Slip form blade foot and method for applying prepressing strain to cast-in-place concrete of well wall

Abstract

The invention discloses a slip form blade foot and method for applying prepressing strain to well wall cast-in-place concrete.The slip form blade foot is of an annular structure and comprises a plurality of blade foot block structures connected end to end, and each blade foot block structure comprises a blade foot block body, a vertical displacement generating device, a displacement sensor and a limiting plate; the vertical displacement generating device is arranged between the lower plate and the cambered surface plate and used for driving the cambered surface plate to move in the vertical direction. The displacement sensor is arranged at the telescopic end of the vertical displacement generating device; the device is suitable for the vertical shaft wall constructed through the top-down and short-digging and short-building technology, the cast-in-place concrete can be extruded by applying upward displacement to the cambered surface plate, pre-pressing strain can be rapidly and accurately applied to the cast-in-place concrete of the shaft wall, and the construction efficiency is improved. The compactness of cast-in-place concrete and continuous cast-in-place concrete in the well wall section is improved, and the overall water sealing performance of the well wall is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of mine roadway construction engineering, and specifically to a sliding formwork cutting edge and method for applying pre-compressive strain to cast-in-place concrete of a shaft wall. Background Technique

[0002] For vertical shaft walls constructed by the top-down, short excavation and short lining process, including but not limited to existing single-layer shaft wall structures and outer layer shaft wall structures, such as Figure 1 and Figure 2 shown, the traditional sliding formwork cutting edge is generally composed of 4 to 8 steel structure cutting edge blocks connected by bolts or welded together. As Figure 3 shown, each cutting edge block is composed of components such as an upper plate, an arc panel, an outer side plate, a lower plate, a reinforcing rib, a limiting block, an inner support rib, an inner plate, etc., which are connected by bolts or welded to each other, and the components cannot move relative to each other. The cutting edge simultaneously supports the weights of the sliding formwork and the cast-in-place concrete within this section height. Due to problems such as the temperature stress of the cast-in-place concrete of the shaft wall, the settlement of the sliding formwork cutting edge, poor workability of the concrete, or insufficient vibration, water-conducting cracks in the middle of the section and water-conducting joints often occur in the concrete of the shaft wall in some section heights after hardening. The water-conducting cracks in the middle of the section and the water-conducting joints seriously weaken the water-sealing performance of the shaft wall, and may induce shaft water inrush or shaft flooding accidents in severe cases.

[0003] During the shaft wall masonry process, applying pre-compressive strain to the cast-in-place concrete of the shaft wall is an effective way to reduce the generation of water-conducting cracks in the cast-in-place concrete shaft wall. The most common is to use micro-expansive concrete to generate micro-expansive strain in the cast-in-place concrete, generally about 300 micro-strains. The concrete expansion is restricted to generate compressive strain. However, the value of the pre-compressive strain generated by this technology in the cast-in-place concrete of the shaft wall depends on the admixture amount of the expansion agent and the restraint degree of the shaft wall concrete, and the value of the pre-compressive strain cannot be artificially adjusted or controlled actively during the hardening process of the concrete. Therefore, this technology is a passive and difficult-to-accurately-control method for applying pre-compressive strain to the cast-in-place concrete of the shaft wall.

[0004] In order to achieve the purpose of actively controlling the pre-compressive strain, there is also a method for applying pre-compressive strain to the concrete. Specifically, during the cast-in-place process of the shaft wall concrete, manually tighten the nuts at the bottom of the vertical steel bars in each section height with tools. The nuts support the joint steel plate to generate an upward displacement, and apply pre-compressive strain to the cast-in-place concrete of the shaft wall.

