoring data through wired or wireless means. When the ambient temperature is below 5℃, the wall surface of the composite wall is covered with multiple layers of thermal insulation material, and the outermost layer is made of waterproof material.

[0017] Furthermore, in step 2, the low-temperature crack-resistant concrete includes:

[0018] The mixture of low-heat cement, fly ash, slag, polycarboxylate superplasticizer, binder, and water has the following volumetric mass fractions: low-heat cement 280~350 kg / m³. 3 Fly ash content is 80~120 kg / m³ 3 Slag content is 60~80 kg / m³ 3 Polycarboxylate superplasticizer is used at a rate of 3.5~4.5 kg / m². 3 The adhesive is 400~450 kg / m² 3 Water content is 135~150 kg / m³ 3 At the same time, add 0.6-0.9 kg / m 3 Polypropylene fibers improve the crack resistance of concrete.

[0019] Furthermore, in step 4, the deployment density of temperature and humidity sensors and strain sensors in the gridded monitoring network includes:

[0020] The horizontal spacing is 5m to 10m, and the vertical spacing is 3m to 5m, with intervals of 2-3m. 2At least one temperature and humidity sensor and one strain sensor are installed on the wall surface. The temperature and humidity sensor is connected to the data acquisition instrument via a shielded cable. The input end of the data acquisition instrument is connected to the temperature and humidity sensor and the strain sensor. The output end of the data acquisition instrument controls the variable frequency water pump, air source heat pump, and cooling water pump. It is connected to the cloud platform via a 4G / 5G network, and the data acquisition frequency is 15-25 minutes / time. The early warning response time is <30 seconds. The cloud platform establishes a maintenance parameter prediction model based on historical data to realize real-time adjustment of maintenance measures.

[0021] This invention also provides a construction and maintenance system for composite walls in a top-down construction integrated hub station, comprising:

[0022] The molded curing module consists of a double-layer curing template, a sealing component, and a fastener-type steel pipe frame. The double-layer curing template is a double-plate nailed structure, consisting of an outer template and an inner template, which are connected by quick connectors. The sealing component includes a sealant filling layer and a bottom double-sided adhesive tape. The fastener-type steel pipe frame is detachably connected to the inner template.

[0023] The intelligent temperature and humidity control module includes an automatic sprinkler system, a drip irrigation system, and a temperature and humidity sensor. The temperature and humidity sensor is linked with the sprinkler system and the drip irrigation system to realize automatic control of sprinkler start / stop, atomization opening and sprinkler pressure.

[0024] The cooling temperature control module includes cooling water pipes, a cooling tower, a variable frequency water pump, and a temperature control unit embedded in the composite wall. The cooling water pipes are arranged in a Z-shape, and the water flow rate is adjusted by the temperature control unit.

[0025] The heat preservation and moisture retention module includes a water energy curing membrane, geotextile and thermal insulation quilt, which can be adapted to the moisture retention and heat preservation needs under different ambient temperatures.

[0026] The monitoring and early warning module consists of a data acquisition unit, a cloud platform, and an audible and visual alarm. The data acquisition unit receives data from the temperature and humidity sensor and the strain sensor and transmits it to the cloud platform. The cloud platform generates a temperature-strain change curve, and the audible and visual alarm issues an audible and visual alarm when the data exceeds the threshold.

[0027] Furthermore, in the molded curing module, the sealant filling depth is ≥5mm, and the double-sided tape width is ≥30mm. The fastener-type steel pipe frame is connected to the inner template through buckles.

[0028] Furthermore, in the intelligent temperature and humidity control module, the nozzle spacing of the sprinkler device is 60cm, and the atomized particle size is 80μm; the drip irrigation device has a drip head flow rate of 3L / h; the temperature and humidity sensor accuracy is ≥0.1℃; the main sprinkler water pipe is arranged horizontally along the top of the fastener-type steel pipe frame, and the branch sprinkler water pipes are led vertically down to the nozzles; the sprinkler water pipe is connected to the outlet of the variable frequency water pump; the nozzles are installed on the sprinkler water pipe through a T-joint; the nozzles are evenly arranged with a spacing of 60cm, 50cm from the wall surface, and the spray angle is 30°.

