Bottom plate structure for reducing excavation depth of foundation pit of shield well and construction method

Abstract

The invention discloses a bottom plate structure for reducing the excavation depth of a shield well foundation pit and a construction method. The bottom plate structure comprises a first-stage bottom plate structure and a second-stage bottom plate structure. The first-stage bottom plate structure is arranged in the set depth of the shield well; the first-stage bottom plate structure is arranged firstly, and the second-stage bottom plate structure is arranged later; a groove is reserved in the first-stage bottom plate structure and can be used for supporting the shield tunneling machine to work; after the second-stage bottom plate structure is arranged, the groove is filled with the second-stage bottom plate structure. The novel bottom plate structure can be applied to the starting end or the receiving end of a shield well, the excavation depth of a foundation pit at the starting end or the receiving end of the shield well can be reduced, and the problem that the foundation pit excavation safety risk is likely to be caused due to the fact that the excavation depth of the shield well is increased due to one-time pouring of a sinking section bottom plate in the shield well is effectively solved. According to the construction method of the bottom plate structure, the novel bottom plate structure can be scientifically guided to be smoothly constructed, the construction difficulty can be reduced, and the construction safety and the construction efficiency can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of open-cut foundation pits, and particularly relates to a bottom plate structure and a construction method for reducing the excavation depth of a shield well foundation pit. Background Art

[0002] At present, for tunnels constructed by the shield method, the shield machine mostly starts from an open-cut shield well. To ensure the starting space of the shield machine, the elevation of the bottom plate at the starting end of the open-cut shield well is usually lower than that of the bottom plate in the standard section and adopts a sinking form. The bottom surface elevation of the bottom plate at the starting end of the shield well controls the excavation depth of the shield well foundation pit. It is common to use one-time pouring for the bottom plate of the sinking section at the starting end of the shield well. However, one-time pouring of the bottom plate of the sinking section will increase the excavation depth of the open-cut foundation pit. The increase in the excavation depth of the foundation pit will greatly increase the risk of foundation pit excavation. Especially in the karst cave development area of the limestone formation, the increase in the excavation depth of the open-cut shield well poses a very high engineering risk. At the same time, the increase in the excavation depth of the foundation pit will increase the risk of base water inrush and sand inrush, affecting the safety of foundation pit construction and easily posing a safety threat to the surrounding buildings and other environments. Once a safety risk occurs in the foundation pit excavation due to the increase in the excavation depth of the foundation pit (such as foundation pit collapse, base water inrush, sand inrush, settlement of surrounding buildings), it will not only increase the construction period and investment of the project construction, but also have an adverse impact on personal safety and public opinion.

[0003] At present, there is a lack of a bottom plate structure for reducing the excavation depth of a shield well foundation pit to solve the problem that one-time pouring of the bottom plate of the sinking section in the shield well leads to an increase in the excavation depth of the shield well and easily causes the risk of foundation pit excavation. At present, there is a lack of a construction method for the bottom plate structure to scientifically guide the construction of the new bottom plate structure, so as to reduce the construction difficulty, improve the construction safety and construction efficiency.

[0004] Therefore, a new technology is needed to solve the problem that there is a lack of a bottom plate structure for reducing the excavation depth of a shield well foundation pit in the prior art. A new technology is needed to solve the problem that there is a lack of a construction method for the bottom plate structure in the prior art. Summary of the Invention

[0005] To solve the above problems in the prior art, the present invention provides a bottom plate structure for reducing the excavation depth of a shield well foundation pit, which can be applied to the starting end or receiving end of the shield well. The newly designed bottom plate structure reduces the excavation depth of the shield well foundation pit and effectively solves the problem that one-time pouring of the bottom plate of the sinking section in the shield well leads to an increase in the excavation depth of the shield well and easily causes the risk of foundation pit excavation.

[0006] The present invention adopts the following technical solutions:

[0007] A bottom plate structure for reducing the excavation depth of a shield well foundation pit, comprising a first-stage bottom plate structure and a second-stage bottom plate structure; the first-stage bottom plate structure is arranged at a set depth of the shield well; the first-stage bottom plate structure is arranged first, and the second-stage bottom plate structure is arranged later; the first-stage bottom plate structure is provided with a groove for supporting the operation of the shield machine; after the second-stage bottom plate structure is arranged, it is filled in the groove.

[0008] Further, the planar area of the first-stage bottom plate structure is determined by the working space of the shield machine and the depth of the shield well;

[0009] The planar area of the groove in plan view is the planar area of the second-stage bottom plate structure;

[0010] The planar area of the second-stage bottom plate structure includes a first planar area and a second planar area, and the first planar area is adjacent to the second planar area;

[0011] The thickness of the second-stage bottom plate structure is determined by the outer diameter of the working space of the shield machine and the outer diameter of the shield segment;

[0012] Among them, the working space of the shield machine and the shield segment have a common center and a common center line.

[0013] Further, the first working width of the shield machine and the length of the working section of the shield machine form the working planar area of the shield machine;

[0014] The first planar area is greater than or equal to the working planar area of the shield machine;

[0015] The maximum width and the maximum length of the reaction frame of the shield machine form the reaction frame planar area of the shield machine;

[0016] The second planar area is greater than or equal to the reaction frame planar area of the shield machine.