[0005] However, this method must rely on the nuts at the bottom of the steel bars and the joint steel plates to apply pre-compressive strain to the cast-in-place concrete of the shaft wall, and is only applicable to "Single-layer Shaft Wall with Joint Plate and Its Construction Method ZL200610088128.3". Moreover, since the tensile force of a single steel bar is only 0.2 kN to 0.52 kN, the tensile force of the steel bars generated by this method is very small, that is, the pre-compressive strain that can be applied to the concrete is very small, and the value of the pre-compressive strain cannot be accurately adjusted or controlled. And it takes at least 2 hours for workers to tighten the nuts at the bottom of the vertical steel bars in each section height, which is time-consuming and labor-intensive. All in all, the above methods are difficult to quickly and accurately apply pre-compressive strain to the cast-in-place concrete of the shaft wall. Summary of the Invention

[0006] The object of the present invention is to provide a sliding formwork cutting edge and method for applying pre-compressive strain to the cast-in-place concrete of the shaft wall, which is applicable to the vertical shaft wall constructed by the top-down and short excavation and short lining process, can quickly and accurately apply pre-compressive strain to the cast-in-place concrete of the shaft wall, improve the compactness of the cast-in-place concrete in the shaft wall section and the joint cast-in-place concrete, avoid the occurrence of mid-section water-conducting cracks and joint water-conducting joints in the shaft wall concrete after hardening, and finally significantly improve the overall water-sealing performance of the shaft wall.

[0007] The technical solution of the present invention is as follows: A sliding formwork cutting edge for applying pre-compressive strain to the cast-in-place concrete of the shaft wall, which is of a circular structure and includes a plurality of cutting edge block structures connected end to end. Each cutting edge block structure includes: a cutting edge block main body, including: a lower plate; an outer side plate vertically arranged at one end of the lower plate; a cutting edge block connecting plate, one end of which is connected to the other end of the lower plate; an upper plate, one end of which is connected to the other end of the cutting edge block connecting plate, and a hole groove is opened on the upper plate; an arc-shaped plate, one end of which slides on the outer side plate through its lower edge structure, and the other end is lapped with the upper plate; a vertical displacement generating device arranged between the lower plate and the arc-shaped plate, with a fixed end fixedly connected to the lower plate and a telescopic end fixedly connected to the arc-shaped plate, for driving the vertical displacement of the arc-shaped plate; a displacement sensor arranged on the telescopic end of the vertical displacement generating device for real-time monitoring of the vertical displacement value applied by the vertical displacement generating device; the vertical displacement h applied by the vertical displacement generating device is monitored in real time to ensure that h is not greater than L. When the stiffness of the arc-shaped plate is large enough, the overall upward vertical displacement of the arc-shaped plate is equal to the vertical displacement h applied by the vertical displacement generating device. A limiting plate, which is of an I-shaped structure and has two horizontal planes and a vertical plane. One end of one horizontal plane of the limiting plate is fixedly connected to one end of the arc-shaped plate, the vertical plane penetrates through the hole groove on the upper plate and is slidably connected to the hole groove, and the other horizontal plane is located below the upper plate. The sizes of the two horizontal planes are both larger than the size of the hole groove. The maximum upward displacement of the arc-shaped plate is equal to the length L by which the limiting plate exceeds the upper plate.

[0008] Further, the arc panel is a steel structure member, ensuring that the arc panel will not deform during the entire process of the slip form cutting edge applying pre-compressive strain to the cast-in-place concrete of the vertical shaft wall.

[0009] Further, the vertical displacement generating device is a hydraulically driven vertical displacement generating device. The hydraulic system can achieve high-precision control of displacement through a servo valve, making it more suitable for scenarios such as concrete strain monitoring that require strict alignment or graded loading.

[0010] Further, the cross-section of the lower edge structure is L-shaped. One end of the arc panel is connected to the outside of the right-angle position of the lower edge structure. The longer right-angle side of the lower edge structure is slidably connected to the inner plate surface of the outer plate, and the shorter right-angle side is lapped with the end of the outer plate away from the lower plate.

