A bottom-up field immersion test apparatus and method for collapsible loess foundations

Abstract

This invention discloses a bottom-up field immersion test device and method for collapsible loess foundations. The device includes an immersion well and a field immersion test structure. The field immersion test structure includes an immersion pipe mechanism and a radial pipe mechanism. The radial pipe mechanism includes multiple sets of radial pipe components, each set of radial pipe units including multiple radial pipes arranged at an angle downwards, with multiple immersion holes arranged along the length of the radial pipes at the bottom. The immersion pipe mechanism includes multiple sets of immersion pipes arranged along the inner wall of the immersion well. The method includes the following steps: 1. Excavation of the immersion test pit and formation of the immersion well; 2. Installation of the radial pipe mechanism; 3. Installation of the immersion pipe mechanism; 4. Backfilling of the immersion well and installation of the water level monitoring pipe; 5. Installation of the monitoring structure; 6. Bottom-up field immersion test of the collapsible loess foundation. This invention simulates groundwater level rise conditions through bottom-up immersion, facilitating the determination of collapsibility type and collapsibility coefficient.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering testing technology, and in particular relates to a bottom-up field immersion test device and method for collapsible loess foundations. Background Technology

[0002] Western my country is home to a large amount of collapsible loess. As a typical aeolian soil, loess possesses characteristics such as high porosity, structure, collapsibility, water sensitivity, and dynamic vulnerability. Compared to other soil and rock materials, a prominent engineering problem with loess is that while it exhibits high strength and low compressibility under natural low moisture content conditions, its strength drops sharply and deformation increases dramatically once it is soaked in water, thus affecting the stability of surrounding structures or facilities. Therefore, when constructing projects in collapsible loess areas, it is usually necessary to measure the amount of collapsibility in the loess to determine the type and grade of site collapse.

[0003] Currently, commonly used methods for determining loess collapsibility can be divided into two main categories: laboratory testing and field immersion testing. Compared to laboratory testing, field immersion testing ensures a higher degree of consistency between the soil structure and stress state in the test area and actual working conditions. Based on the test results, the collapsibility deformation law of collapsible loess foundations can be directly derived, and the collapsibility coefficient corresponding to different depths can be calculated. Therefore, determining the site's collapsibility level is more reliable and widely used. However, current research on field immersion testing mainly focuses on ground engineering, specifically immersion paths from top to bottom, simulating conditions such as surface water infiltration and pipeline leakage. For urban rail transit projects in loess areas, the burial depth of subway shield tunnels is generally around 15m to 20m. Surface water infiltration only causes minor collapsibility deformation in shallow loess, having little impact on deep loess and the tunnel structure. However, if a rise in groundwater level occurs (water seepage from bottom to top), the structure of deep loess gradually deteriorates. With the overlying load remaining essentially unchanged (or even increasing when surface water infiltrates), the subsidence deformation in the deeper loess foundation will be far greater than that in the shallower loess when surface water infiltrates, resulting in a greater impact on the structure of operating urban rail transit projects. If, in this situation, the results of on-site immersion tests along a top-down immersion path are still used to determine the type and level of subsidence and guide the construction of underground works within that site, structural safety will be threatened, and in severe cases, the normal operation of urban rail transit may even be affected.

[0004] Therefore, there is currently a lack of a reasonably designed on-site immersion test device and method for collapsible loess foundations from bottom to top. This device and method would simulate groundwater level rise by using immersion pipes at different depths from bottom to top and radiating pipes to achieve immersion from bottom to top. This would facilitate subsequent determination of the collapsibility type and collapsibility coefficient of collapsible loess foundations under groundwater level rise conditions, thereby making the collapsibility level determination more accurate and reliable. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a bottom-up field immersion test device for collapsible loess foundations, which addresses the shortcomings of the prior art. The device is reasonably designed and easy to operate. It achieves bottom-up immersion through immersion pipes at different depths and radial pipes, simulating the groundwater level rise condition. This facilitates the subsequent determination of the collapsibility type and collapsibility coefficient of the collapsible loess foundation under the groundwater level rise condition, thereby making the collapsibility level determination more accurate and reliable.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a field immersion test device for collapsible loess foundation from bottom to top, characterized in that: it includes multiple immersion wells and field immersion test structures arranged along the height direction of each immersion well, and each field immersion test structure includes an immersion pipe mechanism and a radial pipe mechanism.

[0007] The radial pipeline mechanism includes multiple sets of radial pipeline components arranged sequentially from bottom to top along the height direction of the immersion well. Each set of radial pipeline components includes multiple radial pipeline units arranged circumferentially along the inner wall of the immersion well. Each radial pipeline unit includes a radial tube embedded in the soil of the inner wall of the immersion well and arranged inclined downwards. The upper end of the radial tube near the soil of the inner wall of the immersion well is an open end, and the lower end of the radial tube extending into the soil of the inner wall of the immersion well is closed. Multiple immersion holes are opened at the bottom of the radial tube along the length direction of the radial tube.

[0008] The immersion pipe mechanism includes multiple sets of immersion pipe components arranged sequentially from bottom to top along the height direction of the immersion well. The number of sets of immersion pipe components is the same as the number of sets of radial pipe components. The bottom of the immersion pipe component in the same set is higher than the top of the radial tube in the radial pipe component.

[0009] Each group of the immersion pipeline components includes an immersion pipe laid along the inner wall of the immersion exploration well.

[0010] The above-mentioned field immersion test device for collapsible loess foundation is characterized in that: a concrete waterproof layer is provided at the bottom of the immersion test well.

[0011] The above-mentioned field immersion test device for collapsible loess foundation is characterized in that: the inner wall of the immersion well is provided with inclined radial holes, the radial tube is embedded in the radial holes, the top of the radial tube is attached to the top of the radial hole, and the gap between the outer wall of the radial tube and the inner wall of the radial hole is filled with a coarse sand layer.

[0012] Filter screens are installed at the open end of the radiant tube and at the immersion hole.

[0013] The above-mentioned field immersion test device for collapsible loess foundation is characterized in that: the end of the immersion pipe extending out of the top of the immersion well is equipped with a valve and a flow meter;

[0014] The immersion pipe is installed along the height direction of the immersion well from bottom to top by multiple fixing clamps to fit the immersion well sidewall.

[0015] The above-mentioned field immersion test device for collapsible loess foundation is characterized in that: a monitoring tube is set at the center of the concrete waterproof layer, the monitoring tube includes multiple water level monitoring tubes connected sequentially from bottom to top, and the bottom end of the bottom water level monitoring tube is fixedly installed on the concrete waterproof layer.

