Water-vapor separation type vacuum preloading construction method for drain board

Abstract

The invention discloses a drainage plate water vapor separation type vacuum preloading construction method, and belongs to the technical field of soft soil foundation construction.The construction method comprises the following steps that firstly, a site is leveled, and a plain soil cushion layer is filled; 2, filling a sand cushion layer; 3, constructing a plastic drainage plate; fourthly, the plastic drainage plate is embedded, a vacuum pipeline is installed, and a water ring vacuum pump is started, so that water and gas in the foundation are gathered into the water collecting well tank body through the drainage plate and the under-membrane pipeline under the negative pressure effect, water vapor is separated in the water collecting well tank body, gas is discharged through the water ring vacuum pump, and water in the water collecting well tank body is discharged through a drainage pump. According to the vacuumizing mode, the water ring vacuum pump only exhausts air, and the drainage pump only drains water, so that the highest efficiency of the two devices is exerted, the problems that a traditional jet pump is large in electricity consumption and high in cost consumption are solved, the efficiency is improved to a certain degree, the cost is saved, the project progress is accelerated, and the project cost is reduced.

Description

Technical Field

[0001] The invention specifically relates to a water vapor separation type vacuum preloading construction method for a drainage board, and belongs to the technical field of soft soil foundation construction. Background Art

[0002] Due to special environmental restrictions such as coastal areas, lakes, and fish ponds, many engineering projects have to be built on soft foundations. Since soft soil roadbeds have undesirable characteristics such as low strength, high compressibility, and large post-construction settlement, they are very harmful to the roadbed and have become one of the key factors affecting project quality, construction period, and project cost. In view of the engineering characteristics of deep soft foundations, vacuum preloading is used to treat the soft foundation, improve the bearing capacity of the soft foundation, and reduce the post-construction settlement of the highway roadbed to meet the requirements of the roadbed for the bearing capacity of the foundation. The vacuum preloading method is to first lay a sand cushion layer on the surface of the soft soil foundation that needs to be reinforced, and then bury a vertical drainage pipe, and then use an airtight sealing membrane to isolate it from the atmosphere. The end of the sealing membrane is buried and pressed, and a vacuum pump or other vacuum means is used to draw a vacuum through the water absorption pipe buried in the sand cushion layer to form a negative pressure under the membrane and increase the effective stress of the foundation.

[0003] However, the traditional vacuum preloading technology vacuum equipment uses a jet pump, which gradually forms a vacuum under the membrane by discharging the circulating water in the pump nest with high intensity and stability, and uses the negative pressure difference to discharge the water and gas in the soil through the ejector to achieve the purpose of soil consolidation. The traditional jet pump needs to maintain a fixed power operation during the entire vacuum period, which consumes a lot of electricity and is costly. Summary of the invention

[0004] The purpose of the present invention is to provide a water-vapor separation vacuum preloading construction method for drainage board in view of the shortcomings of the prior art, which abandons the shortcoming that the jet pump cannot exert the maximum efficiency. Through the water-vapor separation device, the water ring vacuum pump only pumps air and the drainage pump only drains water, which exerts the highest efficiency of the two devices, saves energy to the maximum extent, and is more convenient and economical. To a certain extent, it improves efficiency and saves costs, thereby accelerating the progress of the project and reducing the cost of the project.

[0005] The present invention achieves the above-mentioned purpose through the following technical scheme, a water vapor separation vacuum preloading construction method of a drainage board, during the construction, comprises the following steps: Step 1: Level the site and fill the plain soil cushion layer; Step 2: Filling the sand cushion layer; Step 3: Construction of plastic drainage board; Step 4: bury the plastic drainage board and install the vacuum pipeline; Step 5: Dig a sealing trench; Step 6: Lay the sealing cloth and film; Step 7: Install a vacuum device and connect the vacuum device to the vacuum pipeline; Step 8: Test vacuum and check seals; Step 9: Formal vacuuming and testing begins; Step 10: Vacuum preloading and unloading acceptance; Step 11: Continue pre-pressing after vacuum is released, and remove the sealing film outside the drainage cushion layer outside the slope foot; In step seven, the vacuum device consists of a water collection well tank body, a water ring vacuum pump and a distribution box. A vacuum gauge is installed on the water collection well tank body. A hollow pipe is installed on the input end of the water ring vacuum pump. The water ring vacuum pump is connected to the water collection well tank body through the hollow pipe. A drainage pump is installed inside the water collection well tank body. A water inlet pipe and a drainage pipe are respectively installed on the water collection well tank body. The output end of the drainage pump is connected to the drainage pipe, and the vacuum pipeline is connected to the water collection well tank body through the water inlet pipe.

