Combined soft soil foundation energy-saving treatment method

Abstract

This invention discloses a combined energy-saving treatment method for soft soil foundations, creatively integrating air lift and a circulating on-off pump into traditional vacuum preloading. Air lift periodically clears water from the core of the drainage board, ensuring the vacuum load is transmitted along the drainage board without attenuation. The circulating on-off pump causes periodic changes in vacuum level, alleviating clogging and significantly saving energy in the early stages of vacuum preloading. By rationally combining the air lift cycle and the on-off pump cycle, the consolidation pressure is increased and the energy-saving effect is maximized. This invention employs a combined air lift and circulating vacuum loading method for efficient and energy-saving consolidation treatment of soft soil, with broad application prospects and significant social benefits. As a novel energy-saving soft soil consolidation method, it is of great significance for promoting carbon neutrality.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, and in particular relates to a combined method for energy-saving treatment of soft soil foundations. Background Technology

[0002] Deep soft soil foundations are widely distributed in southeastern my country. Soft soil foundations are characterized by high water content (greater than 50%), extremely fine soil particles (average particle size less than 10 μm), and extremely low strength (vane strength around 10 kPa). Therefore, foundation treatment is essential before subsequent construction can proceed. For large-area soft soil foundation treatment, such as for airports, docks, and storage yards, the preferred method is vacuum preloading. This method involves inserting drainage boards into the foundation and connecting them to a pipeline system. Then, a sealing membrane is laid on the surface of the foundation treatment area, and pressure trenches are set up at the boundaries for sealing. Finally, vacuum pumps and drainage pumps are installed. The vacuum pumps extract air from the sealing system to create a vacuum negative pressure, causing the soil to drain and consolidate. The drainage pumps then discharge the water along the drainage boards and pipelines, thus achieving the preloading treatment of the soft soil foundation.

[0003] However, current vacuum preloading faces the problem of rapid vacuum degradation along the vertical direction of the drainage board (the degradation rate can reach 10 kPa / m), resulting in poor treatment effect on soft soil below a depth of 10 m. Meanwhile, current vacuum preloading specifications require a vacuum level ≥85 kPa under the inner membrane throughout the entire foundation treatment period (generally 90 days or more), thus necessitating continuous pump operation and leading to high energy consumption. Engineering practice shows that the electricity cost of the vacuum pump can account for more than 50% of the total cost of vacuum preloading.

[0004] In traditional vacuum preloading, because the vacuum pump operates at a constant power throughout the entire vacuuming process, reaching higher vacuum levels not only fails to effectively increase the vacuum degree but also results in significant energy loss. Furthermore, for dredged soil foundations, maintaining a high vacuum throughout (≥85kPa) can actually cause soil particles to be adsorbed onto the drainage board surface more quickly, forming dense, clogged soil columns that severely impact the drainage and consolidation effect of the dredged soil foundation.

[0005] Furthermore, in traditional vacuum preloading, the core of the drainage board is always filled with water. A full drainage board leads to a significant decrease in vacuum level along its depth, resulting in engineering problems such as a sharp drop in the water discharge rate and poor consolidation of deep soil.

[0006] Chinese patent application number 2023113548579 discloses a method for efficient preloading of soft soil foundations based on air lift combined with vacuum. This method applies the principle of air lift to vacuum preloading.

[0007] It is a new method of vacuum pre-compression, but during the vacuuming stage, the vacuum level inside the drain plate is stable at a high vacuum level, and the vacuum pump is continuously turned on, which cannot effectively improve the vacuum level and will cause a large power consumption. Summary of the Invention

[0008] To address the aforementioned technical problems in existing technologies, this invention provides a combined energy-saving treatment method for soft soil foundations. This method involves periodically introducing positive pressure gas into the bottom of the drainage board to drain the water stored in the core of the drainage board at regular intervals. Simultaneously, the vacuum level is cyclically changed by periodically turning a vacuum pump on and off.

