Recharge well structure and recharge construction method

Abstract

This invention discloses a reinjection well structure, including a reinjection well, a well casing, a water-stopping ring, and a reinjection pipeline assembly. The well casing is coaxially disposed within the reinjection well, and filler is used to fill the space between the outer wall of the well casing and the inner wall of the reinjection well. The well casing includes a sedimentation pipe section, a filter pipe section, and a solid pipe section connected sequentially from bottom to top. The water-stopping ring is disposed on the outer wall of the solid pipe section. The reinjection pipeline assembly includes a reinjection pipe, the upper end of which is located at the upper part of the reinjection well and connected to an external water source, and the lower end of which extends into the filter pipe section of the well casing. This invention also provides a reinjection construction method. The beneficial effects of this invention are: by setting a water-stopping ring in the well casing section, the seepage path of groundwater is increased; simultaneously, a secondary grouting process is used to seal the upper backfill layer, effectively ensuring the maximum allowable reinjection pressure of the reinjection well structure; and by adopting pressurized reinjection measures, the water level in the confined aquifer area with high water head is raised.

Description

Technical Field

[0001] This invention relates to the field of foundation pit excavation technology, specifically to a recharge well structure and a recharge construction method. Background Technology

[0002] With the increasing development of underground space, the excavation depth of foundation pits is also increasing. During the excavation process, groundwater issues are inevitable. The impact of deep well dewatering during foundation pit excavation on the surrounding environment is immeasurable. In areas within the influence zone of subways or tunnels, or in areas with numerous existing buildings and protected structures, the commonly used method is to use bottom-mounted waterstops to block groundwater connections for protection. However, during a construction period, groundwater levels fluctuate significantly, resulting in large pressure differences between the groundwater inside and outside the foundation pit. Leakage of the waterstops is frequent, leading to numerous engineering hazards. Furthermore, bottom-mounted waterstops permanently block groundwater hydraulic connections, causing irreparable damage to groundwater circulation, water resource recovery, and the ecological environment. In addition, bottom-mounted waterstops double the construction cost of foundation pits, and their service life is limited to the construction period, making them unrecoverable and resulting in a significant waste of resources.

[0003] Existing technologies include engineering attempts to control settlement by setting up recharge well structures and using recharge to reduce the drop in groundwater level, which involves injecting water into the soil layer under a certain recharge pressure. In areas with low aquifer head (usually referring to areas where the confined water level is more than 15m below the ground surface), recharge wells often use atmospheric pressure recharge or low-pressure recharge to achieve the recharge effect, meaning that the recharge head pressure is mostly at or slightly above the ground surface. However, in high-head confined aquifers (where the confined water level is no more than 15m below the ground), due to the high confined water head within the aquifer itself, if the applied recharge pressure is too low, the water level difference between the inside and outside of the recharge well will be small, resulting in insufficient driving force for water to flow into the aquifer. This makes it difficult to guarantee the recharge effect, and the groundwater level rise will be insignificant. Especially when the permeability coefficient of the target soil layer is low, water seeps into the underground soil layer slowly, failing to form seepage channels. To raise the groundwater level, the recharge well needs a water head pressure far exceeding the surface pressure, such as 0.1MPa, equivalent to a 10m high water head. Although increasing the recharge pressure can increase the water seepage velocity and facilitate groundwater level recovery, excessive recharge pressure can easily cause splitting and damage at the contact surface between the well wall and the soil layer, and the soil around the well is also prone to sudden surge damage, resulting in poor recharge effectiveness.

[0004] Therefore, it is necessary to improve existing technologies. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a recharge well structure and recharge construction method for high-pressure aquifers, aiming to improve the recharge effect.

[0006] The technical solution adopted in this invention is as follows: a reinjection well structure, including a reinjection well, a well pipe, a water-stopping ring, and a reinjection pipeline assembly; the well pipe is coaxially disposed within the reinjection well, and a filling structure is provided between the outer wall of the well pipe and the inner wall of the reinjection well; the well pipe includes a sedimentation pipe section, a filter pipe section, and a solid pipe section connected sequentially from bottom to top; the water-stopping element includes a water-stopping ring and a water-stopping cylinder, the inner ring of the water-stopping ring is fixed to the outer wall of the solid pipe section, and the outer ring of the water-stopping ring is connected to the inner wall of the water-stopping cylinder; the water-stopping ring is horizontally disposed, the water-stopping cylinder is coaxially disposed with the well pipe, and the water-stopping cylinder is embedded in the filling structure; the reinjection pipeline assembly includes a reinjection pipe, the upper end of which is located at the upper part of the reinjection well and is connected to an external water source, and the lower end of the reinjection pipe extends into the filter pipe section of the well pipe.

