An expandable soft rock stratum well wall structure and construction method

Abstract

The application discloses an inflatable soft rock stratum shaft wall structure and a construction method, and belongs to the technical field of inflatable soft rock stratum construction, and comprises temporary support, wherein the temporary support is internally provided with a shaft wall assembly; the shaft wall assembly comprises an outer layer shaft wall and an inner layer shaft wall which are sequentially arranged from outside to inside; a plurality of anchor rods are arranged between the shaft wall assembly and the temporary support; the anchor rods comprise grouting anchor rods and drainage anchor rods which are alternately arranged between the shaft wall assembly and the temporary support; a drainage mechanism is arranged in the drainage anchor rods; and waterproof heat insulation layers are arranged between the temporary support and the outer layer shaft wall and between the outer layer shaft wall and the inner layer shaft wall. The double-layer shaft wall structure adopted by the application can not only achieve the strength of the steel pipe concrete support, but also solve the problem of the extrusion of the large deformation of the mudstone, and the two-layer waterproof layer arranged in the support structure can prevent the leakage of the concrete shaft wall. The anchor rods can not only drain water, but also grout, so that the expansion of the mudstone is weakened, and the support strength of the shaft wall is strengthened.

Description

Technical Field

[0001] This invention belongs to the field of construction technology for expansive soft rock formations, and particularly relates to a wellbore structure and construction method for expansive soft rock formations. Background Technology

[0002] When constructing inclined shafts in expansive and extremely soft rock formations, commonly used support methods such as anchor bolts and cables, steel supports, and steel-concrete composite supports cannot meet the design requirements. Only by using the freezing method and adopting high-strength passive support can good results be achieved in supporting the surrounding rock of such formations. The reinforced concrete well wall structure can not only meet the support strength requirements, but also solve the problem of large deformation caused by expansive soft rock after thawing.

[0003] Circular reinforced concrete well wall structures are common support structures in vertical shafts, characterized by reasonable structural stress distribution and fast construction speed. However, in inclined shaft construction, circular reinforced concrete well wall structures require a large rough cross-section, have high support costs, and are difficult to construct, making practical engineering implementation challenging. Traditional straight-wall semi-circular arch well wall support structures, while having a small cross-section and simple construction, suffer from significant stress concentration at the bottom of the surrounding rock, leading to severe bottom bulging. Therefore, in the design of inclined shaft well wall structures in expansive soft rock strata, it is necessary to consider, on the one hand, reasonable cross-sectional dimensions, reducing stress concentration points, and emphasizing the stiffness of the well wall structure's base plate to ensure the well wall structure can resist bottom bulging and reduce horizontal stress in the sidewalls; on the other hand, it is also necessary to set yield layers, pay attention to the construction sequence of the shaft, and reduce the expansion pressure faced by the well wall structure after thawing. Summary of the Invention

[0004] The purpose of this invention is to provide a wellbore structure and construction method for expansive soft rock formations to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution: The present invention provides a wellbore structure for expansive soft rock formations, including a temporary support, wherein a wellbore assembly is provided within the temporary support, the wellbore assembly including an outer wellbore and an inner wellbore arranged sequentially from the outside to the inside, a plurality of anchor bolts are provided between the wellbore assembly and the temporary support, the anchor bolts including grouting anchor bolts and drainage anchor bolts alternately arranged between the wellbore assembly and the temporary support, the drainage anchor bolts are provided with a drainage mechanism, waterproof and heat-insulating layers are respectively provided between the temporary support and the outer wellbore and between the outer wellbore and the inner wellbore, and monitoring mechanisms are respectively provided within the temporary support and the wellbore assembly.

[0006] Optionally, a resin-filled layer is provided between the temporary support and the outer well wall.

[0007] Optionally, the tail of the drainage anchor located at the bottom of the well wall assembly is connected to an air pump.

[0008] Optionally, the drainage anchor rod comprises a hollow rod, a plurality of drainage holes are arranged on the hollow rod, a tray is slidably connected to the bottom of the hollow rod, the tray abuts against the inner wall of the temporary support, a locking mechanism is arranged at the bottom of the hollow rod and abuts against the tray, and the drainage mechanism is arranged in the hollow rod.

