Method for excavating foundation pit adjacent to subway

Abstract

The invention provides a method for excavating a foundation pit adjacent to a subway, which comprises the following steps: S1, the foundation pit is divided into a zone I, a zone II and a zone III in sequence from far to near, the zone I is divided into a zone I-1, a zone I-2 and a zone I-3, and the zone II is divided into a zone II-1, a zone II-2 and a zone II-3; s2, construction is conducted from far to near, earth excavation is conducted on the I-2 area of the I area, and then earth excavation is conducted on the I-1 area and the I-3 area of the I area at the same time; s3, after the bottom of the area I is built, dismantling construction of a basement structure and a support is conducted; s4, after the I area supports are formed, the first support of the II-2 area of the II area is firstly constructed, and then the first supports of the II-1 area and the II-3 area are synchronously constructed; s5, earth excavation is conducted on the II-2 area of the II area, and then earth excavation is conducted on the II-1 area and the II-3 area at the same time; s6, a first support is constructed for the area III, and earth excavation is conducted on the area III; and S7, basement structure construction and support dismantling construction are conducted. The method not only effectively controls the deformation of the foundation pit, but also improves the construction speed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of earthwork excavation in building construction, and particularly relates to a foundation pit excavation method close to a subway. BACKGROUND

[0002] In some large projects close to a subway, due to the large area of the foundation pit, the complex surrounding environment, the high subway protection requirements and other factors, the foundation pit support design usually adopts a split pit method, and the split pits are separated by cast-in-place piles. The construction process of such projects is usually to first carry out earthwork excavation and support construction in a single pit, and then carry out excavation construction in the adjacent foundation pit after the basement structure of the single pit is completed and the positive and negative zero values are obtained. This construction mode not only leads to a long construction period of the entire foundation pit, but also causes long-term disturbance to the surrounding environment, especially for projects with fast development rhythm, close to the subway, important buildings or important pipelines, which has great limitations.

[0003] If the split pit simultaneous construction method is adopted, due to unreasonable partition of the two side foundation pits, uncoordinated excavation, uncoordinated construction sequence, unsynchronized support system and structure construction and other problems, the foundation pit support structure and the partition pile are unevenly stressed, which causes excessive deformation of the support structure, thereby affecting the surrounding environment. SUMMARY

[0004] The present application provides a foundation pit excavation method close to a subway, which not only effectively controls the deformation of the foundation pit, but also improves the construction speed.

[0005] The technical scheme of the present application is as follows:

[0006] A foundation pit excavation method close to a subway, the foundation pit has a longitudinal direction parallel to the extension direction of a subway interval tunnel and a transverse direction perpendicular to the extension direction of the subway interval tunnel, and a support is arranged around the foundation pit. The excavation method comprises the following steps: S1-S7.

[0007] S1: Partitioning the foundation pit, the foundation pit is partitioned into a zone I, a zone II and a zone III along the longitudinal direction and from far to near the subway interval tunnel, partition piles are arranged between the adjacent two zones of the zone I, the zone II and the zone III, the zone I is partitioned into a zone I-1, a zone I-2 and a zone I-3 along the transverse direction and from one longitudinal side of the foundation pit to the other longitudinal side, partition piles are arranged between the adjacent two zones of the zone I-1, the zone I-2 and the zone I-3, the zone II is partitioned into a zone II-1, a zone II-2 and a zone II-3 along the transverse direction and from one longitudinal side of the foundation pit to the other longitudinal side, and partition piles are arranged between the adjacent two zones of the zone II-1, the zone II-2 and the zone II-3.

[0008] S2: From far to near, the zone I-2 of the zone I is first subjected to earthwork excavation, then the zone I-1 and the zone I-3 of the zone I are simultaneously subjected to earthwork excavation after transverse bracing.

[0009] S3: After the I-1 region, the I-2 region and the I-3 region of the I region are simultaneously bottomed, basement structure construction and support removal construction are performed.

