A method of constructing a locally deepened open excavation shaft

Abstract

The present invention provides a construction method for a locally deepened open-cut shaft, which relates to the technical field of tunnel construction and includes: first constructing a diaphragm wall, excavating to a first preset elevation to construct the first ring beam, then excavating down to a second preset elevation, and constructing the second ring beam and the first side wall between the first ring beam and the second ring beam; taking the bottom of the second ring beam as the excavation surface, constructing the shaft foundation and the locally deepened foundation, arranging a vertical support member between the top surface of the locally deepened foundation and the bottom surface of the second ring beam, and constructing the remaining side walls and ring beams from bottom to top relying on the vertical support member and the first side wall until the top of the shaft is closed, and finally constructing the second side wall between the top surface of the locally deepened foundation and the bottom surface of the second ring beam. This method improves the closing speed and construction safety of the main structure of the locally deepened open-cut shaft. By constructing the ring beam as a permanent support structure, the demolition process of the temporary waist beam is eliminated, and the problem of asynchronous construction of the left and right side walls in the traditional top-down method is solved.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a construction method for locally deepening open-cut vertical shafts. Background Technology

[0002] With the rapid development of urban underground space, rail transit construction, and cross-river and cross-sea tunnel projects, open-cut shafts, as auxiliary structures in tunnel construction, are widely used in scenarios such as personnel access, equipment hoisting, material transportation, ventilation and drainage, and emergency escape. In areas with abundant groundwater and complex geological conditions (such as soft soil and sand layers), in order to meet the needs of shaft drainage and flood prevention, low-level equipment installation (such as drainage pumps and fire pumps), and connection to underground pipelines or tunnels, most open-cut shafts require a locally deepened area at the bottom of the foundation pit (as a sump or equipment installation pit). The construction quality and safety of this locally deepened area directly determine the stability and operational reliability of the entire shaft structure, becoming a key and difficult process in open-cut shaft construction.

[0003] Currently, the construction methods for partially deepening open-cut shafts in the industry generally result in excessively long exposure times of the pit sidewalls, which can easily lead to soil collapse, ground subsidence, and even safety accidents such as cracking of surrounding buildings and damage to underground pipelines. Therefore, there is an urgent need for a construction method for partially deepening open-cut shafts to shorten the pit exposure time and thus reduce construction safety risks. Summary of the Invention

[0004] The purpose of this invention is to address the above problems by providing a construction method for locally deepening open-cut shafts.

[0005] This invention provides a construction method for partially deepened open-cut shafts, wherein the partially deepened open-cut shafts are constructed using layered excavation. The method includes:

[0006] S1. Construct diaphragm walls within the shaft construction area to form a shaft pit retaining system;

[0007] S2. Within the range of the underground continuous wall, the foundation pit is excavated to the first preset elevation, and the first ring frame beam is constructed; and the excavation continues downward along the first preset elevation to the second preset elevation, where the second ring frame beam is constructed, and the first side wall is constructed between the first ring frame beam and the second ring frame beam.

[0008] S3. Using the soil at the bottom of the second ring beam as the excavation surface, construct the shaft foundation and locally deepen the foundation downwards to form the shaft foundation and the locally deepened foundation.

[0009] S4. A vertical support member is provided between the top surface of the locally deepened base and the bottom surface of the second ring frame beam;

[0010] S5. Using the vertical support members and the first side wall as construction supports, continuously construct all remaining side walls and ring frame beams of the main structure layer of the shaft from bottom to top until the main structure of the shaft is closed at the top.

[0011] S6. After the main structure of the shaft is closed, the second side wall is constructed between the top surface of the locally deepened foundation and the bottom surface of the second ring frame beam to complete the construction of the locally deepened open-cut shaft.

[0012] According to the technical solutions provided by certain embodiments of the present invention, the method further includes, before step S6: sealing the bottom of the locally deepened base, wherein the top surface elevation of the locally deepened base after sealing is equal to the bottom surface elevation of the shaft base.

[0013] According to the technical solutions provided in certain embodiments of the present invention, the bottom sealing process includes:

[0014] The interior of the locally deepened base is filled with sand in layers and then compacted.

[0015] A steel plate is laid on top of the sand-filled layer to seal the locally deepened base.

[0016] A concrete cover plate is poured on top of the steel plate so that the top surface elevation of the locally deepened base is flush with the bottom surface elevation of the shaft base.

[0017] According to the technical solutions provided in certain embodiments of the present invention, within the range of the underground diaphragm wall, the foundation pit is excavated to a first preset elevation, and the first ring frame beam is constructed, including:

[0018] The soil within the range of the underground continuous wall is excavated in layers and temporary supports are set up until the excavation depth reaches the first preset elevation. Then, the first concrete cushion layer is poured on the soil surface at the first preset elevation.

[0019] The reinforcement of the first ring frame beam is tied on the first concrete cushion layer, and the first pouring pipe and the first reinforcement connector are installed on the reinforcement of the first ring frame beam.

[0020] Install the first ring frame beam formwork outside the reinforcement of the first ring frame beam, and pour concrete into the first ring frame beam formwork;

[0021] After the concrete poured inside the formwork of the first ring beam reaches the design strength, the formwork of the first ring beam is removed, and the construction of the first ring beam is completed.

[0022] According to the technical solutions provided in certain embodiments of the present invention, excavation continues downward from the first preset elevation to the second preset elevation, and the construction of the second ring frame beam and the construction of the first sidewall between the first ring frame beam and the second ring frame beam are carried out, including:

[0023] Continue excavating downwards from the first preset elevation to the second preset elevation, and pour a second concrete cushion layer on the soil surface at the second preset elevation;

[0024] Waterproofing work is carried out on the underground continuous wall between the second concrete cushion layer and the first ring frame beam;

[0025] The reinforcement of the second ring beam is tied on the second concrete cushion layer, and the second pouring pipe and the second reinforcement connector are installed on the reinforcement of the second ring beam; at the same time, the reinforcement of the first side wall is tied on the underground continuous wall between the first ring beam and the second ring beam; and the reinforcement of the first side wall is connected with the first reinforcement connector and the reinforcement of the second ring beam into a whole.

[0026] Install the second ring frame beam formwork outside the reinforcement of the second ring frame beam, and install the first side wall formwork outside the reinforcement between the first ring frame beam and the second ring frame beam.

[0027] Concrete was poured into the formwork of the second ring beam;

[0028] After the concrete poured into the second ring beam formwork reaches the design strength, concrete is poured into the first side wall formwork through the first pouring pipe on the first ring beam.