[0016] A steel ruler water level gauge is installed at the top of the immersion well.

[0017] The above-mentioned field immersion test device for collapsible loess foundation is characterized in that: the bottom of the immersion pipe is connected to the telescopic pipe by a pipe clamp, and the bottom of the telescopic pipe is connected to the soil on the inner wall of the immersion well by a fixing clamp.

[0018] Meanwhile, this invention also discloses a simple, rationally designed, and convenient method for conducting on-site immersion tests on collapsible loess foundations from bottom to top, characterized by the following steps:

[0019] The method includes the following steps:

[0020] Step 1: Excavation of the immersion test pit and formation of the immersion test well:

[0021] Step 101: Excavate a water immersion test pit in the collapsible loess foundation research site and obtain the saturated water content Wb of the soil.

[0022] Step 102: Set up multiple immersion well points at the bottom of the immersion test pit; wherein, the multiple immersion well points include six circumferential immersion well points arranged along the circumference of the immersion test pit and a central immersion well point set at the center of the immersion test pit.

[0023] Step 103: Excavate a water-soaked well at each water-soaked well location; wherein the bottom of the water-soaked well extends to the upper surface of the paleosol layer;

[0024] Step 104: Pour concrete into the bottom of the immersion well to form a concrete waterproof layer;

[0025] Step 2: Install the radiant ductwork mechanism:

[0026] Step 201: Set multiple levels of immersion height positions sequentially from bottom to top along the height direction of the immersion exploration well;

[0027] Step 202: Install radial pipe mechanisms at each immersion height position of the immersion well;

[0028] Step 3: Install the immersion pipe mechanism:

[0029] The process of installing immersion pipe mechanisms at various immersion heights in the immersion well is as follows:

[0030] Step 301: Connect the immersion pipe to the telescopic pipe using pipe clamps, and install a filter screen at the outlet end of the telescopic pipe to form an assembled immersion pipe;

[0031] Step 302: Place the assembled immersion pipe into the immersion test well until the bottom height of the telescopic pipe is the same as the current immersion height. Then, install the immersion pipe along the height direction of the immersion test well from bottom to top using multiple fixing clamps to fit the immersion pipe against the side wall of the immersion test well, thus completing the installation of the immersion pipeline mechanism at the current immersion height position. The end of the immersion pipe extending out of the top of the immersion test well is equipped with a valve and a flow meter.

[0032] Step 303: Repeat steps 301 and 302 multiple times to complete the installation of the immersion pipe mechanism at each immersion height position;

[0033] Step 4: Backfilling of the flooded exploratory well and installation of water level monitoring pipes:

[0034] Step 401: Install a water level monitoring pipe at the center of the concrete waterproof layer; wherein the bottom end of the water level monitoring pipe is fixedly installed on the concrete waterproof layer.

[0035] Step 402: Backfill the gap between the inner wall of the immersion well and the outer wall of the water level monitoring pipe with coarse sand until the top of the backfill layer reaches 2 / 3 of the height of the water level monitoring pipe;

[0036] Step 403: Connect the next section of the water level monitoring pipe to the current water level monitoring pipe;

[0037] Step 404: Continue as described in step 402 until the top of the next backfill layer reaches 2 / 3 of the height of the water level monitoring pipe of the next section;

[0038] Step 405: Repeat steps 402 to 404 multiple times until the top of the overall backfill layer is flush with the top of the immersion well, and the top of the last section of the water level monitoring pipe extends beyond the top of the immersion well.

[0039] Step 406: Set up a central monitoring point at the center of the triangular area formed by two adjacent circumferential immersion well points and the central immersion well point;

[0040] Step 407: Use a drilling rig to drill a central borehole at each central monitoring point;

[0041] Step 408: Lower the central water level monitoring pipe into the central borehole, with the top of the central water level monitoring pipe extending beyond the top of the central borehole; wherein, the central water level monitoring pipe includes multiple water level monitoring pipes connected in sequence.

[0042] Step 409: Install steel ruler water level gauges on the top of the flooded exploration well and the central borehole;

[0043] Step 5: Installation of the monitoring structure:

[0044] Step 501: Set up three monitoring lines at the bottom of the immersion test pit with the central immersion well point as the center, and set up multiple shallow markers on each monitoring line; wherein the included angle between two adjacent monitoring lines is 120°;

[0045] Step 502: At the bottom of the immersion test pit, set up three monitoring points along the line connecting the central immersion well point and the two circumferential immersion well points; wherein, the three monitoring points are respectively located in the radiation area of ​​the immersion well point corresponding to the central immersion well point and the two circumferential immersion well points.

[0046] Step 503: Excavate monitoring wells at the three monitoring points;

[0047] Step 504: Settlement monitoring devices and soil moisture meters are installed in each monitoring well from bottom to top, and the monitoring wells are backfilled in layers using loess excavated from the research site.

[0048] Step Six: On-site immersion test of collapsible loess foundation from bottom to top:

[0049] Step 601: Along the height direction of the immersion well, arrange the immersion height positions in multiple levels from bottom to top, and denot them as the first level immersion height position, ..., the i-th level immersion height position, ..., the I-th level immersion height position; where i and I are both positive integers, and 1≤i≤I;

[0050] Step 602: When i = 1, open the valve in the immersion pipe mechanism at the i-th immersion height position to allow the soil below the i-th immersion height position to be wetted by water;

[0051] Step 603: During the process of wetting the soil below the i-th level of immersion height, if the soil moisture content measured by each soil moisture meter in the soil below the i-th level of immersion height reaches Wb, then the valve of the immersion pipe is closed.

[0052] Step 604: Continuously monitor until the surface settlement stabilizes, obtain the surface deformation through shallow markers and record it as the total subsidence deformation Sb; and obtain the height of each layer of loess after water immersion through the settlement monitoring device for each layer; wherein, the height of a certain layer of loess below the i-th level of water immersion height after water immersion is h. i ′;

[0053] Step 605: If the total collapsible deformation Sb is greater than 70 mm, then the loess layer below the i-th level of immersion height is self-weight collapsible loess, and proceed to step 606; otherwise, it is non-self-weight collapsible loess.

[0054] Step 606, according to The self-weight collapsibility coefficient δ of the loess layer below the i-th level of immersion height is obtained. i ; where h i This indicates the height of the loess layer before immersion in water, below the i-th level of immersion height.

