A small-diameter circular shaft unbraced excavation construction method

Abstract

The present application belongs to the technical field of underground structure construction, and provides a small-diameter circular shaft non-interior-support excavation construction method, in order to solve the problem of long construction period of the existing open-cut method shaft construction. The present application uses the cast ring beam and the tensile reinforcement as the fastening base of the steel formwork, and uses the embedded fixed pulley as the adjustment of the position of the steel formwork in the shaft, transports the steel formwork to the specified position, and then pours a section of the sidewall of the shaft. After the pouring of the section of the sidewall is completed, the steel formwork not only serves as the protective support of the pouring section, but also serves as the support of the entire sidewall of the shaft. The shaft is subjected to the cyclic operation of excavating a section and pouring a section. The construction efficiency of the sidewall of the shaft can be greatly improved, and the construction period can be shortened.

Description

Technical Field

[0001] This invention belongs to the field of underground structure construction technology, specifically relating to a method for excavating and constructing a small-diameter circular vertical shaft without internal support. Background Technology

[0002] Shafts, as vertical underground passages, are key structures in mineral resource development, water conservancy and hydropower projects, transportation tunnel construction, urban underground space development, and special underground structures (such as nuclear power plants and energy storage facilities). Shafts undertake important functions such as personnel, material, and equipment transportation, ventilation, pipeline laying, ore hoisting, and connecting underground and surface transportation, making them indispensable "choke points" for many deep underground projects.

[0003] The main steps of open-cut shaft construction are: first, construct the retaining structure (such as diaphragm walls, piles, etc.) – layered excavation and internal support – construct the main structure (constructing the base slab, side walls, etc. from bottom to top) – remove the supports. In actual construction, this method results in a long construction period due to the difficulty in setting up and removing the internal supports. Furthermore, the internal supports also affect the speed of soil and rock excavation, especially for small-diameter shafts, where the relatively small space further hinders construction progress. Summary of the Invention

[0004] To address the problem of long construction cycles in existing open-cut shaft construction methods, this invention provides a method for excavating small-diameter circular shafts without internal support. This method reduces the amount of internal support structure while ensuring construction safety, thereby shortening the construction cycle and reducing construction costs.

[0005] To solve the technical problem, the technical solution adopted by this invention is as follows: A method for excavating a small-diameter circular vertical shaft without internal support includes the following steps: constructing a retaining structure. After the retaining structure is constructed, the following steps are included: (1) Construct a ring beam at the top of the shaft. The ring beam is made of reinforced concrete and is connected to the top of the retaining structure. The ring beam is pre-embedded with pre-embedded steel bars for connecting with the steel reinforcement skeleton in the side wall. Multiple fixed pulleys are also installed on the side of the ring beam facing the center of the shaft to be excavated. (2) After the ring beam reaches the design strength, the earthwork is excavated downwards for a certain distance in the vertical shaft; the downward excavation distance is matched with the height of the steel formwork. (3) After the excavation reaches the set distance, the surface of the retaining structure is cleaned and leveled, and a waterproof layer is laid on the surface of the retaining structure after leveling. (4) Install the steel reinforcement cage of the side wall and connect the steel reinforcement cage with the pre-embedded steel bars in the ring beam; (5) Place the steel formwork into the excavated shaft and wrap the steel formwork around the fixed pulley with a wire rope; (6) Adjust the length of the wire rope to adjust the height of the steel formwork to match the depth of the excavation; (7) Pour concrete into the space between the steel formwork and the enclosure structure; (8) After the concrete to be poured reaches 50% of the design strength, continue to excavate a distance downwards into the shaft; (9) Repeat steps (3) to (8) until the pouring of the shaft sidewall is completed; finally, remove the steel formwork to complete the construction of the shaft sidewall.

[0006] In some embodiments, the ring beam is also pre-embedded with tie rods for winding the steel wire rope.

[0007] In some embodiments, displacement sensors are installed at both the top and bottom of the steel template.

[0008] In some embodiments, after the earthwork in the vertical shaft is excavated to a set distance in step (3), the excavation continues downward to form a step, and the step has an inclined surface. The lower end of the steel reinforcement cage installed in step (4) should extend into the step. Before installing the steel reinforcement cage of the next section of the side wall, the step formed by the concrete poured in the previous section should be removed and the steel reinforcement cage of the previous section should be exposed. Then the steel reinforcement cage of the previous section is connected to the steel reinforcement cage of the next section.