[0029] After the concrete poured into the first side wall formwork reaches the design strength, the second ring beam formwork and the first side wall formwork are removed to complete the construction of the second ring beam and the first side wall.

[0030] According to certain embodiments of the present invention, the shaft foundation includes a shaft bottom slab and a third side wall, and the construction of the shaft foundation includes:

[0031] Using the soil at the bottom of the second ring frame beam as the excavation surface, continue excavating downwards to the third preset elevation, and pour the third concrete cushion layer on the soil surface at the third preset elevation;

[0032] Waterproofing construction is carried out on the third concrete cushion layer, and the reinforcement binding construction of the shaft bottom plate, the installation construction of the shaft bottom plate formwork, and the concrete pouring construction of the shaft bottom plate are carried out in sequence on the surface of the third concrete cushion layer after the waterproofing construction is completed.

[0033] After the concrete poured inside the formwork of the shaft bottom slab reaches the design strength, the formwork of the shaft bottom slab is removed, and the construction of the shaft bottom slab is completed.

[0034] Waterproofing construction, reinforcement binding construction of the third side wall, and installation construction of the formwork of the third side wall are carried out sequentially at a predetermined position on the underground continuous wall between the bottom plate of the shaft and the second ring frame beam. Concrete is poured into the formwork of the third side wall through the second pouring pipe on the second ring frame beam. The predetermined position is determined according to the specifications of the reserved tunnel boring machine tunneling channel.

[0035] After the concrete poured into the third side wall formwork reaches the design strength, the third side wall formwork is removed and the third side wall is backfilled using lateral support components, thus completing the construction of the shaft foundation.

[0036] According to the technical solutions provided in certain embodiments of the present invention, the locally deepened foundation includes a third ring frame beam, a locally deepened bottom plate, and a fourth side wall, and the construction of the locally deepened foundation includes:

[0037] With the soil at the bottom of the second ring beam as the excavation surface, continue excavating downwards to the fourth preset elevation. On the soil surface at the fourth preset elevation, the subbase pouring construction, the reinforcement binding of the third ring beam, the installation of the third pouring pipe and the third reinforcement connector, the installation of the third ring beam formwork, and the pouring of concrete into the third ring beam formwork are carried out in sequence.

[0038] After the concrete poured inside the formwork of the third ring beam reaches the design strength, the formwork of the third ring beam is removed to obtain the third ring beam.

[0039] Continue excavating downwards from the fourth preset elevation to the fifth preset elevation. On the soil surface at the fifth preset elevation, perform the following in sequence: pouring of the cushion layer, waterproofing, binding of the reinforcing bars for locally deepening the bottom slab, installation of the formwork for locally deepening the bottom slab, and pouring of concrete for locally deepening the bottom slab.

[0040] After the concrete poured inside the partially deepened base slab formwork reaches the design strength, the partially deepened base slab formwork is removed to complete the construction of the partially deepened base slab.

[0041] Waterproofing construction, reinforcement binding construction of the fourth side wall, and installation construction of the formwork of the fourth side wall are carried out sequentially on the underground continuous wall between the locally deepened bottom slab and the third ring frame beam. Concrete is poured into the formwork of the fourth side wall through the third pouring pipe on the third ring frame beam.

[0042] After the concrete poured inside the fourth side wall formwork reaches the design strength, the fourth side wall formwork is removed to complete the construction of the locally deepened foundation.

[0043] According to the technical solutions provided by certain embodiments of the present invention, the vertical support member is a steel column, which is spaced out at the corners of the top surface of the locally deepened base to avoid the tunneling passage of the tunnel boring machine.

[0044] According to the technical solutions provided in certain embodiments of the present invention, using the vertical support members and the first side wall as construction supports, all remaining side walls and ring frame beams of the main structure layer of the shaft are continuously constructed from bottom to top until the main structure of the shaft is closed at the top, including:

[0045] S501. Using the locally deepened base plate as the starting reference plane for scaffolding erection, when the scaffolding is erected to the preset construction position of each floor, waterproofing construction, tying construction of the ring beam and side wall reinforcement, installation construction of the ring beam formwork and side wall formwork, and concrete pouring construction of the ring beam and side wall are carried out in sequence.

[0046] S502. When the concrete of the ring frame beam and the side wall of each layer reaches the design strength, the formwork of the ring frame beam and the side wall are removed, and the side wall is backfilled with lateral support components until the construction of the ring frame beam and side wall of the top layer of the main structure of the shaft is completed, so as to realize the closure of the main structure of the shaft at the top.

[0047] In summary, this invention provides a construction method for partially deepened open-cut shafts, wherein the partially deepened open-cut shafts are excavated in layers. The method includes: constructing a diaphragm wall within the shaft construction area to form a shaft foundation pit support system; excavating the foundation pit to a first preset elevation within the diaphragm wall area and constructing a first ring beam; continuing excavation downwards from the first preset elevation to a second preset elevation and constructing a second ring beam; and constructing a first side wall between the first and second ring beams; with the soil at the bottom of the second ring beam as the excavation surface, the excavation proceeds downwards. The construction of the shaft foundation and the locally deepened foundation are carried out to form the shaft foundation and the locally deepened foundation. A vertical support member is set between the top surface of the locally deepened foundation and the bottom surface of the second ring frame beam. Using the vertical support member and the first side wall as construction support, all remaining side walls and ring frame beams of the main shaft structure are continuously constructed from bottom to top until the main shaft structure is closed at the top. After the main shaft structure is closed, the construction of the second side wall is carried out between the top surface of the locally deepened foundation and the bottom surface of the second ring frame beam to complete the construction of the locally deepened open-cut shaft. This invention first constructs a first ring frame beam, a second ring frame beam, and a first side wall between them, and sets vertical support components on the top surface of the locally deepened foundation, so that these two components can serve as supports for subsequent construction. This allows the main structure of the shaft to be closed from bottom to top. Finally, the remaining second side wall in the locally deepened area is constructed. This shortens the exposure time of the unsupported side walls of the shaft foundation pit, effectively avoids safety risks such as soil collapse, water and sand inrush, and ground settlement that are prone to occur during construction, improves the closure speed of locally deepened open-cut shafts, and enhances construction safety.

