Long-distance horizontal freezing hole structure penetrating through underground obstacles and construction method of long-distance horizontal freezing hole structure

Abstract

The invention provides a long-distance horizontal freezing hole structure capable of passing through underground obstacles and a construction method of the long-distance horizontal freezing hole structure, and provides a matched horizontal freezing hole structure and a construction method of the matched horizontal freezing hole structure aiming at a poor stratum of a water-rich sand layer and a construction pain point of a newly-built tunnel passing through an existing station. A special drilling tool is used for penetrating through obstacles such as an underground diaphragm wall and a cast-in-place pile, large-diameter freezing pipes are adopted for screw thread welding connection, and the freezing pipes are constructed in a two-way mode to be arranged in a lap-joint staggered-layer mode and supplemented with retesting and deviation rectifying. The problems of long-distance hole forming deflection, high construction risk, poor frozen body forming and the like are solved, it is guaranteed that the frozen hole smoothly penetrates through obstacles, the frozen wall is accurately crossed and formed, a safe space is provided for manual obstacle removing work, and meanwhile the construction requirements of similar horizontal drilling engineering are met.

Description

Technical Field

[0001] This application belongs to the field of tunnel engineering technology and relates to a horizontal freezing hole structure and construction method. Background Technology

[0002] With the continuous updating of urban rail transit network planning, some underground stations constructed in the early stages did not reserve conditions for the construction of subsequent lines, and their underground structures (retaining piles, diaphragm walls, tension piles, temporary columns, etc.) only meet their own load-bearing requirements. When a new line tunnel passes under an existing station, the above-mentioned structures need to be treated: when the diameter of the reinforcing bars is small and there are no large steel sections, the tunnel boring machine can cut through directly; when the reinforcing bars are thicker or contain large steel materials such as channel steel and H-beams, manual removal is required. For unfavorable strata such as water-rich sand layers, due to their poor stability and susceptibility to water and sand inrush, conventional advanced pre-reinforcement measures cannot guarantee construction safety, and horizontal freezing methods are required to provide safe working space for manual obstacle removal. Whether long-distance horizontal freezing holes can successfully pass through obstacles such as diaphragm walls and bored piles is the key to achieving the connection of freezing holes and forming a frozen body. When constructing long-distance horizontal freezing hole structures that traverse underground obstacles, the quality of the freezing holes directly determines the freezing effect and project safety. However, there is currently a lack of horizontal freezing hole construction technology that can successfully traverse long-distance obstacles such as diaphragm walls and bored piles. Summary of the Invention

[0003] To address the problem mentioned in the background art of lacking construction technology for horizontal freezing holes that can smoothly pass through long-distance obstacles such as diaphragm walls and bored piles, this invention provides a long-distance horizontal freezing hole structure and its construction method for passing through underground obstacles, ensuring that the horizontal freezing hole can smoothly pass through existing long-distance underground obstacles such as diaphragm walls and bored piles, and ensuring construction and personnel safety.

[0004] In a first aspect, the present invention provides a construction method for a long-distance horizontal freezing hole structure that traverses underground obstacles, comprising the following steps: S1. Construction preparation: Construct clearing wells on both sides of the existing underground station to provide working space for subsequent bidirectional horizontal freezing drilling. S2. Construction of guide positioning sleeve: Install orifice pipes and sealing devices in each clearing well. Use a drill bit and core tube to drill the guide hole. After passing through the underground continuous wall of the clearing well and the underground continuous wall under the existing station in sequence, put seamless steel pipe into the guide hole as a guide positioning sleeve. S3. Drilling through underground obstacles: Inside the guide positioning sleeve, an industrial drill rod is used in conjunction with a composite drill bit or an oil drill bit to drill through underground obstacles, including diaphragm walls and bored piles. After completing the drilling of the freezing holes in the obstacle section, the drill rod is pulled out. S4. Lowering the freezing pipe: Lower the freezing pipe along the borehole to the designed position. After the freezing pipe reaches the designed depth, flush the one-way valve and seal the end of the freezing pipe. S5. Re-measurement and correction: Re-measure the depth, angle and inclination of the borehole. If deviations are found, correct them in time. If necessary, add freezing holes at adjacent positions to ensure that the freezing holes are connected smoothly to ensure the thickness of the frozen wall. S6. Start construction of freezing holes from the clearing wells on both sides of the existing underground station according to steps S2 to S5. The freezing pipes constructed in both directions overlap in the middle to form a continuous horizontal freezing body.