[0009] In some embodiments, after the earthwork in the vertical shaft is excavated to a set distance in step (3), it is continued to be excavated downward to form a step, and the step has an inclined surface; the step is equipped with an annular pad, and the pad has a through hole corresponding to the position of the vertical bar of the steel reinforcement cage. When the steel reinforcement cage is installed in step (4), the lower end of the vertical bar of the steel reinforcement cage passes through the through hole of the pad and extends into the earthwork below; the pad is also used to support the bottom of the steel formwork.

[0010] In some embodiments, the pad is fan-shaped in general, and multiple pads are spliced ​​together to form a ring shape that is compatible with the shaft.

[0011] In some embodiments, when excavating a shaft to its design elevation, it is not necessary to place a shim underneath.

[0012] In some embodiments, after the steel formwork is lowered into place in step (6), a manual ladder for construction is provided in the excavated shaft. The manual ladder has a vertical plane that is perpendicular to the horizontal plane. Multiple hydraulic cylinders or electric telescopic rods for adjusting the verticality of the steel formwork are provided on the side of the steel formwork facing the center of the shaft. The multiple hydraulic cylinders or electric telescopic rods are arranged along the inner circumference of the steel formwork. One end of the hydraulic cylinder or electric telescopic rod is fixed to the steel formwork, and the other end of the hydraulic cylinder or electric rod is used to contact the manual ladder to adjust the verticality of the steel formwork.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention relates to a method for excavating and constructing small-diameter circular vertical shafts without internal support. The method employs open-cut excavation, utilizing cast-in-place ring beams and tie rods as the foundation for securing the steel formwork. Pre-embedded fixed pulleys are used to adjust the position of the steel formwork within the shaft, transporting it to the designated location before casting a section of the shaft's sidewall. After the sidewall section is cast, the steel formwork serves both as a protective support for the cast section and as a support for the entire shaft's sidewall. This process is repeated cyclically, excavating and casting sections in a continuous cycle. Compared to existing open-cut shaft construction methods, this method eliminates the need for internal support installation and construction. Therefore, neither the excavation nor the sidewall casting is hindered by internal supports, significantly improving construction efficiency (especially for ultra-deep shafts, where the construction cycle is shortened more noticeably) and reducing costs. Furthermore, using steel formwork as shaft support offers higher safety compared to traditional internal support structures.

[0014] In particular, the benefits of putting critical infrastructure projects into operation ahead of schedule are immeasurable.

[0015] Meanwhile, the invention also installs displacement sensors at the top and bottom of the steel formwork to monitor the displacement and prevent safety accidents, thereby further improving construction safety. Attached Figure Description

[0016] Figure 1 This is a structural schematic diagram of the present invention during the preparation for pouring the uppermost section of the side wall; Figure 2 for Figure 1 A magnified view of a portion of point A in the diagram; Figure 3 This is a structural schematic diagram of the present invention when preparing to pour the bottom section of the side wall; Figure 4 This is a top view schematic diagram of the completed sidewall pouring of the shaft according to the present invention; Figure 5This is a schematic diagram of the steel formwork and manual ladder of the present invention; Figure 6 This is a top view structural schematic diagram of an embodiment of the pad of the present invention; The markings in the diagram are: 1. Enclosure structure, 2. Ring beam, 21. Embedded steel bar, 22. Tie bar, 3. Fixed pulley, 4. Steel wire rope, 5. Steel formwork, 51. Pouring port formwork, 52. Hydraulic cylinder or electric telescopic rod, 6. Manual ladder, 61. Vertical plane, 7. Space, 8. Pad, 9. Side wall, 91. Steel reinforcement cage. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are some, but not all, of the embodiments of the present invention. The following embodiments are only for specific illustration of the implementation methods of the present invention and do not limit the scope of protection of the present invention.

[0018] Referring to the accompanying drawings, the method for excavating a small-diameter circular shaft without internal support according to the present invention includes the step of constructing a retaining structure 1, and the following steps are included after the retaining structure is constructed: (1) A ring beam 2 is constructed at the top of the shaft. The ring beam 2 is made of reinforced concrete and is connected to the top of the retaining structure 1. The ring beam 2 is pre-embedded with pre-embedded steel bars 21 for connecting with the steel skeleton 91 in the side wall 9. That is, the pre-embedded steel bars 21 are part of the steel skeleton 91 when the side wall 9 is poured, thereby improving the connection strength between the ring beam 2 and the side wall 9. Multiple fixed pulleys 3 are also installed on the side of the ring beam 2 facing the center of the shaft to be excavated.

[0019] Among them, the construction of the retaining structure 1 of the shaft (such as underground continuous wall, piles, etc.) is existing technology, which can be understood by those skilled in the art.