[0017] Further, the first working width of the shield machine is determined by the chord length at which the outer diameter of the working space of the shield machine intersects the plate surface of the second-stage bottom plate structure.

[0018] Further, the elevation of the first-stage bottom plate structure includes a first-stage top elevation and a first-stage bottom elevation;

[0019] The elevation of the second-stage bottom plate structure includes a second-stage top elevation and a second-stage bottom elevation;

[0020] The first-stage top elevation is the same as the second-stage top elevation;

[0021] Among them, the elevation of the top surface of the first phase and the elevation of the top surface of the second phase are determined by the bottom elevation of the shield segment and are not higher than the bottom elevation of the shield segment; among them, the outer diameter of the shield segment is determined according to the clearance limit of the train; the bottom elevation of the shield segment is determined by the elevation of the track surface of the line; among them, the elevation of the track surface of the line is determined according to the line design and is the absolute elevation.

[0022] The bottom elevation of the first phase is determined by the thickness of the bottom slab structure of the first phase on the basis that the elevation of the top surface of the first phase has been determined; the thickness of the bottom slab structure of the first phase is determined by the working space of the shield machine and the depth of the shield shaft.

[0023] The bottom elevation of the second phase is determined by the bottom elevation of the working space of the shield machine; among them, the outer diameter of the working space of the shield machine is larger than the outer diameter of the shield segment; the bottom elevation of the working space of the shield machine is determined by the elevation of the track surface of the line.

[0024] Furthermore, the elevation of the top surface of the first phase and the elevation of the top surface of the second phase are both consistent with the bottom elevation of the shield segment.

[0025] The bottom elevation of the second phase is consistent with the bottom elevation of the working space of the shield machine.

[0026] The difference (taking the absolute value) between the elevation of the top surface of the second phase and the elevation of the bottom surface of the second phase is the thickness of the bottom slab structure of the second phase, that is, the depth of the groove; at the same time, the difference between the outer diameter of the working space of the shield machine and the outer diameter of the shield segment is consistent with the thickness of the bottom slab structure of the second phase.

[0027] Furthermore, a number of first-phase steel bars are arranged in the bottom slab structure of the first phase; the first-phase steel bars include first-phase bottom bars, first-phase middle bars, and first-phase top bars; the first-phase bottom bars, the first-phase middle bars, and the first-phase top bars are respectively arranged from top to bottom in the bottom slab structure of the first phase.

[0028] A number of second-phase steel bars are arranged in the bottom slab structure of the second phase; the second-phase steel bars include second-phase bottom bars and second-phase top bars; the second-phase bottom bars and the second-phase top bars are respectively arranged from top to bottom in the bottom slab structure of the second phase.

[0029] Among them, the second-phase top bars are connected to the first-phase middle bars through steel bar couplers.

[0030] The second-phase bottom bars are connected to the first-phase bottom bars through steel bar couplers.

[0031] Furthermore, a number of drain wells are provided in the bottom slab structure of the first phase.

[0032] Furthermore, a fine aggregate concrete protective layer, a waterproof coiled material, and a concrete cushion are provided under the bottom slab structure of the first phase; the concrete cushion, the waterproof coiled material, and the fine aggregate concrete protective layer are sequentially arranged from bottom to top under the bottom slab structure of the first phase.

[0033] Another object of the present invention is to provide a construction method for a floor slab structure to scientifically guide the construction of a new floor slab structure, so as to reduce the construction difficulty, improve the construction safety and construction efficiency.

[0034] A construction method for a floor slab structure, which is used for constructing the floor slab structure for reducing the excavation depth of a shield well foundation pit, is characterized by comprising the following steps:

[0035] S1. Determine the size of the first-stage floor slab structure, determine the size of the second-stage floor slab structure, calculate the steel reinforcement required for the first-stage floor slab structure, and calculate the steel reinforcement required for the second-stage floor slab structure according to the outer diameter of the shield segment, the outer diameter of the working space of the shield machine, the size of the reaction frame of the shield machine, the depth of the shield well and the engineering geology;

[0036] S2. Construct the cushion and waterproof structure under the first-stage floor slab structure;

[0037] S3. Bind the first-stage steel bars required for the first-stage floor slab structure;

[0038] S4. Reserve the steel bar connectors for connecting the first-stage middle steel bars of the first-stage floor slab structure with the second-stage top steel bars of the second-stage floor slab structure; reserve the steel bar connectors for connecting the first-stage bottom steel bars of the first-stage floor slab structure with the second-stage bottom steel bars of the second-stage floor slab structure; reserve the drain well on the first-stage floor slab structure;

[0039] S5. Pour the concrete required for the first-stage floor slab structure and form the groove;

[0040] S6. After the concrete of the first-stage floor slab structure reaches the strength, place the shield machine on the groove and carry out shield work;

[0041] S7. After the shield work is completed, chisel the wall of the groove, that is, chisel the concrete at the interface between the first-stage floor slab structure and the second-stage floor slab structure. Then, bind the second-stage top steel bars and second-stage bottom steel bars of the second-stage floor slab structure, and screw the second-stage top steel bars and second-stage bottom steel bars into the reserved steel bar connectors respectively, so that the second-stage top steel bars are mechanically connected with the first-stage middle steel bars and the second-stage bottom steel bars are mechanically connected with the first-stage bottom steel bars;