[0048] It should be understood that the descriptions of technical features, technical solutions, beneficial effects, or similar language in this invention do not imply that all features and advantages can be achieved in any single embodiment. Rather, it is understood that the description of a feature or beneficial effect means that a specific technical feature, technical solution, or beneficial effect is included in at least one embodiment. Therefore, the descriptions of technical features, technical solutions, or beneficial effects in this specification do not necessarily refer to the same embodiment. Furthermore, the technical features, technical solutions, and beneficial effects described in this embodiment can be combined in any suitable manner. Those skilled in the art will understand that embodiments can be implemented without one or more specific technical features, technical solutions, or beneficial effects of a particular embodiment. In other embodiments, additional technical features and beneficial effects may be identified in specific embodiments that do not embody all embodiments. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the construction process for partially deepening an open-cut shaft, provided as an embodiment of the present invention.

[0051] Figure 2 This is a schematic diagram of the construction process for step S5 provided in an embodiment of the present invention;

[0052] Figure 3 This is a schematic diagram of a partially deepened open-cut shaft provided in an embodiment of the present invention;

[0053] Figure 4 This is a schematic diagram showing the installation position of the vertical support member provided in an embodiment of the present invention.

[0054] The text labels in the image represent:

[0055] 1. First ring frame beam; 2. Second ring frame beam; 3. First side wall; 4. Vertical support component; 5. Shaft foundation; 51. Shaft bottom plate; 52. Third side wall; 6. Partially deepened foundation; 61. Third ring frame beam; 62. Partially deepened bottom plate; 63. Fourth side wall; 7. Second side wall; 8. Tunnel boring machine tunneling passage. Detailed Implementation

[0056] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. This description is merely illustrative and explanatory, and should not be construed as limiting the scope of protection of the present invention in any way. Specifically, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0057] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus.

[0058] During the construction and operation phases of urban underground engineering, open-cut shafts serve as auxiliary structures for tunnel construction, widely used for personnel access, equipment hoisting, material transportation, ventilation and drainage, and emergency escape. In areas with abundant groundwater and complex geological conditions (such as soft soil and sand layers), a locally deepened area needs to be constructed at the bottom of the shaft pit to meet the core drainage and flood control requirements of the shaft. This locally deepened area acts as a collection well, effectively collecting groundwater that seeps into the pit during shaft construction, as well as rainwater flowing into the open-cut section, preventing water accumulation in the pit that could soften the soil and cause structural leakage. Simultaneously, the low-lying space in this area is suitable for the installation and deployment of low-level drainage equipment such as drainage pumps and fire pumps, enabling rapid pumping out of the pit and fundamentally preventing rainwater and groundwater from flowing back into the shield tunnel and other subsequent underground structures through the open-cut section, thus avoiding equipment damage and structural damage. Therefore, the construction of a locally deepened area at the bottom of the pit is a necessary design to ensure soil and water stability during shaft construction and reliable drainage during operation.

[0059] However, in existing technologies, the construction of partially deepened open-cut shafts generally adopts a sequential construction method of "foundation first, sidewalls later." This means following the conventional inertia of open-cut foundation pit construction, first completing the layered excavation of the entire shaft foundation pit, then constructing the locally deepened area, and finally constructing the main shaft sidewalls after the entire structure of the locally deepened area is completed. However, in practical engineering applications, completing the entire structure of the locally deepened area before constructing the shaft sidewalls results in excessively long exposure time of the foundation pit sidewalls. This can easily lead to soil collapse, ground settlement, and even safety accidents such as cracking of surrounding buildings and damage to underground pipelines, making it unsuitable for the safety requirements of complex construction environments.

[0060] As mentioned above, in view of the problems in the prior art, this embodiment provides a construction method for locally deepening open-cut shafts. The locally deepened open-cut shaft adopts a layered excavation method, which includes:

[0061] S1. Construct diaphragm walls within the shaft construction area to form a shaft pit retaining system;

[0062] S2. Within the range of the underground continuous wall, the foundation pit is excavated to the first preset elevation, and the first ring frame beam 1 is constructed; and the excavation continues downward along the first preset elevation to the second preset elevation, and the second ring frame beam 2 is constructed, and the first side wall 3 is constructed between the first ring frame beam 1 and the second ring frame beam 2.

[0063] S3. With the soil at the bottom of the second ring beam 2 as the excavation surface, construct the shaft foundation 5 and the locally deepened foundation 6 downwards to form the shaft foundation 5 and the locally deepened foundation 6.

[0064] S4. A vertical support member 4 is installed between the top surface of the locally deepened base 6 and the bottom surface of the second ring frame beam 2.

[0065] S5. Using the vertical support member 4 and the first side wall 3 as construction supports, continuously construct all remaining side walls and ring frame beams of the main structure layer of the shaft from bottom to top until the main structure of the shaft is closed at the top.

[0066] S6. After the main structure of the shaft is closed, the second side wall 7 is constructed between the top surface of the locally deepened foundation 6 and the bottom surface of the second ring frame beam 2 to complete the construction of the locally deepened open-cut shaft.

[0067] For details, please refer to Figure 1 , Figure 3 and Figure 4Before excavating the foundation pit of the partially deepened open-cut shaft, a diaphragm wall is constructed within the shaft construction area (i.e., the excavation area of ​​the partially deepened open-cut shaft) to form a retaining system for the shaft foundation pit, preventing soil collapse around the pit from affecting subsequent construction. Diaphragm walls include various types such as cast-in-place reinforced concrete diaphragm walls, precast reinforced concrete diaphragm walls, and steel-cement-soil mixing walls, which can be selected appropriately based on the geological conditions, hydrological characteristics, and engineering requirements of the shaft construction area; no specific limitations are made here. Subsequently, the soil within the diaphragm wall area is excavated in layers. When the foundation pit is excavated to the first preset elevation, the first ring frame beam 1 is constructed. After the first ring beam 1 is constructed, excavation continues downwards from the first preset elevation to the second preset elevation for the construction of the second ring beam 2 and the construction of the first side wall 3 between the first ring beam 1 and the second ring beam 2. This provides support for the subsequent construction of the side walls and ring beams above the first side wall 3 (i.e., all remaining side walls and ring beams of the main shaft structure layer) and prevents foundation pit deformation. After the second ring beam 2 and the first side wall 3 are constructed, the excavation surface at the bottom of the second ring beam 2 is used as the excavation surface for the construction of the shaft base 5 and the locally deepened base 6, forming the shaft base 5 and the locally deepened base 6. The locally deepened base 6 will be used as a sump. After the shaft base 5 and the locally deepened base 6 are constructed, a vertical support member 4 is installed between the top surface of the locally deepened base 6 and the bottom surface of the second ring beam 2. The vertical support member 4 is used to prevent the weight of the side walls and ring beams above the first side wall 3 from affecting the first side wall 3 and to prevent foundation pit deformation. Then, using the vertical support member 4 and the first side wall 3 as construction supports, all remaining side walls and ring frame beams of the main structure layer of the shaft are continuously constructed from bottom to top until the main structure of the shaft is closed at the top. After the main structure of the shaft is closed, the second side wall 7 is constructed between the top surface of the locally deepened foundation 6 and the bottom surface of the second ring frame beam 2, finally completing the construction of the locally deepened open-cut shaft.

