An L-shaped half-cover excavation construction method suitable for a crossroad subway station

Abstract

The application discloses a kind of L-shaped half-cover excavation construction methods suitable for crossroad subway station, including excavation construction process and removal construction process, excavation construction process uses open cut method to be made open cut area on the side of main road of crossroad subway station, and cover excavation method is made cover excavation area on the side of secondary road, open cut area and cover excavation area are excavated alternately layer by layer, removal construction process is alternately removed layer by layer, finally form L-shaped foundation pit;The method will be excavated with the reduction of ground influence of cover excavation Construction is a clever combination, is conducive to the up and down of slag, equipment and personnel, open cut and blind excavation operation do not affect each other, improve the efficiency of foundation pit construction, while also reducing the impact on road traffic;L-shaped foundation pit is attached to crossroad design, and the land area is small and can flexibly adjust road distribution;The method has high economy, scientificity and reproducibility, and has good guiding significance for the construction of crossroad subway station.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering technology, specifically relating to an L-shaped semi-cut-and-cover construction method suitable for subway stations at intersections. Background Technology

[0002] With the continuous development of urban economy, urban transportation will also face great challenges. As a result, subways have become a favorite of modern large cities. The construction of subways can not only greatly alleviate the traffic pressure of densely populated cities, but also enhance the city's comprehensive competitiveness through the upgrading of surface transportation and the transformation of underground space.

[0003] Finding a suitable balance between various conditions and the construction needs of multiple subway stations requires selecting an appropriate construction method. Currently, common subway station construction methods include cut-and-cover and top-and-bottom methods. While the cut-and-cover method is low-cost and convenient, its large land area significantly impacts road traffic. On the other hand, the top-and-bottom method reduces the impact on road traffic, but the enclosed roof makes it difficult for underground excavated soil, equipment, and construction personnel to move in and out, causing inconvenience and greatly affecting construction efficiency.

[0004] This shows that existing subway station construction methods cannot simultaneously address the issues of minimizing the impact on road traffic and facilitating construction. Summary of the Invention

[0005] To overcome the above-mentioned technical defects, the present invention provides an L-shaped semi-cut-and-cover construction method suitable for subway stations at intersections, which can solve the technical problem that existing subway station construction methods cannot simultaneously reduce the impact on road traffic and facilitate construction.

[0006] To achieve the above objectives, the present invention employs the following technical content:

[0007] A method for constructing an L-shaped semi-cut-and-cover subway station at an intersection includes: an excavation process and a demolition process;

[0008] The excavation process includes:

[0009] The open-cut area is constructed using the cut-and-cover method on the side of the subway station near the main road of the intersection, while the cut-and-cover area is constructed using the cut-and-cover method on the side of the subway station near the secondary road of the intersection. The open-cut area and the cut-and-cover area are excavated in a multi-layered structure, and the open-cut area is excavated layer by layer in the order of first the cut-and-cover area and then the cut-and-cover area, with support construction carried out simultaneously until the bottom slab of the open-cut area is completed.

[0010] The demolition process includes:

[0011] When the cut-and-cover area and the cut-and-cover area reach the preset demolition conditions, the supports are removed layer by layer in the order of first the cut-and-cover area and then the cut-and-cover area, until the top slab of the cut-and-cover area is backfilled with soil; finally, the cut-and-cover area and the cut-and-cover area form an L-shaped foundation pit.

[0012] Furthermore, it also includes the construction preparation process carried out before the excavation construction process, the specific steps of which are as follows:

[0013] Construction barriers were erected in the area to be constructed; traffic diversion at the intersection was completed by moving the secondary road in the opposite direction of the foundation pit.

[0014] Furthermore, the steps for setting up construction barriers in the area to be constructed include:

[0015] The green space and part of the road surface were demolished, and retaining piles, mixing piles, column piles, capping beams and Larssen steel sheet piles were constructed.

[0016] Furthermore, construction barriers were first set up in the direction of the secondary arterial road, and then in the direction of the main arterial road.

[0017] Furthermore, while traffic diversion is being carried out at the intersection, a temporary military bridge is set up on one side of the secondary road at the intersection to temporarily expand the secondary road into a lane for non-motorized vehicles and emergency use.