[0055] Step 607: Repeat the method described in steps 602 to 606 to wet the soil between the (i+1)th level immersion height position and the i-th level immersion height position, and obtain the self-weight collapsibility coefficient of each layer between the (i+1)th level immersion height position and the i-th level immersion height position, until the soil between the I-th level immersion height position and the I-1-th level immersion height position is wetted.

[0056] The above method is characterized in that: in step 202, a radial pipe mechanism is installed at each level of immersion height in the immersion well, and the specific process is as follows:

[0057] Step 2021: At a position 200mm lower than the current level of immersion height, multiple radial hole points are arranged along the circumferential direction of the inner wall of the immersion well. At each radial hole point, a spiral soil sampler is used to spiral downwards at an angle on the inner wall of the immersion well to form a radial hole; wherein, the radial holes are arranged at an angle.

[0058] Step 2022: Multiple immersion holes are provided at the bottom of the radiant tube along the length of the radiant tube; wherein, one end of the radiant tube is closed and the other end is open.

[0059] Step 2023: Install filter screens at the opening and immersion hole of the radiant tube to form an assembled radiant tube;

[0060] Step 2024: Place the assembled radiant tube into the radiant hole until the closed end of the radiant tube contacts the bottom end of the radiant hole, the top of the radiant tube fits against the top of the radiant hole, and a gap is reserved between the outer wall of the radiant tube and the inner wall of the radiant hole; wherein, the open end of the radiant tube is located at the high end of the radiant hole and is connected to the immersion well.

[0061] Step 2025: Fill the gap between the outer wall of the radiant tube and the inner wall of the radiant hole with coarse sand until the gap is filled, thus completing the installation of the radiant pipe unit in the current radiant hole.

[0062] Step 2026: Repeat steps 2022 to 2025 multiple times to complete the installation of the radiant pipe units in multiple radiant holes, thus completing the installation of the radiant pipe mechanism at the current level of immersion height.

[0063] Step 2027: Repeat steps 2021 to 2026 multiple times to complete the installation of the radiant pipe mechanism at each level of immersion height.

[0064] Compared with the prior art, the present invention has the following advantages:

[0065] 1. The field immersion test device for collapsible loess foundation from bottom to top of the present invention has a simple structure, reasonable design and easy installation and layout, and low investment cost. It improves the accuracy of judging the collapsibility type and collapsibility coefficient of collapsible loess foundation under the condition of groundwater level rise.

[0066] 2. The collapsible loess foundation field immersion test device of the present invention includes a radial pipe component and an immersion pipe component. Water is supplied through the immersion pipe component to wet the soil below the immersion level height, thereby realizing field immersion. The immersion pipe component is arranged in multiple ways from bottom to top along the height direction of the immersion well, and the immersion pipe component is opened from bottom to top for immersion. The radial pipe component is inclined and embedded in the soil of the inner wall of the immersion well, thereby facilitating the immersion of the lower soil.

[0067] 3. In this invention, the bottom of the immersion pipe component in the same group is higher than the high end of the radiant pipe in the radiant pipe component, which facilitates the water in the immersion pipe component to enter the opening end of the radiant pipe component, so as to realize the soil below each level of immersion height being wetted by water.

[0068] 4. By using immersion pipe components and radial pipe components of different depths to immerse water from bottom to top, this invention can simulate the groundwater level rise in actual engineering projects, which facilitates the subsequent determination of the collapsibility type and collapsibility coefficient of collapsible loess foundation under the groundwater level rise condition.

[0069] 5. The method for bottom-up field immersion testing of collapsible loess foundations in this invention is simple, convenient, and easy to operate. First, the immersion test pit is excavated and the immersion well is formed. Second, the radial pipeline mechanism and the immersion pipeline mechanism are installed. Next, the immersion well is backfilled and the water level monitoring pipe and the monitoring structure are installed. Finally, the collapsible loess foundation is subjected to bottom-up field immersion testing to obtain the collapsibility type and self-weight collapsibility coefficient, which further facilitates the subsequent determination of the collapsibility level of the site.

[0070] In summary, this invention is reasonably designed and easy to operate. It achieves bottom-up immersion through a water-immersion pipe mechanism at different depths from bottom to top and a radial pipe mechanism, simulating the groundwater level rise condition. This facilitates the subsequent determination of the collapsibility type and collapsibility coefficient of collapsible loess foundation under the groundwater level rise condition, thereby making the collapsibility level determination more accurate and reliable.

[0071] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the on-site immersion test device for collapsible loess foundation from bottom to top according to the present invention.

[0073] Figure 2 This is a schematic diagram of the structure of the radiant pipe component of the present invention.

[0074] Figure 3 This is a schematic diagram of the structure of the water immersion pipe component of the present invention.

[0075] Figure 4 This is a schematic diagram of the water immersion pipe mechanism of the present invention.

[0076] Figure 5 This is a schematic diagram of the monitoring points for the bottom-up field immersion test method for collapsible loess foundations according to the present invention.

[0077] Figure 6 This is a schematic diagram of the installation of the monitoring structure for the bottom-up field immersion test method for collapsible loess foundations according to the present invention.

[0078] Figure 7 This is a schematic diagram of the process for the bottom-up field immersion test method for collapsible loess foundations according to the present invention.

[0079] Explanation of reference numerals in the attached figures:

[0080] 1—Water immersion test pit; 2-1—Water immersion exploratory well; 2-2—Integral backfill layer;

[0081] 2-3—Concrete waterproof layer; 3-1—Valve; 3-2—Flow meter;

[0082] 3-3—Immersion pipe; 3-4—Fixing clamp; 3-5—Pipe clamp;

[0083] 3-6—Telescopic tube; 3-7—Filter screen;

[0084] 4-1—Radial aperture; 4-2—Radial tube; 4-3—Coarse sand filling layer;

[0085] 4-4—Immersion hole; 5—Steel ruler water level gauge; 5-1—Water level monitoring tube;

[0086] 5-2—Water level gauge probe; 5-3—Steel tape measure cable; 5-4—Winding reel;

[0087] 6—Paleosol layer; 7—Monitoring point location; 7-1—Shallow marker;

[0088] 7-2—Monitoring well; 7-3—Settlement monitoring device; 7-4—Soil moisture meter;

[0089] 8—Central water level monitoring pipe; 9—Radiation area; 10—Central immersion exploration well location;

[0090] 11—Position of circumferentially submerged exploration well. Detailed Implementation

[0091] like Figures 1 to 4 The device shown is a bottom-up field immersion test device for collapsible loess foundation, including multiple immersion test wells 2-1 and field immersion test structures arranged along the height direction of each of the immersion test wells 2-1. Each field immersion test structure includes an immersion pipe mechanism and a radial pipe mechanism.