[0020] In the specific implementation process, before constructing the ring beam 2, the loose soil layer above the soil should be cleared to ensure that the ring beam 2 has sufficient depth to ensure its strength. At the same time, when constructing the ring beam 2, it should be extended from the top of the retaining structure 1 towards the center of the shaft until it reaches the inner edge of the designed side wall 9 of the shaft. That is to say, the side of the ring beam 2 near the center of the shaft is flush with the inner wall of the designed side wall 9.

[0021] (2) After the ring beam 2 reaches its design strength, the shaft is excavated downwards for a certain distance; the distance of the downward excavation is matched with the height of the steel formwork 5. For example, assuming the height of the steel formwork 5 is 3m, the distance of excavation at one time is 3m, thus forming a cycle of excavating one section and pouring one section. Among them, the ring beam 2 serves as a stable foundation, therefore, it should be ensured that the ring beam 2 reaches its design strength before excavation.

[0022] (3) After excavation to the set distance, the surface of the retaining structure 1 is cleaned and leveled, and then a waterproof layer is laid on the surface of the retaining structure 1. The "set distance" mentioned here is the "distance" mentioned in step (2). In the specific implementation process, the size of this distance can be set according to the actual situation, such as 2m, 2.5m, 3m, etc., and the corresponding height of the steel formwork 5 is 2m, 2.5m and 3m.

[0023] (4) Install the steel reinforcement cage 91 of the side wall 9, and connect the steel reinforcement cage 91 with the pre-embedded steel bars 21 embedded in the ring beam 2, so that the cast side wall 9 and the pre-embedded steel bars 21 in the ring beam 2 form a whole. After the side wall is cast, it forms an organic whole with the ring beam and the enclosure structure, thereby improving the structural strength of the shaft. Among them, those skilled in the art can understand the steel reinforcement cage 91 of the shaft side wall 9, and it will not be described in detail here.

[0024] (5) Place the steel formwork 5 into the excavated shaft and wind the steel formwork 5 around the fixed pulley 3 via the steel wire rope 4. The steel formwork 5 is custom-made in the factory and then transported to the site for assembly. In a preferred embodiment of the present invention, the steel formwork 5 is composed of several arc-shaped formwork units spliced ​​together, and adjacent formwork units are fastened together by bolts and nuts, so that the several formwork units form a cylindrical steel formwork 5.

[0025] In the specific implementation process, the top of the steel formwork 5 is equipped with multiple lifting lugs. The steel formwork is lifted by a crane and placed into the excavated shaft. Then, through the lifting lugs and steel wire rope 4, the support of the steel formwork 5 is transferred from the crane to the fixed pulley 3 on the ring beam 2, so that the steel formwork 5 is stabilized by the traction of the steel wire rope 4.

[0026] Among them, the steel formwork 5 is customized in the factory. In order to meet the needs of vertical shaft construction at different depths, steel formwork of different heights and inner diameters can be made to suit the needs of vertical shaft construction of different diameters and depths.

[0027] (6) Adjust the length of the wire rope 4 to adjust the height of the steel formwork 5 to match the depth of the excavation.

[0028] (7) Concrete is poured into the space 7 between the steel formwork 5 and the retaining structure 1. The space between the steel formwork 5 and the retaining structure 7 is the side wall 9 to be poured. After the pouring is completed, the side wall 9 is formed. During the pouring, a pouring port formwork 51 is installed at an angle on the top of the steel formwork 5, so as to form an opening at the upper end of the steel formwork 5 to facilitate the pouring of concrete. When pouring concrete, a vibrating tool (such as a vibrator) is used to compact the poured concrete; or self-compacting concrete is used for pouring to ensure the quality of the concrete pouring.

[0029] (8) After the concrete to be poured reaches 50% of the design strength, continue to excavate a distance downwards into the shaft.

[0030] (9) Repeat steps (3) to (8) until the pouring of the shaft side wall 9 is completed; finally, remove the steel formwork 5 to complete the construction of the shaft side wall.

[0031] This invention discloses a method for excavating and constructing small-diameter circular shafts without internal support. It utilizes cast-in-place ring beams and tie rods as the foundation for securing the steel formwork, and pre-embedded fixed pulleys for adjusting the position of the steel formwork within the shaft. This allows the steel formwork to be transported to the designated position, and then a section of the shaft's sidewall is poured. After the sidewall section is poured, the steel formwork serves both as a protective support for the poured section and as a support for the entire shaft's sidewall. This process is repeated cyclically, excavating and pouring sections in a continuous cycle. Since the installation and construction of internal supports are unnecessary, neither the shaft excavation nor the sidewall pouring is hindered by internal supports. Therefore, it significantly improves the construction efficiency of shafts (especially for ultra-deep shafts, where it significantly shortens the construction cycle) and reduces construction costs. Furthermore, using steel formwork as the shaft's support provides higher safety compared to traditional internal support structures.