[0005] Furthermore, in step S2, a D152 drill bit is used in conjunction with a D146 core tube to drill the pilot hole, and the lowered guide positioning sleeve is a seamless steel pipe of D146×8.

[0006] Furthermore, in step S3, when the drill rod contacts the underground obstacle, the drilling rig maintains a low speed and slow advance state. During the hole opening stage, the speed is 20-40 r / min and the feed rate is 0.1-0.2 m / r to ensure that the drill rod is concentric.

[0007] Furthermore, in step S3, water is used for drilling and the bypass valve is closed; when drilling is difficult, bentonite is used to prepare drilling mud.

[0008] Furthermore, the freezing tube is made of D108×10mm seamless steel pipe.

[0009] Furthermore, the longitudinal connections between the freezing pipes are achieved by using threaded sleeve connections followed by manual arc welding. Horizontal freezing pipes are connected using internal clamps, aligned, and then welded by manual arc welding. This improves the reliability of the freezing pipe joint connections: the longitudinal splicing of the freezing pipes employs a dual connection process combining threaded sleeve connections and manual arc welding. Based on the mechanical principles of pipe connections, the threaded sleeve connections ensure concentricity at the joint, preventing misalignment or eccentricity issues in the spliced ​​sections. Simultaneously, the manual arc welding enhances the welding strength of the joint. This dual reinforcement effectively prevents pipe breakage and leakage during drilling and freezing operation of multi-segment spliced ​​freezing pipes, ensuring the airtightness and structural stability of the freezing pipeline.

[0010] Furthermore, in step S6, the overlap length of the freezing pipe in the middle section of the bidirectional construction is not less than 2m, and the overlap parts are staggered vertically and horizontally in the cross-sectional direction.

[0011] Furthermore, the drilling construction follows a bottom-up, inside-out sequence, with the freezing holes that penetrate the diaphragm wall or bored piles being constructed first.

[0012] Furthermore, during the drilling process, a bypass valve installed at the borehole pipe is used to perform a grouting operation on the soil.

[0013] Secondly, based on the above construction method, the present invention provides a long-distance horizontal freezing hole structure that passes through underground obstacles, including clearing wells respectively set on both sides of the existing underground station, and a number of horizontal freezing holes that start from each clearing well and pass through the underground obstacles.

[0014] Each of the horizontal freezing holes includes: A guide and positioning sleeve is installed between the underground continuous wall of the obstacle clearing well and the underground continuous wall of the existing underground station to guide the subsequent drilling direction; a freezing pipe passes through the underground obstacle and extends to the designed position under the guidance of the guide and positioning sleeve. The diameter of the freezing pipe is larger than that of a conventional freezing pipe, and the freezing pipes are longitudinally connected by a sleeve thread welding method.

[0015] Among them, the freezing pipes starting from the clearing wells on both sides of the existing underground station are overlapped in the middle and arranged in staggered layers in the upper, lower and left and right directions to form a continuous horizontal freezing body.