[0009] Optionally, a top thread is arranged at the top of the hollow rod, a nut is threadedly connected to the top thread, the drainage mechanism comprises a capillary water guide material arranged in the hollow rod, a ring hook is arranged at the top of the capillary water guide material, an iron ring is arranged at the bottom of the nut, and the iron ring is matched with the ring hook.

[0010] Optionally, the locking mechanism comprises a bottom thread arranged at the bottom of the hollow rod, a first locking nut and a second locking nut are respectively threadedly connected to the bottom thread, the first locking nut abuts against the tray, and the second locking nut abuts against the inner layer of the well wall.

[0011] Optionally, a cushion layer is arranged at the bottom of the well wall, and a water collecting groove is arranged in the middle of the cushion layer.

[0012] Optionally, the outer layer of the well wall and the inner layer of the well wall respectively adopt a reinforced concrete support structure, the main reinforcement adopts double-layer HRB335 steel bars with a diameter of 25 mm, the stirrup has a diameter of 8 mm and an interval of 200 mm.

[0013] Optionally, the temporary support is a mixed structure of a concrete spraying layer and an I-beam support.

[0014] A construction method of an expanded soft rock stratum well wall structure comprises the following steps:

[0015] S1, after the stratum is reinforced by the freezing method, the stratum is excavated by using a comprehensive excavation device;

[0016] S2, temporary support construction, spraying concrete and erecting an I-beam support;

[0017] S3, after the temporary support is completed, an anchor rod is punched in, and drainage anchor rods and grouting anchor rods are alternately arranged;

[0018] S4, the outer layer of the well wall is molded, and the outer layer of the well wall is integrally poured by using a slip form;

[0019] S5, after the outer layer of the well wall is stable, the inner layer of the well wall is poured in sections;

[0020] S6, after the inner layer of the well wall is poured in sections, the anchor rod is locked.

[0021] The application discloses the following technical effects: a section of a well wall structure of an expansive soft rock stratum is in a horseshoe shape, a well wall assembly is a double-layer reinforced concrete well wall, an inner layer well wall is sectionally built, and an outer layer well wall is integrally poured by using a slip form, the well wall assembly can ensure the stability of the well shaft, even if force majeure occurs, the well wall only has ductile deformation and damage, and the safety of well shaft construction and operation is ensured; in view of the serious water outflow of the well shaft bottom plate and the extrusion of the outer layer well wall due to the frost heaving of the frozen wall, a waterproof heat preservation layer is arranged between the temporary support and the outer layer well wall and between the outer layer well wall and the inner layer well wall, so that the water outflow and sand leakage of the well shaft are prevented, the heat preservation layer and the resin filling layer can play a pressure relief role; the drainage anchor rod and the grouting anchor rod are alternately arranged, the support strength is increased, and the drainage effect is strengthened; and the monitoring mechanism can timely and real-timely monitor the convergence deformation of the well wall in the main inclined shaft well shaft construction process, so as to provide scientific guidance for the deformation control of the well wall and the safe construction of the inclined shaft.

[0022] The double-layer well wall structure adopted by the application can not only achieve the support strength of the steel pipe concrete, but also solve the problem of large deformation extrusion of the mudstone, and the two waterproof layers arranged in the support structure can prevent the water leakage of the concrete well wall; the anchor rod can not only drain water, but also grout, so that the expansion effect of the mudstone is weakened, and the support strength of the well wall is strengthened. The application has novel structure, reasonable design, and prominent pertinence, can provide a support idea for the expansive soft rock stratum engineering, has good use effect, and is convenient to popularize and use. BRIEF DESCRIPTION OF DRAWINGS

[0023] The drawings constituting a part of the application are used to provide further understanding of the application, the embodiments of the application and the description thereof are used to explain the application, and do not constitute improper limitation on the application. In the drawings:

[0024] Figure 1 It is a section view of the inclined shaft support of the application;

[0025] Figure 2 It is a structure schematic view of the temporary support and the well wall assembly of the application;

[0026] Figure 3 It is a section view of the optical fiber arrangement of the application;

[0027] Figure 4 It is a plane view of the optical fiber arrangement of the application;

[0028] Figure 5 It is a structure schematic view of the drainage anchor rod of the application;

[0029] Figure 6 It is an internal structure schematic view of the drainage anchor rod of the application;

[0030] Figure 7 It is a distribution schematic view of the drainage anchor rod and the grouting anchor rod of the application;

[0031] Figure 8 Working principle of the alternate arrangement of the drainage anchor rod and the grouting anchor rod of the present application.

