Foundation pit bracing replacement construction method and underground tunnel

Abstract

The application relates to the technical field of underground building construction, and discloses a foundation pit support replacement construction method and an underground tunnel. The foundation pit support replacement construction method comprises the following steps: pouring a bottom plate on the bottom wall of a foundation pit, then pouring at least two side walls on the bottom plate, wherein the two side walls are oppositely arranged with the support structure corresponding to one side of the foundation pit and are spaced apart, and the plurality of side walls are sequentially and spaced apart; mounting a connecting piece on the support structure and pouring a replacement support column between the side wall and the support structure; connecting a second support beam between any two opposite side walls; removing the first support beam, and then constructing a top plate on the side wall. When the support structure is extruded towards the inside of the foundation pit after the first support beam is removed, the replacement support column can conduct the extrusion force to the side wall, and the extrusion force is conducted to the second support beam through the side wall, the second support beam can form a support between the two opposite inner side walls of the foundation pit, and thus the stress of each side wall can be uniform.

Description

Technical Field

[0001] This application relates to the field of underground construction technology, and in particular to a method for foundation pit replacement construction and an underground tunnel applicable to the method for foundation pit replacement construction. Background Technology

[0002] In related technologies, underground structures such as basements and underground tunnels are all located below ground level. During construction, it is necessary to first excavate the soil to create a foundation pit. The inner walls of the foundation pit need to be supported by a support structure to prevent the soil on both sides of the foundation pit from collapsing into the pit. Then, construction workers construct the underground structure into the foundation pit. In order to prevent the support structure from deforming into the foundation pit under soil pressure as much as possible, a bracing beam is installed between the support structures on opposite sides of the foundation pit. When the underground structure needs to be covered with a roof slab, the bracing beam spans the inside of the foundation pit and interferes with the roof slab construction area, making it difficult to construct and shape the roof slab.

[0003] Chinese patent application CN219364635U discloses a combined support structure. This structure has diagonal braces between the bottom slab and side walls of an underground building. During the process of removing the supporting beams to construct the top slab, the compressive force of the support structure towards the pit is transmitted sequentially to the bottom of the pit through the side walls, diagonal braces, and bottom slab. Because the soil pressure on the support structure on different sides of the pit is different, the lateral compressive force generated by the support structure is different, resulting in different stress on different side walls. When the stress on the side wall is too large, the side wall is prone to local stress concentration, causing cracking or deformation of the side wall and structural damage, thus affecting the construction quality and safety. Summary of the Invention

[0004] The purpose of this application is to provide support for the retaining structure while ensuring the smooth construction and shaping of the top slab of the underground building, and to ensure that the stress on each side wall of the underground building is uniform, thereby avoiding local stress concentration on the side walls, which could lead to cracking and deformation, and thus improving construction quality and safety.

[0005] To achieve the above objectives, this application provides a method for constructing a foundation pit support replacement system.

[0006] This application further provides an underground tunnel.

[0007] According to the foundation pit replacement support construction method of this application, in a first direction perpendicular to the height direction of the foundation pit, two opposing inner sidewalls of the foundation pit are provided with support structures. The support structures extend along the height direction of the foundation pit and are inserted below the bottom wall of the foundation pit. A first pair of support beams connects the two opposing support structures. The foundation pit replacement support construction method includes the following steps: pouring a bottom slab on the bottom wall of the foundation pit, and then pouring at least two sidewalls upwards on the bottom slab. The top wall height of the poured sidewalls is not higher than the height of the first pair of support beams, wherein the two sidewalls are respectively connected to the corresponding side of the foundation pit. The support structure is arranged opposite to each other and spaced apart along the first direction, and a plurality of side walls are arranged sequentially and spaced apart along the first direction; connectors are installed on the support structure, and a replacement support column is cast between the side wall and the support structure so that the replacement support column is fixedly connected to the support structure through the connectors; a second pair of support beams is connected between any two opposite side walls, and a pre-support force along the axial direction of the second pair of support beams is applied between the two opposite side walls using the second pair of support beams, the second pair of support beams being located below the top wall of the side wall; the first pair of support beams is removed, and then a top slab is constructed on the side wall.

[0008] According to the foundation pit replacement support construction method of this application, when constructing an underground structure using this method, replacement support columns are poured between the side walls and the supporting structure, and a second pair of support beams are connected between two opposing side walls. When the first pair of support beams is removed, and the supporting structure is squeezed into the foundation pit by soil pressure, the supporting structure can transmit the compressive force to the side walls of the structure through the replacement support columns, and further transmit it to the second pair of support beams through the side walls. The second pair of support beams can provide support for the two opposing side walls and form a force transmission path between the two opposing inner side walls of the foundation pit. This makes the compressive force on the side walls more uniform, avoids local stress concentration in the side walls, prevents cracking and deformation of the side walls, and thus improves construction quality and safety. Furthermore, the second pair of support beams is located below the top wall of the side walls, that is, the second pair of support beams does not pass through the construction area of ​​the top slab. While indirectly supporting the supporting structure, the second pair of support beams can ensure the smooth construction and shaping of the top slab.