[0029] Furthermore, in the cooling temperature control module, the cooling water pipes have a diameter of 40mm and a horizontal spacing of 1000mm, connecting the variable frequency water pump and the cooling tower. The inlet of the variable frequency water pump is connected to the water tank, and the outlet of the variable frequency water pump is connected to the spray water pipe. The variable frequency water pump control terminal is linked with the data acquisition instrument. The heat exchanger in the air source heat pump is immersed in the water tank. The control circuit of the air source heat pump is connected to the data acquisition instrument. The temperature control unit adjusts the opening of the flow valve based on the temperature data of the center of the wall.

[0030] Furthermore, in the monitoring and early warning module, the temperature and humidity sensors and strain sensors are deployed at a density of 2m. 2 ~3m 2 At least one, with an audible and visual alarm intensity ≥80dB.

[0031] Compared with the prior art, the superior effects of the present invention are as follows:

[0032] 1. The comprehensive curing method for the construction of composite walls in the cut-and-cover reverse construction method of integrated hub stations described in this invention effectively extends the curing period of the composite wall in the early stage of demolding by seamlessly connecting curing with formwork and moisturizing and heat preservation after demolding. It significantly inhibits the rate of water evaporation on the concrete surface, solves the problem of surface defects caused by excessive early water loss, and significantly improves the uniformity of concrete strength development and the rate of strength compliance.

[0033] 2. The comprehensive maintenance method for the construction of composite walls in the cut-and-cover reverse construction method of integrated hub stations described in this invention achieves precise control of the temperature difference between the inside and outside of the composite wall through the synergistic effect of the precise temperature and humidity control system and the cooling temperature control module. The internal and external temperature difference is strictly controlled within 25℃, which greatly reduces the risk of temperature stress cracks and significantly reduces the incidence of temperature cracks. It can meet the construction requirements under different seasons and different climatic conditions.

[0034] 3. The comprehensive maintenance method for the construction of composite walls in integrated hub stations using the cut-and-cover reverse construction method described in this invention relies on intelligent monitoring and dynamic control technology throughout the entire maintenance process to achieve automation, precision, and closed-loop control of the maintenance process, significantly reducing manual intervention and significantly improving maintenance efficiency; at the same time, it enables the collection, storage, and traceability of maintenance data throughout the entire process, providing technical support for engineering quality control and process traceability.

[0035] 4. The integrated maintenance method for composite wall construction in the cut-and-cover reverse construction method of the integrated hub station described in this invention has modular and combinable features for each functional module. It can be flexibly configured according to the thickness, structural form and construction environment of the composite wall, and has strong versatility and adaptability. It is applicable to composite wall maintenance operations under various working conditions and has broad application value and market prospects. Attached Figure Description

[0036] Figure 1This is a flowchart of the comprehensive maintenance method for the construction of composite walls in the cut-and-cover reverse construction integrated hub station;

[0037] Figure 2 This is a schematic diagram of the formwork-supported curing module structure in the comprehensive curing method for the composite wall construction of the integrated hub station using the cut-and-cover reverse construction method.

[0038] Figure 3 This is a schematic diagram of the layout of cooling water pipes and spraying devices in the comprehensive maintenance method for the composite wall construction of the cut-and-cover integrated hub station described above;

[0039] Figure 4 This is a schematic diagram of the intelligent detection system in the comprehensive maintenance method for the composite wall construction of the integrated hub station using the cut-and-cover reverse construction method;

[0040] Figure label:

[0041] 1. Concrete slab surface; 2. Double-layer curing formwork; 3. Sealant; 4. Double-sided tape; 5. Coupler-type steel pipe frame; 6. Wall; 7. Cooling tower; 8. Cooling water pump; 9. Cooling water pipe; 10. Geotextile; 11. Sprinkler head; 12. Spray water pipe; 13. Variable frequency water pump; 14. Air source heat pump; 15. Water tank; 16. Temperature and humidity sensor; 17. Data acquisition instrument. Detailed Implementation

[0042] To better understand the above-mentioned objectives, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0043] Example

[0044] like Figure 1 As shown, the comprehensive maintenance method for the composite wall construction of the cut-and-cover integrated hub station includes:

[0045] Step 1: Add a separate double-layer curing formwork 2 to the outer side of the single-sided formwork of the composite wall. The foundation surface of the composite wall construction is a concrete slab 1. The double-layer curing formwork 2 adopts a double-plate nailed structure, and the joints are filled with sealant 3. Double-sided tape 4 is pasted on the bottom of the double-layer curing formwork 2 to form a press-fit connection to prevent grout leakage. The inner layer of the double-layer curing formwork 2 is flexibly connected to the fastener-type steel pipe frame 5 through clips. The outer formwork of the double-layer curing formwork 2 is rigidly connected to the fastener-type steel pipe frame 5 through steel pipe fasteners. The joints of the double-layer curing formwork 2 are sealed with sealant 3 to form an embedded connection. The uprights of the steel pipe frame 5 are spaced 800mm apart, and the horizontal bars are spaced 1200mm apart. They are connected to the outside of the double-layer curing template 2 by clips. The bottom of the steel pipe frame 5 is supported on the concrete slab 1 by an adjustable test base. After the concrete has set and stabilized, the steel pipe frame is removed, and the inner template is retained for wall 6 curing with the template. When the center temperature of the composite wall 6 reaches its peak and within 12 hours after the peak, and the concrete strength reaches more than 50% of the design strength, the double-layer curing template 2 is removed. After the double-layer curing template 2 is removed, subsequent moisture retention and heat preservation measures are immediately started.

[0046] Step 2: Low-temperature crack-resistant concrete is used for the construction of the composite wall. When the ambient temperature is higher than 25℃, the temperature of the concrete entering the double-layer curing formwork 2 is controlled to be <26℃. When the thickness of the composite wall 6 is >400mm, cooling water pipes 9 are pre-embedded in the composite wall 6 before pouring, and temperature sensors 16 are embedded in the composite wall 6. After removing the double-layer curing formwork 2, geotextile 10 is directly covered on the surface of the composite wall 6, and a water-energy curing film is covered on the outside of the geotextile 10. An automatic spraying device is used to spray and atomize the surface of the composite wall to maintain the surface moisture content of the composite wall 6 ≥80%. When the ambient temperature is lower than 10℃, insulation material is covered after removing the double-layer curing formwork 2 to ensure that the surface temperature of the composite wall 6 is ≥5℃ and the temperature difference between the inside and outside is ≤25℃.

[0047] Step 3: Roughen the construction joint surface of the composite wall to a depth of ≥10mm, apply a 1-2mm thick interface agent before pouring, and complete the layered concrete pouring within 30 minutes; over-pour concrete 200mm at the construction joint, remove the over-poured part after removing the double-layer curing formwork 2 to form a sloping structure with the inside higher than the outside, and at the same time remove the over-poured part to enhance the interface bonding density.

[0048] Step 4: Temperature and humidity sensors 16 and strain sensors are installed on the surface, center, bottom, upper middle, and lower middle parts of the composite wall 6 to form a grid monitoring network, collecting temperature and strain data in real time. Based on the monitoring data, intelligent analysis is performed through a cloud platform to dynamically adjust the cooling water flow rate, spray frequency, and insulation coverage. When the temperature control unit detects that the temperature difference between the inside and outside of the double-layer curing formwork exceeds 20°C, an early warning is automatically activated and insulation measures are strengthened. First, the curing water temperature is finely adjusted. Before the hydration heat of the concrete reaches its peak, the air-source water supply temperature is moderately increased by 3-5°C to accelerate the curing process. Surface heat is replenished to increase surface temperature; secondly, the frequency of the water circulation pump of the air source heat pump 14 is increased to improve the circulation speed of warm water and make the heat exchange between the warm water and the concrete surface more uniform; finally, the leaks in the warm water pipes, curing layer and interface gaps of the air source heat pump 14 are checked to prevent the loss of warm water and local cooling of the surface. If the ambient temperature is too low, explosion-proof warm air blowers are placed around the curing area to form a local closed heat preservation environment, slightly increasing the ambient temperature (5~8℃) and directly reducing the surface temperature difference. At the same time, the spraying frequency is automatically increased when the surface moisture content is below 80%.

[0049] Furthermore, in step 1, the misalignment of the joints of the double-layer curing formwork 2 is controlled within 1.5mm. The double-layer curing formwork 2 is a 15mm thick double-layer plywood. The filling depth of the sealant is ≥5mm, and the width of the bottom sealing tape is ≥30mm. The total cycle of concrete curing with formwork and subsequent moisture retention and heat preservation is ≥14 days.