[0016] Compared with the prior art, this application has the following advantages: (1) Reduce the difficulty and risk of long-distance drilling: Based on the layout of clearing wells on both sides of the existing underground station, the mode of bidirectional synchronous construction of freezing holes is adopted. Compared with the traditional unidirectional long-distance drilling, the drilling length of a single freezing pipe through underground obstacles is reduced from the root, and the construction journey of a single drilling is greatly reduced. This reduces the risk of stuck drill, deviated hole, water inrush and sand inrush during long-distance drilling. It solves the problem of high difficulty and prominent safety hazards in long-distance horizontal drilling in poor strata and is suitable for construction conditions of poorly stable strata such as water-rich sand layers. (2) Improve the quality of frozen holes: By constructing a guide and positioning casing in advance, the directional guidance of the casing provides a precise path for subsequent freezing pipe drilling. By clearing the obstruction well, a standardized working space is provided. With the help of the orifice pipe and sealing device, the drilling is accurately positioned in the early stage of drilling. The drilling direction is strictly controlled with the guide and positioning casing. The drilling depth, angle and inclination deviations are corrected in time through the re-measurement and correction process. The accuracy of hole formation is controlled throughout the entire process of positioning, drilling and re-measurement, which greatly improves the quality of long-distance horizontal frozen holes and avoids the effect of subsequent frozen wall formation due to hole formation defects. (3) Improve the structural stability of the freezing pipe: Conventional freezing pipes have a small diameter and a single connection method. Long-distance deployment is prone to structural loosening and sealing failure, which affects the delivery of freezing medium and freezing effect. This patent uses freezing pipes with a diameter larger than conventional specifications, and a longitudinal connection method of sleeve thread welding. This not only improves the structural strength of the freezing pipe itself, but also ensures the sealing and stability of the pipe connection, which is suitable for long-distance drilling deployment. At the same time, the overlapping and staggered layout of the freezing pipes further optimizes the thickness and uniformity of the freezing wall, avoids local weakness of the freezing wall, ensures the long-term stability of the freezing structure, and meets the stress and safety requirements of subsequent obstacle removal and tunnel construction. (4) Improve construction safety: Water-rich sand layers have poor stability and are prone to water and sand inrush accidents. Manual clearing operations need to rely on a complete and continuous frozen wall to provide a safe space. However, if the freezing holes cannot be connected, gaps will be directly caused in the frozen wall, leading to safety hazards. This patent adopts a two-way drilling construction process, and freezing holes are constructed simultaneously from the clearing wells on both sides of the existing station. The freezing pipes on both sides are overlapped and staggered in the middle part. With the addition of supplementary holes to correct deviation, it is ensured that each freezing hole is effectively connected and smoothly connected to form a continuous closed horizontal frozen body, which isolates the water and sand inrush channels of the water-rich sand layer. This provides a safe working space for manual removal of underground structures such as thick steel bars and large steel sections, and greatly improves the safety of construction under adverse strata. (5) Adaptable to complex construction scenarios: In response to complex scenarios in urban rail transit where existing stations have not reserved construction conditions, underground structures are dense, and strata conditions are poor, this invention forms a complete construction process from construction preparation, guide sleeve construction, obstacle drilling to freezing pipe placement, re-measurement and correction. It is equipped with a dedicated freezing hole structure design, which can adapt to the horizontal freezing construction needs of various underground obstacles and poor strata, make up for the lack of existing long-distance horizontal freezing hole construction technology, and improve the freezing construction technology system for new urban rail transit tunnels passing under existing stations. At the same time, it can be extended to various horizontal drilling projects that require long-distance and high-precision hole formation, providing mature technical reference for similar underground engineering construction, and improving the feasibility and flexibility of engineering construction under complex underground conditions.

[0017] In summary, addressing the challenges of constructing new tunnels under existing stations in water-rich sandy strata and other difficult terrains, this invention proposes a supporting horizontal freezing borehole structure and its construction method. First, a clearing well is constructed. Then, precise guidance is achieved through a directional casing. Specialized drilling tools are used to penetrate obstacles such as diaphragm walls and cast-in-place piles. Large-diameter freezing pipes are connected by threaded welding, with overlapping and staggered layers of freezing pipes used in both directions, supplemented by re-measurement and correction. This invention overcomes the difficulties of long-distance borehole deviation, high construction risk, and poor frozen body formation. It ensures that the freezing borehole can smoothly penetrate obstacles and accurately form a frozen wall, while also providing safe space for manual clearing operations. Furthermore, it is compatible with the construction needs of similar horizontal drilling projects. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a plan view of the long-distance horizontal freezing hole structure that traverses underground obstacles provided in Embodiment 1 of this application.

[0020] Figure 2 This is a longitudinal section view of the long-distance horizontal freezing hole structure that traverses underground obstacles provided in Embodiment 1 of this application.

[0021] Figure 3 This is a cross-sectional view of the horizontally frozen obstacle clearing tunnel and underground obstacles provided in Embodiment 1 of this application.

[0022] Figure 4 This is a diagram of the horizontal drilling casing and freezing pipe blowout release device provided in Embodiment 1 of this application.

[0023] Explanation of reference numerals in the attached drawings: 1-Clearing well, 11-Clearing well diaphragm wall, 12-Clearing well inner lining wall, 2-Horizontal frozen body, 3-Horizontal freezing hole, 31-Casing, 32-Freezing pipe, 33-Bypass valve, 34-Pressure clamping device, 35-Expansion bolt, 36-Connecting steel bar, 5-New tunnel, 51-New clearing tunnel, 52-New shield tunnel, 6-Existing underground station, 61-Diaphragm wall, 62-Drilled pile, 63-Internal structure. Detailed Implementation

[0024] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0025] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0026] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0027] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0028] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0029] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0031] Ideally, horizontal freezing holes should avoid penetrating underground obstacles. However, in actual engineering projects, the route of newly constructed shield tunnels is often restricted by the surrounding environment, thus limiting the excavation of tunnels to a certain range, and consequently, the horizontal freezing body is also limited to a certain range. The successful formation of the horizontal freezing body depends on whether each horizontal freezing pipe can be successfully drilled; therefore, horizontal freezing pipes will inevitably penetrate underground obstacles such as diaphragm walls and bored piles.