[0032] In particular, the benefits of putting critical infrastructure projects into operation ahead of schedule are immeasurable.

[0033] However, in existing open-cut shaft construction techniques, the entire shaft is excavated to the design elevation before pouring concrete. Although a retaining structure is arranged around the shaft, internal support structures must be installed inside the shaft to ensure construction safety. (These internal support structures come in various forms, mainly using steel profiles and steel frames for support.) The installed internal supports occupy some of the shaft's space, causing interference and affecting shaft operations. Therefore, the installation, obstruction of operations, and removal of internal supports consume a significant amount of construction time, resulting in a long construction period and high construction costs.

[0034] In the invention, when the steel formwork moves downward to the next section of the shaft for pouring, the side wall of the shaft formed by the previous section already has sufficient strength to support it, so there is no need to set up internal supports to ensure the safety of construction.

[0035] In some embodiments, the ring beam 2 is also pre-embedded with tie rods 22 for winding the wire rope 4. The function of the tie rods 22 is to wind the wire rope, thereby adjusting the length of the wire rope used to hoist the steel formwork 5, so as to facilitate the lowering of the steel formwork 5.

[0036] In some embodiments, displacement sensors are installed at both the top and bottom of the steel formwork 5. These sensors detect displacement, ensuring safety after the sidewall section is poured and during the next section of earthwork excavation, thus preventing accidents and further improving construction safety.

[0037] In some embodiments, after the earthwork in the vertical shaft is excavated to a set distance in step (3), the excavation continues downward to form a step, and the step has an inclined surface. The lower end of the steel reinforcement cage 91 installed in step (4) should extend into the step. Before installing the steel reinforcement cage of the next section of the side wall, the step formed by the concrete poured in the previous section should be removed to expose the upper section of the steel reinforcement cage 91, and then the upper section of the steel reinforcement cage 91 should be connected to the lower section of the steel reinforcement cage 91. By using the step formed during earthwork excavation and then removing the step formed by the concrete pouring, the concrete at the contact point with the earthwork can be eliminated, and the exposed upper section of the steel reinforcement cage can be connected to the lower section of the steel reinforcement cage, thereby improving the overall strength of the side wall.

[0038] In some embodiments, after the earthwork in the vertical shaft is excavated to a set distance in step (3), it is further excavated downwards to form a step, and the step has an inclined surface; the step is equipped with an annular pad 8, and the pad 8 has a through hole 81 corresponding to the position of the vertical bar of the steel reinforcement cage. When the steel reinforcement cage 91 is installed in step (4), the lower end of the vertical bar of the steel reinforcement cage 91 passes through the through hole 81 of the pad 8 and extends into the earthwork below; the pad 8 is also used to support the bottom of the steel formwork 5. Through the design of the pad, the quality of the side wall pouring can be guaranteed, and the steel reinforcement cage of the upper side wall can be exposed without removing the concrete, thereby reducing the work of removing concrete and further improving construction efficiency; at the same time, it can also support the bottom of the steel formwork, which is convenient for the positioning of the steel formwork. Meanwhile, when the lower section of earthwork is excavated, since the earthwork support is lost, the pad can be moved to other areas at any time, so as not to affect the excavation progress of the lower section of earthwork.

[0039] In some embodiments, the pad 8 is generally fan-shaped, and multiple pads 8 are spliced ​​together to form a ring shape that adapts to the vertical shaft. In specific implementations, the pad 8 is made of wood, aluminum alloy, etc., so that the pad is lightweight and can provide a certain degree of support for the steel formwork.

[0040] In the specific implementation process, a flexible sealing ring is installed in the through hole 81 of the pad plate 8, which not only facilitates the passage of the vertical bars of the steel reinforcement cage 91, but also plays a sealing role, reducing and preventing the slurry of the poured concrete from being discharged through the through hole and affecting the quality of the pouring.

[0041] In some embodiments, when excavating a shaft to its design elevation, it is not necessary to place a shim underneath.

[0042] In some embodiments, after the steel formwork 5 is lowered into place in step (6), a manual ladder 6 for construction is provided in the excavated shaft. The manual ladder 6 has a vertical surface 61 that is perpendicular to the horizontal plane. Multiple hydraulic cylinders or electric telescopic rods 52 for adjusting the verticality of the steel formwork 5 are provided on the side of the steel formwork 5 facing the center of the shaft. The multiple hydraulic cylinders or electric telescopic rods 52 are arranged along the inner circumference of the steel formwork 5. One end of the hydraulic cylinder or electric telescopic rod 52 is fixed to the steel formwork 5, and the other end of the hydraulic cylinder or electric rod is used to contact the manual ladder 6 to adjust the verticality of the steel formwork 5. The manual ladder can be used as an auxiliary tool for workers to pour concrete, vibrate and compact the concrete, and other construction operations, and can also be used as a reference for adjusting the verticality of the steel formwork 5.