[0009] In some examples of this application, after pouring the base slab and at least two side walls in the foundation pit and before installing the connectors on the support structure, the method further includes the following step: constructing a waterproof layer on the side wall opposite to the support structure.

[0010] In some examples of this application, the replacement support column is cast between the side wall and the support structure, including the following steps: in the height direction of the foundation pit, the replacement support column is cast from the bottom of the foundation pit upwards, so that the height of the top of the replacement support column is not lower than the height of the second pair of support beams, and the height of the bottom of the replacement support column is not higher than the height of the base plate.

[0011] In some examples of this application, after connecting the second pair of support beams between any two opposing side walls and before removing the first pair of support beams, the following steps are further included: erecting a disc-lock frame on the base plate, erecting the disc-lock frame so that its top end is located below the first pair of support beams and above the second pair of support beams, and ensuring that the erected disc-lock frame avoids the second pair of support beams; installing a top plate template at the upper end of the disc-lock frame, wherein the top plate template is used for shaping the top plate.

[0012] In some examples of this application, after removing the first pair of support beams and then constructing the top slab on the side wall, the steps further include: backfilling and compacting soil between the side wall and the support structure; and removing the second pair of support beams.

[0013] In some examples of this application, the step of connecting a second pair of support beams between any two opposing side walls and applying a pre-supporting force along the axial direction of the second pair of support beams between the two opposing side walls further includes the following steps: presetting a first stress threshold, a second stress threshold, a first tilt threshold, a second tilt threshold, a displacement threshold, and a deflection threshold; reading the horizontal stress value and / or tilt and / or horizontal displacement of the replacement support column, and determining whether the horizontal stress value of the replacement support column is greater than the first preset stress threshold, and / or determining whether the tilt of the replacement support column is greater than the first preset tilt threshold, and / or determining whether the horizontal displacement of the replacement support column is greater than the preset displacement threshold; The axial stress value and / or inclination and / or deflection of the second pair of support beams are read, and it is determined whether the axial stress value of the second pair of support beams is greater than a second preset stress threshold, and / or whether the inclination of the second pair of support beams is greater than a second preset inclination threshold, and / or whether the deflection of the second pair of support beams is greater than a preset deflection threshold; when it is determined that at least one of the horizontal stress value, inclination and horizontal displacement of the replacement support column is greater than the corresponding preset value, and / or when at least one of the axial stress value, inclination and deflection of the second pair of support beams is greater than the corresponding preset value, an early warning message is issued.

[0014] In some examples of this application, after issuing the warning information, the following steps are also included: reducing the water level around the foundation pit until the horizontal stress value, inclination and horizontal displacement of the replacement support column are less than the corresponding first preset stress threshold, first preset inclination threshold and preset displacement threshold, respectively, and the axial stress value, inclination and deflection of the second pair of support beams are less than the corresponding second preset stress threshold, second preset inclination threshold and preset deflection threshold, respectively.

[0015] According to the underground tunnel of this application, the underground tunnel is constructed using the above-mentioned foundation pit replacement construction method. The underground tunnel includes a top slab, a bottom slab, and sidewalls. The top slab and the bottom slab are spaced apart along the height direction of the underground tunnel, and the sidewalls are connected between the top slab and the bottom slab.

[0016] According to this application, the underground tunnel is constructed using a pit-support replacement method. After the bottom slab and sidewalls of the underground tunnel are formed, replacement columns are poured between the sidewalls and the support structure. A second pair of support beams is connected between the two opposite sidewalls. When the first pair of support beams is removed, and the support structure is squeezed into the pit by soil pressure, the support structure can transmit the compressive force to the sidewalls of the structure through the replacement columns, and further to the second pair of support beams through the sidewalls. The second pair of support beams can provide support for the two opposite sidewalls and form a force transmission path between the two opposite inner sidewalls of the pit. This makes the compressive force on the sidewalls more uniform, avoids local stress concentration in the sidewalls, prevents cracking and deformation of the sidewalls, and thus improves the construction quality and safety of the underground tunnel. Furthermore, the second pair of support beams is located below the top wall of the sidewalls, that is, in the construction area where the second pair of support beams do not pass through the top slab of the underground tunnel. While indirectly supporting the support structure, the second pair of support beams can ensure the smooth construction and formation of the top slab.

[0017] In some examples of this application, the second pair of support beams includes a fixed member, a support member, and a movable member. The support member is disposed between the fixed member and the movable member, and extends along the first direction. The wall surface of the fixed member away from the support member is constructed as a first fixing surface. A first fixing plate is pre-embedded and installed on the side wall corresponding to the fixed member. The first fixing surface abuts against and is fixedly connected to the first fixing plate. The wall surface of the movable member away from the support member is constructed as a second fixing surface. A second fixing plate is pre-embedded and installed on the side wall corresponding to the movable member. The second fixing surface abuts against and is fixedly connected to the second fixing plate. The support member and the movable member are connected and cooperated by a hydraulic telescopic member, which can extend and retract along the first direction. The support member includes at least one support rod extending along the first direction. When there are multiple support rods, the multiple support rods are connected sequentially. The support rod located at the head of the multiple support rods is connected and cooperated with the fixed member. The support rod located at the tail of the multiple support rods is connected and cooperated with the movable member.