[0032] Some horizontal freezing holes require a small angle of entry into the diaphragm wall or a small angle of entry into the arc surface of the bored pile. During construction, these horizontal freezing holes often deviate due to uneven stress on the drill bit (one side is the dense diaphragm wall or bored pile with a compressive strength of C30-C35, and the other side is the loose soil layer with no compressive strength under natural conditions). Alternatively, drilling may be difficult because the drill bit passes through the I-beam structure (Q235B steel plate with a thickness of about 8-12mm) or large-diameter steel bars (such as HRB400 threaded steel bars with a diameter of 32-36mm) in the diaphragm wall. In addition, when constructing horizontal freezing holes, the horizontal drill rod tends to sag under its own weight. The longer the hole, the greater the deviation at the end. Therefore, corresponding measures need to be taken to ensure that the horizontal freezing holes are successfully and accurately constructed according to the design requirements.

[0033] Example 1 This embodiment provides a construction method for long-distance horizontal freezing hole structures that traverse underground obstacles, and the construction process is combined with... Figure 1 - Figure 4 The core of the project is to solve the problems of deviation and hole formation difficulties when the horizontal frozen hole 3 passes through obstacles such as the underground continuous wall 61 and the bored pile 62 by means of two-way construction, precise guidance and step-by-step drilling. At the same time, it controls the end deviation of long-distance drilling to ensure the continuous formation of the horizontal frozen body 2, and provides safe surrounding rock conditions for the excavation of the new tunnel 5. The specific steps are as follows.

[0034] S1. Construction preparation: Construct clearing wells 1 on both sides of the existing underground station 6 to provide working space for subsequent bidirectional horizontal freezing drilling. Specifically, clearing wells 1 are constructed on both sides of the existing underground station 6. Each clearing well 1 is equipped with a diaphragm wall 11 and an inner lining wall 12, providing ample working space for subsequent bidirectional horizontal freezing drilling. This bidirectional construction mode fundamentally reduces the risk of the freezing pipe repeatedly crossing underground obstacles during unidirectional construction, and reduces the length and difficulty of drilling on one side. This construction layout revolves around the planned route of the new tunnel 5, precisely matching the construction scope of the new clearing tunnel 51 and the new shield tunnel 52.

[0035] S2. Construction of guide positioning sleeve: Install orifice pipes and sealing devices in each clearing well. Use a drill bit and core tube to drill the guide hole. After passing through the underground continuous wall 11 of the clearing well and the underground continuous wall 61 below the existing underground station 6 in sequence, put the seamless steel pipe into the guide hole as the guide positioning sleeve 31. Specifically, orifice pipes and sealing devices are installed in each clearing well. A D152 drill bit is used in conjunction with a D146 core tube to drill pilot holes. After the pilot holes pass through the underground continuous wall 11 of the clearing well and the underground continuous wall 61 below the existing underground station 6, a D146×8 seamless steel pipe is lowered into the pilot hole as a guide and positioning sleeve 31 to provide precise drilling direction guidance for subsequent long-distance freezing hole construction. The axis of the guide and positioning is consistent with the design axis of the new tunnel 5 to ensure that the horizontal frozen body 2 fits the excavation outline of the new tunnel 5.

[0036] S3. Drilling through underground obstacles: Inside the guide positioning sleeve 31, an industrial drill rod is used in conjunction with a composite drill bit or an oil drill bit to drill through underground obstacles including the underground continuous wall 61 and the bored pile 62. After completing the drilling work of the freezing hole 3 in the obstacle section, the drill rod is pulled out. Specifically, within the guide and positioning casing 31, industrial drill rods are used in conjunction with high-strength D120 composite drill bits or oilfield drill bits to drill through underground obstacles such as the diaphragm wall 61 and bored piles 62. When the drill rod contacts the obstacle, the drilling rig maintains a low speed and slow advance, with the speed controlled at 20-40 r / min and the feed rate at 0.1-0.2 m / r during the hole-opening stage to ensure consistent drill rod concentricity and avoid drill bit swaying or getting stuck due to diameter reduction. During drilling, clean water is used first, and the bypass valve 33 is closed to reduce soil erosion. If drilling becomes difficult, bentonite-modified mud drilling is switched to. When the advance is slow or the drilling rig has no torque, the drill bit is replaced in time until the drilling of the freezing hole 3 in the obstacle section is completed, after which the drill rod is pulled out. This drilling section is the core construction area of ​​the newly built obstacle-clearing tunnel 51 and a key node connecting the newly built shield tunnel 52 and the existing underground station 6.