[0009] The technical solution adopted in this invention is:

[0010] A combined method for energy-saving treatment of soft soil foundations, characterized by the following steps:

[0011] Step 1: Modify the drainage board;

[0012] Step 2: One end of the pressurized gas pipeline is connected to the air compressor, and the other end is connected to the bottom of the drainage board. The pipeline is driven into the soft soil foundation together with the drainage board. The end of the pressurized gas pipeline is connected to the ground under the sealing membrane to form an air-lift positive pressure pipeline. The air flow direction is from the air compressor to the drainage board.

[0013] Step 3: Connect one end of the vacuum pipe to the vacuum pump and the other end to the top of the drainage board. Connect the ends of the vacuum pipe to the ground under the sealing membrane to form a vacuum negative pressure pipeline.

[0014] Step 4: Lay a sealing membrane on the soil surface and set up a membrane pressure trench at the boundary of the treated soil, that is, excavate a trench around the reinforcement area to bury the sealing membrane; insert the PU tube probe of the electric contact vacuum gauge into the vacuum distributed filter tube and seal it to measure the real-time vacuum degree at the head of the drainage board, and bury the PU tube probe of the water level sensor into the head of a representative drainage board to monitor the water level of the drainage board;

[0015] Step 5: Set the upper and lower thresholds of the electric contact vacuum gauge so that the pump automatically stops when the vacuum level is higher than the upper threshold and automatically starts when the vacuum level is lower than the lower threshold.

[0016] Step 6: Turn on the vacuum pump and air compressor for trial operation, and debug the air compression system, vacuum equipment and monitoring system; turn on the vacuum pump and obtain the peak vacuum level, that is, the vacuum level when the electric contact vacuum gauge remains stable for one hour; and measure the actual data of the increase or decrease of the vacuum level under the sealing diaphragm over time, and set the vacuum pump on / off cycle based on this: when the vacuum level in the drain plate reaches the lower threshold, turn on the vacuum pump; when the vacuum level in the drain plate reaches the upper threshold, turn off the vacuum pump.

[0017] Step 7: Turn on the vacuum pump and run it continuously until the vacuum degree inside the drainage board reaches the upper threshold. After the vacuum pump stops running, turn it off. The soil is drained and consolidated under the action of vacuum negative pressure energy inside the device. When the vacuum degree inside the drainage board reaches the lower threshold, turn on the vacuum pump.

[0018] Repeat step 7 until the water level sensor detects that the drainage plate is full of water, then proceed to the next step.

[0019] Step 8: Turn on the air compressor and drain pump to perform air lift and water pumping, so that the water is quickly lifted upward and discharged under the positive pressure at the bottom. Then, judge whether the water in the drain plate has been completely discharged based on the drainage of the drain pump. Then stop the air lift. Then turn on the vacuum pump to replenish the vacuum and enter the next cycle. That is, repeat steps 7 and 8 to achieve air lift combined cycle vacuum loading.

[0020] Step 9: Inspection of construction results;

[0021] The acceptance criteria are that the measured settlement reaches more than 80% of the calculated settlement value or the measured soil settlement rate is less than or equal to 0.5 mm / d for five consecutive days.

[0022] Furthermore, in step 1, the specific method for modifying the drainage board is as follows: a hand-shaped connector is connected to both the top and bottom of the drainage board, the other end of the pressure gas pipe is connected to the hand-shaped connector at the bottom of the drainage board, and the other end of the vacuum pipe is connected to the hand-shaped connector at the top of the drainage board.

[0023] Furthermore, in step 2, a check valve is installed at the positive pressure pipeline.

[0024] Furthermore, in step 5, the upper threshold is set to the peak value, which is the maximum vacuum that the vacuum pump can provide, which is affected by the local temperature; the lower threshold is set to 1 / 5 to 3 / 5 of the peak value, depending on the properties of the soil being treated.

[0025] Furthermore, in step 8, the upper threshold is the peak vacuum level reached by the vacuum pump under different operating conditions; the lower threshold is the 4 / 5 peak value.

[0026] Furthermore, the cyclic vacuum loading of the vacuum pump is controlled by setting the upper and lower thresholds of the vacuum gauge with electrical contacts.

[0027] Furthermore, the width of the pressure groove is set to 0.8m.