[0010] S4: After the support of the I region is formed, the first support in the transverse direction of the II-2 region of the II region is first constructed, and the first support in the transverse direction of the II-1 region and the II-3 region is simultaneously constructed.

[0011] S5: When the I region is zeroed, the II-2 region of the II region is first excavated, after the II-2 region is bottomed, basement structure construction and support removal construction are performed, and the II-1 region and the II-3 region are simultaneously excavated, after the II-1 region and the II-3 region are bottomed, basement structure construction and support removal construction are performed.

[0012] S6: When the II region is zeroed, the first support of the III region is constructed, and the III region is excavated, when the excavation reaches the first support below the III region, a hydraulic servo steel support system is used to excavate and install simultaneously.

[0013] S7: After the III region is bottomed, basement structure construction and support removal construction are performed.

[0014] Further, the foundation pit excavation method close to the subway comprises the following steps: S2-S3.

[0015] S21: The I-2 region is divided into an I-2-1 region, an I-2-2 region and an I-2-3 region from one side to the other side in the longitudinal direction of the foundation pit, a partition pile is arranged between two adjacent regions of the I-2-1 region, the I-2-2 region and the I-2-3 region, the I-2-2 region is excavated from the two sides to the middle, the I-2-1 region and the I-2-3 region are excavated from one side close to the I-2-2 region to the other side in the longitudinal direction, and the support formation sequence is the same as the soil excavation sequence.

[0016] S22: The I-1 region is divided into an I-1-1 region, an I-1-2 region and an I-1-3 region from one side to the other side in the longitudinal direction of the foundation pit, a partition pile is arranged between two adjacent regions of the I-1-1 region, the I-1-2 region and the I-1-3 region, the I-3 region is divided into an I-3-1 region, an I-3-2 region and an I-3-3 region from one side to the other side in the longitudinal direction of the foundation pit, a partition pile is arranged between two adjacent regions of the I-3-1 region, the I-3-2 region and the I-3-3 region, and the excavation direction and the support formation sequence of the I-1 region and the I-3 region are the same as the excavation direction and the support formation sequence of the I-2 region in step S21.

[0017] Further, in the foundation pit excavation method close to the subway, after the I-1 region, the I-2 region and the I-3 region of the I region are simultaneously bottomed in the step S3, the basement structure construction and the support removal construction are simultaneously performed and the construction sequence is simultaneously the step S21; and at the position close to the partition pile and the foundation pit enclosure, the support is removed by using the artificial concrete stripping method and the partition pile synchronous cutting and synchronous force unloading method from the longitudinal two sides.

[0018] Further, in the foundation pit excavation method close to the subway, after the I-1 region, the I-2 region and the I-3 region of the I region are simultaneously bottomed in the step S3, the basement structure construction and the support removal construction are simultaneously performed and the construction sequence is simultaneously the step S21; and at the position close to the partition pile and the foundation pit enclosure, the support is removed by using the artificial concrete stripping method and the partition pile synchronous cutting and synchronous force unloading method from the longitudinal two sides.

[0019] Further, in the foundation pit excavation method close to the subway, the step S5 comprises S51-S52.

[0020] S51: the II-2 region is divided into II-2-1 region, II-2-2 region and II-2-3 region from one longitudinal side of the foundation pit to the other side, the II-2-2 region is excavated from the longitudinal two sides to the middle, and the II-2-1 region and the II-2-3 region are excavated from one side close to the II-2-2 region to the other side along the longitudinal direction, and the support formation sequence is the same as the earthwork excavation sequence.

[0021] S52: the II-1 region is divided into II-1-1 region, II-1-2 region and II-1-3 region from one longitudinal side of the foundation pit to the other side, the II-3 region is divided into II-3-1 region, II-3-2 region and II-3-3 region from one longitudinal side of the foundation pit to the other side, and the excavation direction and the support formation sequence of the II-1 region and the II-3 region are the same as the excavation direction and the support formation sequence of the II-2 region in the step S61.

[0022] Further, in the foundation pit excavation method close to the subway, the step S5 comprises S51-S52.