[0018] In some examples of this application, the connector is a connecting steel bar, one end of which extends into the support structure through a rebar anchor, and the other end of which extends into the replacement support column during the casting of the replacement support column, so that the connecting steel bar connects the replacement support column and the support structure. Attached Figure Description

[0019] Figure 1 This is a flowchart of the first embodiment of the foundation pit replacement support construction method according to the present application; Figure 2 This is a flowchart of a second embodiment of the foundation pit replacement support construction method according to the present application; Figure 3 This is a flowchart of a third embodiment of the foundation pit replacement support construction method according to the present application. Figure 4 This is a flowchart of the fourth embodiment of the foundation pit replacement support construction method of this application; Figure 5 This is a flowchart of the fifth implementation method of the foundation pit replacement support construction method in this application; Figure 6 This is a cross-sectional view of an underground structure constructed using the foundation pit replacement construction method of the present application embodiment before performing step S1. Figure 7 This is a cross-sectional view of an underground structure constructed using the foundation pit replacement construction method of the present application after performing step S1; Figure 8 This is a cross-sectional view of an underground structure constructed using the foundation pit replacement construction method of the present application after performing step S3; Figure 9 This is a partial top view of an underground structure constructed using the foundation pit replacement construction method of the present application embodiment after performing step S3; Figure 10 This is a cross-sectional view of an underground structure constructed using the foundation pit replacement construction method of this application after the removal of the first pair of support beams; Figure 11 This is a cross-sectional view of an underground building constructed using the foundation pit replacement construction method of the present application after the top slab is formed by construction on the side walls; Figure 12 This is a cross-sectional view of an underground structure constructed using the foundation pit replacement construction method according to the embodiments of this application after construction is completed; Figure 13 This is a cross-sectional view of the underground structure when the top slab interferes with the first pair of support beams during construction. Figure 14 This is a front view of the second pair of support beams in an embodiment of this application; Figure 15 This is a front view of the support rod according to an embodiment of this application.

[0020] In the diagram, 100 represents the foundation pit. 1. Support structure; 2. First pair of support beams; 3. Base plate; 4. Side walls; 5. Replacement support columns; 6. Second pair of support beams; 61. Fixing component; 62. Support component; 621. Support rod; 63. Movable component; 64. Hydraulic telescopic component; 7. Top slab. Detailed Implementation

[0021] The specific embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application.

[0022] like Figures 1-5 As shown in the embodiment of this application, a method for constructing a foundation pit support replacement structure is disclosed. This method can be used for the construction of underground structures, such as basements or underground tunnels. The underground structure is constructed within a foundation pit 100. In a first direction perpendicular to the height of the foundation pit 100, two opposing inner walls of the foundation pit 100 are provided with support structures 1. Taking an underground tunnel as an example, as... Figures 6-8 , Figures 10-12 As shown, the height direction of the foundation pit 100 can be indicated by... Figure 7 In the context of vertical direction, the first direction of the excavation pit 100 can refer to its width direction. The width direction of the excavation pit 100 is the same as the width direction of the road, i.e. Figure 7 The left and right directions in the middle.

[0023] like Figure 6 As shown, the support structure 1 extends along the height direction of the foundation pit 100 and is inserted below the bottom wall of the foundation pit 100. The support structure 1 can be a support pile or a support wall. A first pair of support beams 2 connects two opposing support structures 1, as shown in the diagram. Figure 1 As shown, the foundation pit replacement support construction method according to an embodiment of this application includes the following steps: like Figure 7 As shown, S1, a base plate 3 is poured on the bottom wall of the foundation pit 100, and then at least two side walls 4 are poured upward on the base plate 3. The top wall height of the cast side wall 4 is not higher than the height of the first pair of support beams 2. The two side walls 4 are respectively opposite to the support structure 1 on the corresponding side of the foundation pit 100 along the first direction of the foundation pit 100 and are spaced apart. Multiple side walls 4 are arranged sequentially and spaced apart along the first direction of the foundation pit 100.

[0024] S2. Install connectors on the support structure 1, and cast a replacement support column 5 between the side wall 4 and the support structure 1. This allows the replacement support column 5 to be fixedly connected to the support structure 1 via the connectors. By fixing the replacement support column 5 to the support structure 1, a reliable force transmission path can be formed between them. Furthermore, the replacement support column 5 is not connected to the structural steel reinforcement within the side wall 4. In some embodiments, the replacement support column 5 is tightly fitted to the side wall 4. In other embodiments, force transmission components can be pre-embedded within the side wall 4. This design avoids the replacement support column 5 damaging the outer wall surface of the side wall 4 due to a rigid connection, thus preventing damage to the waterproofing layer and other components of the outer wall surface. The replacement support column 5 enables the transmission of the compressive force generated by the soil pressure on the support structure 1 to the side wall 4.