[0068] This invention first constructs a first ring frame beam 1, a second ring frame beam 2, and a first side wall 3 between them, and sets a vertical support member 4 on the top surface of the locally deepened foundation. Through the vertical bearing effect of the first ring frame beam 1, the second ring frame beam 2, the first side wall 3, and the vertical support member 4, the combined structure forms a stable rigid support system, which serves as the force support for the subsequent construction of the remaining upper shaft main structure. This allows the shaft main structure to be closed from bottom to top, ensuring that the foundation pit sidewalls are always in an effective support state during the construction of the shaft main structure. Finally, the remaining second side wall 7 in the locally deepened area is constructed to complete the construction of the entire shaft structure. Compared to the traditional construction method of first fully constructing the shaft foundation 5 and the partially deepened foundation 6, and then constructing the ring frame beam and side walls above them, this invention shortens the exposure time of the unsupported side walls of the shaft foundation pit, effectively avoids safety risks such as collapse, water and sand inrush, and ground settlement that are prone to occur during foundation pit excavation and structural construction, and improves the structural closure speed and construction safety of the partially deepened open-cut shaft.

[0069] In a preferred embodiment, before step S6, the method further includes: sealing the bottom of the locally deepened base 6, wherein the top surface elevation of the locally deepened base 6 after sealing is equal to the bottom surface elevation of the shaft base 5.

[0070] Specifically, before constructing the second side wall 7, the locally deepened foundation 6 should be sealed. Sealing refers to the process of filling the locally deepened foundation 6 with reinforced concrete after the shaft has been excavated to the design elevation, in order to form a solid and stable load-bearing foundation. The purpose of sealing is to isolate groundwater, enhance the overall bearing capacity of the locally deepened foundation 6, and prevent problems such as settlement and softening of the locally deepened foundation 6 due to uneven stress and groundwater immersion during the later construction of the second side wall 7. This ensures the flatness and structural stability of the second side wall 7 construction, while also preventing groundwater from seeping into the main structure of the shaft and affecting the overall construction quality. The top surface elevation of the locally deepened foundation 6 after sealing should be equal to the bottom surface elevation of the shaft foundation 5. During later construction, the top surface of the locally deepened foundation 6 after sealing can serve as the working surface for the construction of the second side wall 7, providing stable support for the subsequent construction of the second side wall 7. The sealing treatment of the partially deepened foundation 6 here is a temporary closure measure. After the tunnel boring machine successfully passes through the shaft area, the temporary sealing structure will be removed so that the partially deepened foundation 6 can restore the original function of the water collection well, meet the drainage and water collection needs of subsequent projects, and ensure the integrity and practicality of the construction process.

[0071] In a preferred embodiment, the bottom sealing process includes:

[0072] The interior of the locally deepened base 6 was filled with sand in layers and compacted.

[0073] A steel plate was laid on the top surface of the sand-filled layer to seal the locally deepened base 6.

[0074] A concrete cover plate is poured on top of the steel plate so that the top surface elevation of the locally deepened base 6 is level with the bottom surface elevation of the shaft base 5.

[0075] Specifically, the sealing process begins with layered sand filling and compaction of the interior of the locally deepened foundation 6. Layered construction avoids the problems of voids and insufficient density caused by excessively thick sand filling at once. After compaction, the undulating surface of the locally deepened foundation 6 is effectively leveled. Simultaneously, the moderate permeability and strong bearing capacity of the sand after compaction fill the voids in the loose soil of the foundation, enhancing the overall stability of the foundation. After the sand filling layer is compacted to the designed thickness and density, a steel plate is laid on top for sealing. The steel plate has good rigidity and sealing properties, completely preventing groundwater from seeping into the work area from the voids in the sand filling layer. It also provides rigid constraint on the sand filling layer below, preventing loosening and settlement due to subsequent construction disturbances. Furthermore, it provides a flat and solid working surface for the subsequent concrete cover pouring, avoiding problems such as grout leakage and uneven forming during concrete pouring. Finally, a concrete cover plate is poured on top of the steel plate. During the pouring process, the concrete elevation is strictly controlled to ensure that the top surface of the concrete cover plate (i.e. the top surface of the locally deepened base 6) is level with the bottom surface of the shaft base 5 after the pouring is completed. This makes the two form a continuous load-bearing whole, which can not only provide a stable working platform for the subsequent construction of the second side wall 7 and ensure the quality of subsequent construction, but also further strengthen the integrity and load-bearing capacity of the bottom sealing structure and resist groundwater pressure.

[0076] In a preferred embodiment, within the area of ​​the diaphragm wall, the foundation pit is excavated to a first preset elevation, and the first ring frame beam 1 is constructed, including:

[0077] The soil within the diaphragm wall area is excavated in layers and temporary supports are set up until the excavation depth reaches the first preset elevation. Then, the first concrete cushion layer is poured on the soil surface at the first preset elevation.

[0078] The reinforcement of the first ring beam 1 is tied on the first concrete cushion layer, and the first pouring pipe and the first reinforcement connector are installed on the reinforcement of the first ring beam 1.

[0079] Install the formwork for the first ring beam outside the reinforcing bars of the first ring beam 1, and pour concrete into the formwork for the first ring beam.

[0080] After the concrete poured inside the formwork of the first ring beam reaches the design strength, the formwork of the first ring beam is removed, and the construction of the first ring beam 1 is completed.