[0032] Reference signs:

[0033] 1, temporary support; 2, waterproof thermal insulation layer; 3, resin filling layer; 4, I-beam support; 5, outer layer of shaft lining; 6, inner layer of shaft lining; 7, main reinforcement; 8, stirrup; 9, anchor rod; 901, hollow rod; 902, drainage hole; 903, tray; 9041, first locking nut; 9042, second locking nut; 905, nut; 906, iron ring; 907, ring hook; 908, capillary water guide material; 909, bottom thread; 910, top thread; 10, drainage anchor rod; 11, grouting anchor rod; 12, circumferential optical fiber; 13, radial optical fiber; 14, air pump; 15, water migration; 16, water collecting tank. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0036] Reference Figures 1 to 8 As shown in the figure, the present embodiment provides a well lining structure in an expansive soft rock stratum, which comprises a temporary support 1, wherein the temporary support 1 is provided with a well lining assembly, the well lining assembly comprises an outer layer of shaft lining 5 and an inner layer of shaft lining 6 arranged in sequence from outside to inside, a plurality of anchor rods 9 are arranged between the well lining assembly and the temporary support 1, the anchor rods 9 comprise grouting anchor rods 11 and drainage anchor rods 10 arranged alternately between the well lining assembly and the temporary support 1, the drainage anchor rods 10 are provided with drainage mechanisms, the temporary support 1 and the outer layer of shaft lining 5 and the outer layer of shaft lining 5 and the inner layer of shaft lining 6 are respectively provided with waterproof thermal insulation layers 2, and the temporary support 1 and the well lining assembly are respectively provided with monitoring mechanisms.

[0037] The section of the well wall structure of the expansive soft rock stratum is a horseshoe shape, the well wall assembly is a double-layer reinforced concrete well wall, the inner layer well wall 6 is segmented and built, and the outer layer well wall 5 is integrally poured by using a slip form, the well wall assembly can ensure the stability of the shaft, even if the force majeure occurs, the well wall only has ductile deformation and damage, and the safety of the shaft construction and operation is ensured; in view of the serious water outflow of the shaft bottom plate and the frost heaving extrusion of the freezing wall on the outer layer well wall 5, the waterproof thermal insulation layer 2 is arranged between the temporary support 1 and the outer layer well wall 5 and between the outer layer well wall 5 and the inner layer well wall 6, so that the water outflow and sand leakage of the shaft are fully prevented, and the pressure relief effect can be achieved by the thermal insulation layer and the resin filling layer 3; the drainage anchor rod 10 and the grouting anchor rod 11 are alternately arranged, the support strength is increased, and the drainage effect is strengthened, and the well wall convergence deformation is monitored in time and in real time during the shaft construction of the main inclined shaft, so that scientific guidance is provided for the deformation control of the well wall and the safe construction of the inclined shaft.

[0038] The double-layer well wall structure adopted in the application can not only achieve the support strength of the steel pipe concrete, but also solve the problem of large deformation extrusion of the mudstone sealing, and the two-layer waterproof layer arranged in the support structure can prevent the water leakage of the concrete well wall; the anchor rod 9 can drain water and grout, so that the swelling effect of the mudstone is weakened, and the support strength of the well wall is strengthened. The application has novel structure, reasonable design and prominent pertinence, can provide support ideas for the expansive soft rock stratum engineering, has good use effect, and is convenient to popularize and use.

[0039] In a further optimization scheme, the resin filling layer 3 is arranged between the temporary support 1 and the outer layer well wall 5. Because the expansive soft rock section well wall is subjected to large swelling pressure, a pressure relief buffer layer needs to be separately arranged. The pressure relief buffer layer provides a certain deformation space for the expansive rock, so that the swelling pressure acting on the support is reduced. Therefore, after the outer layer well wall 5 is constructed, a 20-40mm EPS (Expanded Polystyrene, EPS) extruded plate with the characteristics of waterproofness, pressure resistance and good dimensional stability is filled in the gap between the outer layer well wall 5 and the temporary support 1 through a pre-buried pipeline, as a long-term swelling deformation buffer layer to provide a reserved deformation space.