[0023] Further, in the foundation pit excavation method close to the subway, the step S6 comprises S61: the III region is divided into III-1 region, III-2 region and III-3 region from one longitudinal side of the foundation pit to the other side, the III-2 region is excavated from the longitudinal two sides to the middle, and the III-1 region and the III-3 region are excavated from one side close to the III-2 region to the other side along the longitudinal direction.

[0024] Further, in the foundation pit excavation method close to the subway, after the III region is bottomed in the step S7, the basement structure construction and the support removal construction are simultaneously performed and the construction sequence is simultaneously the step S61.

[0025] Further, in the foundation pit excavation method close to the subway, the I area and the II area in the step S1 are divided into three layers from top to bottom along the gravity direction, and the three layers of the I area and the II area are excavated after supporting.

[0026] Further, in the foundation pit excavation method close to the subway, the III area in the step S1 is divided into four layers from top to bottom along the gravity direction, and the first support is set first and then excavated, and the second to fourth supports are installed while excavating; and / or the transverse width of the I area and the II area is greater than the transverse width of the III area.

[0027] The beneficial effects of the present application are as follows:

[0028] The foundation pit excavation method close to the subway provided by the present application has the advantages that: through the overall excavation process of "compared to the subway, construction from far to near, parallel direction multiple pits synchronous excavation, vertical direction separate pit interval operation", and the partition and flow direction during synchronous excavation are refined, the support construction sequence and direction are optimized, so as to effectively control the deformation of the foundation pit, reduce the influence on the surrounding environment, and improve the construction speed of the foundation pit. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a flow chart of the foundation pit excavation method close to the subway of the present application;

[0030] Figure 2 is a schematic diagram of foundation pit partition of the foundation pit excavation method close to the subway of the present application;

[0031] Figure 3 is a schematic diagram of small partition and excavation direction of the foundation pit excavation method close to the subway of the present application. DETAILED DESCRIPTION

[0032] The present application will be further described in detail below in combination with the drawings and specific embodiments. The advantages and features of the present application will be more apparent according to the following description and claims. It should be noted that the drawings are very simplified and all use non-precise proportions, only to facilitate and clearly assist the purpose of explaining the embodiments of the present application.

[0033] As shown in Figure 1 and Figure 3 , the present embodiment provides a foundation pit excavation method close to the subway, the foundation pit has a longitudinal direction parallel to the extension direction of the subway section tunnel and a transverse direction perpendicular to the extension direction of the subway section tunnel, and a surrounding structure is arranged around the foundation pit, the excavation method comprises the following steps: S1-S7.

[0034] S1: The foundation pit is divided into zones, and the foundation pit is divided into Zone I, Zone II and Zone III in sequence from far to near along the longitudinal direction and away from the subway interval tunnel. Adjacent two zones of Zone I, Zone II and Zone III are provided with a partition pile. Zone I is divided into Zone I-1, Zone I-2 and Zone I-3 in sequence from one longitudinal side of the foundation pit to the other side along the transverse direction, and adjacent two zones of Zone I-1, Zone I-2 and Zone I-3 are provided with a partition pile. Zone II is divided into Zone II-1, Zone II-2 and Zone II-3 in sequence from one longitudinal side of the foundation pit to the other side along the transverse direction, and adjacent two zones of Zone II-1, Zone II-2 and Zone II-3 are provided with a partition pile.

[0035] The excavation steps of Zone I are as follows: S2-S3.

[0036] S2: Construction is performed from far to near, and first, Zone I-2 of Zone I is excavated for earthwork, and then Zone I-1 and Zone I-3 of Zone I are simultaneously excavated for earthwork after lateral bracing.

[0037] Step S2 can specifically include steps S21 and S22.