[0006] Furthermore, in order to penetrate deep into the soft foundation and suck out the water inside the soft foundation, in step three, during the construction of the plastic drain board, first measure and place the board position, then put the machine in place, then put the plastic drain board on the end of the machine casing, then insert the casing into the soil, finally pull out the casing and cut off the drain board, and then move the machine to the next pile position.

[0007] Furthermore, in order to be able to suck out the water in the soft foundation through the drainage board, in step four, first bury one end of the plastic drainage board in the sand cushion layer, then dig a trench on the sand cushion layer, and bury the vacuum pipe in the trench. The vacuum pipe is divided into a vacuum filter pipe main pipe and a branch pipe. The vacuum filter pipe main pipe is arranged in a ring along the outside of the treatment area, with a denser spacing in the middle of less than 35m, and the branch pipes are buried at a spacing of 6m.

[0008] Furthermore, in order to seal the periphery of the preloading area, in step five, a sealing ditch is excavated. The sealing ditch is arranged around the construction area, and it mainly plays the role of periphery sealing in the vacuum preloading construction.

[0009] Furthermore, in order to seal the pre-pressing area, in step six, when laying the sealing cloth and the sealing film, first lay a layer of non-woven geotextile, i.e., the sealing cloth, and then sew it with a portable sewing machine, and reserve a certain length on both sides, then lay the two layers of sealing film in layers to cover the entire vacuum pre-pressing area, and finally lay another layer of non-woven geotextile and sew it with a portable sewing machine.

[0010] Furthermore, in order to ensure the normal progress of the subsequent vacuum preloading, in step eight, during the vacuum test and seal inspection, the vacuum degree is stabilized at above 80 kPa for 5-7 days, and then a layer of geotextile is laid before loading.

[0011] Furthermore, in order to ensure the construction effect during the vacuum preloading process, in step nine, the formal vacuuming and testing begins. After 7-10 days of vacuuming, normal vacuum preloading begins, and monitoring work must be carried out immediately after the vacuuming begins.

[0012] Furthermore, in order to ensure the effect of the completion of the vacuum preloading construction, in step ten, during the vacuum preloading unloading acceptance, the vacuum degree under the membrane in the vacuum preloading reinforcement area needs to be continuously and stably maintained at above 80kPa for 6 months. At the same time, before stopping the vacuuming, the total thickness of the fill is required to reach the total thickness required by the design, the fill elevation is not lower than the equal load top elevation, and the monitored horizontal displacement rate is less than 2mm / day. The earthwork is unloaded after an interval of 2-3 months after stopping the vacuuming, and the settlement rate is required to be less than 3mm / month for three consecutive months before unloading.

[0013] The technical effects and advantages of the present invention are as follows: by starting the water ring vacuum pump, negative pressure is formed inside the water collection well tank body, and then the negative pressure is transmitted to the foundation through the sub-membrane pipeline and the plastic drainage board. Under the action of negative pressure, water and gas in the foundation gather in the water collection well tank body through the drainage board and the sub-membrane pipeline, and the water vapor is separated inside the water collection well tank body, and the gas is discharged through the water ring vacuum pump, and the water inside the water collection well tank body is discharged through the drainage pump. In this vacuuming method, the water ring vacuum pump only draws air and the drainage pump only drains water, thereby giving full play to the highest efficiency of the two equipments, avoiding the problems of large power consumption and high cost consumption of traditional jet pumps, improving efficiency and saving costs to a certain extent, thereby accelerating the progress of the project and reducing the project cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the vacuum device of the present invention; Figure 2 This is a schematic diagram of the construction and installation structure of the plastic drainage board of the present invention; Figure 3 It is a schematic diagram of the vacuum pipeline arrangement structure of the present invention.