[0028] Furthermore, in step 8, the air compressor specifications are selected as follows: the capacity and quantity of the drain plates are calculated, and the exhaust flow rate and exhaust pressure required to drain the water in the drain plates within a specified time are used to select the compressor.

[0029] Furthermore, in step 8, the method for selecting the specifications of the drainage pump is as follows: the pump is selected by calculating the amount of water required to drain the water in the drainage board within a specified time.

[0030] Furthermore, in step 9, the actual settlement is measured using a level or total station leveling method.

[0031] The working principle of this invention is as follows:

[0032] During the cyclic vacuum phase, the vacuum pump and drain pump automatically start, and the residual gas in the drain pipe and drain plate is quickly drawn away by the vacuum pump, thereby increasing the vacuum level to a high value P. max Subsequently, the vacuum pump and drainage pump automatically shut down, maintaining a vacuum within the sealed system consisting of the drainage board, drainage pipes, and sealing membrane. Under vacuum pressure, pore water in the soil surrounding the drainage board seeps and accumulates towards the board core (a process similar to water collection in a well and the rise in the water level). After a certain period, the vacuum level within the sealed system decreases to a low value P. min At this point, the vacuum pump and drain pump restart, simultaneously draining the water and raising the vacuum level in the sealed system back to a high value P. max By repeatedly switching the vacuum pump on and off, the vacuum level is maintained at a high value P. max and low value P min The process cycles continuously until the sensor detects that the core of the drainage board is full of water. At this point, the air compressor is activated to perform air lifting for bottom ventilation. The air compressor introduces air at a certain pressure and flow rate into the bottom of the drainage board. The pressurized air and the water in the core of the drainage board form a two-phase flow of air and water, which quickly drains the water from the core of the drainage board, thus starting the next cycle.

[0033] The effectiveness of air lift combined with vacuum preloading depends on the level and distribution of vacuum pressure. At lower vacuum levels, the vacuum under the membrane increases significantly with the number of vacuum pumps (increasing the pumping capacity). However, at higher vacuum levels, the gas under the membrane is already quite rarefied, and increasing the number of vacuum pumps has little effect on changing the vacuum level. The vacuum distribution depends on the location and size of the drainage board and the soil properties. This invention creatively integrates air lift and circulating vacuum technology into the traditional vacuum preloading method. Air lift periodically empties the water from the drainage board core, ensuring that the vacuum load is transmitted vertically along the drainage board without attenuation. The circulating pump switching allows for periodic changes in vacuum level, alleviating clogging and significantly saving energy in the early stages of vacuum preloading. By rationally combining the air lift cycle and the pump switching cycle, the consolidation pressure increase and energy-saving effect are maximized.

[0034] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0035] 1. This invention creatively integrates gas lift and cyclic switching vacuum pump into the traditional vacuum pre-compression treatment method. By rationally combining the gas lift cycle and the switching pump cycle, it maximizes the vacuum consolidation pressure increase and energy saving effect, which has significant originality.

[0036] 2. Compared with the traditional vacuum preloading foundation treatment method that only vacuums the top of the slab, the present invention can effectively increase the vacuum consolidation pressure throughout the entire depth range of the drainage slab and achieve significant energy saving.

[0037] 3. This invention only requires the addition of an air compressor (and the connected ventilation pipeline) and a smart switch for the vacuum pump to realize air lift and circulation switching of the vacuum pump respectively. Moreover, the related hardware costs are low and the operation is simple. It is a brand-new foundation treatment method that combines engineering benefits and economic benefits.

[0038] 4. The air lift of this invention can periodically empty the water stored in the core of the drainage board, thereby ensuring that the vacuum load is transmitted vertically along the drainage board without attenuation. The cyclic switching pump makes the vacuum degree change periodically, thereby alleviating clogging and significantly saving energy in the early stage of vacuum pre-compression. By reasonably combining the air lift cycle and the switching pump cycle, the consolidation pressure can be increased and the energy-saving effect can be maximized. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the present invention.

[0040] Figure 2 This is a flowchart illustrating an embodiment of the present invention.

[0041] Figure 3 This is a detailed schematic diagram of the present invention.