[0042] S8. After the connection of the second-stage steel bars of the second-stage floor slab structure is completed, pour the concrete required for the second-stage floor slab structure;

[0043] S9. After the construction is completed, seal the drain well.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] A floor slab structure for reducing the excavation depth of a shield well foundation pit is cast in two stages. The structure is divided into a first-stage floor slab structure and a second-stage floor slab structure. Among them, the first-stage floor slab structure is arranged first, and the second-stage floor slab structure is arranged later. A groove is reserved in the first-stage floor slab structure, and this groove can be used to support the operation of the shield machine. After the second-stage floor slab structure is set, it is filled in the groove. This structure is arranged in sequence with the first-stage floor slab structure and the second-stage floor slab structure. The reserved groove has a depth. Compared with the conventional one-time integral casting of the floor slab, the newly designed floor slab structure of the present invention can reduce the downward excavation depth of the shield well foundation pit. Specifically, the present invention controls the top elevation of the "first-stage floor slab structure and the second-stage floor slab structure" with the bottom elevation of the shield segment, and controls the bottom elevation of the second-stage floor slab structure with the bottom elevation of the shield machine working space. Compared with the conventional one-time integral casting of the floor slab, the maximum reduction in the excavation depth of the foundation pit by the present invention is: "the absolute value of the difference between the bottom elevation of the shield machine working space and the bottom elevation of the shield segment".

[0046] The newly designed floor slab structure of the present invention realizes the reduction of the excavation depth of the shield well foundation pit, can significantly reduce the risks of base water inrush and sand inrush, reduce the construction risks of the project itself and the construction impact on surrounding buildings; at the same time, since the excavation depth of the foundation pit is reduced, the length of the diaphragm wall of the retaining structure, the length of the structural side wall and the thickness of the concrete backfill in the sinking section of the shield well can be reduced, reducing the construction cost and improving the construction safety; the present invention has remarkable social and economic benefits.

[0047] A floor slab structure for reducing the excavation depth of a shield well foundation pit of the present invention can be applied to the starting end or the receiving end of the shield well. This newly designed floor slab structure reduces the excavation depth of the foundation pit at the starting end or the receiving end of the shield well, and effectively solves the problem that the excavation depth of the shield well increases due to the one-time casting of the floor slab in the sinking section of the shield well, which is likely to cause the risk of foundation pit excavation.

[0048] A construction method of a floor slab structure of the present invention can scientifically guide the construction of the above-mentioned new floor slab structure, can reduce the construction difficulty, improve the construction safety and construction efficiency, and effectively avoid the construction quality problems and safety problems caused by the disordered construction procedures of workers due to insufficient cognition. Description of the Drawings

[0049] The following further details the technology of the present invention in conjunction with the drawings and specific embodiments:

[0050] Figure 1 It is a design relationship diagram of the first-stage floor slab structure, the second-stage floor slab structure, the drainage well, the shield machine working space, the shield segment, the track surface of the line, the cushion layer and the waterproof structure of the present invention;

[0051] Figure 2 It is a front cross-sectional view of the shield working space on the groove of the first-stage floor slab structure of the present invention;

[0052] Figure 3 It is a schematic cross-sectional view of the segment of the present invention on the second-stage floor structure.

[0053] Figure 4 It is a schematic layout diagram of the first-stage steel bars in the first-stage floor structure of the present invention.

[0054] Figure 5 It is a schematic layout diagram of the second-stage steel bars in the second-stage floor structure of the present invention.

[0055] Figure 6 It is Figure 5 A partial enlarged view at V.

[0056] Figure 7 It is a schematic plan view (top view) of the working plane area of the shield machine and the reaction frame plane area of the shield machine of the present invention.

[0057] Figure 8 It is Figure 7 A vertical sectional view at U-U.

[0058] Figure 9 It is Figure 8 A schematic diagram (simplified schematic diagram) showing the depth of the shield well foundation pit.

[0059] Figure 10 It is a schematic diagram for comparing the foundation pit excavation depth of the conventional floor and the floor structure of the present invention.

[0060] Reference numerals:

[0061] 1 - Floor structure; V - Local enlarged view label; U-U - Cross-sectional view symbol;

[0062] 11 - First-stage floor structure; A - Plane area; M1 - First-stage top elevation; M2 - First-stage bottom elevation; Q - Cushion and waterproof structure; T2 - Thickness;

[0063] 12 - Second-stage floor structure; B - Plane area; B1 - First plane area; B2 - Second plane area; T1 - Thickness; N1 - Second-stage top elevation; N2 - Second-stage bottom elevation;

[0064] 13 - Groove; H1 - Depth;

[0065] 2 - Shield machine working space; R1 - Outer diameter of the shield machine working space; D1 - First working width of the shield machine; L1 - Working section length of the shield machine; E - Shield machine working plane area; D2 - Maximum width of the shield machine reaction frame; L2 - Maximum length of the shield machine reaction frame; F - Shield machine reaction frame plane area; P3 - Bottom elevation of the shield machine working space;

[0066] 3 - Shield segment; R2 - Outer diameter of shield segment; G - Chord length; P1 - Bottom elevation of shield segment;

[0067] H - Depth of shield shaft; C - Center of circle; K - Center line; P2 - Elevation of track surface of line; h - Depth;