[0007] According to the above scheme, the reinjection well includes an upper well section and a lower well section connected together. The upper well section is a funnel-shaped structure with a large upper opening and a small lower opening. The lower opening of the upper well section is connected to the lower well section. The lower well section is a section with the same diameter.

[0008] According to the above scheme, the sedimentation pipe section and the filter pipe section are located in the lower well section, and the outer wall of the sedimentation pipe section and the outer wall of the filter pipe section are filled with filter material between the inner wall of the lower well section to form a filter material backfill layer.

[0009] According to the above scheme, the lower part of the solid pipe section is located within the lower well section, and the upper part of the solid pipe section passes through the upper well section; the outer wall of the solid pipe section located within the lower well section is filled with clay balls between it and the inner wall of the lower well section, forming a clay ball backfill layer.

[0010] According to the above scheme, the outer wall of the solid pipe section located in the upper well section and the inner wall of the upper well section are filled with cement grout or cement mortar to form a water-proof sealing layer; the outer end of the water-stop ring plate and the water-stop cylinder are both embedded in the water-proof sealing layer.

[0011] According to the above scheme, a return pump is installed at the lower end of the reinjection pipeline, and a water intake and a flow meter are sequentially installed at the upper end of the reinjection pipeline along the fluid flow direction; an inhibition valve is installed at the water intake.

[0012] According to the above scheme, the reinjection well structure is also equipped with a pressurization pipeline assembly, which includes a pressurization pipe, the lower end of which extends into the upper well section; the pressurization pipe is equipped with an inhibition valve, a flow meter, a pressure gauge, and a pressurization pump or a water storage tank.

[0013] According to the above scheme, both the solid pipe section and the sedimentation pipe section are made of steel pipe; the outer wall of the filter pipe section is wrapped with a filter screen.

[0014] The present invention also provides a method for reinjection construction, the method comprising the following steps:

[0015] Step 1: Set up the reinjection well: The lower section is formed by drilling, and the upper section is formed by excavating and enlarging the hole to form a funnel shape.

[0016] Step 2: On the ground, connect and install the sedimentation pipe section, filter pipe section and solid pipe section in sequence to form a well pipe, and wrap a filter screen around the outer wall of the filter pipe section.

[0017] Step 3: Lower the well casing wrapped with the filter screen into the reinjection well;

[0018] Step 4: Fill the space between the bottom outer wall of the well casing and the wall of the reinjection well with the corresponding filler material in a uniform manner from bottom to top, forming a filter material backfill layer and a clay ball backfill layer respectively.

[0019] Step 5: Weld a water-stop ring with a water-stop cylinder to the outer wall of the solid pipe;

[0020] Step 6: Backfill cement mortar between the outer wall of the solid pipe section and the upper well section to form a water-proof sealing layer;

[0021] Step 7: Insert the lower ends of the pressurization pipe and the reinjection pipe into the reinjection well, then weld and fix the sealing plate at the upper end of the well pipe, and install each pipeline component on the reinjection well.

[0022] Step 8: Inject water into the reinjection well structure, gradually increasing the reinjection pressure to the maximum allowable reinjection pressure in stages, and reinject the water into the soil layer through the filter pipe section of the reinjection well; at the same time, monitor the water head pressure in the soil layer, and when the water head pressure in the soil layer returns to the target water level, maintain the reinjection water volume and reinjection pressure in the reinjection well unchanged.

[0023] According to the above scheme, in step eight, the reinjection pressure is gradually increased from 0.1P to P, where P is the maximum allowable reinjection pressure calculated by the formation structure or the design reinjection pressure; when piping or sudden surge occurs on the ground, the pressurization is stopped and a secondary grouting process is used for sealing.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. This invention increases the seepage path of groundwater by setting water-stopping components in the well section, and at the same time uses a secondary grouting process to seal the upper grouting backfill layer, which can effectively ensure the maximum allowable backfilling pressure of the backfilling well structure and improve the backfilling effect; in addition, the use of pressurized backfilling measures raises the water level in the confined aquifer area with high water head.