[0042] Figure 4 This is a schematic diagram of the drainage plate and hand-shaped structure in the testing device of the present invention.

[0043] Figure 5 This is a schematic diagram of the flow pattern changes within the drainage board during the implementation of this invention.

[0044] Explanation of reference numerals in the attached drawings: 1. Vacuum pump; 2. Air compressor; 3. Geotextile and geomembrane; 4. Pressurized gas pipeline; 5. Vacuum pipeline; 6. Drainage board; 7. Joint; 8. Drainage board filter membrane; 9. Distribution box; 10. Monitoring equipment; 11. Vacuum storage tank; 12. Air filling pump; 13. Flow meter; 14. Submersible pump; 15. Vacuum generating system; 16. Pressure system. Detailed Implementation

[0045] The technical solution of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0046] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] refer to Figures 1 to 5 The present invention provides a combined energy-saving treatment method for soft soil foundations, which specifically includes the following steps:

[0049] Step 1: Modify the drainage board 6 and connect it to the connector 7. Connect the modified and assembled drainage board to the vacuum pipe 5 and the pressurized gas pipe 4.

[0050] Step 2: One end of the pressurized gas pipeline 4 is connected to the air compressor 2, and the other end is connected to the bottom of the drainage board. The pipeline is driven into the soft soil foundation together with the drainage board. The end of the pressurized gas pipeline is connected to the ground under the sealing membrane to form an air-lift positive pressure pipeline. The air flow direction is from the air compressor to the drainage board.

[0051] Step 3: One end of the vacuum pipe 5 is connected to the vacuum pump 1, and the other end is connected to the top of the drainage board. The end of the vacuum pipe is connected to the ground under the geotextile and geomembrane 3 to form a vacuum negative pressure pipeline.

[0052] Step 4: Lay geotextile and geomembrane 3 on the soil surface, and set up a pressure trench at the boundary of the treated soil, that is, excavate a trench around the reinforcement area to bury geotextile and geomembrane 3; insert the PU tube probe of the electric contact vacuum gauge into the vacuum distributed filter tube and seal it to measure the real-time vacuum degree at the head of the drainage board, and bury the PU tube probe of the water level sensor into the head of a representative drainage board to monitor the water level of the drainage board;

[0053] Specifically, the cyclic vacuum loading of the vacuum pump is controlled by setting the upper and lower threshold values ​​of the vacuum gauge with electrical contacts.

[0054] Step 5: Set the upper and lower thresholds of the electric contact vacuum gauge so that the pump automatically stops when the vacuum level is higher than the upper threshold and automatically starts when the vacuum level is lower than the lower threshold.

[0055] Step 6: Turn on the vacuum pump and air compressor for trial operation, and debug the air compression system, vacuum equipment and monitoring system; turn on the vacuum pump, monitor the vacuum degree of vacuum tank 11 through the monitoring equipment. Vacuum tank 11 can also drain water backflow in the drainage plate and stabilize the vacuum degree to obtain the peak vacuum degree, that is, the vacuum degree when the electric contact vacuum gauge remains stable for one hour; and measure the actual data of the vacuum degree under the sealing membrane as it increases or decreases over time. Based on this, set the vacuum pump switching cycle: when the vacuum degree in the drainage plate reaches the lower threshold, turn on the vacuum pump by turning on the relevant circuit switch of the distribution box 9; when the vacuum degree in the drainage plate reaches the upper threshold, turn off the vacuum pump by turning off the relevant circuit switch of the distribution box.

[0056] Specifically, connect the pressurized gas pipeline and vacuum pipeline to the air compressor and vacuum pump respectively; turn on the vacuum pump and air compressor, and test run them to debug the air compression system, vacuum equipment, and monitoring system, checking that all connections are secure and correct. Pay particular attention to the inlet and outlet pipelines and cables, ensuring there are no loose connections or leaks, and ensuring the equipment's operating parameters are within normal ranges. Observe the equipment's operating status, including speed, noise, and vibration. If any abnormalities occur, stop operation immediately, check, and troubleshoot the problem. Turn on the vacuum pump to obtain the peak vacuum level (the vacuum level when the electrical contact vacuum gauge remains stable for one hour), and measure the actual data of the vacuum level under the membrane increasing or decreasing over time. Based on this, set the vacuum pump on / off cycle (when the vacuum level inside the drain plate reaches the lower threshold, i.e., when the vacuum level reaches its trough, turn on the vacuum pump (i.e., start the vacuum generation system); when the vacuum level inside the drain plate reaches the upper threshold, turn off the vacuum pump).