[0018] Furthermore, column piles were erected at the bottom of the military bridge and driven deep into the underground rock mass.

[0019] Furthermore, the specific steps of the excavation process are as follows:

[0020] Step 1: Excavate the first basement level of the open-cut area, erect the first support for the open-cut area, and apply wire mesh and spray concrete between the columns;

[0021] Step 2: Excavate the cut-and-cover area to the design elevation of the cut-and-cover roof slab and simultaneously erect the first support for the underground excavation area;

[0022] Step 3: Continue open excavation of the first basement level, erect the second support in the open excavation area, and apply wire mesh and spray concrete between the columns;

[0023] Step 4: Construct the capping beam under the top slab of the cut-and-cover area;

[0024] Step 5: Excavate the first basement level of the cut-and-cover area and erect the second support for the cut-and-cover area;

[0025] Step Six: Continue excavation in the open-cut area to the second basement level and erect the third support for the open-cut area;

[0026] Step 7: Excavate the cut-and-cover area to the design elevation of the pit bottom at level 2 and erect the third support for the cut-and-cover area;

[0027] Step 8: Excavate the open-cut area to the design elevation of the pit bottom 3 layers and erect the fourth support for the open-cut area.

[0028] Furthermore, in step five, before excavating and covering the first basement level, once the concrete strength of the top slab reaches the design strength, the secondary road that was relocated during the construction preparation process is restored to its original road surface, and the secondary road is upgraded from the original two-in-two-out to three-in-three-out.

[0029] Furthermore, after the open-cut and cut-and-cover areas are excavated to the design elevation of the pit bottom, grounding grids, bottom slab cushions, waterproof layers, bottom slabs, bottom longitudinal beams, and side wall structures are constructed for the open-cut and cut-and-cover areas respectively.

[0030] Furthermore, the specific steps of the demolition process are as follows:

[0031] Step 1: After the cut-and-cover 2nd basement level reaches the design strength, remove the third support in the cut-and-cover area;

[0032] Step 2: After the bottom slab of the third basement level of the open-cut excavation reaches the design strength, remove the fourth support in the open-cut area;

[0033] Step 3: After the cut-and-cover basement slab reaches the design strength, remove the second layer of support in the cut-and-cover area;

[0034] Step 4: After the bottom slab of the second basement level of the open-cut excavation reaches the design strength, remove the third support in the open-cut area;

[0035] Step 5: Continue construction upwards and dismantle the remaining support structure in the cut-and-cover area;

[0036] Step 6: After the bottom slab of the open-cut basement reaches the design strength, remove the second support of the open-cut area A, and at the same time construct the top slab structure of the open-cut basement.

[0037] Step 7: After the top slab structure of the open-cut basement reaches the design strength, remove the first support, apply the waterproof layer and concrete protective layer, and backfill the top slab of the open-cut area with soil.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] This invention provides an L-shaped semi-cut-and-cover construction method suitable for subway stations at intersections. The method includes excavation and demolition processes. The excavation process involves using the open-cut method to construct the open-cut area on the side of the subway station closest to the main road of the intersection, and the cut-and-cover area on the side of the secondary road. The open-cut and cut-and-cover areas are excavated alternately layer by layer, and the demolition process involves alternating demolition layer by layer, ultimately forming an L-shaped foundation pit. This method cleverly combines the convenience of open-cut construction with the reduced impact on the ground surface of cut-and-cover, facilitating the movement of excavated soil, equipment, and personnel. The open-cut and cut-and-cover operations do not interfere with each other, improving the efficiency of foundation pit construction while minimizing the impact on road traffic. The L-shaped foundation pit is designed to fit snugly against the intersection, occupying a small area and allowing for flexible adjustments to the road surface distribution. This method reduces the need for road and pipeline relocation by half, exhibiting high economic efficiency, scientific rigor, and replicability, and providing valuable guidance for the construction of subway stations at intersections.

[0040] Preferably, in this invention, while diverting traffic at the intersection, a temporary military bridge is also installed on one side of the secondary road at the intersection to temporarily expand the secondary road into a non-motorized vehicle lane and an emergency lane. The installation of the temporary military bridge can make room for additional road space in the city, improve traffic flow speed, and ensure smooth road traffic.