[0068] 4 - First - stage steel bars; 41 - First - stage bottom steel bars; 42 - First - stage middle steel bars; 43 - First - stage top steel bars; 44 - First - stage distribution steel bars; 45 - First - stage tie bars; W - Continuous arrangement;

[0069] 5 - Second - stage steel bars; 51 - Second - stage bottom steel bars; 52 - Second - stage top steel bars; 53 - Second - stage distribution steel bars; 54 - Second - stage tie bars;

[0070] 6 - Steel bar coupler;

[0071] 7 - Drain well;

[0072] 81 - End wall of shield shaft; 82 - Shield tunnel portal; 83 - Side wall of shield shaft; I - Conventional bottom slab; Z - Ground elevation; X - Poor geology; Y - (Outside the foundation pit) water level elevation; J - Water pressure; MK - Comparison demarcation line. Detailed implementation manners

[0073] The following will clearly and completely describe the concept, specific structure and technical effects generated by the present invention in combination with the embodiments and the drawings, so as to fully understand the purpose, scheme and effects of the present invention. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The same reference numerals used in the drawings indicate the same or similar parts everywhere.

[0074] It should be noted that, unless otherwise specified, when a certain feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to another feature, or indirectly fixed or connected to another feature. In addition, the up, down, left, right, etc. descriptions used in the present invention are only relative to the mutual positional relationship of the components of the present invention in the drawings.

[0075] Refer to Figures 1 to 10 , a bottom slab structure 1 for reducing the excavation depth of the shield shaft foundation pit, including a first - stage bottom slab structure 11 and a second - stage bottom slab structure 12; the first - stage bottom slab structure 11 is arranged at the set depth of the shield shaft; the first - stage bottom slab structure 11 is arranged first, and the second - stage bottom slab structure 12 is arranged later; the first - stage bottom slab structure 11 is reserved with a groove 13, which can be used to support the operation of the shield machine; after the second - stage bottom slab structure 12 is arranged, it is filled in the groove 13.

[0076] Refer to Figures 1 to 10 , in an embodiment, the planar area A of the first - stage bottom slab structure 11 is determined by the working space 2 of the shield machine and the depth of the shield shaft;

[0077] The top view plane area of the groove 13 is the plane area B of the second-phase floor structure 12;

[0078] The plane area B of the second-phase floor structure 12 includes a first plane area B1 and a second plane area B2, and the first plane area B1 is adjacent to the second plane area B2;

[0079] The thickness T1 of the second-phase floor structure 12 is determined by the outer diameter R1 of the shield machine working space and the outer diameter R2 of the shield segment;

[0080] Among them, the shield machine working space 2 and the shield segment 3 are both circular structures, having a common center C and a common center line K.

[0081] Refer to Figures 1 to 10 , in one embodiment, the first working width D1 of the shield machine and the working section length L1 of the shield machine constitute the shield machine working plane area E; preferably, the shield machine working plane area E is a plane rectangular area;

[0082] The first plane area B1 is greater than or equal to the shield machine working plane area E;

[0083] The maximum width D2 of the shield machine reaction frame and the maximum length L2 of the shield machine reaction frame constitute the shield machine reaction frame plane area F; preferably, the shield machine reaction frame plane area F is a plane rectangular area;

[0084] The second plane area B2 is greater than or equal to the shield machine reaction frame plane area F.

[0085] Refer to Figures 1 to 10, in one embodiment, the first working width D1 of the shield machine is determined by the chord length G where the outer diameter R1 of the working space of the shield machine intersects the plate surface of the second-stage floor structure 12. Preferably, the outer diameter R1 of the working space of the shield machine is 5000 mm, and the chord length G where the outer diameter R1 of the working space of the shield machine intersects the plate surface of the second-stage floor structure 12 is 5400 mm. Each end of this chord length G is extended by 700 mm (to reserve the installation space for the shield machine), and finally the first working width D1 of the shield machine is obtained as 6800 mm; and the working section length L1 of the shield machine is 13000 mm; then the "width × length" of the working plane area E of the shield machine is "6800 mm × 13000 mm". Preferably, the first plane area B1 is "slightly larger than" the working plane area E of the shield machine. On both sides in the width direction of the first plane area B1, it is at least 100 mm larger than the first working width of the shield machine (the margin design of the present invention), that is, the width of the first plane area B1 is at least 7000 mm; on both sides in the length direction of the first plane area B1, it is at least 100 mm larger than the working section length of the shield machine (the margin design of the present invention), that is, the length of the first plane area B1 is at least 13200 mm.

[0086] Refer to Figures 1 to 10 , in one embodiment, the reaction frame plane area F of the shield machine is a plane rectangular area. The maximum width D2 of the reaction frame of the shield machine is 10800 mm, and the maximum length L2 of the reaction frame of the shield machine is 2400 mm. Preferably, the second plane area B2 is "slightly larger than" the reaction frame plane area F of the shield machine. On both sides in the width direction of the second plane area B2, it is at least 100 mm larger than the width of the reaction frame plane area of the shield machine, that is, the width of the second plane area B2 is at least 11000 mm; on both sides in the length direction of the second plane area B2, it is at least 100 mm larger than the length of the reaction frame plane area of the shield machine, that is, the length of the second plane area B2 is at least 2600 mm.