[0011] A method for applying pre-compressive strain to the cast-in-place concrete of the shaft wall, using the above-mentioned slip form cutting edge for construction, includes the following steps: S1 High tunneling construction. After the tunneling section height is equal to , lower the slip form cutting edge and align it; bind the steel bars, install the formwork, and pour the concrete. S11 Determine that the height of the cast-in-place concrete is , the value of the pre-compressive strain to be applied ; the vertical displacement h to be applied to the arc panel. The vertical displacement h is determined by the section height and the value of the pre-compressive strain to be applied , and h ≤ L, where L is the length of the limit plate exceeding the lower edge of the upper plate. S12 During the concrete pouring process, evenly distribute concrete vertical strain gauge measuring points within the section height . The measured strain values are: , ， …, ; where 2 ≤ ≤ 8, the section height = the tunneling section height = the height of the cast-in-place concrete; the average vertical strain of the concrete within the section height ; in the formula, is the label of the measuring point, is the vertical concrete strain value measured at the th measuring point; each concrete vertical strain gauge measuring point measures the vertical strain of the concrete through a concrete strain gauge. Just tie the concrete strain gauge to the vertical steel bar, and lead out the test cable of the concrete strain gauge and connect it to the test instrument to measure the strain reading. This is an existing technical means and will not be elaborated here.

[0012] The value of the pre-compressive strain to be applied as needed after the initial setting and before the final setting of the concrete , operate the vertical displacement generating device to drive the arc panel to apply an upward vertical displacement h. Before removing the formwork, the arc panel maintains this vertical displacement value unchanged.

[0013] During the process of applying the pre-compressive strain in S21, use the control program to monitor and calculate in real time the value, and through the computer feedback and the vertical displacement applied by the vertical displacement generating device to the arc panel h, so that the value is maintained at the target value .

[0014] Furthermore, during the process of applying the pre-compressive strain, in S21, making the value is maintained at the target value The control method includes the following steps: S211 Initialization: Determine the target value of the pre-compressive strain to be applied ; Zero the vertical displacement h applied by the vertical displacement generating device to the arc panel; Set the allowable error .

[0015] S212 Real-time measurement and calculation: The vertical strain value of the concrete read in real time through the concrete strain gauge buried in the concrete , and calculate the average vertical strain of the concrete within the range of the segment height .

[0016] If , then drive the vertical displacement generating device to increase the vertical displacement h of the arc panel.

[0017] If , then drive the vertical displacement generating device to decrease the vertical displacement h of the arc panel.

[0018] If is within the allowable error range, then maintain the current vertical displacement h of the arc panel.

[0019] S213 When the system reaches a stable state, and always remains within the target value within the allowable error range, stop adjusting the vertical displacement generating device.

[0020] Furthermore, the control method further includes: Limit the maximum displacement of the vertical displacement generating device, h ≤ L.

[0021] When ≤ 500 microstrain, urgently stop the vertical displacement generating device to avoid crushing the cast-in-place concrete.

[0022] ​Compared with the prior art, the beneficial effects of the present invention are as follows: During the process of concrete pouring for the shaft wall constructed by the top-down and short excavation and short lining technology, the present invention controls the vertical displacement of the arc panel by the vertical displacement generating device, applies an upward displacement extrusion to the arc panel on the cast-in-place concrete, and pre-compressive strain will be generated inside the cast-in-place concrete, which can improve the compactness of the cast-in-place concrete in the shaft wall section and the joint cast-in-place concrete, avoid the occurrence of water-conducting cracks in the section and joint water-conducting joints after the hardening of the shaft wall concrete, and finally significantly improve the overall water sealing performance of the shaft wall.