[0081] Specifically, such as Figure 1 and Figure 3As shown, during the construction of the first ring beam 1 within the diaphragm wall area, the soil within the diaphragm wall area is first excavated in layers according to the requirements of layered excavation of the shaft foundation pit. The excavation depth of each layer does not exceed 2m. Temporary supports are erected 50cm below the bottom of the design installation elevation of each temporary support. The principle of "excavating one step, supporting one step" is followed until the first preset elevation is reached. Then, the first concrete cushion layer is poured on the soil surface at the first preset elevation as the working surface for subsequent construction. Then, the reinforcement binding operation of the first ring beam 1 is carried out on the first concrete cushion layer. Reinforcement bars are planted on the surface of the diaphragm wall and tied to the reinforcement bars of the first ring beam 1 to form a whole. At the same time, pouring pipes that function as both pouring holes and venting holes for the lower side wall are installed on the reinforcement bars, and the first reinforcement connector for connection with the reinforcement bars of the lower side wall is reserved. Next, a suitable first ring frame beam formwork is installed and reinforced on the outside of the reinforcing bars of the first ring frame beam 1. Concrete is then poured into the first ring frame beam formwork. After a rebound test confirms that the concrete inside the first ring frame beam formwork has reached the design strength, the first ring frame beam formwork is removed, completing the construction of the first ring frame beam 1. In this embodiment, the temporary support is a steel support, the pouring pipe is a PVC pipe, and the first ring frame beam formwork is a 15mm thick plywood formwork. However, adjustments can be made according to the actual construction situation, and no specific limitations are made here.

[0082] In a preferred embodiment, excavation continues downward from the first preset elevation to the second preset elevation, followed by the construction of the second ring beam 2 and the construction of the first sidewall 3 between the first ring beam 1 and the second ring beam 2, including:

[0083] Continue excavating downwards from the first preset elevation to the second preset elevation, and pour a second concrete cushion layer on the soil surface at the second preset elevation.

[0084] Waterproofing work was carried out on the underground continuous wall between the second concrete cushion layer and the first ring frame beam 1;

[0085] The reinforcement of the second ring beam 2 is tied on the second concrete cushion layer, and the second pouring pipe and the second reinforcement connector are installed on the reinforcement of the second ring beam 2; at the same time, the reinforcement of the first side wall 3 is tied on the underground continuous wall between the first ring beam 1 and the second ring beam 2; and the reinforcement of the first side wall 3 is connected with the first reinforcement connector and the reinforcement of the second ring beam 2 into a whole.

[0086] Install the second ring beam formwork outside the reinforcement of the second ring beam 2, and install the first side wall formwork outside the reinforcement between the first ring beam 1 and the second ring beam 2.

[0087] Concrete was poured into the formwork of the second ring beam;

[0088] After the concrete poured into the formwork of the second ring beam reaches the design strength, concrete is poured into the formwork of the first side wall through the first pouring pipe on the first ring beam 1.

[0089] After the concrete poured into the first side wall formwork reaches the design strength, the second ring beam formwork and the first side wall formwork are removed, and the construction of the second ring beam 2 and the first side wall 3 are completed.

[0090] Specifically, such as Figure 1 and Figure 3 As shown, after the construction of the first ring beam 1 is completed, excavation continues downwards from the first preset elevation, following the principle of "excavating one step and supporting one step" at a time, in layers not exceeding 2m. Then, a second concrete cushion layer is poured on the soil surface at the second preset elevation as the working surface. Waterproofing is first completed on the diaphragm wall between the second concrete cushion layer and the first ring beam 1 (e.g., applying waterproofing agent, laying waterproof membrane, etc.). Next, the reinforcement binding of the second ring beam 2 and the first side wall 3 is carried out. Reinforcing bars are planted on the surface of the diaphragm wall and bound to the reinforcement of the second ring beam 2, forming a whole. The reinforcement of the first side wall 3 is tightly connected to the first reinforcement connector of the first ring beam 1 and the reinforcement of the second ring beam 2, forming a whole. Simultaneously, a second pouring pipe, functioning as both a pouring hole and a vent, is installed on the reinforcement of the second ring beam 2, and a second reinforcement connector is reserved for connection to the reinforcement of the lower structure of the second ring beam 2. Then, a dedicated 15mm thick plywood formwork is installed on the outside of the reinforcement of the second ring beam 2 as the formwork for the second ring beam. A polymer composite formwork is installed on the outside of the reinforcement of the first side wall 3 as the formwork for the first side wall. The first side wall formwork is reinforced using waterproof threaded rods in conjunction with φ48 steel pipes and No. 14 I-beams (No. 14 I-beams are used as secondary ribs, closely attached to the outside of the polymer composite formwork, arranged horizontally at 1m intervals; four φ48 steel pipes are installed on the outside of the secondary ribs as main ribs, arranged longitudinally; waterproof threaded rods are arranged in a staggered pattern at 0.6m intervals along the surface of the polymer composite formwork; one end of the waterproof threaded rod penetrates the polymer composite formwork and is anchored to the underground continuous wall retaining structure; the other end passes sequentially through the No. 14 I-beam secondary rib and the φ48 steel pipe main rib, and is then tightened with a nut). Next, concrete is poured into the second ring beam formwork. After the poured concrete reaches the design strength and is confirmed by rebound testing, concrete is poured into the first side wall formwork using the first pouring pipe pre-installed on the first ring beam 1. Finally, after the concrete poured for the first side wall 3 reaches the design strength, the formwork for the second ring beam and the first side wall is removed, thus completing this construction.

[0091] As can be seen, the overall integrity of the structure is ensured by integrally connecting the steel reinforcement of the second ring beam 2 and the first side wall 3 and pouring them in sequence. After construction, the second ring beam 2 and the first side wall 3 can serve as supporting structures for subsequent excavation of the foundation pit, laying the foundation for the rapid closure of the main structure of the shaft. In addition, Φ48 series galvanized disc-lock full-span bracing scaffolding can be used to assist in the construction of the first side wall 3, and the full-span bracing scaffolding can be removed after the construction of the first side wall 3 is completed.

[0092] In a preferred embodiment, the shaft foundation 5 includes a shaft base plate 51 and a third side wall 52. The construction of the shaft foundation 5 includes:

[0093] Using the soil at the bottom of the second ring beam 2 as the excavation surface, continue excavating downwards to the third preset elevation, and pour the third concrete cushion layer on the soil surface at the third preset elevation;

[0094] Waterproofing construction is carried out on the third concrete cushion layer, and on the surface of the third concrete cushion layer after the waterproofing construction is completed, the steel reinforcement binding construction of the shaft bottom plate 51, the installation construction of the shaft bottom plate formwork, and the concrete pouring construction of the shaft bottom plate 51 are carried out in sequence.

[0095] After the concrete poured inside the formwork of the shaft bottom slab reaches the design strength, the formwork of the shaft bottom slab is removed to complete the construction of shaft bottom slab 51.