[0025] In some specific application scenarios, the cross-sectional shape of the replacement support column 5 in the direction perpendicular to the height of the foundation pit 100 can be rectangular, and the width of the replacement support column 5 in the second direction of the foundation pit 100 can be 800mm. It should be noted that the height direction, the first direction, and the second direction of the foundation pit 100 are set perpendicular to each other, and the second direction of the foundation pit 100 can refer to... Figure 9 The front and rear directions are specified. Furthermore, the replacement support column 5 can be formed by casting plain concrete with a concrete strength of C30 to C40. In other embodiments, reinforcement can be added inside the replacement support column 5 to improve its ability to withstand tensile and shear stresses.

[0026] like Figure 8 , Figure 9 As shown in Figure S3, a second pair of support beams 6 are connected between any two opposite side walls 4. The second pair of support beams 6 apply a pre-supporting force along their axial direction between the two opposite side walls 4. This provides support for the two side walls 4, ensuring that the side walls 4 are subjected to the compressive force of the support structure 1, resulting in a balanced force on both sides of the side walls 4 in the first direction of the pit 100. By supporting the second pair of support beams 6 between the two opposite side walls 4, the support structure 1, the support column 5, the side walls 4, and the second pair of support beams 6 together form a continuous force transmission path between the two opposite inner walls of the pit 100. This makes the compressive force on each side wall 4 of the underground structure more uniform, avoids local stress concentration in the side walls 4, prevents cracking and deformation of the side walls 4, and thus improves construction quality and safety.

[0027] Furthermore, the second pair of support beams 6 is located below the top wall of the side wall 4, meaning that the second pair of support beams 6 does not pass through the construction area of ​​the top slab 7 above the side wall 4.

[0028] like Figure 10 , Figure 11 As shown, S4, remove the first pair of support beams 2, and then construct the top slab 7 on the side wall 4. (As shown) Figure 13As shown, if the first pair of support beams 2 are not removed before the construction of the top slab 7, it will cause interference between the first pair of support beams 2 and the top slab 7. Therefore, in this application, by removing the first pair of support beams 2 and using the second pair of support beams 6 to indirectly support the support structure 1 on both sides of the foundation pit 100, the top slab 7 can be successfully constructed and formed since the first pair of support beams 2 no longer passes through the construction area of ​​the top slab 7.

[0029] like Figure 9 , Figure 14 , Figure 15 As shown, in some embodiments of this application, the second pair of support beams 6 may be made of steel, and the second pair of support beams 6 includes a fixing member 61, a support member 62, and a movable member 63. The support member 62 is disposed between the fixing member 61 and the movable member 63, and the support member 62 is along the first direction of the foundation pit 100 (i.e., Figure 8 The fastener 61 extends in the left and right directions. The wall surface of the fastener 61 away from the support 62 is constructed as the first fixing surface. A first fixing plate is pre-embedded on the side wall 4 corresponding to the fastener 61. The first fixing surface and the first fixing plate abut against and are fixedly connected. In some specific embodiments, the first fixing surface and the first fixing plate can be fixedly connected by welding. However, this application is not limited to this. For example, in some other embodiments, a first mounting hole is provided on the fastener 61. The first mounting hole passes through the first fixing surface. A second mounting hole is provided on the first fixing plate. Fasteners such as bolts pass through the first mounting hole and the second mounting hole to fix the fastener 61 to the corresponding side wall 4.

[0030] The wall surface of the movable part 63 away from the support part 62 is constructed as a second fixing surface. A second fixing plate is pre-embedded on the side wall 4 corresponding to the movable part 63. The second fixing surface and the second fixing plate are abutted and fixedly connected. Similarly, after the second fixing surface and the second fixing plate are abutted and engaged, the movable part 63 and the corresponding side wall 4 can be fixedly connected by welding or screwing.

[0031] The support member 62 and the movable member 63 are connected and cooperated by a hydraulic telescopic member 64, which can extend and retract along a first direction. By extending and retracting the hydraulic telescopic member 64, the axial length of the second pair of support beams 6 can be extended and retracted to adapt to the spacing between the corresponding two side walls 4, thereby enabling mutual anti-locking cooperation between the first fixed surface and the first fixed plate, and between the second fixed surface and the second fixed plate. Furthermore, the hydraulic telescopic member 64 can act as a jack, effectively bearing the load to prevent the second pair of support beams 6 from retracting under pressure. This allows the second pair of support beams 6 to reliably support the side walls 4. The hydraulic telescopic member 64 also applies a pre-support force to the two opposite side walls, reducing the sudden load change on the side walls 4 when the first pair of support beams 6 are removed. This reduces the instantaneous displacement of the side walls 4 and the support structure 1, and also avoids local stress concentration in the side walls 4 and the support structure 1.