[0023] Moreover, during the process of applying a large pre-compressive strain, the present invention reads the vertical strain at different section heights in the concrete in real time through a concrete strain gauge, calculates the average vertical strain, compares the average vertical strain with the target vertical strain, and operates the vertical displacement generating device to drive the arc panel so that the average vertical strain is always maintained within the allowable error range of the target vertical strain to ensure the concrete pre-compressive strain value is 300 microstrains to 500 microstrains, reducing the risk of concrete cracking. Description of the Drawings

[0024] Figure 1 is a perspective view of a traditional cutting edge structure.

[0025] Figure 2 is a top view of a traditional cutting edge structure.

[0026] Figure 3 is a perspective view of a traditional cutting edge block structure.

[0027] Figure 4 is a top view of a traditional cutting edge block structure.

[0028] Figure 5 is a sectional view of the cutting edge block structure schematic diagram of the present invention.

[0029] Among them, 1. arc panel, 2. lower plate, 3. outer plate, 4. upper plate, 5. cutting edge block connecting plate, 6. vertical displacement generating device, 7. displacement sensor, 8. limiting plate. Detailed Embodiments

[0030] The following is combined with Figures 1 to 5, a detailed description of the specific embodiments of the present invention will be given. In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0031] It should be noted that the circuit connections involved in the present invention all adopt conventional circuit connection methods and do not involve any innovation.

[0032] Embodiment The connection structure of the slipform cutting edge for applying pre-compressive strain to the cast-in-place concrete of the wellbore and the cutting edge block of the traditional cutting edge structure is the same, both are annular structures, and both include a plurality of cutting edge block structures connected end to end. The adjacent cutting edge block structures are connected by bolts. Each cutting edge block structure of the slipform cutting edge for applying pre-compressive strain to the cast-in-place concrete of the wellbore in this embodiment includes: a cutting edge block main body, a vertical displacement generating device 6, a displacement sensor 7, and a limiting plate 8, as Figure 5As shown in the figure, the main body of the cutting edge block includes: a lower plate 2, an outer plate 3, a connecting plate 5 of the cutting edge block, an upper plate 4 and an arc panel 1. The outer plate 3 is vertically arranged at one end of the lower plate 2; one end of the connecting plate 5 of the cutting edge block is connected to the other end of the lower plate 2; one end of the upper plate 4 is connected to the other end of the connecting plate 5 of the cutting edge block, and a hole groove is provided on the upper plate 4; one end of the arc panel 1 slides on the outer plate 3 through its lower edge structure, and the other end is lapped with the upper plate 4; the cross section of the lower edge structure is L-shaped, one end of the arc panel 1 is connected to the outside of the right-angle position of the lower edge structure, the longer right-angle side of the lower edge structure is slidably connected to the inner plate surface of the outer plate 3, and the shorter right-angle side is lapped with the end of the outer plate 3 away from the lower plate 2, and cooperates with the limiting plate 8 to keep the arc panel 1 sliding in the vertical direction; the vertical displacement generating device 6 is arranged between the lower plate 2 and the arc panel 1, the fixed end is fixedly connected to the lower plate 2, and the telescopic end is fixedly connected to the arc panel 1, and is used to drive the vertical displacement of the arc panel 1. The vertical displacement generating device 6 selects one of pneumatic drive, hydraulic drive and electric drive that can be controlled by an external controller. In this embodiment, the hydraulic drive vertical displacement generating device 6 is selected. Since the hydraulic system can achieve high-precision control of displacement through a servo valve, it is more suitable for scenarios such as concrete strain monitoring that require strict alignment or graded loading; the displacement sensor 7 is arranged on the telescopic end of the vertical displacement generating device 6, and is used to monitor the vertical displacement value applied by the vertical displacement generating device 6 in real time; when the stiffness of the arc panel 1 is large enough, the overall upward vertical displacement of the arc panel 1 is equal to the vertical displacement h applied by the vertical displacement generating device 6. Control the vertical displacement generating device 6 to drive the vertical displacement of the arc panel 1, apply an upward displacement to the arc panel 1 to extrude the cast-in-place concrete, and pre-compressive strain will be generated inside the cast-in-place concrete. The limiting plate 8 is of I-shaped structure, with two horizontal planes and one vertical plane. One end of one horizontal plane of the limiting plate 8 is fixedly connected to one end of the arc panel 1, the vertical plane penetrates through the hole groove on the upper plate 4 and is slidably connected to the hole groove, and the other horizontal plane is located below the upper plate 4. The sizes of the two horizontal planes are both larger than the size of the hole groove. The displacement sensor 7 monitors the vertical displacement h applied by the vertical displacement generating device 6 in real time to ensure that h is not greater than L, that is, the maximum upward displacement of the arc panel 1 is equal to the length L of the limiting plate 8 exceeding the upper plate 4.

