Method for backfilling old civil air defense tunnel under urban water-rich stratum

Abstract

The invention provides a backfilling method for an old civil air defense tunnel under an urban water-rich stratum. The backfilling method is characterized by comprising the following steps that S1, sand for tunnel backfilling is prepared, specifically, the sand for backfilling is stacked at an outlet of the civil air defense tunnel or near a vertical shaft; s2, a sand blowing working pit is constructed, specifically, the sand blowing working pit is constructed on the periphery of the backfill sand stacked in the step S1; s3, dewatering in the tunnel is pumped and drained through an outlet of the civil air defense tunnel or a vertical shaft by using a submersible pump, so that the water level in the tunnel is lowered to the position 1-2 m below the vault of the civil air defense tunnel, and a construction space is provided for follow-up operation; s4, pipeline arrangement; s5, sand blowing of the film bag; and S6, grouting construction is conducted. The construction method solves the problems that when the old civil air defense tunnel is backfilled with conventional foam concrete, water pumping potential safety hazards are large, the construction cost is high, the construction period is long, and the urban site is limited.

Description

Technical Field

[0001] The invention belongs to the technical field of construction engineering, and specifically relates to a backfill construction method for an old civil air defense tunnel under a water-rich stratum in a city. Background Art

[0002] In the 1960s and 1970s, under the call of "dig deep holes, store up food, and do not seek hegemony", many Chinese cities, especially urban core areas, built a large number of civil air defense projects. Early urban civil air defense fortifications were located under roads with heavy traffic and dense pipelines. Due to their age, low construction standards, and lack of maintenance, their construction limits no longer meet the current regulatory requirements, and they have cracked, seeped, and suffered from water damage to varying degrees. Most of them have lost their war protection functions, which not only greatly affects the applicability and safety of their civil air defense projects, but also brings certain safety hazards to underground building structures that are in operation and to be built.

[0003] With the progress of economy and society and the construction of new civil air defense projects, some early and old civil air defense fortifications have small space, are built a long time ago, are abandoned and in disrepair, have degraded performance, have poor waterproofing quality, have serious leakage, and have become less stable after being soaked in water for a long time. They can no longer play the role of civil air defense projects in the new era, and backfilling is adopted to eliminate safety hazards.

[0004] At present, the backfill of old civil air defense tunnels in the early stage is generally made of foamed concrete backfill or poured concrete backfill. Because foamed concrete is diluted by water and bubbles are destroyed, foamed concrete backfill can only be constructed in the civil air defense tunnel without water. For civil air defense projects with serious leakage or below the groundwater level, water needs to be pumped out and water stoppage and leakage plugging are carried out. A large amount of water pumping will break the force balance in the civil air defense tunnel, causing safety hazards such as collapse and water gushing. In addition, water stoppage and leakage plugging for serious tunnel leakage consume a lot of manpower and material resources, with high costs and long construction period. The cost of pouring underwater concrete backfill is high, and construction requires drilling holes in the road surface. Drilling holes in the main roads in busy downtown areas will inevitably lead to traffic "paralysis", which will have an adverse impact on the city's image and environmental protection. In addition, high-strength concrete backfill is not conducive to the future development and utilization of urban underground space. Summary of the invention

[0005] In response to the above problems, the present invention provides a method for backfilling old civil air defense tunnels under water-rich strata in cities, so as to solve the problems of great pumping safety hazards, high construction costs, long construction period, and limited urban sites when conventional foam concrete is used to backfill old civil air defense tunnels.

[0006] The present invention is achieved through the following technical solutions.