[0015] In the figure: 1. Water collection well tank; 2. Water ring vacuum pump; 3. Distribution box; 4. Hollow pipe; 5. Vacuum gauge; 6. Drainage pump; 7. Water inlet pipe; 8. Drainage pipe. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0017] See also Figure 1-3 As shown, a water vapor separation vacuum preloading construction method for a drainage board includes the following steps during construction: Step 1: Level the site and fill the plain soil cushion with a thickness of 80cm. Use a bulldozer to level and compact the site to ensure that the plastic drainage board machine can move normally for construction; Step 2: Fill the sand cushion layer. The total thickness of the drainage sand cushion layer is 60cm. The construction of the drainage sand cushion layer adopts mechanical and manual paving. During the construction process, it is necessary to avoid excessive disturbance of the soft soil surface to avoid mixing of sand, soil and mud. The drainage cushion layer uses medium-coarse sand or crushed stone with a permeability coefficient greater than 1×10-2cm / s; the crushed stone particle size is not more than 2cm, and the sand material uses well-graded, hard, clean medium-coarse sand with a mud content of no more than 3%; Step 3: Construction of plastic drainage board; Step 4: bury the plastic drainage board and install the vacuum pipeline; Step 5: Dig a sealing trench; Step 6: Lay the sealing cloth and film; Step 7: Install the vacuum device and connect the vacuum device to the vacuum pipeline; Step 8: Test vacuum and check seals; Step 9: Formal vacuuming and testing begins; Step 10: Vacuum preloading and unloading acceptance; Step 11: Continue pre-pressing after vacuum is released, and remove the sealing film outside the drainage cushion layer outside the slope foot; In step seven, the vacuum device consists of a water collecting well tank body 1, a water ring vacuum pump 2 and a distribution box 3. A vacuum gauge 5 is installed on the water collecting well tank body 1. A hollow pipe 4 is installed on the input end of the water ring vacuum pump 2. The water ring vacuum pump 2 is connected to the water collecting well tank body 1 through the hollow pipe 4. A drainage pump 6 is installed inside the water collecting well tank body 1. A water inlet pipe 7 and a drainage pipe 8 are respectively installed on the water collecting well tank body 1. The output end of the drainage pump 6 is connected to the drainage pipe 8. The vacuum pipeline is connected to the water collecting well tank body 1 through the water inlet pipe 7. After the construction is completed, the water ring vacuum pump 2 is used to evacuate the water collecting well tank body 1, so that a negative pressure is formed inside the water collecting well tank body 1. The negative pressure continues to be transmitted to the foundation through the sub-membrane pipeline and the plastic drainage board, so that the water and gas in the foundation are gathered into the water collecting well tank body 1 through the drainage board and the sub-membrane pipeline under the action of negative pressure. The water vapor gathered inside the water collecting well tank body 1 is separated inside the water collecting well tank body 1, and then is discharged through the water collecting well tank body 1. The water in the part is discharged through the drainage pump 6, and the gas is discharged through the water ring vacuum pump 2, and the drainage pump 6 can adjust the start and stop time according to the amount of water. The water ring vacuum pump 2 only draws air, and the drainage pump 6 drains water. Therefore, the highest efficiency of the two equipment can be brought into play, which solves the problem that the traditional jet pump needs to maintain a fixed power operation during the entire vacuum pumping period, consumes a lot of electricity, and has a high construction cost. It can save production costs to a certain extent and reduce the project cost. Taking a 10,000 square meter conventional reinforcement area of ​​the project as an example, the vacuum degree in the reinforcement area is stably maintained at more than 80kPa. Using traditional equipment, according to the specifications, a set of jet vacuum pumps handles an area of ​​no more than 1000 square meters. Therefore, 10 7.5kW jet pumps are required, with a total power of 75kW. Using water-gas separation technology, a vacuum pump station is required to be set up. The power of the pump station is 15KW, and the energy saving rate is more than 80%.

[0018] In step three, during the construction of plastic drainage boards, first measure and place the board positions. The measurement and placement of the board positions means using a total station to determine the installation area, using a steel ruler to arrange the installation point positions of each plastic drainage board, and marking them with bamboo sticks or white lime. Then put the machine in place, and then put the plastic drainage board on the end of the machine casing after putting on the boots. The machine is a board inserter, such as Figure 2As shown, after the plate inserter is in place, adjust the verticality of the guide frame, pass the end of the plastic drain board through the prefabricated boot head fixing frame, fold the belt about 10 cm long, and fix it. Generally, the prefabricated boot head is made of iron or concrete boot head and other materials. Put the boot head on the end of the hollow casing to fix the plastic drain board and prevent mud and sand from entering the casing during the sinking process. Then insert the casing into the soil, finally pull out the casing and cut off the drain board. 50 cm is reserved for the plastic drain board on the sand cushion layer. When sinking the conduit into the pile position, it is necessary to calibrate the verticality of the conduit, and then use the vibrating hammer to sink it into the designed depth. The casing is marked with the footage depth. Before construction, check the scale After a review and meeting the requirements, the pipe was inserted 50cm into the underlying layer of silt and then continued to be inserted into the soft soil foundation. When pulling out the conduit, the drainage board in the conduit was loosened to allow it to droop naturally in the conduit. The pipe was pulled out while vibrating. When the plastic drainage board was bonded and anchored to the foundation soil, the vibration was stopped and the pipe was pulled out to the ground. The casing was lifted vertically when it was pulled out to prevent the drainage board from being dragged out or damaged. When the drainage board was dragged out for more than 0.5m or was damaged, it was reinserted nearby and the equipment was moved to the next pile position. After the drainage pipe construction was completed, the silt brought out by the board inserter was cleaned up in time, and the holes formed around the board during driving were filled with sand from the sand cushion layer.