[0092] The radial pipeline mechanism includes multiple sets of radial pipeline components arranged sequentially from bottom to top along the height direction of the immersion well 2-1. Each set of radial pipeline components includes multiple radial pipeline units arranged circumferentially along the inner wall of the immersion well 2-1. Each radial pipeline unit includes a radial pipe 4-2 embedded in the soil of the inner wall of the immersion well 2-1 and arranged inclined downwards. The upper end of the radial pipe 4-2 near the soil of the inner wall of the immersion well 2-1 is an open end. The lower end of the radial pipe 4-2 extending into the soil of the inner wall of the immersion well 2-1 is closed. Multiple immersion holes 4-4 are provided at the bottom of the radial pipe 4-2 along the length direction of the radial pipe 4-2.

[0093] The immersion pipe mechanism includes multiple sets of immersion pipe components arranged sequentially from bottom to top along the height direction of the immersion well 2-1. The number of sets of immersion pipe components is the same as the number of sets of radial pipe components. The bottom of the immersion pipe component in the same set is higher than the high end of the radial pipe 4-2 in the radial pipe component.

[0094] Each group of the immersion pipe components includes an immersion pipe 3-3 laid along the inner wall of the immersion exploration well 2-1.

[0095] In this embodiment, a concrete waterproof layer 2-3 is provided at the bottom of the immersion well 2-1.

[0096] In this embodiment, the inner wall of the immersion well 2-1 is provided with inclined radial holes 4-1, the radial tube 4-2 is embedded in the radial holes 4-1, the top of the radial tube 4-2 is attached to the top of the radial holes 4-1, and a coarse sand filling layer 4-3 is provided in the gap between the outer wall of the radial tube 4-2 and the inner wall of the radial holes 4-1.

[0097] A filter screen is installed at the open end of the radiant tube 4-2 and at the immersion hole 4-4.

[0098] In this embodiment, a valve 3-1 and a flow meter 3-2 are provided at the end of the immersion pipe 3-3 that extends out of the top of the immersion exploration well 2-1;

[0099] The immersion pipe 3-3 is installed along the height direction of the immersion well 2-1 from bottom to top by multiple fixing clamps 3-4 to fit the immersion pipe 3-3 against the side wall of the immersion well 2-1.

[0100] In this embodiment, a monitoring pipe is installed at the center of the concrete waterproof layer 2-3. The monitoring pipe includes multiple sections of water level monitoring pipe 5-1 connected sequentially from bottom to top. The bottom end of the bottommost water level monitoring pipe 5-1 is fixedly installed on the concrete waterproof layer 2-3.

[0101] A steel ruler water level gauge 5 is installed at the top of the immersion well 2-1.

[0102] In this embodiment, the bottom of the immersion pipe 3-3 is connected to the telescopic pipe 3-6 via a pipe clamp 3-5, and the bottom of the telescopic pipe 3-6 is connected to the soil on the inner wall of the immersion well 2-1 via a fixing clamp 3-4.

[0103] In this embodiment, the thickness of the concrete waterproof layer 2-3 is 100mm; the concrete waterproof layer 2-3 is set to prevent water from directly seeping away under the influence of gravity during the test.

[0104] In this embodiment, three levels of immersion height are arranged sequentially from bottom to top along the height direction of the immersion well 2-1. There are three groups of immersion pipe components and three groups of radial pipe components. The bottom of each immersion pipe component is the same as the immersion height position, and the bottom of the immersion pipe component in the same group is higher than the high end of the radial pipe 4-2 in the radial pipe component, so that water in the immersion pipe component can enter the opening end of the radial pipe component and realize the soil below each level of immersion height position is wetted by water.

[0105] In this embodiment, the three sets of immersion pipe components are evenly distributed along the circumference of the immersion well 2-1, and the immersion pipe components and the radial pipe unit are staggered, with the included angle between two adjacent immersion pipe components being 120°.

[0106] In this embodiment, the bottom of the immersion pipe 3-3 is connected to the telescopic pipe 3-6 via a pipe clamp 3-5, and the bottom of the telescopic pipe 3-6 is connected to the inner wall of the soil of the immersion well 2-1 via a fixing clamp 3-4. This is to ensure that the bottom of the telescopic pipe 3-6 changes synchronously with the soil of the inner wall of the immersion well 2-1, thereby adapting to soil settlement during subsequent immersion and ensuring that the bottom of the immersion pipe component is at the same position as the immersion height of each stage.

[0107] In this embodiment, the radial hole 4-1 is inclined for two reasons. First, it is to adapt to the narrow space inside the immersion well 2-1, so as to facilitate the formation of the immersion well by using a spiral soil sampler to spiral downwards on the inner side wall of the immersion well. Second, it is to facilitate the inclined arrangement of the radial tube 4-2 along the radial hole 4-1, thereby facilitating the immersion of the lower soil.

[0108] In this embodiment, the top of the radiating tube 4-2 is attached to the top of the radiating hole 4-1. A coarse sand filling layer 4-3 is provided in the gap between the outer wall of the radiating tube 4-2 and the inner wall of the radiating hole 4-1. The coarse sand filling layer 4-3 enables the radiating tube 4-2 to bear the load, preventing the immersion hole 4-4 from directly contacting the bottom of the radiating hole 4-1 and causing blockage, thereby reducing the amount of soil in the lower part of the immersion and affecting the experimental results; in addition, it can also prevent the hole from collapsing and improve the stability of immersion.

[0109] like Figures 5 to 7 The method for conducting a bottom-up field immersion test on collapsible loess foundation, as shown, includes the following steps:

[0110] Step 1: Excavation of the immersion test pit and formation of the immersion test well:

[0111] Step 101: Excavate a water immersion test pit 1 in the collapsible loess foundation research site and obtain the saturated water content Wb of the soil.

[0112] Step 102: Arrange multiple immersion well points in the bottom of the immersion test pit 1; wherein, the multiple immersion well points include six circumferential immersion well points 11 arranged along the circumference of the immersion test pit 1 and a central immersion well point 10 set at the center of the immersion test pit 1.