[0057] Figure 3 The vacuum generating system 15 includes a vacuum pump 1, a power distribution box 9, a monitoring device 10, and a vacuum storage tank 11; the pressure system 16 includes an air compressor 2 and an air filling pump. Figure 1 The diagram shown is a schematic diagram of all the devices and structures of this invention; Figure 3The diagram shows all the equipment in actual use.

[0058] Step 7: Start the vacuum generation system: Turn on the vacuum pump and run it continuously until the vacuum degree inside the drainage board reaches the upper threshold. After the vacuum pump stops running, turn it off. Under the action of the circulating vacuum pressure, the water in the soil quickly passes through the drainage board filter membrane 8 and enters the drainage board 6, and the soil is drained and consolidated. When the vacuum degree inside the drainage board reaches the lower threshold, turn on the vacuum pump.

[0059] Repeat step 7 until the water level sensor detects that the drainage plate is full of water, then proceed to the next step.

[0060] Step 8: Activate the pressure system: Activate the air pump 12, air compressor 2, and submersible pump 14 to perform air injection and water pumping, so that the water in the drainage plate 6 is quickly lifted upwards and discharged under the positive pressure at the bottom. (The water inside the drainage plate is then discharged.) Figure 5 As shown, as water is continuously discharged, the air content inside the plate increases, and the flow pattern of water inside the drainage plate changes from mainly slug flow to mainly annular flow. Then, based on the flow rate monitored by flowmeter 13, it is determined whether the water in the drainage plate has been completely discharged, and then the air lift is stopped; the vacuum pump is then turned on to replenish the vacuum, and the next cycle begins, i.e., steps 7 and 8 are repeated, thus achieving air lift combined cycle vacuum loading.

[0061] The method for selecting the specifications of an air compressor is as follows: Calculate the capacity and quantity of the drain plates, and select the compressor by calculating the exhaust flow rate and exhaust pressure required to drain the water from the drain plates within a specified time. The method for selecting the specifications of a drain pump is as follows: Calculate the drainage volume required to drain the water from the drain plates within a specified time.

[0062] Step 9: Inspection of construction results;

[0063] The acceptance criteria are that the measured settlement reaches more than 80% of the calculated settlement value or the measured soil settlement rate is less than or equal to 0.5 mm / d for five consecutive days. Once the expected standard is met, all equipment will be shut down.

[0064] Specifically, the actual settlement is measured using a level or total station leveling method.

[0065] In one embodiment, in step 1, the specific method for modifying the drainage board is as follows: a hand-type connector 7 is connected to both the top and bottom of the drainage board, the other end of the pressure gas pipe is connected to the hand-type connector at the bottom of the drainage board, and the other end of the vacuum pipe is connected to the hand-type connector at the top of the drainage board.

[0066] In one embodiment, a check valve is provided at the positive pressure pipeline.

[0067] In one embodiment, the upper threshold is set to the peak value, which is the maximum vacuum that the vacuum pump can provide, which is affected by the local temperature; the lower threshold is set to 1 / 5 to 3 / 5 of the peak value, depending on the properties of the soil being treated.

[0068] Specifically, the maximum vacuum level that a vacuum pump can provide is affected by the local temperature, and is generally around 85 kPa.

[0069] Specifically, the upper threshold is the peak vacuum level achieved by the vacuum pump under different operating conditions; the lower threshold is the 4 / 5 peak value.

[0070] In one embodiment, the width of the pressure groove is set to 0.8m.