[0050] Furthermore, in step 2, the cooling water pipes 9 are pre-embedded inside the composite wall 6 in a Z-shaped arrangement. The two ends of the cooling water pipes 9 extend out of the composite wall and connect to the cooling water pump 8. The horizontal spacing of the cooling water pipes 9 is 1000mm, and the pipe diameter is 40mm. Water is circulated for pre-cooling 2-3 hours before pouring. The cooling water pipes 9 are connected to the variable frequency water pump 13 and the flow valve. The inlet of the cooling water pump 8 is connected to the outlet of the cooling tower 7, and the outlet is connected to the cooling water pipes 9 through a valve. Then, water energy curing membrane and thermal insulation blankets are prepared, and they are flexibly selected according to the ambient temperature. The data acquisition instrument 17 is wirelessly connected to the cloud platform, and the sound and light alarm is set in the duty room of the construction site. The sound and light alarm intensity is ≥80dB.

[0051] The automatic sprinkler system has a nozzle spacing of 50-70cm, an atomized particle size of 70-90μm, and a spraying interval of no more than 20 minutes. Drip irrigation devices are installed on the side walls with a drip flow rate of 3L / h. The PLC controller is installed in the control cabinet at the construction site and automatically controls the start and stop of the sprinkler system, the atomization degree, and the spraying pressure through wired or wireless means. When the ambient temperature is below 5℃, the composite wall surface is covered with multiple layers of insulation material, with the outermost layer being waterproof material.

[0052] Furthermore, in step 2, the low-temperature crack-resistant concrete includes:

[0053] The mixture of low-heat cement, fly ash, slag, polycarboxylate superplasticizer, binder, and water has the following volumetric mass fractions: low-heat cement 280~350 kg / m³. 3 Fly ash content is 80~120 kg / m³ 3 Slag content is 60~80 kg / m³ 3 Polycarboxylate superplasticizer is used at a rate of 3.5~4.5 kg / m². 3 The adhesive is 400~450 kg / m² 3 Water content is 135~150 kg / m³ 3 At the same time, add 0.6-0.9 kg / m 3 Polypropylene fibers improve the crack resistance of concrete; before concrete pouring, a quality pre-control procedure is implemented, which ensures that the pouring temperature meets environmental requirements by ensuring the supply of raw materials in a dedicated warehouse, testing the workability and slump of the concrete before it leaves the factory, and monitoring the pouring temperature in real time.

[0054] Furthermore, in step 4, the deployment density of the temperature and humidity sensors 16 and strain sensors in the gridded monitoring network includes:

[0055] The horizontal spacing is 5m to 10m, and the vertical spacing is 3m to 5m, with intervals of 2-3m. 2 At least one temperature and humidity sensor 16 and a strain sensor are installed on the wall surface. The temperature and humidity sensor 16 is connected to the data acquisition instrument 17 via a shielded cable. The input terminal of the data acquisition instrument 17 is connected to the temperature and humidity sensor 16 and the strain sensor. The output terminal of the data acquisition instrument 17 controls the variable frequency water pump 13, the air source heat pump 14, and the cooling water pump 8. It is connected to the cloud platform via a 4G / 5G network. The data acquisition frequency is 15-25 minutes / time. The early warning response time is <30 seconds. The cloud platform establishes a maintenance parameter prediction model based on historical data to realize the forward-looking adjustment of maintenance measures.

[0056] This invention also provides a construction and maintenance system for composite walls in a top-down construction integrated hub station, comprising:

[0057] like Figures 2 to 4 As shown, the molded curing module consists of a double-layer curing template 2, a sealing component, and a fastener-type steel pipe frame. The double-layer curing template 2 is a double-plate nailed structure, composed of an outer template and an inner template, which are connected by quick connectors. The sealing component includes a sealant 3 filling layer and a bottom-length double-sided adhesive tape 4. The fastener-type steel pipe frame is detachably connected to the inner template. Through the design of the double-layer curing template 2 and the sealing component, the inner template is retained for molded curing for 2 days while the double-layer curing template 2 is rotated, thus extending the moisture retention and heat preservation time.

[0058] The intelligent temperature and humidity control module includes an automatic sprinkler device, a drip irrigation device, and a temperature and humidity sensor 16. The temperature and humidity sensor 16 is linked with the sprinkler device and the drip irrigation device to realize automatic control of sprinkler start and stop, atomization opening and sprinkler pressure.

[0059] The cooling temperature control module includes a cooling water pipe 9 embedded in the wall of the composite wall, a cooling tower, a variable frequency water pump 13 and a temperature control unit. The cooling water pipe 9 is arranged in a Z-shape and the water flow rate is adjusted by the temperature control unit.