[0087] Refer to Figures 1 to 10 , in one embodiment, the elevation of the first-stage floor structure 11 includes the first-stage top elevation M1 and the first-stage bottom elevation M2;

[0088] The elevation of the second-stage floor structure 12 includes the second-stage top elevation N1 and the second-stage bottom elevation N2;

[0089] The first-stage top elevation M1 is the same as the second-stage top elevation N1;

[0090] Among them, the elevation M1 of the top surface of the first phase and the elevation N1 of the top surface of the second phase are determined by the bottom elevation P1 of the shield segment and are not higher than the bottom elevation P1 of the shield segment. Among them, the outer diameter R2 of the shield segment is determined according to the clearance limit of the train. Preferably, the outer diameter R2 of the shield segment is 4250 mm. The bottom elevation P1 of the shield segment is determined by the elevation P2 of the track surface of the line. Among them, the elevation P2 of the track surface of the line is determined according to the line design and is the absolute elevation (the "relative position" of each structure can be located with the elevation P2 of the track surface of the line as the absolute coordinate). Preferably, the center line of the line is consistent with the center line K of the working space 2 of the shield machine and the shield segment 3.

[0091] The bottom elevation M2 of the first phase is determined by the thickness T2 of the bottom slab structure 11 of the first phase on the basis that the elevation M1 of the top surface of the first phase has been determined. The thickness T2 of the bottom slab structure 11 of the first phase is determined by the working space 2 of the shield machine and the depth H of the shield shaft. Preferably, the outer diameter R1 of the working space of the shield machine is 5000 mm, and the depth H of the shield shaft is 38000 mm. Through (numerical) calculation, the thickness T2 of the bottom slab structure 11 of the first phase is obtained as 1500 mm.

[0092] The bottom elevation N2 of the second phase is determined by the bottom elevation P3 of the working space of the shield machine. Among them, the outer diameter R1 of the working space of the shield machine is greater than the outer diameter R2 of the shield segment. The bottom elevation P3 of the working space of the shield machine is determined by the elevation P2 of the track surface of the line (with the elevation P2 of the track surface of the line and the outer diameter R1 of the working space of the shield machine, the bottom elevation P3 of the working space of the shield machine can be located).

[0093] Refer to Figures 1 to 10 , in an embodiment, the elevation M1 of the top surface of the first phase and the elevation N1 of the top surface of the second phase are both consistent with the bottom elevation P1 of the shield segment. Preferably, the plate surfaces of the bottom slab structure 11 of the first phase and the bottom slab structure 12 of the second phase are both tangent to the lowest point of the shield segment 3.

[0094] The bottom elevation N2 of the second phase is consistent with the bottom elevation P3 of the working space of the shield machine. Preferably, the bottom surface of the bottom slab structure 12 of the second phase is tangent to the lowest point of the working space 2 of the shield machine. Preferably, the bottom elevation N2 of the second phase should not be higher than the bottom elevation P3 of the working space of the shield machine and should not be lower than the bottom elevation M2 of the first phase.

[0095] The difference (taking the absolute value) between the elevation N1 of the top surface of the second stage and the elevation N2 of the bottom surface of the second stage is the thickness T1 of the bottom slab structure 12 of the second stage, that is, the depth H1 of the groove 13. At the same time, the difference (taking the absolute value) between the outer diameter R1 of the working space of the shield machine and the outer diameter R2 of the shield segment is consistent with the thickness T1 of the bottom slab structure 12 of the second stage. Among them, preferably, the outer diameter R1 of the working space of the shield machine is 5000 mm, the outer diameter R2 of the shield segment is 4250 mm, then the thickness T1 of the bottom slab structure 12 of the second stage is 750 mm.

[0096] Refer to Figures 1 to 10 , in one embodiment, the present invention controls the elevation M1 of the top surface of the first stage and the elevation N1 of the top surface of the second stage with the bottom elevation P1 of the shield segment, and controls the bottom elevation N2 of the second stage with the bottom elevation P3 of the working space of the shield machine. Compared with the conventional bottom slab 1 cast integrally at one time, the present invention can reduce the excavation depth of the foundation pit by a maximum of: "the difference (taking the absolute value) between the bottom elevation P3 of the working space of the shield machine and the bottom elevation P1 of the shield segment", that is, "the difference (taking the absolute value) between the outer diameter R1 of the working space of the shield machine and the outer diameter R2 of the shield segment". If the outer diameter R1 of the working space of the shield machine is 5000 mm, the outer diameter R2 of the shield segment is 4250 mm, and the thickness T1 of the bottom slab structure 12 of the second stage is 750 mm, the present invention can reduce the excavation depth h of the foundation pit by a maximum of 750 mm.

[0097] In one embodiment, a bottom slab structure 1 for reducing the excavation depth of the shield well foundation pit of the present invention is applied to the foundation pit at the "starting end" of the shield well. Then, the outer diameter R1 of the working space of the shield machine is the outer diameter of the starting working space of the shield machine, and the working section length L1 of the shield machine is the starting section length of the shield machine. In another embodiment, a bottom slab structure 1 for reducing the excavation depth of the shield well foundation pit of the present invention is applied to the foundation pit at the "receiving end" of the shield well. Then, the outer diameter R1 of the working space of the shield machine is the outer diameter of the receiving working space of the shield machine, and the working section length L1 of the shield machine is the receiving section length of the shield machine.