[0038] S21: Zone I-2 is divided into Zone I-2-1, Zone I-2-2 and Zone I-2-3 from one longitudinal side of the foundation pit to the other side, and adjacent two zones of Zone I-2-1, Zone I-2-2 and Zone I-2-3 are provided with a partition pile. Zone I-2-2 is excavated from the two longitudinal sides to the middle. Zone I-2-1 and Zone I-2-3 are subdivided into three regions of a region, a b region and a c region in sequence from the side close to Zone I-2-2 to the side away from Zone I-2-2 along the longitudinal direction, and excavation is performed in sequence along the a region-c region. Zone I-2-1 and Zone I-2-3 are respectively constructed to the two sides along the longitudinal direction with the two partition piles as the initial excavation positions. The formation sequence of the support and the bottom plate before excavation is the same as the earthwork excavation sequence. Three layers of earthwork excavation work of Zone I-2 is completed in sequence from top to bottom along the gravity direction.

[0039] S22: The excavation direction and support formation sequence of the I-1 region and the I-3 region are the same as the excavation direction and support formation sequence of the I-2 region in step S21. Specifically, the I-1 region is divided into I-1-1 region, I-1-2 region and I-1-3 region from one longitudinal side of the foundation pit to the other side, and a partition pile is arranged between the adjacent two regions of the I-1-1 region, the I-1-2 region and the I-1-3 region. The I-3 region is divided into I-3-1 region, I-3-2 region and I-3-3 region from one longitudinal side of the foundation pit to the other side, and a partition pile is arranged between the adjacent two regions of the I-3-1 region, the I-3-2 region and the I-3-3 region. The I-1-1 region and the I-1-3 region are sequentially subdivided into d region, e region and f region along the longitudinal direction from the side close to the I-1-2 region to the side away from the I-1-2 region, and excavation is sequentially performed along the d region-f region. The I-3-1 region and the I-3-3 region are sequentially subdivided into d region, e region and f region along the longitudinal direction from the side close to the I-3-2 region to the side away from the I-3-2 region, and excavation is sequentially performed along the d region-f region. The I-1-2 region and the I-3-2 region are excavated from the two longitudinal sides to the middle. Since the I-1-2 region is located at the edge of the foundation pit, the I-1-2 region is subdivided into A region, B region and A region along the longitudinal direction, the B region is located between the two A regions, and excavation is performed from the two sides to the B region along the A region, thereby further improving the deformation resistance of the foundation pit. The three-layer soil excavation work of the I-1 region and the I-3 region is sequentially completed from top to bottom along the gravity direction.

[0040] The above excavation sequence can reduce the adverse effects of synchronous excavation of the three pits (for example, the I-2-1 region, the I-2-2 region and the I-2-3 region) on the deformation of the partition pile.

[0041] S3: After the I-1 region, the I-2 region and the I-3 region of the I region are simultaneously bottomed, the basement structure construction and the support removal construction are simultaneously performed and the construction sequence is step S21, and at the position close to the partition pile and the foundation pit enclosure, the support is removed by using the artificial stripping concrete method and the partition pile is simultaneously cut and removed from the two longitudinal sides to simultaneously unload the force, thereby further reducing the disturbance influence of the support removal on the partition pile and the foundation pit enclosure.

[0042] In the process of synchronous excavation of soil or construction of basement structure in each three small regions (for example, the I-2-1 region, the I-2-2 region and the I-2-3 region), the workloads of the small regions are ensured to be similar by reasonably allocating and configuring the number of workers and machines as needed, and dynamic management is realized by daily progress monitoring. In particular, when the soil is excavated on both sides of the partition pile, the two sides are excavated in balance and cooperation, and real-time regulation and control are performed in combination with the monitoring data.

[0043] The excavation steps of the II region are as follows: S4-S5.

[0044] S4: After the support of the I area is formed, under the premise that the force of the retaining arm of the foundation pit is controllable, the first support of the transverse of the II-2 area of the II area is constructed first, and the first support of the transverse of the II-1 area and the II-3 area is constructed synchronously, and the construction sequence of the first support of the II-1 area, the II-2 area and the II-3 area is step S21, which can improve the overall foundation pit construction speed.

