Combined dewatering well structure located in shield interval and construction method

Abstract

The construction method comprises the following steps that a dewatering well suitable for a non-fine concrete pipe is drilled in a shield tunneling passing section, a dewatering well pump mounting section is arranged below the shield tunneling passing section, a pump mounting section drill hole is drilled in the bottom of the dewatering well, and a pump mounting section drill hole is drilled in the bottom of the dewatering well; the dewatering well pump installation section well pipe is a steel water filtering pipe, and the outer diameter of the steel water filtering pipe is smaller than the inner diameter of the non-fine concrete pipe. Manufacturing the steel water filter pipe and the well pipe connecting device; the steel water filter pipe is tripped into the pump installation section drill hole, the top of the steel water filter pipe is located above a well opening of the dewatering well, and the steel water filter pipe is connected with the well pipe connecting device; and a non-fine concrete pipe is tripped into the dewatering well, the bottom of the non-fine concrete pipe is connected with the well pipe connecting device, and follow-up construction is completed. According to the method, the dewatering well can be drilled in the shield interval, shield tunneling is not affected, and the method is suitable for shield tunnel dewatering construction of projects such as railways, subways and municipal administration.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering technology, specifically relating to a combined dewatering well structure and construction method located within a shield tunnel section. Background Technology

[0002] In underground engineering construction, groundwater control is a crucial step in ensuring the safety of foundation pit and tunnel construction, preventing surrounding rock instability, and reducing settlement and deformation. Well dewatering, due to its advantages such as large dewatering depth, stable drainage volume, and wide applicability to various geological formations, has become the mainstream dewatering technology at the starting and receiving ends of shield tunnels and when traversing water-rich strata. The well casing, as the core load-bearing and water-conducting component, directly determines the dewatering effect, construction safety, and the smoothness of subsequent shield tunneling through its material selection and structural design. Currently, the two most widely used technologies in engineering and closest to the purpose of this invention are no-fines concrete pipe dewatering well technology and steel pipe dewatering well technology.

[0003] Among them, the sand-free concrete pipe dewatering well technology is widely used in ordinary underground engineering dewatering operations due to its low cost, convenient material sourcing, and good corrosion resistance. This technology uses sand-free concrete pipes as the main body of the well, utilizing the porous structure of the pipe material to achieve groundwater infiltration and collection, and then uses a water pump to complete drainage and pressure reduction. However, in shield tunnel dewatering scenarios, this technology has significant drawbacks: the strength of sand-free concrete pipes is relatively low (compressive strength is usually only 30-50MPa). When the project is limited by site and requires the use of a "few wells, large pumps" approach, the vibration and water flow impact generated by the operation of the high-flow water pump can easily cause the well pipe in the pump section to rupture and fall off, which not only affects the continuity of dewatering but may also trigger the risk of ground subsidence.

[0004] Another mainstream technology is steel pipe dewatering well technology, which uses seamless or welded steel pipes as well casings. It boasts advantages such as high strength (compressive strength can reach over 200MPa) and strong impact resistance, making it suitable for high-flow-rate pumping and effectively avoiding well casing damage during the pumping section. However, when this technology is applied to shield tunnel sections, a core problem exists: the high hardness and wear resistance of the steel pipes cause severe wear when the cutterhead contacts the pipes during shield tunneling. This significantly shortens the service life of the cutterhead cutters (according to engineering measurements, cutterhead wear increases by 3-5 times compared to conventional strata when excavating steel pipes), and also leads to a significant decrease in tunneling speed due to uneven force on the cutterhead (the average tunneling speed can drop to less than 1 / 3 of that in conventional strata), increasing construction time and costs. Furthermore, the presence of the steel pipes can make shield machine attitude control difficult, easily causing quality hazards such as segment misalignment and tunnel displacement. Therefore, steel pipe dewatering wells are generally avoided within the shield tunnel area in engineering projects.