[0060] The heat preservation and moisture retention module includes a water energy curing membrane, geotextile 10 and heat preservation cotton quilt, which are adapted to the moisture retention and heat preservation needs under different ambient temperatures.

[0061] The monitoring and early warning module consists of a data acquisition instrument 17, a cloud platform, and an audible and visual alarm. The data acquisition instrument 17 receives data from the temperature sensor 16 and the strain sensor and transmits it to the cloud platform. The cloud platform generates a temperature-strain change curve, and the audible and visual alarm issues an audible and visual alarm when the data exceeds the threshold.

[0062] Furthermore, in the molded curing module, the sealant 3 has a filling depth of ≥5mm and a double-sided tape width of ≥30mm; the disassembly of the outer frame adopts a fastener-type steel pipe frame 5, which is connected to the inner template through buckles.

[0063] Furthermore, in the intelligent temperature and humidity control module, the nozzle spacing of the sprinkler device is 60cm, and the atomized particle size is 80μm; the drip flow rate of the drip irrigation device is 3L / h; the temperature and humidity sensor accuracy is ≥0.1℃; the main sprinkler pipe 12 is arranged horizontally along the top of the fastener-type steel pipe frame 5, and the branch pipes of the sprinkler pipe 12 are vertically led down to the nozzles 11; the sprinkler pipe 12 is connected to the outlet of the variable frequency water pump 13; the nozzles 11 are installed on the sprinkler pipe 12 through a three-way connector; the nozzles 11 are evenly arranged with a spacing of 60cm, 50cm from the wall surface, and the spray angle is 30°.

[0064] Furthermore, in the cooling temperature control module, the cooling water pipe 9 has a diameter of 40mm and a horizontal spacing of 1000mm. It connects the variable frequency water pump 13 to the cooling tower. The inlet of the variable frequency water pump 13 is connected to the water tank 15, and the outlet of the variable frequency water pump 13 is connected to the spray water pipe 12. The control terminal of the variable frequency water pump 13 is linked with the data acquisition instrument 17. The heat exchanger in the air source heat pump 14 is immersed in the water tank 15. The control circuit of the air source heat pump 14 is connected to the data acquisition instrument 17. The temperature control unit adjusts the opening of the flow valve based on the temperature data of the center of the wall.

[0065] Furthermore, in the monitoring and early warning module, the temperature and humidity sensor 16 and the strain sensor are arranged at a density of at least one per 2m²~3m², and the audible and visual alarm intensity is ≥80dB.

[0066] This invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims.

Claims

1. A comprehensive maintenance method for the construction of composite walls in a combined hub station using the cut-and-cover reverse construction method, characterized in that, include: Step 1: Add a separate double-layer curing formwork to the outer side of the single-sided formwork of the composite wall. The foundation surface for the composite wall construction is a concrete slab. The double-layer curing formwork uses a double-plate nailed structure, and the joints are filled with sealant. Double-sided tape is pasted on the bottom of the double-layer curing formwork to form a press-fit connection to prevent grout leakage. The inner layer of the double-layer curing formwork is flexibly connected to the coupler-type steel pipe frame via clips, while the outer formwork is rigidly connected to the coupler-type steel pipe frame via steel pipe couplers. The joints of the double-layer curing formwork are filled with sealant to form an embedded connection. The vertical poles of the steel pipe scaffold are spaced 800mm apart, and the horizontal poles are spaced 1200mm apart. They are connected to the outside of the double-layer curing formwork by clips. The bottom of the coupler-type steel pipe scaffold is supported on the concrete slab by an adjustable base. After the concrete has set and stabilized, the coupler-type steel pipe scaffold is removed, and the inner formwork is retained for wall curing with the formwork in place. When the center temperature of the composite wall reaches its peak and within 12 hours after the peak, and the concrete strength reaches more than 50% of the design strength, the double-layer curing formwork is removed. After the double-layer curing formwork is removed, subsequent moisture retention and heat preservation measures are immediately started. Step 2: For the construction of the composite wall, low-temperature crack-resistant concrete is selected. When the ambient temperature is higher than 25℃, the temperature of the concrete entering the double-layer curing formwork is controlled to be <26℃. When the thickness of the composite wall is >400mm, cooling water pipes are pre-embedded in the composite wall before pouring, and temperature sensors are embedded in the composite wall. After removing the double-layer curing formwork, geotextile is directly covered on the surface of the composite wall, and a water-energy curing film is covered on the outside of the geotextile. An automatic spraying device is used to spray and atomize the surface of the composite wall to maintain the surface moisture content of the composite wall ≥80%. When the ambient temperature is lower than 10℃, after removing the double-layer curing formwork, insulation material is covered to ensure that the surface temperature of the composite wall is ≥5℃ and the temperature difference between the inside and outside is ≤25℃. Step 3: Roughen the joint surface of the composite wall construction to a depth of ≥10mm, apply a 1-2mm thick interface agent before pouring, and complete the layered concrete pouring within 30 minutes; over-pour concrete at the construction joint by 200mm, remove the over-poured part after removing the double-layer curing formwork to form a sloping structure with the inside higher than the outside, and at the same time remove the over-poured part to enhance the density of the interface bonding. Step 4: Install temperature and humidity sensors and strain sensors on the surface, center, bottom, upper middle, and lower middle parts of the composite wall to form a grid monitoring network and collect temperature and strain data in real time. Based on the monitoring data, the system will intelligently analyze the data through a cloud platform and dynamically adjust the cooling water flow, spraying frequency, and insulation coverage. When the temperature control unit detects that the temperature difference between the inside and outside of the double-layer curing template exceeds 20°C, it will automatically activate the warning and strengthen the insulation measures. When the surface moisture content is below 80%, it will automatically increase the spraying frequency.