[0026] 2. Under the action of reinjection pressure, when water flows out of the filter section of the reinjection well, it exhibits two directions: horizontal flow through the filter material towards the target reinjection layer and vertical flow upward along the well wall. This invention incorporates a water-stopping element in the well pipe section. Water in the reinjection well flows vertically upward along the contact surface between the outer wall of the well pipe and the soil of the grouting sealing layer. When it encounters the water-stopping element, the water flow path changes from vertical to a bypass path along the element (horizontal → vertical → horizontal → vertical), increasing seepage loss and making it difficult for water to flow along the well wall. Therefore, more water flows horizontally through the filter material towards the target reinjection layer, ensuring the maximum allowable reinjection pressure of the reinjection well structure and enhancing the reinjection effect.

[0027] 3. The upper section of the reinjection well in this invention is designed as a funnel-shaped structure with a larger upper opening and a smaller lower opening, while the lower section has a smaller diameter. This design increases the backfill space between the well casing and the wall of the reinjection well, which is beneficial for the construction of the water-proof sealing layer and can better ensure the sealing effect. By controlling the diameter of the lower section, a larger reinjection pressure can be maintained with a smaller reinjection volume. After the seepage channel is formed in the target permeable layer, the pressure difference inside and outside the reinjection well can be used to maintain the water head pressure of the target reinjection layer.

[0028] 4. This invention involves embedding secondary grouting pipes at different elevations of the backfill layer in the upper funnel-shaped structure. During the backfilling pressurization process, the pressure is gradually increased from 0.1P (where P is the maximum allowable backfilling pressure calculated based on the geological structure or the design backfilling pressure) to P, with each pressurization increment being approximately 0.1P. When piping or sudden surges occur on the ground, pressurization is stopped, and a secondary grouting process is used for sealing. The secondary grouting reinforces the sealing effect of the waterproof sealing layer, ensuring the backfilling pressure. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a specific embodiment of the present invention.

[0030] Figure 2 A top view showing the connection between the water-stopping component and the solid pipe.

[0031] Figure 3 An enlarged schematic diagram of the connection between the water-stopping component and the solid pipe.

[0032] In the diagram: 1. Municipal drainage pipe; 2. Suppression valve A; 3. Flow meter A; 4. Vent; 5. Suppression valve B; 6. Booster pump; 7. Flow meter B; 8. Pressure gauge B; 9. Natural ground elevation; 10. Water-stop ring; 11. Waterproof sealing layer; 12. Clay ball backfill layer; 13. Filter material backfill layer; 14. Return pump; 15. Sedimentation pipe section; 16. Filter pipe section; 17. Solid pipe section; 18. Upper well section; 19. Lower well section; 20. Recharge pipe; 21. Booster pipe. Detailed Implementation

[0033] To better understand the present invention, it will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 The diagram illustrates a reinjection well structure, comprising a reinjection well, a well casing, a water-stopping element, and a reinjection pipeline assembly. The well casing is coaxially disposed within the reinjection well, and a filling structure is provided between the outer wall of the well casing and the inner wall of the reinjection well. The well casing includes a sedimentation pipe section 15, a filter pipe section 16, and a solid pipe section 17 connected sequentially from bottom to top. The inner end of the water-stopping element is connected to the outer wall surface of the solid pipe section 17, and the outer end of the water-stopping element is embedded in the filling structure. The reinjection pipeline assembly includes a reinjection pipe 20, the upper end of which is located at the upper part of the reinjection well and connected to an external water source, and the lower end of which extends into the filter pipe section 16 of the well casing.

[0035] In this invention, both the solid pipe section 17 and the sedimentation pipe section 15 are made of steel pipe; the outer wall of the filter pipe section 16 is wrapped with a filter screen.

[0036] In this invention, the upper end of the well pipe extends out of the recharge well; the inner diameter of the recharge well exceeds 800 mm, and the inner diameter of the well pipe is less than 200 mm; the distance between the inner wall of the recharge well and the outer wall of the well pipe exceeds 300 mm. The top elevation of the recharge well is consistent with the natural ground elevation 9.

[0037] Preferably, such as Figure 2 and Figure 3 As shown, the water-stopping component includes a water-stopping ring 10 and a water-stopping cylinder 10.1. The inner ring of the water-stopping ring 10 is fixed to the outer wall of the solid pipe section 17, and the outer ring of the water-stopping ring 10 is connected to the inner wall of the water-stopping cylinder 10.1. The water-stopping ring 10 is horizontally arranged, and the water-stopping cylinder 10.1 is coaxially arranged with the well pipe, with both axes being vertical. The outer end of the water-stopping ring 10 and the water-stopping cylinder 10.1 are both embedded in the filling structure. In this invention, the middle part of the inner wall of the water-stopping cylinder 10.1 is connected to the outer ring of the water-stopping ring 10.