[0045] S5: When the I area is zero, the II-2 area of the II area is excavated first, and after the II-2 area is built, the basement structure construction and support removal construction are performed, and the II-1 area and the II-3 area are excavated simultaneously, and after the II-1 area and the II-3 area are built, the basement structure construction and support removal construction are performed. Wherein, the zero (±0.000 or ±000) is the reference elevation control point of the building.

[0046] Step S5 can specifically include steps S51 and S52.

[0047] S51: The II-2 area is divided into II-2-1 area, II-2-2 area and II-2-3 area from one side to the other side of the longitudinal direction of the foundation pit, the II-2-2 area is excavated from the two sides to the middle, and the II-2-1 area and the II-2-3 area are sequentially subdivided into g area and h area from the side close to the II-2-2 area to the side away from the II-2-2 area along the longitudinal direction, and the excavation is performed along the g area-h area. The formation sequence of the support and the bottom plate before excavation is the same as the excavation sequence. The three-layer soil excavation work of the II-2 area is completed from top to bottom along the gravity direction.

[0048] S52: The II-1 area is divided into II-1-1 area, II-1-2 area and II-1-3 area from one side to the other side of the longitudinal direction of the foundation pit, and the II-3 area is divided into II-3-1 area, II-3-2 area and II-3-3 area from one side to the other side of the longitudinal direction of the foundation pit, the II-1-1 area and the II-1-3 area are sequentially subdivided into i area and j area from the side close to the II-1-2 area to the side away from the II-1-2 area along the longitudinal direction, and the excavation is performed along the i area-j area. The II-3-1 area and the II-3-3 area are sequentially subdivided into i area and j area from the side close to the II-3-2 area to the side away from the II-3-2 area along the longitudinal direction, and the excavation is performed along the i area-j area. The formation sequence of the support and the bottom plate before excavation is the same as the excavation sequence. The three-layer soil excavation work of the II-1 area and the II-3 area is completed from top to bottom along the gravity direction.

[0049] When the II-1 area, the II-2 area or the II-3 area is built, the basement structure construction and the support removal construction are performed synchronously and the construction sequence is from the soil excavation sequence, at the position close to the partition pile and the foundation pit retaining, the support is removed by using the artificial stripping concrete method and the partition pile is synchronously cut off from the two sides of the longitudinal direction and the force is synchronously unloaded.

[0050] The excavation steps of the III area are as follows: S6-S7.

[0051] S6: When the positive and negative zero of the II area is out, the first support of the III area is constructed, and the earthwork excavation of the III area is carried out. When the excavation reaches the first support below the III area, a hydraulic servo steel support system is used for excavation and installation.

[0052] The step S6 can specifically include a step S61.

[0053] S61: The III area is divided into III-1 area, III-2 area and III-3 area from one longitudinal side of the foundation pit to the other side. The III-2 area is excavated from the two longitudinal sides to the middle. The III-1 area and the III-3 area are divided into k areas and m areas along the longitudinal direction from the side close to the III-2 area to the side away from the III-2 area, and are excavated from the k area to the m area. Four layers of excavation work are carried out from top to bottom along the gravity direction. The hydraulic servo steel support system is used during the second to fourth excavation to realize the excavation and installation simultaneously. Since the III area is a narrow and long buffer foundation pit on the side of the subway, the hydraulic servo steel support system can dynamically adjust the support axial force, further reducing the influence of the foundation pit construction on the subway and the surrounding environment.

[0054] S7: After the III area is built, the basement structure construction and the support removal construction are carried out synchronously and the construction sequence is synchronous with the step S61.

[0055] The above foundation pit excavation method, through the overall process of "compared to the subway, construction from far to near, parallel direction multiple pit synchronous excavation, vertical direction sub-pit interval operation", the partition and flow direction during synchronous excavation are refined, the support construction sequence and direction are optimized, under the condition that the cantilever force of the enclosure meets the requirements, the first support is constructed, the narrow and long sub-pit on the side of the subway is constructed, and the hydraulic servo steel support system is used, thereby effectively controlling the deformation of the foundation pit, reducing the influence on the surrounding environment, and greatly speeding up the construction speed of the foundation pit.