[0033] Control the vertical displacement generating device 6 through the hydraulic system to drive the arc panel 1 to achieve precise vertical displacement, so as to more precisely apply an upward displacement to the arc panel 1 to extrude the cast-in-place concrete, and pre-compressive strain will be generated inside the cast-in-place concrete, which can improve the compactness of the cast-in-place concrete in the shaft wall section and the joint cast-in-place concrete, and avoid the occurrence of water-conducting cracks in the section and joint water-conducting joints in the shaft wall concrete after hardening, and finally significantly improve the overall water-sealing performance of the shaft wall.

[0034] In order to ensure that the arc panel 1 will not deform during the whole process of applying pre-compressive strain to the cast-in-place concrete of the vertical shaft wall by the sliding form cutting edge, the arc panel 1 in this embodiment is a steel structure part.

[0035] A method for applying pre-compressive strain to the cast-in-situ concrete of the wellbore, using the above-mentioned slip form cutting edge for construction, includes the following steps: S1 High tunneling construction. After the excavated section height is equal to , lower the slip form cutting edge and align it; bind steel bars, install vertical forms, and pour concrete; S11 Determine that the height of the cast-in-situ concrete is , the value of the pre-compressive strain to be applied ; the vertical displacement h to be applied to the arc panel 1, and the vertical displacement h is determined by the section height and the value of the pre-compressive strain to be applied , and h ≤ L, where L is the length of the limiting plate 8 exceeding the lower edge of the upper plate 4; S12 During the concrete pouring process, evenly distribute concrete vertical strain gauge measuring points within the section height . The measured strain values are: , ， …, ; where 2 ≤ ≤ 8, the section height = the excavated section height = the height of the cast-in-situ concrete; the average vertical strain of the concrete within the section height ; in the formula, is the label of the measuring point, is the vertical concrete strain value measured at the -th measuring point; In this embodiment, takes 2m to 4m, and the value of the pre-compressive strain to be applied is 300 microstrain to 500 microstrain; the vertical displacement h to be applied to the arc panel 1 ≈ , and h ≤ L, where L is the length of the limiting plate 8 exceeding the lower edge of the upper plate 4.

[0036] Since the number of measuring points is too small, for example, arranging 1 to 2 measuring points, it may be difficult to accurately reflect the true form of the strain distribution. And if the number of measuring points is too large, for example, arranging 5 to 8 measuring points, it will not only increase the layout cost and data processing complexity, but also have limited improvement in accuracy. Therefore, in this embodiment, 3 concrete vertical strain gauge measuring points are evenly distributed within the section height . The vertical heights of the 3 concrete vertical strain gauge measuring points are respectively , and . The vertical concrete strain values measured at the 3 measuring points are respectively , and , which can effectively capture the non - linear strain gradient caused by the self - weight, shrinkage or external load of concrete. For example, compression at the bottom and tension at the top, the average vertical strain of concrete within the section height of the concrete ; The vertical strain of each concrete vertical strain gauge measuring point measures the vertical strain of the concrete through the concrete strain gauge. Just tie the concrete strain gauge to the vertical steel bar, and lead out the test cable of the concrete strain gauge and connect it to the test instrument to measure the strain reading. This is an existing technical means and will not be elaborated here.