[0113] Step 103: Excavate a water-soaked well 2-1 at each water-soaked well location; wherein the bottom of the water-soaked well 2-1 extends to the upper surface of the paleosol layer 6;

[0114] Step 104: Pour concrete into the bottom of the immersion well 2-1 to form a concrete waterproof layer 2-3;

[0115] Step 2: Install the radiant ductwork mechanism:

[0116] Step 201: Set multiple levels of immersion height along the height direction of the immersion exploration well 2-1 from bottom to top;

[0117] Step 202: Install radial pipe mechanisms at each level of immersion height in the immersion well 2-1;

[0118] Step 3: Install the immersion pipe mechanism:

[0119] The immersion pipeline mechanism is installed at each immersion height position of the immersion test well 2-1. The specific process is as follows:

[0120] Step 301: Connect the immersion pipe 3-3 to the telescopic pipe 3-6 through the pipe clamp 3-5, and install the filter screen 3-7 at the outlet end of the telescopic pipe 3-6 to form the assembled immersion pipe;

[0121] Step 302: Place the assembled immersion pipe into the immersion well 2-1 until the bottom height of the telescopic pipe 3-6 is the same as the current immersion height. Then, install the immersion pipe 3-3 against the side wall of the immersion well 2-1 from bottom to top along the height direction of the immersion well 2-1 using multiple fixing clamps 3-4, thus completing the installation of the immersion pipe mechanism at the current immersion height. The end of the immersion pipe 3-3 extending out of the top of the immersion well 2-1 is equipped with a valve 3-1 and a flow meter 3-2.

[0122] Step 303: Repeat steps 301 and 302 multiple times to complete the installation of the immersion pipe mechanism at each immersion height position;

[0123] Step 4: Backfilling of the flooded exploratory well and installation of water level monitoring pipes:

[0124] Step 401: Install a water level monitoring pipe 5-1 at the center of the concrete waterproof layer 2-3; wherein the bottom end of the water level monitoring pipe 5-1 is fixedly installed on the concrete waterproof layer 2-3.

[0125] Step 402: Backfill the gap between the inner wall of the immersion well 2-1 and the outer wall of the water level monitoring pipe 5-1 with coarse sand until the top of the backfill layer reaches 2 / 3 of the height of the water level monitoring pipe 5-1.

[0126] Step 403: Connect the next section of water level monitoring pipe 5-1 to the current water level monitoring pipe 5-1;

[0127] Step 404: Continue as described in step 402 until the top of the next backfill layer reaches 2 / 3 of the height of the water level monitoring pipe 5-1 of the next section;

[0128] Step 405: Repeat steps 402 to 404 multiple times until the top of the overall backfill layer 2-2 is flush with the top of the immersion well 2-1, and the top of the last section of the water level monitoring pipe 5-1 extends beyond the top of the immersion well 2-1.

[0129] Step 406: Set up a central monitoring point at the center of the triangular area formed by two adjacent circumferential water-soaked exploration well points 11 and the central water-soaked exploration well point 10;

[0130] Step 407: Use a drilling rig to drill a central borehole at each central monitoring point;

[0131] Step 408: Lower the central water level monitoring pipe 8 into the central borehole, with the top of the central water level monitoring pipe 8 extending beyond the top of the central borehole; wherein, the central water level monitoring pipe 8 includes multiple water level monitoring pipes 5-1 connected in sequence;

[0132] Step 409: Install steel ruler water level gauge 5 on the top of the flooded exploration well 2-1 and the central borehole;

[0133] Step 5: Installation of the monitoring structure:

[0134] Step 501: Set up three monitoring lines at the bottom of the immersion test pit 1 with the central immersion well point 10 as the center, and set up multiple shallow markers 7-1 on each monitoring line; wherein the included angle between two adjacent monitoring lines is 120°.

[0135] Step 502: At the bottom of the immersion test pit 1, three monitoring points 7 are set up on the line connecting the central immersion well point 10 and the two circumferential immersion well points 11; wherein, the three monitoring points are respectively located in the radiation area of ​​the immersion well 2-1 corresponding to the central immersion well point 10 and the two circumferential immersion well points 11.

[0136] Step 503: Excavate monitoring wells 7-2 at the three monitoring points;

[0137] Step 504: Settlement monitoring device 7-3 and soil moisture meter 7-4 are installed in each monitoring well 7-2 from bottom to top, and the monitoring well 7-2 is backfilled in layers with loess excavated in the research site.

[0138] Step Six: On-site immersion test of collapsible loess foundation from bottom to top:

[0139] Step 601: Along the height direction of the immersion well 2-1, arrange the immersion height positions in multiple levels from bottom to top, and denot them as the first level immersion height position, ..., the i-th level immersion height position, ..., the I-th level immersion height position; where i and I are both positive integers, and 1≤i≤I;

[0140] Step 602: When i = 1, open valve 3-1 in the immersion pipe mechanism at the i-th immersion height position to allow the soil below the i-th immersion height position to be wetted by water;

[0141] Step 603: During the process of wetting the soil below the i-th level of immersion height, so that the soil moisture content measured by each soil moisture meter 7-4 in the soil below the i-th level of immersion height reaches Wb, then the valve 3-1 of the immersion pipe 3-3 is closed.

[0142] Step 604: Continuously monitor until the surface settlement stabilizes. Obtain the surface deformation amount through shallow marker 7-1 and record it as the total subsidence deformation Sbi; and obtain the height of each layer of loess after water immersion through the settlement monitoring device 7-3; wherein, the height of a certain layer of loess below the i-th level of water immersion height after water immersion is h. i ′;

[0143] Step 605: If the total collapsible deformation Sbi is greater than 70mm, then the loess layer below the i-th level of immersion height is self-weight collapsible loess, and proceed to step 606; otherwise, it is non-self-weight collapsible loess.

[0144] Step 606, according to The self-weight collapsibility coefficient δ of the loess layer below the i-th level of immersion height is obtained. i ; where h i This indicates the height of the loess layer before immersion in water, below the i-th level of immersion height.

[0145] Step 607: Repeat the method described in steps 602 to 606 to wet the soil between the (i+1)th level immersion height position and the i-th level immersion height position, and obtain the self-weight collapsibility coefficient of each layer between the (i+1)th level immersion height position and the i-th level immersion height position, until the soil between the I-th level immersion height position and the I-1-th level immersion height position is wetted.