[0007] A method for backfilling an old civil air defense tunnel under a water-rich stratum in an urban area, characterized by comprising the following steps:

[0008] S1. Preparation of sand for tunnel backfill

[0009] Pile the backfill sand near the exit of the civil air defense tunnel or the shaft;

[0010] S2. Construction sand blowing pit

[0011] A sand blowing pit is constructed around the backfill sand piled in step S1;

[0012] S3. Precipitation in the cave

[0013] Use a submersible pump to pump out water through the civil air defense tunnel exit or shaft to lower the water level in the tunnel to 1-2m below the arch of the civil air defense tunnel, so as to provide construction space for subsequent operations;

[0014] S4. Pipeline layout

[0015] After the dewatering in the tunnel is completed in step S3 and there is an operating space, the sand blowing pipeline is first laid between the sand blowing working pit and the designed position for laying the membrane bag. The sand blowing pipeline outside the civil air defense tunnel and at the exit of the civil air defense tunnel or in the shaft adopts a hard pipe, and the sand blowing pipeline in the tunnel adopts a high-pressure wear-resistant water hose, and a buoy is fixed on the high-pressure wear-resistant water hose every 3 to 6 meters;

[0016] S5, film bag sand blowing

[0017] The measurement and layout are carried out according to the designed position of the film bag laying. After the measurement and layout are completed, the sand blowing thickness of the film bag is taken as one layer, and the film bag sand blowing construction is carried out layer by layer from bottom to top until the backfill height is reached; and the film bag sand blowing construction of each layer is carried out in the following way, taking each film bag as a section, and the film bag laying and sand blowing construction are carried out section by section along the length direction of the tunnel until the required backfill length of the tunnel is reached; wherein, the film bag is water permeable; the sand blowing thickness in each film bag of the same layer is the same; the specific method of sand blowing construction is to flush the stacked backfill sand into the sand blowing working pit by spraying high-pressure water at a sand-water mass ratio of 1:3-5, so that the sand and water mixture flows evenly into the working pit, and then the sand and water mixture is blown from the working pit along the sand blowing pipeline into the laid film bag by a high-pressure mud pump until the film bag is full;

[0018] S6. Grouting construction

[0019] Before the last layer of membrane bag sand blowing is completed in step S5, a grouting pipe is reserved in advance on the tunnel vault; after the membrane bag sand blowing is completed in step S5, the sand body is consolidated and settled, and grouting is backfilled and compacted from the top surface of the last layer of membrane bag to the arc position at the top of the tunnel through the reserved grouting pipe.

[0020] Preferably, the backfill sand is river sand, preferably river sand with a fineness modulus of fine sand; the sand blowing working pit is formed by digging downward from the ground and laying brick walls and plastering the surface, or by using a prefabricated mud box made of iron sheets.

[0021] Preferably, in step S4, the sandblasting pipeline is laid out in a manner that avoids crossing obstacles and forming sharp bends, and at the same time ensures that the pipeline joints are firmly sealed to prevent leakage from causing blockage along the line.

[0022] Preferably, the length of the membrane bag is 30 to 50 m, the width of the membrane bag is determined according to the cross-sectional size of the tunnel, the membrane bag is made of polypropylene woven cloth, and two sand blasting ports for connecting to the sand blasting pipeline are arranged at both ends of the membrane bag; the diameter of the sand blasting port is 15 to 25 cm, and the length is 30 to 50 cm.

[0023] Preferably, in step S5, during measurement and layout, for the shallow water construction area of ​​the tunnel, the membrane bags are laid and positioned by artificial underwater operations; for the deep water construction area of ​​the tunnel, kayaks or wooden boats are used to lay and position the membrane bags.

[0024] Preferably, in step S5, the film bags are laid with the sand blowing ports facing upward, the film bags on the same layer are arranged compactly, the upper and lower film bags are firmly connected by tie rods at the buckles, and the end seams of the upper and lower film bags are staggered by 4 to 6m to prevent through seams.

[0025] Preferably, in step S5, during the sand blowing construction, the four corners of the film bag are first blown to make the film bag sink to the bottom, and then the middle part is blown.