[0098] Refer to Figures 1 to 10 , in one embodiment, a number of first-stage steel bars 4 are arranged in the first-stage bottom slab structure 11; the first-stage steel bars 4 include first-stage bottom bars 41, first-stage middle steel bars 42, and first-stage top bars 43; the first-stage bottom slab structure 11 is provided with the first-stage bottom bars 41, the first-stage middle steel bars 42, and the first-stage top bars 43 from top to bottom; among them, the names of "bottom bars" and "top bars" are distinguished according to the stress conditions of the structure. The steel bars in the lower position are called "top bars", and the steel bars in the upper position are called "bottom bars";

[0099] A number of second-stage steel bars 5 are arranged in the second-stage floor slab structure 12; the second-stage steel bars 5 include second-stage bottom bars 51 and second-stage top bars 52; the second-stage bottom bars 51 and the second-stage top bars 52 are respectively arranged in the second-stage floor slab structure 12 from top to bottom; among them, the names of "bottom bars" and "top bars" are distinguished according to the structural stress conditions. The steel bars in the bottom position are called "top bars", and the steel bars in the upper position are called "bottom bars".

[0100] Among them, the second-stage top bars 52 are connected to the first-stage middle bars 42 through a steel bar coupler 6;

[0101] The second-stage bottom bars 51 are connected to the first-stage bottom bars 41 through a steel bar coupler 6.

[0102] Refer to Figures 1 to 10 , preferably, there are multiple first-stage middle bars 42, and at least one of the first-stage middle bars 42 is continuously arranged along the width direction of the first-stage floor slab structure 11 (not in the "disconnected - connected" mode) (refer to the symbol W shown in Figure 4 and Figure 5 ).

[0103] Refer to Figures 1 to 10 , in an embodiment, the first-stage steel bars 4 further include first-stage distribution bars 44 and first-stage tie bars 45; the first-stage distribution bars 44 and the first-stage tie bars 45 are evenly arranged in the first-stage floor slab structure 11.

[0104] Refer to Figures 1 to 10 , in an embodiment, the second-stage steel bars 5 further include second-stage distribution bars 53 and second-stage tie bars 54; the second-stage distribution bars 53 and the second-stage tie bars 54 are evenly arranged in the second-stage floor slab structure 12.

[0105] Refer to Figures 1 to 10 , in an embodiment, a number of drain wells 7 are arranged in the first-stage floor slab structure 11, which are used to unload the buoyancy force of the water below the first-stage floor slab structure 11 during construction to reduce the influence of water pressure on the weak positions (such as the position of the groove 13) of the first-stage floor slab structure 11.

[0106] Refer to Figures 1 to 10 , in an embodiment, a fine aggregate concrete protective layer, a waterproof coiled material and a concrete cushion are provided under the first-stage floor slab structure 11; the concrete cushion, the waterproof coiled material and the fine aggregate concrete protective layer are sequentially arranged under the first-stage floor slab structure 11 from bottom to top. Preferably, the concrete cushion is a 150 mm thick C20 concrete cushion; the waterproof coiled material is a 1.5 mm thick PVC waterproof coiled material; the fine aggregate concrete protective layer is a 50 mm thick fine aggregate concrete protective layer.

[0107] In one embodiment, the end wall 81 of the shield well, the shield portal 82, and the side wall 83 of the shield well are as Figure 7 shown. Specifically, the end wall 81 of the shield well, the shield portal 82, and the side wall 83 of the shield well can be referred to the prior art and will not be elaborated here.

[0108] Referring to Figure 10 , the conventional bottom slab I is cast integrally at one time, which fails to reduce the excavation depth of the shield well foundation pit. When the excavation depth of the shield well foundation pit is not reduced, if there are unfavorable geological conditions X such as "karst caves, fissures or fault zones" at the bottom slab position, when the foundation pit is excavated to the elevation of the bottom surface of the bottom slab, under the action of water pressure J of the unfavorable geological condition X, there will be risks of water gushing and sand gushing at the foundation base, and even risks of foundation pit collapse. However, if the newly designed bottom slab structure 1 of the present invention is adopted, the excavation depth of the shield well foundation pit can be reduced. The excavation depth of the foundation pit is reduced by a set depth compared with the past. For example, if the depth h is reduced (where h = T1 = H1 = (R1 - R2)), then when the shield tunneling operation is realized, the unfavorable geological conditions X such as "karst caves, fissures or fault zones" are below the excavation depth of the foundation pit, and the present invention effectively reduces the risks of water gushing and sand gushing in the foundation pit.

[0109] In a construction project, the conventional bottom slab I is cast integrally at one time, which fails to reduce the excavation depth of the shield well foundation pit. When the excavation depth of the shield well foundation pit is not reduced, the foundation pit is over-excavated and encounters unfavorable geological condition X. Under the action of water pressure J of the unfavorable geological condition X, there is a sudden risk of water gushing. Eventually, the foundation pit is flooded in a large area, which brings difficulties to the construction, causes damage to mechanical equipment, and damages the foundation pit structure, bringing construction losses and economic losses to the project and having relatively large safety risks. After the present invention appears, the construction risks brought by over-deep excavation of the foundation pit are significantly reduced.

[0110] Another object of the present invention is to provide a construction method for a bottom slab structure to scientifically guide the construction of the new bottom slab structure, so as to reduce the construction difficulty, improve the construction safety and construction efficiency.