[0032] Furthermore, the support member 62 includes at least one support rod 621 extending along the first direction. When there are multiple support rods 621, the multiple support rods 621 are connected sequentially. The support rod 621 located at the head of the multiple support rods 621 is connected and cooperates with the fixing member 61, and the support rod 621 located at the tail of the multiple support rods 621 is connected and cooperates with the movable member 63. Each support rod 621 uses the same length and material. By increasing and decreasing the number of support rods 621, the axial length dimension of the second pair of support beams 6 can be correspondingly extended and shortened. This allows the second pair of support beams 6 to adapt to the interval distance between two opposite side walls 4 under different construction environments, thereby reducing the manufacturing, transportation and installation difficulty of the second pair of support beams 6 and helping to improve the versatility and construction convenience of the second pair of support beams 6.

[0033] like Figure 2 As shown, in some embodiments of this application, after pouring the bottom slab 3 and at least two side walls 4 within the foundation pit 100 and before installing the connectors on the support structure 1, the following steps are also included: S11. Construct a waterproof layer on the side wall 4 opposite to the support structure 1. By setting the waterproof layer construction step before pouring the replacement column 5, the construction difficulty of the waterproof layer can be avoided by the replacement column 5 obstructing the side wall 4 after its formation. At the same time, after the replacement column 5 is poured, the replacement column 5 and the waterproof layer are fitted together, so there is no rigid connection between the replacement column 5 and the waterproof layer. When the replacement column 5 is displaced or deformed, this can reduce the damage to the waterproof layer caused by the replacement column 5.

[0034] like Figure 7 As shown, in some embodiments of this application, a replacement support column 5 is formed by casting a concrete between the side wall 4 and the support structure 1, including the following steps: S21. In the height direction of the foundation pit 100, a replacement support column 5 is formed by pouring water from the bottom of the foundation pit 100 upwards, so that the height of the top of the replacement support column 5 is not lower than the height of the second pair of support beams 6, and the height of the bottom of the replacement support column 5 is not higher than the height of the bottom plate 3.

[0035] By extending one end of the replacement support column 5 toward the second pair of support beams 6, a portion of the compressive force exerted by the support structure 1 on the replacement support column 5 can be transmitted toward the second pair of support beams 6. Furthermore, the pressure exerted by the replacement support column 5 on the side wall 4 is approximately the same as the supporting force exerted by the second pair of support beams 6 on the side wall 4. This can reduce the bending moment on the side wall 4, thereby further preventing cracking and deformation of the side wall 4.

[0036] Furthermore, by extending the other end of the replacement support column 5 toward the base plate 3, a continuous force transmission path can be formed between the replacement support column 5, the base plate 3, and the bottom wall of the pit 100. Another part of the compressive force exerted by the support structure 1 on the replacement support column 5 can be transmitted to the bottom of the pit 100, thereby reducing the pressure on the side wall 4 and the second pair of support beams 6, and further reducing the cracking and deformation problems of the side wall 4. In addition, two force transmission paths are formed in the pit 100. Specifically, the replacement support column 5, the side wall 4, and the second pair of support beams 6 together form a transverse force transmission path, and the replacement support column 5, the base plate 3, and the bottom wall of the pit 100 together form a longitudinal force transmission path. The two force transmission paths can improve the stability of the pit 100, thereby effectively improving the construction quality and construction safety.

[0037] like Figure 3 As shown, in some embodiments of this application, after connecting the second pair of support beams 6 between any two opposing side walls 4 and before removing the first pair of support beams 2, the following steps are also included: S31. Erect a disc buckle frame on the base plate 3, and set the top of the disc buckle frame below the first pair of support beams 2 and above the second pair of support beams 6, and make the erected disc buckle frame avoid the second pair of support beams 6.

[0038] S32. Install the top plate template at the upper end of the disc buckle frame, wherein the top plate template is used for the forming of the top plate 7.

[0039] The modular scaffolding includes horizontal and vertical poles that are interconnected. A second pair of support beams 6 are horizontally positioned and pass through the gaps between the horizontal and vertical poles, ensuring that the second pair of support beams 6 do not interfere with the modular scaffolding and preventing collapse during the forming of the top slab 7. Furthermore, by erecting the modular scaffolding and top slab formwork before removing the first pair of support beams 2, the top slab formwork can be erected in advance while retaining the supporting function of the first pair of support beams 2. This shortens the construction time from the removal of the first pair of support beams 2 to the forming of the top slab 7, thus ensuring construction safety.

[0040] like Figure 4 As shown, in some embodiments of this application, after removing the first pair of support beams 2 and then constructing the top slab 7 on the side wall 4, the following steps are also included: S5. Backfill and compact the soil between the side wall 4 and the support structure 1.

[0041] S6. Remove the second pair of support beams 6.

[0042] Among them, such as Figure 12As shown, after the completion of the top slab 7 of the underground structure, the underground structure forms a complete load-bearing structure. By backfilling soil between the side wall 4 and the support structure 1, the gap between the side wall 4 and the support structure 1 can be filled, increasing the stress-bearing area between the foundation pit 100 and the side wall 4, thus avoiding local stress concentration in the side wall 4. Furthermore, by removing the second pair of support beams 6, the second pair of support beams 6 can be recovered, and the second pair of support beams 6 can be prevented from occupying the internal space of the underground structure for a long period of time.