[0040] In a further optimization scheme, the tail part of the drainage anchor rod 10 located at the bottom of the well wall assembly is connected with the air pump 14.

[0041] In a further optimization scheme, the drainage anchor rod 10 comprises a hollow rod 901, a plurality of drainage holes 902 are arranged on the hollow rod 901, a tray 903 is slidably connected to the bottom of the hollow rod 901, the tray 903 abuts against the inner wall of the temporary support 1, a locking mechanism is arranged at the bottom of the hollow rod 901 and abuts against the tray 903, and a drainage mechanism is arranged in the hollow rod 901.

[0042] In a further optimized design, the top of the hollow rod 901 is provided with a top thread 910, and the top thread 910 is threadedly connected to a nut 905. The drainage mechanism includes a capillary water-conducting material 908 disposed inside the hollow rod 901. The top of the capillary water-conducting material 908 is provided with a ring hook 907, and the bottom of the nut 905 is provided with an iron ring 906, which is adapted to the ring hook 907.

[0043] The locking mechanism is further optimized by including a bottom thread 909 at the bottom of the hollow rod 901, and a first locking nut 9041 and a second locking nut 9042 threadedly connected to the bottom thread 909. The first locking nut 9041 abuts against the tray 903, and the second locking nut 9042 abuts against the inner well wall 6.

[0044] After the temporary support 1 is completed, anchor bolts 9 are driven in to attach the tray 903 to the well wall. The first locking nut 9041 is tightened, and the threaded portion below the tray 903 is exposed for further pouring. Once both the inner and outer well walls 5 are poured, the second locking nut 9042 is tightened. This not only secures the anchor bolts 9 but also strengthens the connection between the inner and outer well walls 5. The capillary water-conducting material 908 is an H2Ri type capillary water-conducting material.

[0045] When using the drainage function, such as Figure 6 As shown, H2Ri type capillary water-conducting material 908 is inserted into the hollow rod 901 and fixed to the drainage nut 905 by the connection of iron ring 906 and ring hook 907 to prevent the capillary water-conducting material 908 from slipping down during use and affecting the drainage effect. When using the grouting function, it is not necessary to insert the capillary water-conducting material 908; the nut 905 is fixedly connected to the hollow rod 901 by the top thread 910. Due to the special nature of the strata, the water in expansive soft rock strata is mostly capillary water. Ordinary drainage components will cause the drainage hole 902 to be blocked due to the large amount of mudstone. This invention inserts capillary water-conducting material 908 into the hollow rod 901, so that even if the drainage hole 902 is blocked, the water in the soil can still be discharged from the bottom end along the direction of the rod.

[0046] The design was further optimized by adding a pad layer at the bottom of the well wall and a water collection trough 16 in the middle of the pad layer.

[0047] After grouting is completed, the grouting anchor 11 can more effectively concentrate the water migration 15 towards the drainage anchor 10, thus increasing both the support strength and the drainage effect. Considering that the drainage effect of the lower anchor 9 is affected by gravity, such as... Figure 1 As shown, an air pump 14 is connected to the end of the drainage anchor 10 to increase the air pressure difference and speed up the drainage. It can be pumped once every 10 days. The cushion layer is inclined at a 10° angle, and a water collection tank 16 is built in the middle to facilitate water storage and drainage.

[0048] Further optimization scheme, outer well wall 5 and inner well wall 6 are respectively used reinforced concrete support structure, concrete thickness 600mm, concrete mark C60, main reinforcement 7 uses double layer HRB335 reinforcement, diameter is 25mm, stirrup 8 diameter is 8mm, interval is 200mm.

[0049] Further optimization scheme, temporary support 1 is concrete spraying layer and I-steel support 4 mixed structure. Temporary support 1 is first supported by concrete spraying layer, after main inclined shaft excavation, concrete spraying layer is arranged by using wet spraying process, spraying layer thickness 50mm, concrete mark C30, then 2mm thick thermal insulation coiled material is arranged, and 10# I-steel support 4 is used for secondary support, interval of adjacent two I-steel supports 0.8m, then 100mm thick concrete is resprayed. Thermal insulation coiled material ensures that concrete 1 day strength can reach more than 60% of design strength, 3 day strength reaches design strength.

