Multi-channel air wall permeation-resistant foundation pit dewatering device and construction method thereof

Abstract

The application discloses a kind of multi-channel air wall permeation-resistant foundation pit dewatering device and its construction method, including being laid in the soil body of foundation pit around multiple inflatable holes, the depth of each inflatable hole is greater than water level before inflation, and along the tendency of water level before inflation, inflatable hole is inflated one by one, after inflation, multiple air walls are formed, the depth of each air wall is greater than the depth of water level before inflation;When inflatable hole is inflated, the bottom of inflation pipe is deep into inflatable hole, until the bottom of inflation pipe reaches water level and stops, the top of inflation pipe is stretched outside inflatable hole, and is connected with compressor.The application has the characteristics of rapid reduction with saturation according to the permeability of soil body, by inflation equipment in the soil body around foundation pit, the saturation of soil body is reduced, and the inflation wall is formed to reduce water level;Equipment is simple, green and economic, efficient, a new technology different from traditional dewatering technology is proposed, which has strict theoretical support and broad application prospect.

Description

Technical Field

[0001] This invention relates to a foundation pit dewatering device and its construction method, and more particularly to a foundation pit dewatering device with multiple air walls for seepage prevention and its construction method. Background Technology

[0002] During foundation pit excavation, the groundwater level is often higher than the bottom of the pit. Therefore, groundwater continuously seeps into the pit. To ensure construction is carried out under dry conditions and to prevent slope instability, quicksand, pit bottom heave, piping, and decreased foundation bearing capacity, dewatering is necessary. Currently, the main dewatering methods for foundation pits include: open drainage, lightweight wellpoints, jet wellpoints, electro-osmotic wellpoints, and tubular well dewatering. Each of these methods has its own applicable scope and limitations.

[0003] Prior to this invention, application documents such as CN118933046A disclosed a method for dewatering foundation pits. This method involves pouring a waterproof layer around the perimeter of the foundation pit and securing it with anchors. A collection trough is then created at the bottom of the pit, and the accumulated silt and mud are transported upwards to a collection box installed on the ground. This significantly improves the efficiency and quality of silt and mud removal. However, existing inventions generally cannot avoid the necessary engineering steps of using water pumps to remove accumulated water and silt, increasing engineering costs. To a certain extent, the efficiency is not high. Furthermore, pumping away large amounts of water may cause ground subsidence, leading to greater damage. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to propose a multi-layered air-wall seepage-blocking dewatering device for foundation pits and its construction method, which lowers the water level by forming an air-filled wall.

[0005] Technical solution: The present invention includes multiple air holes arranged in the soil around the foundation pit. The depth of each air hole is greater than the water level before air filling. The air holes are filled one by one along the downward trend of the water level before air filling. After air filling, multiple air walls are formed, and the depth of each air wall is greater than the depth of the water level before air filling.

[0006] When inflating the air hole, the bottom of the air tube is inserted into the air hole, and the top of the air tube extends out of the outside of the air hole and is connected to the compressor to inflate the air hole.

[0007] When the air inlet is inflated, it stops when the bottom of the air inlet tube reaches the water level line. After inflation is completed, evenly distributed bubbles are formed in the air inlet.

[0008] A resistivity sensor is installed on the inner wall of the air tube near the bottom, which can monitor the change in soil resistivity in real time. The change in soil saturation can be calculated based on the resistivity, and it can be used to determine whether the air inflation has reduced the soil saturation to the target saturation.

[0009] The bottom of the air-filled pipe is equipped with a filter screen to prevent fine soil particles from entering the air-filled pipe, clogging it, reducing the air-filling efficiency, and affecting the water-reducing effect of the air-filled wall.

[0010] The inflation tube is made of stainless steel and coated with lubricant on the outside to achieve a lubricating and sealing effect, making it easy to pull up during construction and remove after construction, and also ensuring that air bubbles do not easily overflow from the wall of the inflation tube.

[0011] The diameter of the air inlet is between 0.25m and 0.5m, and the interval is between 0.5m and 1m.

[0012] The width of the air wall is between 0.5m and 1.5m.