[0146] In this embodiment, step 202 involves installing radial pipe mechanisms at various immersion heights of the immersion well 2-1. The specific process is as follows:

[0147] Step 2021: At a position 200mm lower than the current level of immersion height, multiple radial hole points are arranged along the circumferential direction of the inner wall of the immersion well 2-1. At each radial hole point, a spiral soil sampler is used to spiral downwards at an angle on the inner wall of the immersion well 2-1 to form a radial hole 4-1; wherein, the radial holes 4-1 are arranged at an angle.

[0148] Step 2022: A plurality of immersion holes 4-4 are provided at the bottom of the radiant tube 4-2 along the length of the radiant tube 4-2; wherein, one end of the radiant tube 4-2 is closed and the other end of the radiant tube 4-2 is open.

[0149] Step 2023: Install filter screens at the opening of the radiant tube 4-2 and the water immersion hole 4-4 to form the assembled radiant tube 4-2;

[0150] Step 2024: Place the assembled radiant tube 4-2 into the radiant hole 4-1 until the closed end of the radiant tube 4-2 contacts the bottom end of the radiant hole 4-1, the top of the radiant tube 4-2 fits against the top of the radiant hole 4-1, and a gap is reserved between the outer wall of the radiant tube 4-2 and the inner wall of the radiant hole 4-1; wherein, the open end of the radiant tube 4-2 is located at the high end of the radiant hole 4-1 and is connected to the water-immersed exploration well 2-1;

[0151] Step 2025: Fill the gap between the outer wall of the radiant tube 4-2 and the inner wall of the radiant hole 4-1 with coarse sand until the gap is filled, thus completing the installation of the radiant pipe unit in the current radiant hole.

[0152] Step 2026: Repeat steps 2022 to 2025 multiple times to complete the installation of the radiant pipe units in multiple radiant holes 4-1, thus completing the installation of the radiant pipe mechanism at the current level of immersion height.

[0153] Step 2027: Repeat steps 2021 to 2026 multiple times to complete the installation of the radiant pipe mechanism at each level of immersion height.

[0154] In this embodiment, it should be noted that the bottom of the immersion well 2-1 extends to the upper surface of the paleosol layer 6, ensuring that the immersion test of the collapsible loess foundation research site is achieved without any settlement at the bottom of the immersion well 2-1 or any water infiltration.

[0155] In this embodiment, flow meter 3-2 is set up to obtain the immersion volume of each level when the ground surface settles and the immersion height position is reached.

[0156] In this embodiment, the water level probe 5-2 is placed in the water level monitoring pipe 5-1 and the central water level monitoring pipe 8 inside the immersion well 2-1 to achieve water level monitoring, ensure that the water level in each immersion well 2-1 is the same, and ensure that the immersion height in the collapsible loess foundation research site is basically consistent.

[0157] In this embodiment, the diameter of the immersion test pit 1 is not less than 10m; the diameter of the immersion exploration well 2-1 is not less than 800mm.

[0158] In this embodiment, the diameter of the central borehole is adapted to the outer diameter of the central water level monitoring pipe 8, which just meets the requirements for lowering the central water level monitoring pipe 8; however, the diameter of the immersion well 2-1 is larger than the diameter of the water level monitoring pipe 5-1, so the bottom end of the water level monitoring pipe 5-1 needs to be fixedly installed on the concrete waterproof layer 2-3 at the bottom of the immersion well 2-1.

[0159] In this embodiment, I = 3, which represent the first level of immersion height position, ..., the i-th level of immersion height position, ..., the i-th level of immersion height position.

[0160] In this embodiment, the monitoring well 7-3 was backfilled in layers to ensure that the backfill layer had the same dry density as the collapsible loess foundation research site.

[0161] In this embodiment, in step 604, the surface subsidence is stable, meaning the subsidence rate is less than 0.04 mm / d.

[0162] In this embodiment, the centerline of the radiation hole 4-1 is located below the horizontal plane and forms an angle α with the horizontal plane, where α is an acute angle, and is more preferably 15°.

[0163] In this embodiment, there are 8 radiation tubes 4-2 at the same height, and the diameter of the radiation hole 4-1 is 150mm.

[0164] In this embodiment, the diameter of the radiant tube 4-2 is 100mm, the thickness is 10mm, and the length is 1.5m; there are 14 immersion holes 4-4, the diameter of each immersion hole 4-4 is 30mm, and the distance between two adjacent immersion holes 4-4 is 100mm.

[0165] In this embodiment, the outer diameter of the immersion pipe 3-3 is 110 mm and the wall thickness is 6.6 mm.

[0166] In this embodiment, when used in practice, the fixing clamp 3-4 includes a clamp part sleeved on the immersion pipe 3-3 and an anchoring part connected to the clamp and extending into the soil, thereby installing the immersion pipe 3-3 along the side wall of the immersion well 2-1 to avoid displacement.

[0167] In this embodiment, when used in practice, the shallow mark 7-1 is a cement pier, and vertical round steel bars are inserted into the cement pier.

[0168] In this embodiment, when in use, the water level gauge probe 5-2 is placed into the water level monitoring tube 5-1 and the central water level monitoring tube 8 in the immersion well 2-1 through the steel tape water level gauge 5 via the steel tape cable 5-3 to realize water level detection, and the receiving system and winding reel 5-4 for the steel tape cable 5-3 to be wound are placed outside the top of the immersion well 2-1.

[0169] In this embodiment, when used specifically, the settlement monitoring device 7-3 can refer to the deep settlement monitoring device disclosed in the paper "Development of Wire-type Deep Settlement Monitoring Device" published in April 2022, Volume 18, Issue 2, or other devices that can achieve the same function.

[0170] In this embodiment, when used in practice, the soil between two adjacent anchor heads in the settlement monitoring device 7-3 from bottom to top is a single layer of soil, and the bottommost anchor head is located at the bottom of the monitoring well 7-2, so no settlement occurs.

[0171] Thus, the height of each layer of loess below the i-th level of immersion height before immersion is the initial height difference between two adjacent anchor heads in the soil below the i-th level of immersion height; the height of each layer of loess below the i-th level of immersion height after immersion is the height difference between two adjacent anchor heads in the soil below the i-th level of immersion height after the immersion surface settlement has stabilized.

[0172] In this embodiment, when used in practice, the area formed by the projection of the radial tube 4-2 at the six circumferential immersion well points 11 is the radiation area 9, and two adjacent radiation areas 9 are attached to each other; and the edge of the radiation area 9 formed by the projection of the radial tube 4-2 at the central immersion well point 10 is attached to the circumferential radiation area 9.