[0026] Preferably, in step S5, during the sand blowing construction, the sand blowing thickness in the membrane bag is controlled to be 0.6 to 1 m. When the thickness of the sand body in the membrane bag is close to the designed thickness, the sand blowing speed is reduced. At the same time, construction personnel are arranged to step on the top surface of the membrane bag to facilitate the discharge of water in the membrane bag and make the sand body in the membrane bag evenly distributed.

[0027] Preferably, in step S5, during the sand blowing construction, a submersible pump is used to pump out water while blowing sand, so as to control the water level in the tunnel to always be 1 to 2 meters below the arch of the civil air defense tunnel.

[0028] Preferably, in step S6, the grouting material is 42.5 grade ordinary Portland cement with a water-cement ratio of 1:1.

[0029] Compared with the prior art, the beneficial effects of the present invention include at least:

[0030] 1. The construction is safe and reliable. Water operation is possible. There is no need to pump out all the water in the tunnel and stop water leakage. Sand can be directly blown backfilled in the civil air defense tunnel, which is safer and more convenient.

[0031] 2. Save costs. The sandblasting material uses river sand, which greatly reduces the cost compared with the previous foam concrete backfill and underwater concrete backfill.

[0032] 3. The construction speed is fast. The sand blowing backfilling method of the present invention saves the construction time of drilling and road surface restoration. There is no need to wait for the time for the concrete strength to rise during the backfilling process. The speed of blowing sand to the film bag is fast, and a lot of construction time can be saved by constructing multiple shafts at the same time.

[0033] 4. It occupies a small area, has a long conveying distance, and is easy to construct. Sand can be blown to both ends simultaneously through the vertical shaft. The sand blowing and conveying distance at each end can reach 600m. There is no need to drill holes on the ground for backfilling, which can solve the problem of rapid backfilling of civil air defense tunnels in confined spaces in cities.

[0034] 5. The backfill quality is reliable. Due to the restraint of the membrane bag and the original structure of the tunnel, the overall stability of the sand body is good. After being saturated and compacted, there will be no uneven settlement. Grouting is performed in the gaps on the top of the sand layer, making the backfill more compact.

[0035] 6. Green and environmentally friendly, sand blowing backfill only requires water and sand, and will not cause pollution or damage to the water, atmosphere, soil and other environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention is further described in detail below with reference to the drawings. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute improper limitations on the present invention.

[0037] Figure 1 A schematic diagram of the backfilling method of the present invention;

[0038] Figure 2 for Figure 1 Schematic diagram outside the Chinese Civil Defense Tunnel;

[0039] Figure 3 for Figure 1 Schematic diagram of the interior of the civil air defense tunnel;

[0040] Figure 4 This is a schematic diagram of the civil air defense tunnel after backfilling is completed;

[0041] Figure 5 for Figure 4 Cross-section at AA in the middle;

[0042] Figure 6 This is the actual construction drawing of the high-pressure mud pump pumping sand in the sand blowing pit;

[0043] Figure 7 Actual construction drawings for pipeline layout;

[0044] Figure 8 Actual construction drawings for membrane bag laying and sand blowing;

[0045] Fig. 9 Actual construction drawings for grouting construction;

[0046] The meanings of the symbols in the above figure are: 1-sand for backfilling, 2-sand blowing working pit, 3-high-pressure mud pump, 4-sand blowing pipeline, 401-high-pressure wear-resistant water hose, 402-PE hard pipe, 5-buoy, 6-high-pressure water gun, 7-water pipe, 8-submersible pump, 9-membrane bag, 10-grouting pipe, 11-cement slurry, 12-bracket, 13-sand and water mixture, 14-ground line, 15-water level line in the tunnel, 16-civil defense tunnel exit or shaft. DETAILED DESCRIPTION

[0047] The following is a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] Example 1

[0049] A method for backfilling old civil air defense tunnels under urban water-rich strata, please refer to Figures 1 to 5 , which comprises the following steps:

[0050] S1. Preparation of sand for tunnel backfill

[0051] See also Figure 1 and Figure 2 , the backfill sand 1 is piled near the exit of the civil air defense tunnel or the shaft 16; wherein, the backfill sand 1 is river sand, and the river sand fineness modulus is selected into three types: medium coarse sand, fine sand, and extra fine sand. The medium coarse sand has a larger particle size, a short pumping distance, and is easy to block the pipe; the fine sand has a lower cost, good fluidity in the sand blowing operation, and a long pumping distance; the extra fine sand has a higher mud content and a large loss during the operation; after comprehensive comparison, in this embodiment, river sand with a fineness modulus of fine sand is selected as the backfill sand;

[0052] S2. Construction sand blowing pit

[0053] See also Figure 1 and Figure 2 A sand-blasting pit 2 is constructed around the backfill sand 1 piled in step S1, and a steel mesh is laid on the top surface of the sand-blasting pit 2 to filter debris; the sand-blasting pit can be formed by digging downward from the ground and laying brick walls as a sand-water mixing area, or a mud box prefabricated with iron sheets can be used as the sand-blasting pit; in this embodiment, the sand-blasting pit has a size of 3m in length, 2m in width, 2m in height, and a volume of 12 cubic meters, and is formed by digging downward from the ground and laying brick walls;

[0054] S3. Precipitation in the cave

[0055] See also Figure 1 and Figure 3, because the civil air defense tunnel has been in disrepair for a long time, the structural performance has declined, the leakage is serious, and the tunnel is full of water. It is necessary to first reduce the water appropriately, that is, to use a submersible pump 8 to pump out water through the civil air defense tunnel outlet or shaft to reduce the water level in the tunnel to 1 to 2 meters below the arch of the civil air defense tunnel, so as to provide construction space for subsequent operations;

[0056] S4. Pipeline layout

[0057] See also Figures 1 to 3 After the dewatering in the tunnel is completed in step S3 and there is an operating space, the sand-blasting pipeline 4 is first laid between the sand-blasting working pit 2 and the designed position for laying the membrane bag, wherein the sand-blasting pipeline outside the civil air defense tunnel and the exit of the civil air defense tunnel or in the vertical shaft adopts a PE hard pipe 402 with a diameter of 150 mm, and the sand-blasting pipeline in the tunnel adopts a high-pressure wear-resistant water hose 401 with a diameter of 150 mm, and a buoy 5 is fixed on the high-pressure wear-resistant water hose every 5 m to make the sand-blasting pipeline in the tunnel float in the tunnel; when laying the sand-blasting pipeline 4, avoid crossing obstacles and avoid forming too sharp bends, and at the same time ensure that the pipeline joints are firmly sealed to prevent leakage from causing blockage along the line; during the sand-blasting construction, the pipe end of the sand-blasting pipeline is connected to the membrane bag 9 through the sand-blasting port;

[0058] S5, film bag sand blowing

[0059] The membrane bag laying design position is measured and laid out. During the measurement and laying out, for the shallow water construction area of ​​the tunnel, the membrane bag is laid and positioned by artificial underwater operation; for the deep water construction area of ​​the tunnel, the membrane bag is laid and positioned by kayak or wooden boat;

[0060] See also Figure 3 and Figure 4 After the measurement and layout is completed, the film bag sand blowing construction is carried out layer by layer from bottom to top along the height direction of the tunnel, with the sand blowing thickness of the film bag as one layer, until the construction reaches the filling height; and the film bag sand blowing construction of each layer is carried out in the following way, with each film bag as a section, and the film bag is laid and sand blowing construction is carried out section by section along the length direction of the tunnel, that is, after the sand blowing construction of each section of the film bag is completed, the sand blowing pipeline is extended above the film bag section, and then the next adjacent film bag is laid and sand blowing construction is carried out, and the cycle is repeated in sequence until the construction is carried out section by section to the required backfill length of the tunnel, that is, the film bag sand blowing construction of this layer is completed; the extension of the sand blowing pipeline is connected by an inner-lined steel pipe, and the sand blowing pipeline must not be bent to prevent blockage;