[0043] In some embodiments of this application, the connector is a connecting steel bar. One end of the connecting steel bar extends into the support structure 1 through rebar installation, and the other end of the connecting steel bar extends into the replacement support column 5 during the pouring of the replacement support column 5, so that the connecting steel bar connects the replacement support column 5 and the support structure 1. This design can improve the connection strength between the support structure 1 and the replacement support column 5, and can make the support structure 1 and the replacement support column 5 form an integrated force transmission structure. This allows the soil compression force on the support structure 1 to be stably transmitted to the replacement support column 5, and further transmitted to the side wall 4 and the bottom slab 3. It can also reduce the risk of separation or relative displacement at the connection between the support structure 1 and the replacement support column 5, thereby improving the construction safety when using the foundation pit replacement support construction method.

[0044] like Figure 5 As shown, in some embodiments of this application, a second pair of support beams 6 are connected between any two opposing side walls 4, and a pre-support force along the axial direction of the second pair of support beams 6 is applied between the two opposing side walls 4 using the second pair of support beams 6. The method further includes the following steps: S7. Preset the first stress threshold, the second stress threshold, the first tilt threshold, the second tilt threshold, the displacement threshold, and the deflection threshold.

[0045] S8. Read the horizontal stress value and / or tilt and / or horizontal displacement of the replacement support column 5, and determine whether the horizontal stress value of the replacement support column 5 is greater than the first preset stress threshold, and / or determine whether the tilt of the replacement support column 5 is greater than the first preset tilt threshold, and / or determine whether the horizontal displacement of the replacement support column 5 is greater than the preset displacement threshold.

[0046] By pre-embedding stress gauges inside the support column 5 and reading their readings, the horizontal stress value of the support column 5 can be obtained. In some specific implementations, the height of the stress gauges on the support column 5 is the same as the height of the central axis of the second pair of support beams 6. This arrangement ensures that the area detected by the stress gauges is the area of ​​maximum stress in the support column 5. It should be noted that the specific structure of the stress gauges has been widely disclosed in the prior art and will not be elaborated here. By recording the current horizontal stress value of the support column 5 by computer or construction personnel and comparing the current horizontal stress value with a first stress threshold, it can be determined whether the horizontal stress value of the support column 5 is greater than the first preset stress threshold. The first preset stress threshold can be calculated based on the building type, construction materials, foundation pit 100 dimensions, soil materials, etc. When the horizontal stress value of the support column 5 is greater than the first preset stress threshold, it proves that the support structure 1 and the support column 5 are under abnormal stress.

[0047] Accordingly, by pre-embedding an inclination sensor in the replacement support column 5, the inclination sensor can obtain the inclination of the replacement support column 5. The current inclination of the replacement support column 5 can be recorded by a computer or construction personnel, and the current inclination can be compared with a first preset inclination threshold. It can be determined whether the inclination of the replacement support column 5 is greater than the first preset inclination threshold. The first preset inclination threshold can be determined according to the construction safety requirements. When the inclination of the replacement support column 5 is greater than the first preset inclination threshold, it proves that the inclination of the replacement support column 5 is abnormal and does not meet the construction safety requirements.

[0048] Furthermore, by setting multiple displacement monitoring points on the surface of the replacement support column 5, the horizontal displacement of the replacement support column 5 can be read and determined using devices such as rulers. The current horizontal displacement of the replacement support column 5 can be recorded by a computer or by construction personnel, and compared with a preset displacement threshold. This allows it to be determined whether the horizontal displacement of the replacement support column 5 is greater than the preset displacement threshold. The preset displacement threshold can be determined according to construction safety requirements. When the horizontal displacement of the replacement support column 5 is greater than the preset displacement threshold, it proves that the inward deformation of the foundation pit 100 is abnormal and does not meet the construction safety requirements.

[0049] S9. Read the axial stress value and / or inclination and / or deflection of the second pair of support beams 6, and determine whether the axial stress value of the second pair of support beams 6 is greater than the second preset stress threshold, and / or determine whether the inclination of the second pair of support beams 6 is greater than the second preset inclination threshold, and / or determine whether the deflection of the second pair of support beams 6 is greater than the preset deflection threshold.

[0050] By installing a stress gauge at the hydraulic telescopic component 64 of the second pair of support beams 6, the axial stress value of the second pair of support beams 6 can be read. When the axial stress value of the second pair of support beams 6 is greater than the second preset stress threshold, it proves that the second pair of support beams 6 is abnormally compressed and the supporting force of the second pair of support beams 6 does not meet the supporting requirements of the side wall 4.

[0051] By installing an inclination sensor at the hydraulic telescopic component 64 of the second pair of support beams 6, the inclination of the second pair of support beams 6 can be obtained. When the inclination of the second pair of support beams 6 is greater than the second preset inclination threshold, it proves that the second pair of support beams 6 deflects too much and there is a high risk of slippage between the second pair of support beams 6 and the side wall 4, which will affect construction safety.