[0041] More preferably, in this invention, column piles are erected at the bottom of the military temporary beam and driven deep into the underground rock mass; the column piles also serve as pull-out piles, providing stable and reliable support for the top slab of the cut-and-cover area. Under the protection of the column piles and the top slab, excavation can proceed to the design elevation of the pit bottom, enabling the construction of the main structure such as the bottom slab, side walls, and middle slab. This is a prerequisite for realizing the semi-reverse construction method of cut-and-cover. At the same time, this will also directly affect the traffic diversion plan. The secondary fixing effect provided by the column piles for the military temporary beam will effectively ensure the safety of the temporary expansion lane.

[0042] Preferably, in this invention, once the concrete strength of the top slab reaches the design strength, the secondary road that was moved during the construction preparation process is restored to its original road surface, and the secondary road is upgraded from the original two-in-two-out to three-in-three-out. While completing the overall construction of the foundation pit, the traffic at the intersection is also upgraded, thus achieving a further upgrade of the urban hub. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the overall structure of an L-shaped semi-cut-and-cover construction method for subway stations at intersections, provided by an embodiment of the present invention.

[0044] Figure 2 The following is a traffic diagram of an intersection provided for an embodiment of the present invention, wherein (a) is a schematic diagram of the original traffic situation of the intersection before construction; and (b) is a schematic diagram of traffic diversion at the intersection during construction.

[0045] Figure 3 A schematic diagram of the plan layout for erecting a simple military-style temporary beam provided in an embodiment of the present invention;

[0046] Figure 4 The diagram shows the structure of the military pontoon beam provided in the embodiment of the present invention, wherein (a) is an overall view and (b) is a partial enlarged view of (a);

[0047] Figure 5 This is a schematic diagram of the plan layout of the L-shaped foundation pit retaining structure provided in an embodiment of the present invention;

[0048] Figure 6 for Figure 5 Cross-sectional view at point AA;

[0049] Figure 7 for Figure 5 Cross-sectional view at point BB;

[0050] Figure 8 for Figure 5 Cross-sectional view at point CC;

[0051] Figure 9 This is a schematic diagram of the plan layout of the L-shaped foundation pit support structure provided in an embodiment of the present invention;

[0052] Figure label:

[0053] Open-cut zone -1; Cut-and-cover zone -2; Temporary support zone -3;

[0054] Open-cut -1 level -1-1; Open-cut -2 level -1-2; Open-cut -3 level -1-3; Cut-and-cover -1 level -2-1; Cut-and-cover -2 level -2-2;

[0055] Military temporary beam - 3-1; Spiral knob - 3-2; Double plywood - 3-3; Post pile - 3-4; Fence - 3-5;

[0056] Phase 1 construction enclosure - 4-1; Phase 2 construction enclosure - 4-2. Detailed Implementation

[0057] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0058] 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. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0059] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0060] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0061] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0062] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0063] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0064] The present invention will now be described in further detail with reference to the accompanying drawings:

[0065] Example

[0066] As mentioned in the background section, common construction methods for subway stations include open-cut and cut-and-cover methods. While open-cut methods are low-cost and convenient, their large footprint significantly impacts road traffic. Cut-and-cover methods, while reducing traffic disruption, hinder the movement of excavated soil, equipment, and personnel after the roof is sealed, causing inconvenience and significantly reducing construction efficiency. Although some subway station construction combines open-cut and cut-and-cover methods, this simple approach cannot completely solve the problems. Instead, it increases the horizontal and vertical construction site area and the amount of pipeline relocation, making widespread adoption difficult.

[0067] To address the aforementioned technical issues, this embodiment provides an L-shaped semi-cut-and-cover construction method suitable for subway stations at intersections. This method is applicable to subway construction at urban transportation hubs, simultaneously upgrading road traffic during subway station construction, aiming to solve current pain points, and possesses a certain degree of universality. Using this method, not only can the construction of the subway station foundation pit be accelerated, but secondary roads can also be expanded into main roads without affecting road traffic, further upgrading the urban sub-intersection center area. This method combines the advantages of both open-cut and cut-and-cover methods, improving construction efficiency and reducing construction time and economic costs.