[0043] It should be understood that the above description of the preferred embodiments is quite detailed, but it should not be considered as a limitation on the scope of protection of this invention. Those skilled in the art, under the guidance of this invention, can make substitutions or modifications without departing from the scope of protection of the claims of this invention, and all such substitutions or modifications fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. A method for excavating a small-diameter circular vertical shaft without internal support, comprising the step of constructing a retaining structure, characterized in that, The following steps are included after the construction of the enclosure structure: (1) Construct a ring beam at the top of the shaft. The ring beam is made of reinforced concrete and is connected to the top of the retaining structure. The ring beam is pre-embedded with pre-embedded steel bars for connecting with the steel reinforcement skeleton in the side wall. Multiple fixed pulleys are also installed on the side of the ring beam facing the center of the shaft to be excavated. (2) After the ring beam reaches the design strength, the earthwork is excavated downwards for a certain distance in the vertical shaft; the downward excavation distance is matched with the height of the steel formwork. (3) After the excavation reaches the set distance, the surface of the retaining structure is cleaned and leveled, and a waterproof layer is laid on the surface of the retaining structure after leveling. (4) Install the steel reinforcement cage of the side wall and connect the steel reinforcement cage with the pre-embedded steel bars in the ring beam; (5) Place the steel formwork into the excavated shaft and wrap the steel formwork around the fixed pulley with a wire rope; (6) Adjust the length of the wire rope to adjust the height of the steel formwork to match the depth of the excavation; (7) Pour concrete into the space between the steel formwork and the enclosure structure; (8) After the concrete to be poured reaches 50% of the design strength, continue to excavate a distance downwards into the shaft; (9) Repeat steps (3) to (8) until the pouring of the shaft sidewall is completed; finally, remove the steel formwork to complete the construction of the shaft sidewall. In step (3), after the earthwork in the vertical shaft is excavated to a set distance, it is continued to be excavated downward to form a step, and the step has an inclined surface; the step is equipped with an annular pad, and the pad has a through hole corresponding to the position of the vertical bar of the steel reinforcement cage; the lower end of the steel reinforcement cage installed in step (4) should extend into the step; before installing the steel reinforcement cage of the next section of the side wall, the step formed by the concrete poured in the previous section should be removed and the steel reinforcement cage of the previous section should be exposed, and then the steel reinforcement cage of the previous section should be connected to the steel reinforcement cage of the next section.

2. The method for excavating and constructing a small-diameter circular vertical shaft without internal support according to claim 1, characterized in that, The ring beam also has pre-embedded reinforcing bars for winding the steel wire rope.

3. The method for excavating and constructing a small-diameter circular vertical shaft without internal support according to claim 1, characterized in that, Displacement sensors are installed at both the top and bottom of the steel template.

4. The method for excavating a small-diameter circular vertical shaft without internal support according to any one of claims 1-3, characterized in that, When installing the steel reinforcement cage in step (4), the lower end of the vertical reinforcement of the steel reinforcement cage passes through the through hole of the pad and extends into the soil below; the pad is also used to support the bottom of the steel formwork.

5. The method for excavating and constructing a small-diameter circular vertical shaft without internal support according to claim 4, characterized in that, The pad is fan-shaped, and multiple pads are spliced ​​together to form a ring shape that fits the vertical shaft.

6. The method for excavating and constructing a small-diameter circular vertical shaft without internal support according to claim 5, characterized in that, When excavating the shaft to its design elevation, it is not necessary to continue excavating downwards to form steps.

7. The method for excavating and constructing a small-diameter circular vertical shaft without internal support according to claim 1, characterized in that, In step (6), after the steel formwork is lowered into place, a manual ladder is installed in the excavated shaft for easy construction. The manual ladder has a vertical plane that is perpendicular to the horizontal plane. Multiple hydraulic cylinders or electric telescopic rods for adjusting the verticality of the steel formwork are installed on the side of the steel formwork facing the center of the shaft. The multiple hydraulic cylinders or electric telescopic rods are arranged along the inner circumference of the steel formwork. One end of the hydraulic cylinder or electric telescopic rod is fixed to the steel formwork, and the other end of the hydraulic cylinder or electric rod is used to contact the manual ladder to adjust the verticality of the steel formwork.

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