[0013] A construction method for a multi-layered air-wall seepage-prevention dewatering device for foundation pits includes the following steps:

[0014] Multiple air holes are set up around the foundation pit, with the depth of each air hole exceeding the water level line before air inflation at its location. An air inflation pipe is then laid and placed to the designated depth, followed by backfilling the soil to the ground surface.

[0015] Set the inflation pressure and start inflation. Monitor the soil saturation changes in real time during the inflation process using a resistivity sensor at the bottom of the inflation tube. Once the saturation reaches the target saturation, pull up the inflation tube and continue inflation. Repeat this process until the bottom of the inflation tube reaches the water level line and stop inflation.

[0016] After the first air wall is formed, the foundation pit is excavated, but it must not be below the water level line after the first air wall is formed. Then the support structure is installed. Repeat the above steps to form multiple air walls until the foundation pit excavation is completed.

[0017] After the excavation work was completed, the air pipes were retrieved and the soil samples were backfilled.

[0018] The water level line formed after the air tube is inflated is the inflated water level line. Compared with the water level line before inflation, the water level height of the two is the same before the first air wall. After passing through the first air wall, the water level line decreases. The inflated water level line after passing through the first air wall is parallel to the water level line before inflation. The remaining water level lines also follow the same pattern.

[0019] Beneficial effects: The present invention has the following advantages:

[0020] (1) Based on the characteristic that the permeability of soil decreases rapidly with saturation, the present invention uses an air-filling device to inflate the soil around the foundation pit, thereby reducing the saturation of the soil and forming an air-filled wall to lower the water level.

[0021] (2) The equipment is simple, green, economical, and efficient. It proposes a completely new technology that differs from traditional dewatering techniques, with rigorous theoretical support and broad application prospects. Utilizing the air-filled equipment and the multiple air walls formed by air can effectively achieve seepage prevention, lower the groundwater level, and ensure the safety of the foundation pit;

[0022] (3) There is no need to pump the groundwater to the surface. It only changes the permeability coefficient of the air wall and eventually lowers the water level to below the bottom of the excavated pit, so there will be no ground settlement problem.

[0023] (4) There is no need to use a water pump to clean up the water and silt at the bottom of the foundation pit, which effectively reduces project costs, saves time, and saves manpower and resources;

[0024] (5) It has a wide range of applications and can be used for soils with a particle size of 5 micrometers or larger, that is, it is applicable to soils with permeability coefficients of various orders of magnitude. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the inflation tube of the present invention;

[0027] Figure 3 This is a three-dimensional schematic diagram of the multi-layered air wall of the present invention. Detailed Implementation

[0028] The invention will now be further described with reference to the accompanying drawings.

[0029] Example 1

[0030] like Figures 1-3 As shown, the multi-air-wall seepage-blocking foundation pit dewatering device of the present invention includes multiple air-filled holes arranged in the soil surrounding the foundation pit. The diameter of the air-filled holes is between 0.25m and 0.5m, and the spacing is between 0.5m and 1m, which can be set according to the actual project. The depth of each air-filled hole is greater than the water level 1 before inflation, and the air-filled holes are inflated one by one along the downward trend of the water level 1 before inflation. After inflation, multiple air walls are formed, and the depth of each air wall is greater than the depth of the water level before inflation, so as to meet the basic requirements for lowering the water level. When inflating the air-filled holes, the bottom of the inflation pipe 9 is inserted into the bottom of the current inflation hole, and the top of the inflation pipe 9 extends out of the outside of the inflation hole and is connected to the compressor 3. During the inflation process, a cycle of inflation-pulling out the inflation pipe-inflation is required until the bottom of the inflation pipe 9 reaches the water level line to stop, ensuring that the air bubbles are evenly distributed.

[0031] like Figure 2 As shown, a filter screen 10 is installed at the bottom of the air tube 9 to prevent fine soil particles from entering the air tube, clogging it, reducing inflation efficiency, and affecting the water-reducing effect of the inflatable wall. A resistivity sensor 11 is installed on the inner wall near the bottom of the air tube 9 to monitor changes in soil resistivity in real time. The change in soil saturation can be calculated based on the resistivity, thus determining whether inflation has reduced the soil saturation to the target level. The air tube 9 is made of steel, and the outer surface is coated with Vaseline for lubrication and sealing, facilitating easy removal during construction and ensuring that air bubbles do not easily escape from the tube wall.