[0068] The present invention will now be explained in detail with reference to the accompanying drawings and embodiments:

[0069] like Figure 1 As shown, the foundation pit is first pre-divided into open excavation area 1 and cut-and-cover area 2. The subsequent construction can be roughly described as follows: first, the soil in the open excavation area 1-1 of the first basement level is excavated, and then the soil in the cut-and-cover area 2-1 of the first basement level is excavated. This process is repeated back and forth until the excavation of the open excavation area 1-3 of the third basement level is completed and the bottom slab construction is finished. Then, the construction is carried out in reverse order. First, the support in the cut-and-cover area 2-2 of the second basement level is removed, and then the support in the open excavation area 1-3 of the third basement level is removed and the relevant structures are constructed. This process continues until the open excavation area 1-1 of the first basement level is backfilled, and finally, the construction of the entire L-shaped foundation pit is completed.

[0070] Specifically, this embodiment provides an L-shaped semi-cut-and-cover construction method suitable for subway stations at intersections, dividing the main body of the construction area into two areas, namely the open-cut area 1 and the cut-and-cover area 2. The specific steps are as follows:

[0071] Step 1: As Figure 1As shown, the L-shaped foundation pit is pre-divided into two areas: an open-cut zone 1 primarily using cut-and-cover construction techniques and a cut-and-cover zone 2 primarily using top-and-bottom construction techniques. A first-phase construction enclosure 4-1 is installed. Specifically, the enclosure is installed 3 meters from the widened end of the pit near the main road, and 2 meters from the pit near the secondary road. This is the layout of the first-phase construction enclosure 4-1. Green spaces and parts of the road surface are demolished, and retaining piles, mixing piles, columns that also act as tension piles, capping beams, and Larssen sheet piles are constructed at the corresponding locations. However, under the same conditions, priority is given to constructing the enclosure for the bottom layer -2-1 of the top-and-bottom construction, in preparation for subsequent step three.

[0072] Step Two: As Figure 2 As shown in (1) and (2) in the figure, the first round of traffic diversion in the central area of ​​the crossroads begins. As can be seen from the figure, this traffic diversion temporarily includes part of the original secondary road into the construction scope of the excavation and cover area 2. The secondary road is moved in the opposite direction of the foundation pit, while still maintaining two lanes in and two lanes out.

[0073] Step 3: As Figure 3 As shown, in the cut-and-cover area 2, near the edge of the secondary road at the intersection, a simple military-style beam 3-1 is erected using a spiral knob 3-2 and double clamps 3-3. Figure 3 In the middle, the temporary support area 3 is the area occupied by the military temporary beam 3-1. The purpose is to temporarily expand the secondary road with another lane as a non-motorized vehicle lane and emergency lane. For this reason, it is necessary to make appropriate adjustments to the first phase construction enclosure 4-1.

[0074] In this embodiment, Figure 4 (a) shows the overall layout of the temporary bridge 3-1, and (b) shows a detailed view of a section of the temporary bridge 3-1. Here, the temporary bridge 3-1 can be understood as a truss bridge. The overall layout uses the spiral knobs 3-2 driven into the road surface as the main fixing points, and the double-clamped plates 3-3 and the column piles 3-4 as secondary fixing points to maintain overall stability. In addition, a fence 3-5 is added to the temporary bridge 3-1 to replace part of the first-phase construction fence 4-1. The actual width of the auxiliary road is the same as the normal road lane width, primarily for non-motorized vehicle use, but can also be used as an emergency lane.

[0075] Step Four: As Figure 5 As shown, the excavation involves the open-cut level 1-1, with the first temporary support erected in the open-cut area, and shotcrete applied between the columns. In this embodiment, the main retaining structure of the station adopts a retaining structure of bored piles + internal supports + shotcrete between the piles, with a design safety level of Level 1. The design service life of the foundation pit is 2 years, and the monitoring level of the foundation pit is Level 1.

[0076] Step 5: When the excavation of the cut-and-cover area 2 reaches 0.5 meters below the temporary support of the semi-reverse roof slab from top to bottom, temporary steel support is installed, which is the first support of the cut-and-cover area. Excavation continues to the design elevation of the bottom surface of the cut-and-cover roof slab.

[0077] Step 6: Continue excavating the open-cut layer 1-1, excavating in layers, setting up the second support in the open-cut area, and applying sprayed concrete with wire mesh between the columns.