2. The comprehensive maintenance method for the composite wall construction of a combined hub station using the cut-and-cover reverse construction method according to claim 1, characterized in that, In step 1, the misalignment of the joints of the double-layer curing formwork is controlled within 1.5mm, the filling depth of the sealant is ≥5mm, and the width of the bottom sealing tape is ≥30mm; the total cycle of concrete curing with formwork and subsequent moisture retention and heat preservation is ≥14d.

3. The comprehensive maintenance method for the construction of composite walls in a combined hub station using the cut-and-cover reverse construction method according to claim 1, characterized in that, In step 2, the cooling water pipes are pre-embedded inside the composite wall in a Z-shaped arrangement. The two ends of the cooling water pipes extend out of the composite wall and connect to the cooling water pump pipeline. The horizontal spacing of the cooling water pipes is 1000mm, and the pipe diameter is 40mm. Water is circulated for pre-cooling 2-3 hours before pouring. The cooling water pipes are connected to the variable frequency water pump and flow valve. The inlet of the cooling water pump is connected to the outlet of the cooling tower, and the outlet is connected to the cooling water pipe through a valve. The data acquisition instrument is wirelessly connected to the cloud platform, and the audible and visual alarm is set in the duty room at the construction site with an audible and visual alarm intensity ≥80dB. The nozzle spacing of the automatic sprinkler device is 50-70cm, the atomized particle size is 70-90μm, and the spraying time interval is no more than 20min. The start-up and shutdown, atomization opening and spraying pressure of the sprinkler device are automatically controlled by monitoring data through wired or wireless means. When the ambient temperature is below 5℃, the wall surface of the composite wall is covered with multiple layers of thermal insulation material, and the outermost layer is waterproof material.

4. The comprehensive maintenance method for the composite wall construction of a combined hub station using the cut-and-cover reverse construction method according to claim 1, characterized in that, In step 2, the low-temperature crack-resistant concrete includes: The mixture of low-heat cement, fly ash, slag, polycarboxylate superplasticizer, binder, and water has the following volumetric mass fractions: low-heat cement 280~350 kg / m³. 3 Fly ash content is 80~120 kg / m³ 3 Slag content is 60~80 kg / m³ 3 Polycarboxylate superplasticizer is used at a rate of 3.5~4.5 kg / m². 3 The adhesive is 400~450 kg / m² 3 Water content is 135~150 kg / m³ 3 At the same time, 0.6-0.9 kg / m³ of polypropylene fiber is added to improve the crack resistance of concrete.