[0005] Patent CN115807440A discloses a combined dewatering well structure, employing sand-free concrete pipes in fine-grained soil layers and bridge-type filter pipes in coarse-grained soil layers, with different material pipes fixedly connected using clamps. The core of this patent lies in using different pipes for different geological formations. However, this technology fails to consider the differences in pipe diameter and wall thickness, leading to misalignment at connections. This can easily cause pipe blockage and pump jamming during maintenance processes such as well cleaning, pump installation, and pump replacement.

[0006] Patent CN217811142U discloses a composite dewatering well structure. This structure uses the bottom of the foundation pit as a boundary, with a concrete pipe at the bottom and a steel pipe at the top. The upper steel pipe has a joint located below the bottom of the pit. The joint includes a core tube inserted into the lower concrete pipe and a sleeve fitted over the outside of the lower concrete pipe. The top of the sleeve is concentrically connected to the upper steel pipe via a tapered tube. The core tube is formed by the tail section of the upper steel pipe, and the tapered tube is filled with a sponge strip. This technology neglects the potential for pipe blockage and pump jamming during maintenance processes such as well flushing, pump installation, and pump replacement.

[0007] Patent CN106437728A discloses a combined dewatering well pipe and its installation method for use in shield tunneling sections. The dewatering well pipe in the depth area where the shield machine is advancing is made of fiberglass, while a steel pipe is used in the non-shield machine advancing area. The steel pipe and the fiberglass well pipe are connected by flanges. The fiberglass well pipe used in this patent is not commonly used in dewatering construction and is relatively expensive, generally 2 to 3 times the price of no-fines concrete pipe.

[0008] In summary, existing dewatering well technologies are unable to adequately meet the core requirements of dewatering scenarios in shield tunneling sections, namely, simultaneously satisfying dewatering stability, well casing structural strength, and shield tunneling compatibility. With the increasing number of urban shield tunnel projects and the increasingly stringent constraints imposed on construction sites by surrounding buildings and underground pipelines, the conflict between the placement of dewatering wells and the materials used for the casings is becoming increasingly prominent. Therefore, a new type of dewatering well structure is urgently needed to solve these technical problems and achieve safe placement and efficient operation of dewatering wells within shield tunneling sections. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a combined dewatering well structure and construction method located within the shield tunnel section. This is a technical means applicable to dewatering of shield tunnels in railway, subway, and municipal engineering projects. It enables the installation of dewatering wells within the shield tunnel section without affecting the shield tunnel excavation.

[0010] This invention achieves this objective through the following technical solution: A construction method for a combined dewatering well located within a shield tunnel section includes the following steps: Dewatering wells suitable for sand-free concrete pipes are installed in the shield tunneling section. The pump installation section of the dewatering well is set below the shield tunneling section. A pump installation section borehole is drilled at the bottom of the dewatering well. The well pipe of the pump installation section of the dewatering well is a steel filter pipe, and the outer diameter of the steel filter pipe is smaller than the inner diameter of the sand-free concrete pipe. Fabricate the steel filter pipe and well pipe connection device; The steel filter pipe is lowered into the borehole of the pump section, with its top positioned above the bottom of the dewatering well and connected to the well pipe connection device. The sand-free concrete pipe is lowered into the dewatering well, and its bottom is connected to the well pipe connection device to complete the subsequent construction.

[0011] Furthermore, the well casing connection device includes an outer steel pipe, an inner steel pipe, and an annular steel plate; The inner diameter of the outer steel pipe is larger than the outer diameter of the sand-free concrete pipe, and its length is smaller than the length of the inner steel pipe. The outer diameter and wall thickness of the inner steel pipe are the same as those of the steel filter pipe, but the outer diameter is smaller than the inner diameter of the sand-free concrete pipe. The diameter of the annular steel plate is the same as the outer diameter of the outer steel pipe, and the diameter of the concentric holes inside is the same as the outer diameter of the inner steel pipe. The outer steel pipe and the inner steel pipe are welded to the annular steel plate to form an annular groove structure. The sand-free concrete pipe is installed in the annular groove, and the lower end of the inner steel pipe is welded to the upper end of the steel filter pipe.