[0078] Step 7: In the cut-and-cover area 2, remove the retaining piles on both sides to 0.1m below the bottom surface of the cut-and-cover top slab and construct the capping beam. Pour the plain concrete cushion layer, the cut-and-cover structure top slab, the top longitudinal beam, and the columns. Lay the waterproof layer of the top slab and the fine stone concrete protective layer.

[0079] Step 8: After the concrete strength of the excavated and cut-off top slab reaches the design strength, remove the military temporary beam 3-1, relocate the pipelines, dismantle the sheet piles and temporary supports, backfill with soil, break down part of the enclosure and set up the second-phase construction enclosure 4-2, and restore the original road surface. Remove the plain concrete cushion layer under the excavated and cut-off slab, and then excavate the excavated and cut-off sub-level 1 2-1 from top to bottom in layers to 0.5m below the second support of the cut-off area, and erect the second support of the cut-off area; at this time, carry out the final traffic diversion, upgrading the secondary road from the original two-in-two-out to three-in-three-out.

[0080] Step 9: Continue excavating in open-cut area 1 to the second basement level 1-2, and set up the third support for the open-cut area as you excavate.

[0081] Step 10: Continue excavating the foundation pit at level 2-2 (cover and cut) to 0.5m below the third support in the cover and cut area, and erect the third support in the cover and cut area; continue excavating to the design elevation of the pit bottom, construct the bottom slab cushion layer, the bottom slab waterproof layer, the grounding grid, the structural bottom slab, and the bottom longitudinal beams. After the foundation pit is excavated to the design elevation, promptly arrange for the construction of the grounding grid and the sealing of the cushion layer with concrete. Prolonged exposure of the foundation base is not permitted to prevent softening of the foundation soil. The reinforced concrete structure of the bottom slab should be completed in the shortest possible time. Only after the reinforced concrete of the bottom slab reaches a certain strength can the safety of the foundation pit be truly guaranteed.

[0082] Step 11: Continue excavating the open-cut third level (1-3) to the design elevation of the pit bottom, setting up the fourth support in the open-cut area as excavation progresses. Install the grounding grid, the base slab bedding layer, lay the waterproof layer, and construct the base slab, bottom longitudinal beams, and part of the side wall structure.

[0083] Step 12: After the 2-2 basement slab of the cut-and-cover section reaches its design strength, remove the third layer of support in the cut-and-cover area. Properly manage the relationship between support removal and structural concrete construction, and strictly control the support removal time according to design requirements during construction.

[0084] Step Thirteen: After the concrete reaches 90% of the design strength in the open-cut third basement level 1-3, remove the fourth support in the open-cut area, lay the waterproof layer for the side walls, and construct the side walls, platform level columns, and central floor slab structure.

[0085] Step Fourteen: Continue construction upwards in cut-and-cover area 2. After the bottom slab of the cut-and-cover basement 1 reaches the design strength, remove the second support in the cut-and-cover area.

[0086] Step 15: After the slab of the second basement level of the open-cut section reaches 90% of the design strength, remove the third support in the open-cut area, lay the waterproof layer for the side walls, and construct the side walls, the central columns of the station hall, and the roof structure.

[0087] Step 16: Continue construction upwards on the remaining side walls, central columns, and side walls of the excavation and cover area 2.

[0088] Step 17: Similarly, remove the second support in the open-cut area and construct the 1-1 top slab structure of the first basement level of the open-cut area.

[0089] Step 18: As Figure 8 As shown, the column piles 3-4 of the cut-and-cover area 2 are removed to complete the construction of the cut-and-cover area 2. The overall construction adopts a semi-reverse cut-and-cover method.

[0090] Step Nineteen: As Figure 6 and Figure 7 As shown, after the concrete of the top slab of the 1-1 level of the open-cut sub-base reaches 100% of the design strength, the first support in the open-cut area is removed, a waterproof layer and a concrete protective layer are applied, the retaining wall above the cap beam is removed and backfilled with soil, and the construction of the open-cut area 1 is completed.

[0091] Step 20: Remove the second phase construction enclosure 4-2, restore the ground, and construct the remaining structure inside the station.