[0096] Waterproofing construction, reinforcement binding construction of the third side wall 52, and installation construction of the third side wall formwork are carried out sequentially at the preset position on the underground continuous wall between the shaft bottom plate 51 and the second ring frame beam 2. Concrete is poured into the third side wall formwork through the second pouring pipe on the second ring frame beam 2. The preset position is determined according to the design specifications of the reserved shield tunneling channel 8.

[0097] After the concrete poured inside the formwork of the third side wall reaches the design strength, the formwork of the third side wall is removed and the third side wall 52 is backfilled using lateral support components, thus completing the construction of the shaft foundation 5.

[0098] Specifically, such as Figure 1 and Figure 3As shown, the shaft foundation 5 includes a shaft base slab 51 and a third side wall 52. Therefore, the construction of the shaft foundation 5 involves the sequential construction of the shaft base slab 51 and the third side wall 52. First, the soil at the bottom of the second ring beam 2 is excavated downwards to the third preset elevation. A third concrete cushion layer is poured on the surface of the soil at the third preset elevation as the working surface. Waterproofing is carried out on the third concrete cushion layer. Then, on the surface of the waterproofed third concrete cushion layer, the reinforcement binding of the shaft base slab 51 and the installation of the shaft base slab formwork are carried out sequentially. Subsequently, the base slab concrete is poured. After the concrete poured inside the shaft base slab formwork reaches the design strength and is confirmed by rebound testing, the shaft base slab formwork is removed, completing the construction of the shaft base slab 51.

[0099] Next, according to the design specifications of the reserved tunnel boring machine excavation channel 8, waterproofing construction and reinforcement binding of the third side wall 52 are completed sequentially at the preset positions within the portal ring range of the underground continuous wall between the shaft bottom slab 51 and the second ring frame beam 2. The reinforcement of the third side wall 52 is then firmly connected to the second reinforcement connector reserved in the second ring frame beam 2 to form an integral reinforcement structure. Next, a polymer composite formwork is installed on the outside of the reinforcement of the third side wall 52, and the formwork installation is carried out. The formwork is reinforced using a combination of waterproof threaded rods, φ48 steel pipes, and No. 14 I-beams. Then, concrete is poured into the third side wall formwork through the second pouring pipe (PVC pipe) reserved on the second ring frame beam 2. After the concrete poured into the third side wall formwork reaches the design strength, the formwork is removed, and lateral support components are used to backfill the third side wall 52 (lateral support for the third side wall 52) to prevent lateral deformation, thus completing the construction of the entire shaft foundation 5. In addition, the reinforced haunch angle serves as a transitional connection structure between the shaft bottom plate 51 and the third side wall 52. Its concrete must be poured integrally with the concrete of the shaft bottom plate 51 at one time to avoid construction joints and ensure the structural continuity and integrity of the two structures. Standardized steel formwork must be used for construction in this area.

[0100] In a preferred embodiment, the partially deepened foundation 6 includes a third ring frame beam 61, a partially deepened base plate 62, and a fourth side wall 63. The construction of the partially deepened foundation 6 includes:

[0101] With the soil at the bottom of the second ring beam 2 as the excavation surface, continue excavating downwards to the fourth preset elevation. On the soil surface at the fourth preset elevation, the subbase pouring construction, the reinforcement binding of the third ring beam 61, the installation of the third pouring pipe and the third reinforcement connector, the installation of the third ring beam formwork, and the pouring of concrete into the third ring beam formwork are carried out in sequence.

[0102] After the concrete poured inside the formwork of the third ring beam reaches the design strength, the formwork of the third ring beam is removed to obtain the third ring beam 61.

[0103] Continue excavating downwards from the fourth preset elevation to the fifth preset elevation. On the soil surface at the fifth preset elevation, carry out the following construction steps in sequence: pouring of the cushion layer, waterproofing, binding of the reinforcing bars for locally deepening the bottom slab 62, installation of the formwork for locally deepening the bottom slab, and pouring of concrete for locally deepening the bottom slab 62.

[0104] After the concrete poured inside the partially deepened base slab formwork reaches the design strength, the partially deepened base slab formwork is removed, and the construction of the partially deepened base slab 62 is completed.

[0105] Waterproofing construction, reinforcement binding construction of the fourth side wall 63, and installation construction of the fourth side wall formwork are carried out sequentially for the underground continuous wall between the locally deepened bottom slab 62 and the third ring frame beam 61. Concrete is poured into the fourth side wall formwork through the third pouring pipe on the third ring frame beam 61.

[0106] After the concrete poured inside the fourth side wall formwork reaches the design strength, the fourth side wall formwork is removed, and the construction of the locally deepened foundation 6 is completed.

[0107] Specifically, such as Figure 1 and Figure 3As shown, since the locally deepened base 6 includes the third ring frame beam 61, the locally deepened bottom plate 62 and the fourth side wall 63, the construction of the locally deepened base 6 includes the construction of the third ring frame beam 61, the construction of the locally deepened bottom plate 62 and the construction of the fourth side wall 63 in sequence. First, using the soil at the bottom of the second ring beam 2 as the excavation surface, the excavation continues downward to the fourth preset elevation, following the principle of "excavating one step and supporting one step" and no more than 2m of depth in the layered excavation of the vertical shaft foundation pit. At the fourth preset elevation, a concrete cushion layer is first poured on the soil surface as the working surface. Then, based on the reinforcement of the underground continuous wall, the reinforcement binding construction of the third ring beam 61 is carried out. At the same time, a third pouring pipe (PVC pipe) with both pouring and venting functions and a third reinforcement connector for subsequent reinforcement connection are installed on the reinforcement. Then, a 15mm plywood formwork is installed as the formwork for the third ring beam and reinforced. Concrete is poured into the formwork of the third ring beam. After the concrete in the formwork of the third ring beam reaches the design strength and is confirmed by rebound testing, the formwork of the third ring beam is removed, thus forming the shaped third ring beam 61. Next, continue excavating downwards along the fourth preset elevation to the fifth preset elevation according to the same excavation principle. At this elevation, the concrete cushion layer is poured, waterproofing is carried out, the reinforcement binding of the locally deepened base slab 62 is completed, and the concrete of the locally deepened base slab 62 is poured in sequence. After the concrete in the locally deepened base slab formwork reaches the design strength, the locally deepened base slab formwork is removed to complete the construction of the locally deepened base slab 62. Subsequently, waterproofing construction and reinforcement binding construction of the fourth side wall 63 were completed sequentially on the surface of the underground continuous wall between the locally deepened base slab 62 and the third ring frame beam 61. The reinforcement of the fourth side wall 63 was then firmly connected to the third reinforcement connector reserved in the third ring frame beam 61 to form an integral reinforcement structure. Then, a polymer composite formwork was installed as the formwork for the fourth side wall, and it was reinforced by a combination of waterproof threaded rods, φ48 steel pipes and No. 14 I-beams. Concrete was poured into the fourth side wall formwork through the third pouring pipe reserved in the third ring frame beam 61. After the concrete in the fourth side wall formwork reached the design strength, the formwork was removed, and the construction of the entire locally deepened base 6 was completed.