[0111] Referring to Figures 1 to 10 , a construction method for a bottom slab structure, which is used for constructing the bottom slab structure 1 that reduces the excavation depth of the shield well foundation pit, is characterized by including the following steps:

[0112] S1. Determine the dimensions of the first-stage floor structure 11 (such as the planar area A (length × width), thickness T2), determine the dimensions of the second-stage floor structure 12 (such as the planar area B (length × width), thickness T1), calculate the steel reinforcement required for the first-stage floor structure 11, and calculate the steel reinforcement required for the second-stage floor structure 12 according to the outer diameter R2 of the shield segment (such as R2 = 4250 mm), the dimensions of the shield machine (such as the diameter of the shield machine is 8800 mm), the outer diameter R1 of the working space of the shield machine (such as R1 = 5000 mm), the dimensions of the reaction frame of the shield machine, the depth H of the shield shaft (such as H = 38000 mm), and the engineering geology (such as the geology of "karst cave development");

[0113] S2. Construct the cushion and waterproof structure Q under the first-stage floor structure 11; specifically, from bottom to top, first construct a 150-mm-thick C20 concrete cushion, then construct a 1.5-mm-thick PVC waterproof coiled material, and finally construct a 50-mm-thick fine aggregate concrete protective layer;

[0114] S3. Bind the first-stage steel bars 4 required for the first-stage floor structure 11; specifically, the first-stage top steel bars 43, the first-stage middle steel bars 42, and the first-stage bottom steel bars 41 can be bound in sequence from bottom to top;

[0115] S4. Reserve the steel bar couplers 6 for connecting the first-stage middle steel bars 42 of the first-stage floor structure with the second-stage top steel bars 52 of the second-stage floor structure; reserve the steel bar couplers 6 for connecting the first-stage bottom steel bars 41 of the first-stage floor structure with the second-stage bottom steel bars 51 of the second-stage floor structure; reserve the drainage well 7 on the first-stage floor structure;

[0116] S5. Pour the concrete required for the first-stage floor structure 11 and form the groove 13; among them, the concrete adopts C35 concrete with an impermeability grade of P12;

[0117] S6. After the concrete of the first-stage floor structure 11 reaches the strength, place the shield machine on the groove 13 and carry out shield work;

[0118] S7. After completing the shield work (note: such as the shield machine on the groove 13 at the starting end has shielded into the tunnel, and the second-stage floor structure 12 is needed for subsequent installation of the shield segment 3), chisel the groove wall of the groove 13 (the groove wall includes the groove bottom), that is, chisel the concrete at the interface between the first-stage floor structure 11 and the second-stage floor structure 12. Then, bind the second-stage top steel bars 52 and the second-stage bottom steel bars 51 of the second-stage floor structure 12, and screw the second-stage top steel bars 52 and the second-stage bottom steel bars 51 into the reserved steel bar couplers 6 respectively, so that the second-stage top steel bars 52 are mechanically connected to the first-stage middle steel bars 42 and the second-stage bottom steel bars 51 are mechanically connected to the first-stage bottom steel bars 41;

[0119] S8. After the connection of the secondary steel bars 5 of the secondary floor slab structure 12 is completed, pour the concrete required for the secondary floor slab structure 12. Among them, the concrete used for the secondary floor slab structure 12 is the same grade and impermeability grade as that of the primary floor slab structure 11, that is, C35 concrete with an impermeability grade of P12. At the same time, the concrete used for the secondary floor slab structure 12 should have the characteristic of "micro-expansion" to better realize the interface connection between the secondary floor slab structure 12 and the primary floor slab structure 11. After the secondary floor slab structure 12 is poured and formed, its top view is in a "T" shape.

[0120] S9. After the construction is completed, block the drainage well 7.

[0121] For a floor slab structure 1 for reducing the excavation depth of a shield tunnel shaft foundation pit of the present invention, on the premise that the elevation P2 of the track surface of the line is determined, the bottom elevation N2 of the secondary floor is controlled by the bottom elevation P3 of the working space of the shield machine, and the top elevations M1 of the primary floor and N1 of the secondary floor are controlled by the bottom elevation P1 of the shield segment. Among them, the primary floor slab structure 11 and the secondary floor slab structure 12 are poured in two times successively. Compared with the conventional floor slab I which is poured integrally at one time, the present invention can minimize the excavation depth of the foundation pit at the starting end or receiving end of the shield tunnel shaft (note: understand in combination with Figure 10 ). The reduction of the excavation depth of the foundation pit at the starting end or receiving end of the shield tunnel shaft can greatly reduce the risks of base water gushing and sand gushing, reduce the construction risks of the project itself and the construction impact on surrounding buildings. At the same time, since the excavation depth of the foundation pit at the starting end or receiving end of the shield tunnel shaft is reduced, the length of the retaining structure diaphragm wall, the length of the structural side wall and the thickness of the concrete backfill in the sinking section of the shield tunnel shaft can be reduced, reducing the construction cost and improving the construction safety. The present invention has remarkable social and economic benefits. By adopting the newly designed floor slab structure and construction method of the present invention, the construction difficulty is reduced, the construction risks are effectively avoided, and the smooth progress of the shield project is ensured. According to statistics, the appearance of the present invention can reduce the "expenditure on the materials of the structure itself" and the "extra expenditure required to solve the construction risks" by nearly one million yuan.