[0038] In this embodiment, there are two sets of water-stopping plates 10, which are fixed to the outer wall of the solid pipe section 17 of the well pipe with vertical spacing and parallel to each other; the structure of the water-stopping component is as follows: Figure 2 The number and spacing of the waterstop components can be adjusted appropriately according to the actual situation.

[0039] In this invention, the outer end of the water-stop ring 10 and the water-stop cylinder 10.1 are both embedded in the filling structure (that is, embedded in the water-proof sealing layer 11 mentioned later), which can increase the structural strength of the water-proof sealing layer (reinforced in cement grout or cement mortar), thereby improving its ability to resist sudden surges and effectively ensuring the maximum allowable backfill pressure.

[0040] Preferably, the reinjection well includes an upper section 18 and a lower section 19 connected to each other. The upper section 18 has a trumpet-shaped structure with a large upper opening and a small lower opening. The lower opening of the upper section 18 is connected to the lower section 19. The lower section 19 is a section with the same diameter.

[0041] In this invention, the upper well section 18 is excavated to form a well, and the lower well section 19 is formed by drilling.

[0042] Preferably, the sedimentation pipe section 15 and the filter pipe section 16 are located within the lower well section 19, and filter material is filled between the outer wall of the sedimentation pipe section 15 and the outer wall of the filter pipe section 16 and the inner wall of the lower well section 19 to form a filter material backfill layer 13.

[0043] In this invention, the filter media is medium-coarse sand filter media, and the filter media filling volume is not less than 95% of the total filling volume.

[0044] Preferably, the lower part of the solid pipe section 17 is located within the lower well section 19, and the upper part of the solid pipe section 17 passes through the upper well section 18.

[0045] In this invention, the upper opening of the solid pipe section 17 is provided with a sealing plate, and an exhaust port 4 is opened on the sealing plate.

[0046] Preferably, the outer wall of the solid pipe section 17 located in the lower well section 19 is filled with clay balls between it and the inner wall of the lower well section 19, forming a clay ball backfill layer 12.

[0047] Preferably, the space between the outer wall of the solid pipe section 17 located in the upper well section 18 and the inner wall of the upper well section 18 is filled with cement grout or cement mortar, and a water-proof sealing layer 11 is formed by a secondary grouting process; the outer end of the water-stop ring plate 10 and the water-stop cylinder 10.1 are both embedded in the water-proof sealing layer 11.

[0048] This invention utilizes cement grout or cement mortar to form a grouting backfill layer, also known as a waterproof sealing layer 11. Simultaneously, secondary grouting pipes are embedded at different elevations of the waterproof sealing layer 11 to perform secondary grouting, sealing small cracks in the backfill cement mortar and gaps between the cement mortar and the solid pipe 17. This secondary grouting process ensures the structural strength of the grouting backfill layer and also ensures a denser contact between the grouting backfill layer and the surrounding undisturbed soil, blocking groundwater seepage channels and better forming the waterproof sealing layer 11.

[0049] Preferably, a return pump 14 is provided at the lower end of the reinjection pipe 20, and a water intake and a flow meter A3 are sequentially provided at the upper end of the reinjection pipe 20 along the fluid flow direction; an inhibition valve A2 is installed at the water intake.

[0050] In this invention, the reinjection pipe 20 can be connected to the municipal drainage pipe 1 to draw water from the municipal drainage pipe 1.

[0051] Preferably, the reinjection well structure is further provided with a pressurization pipeline assembly, which includes a pressurization pipe 21, the lower end of which extends into the upper well section 18; the pressurization pipe 21 is provided with an inhibition valve B5, a flow meter B7, a pressure gauge 8, and a pressurization pump 6 or a water storage tank.

[0052] In this invention, the water head height in the reinjection well is increased by pressurizing pipeline components, so that the water head height in the reinjection well can be higher than the ground surface.

[0053] The present invention also provides a method for reinjection construction, the method being as follows:

[0054] Step 1: Constructing the Recharge Well: A lower well section 19 is formed by drilling. The upper section 18 is formed by excavating and enlarging the borehole to create a funnel-shaped opening. During excavation, a sealing plate is installed at the boundary between the upper well section 18 and the lower well section 19 to prevent excavated soil from falling into the lower well section 19 and affecting its construction quality. After the funnel-shaped opening of the upper well section 18 is formed, the sealing plate is removed.