[0092] The main foundation pit retaining structure consists of φ1000mm bored cast-in-place piles, with 1000×1400mm capping beams at the pile tops. An internal support system is installed within the pit, with a maximum of four vertical internal supports. The first support is a concrete support (800×1000mm), spaced 7m–9m apart. The second, third, and fourth supports are steel supports (Φ609, t=16mm), spaced 2.3m–3.5m apart. The steel walers use double-jointed 452 steel. A Φ6@150×150mm steel mesh is used between the retaining piles, and 100mm thick 325 concrete is sprayed over it. Fixed reinforcing bars and horizontal Φ16@1000 reinforcing bars ensure a reliable connection between the steel mesh and the main reinforcement of the retaining piles. Figure 9 As shown, Figure 9 The planar layout of steel supports for part of the L-shaped foundation pit.

[0093] Preferably, in step one, the open-cut area adopts a three-story, double-span, single-column box-type frame structure, and the cut-and-cover area adopts a two-story, double-span, single-column box-type frame structure. Specifically, the two ends of the open-cut area are partially three-story, three-span, double-column box-type frame structures. The main station enclosure adopts a retaining structure of bored piles + internal bracing + shotcrete between piles, with the overall layout following the principle of "layered staggered layers and alternating zones."

[0094] Preferably, in step one, the construction of retaining piles, mixing piles, column-supported and tension-resistant piles, capping beams, and Larssen sheet piles should be started first in the direction of the secondary road, so that step two can be intervened earlier to mitigate the impact on the road surface as soon as possible.

[0095] Preferably, in step two, the secondary arterial road adjacent to the construction site needs to be moved 10m southward from its original location, and the original green belt and other structures need to be removed, leaving only a two-lane-in-two-lane-out design to provide sufficient space for subsequent traffic diversion.

[0096] Preferably, in step three, within the already limited excavation site, additional road space is created for the city roads by connecting external military temporary beams, thereby improving traffic flow speed. After being prefabricated in the factory, the military temporary beams only need to be placed in fixed positions after the road surface has been broken up. They then support the passage of non-motorized vehicles and pedestrians based on the height difference of the road surface and the supports between the columns. The installation of the military temporary beams can be carried out simultaneously with the traffic diversion in step two, provided that time and space permit, without requiring a specific order.

[0097] Preferably, in step eight, the final traffic diversion is also the second diversion, upgrading from the initial two-lane dual carriageway to a three-lane dual carriageway, while retaining the original landscaping and other greenery. The symmetrical area of ​​the secondary arterial road can be upgraded to the same scale before step eight, or it can begin after step eight, but not simultaneously with step eight, to avoid increasing traffic pressure on the road surface. The aim is to upgrade the secondary arterial road from a two-in, two-out lane to a three-in, three-out lane, creating a dual-main-line intersection and increasing traffic radiation in the city's secondary intersection center area.

[0098] Preferably, the first layer of support mentioned in steps four, six, nine, and eleven above uses concrete supports (800×1000mm) with a spacing of 7m to 9m. The second, third, and fourth layers of support use steel supports (Φ609, t=16mm) with a spacing of 2.3m to 3.5m, and the steel walers use double-jointed 45b steel. In each excavation step, care should be taken to ensure that the over-excavation depth when erecting each layer of support does not exceed 0.5 meters.

[0099] This method divides the subway station foundation pit into open-cut and cut-and-cover areas. The open-cut pit in the open-cut area is located near the main road, while the cut-and-cover pit in the cut-and-cover area is located near the secondary road. The open-cut and cut-and-cover areas are connected to form an L-shaped foundation pit based on the site topography. The overall construction considers the relocation and upgrading of the secondary road, prioritizing the excavation of the cut-and-cover area. Then, the three-layer open-cut area of ​​the main road and the two-layer cut-and-cover area of ​​the secondary road are constructed in a staggered manner. The road traffic diversion scheme involves deploying temporary road beams as auxiliary road frames for non-motorized vehicle lanes in step three, combined with the central and outer columns of the cut-and-cover area. This ensures that road traffic is not affected while meeting construction space requirements, and also reduces the number of underground pipeline relocations. Compared to traditional cut-and-cover or open-cut methods, this construction method is applicable to all intersection terrains, and can further upgrade urban hubs while completing the subway station construction. It offers a better construction environment, faster progress, and improved land utilization.