[0061] Among them, the length of the membrane bag is 30 to 50m, and the width of the membrane bag is determined according to the cross-sectional size of the tunnel. In this embodiment, the cross-sectional width of the civil air defense tunnel is 4.2m, so the width of the membrane bag is designed to be 6.2m; the membrane bag is made of polypropylene woven cloth and is water-permeable. Two sand blowing ports are arranged at both ends of the membrane bag to connect with the sand blowing pipeline. The diameter of the sand blowing port is 20cm and the length is 40cm; when the membrane bag is laid, the sand blowing port is kept facing upward, and the membrane bags on the same layer are arranged compactly. The upper and lower membrane bags are firmly connected by tie rods at the buckles, and the end seams of the upper and lower membrane bags are staggered by 5m to prevent the occurrence of through seams; the specific method of sand blowing construction is to use a high-pressure water gun to spray high-pressure water at a sand-water mass ratio of 1:4 to flush the stacked backfill sand into the sand blowing working pit, so that the sand and water are evenly mixed and flow into the working pit, and then the sand and water are pumped into the working pit by a high-pressure mud pump The mixed material is blown into the film bag along the sand blowing pipeline from the working pit until the film bag is full; during the sand blowing construction, the thickness of the sand in each film bag of the same layer is controlled to be the same; during the sand blowing construction, the four corners of the film bag are blown and filled first to make the film bag sink to the bottom, and then the middle part is blown and filled, and the thickness of the sand in the film bag is controlled to be 0.6-1m. When the thickness of the sand body in the film bag is close to the designed thickness, the sand blowing speed is reduced, and the construction personnel are arranged to step on the top surface of the film bag to facilitate the discharge of water in the film bag, so that the sand body in the film bag is evenly distributed. At the same time, while blowing sand, a submersible pump is used to pump water to the ground municipal pipeline network to control the water level in the cave to always be 1-2m below the arch of the civil air defense tunnel; in addition, during the sand blowing construction, the submersible pump installed at the exit of the civil air defense tunnel or in the shaft can be connected to the high-pressure water gun through a water pipe, so that part of the water pumped out of the tunnel can be used for sand blowing construction to save water resources;

[0062] S6. Grouting construction

[0063] See also Figure 4 and Figure 5 Before the last layer of membrane bag sand blowing construction is completed in step S5, a grouting pipe 10 is reserved in advance on the tunnel vault; after the membrane bag sand blowing construction in step S5 is completed, after the sand body is consolidated and settled, grouting backfill is carried out from the top surface of the last layer of membrane bag to the arc position at the top of the tunnel through the reserved grouting pipe; the grouting material is 42.5 grade ordinary Portland cement with a water-cement ratio of 1:1.