[0052] By arranging multiple displacement monitoring points along the axial direction of the second pair of support beams 6 and measuring the displacement of each monitoring point using a ruler or other device, the deflection of the second pair of support beams 6 can be determined. This allows us to judge and determine whether the deflection of the second pair of support beams 6 is greater than a preset deflection threshold. When the deflection of the second pair of support beams 6 is greater than the preset deflection threshold, it proves that the second pair of support beams 6 is severely deformed and does not meet the construction safety requirements.

[0053] S10. When at least one of the horizontal stress value, inclination, and horizontal displacement of the support column 5 is determined to be greater than the corresponding preset value, and / or when at least one of the axial stress value, inclination, and deflection of the second pair of support beams 6 is determined to be greater than the corresponding preset value, an early warning message is issued. When it is determined that at least one of the above indicators exceeds the corresponding preset value, it proves that the compressive force of the soil acting on the underground structure through the support structure 1 is too large, and there is a risk in continuing construction. The early warning message can be issued through an alarm device or by construction personnel. Construction can continue after it is determined that construction safety is not affected.

[0054] Furthermore, such as Figure 5 As shown, after determining that at least one of the horizontal stress value, inclination, and horizontal displacement of the support column 5 is greater than the corresponding preset value, and / or when at least one of the axial stress value, inclination, and deflection of the second pair of support beams 6 is greater than the corresponding preset value, and after issuing a warning message, the following steps are also included: S20. Lower the water level around the foundation pit 100 until the horizontal stress, inclination, and horizontal displacement of the replacement support column 5 are less than the corresponding first preset stress threshold, first preset inclination threshold, and preset displacement threshold, respectively, and the axial stress, inclination, and deflection of the second pair of support beams 6 are less than the corresponding second preset stress threshold, second preset inclination threshold, and preset deflection threshold, respectively. Lowering the water level around the foundation pit 100 (i.e., lowering the groundwater level) reduces groundwater pressure, thereby reducing pore water pressure and hydrostatic pressure outside the support structure 1. This reduces the pressure exerted by the soil on the sidewall 4 through the support structure 1. Furthermore, lowering the water level around the foundation pit 100 improves soil stability, making it less likely for the soil to slide into the foundation pit 100, and also helps reduce pressure on the sidewall 4. Thus, the working state of the replacement support column 5 and the second pair of support beams 6 meets construction safety requirements.

[0055] Based on this, such as Figure 12As shown, this application further discloses an underground tunnel. According to an embodiment of this application, the underground tunnel is constructed using the foundation pit replacement support construction method described above. The underground tunnel is constructed within a foundation pit 100. The first direction of the foundation pit 100 is the road width direction of the underground tunnel. The underground tunnel includes a top slab 7, a bottom slab 3, and side walls 4. The top slab 7 and the bottom slab 3 are spaced apart along the height direction of the underground tunnel. The side walls 4 connect the top slab 7 and the bottom slab 3. During the construction of the underground tunnel within the foundation pit 100, replacement support columns 5 are poured between the side walls 4 and the support structure 1, and in relative... The two side walls 4 are connected by a second pair of support beams 6. When the first pair of support beams 2 are removed, and the support structure 1 is squeezed into the pit 100 by the soil pressure, the support structure 1 can transmit the squeezing force to the side walls 4 through the replacement support columns 5, and further transmit it to the second pair of support beams 6 through the side walls 4. The second pair of support beams 6 can provide support for the two opposite side walls 4 and form a force transmission path between the two opposite inner side walls of the pit 100. This makes the squeezing force on the side walls 4 more uniform, avoids local stress concentration in the side walls 4, prevents cracking and deformation of the side walls 4, and thus improves construction quality and construction safety. Furthermore, the second pair of support beams 6 is located below the top wall of the side walls 4, that is, the second pair of support beams 6 does not pass through the construction area of ​​the top slab 7. While indirectly supporting the support structure 1, the second pair of support beams 6 can ensure the smooth construction and shaping of the top slab 7.

[0056] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A method for constructing a foundation pit support replacement system, characterized in that, In a first direction perpendicular to the height of the foundation pit, two opposing inner sidewalls of the foundation pit are provided with support structures. The support structures extend along the height of the foundation pit and are inserted below the bottom wall of the foundation pit. A first pair of support beams connects the two opposing support structures. The foundation pit support replacement construction method includes the following steps: A base slab is poured on the bottom wall of the foundation pit, and then at least two side walls are poured upwards on the base slab. The top wall height of the cast side walls is not higher than the height of the first pair of support beams. The two side walls are respectively opposite to the support structure on the corresponding side of the foundation pit along the first direction and are spaced apart. Multiple side walls are arranged sequentially and spaced apart along the first direction. Connectors are installed on the support structure, and a replacement support column is cast between the side wall and the support structure so that the replacement support column is fixedly connected to the support structure through the connectors. A second pair of support beams is connected between any two opposing side walls, and a pre-support force along the axial direction of the second pair of support beams is applied between the two opposing side walls using the second pair of support beams, the second pair of support beams being located below the top wall of the side wall; Remove the first pair of support beams, and then construct the top slab on the side wall.