[0037] S4. Lowering the freezing tube 32: Lower the freezing tube 32 along the borehole to the designed position. After the freezing tube 32 reaches the designed depth, flush the one-way valve and seal the end of the freezing tube 32. Specifically, the freezing pipe 32 is made of D108×10mm seamless steel pipe and is lowered along the borehole to the designed position. The lowering depth matches the excavation length of the new tunnel 5 to ensure that the frozen body covers the entire section of the new obstacle clearing tunnel 51 and the connection section between the new shield tunnel 52 and the obstacle clearing tunnel. After the freezing pipe 32 reaches the designed depth, the one-way valve is flushed in time, and the end of the freezing pipe 32 is sealed to prevent grout leakage and cold runoff during subsequent construction.

[0038] S5. Re-measurement and correction: Re-measure the depth, angle and inclination of the borehole. If deviations are found, correct them in time. If necessary, add freezing holes 3 at adjacent positions to ensure that each freezing hole 3 can be smoothly connected to ensure the thickness of the frozen wall. Specifically, the depth, angle, and inclination of the boreholes were comprehensively remeasured using a theodolite for inclination measurement, and any deviations were corrected promptly. After the freezing pipes were installed, the length of the freezing pipes 32 was remeasured, and the inclination was measured again using a light inclinometer to draw a borehole deviation diagram. If the borehole position was deviated or the borehole spacing did not meet the design requirements, additional freezing holes 3 were added at adjacent locations to ensure that all freezing holes 3 could be smoothly connected and that the thickness of the frozen wall met the standard. The design thickness of the frozen wall was determined based on the excavation cross-sectional dimensions and surrounding rock conditions of the newly constructed obstacle-clearing tunnel 51 and the newly constructed shield tunnel 52, meeting the requirements for collapse resistance and seepage prevention during tunnel excavation.

[0039] S6. Construction of freezing holes from the clearing wells 1 on both sides of the existing underground station 6 in accordance with steps S2 to S5. The freezing pipes 32 constructed in both directions overlap at the middle part to form a continuous horizontal freezing body 2.

[0040] Specifically, freezing holes are constructed from the clearing wells 1 on both sides of the existing underground station 6 according to steps S2 to S5. The freezing pipes 32 constructed in both directions overlap in the middle, with an overlap length of not less than 2m. The overlap parts are staggered vertically and horizontally in the cross-sectional direction, ultimately forming a continuous horizontal frozen body 2. This horizontal frozen body 2 is formed along the designed route of the new tunnel 5, completely enclosing the excavation area of ​​the new clearing tunnel 51, and seamlessly connecting with the starting section of the new shield tunnel 52. This provides a safe construction environment for the subsequent tunneling construction of the new clearing tunnel 51 and the shield tunneling of the new shield tunnel 52, effectively isolating underground obstacles from the tunnel excavation face and preventing water inrush, soil inrush, and surrounding rock collapse during the excavation process.

[0041] In step S2 of the actual construction, a D152 drill bit is used in conjunction with a D146 core tube to drill the pilot hole, and the lowered guide positioning sleeve 31 is a seamless steel pipe of D146×8.

[0042] In step S3 of the actual construction, when the drill rod contacts the underground obstacle, the drilling rig maintains a low speed and slow advance. During the hole opening stage, the speed is 20-40 r / min and the feed rate is 0.1-0.2 m / r to ensure consistent drill rod concentricity. Water is used for drilling and the bypass valve 33 is closed. When drilling is difficult, bentonite-modified drilling mud is used.

[0043] In actual construction, the freezing pipe 32 uses D108×10mm seamless steel pipe.

[0044] In actual construction, the longitudinal connection between the freezing pipes 32 is made by connecting the sleeve thread and then welding by manual arc welding. The horizontal freezing pipes 32 are connected by inner pipe clamps and then aligned before being welded by manual arc welding.