[0100] This embodiment provides an L-shaped semi-cut-and-cover construction method suitable for subway stations at intersections. The key points are:

[0101] (1) Alternate construction of cut-and-cover and open-cut sections.

[0102] This embodiment focuses on how to closely integrate two construction methods. Regardless of the construction method, the construction process is limited by materials and requires waiting for the structure to reach a certain level of reliability before it can continue. Therefore, implementing the two construction methods close together not only makes the entire construction process smoother, but also solves the problem of soil removal in the cut-and-cover method and the traffic interference problem on the surface in the open-cut method. At the same time, combining them into an L-shaped foundation pit saves land area to a certain extent, which can directly save economic costs.

[0103] (2) Constructing column piles

[0104] The column piles, which also act as tension piles, are driven deep into the underground rock mass to provide stable and reliable support for the roof slab. Under the protection of the columns and the roof slab, excavation can proceed to the bottom elevation of the pit to construct the main structure, including the base slab, side walls, and middle slab. This is a prerequisite for implementing the cut-and-cover semi-reverse construction method. Simultaneously, this will directly impact traffic diversion plans, as the secondary stabilization provided by the column piles will reliably ensure the safety of the temporary widened lanes. Special attention must be paid to positioning during column pile construction to prevent pile foundation eccentricity, and differential settlement between piles will also require close control.

[0105] In summary, this invention provides an L-shaped semi-cut-and-cover construction method suitable for subway stations at intersections, which has the following advantages compared to existing construction methods:

[0106] 1. Compared to traditional cut-and-cover and open-cut methods, the semi-cut-and-cover method in this construction approach cleverly combines the main advantages of cut-and-cover (reducing ground impact) and open-cut (facilitating construction), facilitating the access of underground excavated soil and related equipment, and significantly improving the efficiency of foundation pit construction, thereby effectively reducing related construction costs. Furthermore, compared to the ordinary semi-cut-and-cover method, the L-shaped semi-cut-and-cover method can effectively integrate with the city's sub-center intersection, simultaneously upgrading traffic at the intersection while completing the overall foundation pit construction, and reducing the need for underground pipeline relocation by half. This approach has extremely high economic, scientific, and replicable guiding significance.

[0107] 2. Traditional large-span subway stations occupy too large an area and are subject to great terrain restrictions. The ingenious design of the L-shaped foundation pit ensures that the area occupied is not too large, which would require the acquisition of a large amount of open land. At the same time, the shape of the foundation pit is attached to the intersection, and the functional zoning is based on the existing line, which allows for relatively flexible adjustment of the ground distribution.

[0108] 3. This construction method divides the project into open-cut and cut-and-cover zones, with alternating construction between the two areas, allowing for a continuous and uninterrupted workflow. Furthermore, if a sufficient number of personnel are available, the process can be highly streamlined, maintaining the sequential order of steps in both zones. This ensures efficient continuous construction, facilitates the movement of personnel and equipment between the cut-and-cover zones, and saves necessary waiting time, such as the time required for material strength assessment.

[0109] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A method for constructing an L-shaped semi-cut-and-cover subway station at an intersection, characterized in that, include: Excavation and demolition processes; The excavation process includes: The open-cut area (1) is constructed using the cut-and-cover method on the side of the subway station near the main road of the intersection, and the cut-and-cover area (2) is constructed using the cut-and-cover method on the side of the subway station near the secondary road of the intersection. The open-cut area (1) and the cut-and-cover area (2) are excavated in a multi-layer structure, and the open-cut area (1) is excavated layer by layer in the order of the cut-and-cover area (2) first and then the cut-and-cover area (2) and the support construction is carried out simultaneously until the bottom slab of the open-cut area (1) is completed. The demolition process includes: When the open-cut area (1) and the cut-and-cover area (2) reach the preset demolition conditions, the supports are removed layer by layer in the order of first the cut-and-cover area (2) and then the open-cut area (1) until the top slab of the open-cut area (1) is backfilled with soil; finally, the open-cut area (1) and the cut-and-cover area (2) form an L-shaped foundation pit.

2. The L-shaped semi-cut-and-cover construction method for subway stations at intersections according to claim 1, characterized in that, It also includes the construction preparation process carried out before the excavation construction process, and the specific steps are as follows: Construction barriers were erected in the area to be constructed; traffic diversion at the intersection was completed by moving the secondary road in the opposite direction of the foundation pit.