[0173] In this embodiment, when used in practice, the first monitoring point is located in the radiation area of ​​the immersion well 2-1 corresponding to the circumferential immersion well point 11, the second monitoring point is located in the radiation area of ​​the immersion well 2-1 at the central immersion well point 10, and the third monitoring point is located in the radiation area of ​​the immersion well 2-1 corresponding to the other circumferential immersion well point 11.

[0174] In summary, this invention is reasonably designed and easy to operate. It achieves bottom-up immersion through a water-immersion pipe mechanism at different depths from bottom to top and a radial pipe mechanism, simulating the groundwater level rise condition. This facilitates the subsequent determination of the collapsibility type and collapsibility coefficient of collapsible loess foundation under the groundwater level rise condition, thereby making the collapsibility level determination more accurate and reliable.

[0175] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A bottom-up field immersion test device for collapsible loess foundations, characterized in that... It includes multiple immersion test wells (2-1) and field immersion test structures arranged along the height direction of each immersion test well (2-1). Each field immersion test structure includes an immersion pipe mechanism and a radial pipe mechanism. The radial pipeline mechanism includes multiple sets of radial pipeline components arranged sequentially from bottom to top along the height direction of the immersion well (2-1). Each set of radial pipeline components includes multiple radial pipeline units arranged circumferentially along the inner wall of the immersion well (2-1). Each radial pipeline unit includes a radial pipe (4-2) embedded in the soil of the inner wall of the immersion well (2-1) and arranged inclined downwards. The upper end of the radial pipe (4-2) near the soil of the inner wall of the immersion well (2-1) is an open end. The lower end of the radial pipe (4-2) extending into the soil of the inner wall of the immersion well (2-1) is closed. Multiple immersion holes (4-4) are opened at the bottom of the radial pipe (4-2) along the length direction of the radial pipe (4-2). The immersion pipe mechanism includes multiple sets of immersion pipe components arranged sequentially from bottom to top along the height direction of the immersion well (2-1). The number of sets of immersion pipe components is the same as the number of sets of radial pipe components. The bottom of the immersion pipe component in the same set is higher than the high end of the radial tube (4-2) in the radial pipe component. Each group of the immersion pipe components includes an immersion pipe (3-3) laid along the inner wall of the immersion exploration well (2-1).

2. The field immersion test device for collapsible loess foundation from bottom to top as described in claim 1, characterized in that: A concrete waterproof layer (2-3) is installed at the bottom of the immersion well (2-1).

3. The field immersion test device for collapsible loess foundation from bottom to top as described in claim 1, characterized in that: The inner wall of the immersion well (2-1) is provided with inclined radial holes (4-1), the radial tube (4-2) is embedded in the radial holes (4-1), the top of the radial tube (4-2) is attached to the top of the radial hole (4-1), and a coarse sand filling layer (4-3) is provided in the gap between the outer wall of the radial tube (4-2) and the inner wall of the radial hole (4-1); A filter screen is installed at the open end of the radiant tube (4-2) and at the immersion hole (4-4).

4. The field immersion test device for collapsible loess foundation from bottom to top as described in claim 1, characterized in that: The end of the immersion pipe (3-3) extending out of the top of the immersion exploration well (2-1) is equipped with a valve (3-1) and a flow meter (3-2); The immersion pipe (3-3) is installed along the height direction of the immersion well (2-1) from bottom to top by multiple fixing clamps (3-4) to fit the immersion pipe (3-3) against the side wall of the immersion well (2-1).

5. The field immersion test device for collapsible loess foundation from bottom to top as described in claim 2, characterized in that: A monitoring pipe is installed at the center of the concrete waterproof layer (2-3). The monitoring pipe includes multiple water level monitoring pipes (5-1) connected sequentially from bottom to top. The bottom end of the bottom water level monitoring pipe (5-1) is fixedly installed on the concrete waterproof layer (2-3). A steel ruler water level gauge (5) is installed at the top of the immersion well (2-1).

6. The field immersion test device for collapsible loess foundation from bottom to top as described in claim 1, characterized in that: The bottom of the immersion pipe (3-3) is connected to the telescopic pipe (3-6) via a pipe clamp (3-5), and the bottom of the telescopic pipe (3-6) is connected to the soil on the inner wall of the immersion well (2-1) via a fixing clamp (3-4).