[0012] Furthermore, several triangular steel ribs are evenly arranged around the bottom of the annular steel plate. One side of each triangular steel rib is welded to the bottom of the annular steel plate, and the other side is welded to the outer wall of the inner steel pipe.

[0013] Furthermore, the upper end of the inner steel pipe is processed into a flared structure, with the flared opening being outward-opening and the outer diameter of the flared opening being smaller than the inner diameter of the sand-free concrete pipe.

[0014] Furthermore, the upper end of the welded inner steel pipe is higher than the upper end of the outer steel pipe.

[0015] Furthermore, after the well pipe connection device is welded to the steel filter pipe, asphalt is poured into the annular groove formed by the outer steel pipe, the inner steel pipe, and the annular steel plate. Before the asphalt solidifies, the sand-free concrete pipe is inserted into the annular groove, and the overflowing asphalt is removed in time to prevent it from flowing into the dewatering well and clogging the filter.

[0016] Furthermore, the height of the poured asphalt liquid is between 1 / 3 and 1 / 2 of the depth of the annular groove.

[0017] Furthermore, the steel filter pipe is lowered into the borehole using a tray method.

[0018] The present invention also provides a combined dewatering well structure located within the shield tunnel section, which is constructed using the method described above.

[0019] Compared with the prior art, the beneficial effects of this invention are as follows: This invention is primarily applied to dewatering operations during the construction of shield tunnels in subways, highways, and railways, and is particularly suitable for scenarios where dewatering wells need to be installed within the shield tunneling area. Its core principle is to optimize the structure and connection method of the dewatering wells to meet groundwater level control requirements and ensure dewatering stability while simultaneously considering the safety and efficiency of the shield tunneling machine. It solves the problems of material compatibility, structural reliability, and construction compatibility inherent in traditional dewatering well installations within shield tunnel sections, providing technical support for dewatering construction in shield tunnel sections under complex site conditions. The steel pipes, steel plates, and asphalt used in this invention are all commonly used materials in dewatering engineering. The device is primarily manufactured through welding, facilitating on-site operation. This invention achieves satisfactory dewatering stability, well structural strength, and shield tunneling compatibility, while the connecting device ensures the stability of connections between wells of different materials, ease of installation, and convenience of pump maintenance. It also improves production efficiency, reduces safety risks, and lowers overall costs, thus achieving a safe and economical outcome. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a precipitation well according to an embodiment of the present invention; Figure 2 This is a cross-sectional schematic diagram of the well pipe connection device according to an embodiment of the present invention; Figure 3 This is a schematic cross-sectional view of the connection position of the dewatering well structure in an embodiment of the present invention; Figure 4 This is a top view of the well pipe connection device according to an embodiment of the present invention; Figure 5 This is a bottom view of the well pipe connection device according to an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the manufacturing process of the well pipe connection device according to an embodiment of the present invention.

[0021] The attached diagram is labeled as follows: 1-Steel filter pipe, 2-Sand-free concrete pipe, 3-Well pipe connection device, 4-Outer steel pipe, 5-Inner steel pipe, 6-Annular steel plate, 7-Triangular steel rib plate, 8-Asphalt, 9-Flare structure. Detailed Implementation

[0022] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] An embodiment of the present invention discloses a dewatering well structure and construction method suitable for installation within a shield tunnel section. The well structure is shown in the attached diagram. Figure 1 As shown: The dewatering well pumping section is located below the shield tunnel section. The well pipe of the dewatering well pumping section adopts a steel filter pipe 1, and the well pipe of the shield tunneling section adopts a sand-free concrete pipe 2. The steel filter pipe 1 and the sand-free concrete pipe 2 are connected by a well pipe connection device 3, which takes into account the stability of the well pipe connection, the convenience of manufacturing and installation, and the convenience of pump maintenance.

[0024] Well casing connection device 3, such as Figure 2 As shown, it includes an outer steel pipe 4, an inner steel pipe 5, an annular steel plate 6, and a triangular steel rib plate 7.