[0037] S2 After the concrete starts to set and before it finally sets, generally 2 to 6 hours after the concrete is poured, apply the pre - compression strain value as required , operate the vertical displacement generating device 6 to drive the arc - shaped panel 1 to apply an upward vertical displacement h. Before removing the formwork, keep the vertical displacement value of the arc - shaped panel 1 unchanged.

[0038] S21 During the process of applying pre - compression strain, use the control program to monitor and calculate in real - time the value, and through the computer feedback and the vertical displacement h applied by the vertical displacement generating device 6 to the arc - shaped panel 1, so that the value remains at the target value .

[0039] Read the vertical strain at different section height positions in the concrete in real - time through the concrete strain gauge, calculate the average vertical strain, compare the average vertical strain with the vertical strain of the target value, and operate the drive of the vertical displacement generating device 6 on the arc - shaped panel 1 to keep the average vertical strain always within the allowable error range of the vertical strain of the target value, so as to ensure that the concrete pre - compression strain value is 300 micro - strain to 500 micro - strain, reducing the risk of concrete cracking.

[0040] S21 During the process of applying pre - compression strain, make the value remain at the target value The control method includes the following steps: S211 Initialization: Determine the target pre - compression strain value to be applied . Zero the vertical displacement h applied by the vertical displacement generating device 6 to the arc - shaped panel 1. Set the allowable error .

[0041] S212 Real - time measurement and calculation: Read the vertical strain of the concrete , and of the concrete in real - time through the concrete strain gauge buried in the concrete, and calculate the average vertical strain of the concrete within the section height of the concrete .

[0042] If , the vertical displacement generating device 6 is driven to increase the vertical displacement h of the arc-shaped panel 1; If , the vertical displacement generating device 6 is driven to decrease the vertical displacement h of the arc-shaped panel 1; If Within the allowable error range, the current vertical displacement h of the arc-shaped panel 1 is maintained; S213 When the system reaches a stable state and Always remains at the target value Within the allowable error range, the adjustment of the vertical displacement generating device 6 is stopped.

[0043] In some embodiments, the control method further includes: Limiting the maximum displacement of the vertical displacement generating device 6, h ≤ L.

[0044] When ≤ 500 microstrain, the vertical displacement generating device 6 is emergently stopped to avoid crushing the cast-in-place concrete.

[0045] The above-disclosed are only several preferred specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A slip form cutting edge for applying pre-compressive strain to cast-in-place concrete of a wellbore wall, which is an annular structure and includes a plurality of cutting edge block structures connected end to end. It is characterized in that, Each of the said cutting edge block structures includes: A cutting edge block main body, including: a lower plate (2); an outer side plate (3), vertically arranged at one end of the lower plate (2); a cutting edge block connecting plate (5), one end of which is connected to the other end of the lower plate (2); an upper plate (4), one end of which is connected to the other end of the cutting edge block connecting plate (5), and a hole groove is formed on the upper plate (4); an arc-shaped plate (1), one end of which slides on the outer side plate (3) through its lower edge structure, and the other end of which is lapped with the upper plate (4); A vertical displacement generating device (6), arranged between the lower plate (2) and the arc-shaped plate (1), with a fixed end fixedly connected to the lower plate (2) and a telescopic end fixedly connected to the arc-shaped plate (1), for driving the vertical displacement of the arc-shaped plate (1); A displacement sensor (7), arranged on the telescopic end of the vertical displacement generating device (6), for real-time monitoring of the vertical displacement value applied by the vertical displacement generating device (6); A limiting plate (8), with an I-shaped structure, having two horizontal planes and one vertical plane. One end of one of the horizontal planes of the limiting plate (8) is fixedly connected to one end of the arc-shaped plate (1), the vertical plane penetrates through the hole groove on the upper plate (4) and is slidably connected to the hole groove, and the other horizontal plane is located below the upper plate (4), and the sizes of the two horizontal planes are both larger than the size of the hole groove.