[0055] Step 2: On the ground, install the sedimentation pipe section 15, the filter pipe section 16 and the solid pipe section 17 in sequence to form a well pipe, and wrap a filter screen around the outer wall of the filter pipe section 16.

[0056] Step 3: Lower the well casing with the filter screen into the reinjection well.

[0057] Step 4: Fill the gap between the bottom outer wall of the well pipe and the wall of the reinjection well with the corresponding filler material in a uniform manner from bottom to top, forming the filter material backfill layer 13 and the clay ball backfill layer 12 respectively.

[0058] Step 5: Weld a water-stop ring plate 10 with a water-stop cylinder 10.1 to the outer wall of the solid pipe 17. Depending on the length of the solid pipe 17, several sets of water-stop ring plates 10 can be welded.

[0059] Step 6: Backfill cement mortar between the outer wall of the solid pipe section 17 and the upper well section 18 and install a secondary grouting pipe. Grout the upper well section 18. After the cement mortar has solidified, seal the small cracks in the backfilled cement mortar and the gaps between the cement mortar and the solid pipe 17 by post-grouting to form a dense water-proof sealing layer 11 to prevent groundwater from surging up through the pipe wall.

[0060] Step 7: Insert the lower ends of the pressurization pipe 21 and the reinjection pipe 20 into the reinjection well, then weld and fix the sealing plate at the upper end of the well pipe (with the exhaust port 4 reserved), install each pipeline component on the reinjection well, and complete the construction of the reinjection well.

[0061] Step 8: After the recharge well construction is completed, fill the recharge well structure with water, start the pressurization pipeline 21 through the pressurization pump 6, and gradually increase the pressure in the pressurization pipeline 21 to the maximum allowable recharge pressure. The water is then continuously recharged into the soil layer through the filter pipe section of the recharge well to increase the water head pressure in the soil layer. At the same time, monitor the water head pressure in the soil layer. When the water head pressure in the soil layer returns to the target water level, maintain the recharge water volume and recharge pressure in the recharge well unchanged.

[0062] In step eight, during the reinjection pressurization process, the reinjection pressure is gradually increased from 0.1P (where P is the maximum allowable reinjection pressure calculated based on the geological structure or the design reinjection pressure) to P, with each pressurization increment being approximately 0.1P. When piping or sudden surges occur on the ground, pressurization is stopped, and a secondary grouting process is used for sealing. The secondary grouting reinforces the sealing effect of the waterproof sealing layer, ensuring the reinjection pressure.

[0063] Under the influence of reinjection pressure, water flowing out of the filter section of the reinjection well exhibits two directions: horizontal flow through the filter material towards the target reinjection layer and vertical upward flow along the well wall. This invention incorporates a water-stopping element in the well pipe section. Water in the reinjection well flows vertically upward along the contact surface between the outer wall of the well pipe and the soil of the grouting sealing layer. When encountering the water-stopping element, the water flow path changes from vertical to a bypass flow along the element (horizontal → vertical → horizontal → vertical), increasing seepage loss during flow and making it more difficult for water to flow along the well wall. This, in turn, increases the maximum allowable reinjection pressure of the reinjection well structure. Therefore, more water flows horizontally through the filter material towards the target reinjection layer, increasing the maximum allowable reinjection pressure and improving the reinjection effect. This allows reinjection as an engineering measure to be used in areas with abundant groundwater resources and high hydraulic heads, reducing groundwater level drops and surrounding ground subsidence during underground engineering development.

[0064] This invention can be used in recharge well structures for maintaining aquifer head pressure under conditions of foundation pit engineering and dewatering engineering.