[0045] In step S6 of the actual construction, the overlap length of the freezing pipe 32 in the middle part of the bidirectional construction shall not be less than 2m, and the overlap parts shall be staggered in the cross-sectional direction, both vertically and horizontally.

[0046] In actual construction, drilling follows a bottom-up, inside-out sequence, with the freezing holes 3 that penetrate the diaphragm wall 61 or the bored piles 62 being constructed first.

[0047] During the actual drilling process, the bypass valve 33 installed at the borehole pipe is used to perform grouting on the soil.

[0048] The following points should be noted regarding the above construction methods: Drilling sequence: Follow the bottom-up and inside-out drilling sequence, and prioritize drilling the freezing holes 3 that pass through the diaphragm wall 61 or the bored piles 62. First, verify the stability of the drill bit construction, and replace it in time if problems occur. Provide parameter reference for subsequent drilling. The drilling range strictly matches the excavation cross section of the newly built obstacle clearing tunnel 51, and takes into account the connection requirements of the newly built shield tunnel 52.

[0049] Drilling rig and supporting equipment: MD-120A drilling rig is selected, equipped with BW250 mud pump; under the protection of guide positioning sleeve 31, D108×10mm freezing pipe is used directly as drill rod to ensure drill rod rigidity, control the deviation at the end of long-distance drilling, and ensure that the axis of freezing hole coincides with the design axis of the new tunnel 5.

[0050] Orifice sealing and anti-blowout: Each horizontal freezing hole 3 is equipped with an anti-blowout device. The sealing device of the orifice pipe includes a clamping device 34, which is fixed to the inner lining wall 12 of the clearing well by expansion bolts 35 and connecting steel bars 36. After the freezing pipe 32 is inserted into the sealing device, the bolts are tightened to achieve a seal. Then the large ball valve of the orifice pipe is opened to start drilling, which effectively prevents water and soil in the hole from spraying out under water pressure and avoids disturbing the surrounding rock in the construction area of ​​the new tunnel 5.

[0051] Soil and water loss and grouting: If soil and water loss occurs during drilling, grouting will be carried out on the soil in a timely manner through the bypass valve 33 at the borehole pipe according to the daily monitoring data. The grouting will be mainly single liquid grout to control the impact of drilling on the settlement of the existing station floor and the surrounding environment, while ensuring the stability of the soil around the new tunnel 5 and avoiding the impact of soil settlement on the subsequent construction of the tunnel.

[0052] For the 32 frozen pipe joint treatment: longitudinal connections are made using sleeve thread connection + manual arc welding, and horizontal connections are made using inner pipe clamp connection for alignment + manual arc welding to ensure concentricity, horizontal and verticality and welding strength of the joints; when multiple connections are required due to the limited working space of the clearing well (longitudinal length is only 4-5m), the construction quality of each joint must be strictly controlled to prevent pipe breakage.

[0053] Key and difficult points control: The small-angle crossing of the frozen pipe 32 through underground obstacles is a key and difficult point in the construction. This crossing section is located in the core construction area of ​​the newly built obstacle clearing tunnel 51. Before construction, a special plan was formulated, and the reliability of the plan was verified by trial drilling and construction parameters were summarized to ensure the accuracy and quality of the crossing. During the drilling process, the borehole inclination was monitored throughout to ensure the quality of the frozen hole and lay the foundation for the formation of the frozen body.

[0054] Piping and drilling of freezing pipe: The piping of freezing pipe 32 is reasonably selected based on the geological interaction; a four-wing alloy drill bit is used during the normal drilling stage (specific parameters are determined through test holes); after freezing pipe 32 is lowered to the design depth, a liquid supply pipe is lowered inside the pipe, and end caps and return and return horns are welded to ensure the cooling effect of brine circulation and quickly form a horizontal frozen body 2 that meets the requirements of tunnel excavation.

[0055] Example 2 Based on the construction method of Embodiment 1, a long-distance horizontal freezing hole structure for traversing underground obstacles is provided. This structure is suitable for the restricted construction environment around existing underground stations and can achieve precise passage of long-distance horizontal freezing holes 3 through obstacles such as underground continuous walls 61 and bored piles 62, forming a continuous and stable horizontal frozen body 2. This provides reliable surrounding rock protection for the construction of the new tunnel 5. The new tunnel 5 includes two parts: a new obstacle clearing tunnel 51 and a new shield tunnel 52. The new obstacle clearing tunnel 51 is the cut-and-cover construction section and is the core section for traversing underground obstacles. The new shield tunnel 52 is the shield construction section and is seamlessly connected to the new obstacle clearing tunnel 51, realizing the connection between the existing underground station 6 and the external line.