[0025] The inner diameter of the outer steel pipe 4 is larger than the outer diameter of the sand-free concrete pipe 2.

[0026] The outer diameter and wall thickness of the inner steel pipe 5 are the same as those of the steel filter pipe 1, but the outer diameter is smaller than the inner diameter of the sand-free concrete pipe 2. The upper end of the pipe body is processed into a flared structure 9, with the flared opening being outward-opening. The outer diameter of the flared opening should be smaller than the inner diameter of the sand-free concrete pipe 2. The upper height of the outer steel pipe 4 does not exceed the bottom of the flared structure 9 of the inner steel pipe 5, and the transition between different well diameters is smooth, making it less likely to cause pipe blockage or pump jamming during well washing and pump installation and maintenance.

[0027] The diameter of the annular steel plate 6 is the same as the outer diameter of the outer steel pipe 4, and the diameter of the concentric holes inside is the same as the outer diameter of the inner steel pipe 5.

[0028] The outer steel pipe 4 and the inner steel pipe 5 are welded to the annular steel plate 6 to form an annular groove structure.

[0029] The overall structural construction process is as follows: S1: Install dewatering wells suitable for sand-free concrete pipe 2 in the shield tunneling section.

[0030] S2: The pumping section of the dewatering well is set below the shield tunneling section, and a pumping section borehole is drilled at the bottom of the dewatering well.

[0031] S3: Fabricate and weld steel filter pipe 1.

[0032] S4: Fabricate well pipe connection device 3.

[0033] S5: The steel filter pipe 1 is lowered into the borehole in the dewatering well using the tray method, with the upper end above the bottom surface of the dewatering well.

[0034] S6: Weld the bottom of the inner steel pipe 5 in the well pipe connecting device 3 to the upper end of the steel filter pipe 1 concentrically to ensure that the axes of the two coincide and the welding surfaces fit tightly, and fully weld along the circumferential direction of the joint.

[0035] S7: In the well casing connection device 3, asphalt 8 is poured into the annular groove formed by the outer steel pipe 4, the inner steel pipe 5, and the annular steel plate 6. The liquid level is between 1 / 3 and 1 / 2 of the depth of the annular groove. Pouring asphalt 8 into the annular groove formed by the annular steel plate 6 provides a flexible seal at the connection, enhances the stability of the connection, and prevents mud, filter media, etc. from entering the well casing.

[0036] S8: Before the asphalt 8 solidifies, quickly insert the sand-free concrete pipe 2 into the groove and remove any overflowing asphalt 8 in time to prevent it from flowing into the dewatering well and clogging the filter. The flared structure 9, which is higher than the upper end of the outer steel pipe 4, can prevent asphalt 8 from being squeezed into the well pipe during the installation of the sand-free concrete pipe 2.

[0037] S9: Continue with subsequent well casing installation work.

[0038] The manufacturing steps for well casing connection device 3 are as follows: S4.1: The top part of the inner steel pipe 5 is made into an outwardly flared structure 9, see [reference]. Figure 6 (a).

[0039] S4.2: Concentrically attach the annular steel plate 6 to the outside of the inner steel pipe 5, ensuring that the plane of the annular steel plate 6 is perpendicular to the axis of the inner steel pipe 5. Perform concentric circumferential full welding along the attachment point. See [link to documentation]. Figure 6 (b).

[0040] S4.3: Arrange the triangular steel ribs 7 evenly at equal intervals around the axis of the inner steel pipe 5, and weld them between the lower surface of the annular steel plate 6 and the outer wall of the inner steel pipe 5, ensuring that the triangular steel ribs 7 fit tightly against both and are firmly welded. See [link to documentation]. Figure 6 (c). Welding triangular steel ribs 7 between the lower surface of the annular steel plate 6 and the outer wall of the inner steel pipe 5 can strengthen the well pipe connection device 3 and facilitate the support of the upper sand-free concrete pipe 2.