[0019] In step 4, first bury one end of the plastic drainage board in the sand cushion layer, then dig a trench on the sand cushion layer, and bury the vacuum pipe in the trench. The vacuum pipe is divided into a vacuum filter pipe main pipe and a branch pipe. The vacuum filter pipe main pipe adopts a φ90mm corrugated pipe that meets the requirements, and the branch pipe adopts a φ75mm corrugated pipe. The corrugated pipe is wrapped with a filter membrane. The vacuum filter pipe is a hose that allows water to penetrate into the pipe from the outside. The filter pipe mainly plays the role of reverse filtration and water passing. Generally, PVC pipes (perforated geotextile) or corrugated pipes are used, such as Figure 3 As shown, the main pipe of the vacuum filter tube is arranged in a ring along the outside of the treatment area, with the middle encrypted spacing less than 35m, the branch pipes are buried at a spacing of 6m, and the sub-membrane vacuum probe is arranged horizontally along the line with a spacing of 20m. The vacuum main pipe is connected to the water collection well tank 1 through the film outlet and the water suction hose, and the connection of the film outlet must be firm and the seal must be reliable.

[0020] In step five, the sealing trench is excavated. The sealing trench is arranged around the construction area. It mainly plays the role of peripheral sealing in the vacuum preloading construction. The sealing trench is constructed by mechanical excavation. The excavation depth is controlled at 1.2-1.5m and the bottom width is 1.2m.

[0021] In step six, when laying the sealing cloth and sealing film, first lay a layer of non-woven geotextile, i.e., sealing cloth, and then sew it with a portable sewing machine, leaving a certain length on both sides, and then lay the two layers of sealing film in layers to cover the entire vacuum pre-compression area. After the first layer of film is laid, carefully check and fill the holes in time, and then lay the second layer of sealing film, and finally lay another layer of non-woven geotextile and sew it with a portable sewing machine.

[0022] In step eight, try to vacuum and check the seals. Stabilize the vacuum degree at more than 80kPa for 5-7 days, then lay a layer of geotextile, and then load it. The first layer of uniform fine soil is 50cm thick. It is pushed from all sides or both ends to prevent the geomembrane from being damaged and affecting the vacuum degree. The upper load is rolled layer by layer and constructed according to the compaction requirements of the roadbed. Continuously vacuum during the loading process.

[0023] In step nine, formal vacuuming and testing begins. After 7-10 days of vacuuming, it enters the normal vacuum preloading stage. Monitoring should be carried out immediately after the vacuuming begins. After vacuuming, the vacuum degree under the membrane in the reinforcement area will continue to rise. When the vacuum degree under the membrane reaches and stabilizes at above 80kPa, it enters the normal vacuum preloading stage. During the vacuuming process, patrol inspections are carried out and problems are dealt with in a timely manner. If the vacuum degree under the membrane does not reach 80kPa as expected after the vacuuming begins, appropriate technical measures must be taken to deal with it.

[0024] Step 10. During the vacuum preloading unloading acceptance, the vacuum degree under the membrane in the vacuum preloading reinforcement area needs to be continuously stable at above 80kPa for 6 months. In combination with the soft foundation design table, some sections with high filling height and deep soft foundation are vacuumed for 6-8 months. At the same time, before stopping the vacuuming, the total thickness of the fill is required to reach the total thickness required by the design, the fill elevation is not lower than the equal load top elevation, and the monitored horizontal displacement rate is less than 2mm / day. The earthwork is unloaded after an interval of 2-3 months after stopping the vacuuming, and the settlement rate is required to be less than 3mm / month for three consecutive months before unloading.

[0025] When in use, the water ring vacuum pump 2 is started, so that negative pressure is formed inside the water collecting well tank body 1, and then the negative pressure is transmitted to the foundation through the sub-membrane pipeline and the plastic drainage board. Under the action of negative pressure, the water and gas in the foundation gather in the water collecting well tank body 1 through the drainage board and the sub-membrane pipeline, and the water vapor is separated inside the water collecting well tank body 1, and the gas is discharged through the water ring vacuum pump 2, and the water inside the water collecting well tank body 1 is discharged through the drainage pump 6. The drainage pump 6 adjusts the start and stop time according to the amount of water. In this vacuuming mode, the water ring vacuum pump 2 only draws air and the drainage pump 6 only drains water, thereby giving full play to the highest efficiency of the two equipments, avoiding the problem that the traditional jet pump needs to keep the jet pump running at a fixed power throughout the vacuuming period, which consumes a lot of electricity and has high cost consumption. To a certain extent, it improves efficiency and saves costs, thereby accelerating the progress of the project and reducing the project cost.