3. The L-shaped semi-cut-and-cover construction method for subway stations at intersections according to claim 2, characterized in that, The steps for setting up construction barriers in the area to be constructed include: The green space and part of the road surface were demolished, and retaining piles, mixing piles, column piles, capping beams and Larssen steel sheet piles were constructed.

4. The L-shaped semi-cut-and-cover construction method for subway stations at intersections according to claim 2, characterized in that, First, set up construction barriers along the secondary roads, then set up construction barriers along the main roads.

5. A method for constructing an L-shaped semi-cut-and-cover subway station at an intersection, as described in claim 2, is characterized in that... While traffic diversion is being carried out at the intersection, a temporary military bridge (3-1) is set up on one side of the secondary road at the intersection to temporarily expand the secondary road into a lane for non-motorized vehicles and emergency use.

6. A method for constructing an L-shaped semi-cut-and-cover subway station at an intersection, as described in claim 5, is characterized in that... Erect piles (3-4) at the bottom of the military bridge (3-1) and insert them into the underground rock mass.

7. The L-shaped semi-cut-and-cover construction method for subway stations at intersections according to claim 1, characterized in that, The specific steps of the excavation process are as follows: Step 1: Excavate the open-cut section to the first basement level (1-1), erect the first support for the open-cut section, and apply wire mesh and spray concrete between the columns; Step 2: Excavate the cut-and-cover area to the design elevation of the cut-and-cover roof slab and simultaneously erect the first support for the underground excavation area; Step 3: Continue open excavation of the first basement level (1-1), erect the second support in the open excavation area, and apply wire mesh and spray concrete between the columns; Step 4: Construct the capping beam under the top slab of the cut-and-cover area; Step 5: Excavate the cut-and-cover area to level 1 (2-1) and erect the second support for the cut-and-cover area; Step Six: Continue excavating the open-cut area to the second basement level (1-2) and erect the third support for the open-cut area; Step 7: Excavate the cut-and-cover area to the design elevation of the bottom of the pit (2-2) and erect the third support for the cut-and-cover area; Step 8: Excavate the open-cut area to the design elevation of the pit bottom 3 layers (1-3) and erect the fourth support for the open-cut area.

8. A method for constructing an L-shaped semi-cut-and-cover subway station at an intersection, as described in claim 7, is characterized in that... In step five, before excavating and covering the first basement level (2-1), once the concrete strength of the top slab reaches the design strength, the secondary road that was moved during the construction preparation process will be restored to its original state, and the secondary road will be upgraded from two entrances and two exits to three entrances and three exits.

9. A method for constructing an L-shaped semi-cut-and-cover subway station at an intersection, as described in claim 7, is characterized in that... After the open-cut and cut-and-cover areas are excavated to the design elevation of the pit bottom, grounding grids, bottom slab cushion layers, waterproof layers, bottom slabs, bottom longitudinal beams, and side wall structures are constructed for the open-cut and cut-and-cover areas respectively.

10. A method for constructing an L-shaped semi-cut-and-cover subway station at an intersection, as described in claim 7, is characterized in that... The specific steps of the demolition process are as follows: Step 1: After the bottom slab of the cut-and-cover 2nd basement level (2-2) reaches the design strength, remove the third support in the cut-and-cover area; Step 2: After the bottom slab of the third basement level (1-3) of the open excavation reaches the design strength, remove the fourth support in the open excavation area; Step 3: After the bottom slab of the cut-and-cover level 1 (2-1) reaches the design strength, remove the second support in the cut-and-cover area; Step 4: After the bottom slab of the second basement level (1-2) of the open excavation reaches the design strength, remove the third support in the open excavation area; Step 5: Continue construction upwards and dismantle the remaining support structure in the cut-and-cover area; Step 6: After the bottom slab of the open-cut basement (1-1) reaches the design strength, remove the second support in the open-cut area and at the same time construct the top slab structure of the open-cut basement (1-1). Step 7: After the top slab structure of the open-cut basement level (1-1) reaches the design strength, remove the first support, apply the waterproof layer and concrete protective layer, and backfill the top slab of the open-cut area with soil.

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