2. The foundation pit support replacement construction method according to claim 1, characterized in that, After pouring the bottom slab and at least two side walls in the foundation pit, and before installing the connectors on the support structure, the method further includes the following steps: A waterproof layer is constructed on the side wall opposite to the support structure.

3. The foundation pit support replacement construction method according to claim 1, characterized in that, Casting a replacement support column between the side wall and the support structure includes the following steps: In the height direction of the foundation pit, the replacement support column is formed by pouring water from the bottom of the foundation pit upwards, so that the height of the top of the replacement support column is not lower than the height of the second pair of support beams, and the height of the bottom of the replacement support column is not higher than the height of the base plate.

4. The foundation pit support replacement construction method according to claim 1, characterized in that, After connecting the second pair of support beams between any two opposing side walls and before removing the first pair of support beams, the procedure further includes the following steps: A disc buckle frame is erected on the base plate, with the top of the disc buckle frame positioned below the first pair of support beams and above the second pair of support beams, and the erected disc buckle frame is positioned to avoid the second pair of support beams. A top plate template is installed at the upper end of the disc buckle frame, wherein the top plate template is used for forming the top plate.

5. The foundation pit support replacement construction method according to claim 1, characterized in that, After removing the first pair of support beams and then constructing the roof slab on the side wall, the following steps are also included: Backfill and compact the soil between the side wall and the support structure; Remove the second pair of support beams.

6. The foundation pit support replacement construction method according to claim 1, characterized in that, The method of connecting a second pair of support beams between any two opposing side walls, and applying a pre-support force along the axial direction of the second pair of support beams between the two opposing side walls using the second pair of support beams, further includes the following steps: The system presets a first stress threshold, a second stress threshold, a first tilt threshold, a second tilt threshold, a displacement threshold, and a deflection threshold. Read the horizontal stress value and / or tilt and / or horizontal displacement of the replacement support column, and determine whether the horizontal stress value of the replacement support column is greater than a first preset stress threshold, and / or determine whether the tilt of the replacement support column is greater than a first preset tilt threshold, and / or determine whether the horizontal displacement of the replacement support column is greater than a preset displacement threshold. Read the axial stress value and / or tilt and / or deflection of the second pair of support beams, and determine whether the axial stress value of the second pair of support beams is greater than the second preset stress threshold, and / or determine whether the tilt of the second pair of support beams is greater than the second preset tilt threshold, and / or determine whether the deflection of the second pair of support beams is greater than the preset deflection threshold. When it is determined that at least one of the horizontal stress value, inclination, and horizontal displacement of the replacement support column is greater than the corresponding preset value, and / or when at least one of the axial stress value, inclination, and deflection of the second pair of support beams is greater than the corresponding preset value, an early warning message is issued.

7. The foundation pit support replacement construction method according to claim 6, characterized in that, After issuing the warning information, the following steps are also included: Lower the water level around the foundation pit until the horizontal stress value, inclination, and horizontal displacement of the replacement support column are less than the corresponding first preset stress threshold, first preset inclination threshold, and preset displacement threshold, respectively, and the axial stress value, inclination, and deflection of the second pair of support beams are less than the corresponding second preset stress threshold, second preset inclination threshold, and preset deflection threshold, respectively.

8. An underground tunnel, characterized in that, The underground tunnel is constructed using the foundation pit replacement construction method according to any one of claims 1-7. The underground tunnel includes a top slab, a bottom slab, and sidewalls. The top slab and the bottom slab are spaced apart along the height direction of the underground tunnel, and the sidewalls are connected between the top slab and the bottom slab.

9. The underground tunnel according to claim 8, characterized in that, The second pair of support beams includes a fixed member, a support member, and a movable member. The support member is disposed between the fixed member and the movable member and extends along the first direction. The wall surface of the fixed member away from the support member is constructed as a first fixing surface. A first fixing plate is pre-embedded and installed on the side wall corresponding to the fixed member. The first fixing surface and the first fixing plate are abutted and fixedly connected. The wall surface of the movable member away from the support member is constructed as a second fixing surface. A second fixing plate is pre-embedded and installed on the side wall corresponding to the movable member. The second fixing surface and the second fixing plate are abutted and fixedly connected. The support member and the movable member are connected and cooperated by a hydraulic telescopic member, which can extend and retract along the first direction; The support member includes at least one support rod extending along the first direction. When there are multiple support rods, the multiple support rods are connected in sequence. The support rod located at the head of the multiple support rods is connected and cooperates with the fixing member, and the support rod located at the tail of the multiple support rods is connected and cooperates with the movable member.

10. The underground tunnel according to claim 8, characterized in that, The connector is a connecting steel bar. One end of the connecting steel bar extends into the support structure through a rebar anchoring process, and the other end of the connecting steel bar extends into the replacement support column during the pouring of the replacement support column, so that the connecting steel bar connects the replacement support column and the support structure.

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