Claims

1. A method for backfilling old civil air defense tunnels under urban water-rich strata, characterized in that The steps include: S1. Preparation of sand for tunnel backfill Pile the backfill sand near the exit of the civil air defense tunnel or the shaft; S2. Construction sand blowing pit A sand blowing pit is constructed around the backfill sand piled in step S1; S3. Precipitation in the cave Use a submersible pump to pump out water through the civil air defense tunnel exit or shaft to lower the water level in the tunnel to 1-2m below the arch of the civil air defense tunnel, so as to provide construction space for subsequent operations; S4. Pipeline layout After the dewatering in the tunnel is completed in step S3 and there is an operating space, the sand blowing pipeline is first laid between the sand blowing working pit and the designed position for laying the membrane bag. The sand blowing pipeline outside the civil air defense tunnel and at the exit of the civil air defense tunnel or in the shaft adopts a hard pipe, and the sand blowing pipeline in the tunnel adopts a high-pressure wear-resistant water hose, and a buoy is fixed on the high-pressure wear-resistant water hose every 3 to 6 meters; S5, film bag sand blowing The measurement and layout are carried out according to the designed position of the film bag laying. After the measurement and layout are completed, the sand blowing thickness of the film bag is taken as one layer, and the film bag sand blowing construction is carried out layer by layer from bottom to top until the backfill height is reached; and the film bag sand blowing construction of each layer is carried out in the following way, taking each film bag as a section, and the film bag laying and sand blowing construction are carried out section by section along the length direction of the tunnel until the required backfill length of the tunnel is reached; wherein, the film bag is water permeable; the sand blowing thickness in each film bag of the same layer is the same; the specific method of sand blowing construction is to flush the stacked backfill sand into the sand blowing working pit by spraying high-pressure water at a sand-water mass ratio of 1:3-5, so that the sand and water mixture flows evenly into the working pit, and then the sand and water mixture is blown from the working pit along the sand blowing pipeline into the laid film bag by a high-pressure mud pump until the film bag is full; S6. Grouting construction Before the last layer of membrane bag sand blowing is completed in step S5, a grouting pipe is reserved in advance on the tunnel vault; after the membrane bag sand blowing is completed in step S5, the sand body is consolidated and settled, and grouting is backfilled and compacted from the top surface of the last layer of membrane bag to the arc position at the top of the tunnel through the reserved grouting pipe.

2. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 1, characterized in that: The backfill sand is river sand, preferably river sand with a fineness modulus of fine sand; the sand blowing working pit is formed by digging downward from the ground and laying brick walls and plastering the surface, or by using a mud box prefabricated with iron sheets.

3. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 1, characterized in that: In step S4, the sandblasting pipeline is laid out in such a way as to avoid crossing obstacles and forming sharp bends, and at the same time ensure that the pipeline joints are firmly sealed to prevent leakage from causing blockage along the line.

4. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 1, characterized in that: The length of the membrane bag is 30 to 50 meters, the width of the membrane bag is determined according to the cross-sectional size of the tunnel, the membrane bag is made of polypropylene woven cloth, and two sand blowing ports for connecting to the sand blowing pipeline are arranged at both ends of the membrane bag; the diameter of the sand blowing port is 15 to 25 cm, and the length is 30 to 50 cm.

5. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 1, characterized in that: In step S5, during the surveying and setting out, for the shallow water construction area of ​​the tunnel, the membrane bags are laid and positioned by artificial underwater operation; for the deep water construction area of ​​the tunnel, the membrane bags are laid and positioned by kayaking or wooden boats.

6. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 4, characterized in that: In step S5, the sand blowing ports are kept facing upwards when the film bags are laid, the film bags in the same layer are arranged compactly, the upper and lower film bags are firmly connected by tie rods at the buckles, and the end seams of the upper and lower film bags are staggered by 4 to 6m to prevent through seams.

7. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 4, characterized in that: In step S5, during the sand blowing construction, the four corners of the film bag are first blown to make the film bag sink to the bottom, and then the middle part is blown to fill.

8. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 1, characterized in that: In step S5, during the sand blowing construction, the sand blowing thickness in the membrane bag is controlled to be 0.6-1m. When the thickness of the sand body in the membrane bag is close to the designed thickness, the sand blowing speed is reduced, and construction personnel are arranged to step on the top surface of the membrane bag to facilitate the discharge of water in the membrane bag and make the sand body in the membrane bag evenly distributed.

9. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 1, characterized in that: In step S5, during the sand blowing construction, a submersible pump is used to pump out water while blowing sand, so as to control the water level in the tunnel to always be 1 to 2 meters below the arch of the civil air defense tunnel.

10. A method for backfilling old civil air defense tunnels under urban water-rich strata as claimed in claim 1, characterized in that: In step S6, the grouting material is 42.5 grade ordinary Portland cement with a water-cement ratio of 1:1.

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