[0056] As a preferred embodiment, in the foundation pit excavation method close to the subway, the III area in the step S1 is divided into four layers from top to bottom along the gravity direction, the first support is set first and then excavated, the second to fourth supports are excavated and installed simultaneously, and / or the transverse width of the I area and the II area is greater than the transverse width of the III area. Since the III area is a narrow and long buffer foundation pit on the side of the subway, the hydraulic servo steel support system can dynamically adjust the support axial force, further reducing the influence of the foundation pit construction on the subway and the surrounding environment.

[0057] As a preferred embodiment, in the foundation pit excavation method close to the subway, the III area in the step S1 is divided into four layers from top to bottom along the gravity direction, the first support is set first and then excavated, the second to fourth supports are excavated and installed simultaneously, and / or the transverse width of the I area and the II area is greater than the transverse width of the III area. Since the III area is a narrow and long buffer foundation pit on the side of the subway, the hydraulic servo steel support system can dynamically adjust the support axial force, further reducing the influence of the foundation pit construction on the subway and the surrounding environment.

[0058] The above description is only the description of the preferred embodiments of the present application, and is not any limitation on the scope of the present application. Any change and modification made by the person skilled in the art according to the above disclosure is within the protection scope of the claims.

Claims

1. A method for excavating a foundation pit adjacent to a subway, characterized in that: The foundation pit has a longitudinal direction parallel to the extension direction of the subway section tunnel and a transverse direction perpendicular to the extension direction of the subway section tunnel. The foundation pit is surrounded by enclosures. The excavation method includes the following steps: S1: Excavation zoning: The excavation is divided into Zone I, Zone II, and Zone III along a line parallel to the longitudinal direction and from the farthest to the nearest subway tunnel. Separation piles are installed between adjacent zones I, II, and III. Zone I is divided into Zone I-1, Zone I-2, and Zone I-3 along a line parallel to the transverse direction and from one side of the excavation longitudinal direction to the other. Separation piles are installed between adjacent zones I-1, I-2, and I-3. Zone II is divided into Zone II-1, Zone II-2, and Zone II-3 along a line parallel to the transverse direction and from one side of the excavation longitudinal direction to the other. Separation piles are installed between adjacent zones II-1, II-2, and II-3. S2: Construction is carried out from far to near. First, excavate the Ⅰ-2 area of ​​zone Ⅰ to form a horizontal support. Then, excavate the Ⅰ-1 and Ⅰ-3 areas of zone Ⅰ at the same time. S3: After the simultaneous construction of the basement in Zones I-1, I-2, and I-3 of Zone I, the basement structure construction and support removal construction will be carried out; S4: After the support of Zone I is formed, first construct the first horizontal support of Zone II-2 of Zone II, and then simultaneously construct the first horizontal support of Zone II-1 and Zone II-3; S5: When the positive and negative zero is reached in Zone I, excavation is first carried out in Zone II-2 of Zone II. After the bottom of Zone II-2 is built, the basement structure construction and support removal construction are carried out. Then, excavation is carried out in Zone II-1 and Zone II-3 simultaneously. After the bottom of Zone II-1 and Zone II-3 is built, the basement structure construction and support removal construction are carried out. S6: After the positive and negative zero is reached in Zone II, the first support of Zone III is constructed and earthwork is excavated in Zone III. When the excavation reaches the support below the first support of Zone III, a hydraulic servo steel support system is used to install the support while digging; S7: After the bottom of Zone III is built, the basement structure construction and support removal construction will be carried out.