[0108] In a preferred embodiment, the vertical support member 4 is a steel column, which is spaced out at the corners of the top surface of the locally deepened base 6 to avoid the tunneling passage 8 of the tunnel boring machine.

[0109] Specifically, such as Figure 4 As shown, the vertical support member 4 is a steel column. The steel column is made of hot-rolled wide-flange H-beams with a steel grade of Q355B. It is arranged at intervals at the corners of the top surface of the locally deepened base 6, with a total of 8 columns. Four columns are set on each side of the tunnel boring machine tunneling channel 8. The spacing between the steel columns is 3m.

[0110] In a preferred embodiment, using the vertical support member 4 and the first side wall 3 as construction supports, all remaining side walls and ring frame beams of the main shaft structure are continuously constructed from bottom to top until the main shaft structure is closed at the top, including:

[0111] S501. Using the locally deepened base plate 62 as the starting reference plane for scaffolding erection, when the scaffolding is erected to the preset construction position of each floor, waterproofing construction, tying construction of the ring beam and side wall reinforcement, installation construction of the ring beam formwork and side wall formwork, and concrete pouring construction of the ring beam and side wall are carried out in sequence.

[0112] S502. When the concrete of each ring frame beam and the side wall reaches the design strength, remove the formwork of the ring frame beam and the side wall, and use lateral support components to back the side wall until the construction of the ring frame beam and side wall of the top layer of the main structure of the shaft is completed, so as to realize the closure of the main structure of the shaft at the top.

[0113] Specifically, such as Figure 3 and Figure 2 As shown, after the construction of vertical support component 4 is completed, the remaining three layers of side walls and ring frame beams are continuously constructed from bottom to top, relying on the support system formed by vertical support component 4 and the first side wall 3. Using the locally deepened base plate 62 as the starting reference surface for scaffolding erection, φ48 series galvanized disc-lock full-span bracing scaffolding is erected. When the scaffolding reaches the preset construction position of each of the upper three layers, waterproofing construction is first carried out on the corresponding underground continuous wall, followed by simultaneous reinforcement binding of the ring frame beam and side wall of that layer, and then simultaneous pouring of the ring frame beam and side wall of that layer. After the concrete of each layer of ring frame beam and side wall reaches the design strength and is confirmed by rebound testing, the formwork of the corresponding layer of ring frame beam and side wall is removed. Then, lateral support components are used to back up the side walls, and the remaining three layers of side walls and ring frame beams are constructed layer by layer upwards according to this process, until the construction of the ring frame beam and side wall of the top layer of the main shaft structure is completed, ultimately achieving the closure of the main shaft structure at the top.

[0114] The construction method for partially deepened open-cut shafts provided by this invention combines forward (bottom-up) and reverse (top-down) construction methods. First, the reverse method is used to complete the construction of the ring beams (first and second ring beams) above the shaft foundation, the side walls (first side wall), the shaft foundation, the partially deepened foundation, and the vertical support components to construct a stable foundation support system. Then, the forward method is used to complete the closure of the main shaft structure from bottom to top, ensuring that the pit sidewalls remain effectively supported throughout the construction of the main shaft structure. Finally, the remaining second sidewalls in the partially deepened area are constructed, completing the construction of the entire shaft structure. This combined forward and reverse construction method solves the technical problems of delayed shaft closure, excessive pit exposure time, and significant safety hazards in traditional partially deepened open-cut shaft construction. Furthermore, the traditional sequential construction method requires the installation of temporary support beams at the excavated but unconstructed sidewall locations, which are then removed during sequential construction to the corresponding beam positions. In contrast, this invention directly casts a ring-frame beam as a permanent support structure, eliminating the need for beam removal and effectively increasing construction speed. Simultaneously, addressing the challenges of asynchronous sidewall construction and rapid sidewall closure caused by locally deepened pits in the traditional sequential construction method, this invention optimizes the construction sequence and support system, achieving simultaneous progress and rapid closure of sidewall construction, further enhancing construction safety and efficiency.