[0041] S4.4: Concentrically attach the outer steel pipe 4 to the upper surface of the annular steel plate 6, and perform concentric circumferential full welding at the attachment point. See [link / reference]. Figure 6 (d).

[0042] The present invention has been described in detail above through embodiments, but the content described is only an exemplary embodiment of the present invention and should not be considered as limiting the scope of the present invention. The scope of protection of the present invention is defined by the claims. Any technical solutions designed by those skilled in the art using the technical solutions described in the present invention, or similar technical solutions designed by those skilled in the art under the inspiration of the technical solutions of the present invention, within the substance and protection scope of the present invention, to achieve the above-mentioned technical effects, or equivalent changes and improvements made to the scope of the application, should still fall within the patent protection scope of the present invention. It should be noted that, for clarity, descriptions of some components and processes that are not directly and obviously related to the protection scope of the present invention but are known to those skilled in the art have been omitted in the description of the present invention.

Claims

1. A construction method for a combined dewatering well located within a shield tunnel section, characterized in that, Includes the following steps: Dewatering wells suitable for sand-free concrete pipes are installed in the shield tunneling section. The pump installation section of the dewatering well is set below the shield tunneling section. A pump installation section borehole is drilled at the bottom of the dewatering well. The well pipe of the pump installation section of the dewatering well is a steel filter pipe, and the outer diameter of the steel filter pipe is smaller than the inner diameter of the sand-free concrete pipe. Fabricate the steel filter pipe and well pipe connection device; The steel filter pipe is lowered into the borehole of the pump section, with its top positioned above the bottom of the dewatering well and connected to the well pipe connection device. The sand-free concrete pipe is lowered into the dewatering well, and its bottom is connected to the well pipe connection device to complete the subsequent construction.

2. The method according to claim 1, characterized in that, The well casing connection device includes an outer steel pipe, an inner steel pipe, and an annular steel plate; The inner diameter of the outer steel pipe is larger than the outer diameter of the sand-free concrete pipe, and its length is smaller than the length of the inner steel pipe. The outer diameter and wall thickness of the inner steel pipe are the same as those of the steel filter pipe, but the outer diameter is smaller than the inner diameter of the sand-free concrete pipe. The diameter of the annular steel plate is the same as the outer diameter of the outer steel pipe, and the diameter of the concentric holes inside is the same as the outer diameter of the inner steel pipe. The outer steel pipe and the inner steel pipe are welded to the annular steel plate to form an annular groove structure. The sand-free concrete pipe is installed in the annular groove, and the lower end of the inner steel pipe is welded to the upper end of the steel filter pipe.

3. The method according to claim 2, characterized in that, Several triangular steel ribs are evenly arranged around the bottom of the annular steel plate. One side of each triangular steel rib is welded to the bottom of the annular steel plate, and the other side is welded to the outer wall of the inner steel pipe.

4. The method according to claim 2, characterized in that, The upper end of the inner steel pipe is processed into a flared structure, and the flared opening is outward-opening, with the outer diameter of the flared opening being smaller than the inner diameter of the sand-free concrete pipe.

5. The method according to claim 2, characterized in that, After welding, the upper end of the inner steel pipe is higher than the upper end of the outer steel pipe.

6. The method according to claim 2, characterized in that, After the well pipe connection device is welded to the steel filter pipe, asphalt is poured into the annular groove formed by the outer steel pipe, the inner steel pipe, and the annular steel plate. Before the asphalt solidifies, the sand-free concrete pipe is inserted into the annular groove, and the overflowing asphalt is removed in time to prevent it from flowing into the dewatering well and clogging the filter.

7. The method according to claim 6, characterized in that, The height of the poured asphalt liquid is between 1 / 3 and 1 / 2 of the depth of the annular groove.

8. The method according to claim 1, characterized in that, The steel filter pipe is lowered into the borehole using a tray method.

9. A combined dewatering well structure located within a shield tunnel section, characterized in that, Construction shall be carried out using the method described in any one of claims 1-8.

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