[0071] In this invention, the vacuum pump is first turned on, and the peak value of the vacuum degree is obtained. The trough value (1 / 5 to 3 / 5 of the peak value) is taken as the trough value (depending on the properties of the soil being treated). The measured data of the vacuum degree under the membrane increasing or decreasing over time are also obtained. A single cycle is set to 1 hour, with the vacuum pump running time set to 15 minutes and the settling time set to 45 minutes. The vacuum pump runs continuously for 15 minutes, allowing the soil to continue draining and consolidating under the residual vacuum negative pressure energy within the device. After the vacuum pump stops running, the soil is left to stand for 45 minutes. This operation is repeated until the sensor detects sufficient water in the drainage board. At this point, the air compressor (i.e., the pressure system) is turned on to perform air lifting, allowing this water to be quickly lifted upwards and discharged under the positive pressure at the bottom. Air is continuously ventilated for 5 minutes to ensure that as much water as possible is drained from the drainage board. After completing the above steps, the vacuum pump is turned on again to replenish the vacuum degree for the next cycle. Repeating the above operations achieves air lifting combined with cyclic vacuum loading.

[0072] The acceptance standard is to ensure that the measured settlement reaches more than 80% of the calculated settlement value, or that the measured soil settlement rate is less than or equal to 0.5 mm / d for five consecutive days. After achieving the expected results, all equipment should be shut down.

[0073] Working principle of the invention:

[0074] During the cyclic vacuum phase, the vacuum pump and drain pump automatically start, and the residual gas in the drain pipe and drain plate is quickly drawn away by the vacuum pump, thereby increasing the vacuum level to a high value P. max Subsequently, the vacuum pump and drainage pump automatically shut down, maintaining a vacuum within the sealed system consisting of the drainage board, drainage pipes, and sealing membrane. Under vacuum pressure, pore water in the soil surrounding the drainage board seeps and accumulates towards the board core (a process similar to water collection in a well and the rise in the water level). After a certain period, the vacuum level within the sealed system decreases to a low value P. min At this point, the vacuum pump and drain pump restart, simultaneously draining the water and raising the vacuum level in the sealed system back to a high value P. max By repeatedly switching the vacuum pump on and off, the vacuum level is maintained at a high value P.max and low value P min The process cycles continuously until the sensor detects that the core of the drainage board is full of water. At this point, the air compressor is activated to perform air lifting for bottom ventilation. The air compressor introduces air at a certain pressure and flow rate into the bottom of the drainage board. The pressurized air and the water in the core of the drainage board form a two-phase flow of air and water, which quickly drains the water from the core of the drainage board, thus starting the next cycle.

[0075] During the several minutes of air-lift operation, the water in the core of the drainage board is emptied in the form of a two-phase air-water flow. The air-lift then ends, leaving the core water-free. Any remaining air in the board is quickly removed by the vacuum pump connected to the top, achieving seamless vacuum transfer from the top to the bottom of the drainage board and significantly increasing the vacuum consolidation pressure of the foundation soil. During the cyclic switching of the vacuum pump, the vacuum level under the membrane and inside the drainage board cyclically changes between high and low values, thus reducing the average vacuum level. This helps alleviate the drainage clogging effect in soft soil during the early stages of vacuum preloading. Simultaneously, the vacuum pump consumes no electricity during the pump shutdown period, resulting in significant energy savings.

[0076] The vacuum pump and drainage pump consume no electricity during pump shutdown, making it more energy-efficient than conventional vacuum preloading processes using continuously operating pumps. Furthermore, after the water in the core of the drainage board is emptied by air lift, any remaining gas inside the board can be quickly extracted by the vacuum pump, ensuring a negative pressure value (e.g., -85 kPa) at the board head throughout the entire board depth. This creates a significantly enhanced seepage pressure difference between the board and the soil compared to conventional vacuum preloading, driving pore water in the soft soil to flow rapidly into the drainage board, achieving efficient consolidation. In addition, the positive pressure gas at the bottom of the board can also escape through the filter membrane of the drainage board into the surrounding soft soil, causing cracks and creating new drainage channels, further shortening the seepage path and increasing the seepage consolidation rate.