[0056] The long-distance horizontal freezing hole structure of this embodiment includes clearing wells 1 respectively set on both sides of the existing underground station 6, and several horizontal freezing holes 3 that start from each clearing well 1 and pass through underground obstacles.

[0057] Clearing well 1: Clearing well 1 is set on both sides of the existing underground station 6 to serve as the working foundation for bidirectional horizontal freezing boreholes. Clearing well 1 includes a clearing well underground continuous wall 11 and a clearing well inner lining wall 12, and has sufficient structural strength and working space. The layout of clearing well 1 corresponds to the end of the newly built clearing tunnel 51, providing the starting point for tunnel excavation.

[0058] Horizontal freezing holes 3: Several horizontal freezing holes 3 are set out from each clearing well 1. Each horizontal freezing hole 3 includes two core components: a guide positioning sleeve 31 and a freezing pipe 32.

[0059] The functions and specifications of each component of the horizontal freezing hole 3 are as follows: Guide positioning sleeve 31: Installed between the diaphragm wall 11 of the clearing well and the diaphragm wall 61 of the existing underground station 6, it is made of seamless steel pipe with diameter D146×8. Its core function is to guide the drilling direction of the subsequent freezing pipe, control the initial deviation of the borehole, and provide precise guidance for long-distance drilling. Its layout axis is consistent with the design axis of the newly built clearing tunnel 51 to ensure that the frozen body conforms to the tunnel excavation outline.

[0060] Freezing pipe 32: Guided by the guide positioning sleeve 31, it passes through underground obstacles such as the diaphragm wall 61 and the bored pile 62 and extends to the designed position. The deployment range covers the entire section of the newly built obstacle clearing tunnel 51 and the connection section with the newly built shield tunnel 52. To ensure rigidity and strength, D108×10mm seamless steel pipe (diameter larger than conventional freezing pipe) is selected, which can effectively avoid pipe breakage during hole formation and subsequent excavation. The longitudinal connection between freezing pipes 32 adopts the sleeve thread combined with manual electric arc welding to ensure the connection strength and concentricity of the interface.

[0061] The freezing pipes 32, originating from the clearing manholes 1 on both sides of the existing underground station 6, are arranged in a staggered manner with front-to-back overlaps and vertical and horizontal layers in the middle section. The front-to-back overlap length is not less than 2m. The staggered arrangement avoids the overlap sections being concentrated on the same excavation cross section of the clearing tunnel, solves the problem of insufficient brine circulation temperature at the tail of the freezing pipe, and ensures the freezing quality of the overlap section. Finally, all the freezing pipes 32 form a continuous and complete horizontal frozen body 2. This horizontal frozen body 2 is formed along the designed route of the new tunnel 5 and serves as the core protective structure for the underground excavation of the new clearing tunnel 51. It can effectively reinforce the surrounding rock, block groundwater, and prevent problems such as water and soil inrush and surrounding rock collapse during excavation. At the same time, the end of the horizontal frozen body 2 connects with the starting section of the new shield tunnel 52, providing stable operating conditions for the shield machine to start and ensuring the smooth progress of subsequent construction of the new shield tunnel 52.

[0062] The horizontal freezing body 2 in this structure provides pre-construction protection for the construction of the new tunnel 5. The new obstacle-clearing tunnel 51 is a mined section that passes through underground obstacles. Relying on the protection of the horizontal freezing body 2, the tunnel excavation in the obstacle area, such as the diaphragm wall 61 and the bored pile 62, is completed. The new shield tunnel 52 is the subsequent shield construction section. It is seamlessly connected with the new obstacle-clearing tunnel 51 within the protection range of the horizontal freezing body 2 to form a complete new tunnel 5 line, realizing the connection between the existing underground station 6 and the external rail transit line. The layout of the horizontal freezing hole 3 structure is carried out entirely around the design outline and construction requirements of the new obstacle-clearing tunnel 51 and the new shield tunnel 52, ensuring that the protection range of the horizontal freezing body 2 is highly matched with the tunnel construction range.