[0032] This invention features 3-5 air walls, each with a width between 0.5m and 1.5m. This embodiment uses 4 air walls as an example, including a first air wall 4, a second air wall 5, a third air wall 6, and a fourth air wall 7. Each air wall has a different depth, but all depths are greater than the depth of the water level line 1 before inflation. The specific depth is determined based on the actual project requirements, ultimately lowering the water level below the bottom of the foundation pit to meet engineering requirements. During inflation, the inflation tube 9 is first inserted into the corresponding inflation hole of the first air wall 4. The resistivity sensor 11 at the bottom of the inflation tube 9 monitors the change in soil saturation within the affected area in real time during inflation. Once the saturation reaches the target level, the inflation tube 9 is pulled up a certain height, and inflation continues. This process is repeated until the bottom of the inflation tube 9 reaches the water level line, at which point inflation stops. After inflation, evenly distributed air bubbles 12 are formed in the inflation holes, thus forming the first air wall 4. After the first air wall 4 is formed, the foundation pit can be excavated to a certain depth, but not below the water level that the first air wall 4 can lower. Then, the support structure 8 is installed. During the excavation process, the second air wall 5 can be formed simultaneously by inflation, following the same steps as the first air wall 4. After the second air wall 5 is formed, excavation and support continue, repeating this cycle until the entire foundation pit excavation is completed. The water level line formed after inflation is called the inflated water level line 2. Compared to the water level line 1 before inflation, the water level before the first air wall 4 is the same. After passing the first air wall 4, the water level drops significantly. The inflated water level line 2 after passing the first air wall 4 is parallel to the water level line 1 before inflation. The remaining water level lines follow the same pattern. After the entire excavation is completed, the inflation pipe is retrieved, and soil samples are backfilled.

[0033] This invention is based on the principle that the permeability coefficient of soil decreases rapidly with decreasing saturation. It utilizes an air-inflating device to inflate the soil around the excavation pit at a specific depth below the groundwater level, forming multiple unsaturated water-resistant zones, or multiple air walls. These air walls significantly reduce the water level passing through each air wall, effectively lowering the water level below the depth of the excavation pit. This invention features simple equipment, good economy, ease of construction, wide applicability, and broad application prospects.

[0034] Example 2

[0035] A construction method for a multi-layered air-wall seepage-blocking dewatering device for foundation pits utilizes the characteristic that soil permeability decreases rapidly with saturation. By inflating the soil around the foundation pit using an air-filling device, the soil saturation is reduced, forming an air-filled wall that lowers the water level. This method eliminates the need for cleaning accumulated water and silt, and does not pump water below the groundwater level to the surface, thus preventing ground subsidence. The specific principle is as follows:

[0036] Where Θ is the normalized volumetric water content, ranging from 0 to 1, and k r It is the relative permeability coefficient, k s This is the saturated permeability coefficient, and the value of η depends on the properties of the soil, generally ranging from 3 to 4. When the soil is inflated using an aeration device, the volumetric water content θ decreases, and Θ also decreases accordingly, thus reducing the soil's saturation. If we assume the residual saturation of the soil is θ... r If Θ is 0, then the normalized volumetric water content is equivalent to saturation. As soil saturation decreases, the soil permeability coefficient k also decreases significantly. This decrease in permeability coefficient can significantly reduce the water level passing through each air wall; therefore, passing through multiple air walls can lower the water level below the depth of the excavation pit. Specifically, this includes the following steps:

[0037] Step 1: According to the dewatering plan, install air inlets around the foundation pit. First, use a drilling rig to drill holes at the designed locations, drilling to a depth below the pre-inflation water level. Lay the air inlet pipes and place them at the designated depth. Then, continue backfilling with medium-coarse sand to 0.5 meters above the ground, followed by backfilling with clay to the ground level, ensuring that air bubbles are sealed within the soil during inflation. The diameter of the air inlets should be between 0.25m and 0.5m, and the drilling interval should be between 0.5m and 1m. The spacing and number of air inlets should also be determined based on the actual project conditions.