[0077] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this invention should not be considered as limited to the specific forms stated in the embodiments. The scope of protection of this invention also includes equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A combined soft ground foundation energy-saving treatment method, characterized by, The specific method includes the following steps: Step 1: Modify the drainage board; Step 2: After connecting the pressurized gas pipeline to the drainage board, drive them together into the soft soil foundation; Step 3: Connect the vacuum pipe to the top of the drainage board; Step 4: Lay a sealing membrane on the soil surface and set up a membrane trench at the boundary of the treated soil; insert the PU tube probe of the electric contact vacuum gauge into the vacuum distributed filter tube and seal it; and bury the PU tube probe of the water level sensor into the head of the representative drainage board. Step 5: Set the upper and lower thresholds of the electrical contact vacuum gauge; the upper threshold is set to the peak value, which is the maximum vacuum that the vacuum pump can provide, which is affected by the local temperature; the lower threshold is set to 1 / 5 to 3 / 5 of the peak value, depending on the properties of the soil being treated. Step 6: Turn on the vacuum pump and air compressor to conduct a trial run and debug the air compression system, vacuum equipment and monitoring system; when the vacuum level in the drain plate reaches the lower threshold, turn on the vacuum pump; when the vacuum level in the drain plate reaches the upper threshold, turn off the vacuum pump. Step 7: Turn on the vacuum pump and run it continuously until the vacuum degree inside the drainage board reaches the upper threshold. After the vacuum pump stops running, turn it off. The soil is drained and consolidated under the action of vacuum negative pressure energy inside the device. When the vacuum degree inside the drainage board reaches the lower threshold, turn on the vacuum pump. Repeat step 7 until the water level sensor detects that the drainage plate is full of water, then proceed to the next step. Step 8: Turn on the air compressor and drain pump to perform air injection, air lift and water pumping. Repeat steps 7 and 8 to achieve air lift combined cycle vacuum loading. The upper threshold is the peak vacuum level reached by the vacuum pump under different operating conditions. The lower threshold is the 4 / 5 peak value. Step 9: Construction effect inspection. Use a level or total station to perform leveling measurement to measure the actual settlement. The acceptance standard is that the measured settlement reaches more than 80% of the calculated settlement value or the measured soil settlement rate is less than or equal to 0.5 mm / d for five consecutive days.

2. The combined soft soil foundation energy-saving treatment method according to claim 1, characterized in that, In step 1, the specific method for modifying the drainage board is as follows: a hand-shaped connector is connected to both the top and bottom of the drainage board, the other end of the pressure gas pipe is connected to the hand-shaped connector at the bottom of the drainage board, and the other end of the vacuum pipe is connected to the hand-shaped connector at the top of the drainage board.

3. The combined soft soil foundation energy-saving treatment method according to claim 1, characterized in that, In step 2, one end of the pressurized gas pipeline is connected to an air compressor, and the other end is connected to the bottom of a drainage board. The pipeline is driven into the soft soil foundation together with the drainage board. The end of the pressurized gas pipeline is connected to the ground under the sealing membrane to form an air-lifted positive pressure pipeline. The air flow direction is from the air compressor to the drainage board. A one-way valve is installed at the air-lifted positive pressure pipeline. In step 3, one end of the vacuum pipe is connected to the vacuum pump, and the other end is connected to the top of the drainage board. The end of the vacuum pipe is connected to the ground under the sealing membrane to form a vacuum negative pressure pipeline.

4. The combined soft soil foundation energy-saving treatment method according to claim 1, characterized in that, The cyclic vacuum loading of the vacuum pump is controlled by setting the upper and lower thresholds of the vacuum gauge with electrical contacts.

5. The combined soft soil foundation energy-saving treatment method according to claim 1, characterized in that, The width of the pressure groove is set to 0.8m.

6. The combined soft soil foundation energy-saving treatment method according to claim 1, characterized in that, In step 8, the air compressor specifications are selected as follows: the capacity and quantity of the drain plates are calculated, and the exhaust flow rate and exhaust pressure required to drain the water in the drain plates within a specified time are used to select the compressor.

7. The combined soft soil foundation energy-saving treatment method according to claim 1, characterized in that, In step 8, the specifications of the drainage pump are selected as follows: the pump is selected by calculating the amount of water required to drain the water in the drainage board within a specified time.

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