[0115] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be noted that due to the limitations of textual expression, and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A construction method for locally deepening open-cut vertical shafts, characterized in that, The locally deepened open-cut shaft adopts a layered excavation method, which includes: S1. Construct diaphragm walls within the shaft construction area to form a shaft pit retaining system; S2. Within the range of the underground continuous wall, the foundation pit is excavated to the first preset elevation, and the first ring frame beam (1) is constructed; and the excavation continues downward along the first preset elevation to the second preset elevation, and the second ring frame beam (2) is constructed, and the first side wall (3) is constructed between the first ring frame beam (1) and the second ring frame beam (2); S3. With the soil at the bottom of the second ring beam (2) as the excavation surface, construct the shaft foundation (5) and the locally deepened foundation (6) to form the shaft foundation (5) and the locally deepened foundation (6). The shaft foundation (5) includes a shaft base plate (51) and a third side wall (52). The construction of the shaft foundation (5) includes: Using the soil at the bottom of the second ring beam (2) as the excavation surface, continue excavating downwards to the third preset elevation, and pour the third concrete cushion layer on the soil surface at the third preset elevation; Waterproofing construction is carried out on the third concrete cushion layer, and the reinforcement binding construction of the shaft bottom plate (51), the installation construction of the shaft bottom plate formwork and the concrete pouring construction of the shaft bottom plate (51) are carried out in sequence on the surface of the third concrete cushion layer after the waterproofing construction is completed. After the concrete poured into the formwork of the shaft bottom plate reaches the design strength, the formwork of the shaft bottom plate is removed to complete the construction of the shaft bottom plate (51); Waterproofing construction, reinforcement binding construction of the third side wall (52), and installation construction of the formwork of the third side wall are carried out in sequence at the preset position on the underground continuous wall between the bottom plate (51) of the shaft and the second ring frame beam (2). Concrete is poured into the formwork of the third side wall through the second pouring pipe on the second ring frame beam (2). The preset position is determined according to the specifications of the reserved shield tunneling channel (8). After the concrete poured into the formwork of the third side wall reaches the design strength, the formwork of the third side wall is removed and the third side wall (52) is backed up using lateral support components to complete the construction of the shaft foundation (5). The locally deepened base (6) includes a third ring frame beam (61), a locally deepened base plate (62), and a fourth side wall (63). The construction of the locally deepened base (6) includes: With the soil at the bottom of the second ring beam (2) as the excavation surface, continue excavating downwards to the fourth preset elevation. On the soil surface at the fourth preset elevation, the subbase pouring construction, the reinforcement binding of the third ring beam (61), the installation of the third pouring pipe and the third reinforcement connector, the installation of the third ring beam formwork, and the pouring of concrete into the third ring beam formwork are carried out in sequence. After the concrete poured into the formwork of the third ring beam reaches the design strength, the formwork of the third ring beam is removed to obtain the third ring beam (61). Continue excavating downwards from the fourth preset elevation to the fifth preset elevation. On the soil surface at the fifth preset elevation, perform the following in sequence: cushion layer pouring, waterproofing, reinforcement binding of the partially deepened bottom slab (62), installation of the partially deepened bottom slab formwork, and concrete pouring of the partially deepened bottom slab (62). After the concrete poured inside the partially deepened base plate formwork reaches the design strength, the partially deepened base plate formwork is removed to complete the construction of the partially deepened base plate (62); Waterproofing construction, reinforcement binding construction of the fourth side wall (63), and installation construction of the fourth side wall formwork are carried out sequentially on the underground continuous wall between the locally deepened bottom slab (62) and the third ring frame beam (61), and concrete is poured into the fourth side wall formwork through the third pouring pipe on the third ring frame beam (61). After the concrete poured into the fourth side wall formwork reaches the design strength, the fourth side wall formwork is removed to complete the construction of the locally deepened foundation (6). S4. A vertical support member (4) is provided between the top surface of the locally deepened base (6) and the bottom surface of the second ring beam (2). S5. Using the vertical support member (4) and the first side wall (3) as construction supports, continuously construct all remaining side walls and ring frame beams of the main structure layer of the shaft from bottom to top until the main structure of the shaft is closed at the top. Using the vertical support member (4) and the first side wall (3) as construction supports, the remaining side walls and ring frame beams of the main structure layer of the shaft are continuously constructed from bottom to top until the main structure of the shaft is closed at the top, including: S501. Using the locally deepened base plate (62) as the starting reference plane for scaffolding erection, when the scaffolding is erected to the preset construction position of each floor, waterproofing construction, tying construction of the ring beam and side wall reinforcement, installation construction of the ring beam formwork and side wall formwork, and concrete pouring construction of the ring beam and side wall are carried out in sequence. S502. When the concrete of the ring frame beam and the side wall of each layer reaches the design strength, the formwork of the ring frame beam and the side wall are removed, and the side wall is backfilled with lateral support components until the construction of the ring frame beam and side wall of the top layer of the main structure of the shaft is completed, so as to realize the closure of the main structure of the shaft at the top. S6. After the main structure of the shaft is closed, the second side wall (7) is constructed between the top surface of the locally deepened base (6) and the bottom surface of the second ring beam (2) to complete the construction of the locally deepened open-cut shaft.

2. The construction method for locally deepened open-cut shafts according to claim 1, characterized in that, Before step S6, the method further includes: sealing the bottom of the locally deepened base (6), wherein the top surface elevation of the locally deepened base (6) after sealing is equal to the bottom surface elevation of the shaft base (5).

3. The construction method for locally deepened open-cut shafts according to claim 2, characterized in that, The bottom sealing process includes: The interior of the locally deepened base (6) is filled with sand in layers and compacted. A steel plate is laid on the top surface of the sand filling layer to seal the locally deepened base (6); A concrete cover plate is poured on top of the steel plate so that the top surface elevation of the locally deepened base (6) is flush with the bottom surface elevation of the shaft base (5).

4. The construction method for locally deepened open-cut shafts according to claim 1, characterized in that, Within the range of the underground continuous wall, the foundation pit is excavated to the first preset elevation, and the construction of the first ring frame beam (1) is carried out, including: The soil within the range of the underground continuous wall is excavated in layers and temporary supports are set up until the excavation depth reaches the first preset elevation. Then, the first concrete cushion layer is poured on the soil surface at the first preset elevation. The reinforcement of the first ring beam (1) is tied on the first concrete cushion layer, and the first pouring pipe and the first reinforcement connector are installed on the reinforcement of the first ring beam (1). Install the first ring frame beam formwork outside the reinforcement of the first ring frame beam (1), and pour concrete into the first ring frame beam formwork; After the concrete poured into the first ring frame beam formwork reaches the design strength, the first ring frame beam formwork is removed to complete the construction of the first ring frame beam (1).

5. The construction method for locally deepened open-cut shafts according to claim 4, characterized in that, Continue excavating downwards from the first preset elevation to the second preset elevation, and carry out the construction of the second ring frame beam (2) and the construction of the first side wall (3) between the first ring frame beam (1) and the second ring frame beam (2), including: Continue excavating downwards from the first preset elevation to the second preset elevation, and pour a second concrete cushion layer on the soil surface at the second preset elevation; Waterproofing work is carried out on the underground continuous wall between the second concrete cushion layer and the first ring frame beam (1); The reinforcement of the second ring beam (2) is tied on the second concrete cushion layer, and the second pouring pipe and the second reinforcement connector are installed on the reinforcement of the second ring beam (2); the reinforcement of the first side wall (3) is tied on the underground continuous wall between the first ring beam (1) and the second ring beam (2); and the reinforcement of the first side wall (3) is connected to the first reinforcement connector and the reinforcement of the second ring beam (2) into a whole. Install the second ring frame beam template outside the reinforcement of the second ring frame beam (2), and install the first side wall template outside the reinforcement between the first ring frame beam (1) and the second ring frame beam (2); Concrete was poured into the formwork of the second ring beam; After the concrete poured into the second ring frame beam template reaches the design strength, concrete is poured into the first side wall template through the first pouring pipe on the first ring frame beam (1). After the concrete poured into the first side wall formwork reaches the design strength, the second ring beam formwork and the first side wall formwork are removed to complete the construction of the second ring beam (2) and the first side wall (3).

6. The construction method for locally deepened open-cut shafts according to claim 1, characterized in that, The vertical support member (4) is a steel column, which is spaced out at the corners of the top surface of the locally deepened base (6) to avoid the tunneling passage (8) of the tunnel boring machine.

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