2. The method for excavating a foundation pit adjacent to a subway according to claim 1, wherein: The step S2 comprises: S21: Zone I-2 is divided longitudinally from one side of the foundation pit to the other into Zone I-2-1, Zone I-2-2, and Zone I-2-3. Separation piles are installed between adjacent zones I-2-1, I-2-2, and I-2-3. Zone I-2-2 is excavated longitudinally from both sides toward the center. Zones I-2-1 and I-2-3 are excavated longitudinally from the side closest to Zone I-2-2 toward the other side. The support formation sequence is the same as the earthwork excavation sequence. S22: Zone I-1 is divided into Zone I-1-1, Zone I-1-2 and Zone I-1-3 from one longitudinal side of the foundation pit, and separation piles are set between adjacent zones of Zone I-1-1, Zone I-1-2 and Zone I-1-3. Zone I-3 is divided into Zone I-3-1, Zone I-3-2 and Zone I-3-3 from one longitudinal side of the foundation pit, and separation piles are set between adjacent zones of Zone I-3-1, Zone I-3-2 and Zone I-3-3. The excavation direction and support formation order of Zone I-1 and Zone I-3 are the same as the excavation direction and support formation order of Zone I-2 in step S21.

3. The method for excavating a foundation pit adjacent to a subway according to claim 2, wherein: After the simultaneous construction of the bottoms of Areas I-1, I-2 and I-3 of Area I in Step S3, the basement structure construction and support removal construction are carried out simultaneously and the construction sequence is the same as that of Step S21. In addition, at locations close to the separation piles and foundation pit enclosures, the supports are removed by manually stripping the concrete and by simultaneously cutting off the separation piles from both longitudinal sides and by the simultaneous unloading method.

4. The method for excavating a foundation pit adjacent to a subway as claimed in claim 2, wherein: In the step S4, after the support of zone I is formed, under the premise that the force of the foundation pit retaining cantilever is controllable, the first horizontal support of zone II-2 of zone II is constructed first, and then the first horizontal supports of zones II-1 and II-3 are constructed simultaneously. The construction order of the first supports of zones II-1, II-2 and II-3 is the same as that of step S21.

5. The method for excavating a foundation pit adjacent to a subway according to claim 1, wherein: The step S5 comprises: S51: Zone II-2 is divided into Zone II-2-1, Zone II-2-2, and Zone II-2-3 from one side of the foundation pit to the other. Zone II-2-2 is excavated from both sides toward the center, and Zone II-2-1 and Zone II-2-3 are excavated from the side closest to Zone II-2-2 toward the other side. The support formation sequence is the same as the earthwork excavation sequence. S52: Zone II-1 is divided into Zone II-1-1, Zone II-1-2 and Zone II-1-3 from one longitudinal side of the foundation pit to the other. Zone II-3 is divided into Zone II-3-1, Zone II-3-2 and Zone II-3-3 from one longitudinal side of the foundation pit to the other. The excavation direction and support formation sequence of Zone II-1 and Zone II-3 are the same as the excavation direction and support formation sequence of Zone II-2 in step S61.

6. The method for excavating a foundation pit adjacent to a subway according to claim 5, wherein: The construction sequence of the basement structure and support removal in step S6 is the same as that in step S51. At the position close to the separation piles and the foundation pit enclosure, the support is removed by manually stripping the concrete and simultaneously cutting and unloading the separation piles from both longitudinal sides.

7. The method for excavating a foundation pit adjacent to a subway according to claim 1, wherein: The step S6 comprises: S61: Zone III is divided into Zone III-1, Zone III-2 and Zone III-3 from one side of the foundation pit to the other. Zone III-2 is excavated from both sides of the longitudinal direction to the middle, and Zone III-1 and Zone III-3 are excavated from the side close to Zone III-2 along the longitudinal direction to the other side.

8. The method for excavating a foundation pit adjacent to a subway according to claim 7, wherein: In step S7, after the bottom of zone III is built, the order of basement structure construction and support removal is the same as step S61.

9. The method for excavating a foundation pit adjacent to a subway as claimed in claim 1, wherein: In step S1, area I and area II are divided into three layers from top to bottom along the gravity direction, and the three layers of area I and area II are all excavated in a manner of first supporting and then excavating.

10. The method for excavating a foundation pit adjacent to a subway according to claim 1, wherein: In step S1, zone III is divided into four layers from top to bottom along the gravity direction, and the first support is set before excavation, and the second to fourth layers are installed with support during excavation; and / or, The lateral widths of regions I and II are greater than the lateral width of region III.

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