[0038] The inflation tube is made of steel, with petroleum jelly applied to the outside for lubrication and sealing, facilitating easy removal during and after construction, and preventing air bubbles from escaping from the tube wall. A filter screen is installed at the bottom of the inflation tube to prevent fine soil particles from entering and clogging the tube, reducing inflation efficiency and affecting the water-reducing effect of the aerated wall. A resistivity sensor is installed on the inner bottom wall of the inflation tube to monitor soil resistivity changes in real time. The change in soil saturation can be calculated based on the resistivity, determining whether inflation has reduced the soil saturation to the target level.

[0039] Step 2: After all backfilling is completed, set the inflation pressure and start inflation. The resistivity sensor at the bottom of the inflation tube monitors the change in soil saturation within the affected area in real time during the inflation process. When the saturation reaches the target saturation, pull the inflation tube up a certain height and continue inflation. Repeat this step until the bottom of the inflation tube reaches the water level line and stop inflation to meet the requirement of uniform bubble distribution during the inflation process.

[0040] Step 3: After the first air wall is formed, the foundation pit can be excavated to a certain depth, but it cannot exceed the water level that the first air wall can lower, that is, it cannot exceed the water level line after the first air wall is formed and inflated. Then, the support structure is installed. During the excavation process, the second air wall can be formed by inflating at the same time. The steps are the same as the engineering steps of the first air wall. After the second air wall is formed, continue to excavate and support. Repeat this cycle to form multiple air walls until the foundation pit excavation is completed. The width of the air wall is approximately between 0.5m and 1.5m, which is directly proportional to the diameter of the air pipe. The larger the diameter of the air pipe, the wider the air wall.

[0041] Step 4: After all the excavation work is completed, retrieve the air pipe and backfill the soil sample.

Claims

1. A construction method for a multi-layered air-wall seepage-blocking dewatering device for foundation pits, characterized in that, This multi-air-wall seepage-blocking dewatering device for foundation pits includes multiple air-filled holes arranged in the soil surrounding the foundation pit. Each air-filled hole is deeper than the pre-inflation water level. The diameter of the air-filled holes is between 0.25m and 0.5m, and the spacing is between 0.5m and 1m. Air is added to each hole sequentially along the downward trend of the pre-inflation water level. During inflation, the bottom of the inflation pipe is inserted into the air-filled hole until the water level is reached. A filter screen is installed at the bottom of the inflation pipe, and a resistivity sensor is installed on the inner wall near the bottom. The top of the inflation pipe extends beyond the air-filled hole and is connected to a compressor. After inflation, multiple air walls are formed, each with a depth greater than the pre-inflation water level and a width between 0.5m and 1.5m. The construction method includes the following steps: Multiple air holes are set up around the foundation pit, with the depth of each air hole exceeding the water level line before air inflation at its location. An air inflation pipe is then laid and placed to the designated depth, followed by backfilling the soil to the ground surface. Set the inflation pressure and begin inflation. The resistivity sensor at the bottom of the inflation tube monitors the soil saturation changes in real time during the inflation process. Once the target saturation is reached, pull up the inflation tube and continue inflation. Repeat this process until the bottom of the inflation tube reaches the water level line and inflation stops. The water level line formed after inflation is the post-inflation water level line. Compared with the water level line before inflation, the water level is the same before the first air wall. After passing through the first air wall, the water level line decreases. The post-inflation water level line after passing through the first air wall is parallel to the pre-inflation water level line. The remaining water level lines follow the same pattern. After the first air wall is formed, the foundation pit is excavated, but it must not be below the water level line after the first air wall is formed. Then the support structure is installed. Repeat the above steps to form multiple air walls until the foundation pit excavation is completed. After the excavation work was completed, the air pipes were retrieved and the soil samples were backfilled.

2. The construction method of a multi-layer air wall seepage-blocking dewatering device for foundation pits according to claim 1, characterized in that, The inflation tube is made of stainless steel and is coated with lubricant on the outside.

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