[0050] Monitoring mechanism includes hoop optical fiber 12 and radial optical fiber 13, radial optical fiber 13 is embedded in two lining structures, in order to prevent optical fiber fracture from causing test failure, every three optical fibers are arranged as a strand, one strand is embedded at vault, haunch, two sides and bottom plate midpoint, and 100m joint is reserved to connect optical fiber strain tester. Every five meters sets a monitoring section, hoop optical fiber 12 is bound and embedded on outer well wall 5 and outer well wall 5 reinforcement cage, top connects optical fiber reserved 10m, two optical fibers are embedded at two haunches, and 3m is reserved to connect strain tester.

[0051] Strain tester can obtain optical fiber Brillouin spectrum curve, key parameters in the curve include: Brillouin frequency shift, spectrum line width, peak power. Wherein frequency shift amount Δv B Corresponding strain Δε=Δv B / C ε , C ε is strain coefficient; when spectrum line width increases significantly (more than 20%), it indicates local deformation or damage; power drop may indicate optical fiber fracture or severe deformation. Spectrum curve shape also reflects different deformation characteristics, overall translation of spectrum curve, frequency shift amount uniformly changes along optical fiber length, corresponding to uniform deformation; frequency shift suddenly changes at specific position, spectrum line appears sharp peak or broadening at the point, corresponding to local deformation; spectrum line appears multiple peaks or distortion, frequency shift gradient changes sharply, corresponding to internal stress concentration or layered deformation of rock-soil body.

[0052] A construction method of an expansive soft rock stratum well wall structure, comprising the following steps:

[0053] S1, after stratum is reinforced by freezing method, stratum excavation is carried out by using fully mechanized equipment;

[0054] S2, temporary support 1 construction, spraying concrete and erecting I-steel support 4;

[0055] S3, after the temporary support 1 is completed, the anchor rod 9 is punched, and the drainage anchor rod 10 and the grouting anchor rod 11 are arranged alternately;

[0056] S4, the outer shaft lining 5 is molded, and the slip form is used for integral pouring;

[0057] S5, after the outer shaft lining 5 is stable, the inner shaft lining 6 is poured in sections;

[0058] S6, after the inner shaft lining 6 is poured in sections, the anchor rod 9 is locked.

[0059] In the construction of the thick inverted-arch bottom plate, the pouring space is excavated according to the requirements, the reinforcement cage is placed, and then the concrete is poured. If the inverted-arch bottom plate has wedge-shaped arch feet, the bottom plate should be excavated by expanding outward at the bottom corners of the shaft wall, and the expansion depth and angle should be implemented according to the scheme.

[0060] In the selection of the pouring concrete grade, the support force of each section of the shaft lining is first determined through calculation, then the appropriate concrete grade range is determined according to the section size, shaft lining thickness and construction difficulty, and finally the best concrete grade is selected according to the properties of different grade concretes and the site maintenance conditions (such as hydration heat, early strength performance, fluidity, frost resistance, durability, etc.).

[0061] During the freezing of the shaft, the strength of the frozen wall can play the role of "temporary support 1" for a short time. Due to the disassembly of the freezing pipes of the top and bottom plates of the shaft, the top and bottom parts of the frozen wall thaw, which reduces the strength of the top and bottom of the frozen wall. Especially in the mudstone section, the expansion pressure caused by local thawing directly acts on the bottom and top of the temporary support 1 body, and the frost heaving force generated by the two sides of the frozen wall also affects the temporary support 1 body. However, as long as the thickness of the upper and lower frozen walls is not less than 6m and the thickness of the two sides of the frozen wall is not less than 3m, the expansion pressure caused by local thawing can be solved by locally densifying the mine I-shaped steel support 4. The frost heaving pressure of the shaft is small when the frozen wall is stable, and the waterproof and heat preservation layer 2 behind the outer shaft lining 5 has certain elasticity and compressibility. This part of the frost heaving pressure can be completely released through the waterproof and heat preservation layer 2. During the freezing period, the temperature of the shaft wall is generally low (the freezing pipe has not been disassembled, and the temperature of the shaft wall is generally lower than -10℃), the thawing range of the frozen wall is quite limited, and the thawed soil behind the wall has experienced the frost heaving process. Therefore, under the condition of no new water supply, the frost heaving pressure of the thawed soil is small, and the design of the temporary support 1 can completely ensure the stability and safety of the outer shaft lining 5 during pouring. During the freezing period, after the outer shaft lining 5 is built, the outer shaft lining 5 bears part of the frozen pressure before reaching the design strength due to the existence of the frost heaving pressure inside and outside the frozen wall. The heat preservation layer and the resin filling layer 3 can play the role of pressure relief. Frost heaving force pressure relief holes can also be set (the freezing scheme needs to be considered). Of course, the temporary support 1 structure is crucial in the initial stage of the growth of the frozen pressure.