[0026] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0027] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A water vapor separation vacuum preloading construction method for a drainage board, characterized in that: During construction, the following steps are included: Step 1: Level the site and fill the plain soil cushion layer; Step 2: Filling the sand cushion layer; Step 3: Construction of plastic drainage board; Step 4: bury the plastic drainage board and install the vacuum pipeline; Step 5: Dig a sealing trench; Step 6: Lay the sealing cloth and film; Step 7: Install a vacuum device and connect the vacuum device to the vacuum pipeline; Step 8: Test vacuum and check seals; Step 9: Formal vacuuming and testing begins; Step 10: Vacuum preloading and unloading acceptance; Step 11: Continue pre-pressing after vacuum is released, and remove the sealing film outside the drainage cushion layer outside the slope foot; In step seven, the vacuum device is composed of a water collection well tank body (1), a water ring vacuum pump (2) and a distribution box (3); a vacuum gauge (5) is installed on the water collection well tank body (1); a hollow pipe (4) is installed on the input end of the water ring vacuum pump (2); the water ring vacuum pump (2) is connected to the water collection well tank body (1) through the hollow pipe (4); a drainage pump (6) is installed inside the water collection well tank body (1); a water inlet pipe (7) and a drainage pipe (8) are respectively installed on the water collection well tank body (1); the output end of the drainage pump (6) is connected to the drainage pipe (8); and the vacuum pipeline is connected to the water collection well tank body (1) through the water inlet pipe (7).

2. The water vapor separation vacuum preloading construction method for drainage board according to claim 1, characterized in that: In step three, during the construction of the plastic drain board, first measure and place the board position, then put the machine in place, then put the plastic drain board on the end of the machine casing, then insert the casing into the soil, finally pull out the casing and cut off the drain board, and then move the machine to the next pile position.

3. The water vapor separation vacuum preloading construction method for drainage board according to claim 1, characterized in that: In step four, first bury one end of the plastic drainage board in the sand cushion layer, then dig a trench on the sand cushion layer, and bury the vacuum pipe in the trench. The vacuum pipe is divided into a vacuum filter pipe main pipe and a branch pipe. The vacuum filter pipe main pipe is arranged in a ring along the outside of the treatment area, with a dense spacing of less than 35m in the middle, and the branch pipes are buried at a spacing of 6m.

4. The water vapor separation vacuum preloading construction method for drainage board according to claim 1, characterized in that: In step five, sealing trenches are excavated and arranged around the construction area.

5. The water vapor separation vacuum preloading construction method for drainage board according to claim 1, characterized in that: In step six, in laying the sealing cloth and sealing film, first lay a layer of non-woven geotextile, i.e., sealing cloth, and then sew it with a portable sewing machine, and reserve a certain length on both sides, then lay the two layers of sealing film in layers to cover the entire vacuum pre-pressing area, and finally lay another layer of non-woven geotextile and sew it with a portable sewing machine.

6. The water vapor separation vacuum preloading construction method for drainage board according to claim 1, characterized in that: In step eight, during the vacuum test and seal inspection, the vacuum degree is stabilized at above 80 kPa for 5-7 days, and then another layer of geotextile is laid before loading.

7. The water vapor separation vacuum preloading construction method for drainage board according to claim 1, characterized in that: In step nine, the formal vacuuming and testing begins. After 7-10 days of vacuuming, it enters the normal vacuum pre-pressing stage. Monitoring work must be carried out immediately after the vacuuming begins.

8. The water vapor separation vacuum preloading construction method for drainage board according to claim 1, characterized in that: Step 10. During the vacuum preloading unloading acceptance, the vacuum degree under the membrane in the vacuum preloading reinforcement area needs to be continuously stable at above 80kPa for 6 months. At the same time, the total thickness of the fill is required to reach the total thickness required by the design before stopping the vacuum pumping. The fill elevation is not lower than the equal load top elevation, and the monitored horizontal displacement rate is less than 2mm / day. The earthwork can be unloaded after an interval of 2-3 months after stopping the vacuum pumping, and the settlement rate is required to be less than 3mm / month for three consecutive months before unloading.

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