[0065] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0066] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for constructing a reinjection well structure, the reinjection well structure comprising a reinjection well, a well pipe, a water-stopping element, and a reinjection pipeline assembly; the well pipe is coaxially disposed within the reinjection well, and a filling structure is provided between the outer wall of the well pipe and the inner wall of the reinjection well; the well pipe comprises a sedimentation pipe section, a filter pipe section, and a solid pipe section connected sequentially from bottom to top; the water-stopping element comprises a water-stopping ring and a water-stopping cylinder, the inner ring of the water-stopping ring being fixed to the outer wall of the solid pipe section, and the outer ring of the water-stopping ring being connected to the inner wall of the water-stopping cylinder; the water-stopping cylinder is embedded within the filling structure; the reinjection pipeline assembly comprises a reinjection pipe, the upper end of which is located at the upper part of the reinjection well and connected to an external water source, and the lower end of which extends into the filter pipe section of the well pipe; characterized in that The method includes the following steps: Step 1: Set up the reinjection well: The lower section is formed by drilling, and the upper section is formed by excavating and enlarging the hole to form a funnel shape. Step 2: On the ground, connect and install the sedimentation pipe section, filter pipe section and solid pipe section in sequence to form a well pipe, and wrap a filter screen around the outer wall of the filter pipe section. Step 3: Lower the well casing wrapped with the filter screen into the reinjection well; Step 4: Fill the space between the bottom outer wall of the well casing and the wall of the reinjection well with the corresponding filler material in a uniform manner from bottom to top, forming a filter material backfill layer and a clay ball backfill layer respectively. Step 5: Weld a water-stop ring with a water-stop cylinder to the outer wall of the solid pipe; the water-stop ring is set horizontally, and the water-stop cylinder is coaxially configured with the well pipe; both the water-stop ring and the water-stop cylinder are located in the upper section of the well in the shape of a funnel. Step 6: Backfill cement mortar between the outer wall of the solid pipe section and the upper well section to form a water-proof sealing layer; bury secondary grouting pipes at different elevations of the water-proof sealing layer to perform secondary grouting on the water-proof sealing layer, sealing the cracks in the backfill cement mortar and the gaps between the cement mortar and the solid pipe. Step 7: Insert the lower ends of the pressurization pipe and the reinjection pipe into the reinjection well, then weld and fix the sealing plate at the upper end of the well pipe, and install each pipeline component on the reinjection well. Step 8: Fill the reinjection well structure with water, start the pressurization pipeline through the pressurization pump, and gradually increase the pressure in the pressurization pipeline to the maximum allowable reinjection pressure. Reinject the water into the soil layer through the filter section of the reinjection well. At the same time, monitor the water head pressure in the soil layer. When the water head pressure in the soil layer returns to the target water level, maintain the reinjection water volume and reinjection pressure in the reinjection well unchanged.

2. The reinjection construction method as described in claim 1, characterized in that, In step eight, the reinjection pressure is gradually increased from 0.1P to P, where P is the maximum allowable reinjection pressure calculated based on the geological structure or the design reinjection pressure. When piping or sudden surge occurs on the ground, the pressurization is stopped, and a secondary grouting process is used for sealing.

3. The reinjection construction method as described in claim 1, characterized in that, The reinjection well includes an upper section and a lower section connected together. The upper section has a funnel-shaped structure with a larger upper opening and a smaller lower opening. The lower opening of the upper section is connected to the lower section. The lower section is a section with a constant diameter.

4. The reinjection construction method as described in claim 3, characterized in that, The sedimentation pipe section and the filter pipe section are located in the lower well section, and the outer wall of the sedimentation pipe section and the outer wall of the filter pipe section are filled with filter material between them and the inner wall of the lower well section to form a filter material backfill layer.

5. The reinjection construction method as described in claim 3, characterized in that, The lower part of the solid pipe section is located within the lower well section, and the upper part of the solid pipe section passes through the upper well section; the outer wall of the solid pipe section located within the lower well section is filled with clay balls between it and the inner wall of the lower well section, forming a clay ball backfill layer.

6. The reinjection construction method as described in claim 5, characterized in that, The outer wall of the solid pipe section located in the upper well section and the inner wall of the upper well section are filled with cement grout or cement mortar to form a water-proof sealing layer; the outer end of the water-stop ring and the water-stop cylinder are both embedded in the water-proof sealing layer.

7. The reinjection construction method as described in claim 3, characterized in that, A return pump is installed at the lower end of the reinjection pipeline, and a water intake and a flow meter are sequentially installed at the upper end of the reinjection pipeline along the fluid flow direction; an inhibition valve is installed at the water intake.

8. The reinjection construction method as described in claim 4, characterized in that, The reinjection well structure is also equipped with a pressurization pipeline assembly, which includes a pressurization pipe, the lower end of which extends into the upper well section; the pressurization pipe is equipped with an inhibition valve, a flow meter, a pressure gauge, and a pressurization pump or a water storage tank.

9. The reinjection construction method as described in claim 4, characterized in that, Both the solid pipe section and the sedimentation pipe section are made of steel pipe; the outer wall of the filtration pipe section is wrapped with a filter screen.

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