7. A method for conducting a bottom-up field immersion test on a collapsible loess foundation using the apparatus described in claim 1, characterized in that, The method includes the following steps: Step 1: Excavation of the immersion test pit and formation of the immersion test well: Step 101: Excavate a water immersion test pit (1) in the collapsible loess foundation research site and obtain the saturated water content Wb of the soil. Step 102: Arrange multiple immersion well points in the bottom of the immersion test pit (1); wherein, the multiple immersion well points include six circumferential immersion well points (11) arranged along the circumference of the immersion test pit (1) and a central immersion well point (10) set at the center of the immersion test pit (1). Step 103: Excavate a water-soaked well (2-1) at each water-soaked well location; wherein the bottom of the water-soaked well (2-1) extends to the upper surface of the paleosol layer (6); Step 104: Pour concrete into the bottom of the immersion well (2-1) to form a concrete waterproof layer (2-3); Step 2: Install the radiant ductwork mechanism: Step 201: Set multiple levels of immersion height along the height direction of the immersion exploration well (2-1) from bottom to top; Step 202: Install radial pipe mechanisms at each level of immersion height in the immersion test well (2-1); Step 3: Install the immersion pipe mechanism: The immersion pipe mechanism is installed at each immersion height position of the immersion test well (2-1). The specific process is as follows: Step 301: Connect the immersion pipe (3-3) to the telescopic pipe (3-6) through the pipe clamp (3-5), and install a filter screen (3-7) at the outlet end of the telescopic pipe (3-6) to form an assembled immersion pipe; Step 302: Place the assembled immersion pipe into the immersion test well (2-1) until the bottom height of the telescopic pipe (3-6) is the same as the current immersion height. Then, along the height direction of the immersion test well (2-1), install the immersion pipe (3-3) against the side wall of the immersion test well (2-1) from bottom to top using multiple fixing clamps (3-4), thus completing the installation of the immersion pipe mechanism at the current immersion height. The end of the immersion pipe (3-3) extending out of the top of the immersion test well (2-1) is equipped with a valve (3-1) and a flow meter (3-2). Step 303: Repeat steps 301 and 302 multiple times to complete the installation of the immersion pipe mechanism at each immersion height. Step 4: Backfilling of the flooded exploratory well and installation of water level monitoring pipes: Step 401: Install a water level monitoring pipe (5-1) at the center of the concrete waterproof layer (2-3); wherein the bottom end of the water level monitoring pipe (5-1) is fixedly installed on the concrete waterproof layer (2-3); Step 402: Backfill the gap between the inner wall of the immersion well (2-1) and the outer wall of the water level monitoring pipe (5-1) with coarse sand until the top of the backfill layer reaches 2 / 3 of the height of the water level monitoring pipe (5-1); Step 403: Connect the next section of the water level monitoring pipe (5-1) to the current water level monitoring pipe (5-1); Step 404: Continue as described in step 402 until the top of the next backfill layer reaches 2 / 3 of the height of the water level monitoring pipe (5-1) of the next section; Step 405: Repeat steps 402 to 404 multiple times until the top of the overall backfill layer (2-2) is flush with the top of the immersion well (2-1), and the top of the last section of the water level monitoring pipe (5-1) extends beyond the top of the immersion well (2-1). Step 406: Set up a central monitoring point at the center of the triangular area formed by two adjacent circumferential immersion well points (11) and the central immersion well point (10); Step 407: Use a drilling rig to drill a central borehole at each central monitoring point; Step 408: Lower the central water level monitoring pipe (8) into the central borehole, with the top of the central water level monitoring pipe (8) extending beyond the top of the central borehole; wherein, the central water level monitoring pipe (8) includes multiple water level monitoring pipes (5-1) connected in sequence; Step 409: Install steel ruler water level gauges (5) on the top of the flooded exploration well (2-1) and the central borehole; Step 5: Installation of the monitoring structure: Step 501: Set up three monitoring lines at the bottom of the immersion test pit (1) with the central immersion well point (10) as the center, and set up multiple shallow markers (7-1) on each monitoring line; wherein the included angle between two adjacent monitoring lines is 120°. Step 502: At the bottom of the immersion test pit (1), set up three monitoring points (7) on the line connecting the central immersion well point (10) and the two circumferential immersion well points (11); wherein, the three monitoring points are respectively located in the radiation area of ​​the immersion well (2-1) corresponding to the central immersion well point (10) and the two circumferential immersion well points (11); Step 503: Excavate monitoring wells (7-2) at the three monitoring points; Step 504: Settlement monitoring devices (7-3) and soil moisture meters (7-4) are installed in each monitoring well (7-2) from bottom to top, and the monitoring wells (7-2) are backfilled in layers by compacting the excavated loess from the research site. Step Six: On-site immersion test of collapsible loess foundation from bottom to top: Step 601: Along the height direction of the immersion well (2-1), arrange the immersion height positions in multiple levels from bottom to top, and denot them as the first level immersion height position, ..., the i-th level immersion height position, ..., the I-th level immersion height position; where i and I are both positive integers, and 1≤i≤I; Step 602: When i = 1, open valve (3-1) in the immersion pipe mechanism at the i-th immersion height position to allow the soil below the i-th immersion height position to be wetted by water; Step 603: During the process of wetting the soil below the i-th level of immersion height, so that the soil moisture content measured by each soil moisture meter (7-4) in the soil below the i-th level of immersion height reaches Wb, then the valve (3-1) of the immersion pipe (3-3) is closed. Step 604: Continuously monitor until the surface settlement stabilizes. Obtain the surface deformation through shallow markers (7-1) and record it as the total subsidence deformation Sb(i); obtain the height of each layer of loess after water immersion through the settlement monitoring device (7-3); where the height of a certain layer of loess below the i-th level of water immersion height after water immersion is h. i ′; Step 605: If the total collapsible deformation Sb(i) is greater than 70 mm, then the loess layer below the i-th level of immersion height is self-weight collapsible loess, and proceed to step 606; otherwise, it is non-self-weight collapsible loess. Step 606, according to The self-weight collapsibility coefficient δ of the loess layer below the i-th level of immersion height is obtained. i ; where h i This indicates the height of the loess layer before immersion in water, below the i-th level of immersion height. Step 607: Repeat the method described in steps 602 to 606 to wet the soil between the (i+1)th level immersion height position and the i-th level immersion height position, and obtain the self-weight collapsibility coefficient of each layer between the (i+1)th level immersion height position and the i-th level immersion height position, until the soil between the I-th level immersion height position and the I-1-th level immersion height position is wetted.

8. The method according to claim 7, characterized in that: In step 202, radial pipe mechanisms are installed at various immersion heights of the immersion test well (2-1). The specific process is as follows: Step 2021: At a position 200mm lower than the current level of immersion height, multiple radial holes are arranged along the circumferential direction of the inner wall of the immersion well (2-1). At each radial hole point, a spiral soil sampler is used to spiral downwards at an angle on the inner wall of the immersion well (2-1) to form a radial hole (4-1); wherein, the radial holes (4-1) are arranged at an angle. Step 2022: A plurality of immersion holes (4-4) are provided at the bottom of the radiant tube (4-2) along the length of the radiant tube (4-2); wherein, one end of the radiant tube (4-2) is closed and the other end of the radiant tube (4-2) is open; Step 2023: Install filter screens at the opening and immersion hole (4-4) of the radiant tube (4-2) to form the assembled radiant tube (4-2); Step 2024: Place the assembled radiant tube (4-2) into the radiant hole (4-1) until the closed end of the radiant tube (4-2) contacts the bottom end of the radiant hole (4-1), the top of the radiant tube (4-2) fits against the top of the radiant hole (4-1), and a gap is reserved between the outer wall of the radiant tube (4-2) and the inner wall of the radiant hole (4-1); wherein, the open end of the radiant tube (4-2) is located at the high end of the radiant hole (4-1) and is connected to the immersion well (2-1); Step 2025: Fill the gap between the outer wall of the radiant tube (4-2) and the inner wall of the radiant hole (4-1) with coarse sand until the gap between the outer wall of the radiant tube (4-2) and the inner wall of the radiant hole (4-1) is filled, thus completing the installation of the radiant pipe unit in the current radiant hole. Step 2026: Repeat steps 2022 to 2025 multiple times to complete the installation of the radiant pipe units in multiple radiant holes (4-1), thus completing the installation of the radiant pipe mechanism at the current level of immersion height. Step 2027: Repeat steps 2021 to 2026 multiple times to complete the installation of the radiant pipe mechanism at each level of immersion height.

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