[0062] In the description of the present application, it is to be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are intended to indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0063] The above-described embodiments are only to describe the preferred modes of the present application, and are not intended to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A wellbore structure for expansive soft rock formations, characterized in that: The system includes a temporary support (1), which is equipped with a well wall assembly. The well wall assembly includes an outer well wall (5) and an inner well wall (6) arranged sequentially from the outside to the inside. Multiple anchor bolts (9) are provided between the well wall assembly and the temporary support (1). The anchor bolts (9) include grouting anchor bolts (11) and drainage anchor bolts (10) alternately arranged between the well wall assembly and the temporary support (1). A drainage mechanism is provided in the drainage anchor bolts (10). Waterproof and heat-insulating layers (2) are provided between the temporary support (1) and the outer well wall (5) and between the outer well wall (5) and the inner well wall (6). Monitoring mechanisms are provided in the temporary support (1) and the well wall assembly. The drainage anchor (10) includes a hollow rod (901), which has multiple drainage holes (902). A tray (903) is slidably connected to the bottom of the hollow rod (901). The tray (903) abuts against the inner wall of the temporary support (1). A locking mechanism is provided at the bottom of the hollow rod (901), which abuts against the tray (903). The drainage mechanism is provided inside the hollow rod (901). The hollow rod (901) has a top thread (910) at its top, and a nut (905) is threaded onto the top thread (910). The drainage mechanism includes a capillary water-conducting material (908) disposed inside the hollow rod (901). A ring hook (907) is provided at the top of the capillary water-conducting material (908), and an iron ring (906) is provided at the bottom of the nut (905). The iron ring (906) is adapted to the ring hook (907). The locking mechanism includes a bottom thread (909) at the bottom of the hollow rod (901), on which a first locking nut (9041) and a second locking nut (9042) are threadedly connected respectively. The first locking nut (9041) abuts against the tray (903), and the second locking nut (9042) abuts against the inner well wall (6).

2. The wellbore structure for expansive soft rock formations according to claim 1, characterized in that: A resin filling layer (3) is provided between the temporary support (1) and the outer well wall (5).

3. The wellbore structure for expansive soft rock formations according to claim 1, characterized in that: The tail of the drainage anchor (10) located at the bottom of the well wall assembly is connected to an air pump (14).

4. The wellbore structure for expansive soft rock formations according to claim 1, characterized in that: The bottom of the well wall is provided with a cushion layer, and a water collection trough (16) is provided in the middle of the cushion layer.

5. The wellbore structure for expansive soft rock formations according to claim 1, characterized in that: The outer well wall (5) and the inner well wall (6) are respectively adopted as reinforced concrete support structures. The main reinforcement (7) adopts double-layer HRB335 steel bars with a diameter of 25mm, and the stirrups (8) have a diameter of 8mm and a spacing of 200mm.

6. The wellbore structure for expansive soft rock formations according to claim 1, characterized in that: The temporary support (1) is a hybrid structure of concrete spraying and I-beam support (4).

7. A construction method for a wellbore structure in expansive soft rock formations, based on the wellbore structure in expansive soft rock formations as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. After the strata are reinforced by freezing method, the strata are excavated using fully mechanized tunneling equipment; S2, Temporary support (1) Construction, spraying concrete and erecting I-beam supports (4). S3. After the temporary support (1) is completed, drive in the anchor bolts (9) and alternately set the drainage anchor bolts (10) and the grouting anchor bolts (11); S4. The outer well wall (5) is cast in one piece using slipform casting. S5. After the outer well wall (5) has stabilized, the inner well wall (6) is poured in sections. S6. After the inner well wall of the segment (6) is poured, lock the anchor rod (9).

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