5. The comprehensive maintenance method for the construction of composite walls in a combined hub station using the cut-and-cover reverse construction method according to claim 1, characterized in that, In step 4, the deployment density of temperature and strain sensors in the gridded monitoring network includes: The horizontal spacing is 5m to 10m, and the vertical spacing is 3m to 5m, with intervals of 2-3m. 2 At least one temperature and humidity sensor and one strain sensor are installed on the wall surface. The temperature and humidity sensor is connected to the data acquisition instrument via a shielded cable. The input end of the data acquisition instrument is connected to the temperature and humidity sensor and the strain sensor. The output end of the data acquisition instrument controls the variable frequency water pump, air source heat pump, and cooling water pump. It is connected to the cloud platform via a 4G / 5G network. The data acquisition frequency is 15-25 minutes / time. The early warning response time is <30 seconds. The cloud platform establishes a maintenance parameter prediction model based on historical data to realize the forward-looking adjustment of maintenance measures.

6. A construction and maintenance system for composite walls in a cut-and-cover integrated hub station using the top-down construction method, applied to the comprehensive maintenance method for composite walls in a cut-and-cover integrated hub station as described in any one of claims 1 to 5, characterized in that, include: The molded curing module consists of a double-layer curing template, a sealing component, and a fastener-type steel pipe frame. The double-layer curing template is a double-plate nailed structure, consisting of an outer template and an inner template, which are connected by quick connectors. The sealing component includes a sealant filling layer and a bottom double-sided adhesive tape. The fastener-type steel pipe frame is detachably connected to the inner template. The intelligent temperature and humidity control module includes an automatic sprinkler system, a drip irrigation system, and a temperature and humidity sensor. The temperature and humidity sensor is linked with the sprinkler system and the drip irrigation system to realize automatic control of sprinkler start / stop, atomization opening and sprinkler pressure. The cooling temperature control module includes cooling water pipes, a cooling tower, a variable frequency water pump, and a temperature control unit embedded in the composite wall. The cooling water pipes are arranged in a Z-shape, and the water flow rate is adjusted by the temperature control unit. The heat preservation and moisture retention module includes a water energy curing membrane, geotextile and thermal insulation quilt, which can be adapted to the moisture retention and heat preservation needs under different ambient temperatures. The monitoring and early warning module consists of a data acquisition unit, a cloud platform, and an audible and visual alarm. The data acquisition unit receives data from the temperature and humidity sensor and the strain sensor and transmits it to the cloud platform. The cloud platform generates a temperature-strain change curve, and the audible and visual alarm issues an audible and visual alarm when the data exceeds the threshold.

7. The integrated maintenance system for composite wall construction of a combined hub station using the cut-and-cover reverse construction method according to claim 6, characterized in that, In the molded curing module, the sealant filling depth is ≥5mm, and the double-sided tape width is ≥30mm. The fastener-type steel pipe frame is connected to the inner template through buckles.

8. The integrated maintenance system for composite wall construction of a combined hub station using the cut-and-cover reverse construction method according to claim 6, characterized in that, In the intelligent temperature and humidity control module, the nozzle spacing of the sprinkler device is 60cm and the atomized particle size is 80μm; the drip irrigation device has a drip head flow rate of 3L / h; the temperature and humidity sensor accuracy is ≥0.1℃; the main sprinkler water pipe is arranged horizontally along the top of the fastener-type steel pipe frame, and the branch sprinkler water pipes are led vertically down to the nozzles. The sprinkler water pipe is connected to the outlet of the variable frequency water pump, and the nozzles are installed on the sprinkler water pipe through a T-joint. The nozzles are evenly arranged with a spacing of 60cm, 50cm from the wall surface, and the spray angle is 30°.

9. The integrated maintenance system for composite wall construction of a combined hub station using the cut-and-cover reverse construction method according to claim 6, characterized in that, In the cooling temperature control module, the cooling water pipes have a diameter of 40mm and a horizontal spacing of 1000mm. They connect the variable frequency water pump to the cooling tower. The inlet of the variable frequency water pump is connected to the water tank, and the outlet of the variable frequency water pump is connected to the spray water pipe. The variable frequency water pump control terminal is linked with the data acquisition instrument. The heat exchanger in the air source heat pump is immersed in the water tank. The control circuit of the air source heat pump is connected to the data acquisition instrument. The temperature control unit adjusts the opening of the flow valve based on the temperature data of the center of the wall.

10. The integrated maintenance system for composite wall construction of a combined hub station using the cut-and-cover reverse construction method according to claim 6, characterized in that, In the monitoring and early warning module, the temperature and humidity sensors and strain sensors are deployed at a density of 2m. 2 ~3m 2 At least one, with an audible and visual alarm intensity ≥80dB.

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