2. The slipform cutting edge for applying pre-compressive strain to the cast-in-place concrete of the shaft wall according to claim 1, characterized in that The arc-shaped plate (1) is a steel structure member.

3. A slipform cutting edge for applying pre-compressive strain to cast-in-place concrete of a wellbore wall according to claim 1, characterized in that, The vertical displacement generating device (6) is selected from one of pneumatic drive, hydraulic drive, and electric drive that can be controlled by an external controller.

4. A slipform cutting edge for applying pre-compressive strain to cast-in-place concrete of a wellbore wall, characterized in that, The cross-section of the lower edge structure is L-shaped, one end of the arc-shaped plate (1) is connected to the outside of the right-angle position of the lower edge structure, one right-angle side of the lower edge structure is slidably connected to the inner plate surface of the outer side plate (3), and the other right-angle side is lapped with the end of the outer side plate (3) away from the lower plate (2).

5. A method for applying pre-compressive strain to cast-in-place concrete of a wellbore wall, characterized in that, Using the slip form cutting edge according to any one of claims 1-4 for construction, includes the following steps: S1 high tunneling construction, after the excavated section height is equal to lower the sliding formwork cutting edge and align it; tie the steel bars, install the formwork, and pour the concrete; S11 Determine the height of the cast-in-place concrete to be , the value of the pre-compressive strain to be applied ; the vertical displacement h to be applied to the arc panel (1), and the vertical displacement h is determined by the segment height and the value of the pre-compressive strain to be applied , and h ≤ L, where L is the length by which the limit plate (8) extends beyond the lower edge of the upper plate (4); During the S12 concrete pouring process, within the section height are evenly distributed vertical concrete strain gauge measuring points, and the measured strain values are: , ， …, ; among them, 2 ≤ ≤ 8, the section height = excavated section height = cast-in-place concrete height, the average vertical strain of the concrete within the section height , where , in the formula, is the label of the measuring point, is the vertical concrete strain value measured at the th measuring point; The value of the pre-compressive strain applied as needed after the initial setting and before the final setting of the concrete , operate the vertical displacement generating device (6) to drive the arc-shaped panel (1) to apply an upward vertical displacement h. Before form removal, the arc-shaped panel (1) maintains this vertical displacement value unchanged; During the process of applying preloading strain, use the control program to monitor and calculate in real time value, and the vertical displacement h applied to the arc panel (1) by computer feedback and the vertical displacement generating device (6), so that value remains at the target value .

6. A method for applying pre-compressive strain to cast-in-situ concrete of a wellbore according to claim 5, characterized in that, During the application of pre-compressive strain, the control method for keeping the value at the target value includes the following steps: S211 Initialization: Determine the numerical value of the target preloading strain to be applied ; Zero the vertical displacement h applied by the vertical displacement generating device (6) to the arc-shaped plate (1); Set allowable error ; S212 Real-time measurement and calculation: By reading the vertical strain values of concrete in real time , and calculating the average vertical strain of concrete within the section height ; ; If , the driving vertical displacement generating device (6) is driven to increase the vertical displacement h of the arc-shaped panel (1). If , the driving vertical displacement generating device (6) is driven to reduce the vertical displacement h of the arc panel (1). If within the allowable error range, the current vertical displacement h of the arc panel (1) is maintained; S213 When the system reaches a stable state and always remains at the target value within the allowable error range, stop adjusting the vertical displacement generating device (6).

7. A method for applying pre-compressive strain to cast-in-place concrete of a wellbore according to claim 6, characterized in that, The said control method further includes: Restrict the maximum displacement of the vertical displacement generating device (6), h ≤ L; When ≤ 500 microstrain, the vertical displacement generating device (6) is emergently stopped to avoid crushing the cast-in-place concrete.

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