[0063] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A construction method for long-distance horizontal freezing hole structures that traverse underground obstacles, characterized in that, Includes the following steps: S1. Construction preparation: Construct clearing wells on both sides of the existing underground station to provide working space for subsequent bidirectional horizontal freezing drilling. S2. Construction of guide positioning sleeve: Install orifice pipes and sealing devices in each clearing well. Use a drill bit and core tube to drill the guide hole. After passing through the underground continuous wall of the clearing well and the underground continuous wall under the existing station in sequence, put seamless steel pipe into the guide hole as a guide positioning sleeve. S3. Drilling through underground obstacles: Inside the guide positioning sleeve, an industrial drill rod is used in conjunction with a composite drill bit or an oil drill bit to drill through underground obstacles, including diaphragm walls and bored piles. After completing the drilling of the freezing holes in the obstacle section, the drill rod is pulled out. S4. Lowering the freezing pipe: Lower the freezing pipe along the borehole to the designed position. After the freezing pipe reaches the designed depth, flush the one-way valve and seal the end of the freezing pipe. S5. Re-measurement and correction: Re-measure the depth, angle and inclination of the borehole. If deviations are found, correct them in time. If necessary, add freezing holes at adjacent positions to ensure that the freezing holes can be connected smoothly to ensure the thickness of the frozen wall. S6. Start construction of freezing holes from the clearing wells on both sides of the existing underground station according to steps S2 to S5. The freezing pipes constructed in both directions overlap in the middle to form a continuous horizontal freezing body.

2. The construction method for a long-distance horizontal freezing hole structure traversing underground obstacles according to claim 1, characterized in that: In step S2, a D152 drill bit is used in conjunction with a D146 core tube to drill the pilot hole, and the lowered guide positioning sleeve is a seamless steel pipe of D146×8.

3. The construction method for a long-distance horizontal freezing hole structure traversing underground obstacles according to claim 1, characterized in that: In step S3, when the drill rod contacts the underground obstacle, the drilling rig maintains a low speed and slow advance state. During the hole opening stage, the speed is 20-40 r / min and the feed rate is 0.1-0.2 m / r to ensure that the drill rod is concentric.

4. The construction method for a long-distance horizontal freezing hole structure traversing underground obstacles according to claim 3, characterized in that: In step S3, water is used for drilling and the bypass valve is closed; when drilling is difficult, bentonite is used to prepare drilling mud.

5. The construction method for a long-distance horizontal freezing hole structure traversing underground obstacles according to claim 2, characterized in that: The freezing pipe is made of D108×10mm seamless steel pipe.

6. The construction method for a long-distance horizontal freezing hole structure traversing underground obstacles according to any one of claims 1, characterized in that: The longitudinal connection between the freezing pipes is made by connecting the sleeve thread and then welding by manual arc welding. The horizontal freezing pipes are connected by the inner pipe clamp and then aligned before being welded by manual arc welding.

7. The construction method for a long-distance horizontal freezing hole structure traversing underground obstacles according to claim 6, characterized in that: In step S6, the overlap length of the freezing pipe in the middle part of the bidirectional construction is not less than 2m, and the overlap parts are staggered vertically and horizontally in the cross-sectional direction.

8. The construction method for a long-distance horizontal freezing hole structure traversing underground obstacles according to claim 1, characterized in that: The drilling construction follows a bottom-up, inside-out sequence, with the freezing holes that penetrate the diaphragm wall or bored piles being constructed first.

9. The construction method for a long-distance horizontal freezing hole structure traversing underground obstacles according to claim 1, characterized in that: During the drilling process, a bypass valve installed at the borehole opening is used to apply grout to the soil.

10. A long-distance horizontal freezing hole structure traversing underground obstacles, obtained by the construction method according to any one of claims 1-9, characterized in that: This includes clearing wells located on both sides of the existing underground station, as well as several horizontal freezing holes that extend from each clearing well and pass through underground obstacles; Each of the horizontal freezing holes includes: The guide and positioning sleeve is installed between the underground diaphragm wall of the clearing well and the underground diaphragm wall of the existing underground station to guide the direction of subsequent drilling. The freezing pipe, guided by the guide positioning sleeve, passes through underground obstacles and extends to the designed position. The diameter of the freezing pipe is larger than that of a conventional freezing pipe, and the freezing pipes are longitudinally connected by a sleeve thread welding method. Among them, the freezing pipes starting from the clearing wells on both sides of the existing underground station are connected front and back in the middle and arranged in staggered layers in the upper, lower and left and right directions to form a continuous horizontal freezing body.

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