[0122] For other contents of the floor slab structure and construction method for reducing the excavation depth of a shield tunnel shaft foundation pit of the present invention, refer to the prior art and will not be elaborated here.

[0123] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Therefore, any modification, equivalent change and decoration made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A bottom plate structure for reducing the excavation depth of a shield shaft foundation pit, characterized in that: It includes a first-phase bottom plate structure and a second-phase bottom plate structure; the first-phase bottom plate structure is arranged at a set depth of the shield shaft; the first-phase bottom plate structure is arranged first, and the second-phase bottom plate structure is arranged later; the first-phase bottom plate structure is reserved with a groove that can be used to support the work of the shield machine; after the second-phase bottom plate structure is arranged, it is filled in the groove.

2. A bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit according to claim 1, characterized in that: The plane area of ​​the first-stage bottom plate structure is determined by the working space of the shield machine and the depth of the shield shaft; The top view plane area of ​​the groove is the plane area of ​​the second-stage bottom plate structure; The plane area of ​​the second-phase bottom plate structure includes a first plane area and a second plane area, and the first plane area is adjacent to the second plane area; The thickness of the second-stage bottom plate structure is determined by the outer diameter of the shield machine working space and the outer diameter of the shield segment; Among them, the shield machine working space and shield segments have a common center and a common center line.

3. A bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit according to claim 2, characterized in that: The first working width of the shield machine and the working section length of the shield machine constitute the working plane area of ​​the shield machine; The first plane area is greater than or equal to the working plane area of ​​the shield machine; The maximum width of the shield machine reaction frame and the maximum length of the shield machine reaction frame constitute the plane area of ​​the shield machine reaction frame; The second plane area is greater than or equal to the plane area of ​​the shield machine reaction frame.

4. A bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit according to claim 3, characterized in that: The first working width of the shield machine is determined by the chord length of the intersection between the outer diameter of the shield machine's working space and the plate surface of the second-phase bottom plate structure.

5. The bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit according to claim 2, characterized in that: The elevation of the first-stage base structure includes the first-stage top elevation and the first-stage bottom elevation; The elevation of the second-phase base plate structure includes the second-phase top surface elevation and the second-phase bottom surface elevation; The elevation of the top surface of the first phase is consistent with the elevation of the top surface of the second phase; The elevation of the first-stage top surface and the elevation of the second-stage top surface are determined by the bottom elevation of the shield segment and are not higher than the bottom elevation of the shield segment; the outer diameter of the shield segment is determined according to the limit of the train; the bottom elevation of the shield segment is determined by the track surface elevation; the track surface elevation is determined according to the line design and is an absolute elevation; The elevation of the first-stage bottom surface is determined by the thickness of the first-stage bottom plate structure on the basis that the elevation of the first-stage top surface has been determined; the thickness of the first-stage bottom plate structure is determined by the working space of the shield machine and the depth of the shield shaft; The bottom elevation of the second phase is determined by the bottom elevation of the shield machine's working space; wherein, the outer diameter of the shield machine's working space is greater than the outer diameter of the shield segment; the bottom elevation of the shield machine's working space is determined by the track surface elevation.

6. A bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit according to claim 5, characterized in that: The first phase top surface elevation and the second phase top surface elevation are both consistent with the shield segment bottom elevation; The bottom elevation of the second phase is consistent with the bottom elevation of the shield machine working space; The difference between the second phase top surface elevation and the second phase bottom surface elevation is the thickness of the second phase bottom plate structure, that is, the depth of the groove; at the same time, the difference between the outer diameter of the shield machine working space and the outer diameter of the shield segment is consistent with the thickness of the second phase bottom plate structure.

7. The bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit according to claim 1, characterized in that: A plurality of first-stage steel bars are arranged in the first-stage bottom plate structure; the first-stage steel bars include first-stage bottom bars, first-stage middle steel bars, and first-stage surface bars; the first-stage bottom plate structure is respectively provided with the first-stage bottom bars, the first-stage middle steel bars, and the first-stage surface bars from top to bottom; A plurality of second-phase steel bars are arranged in the second-phase bottom plate structure; the second-phase steel bars include second-phase bottom bars and second-phase surface bars; the second-phase bottom plate structure is respectively provided with the second-phase bottom bars and the second-phase surface bars from top to bottom; Wherein, the second-stage surface steel bars are connected to the first-stage middle steel bars through a steel bar connector; The second-stage bottom reinforcement is connected to the first-stage bottom reinforcement via a reinforcement connector.

8. The bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit according to claim 1, characterized in that: A plurality of drainage wells are arranged in the first-phase bottom plate structure.

9. The bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit according to claim 1, characterized in that: A fine stone concrete protective layer, a waterproof membrane and a concrete cushion layer are arranged under the first-phase bottom plate structure; the concrete cushion layer, the waterproof membrane and the fine stone concrete protective layer are arranged under the first-phase bottom plate structure in sequence from bottom to top.

10. A method for constructing a bottom plate structure, which is used for constructing a bottom plate structure for reducing the excavation depth of a shield tunnel foundation pit as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Determine the size of the first-phase floor structure and the second-phase floor structure according to the outer diameter of the shield segment, the outer diameter of the shield machine working space, the size of the shield machine reaction frame, the depth of the shield shaft and the engineering geology, and calculate the reinforcement required for the first-phase floor structure and the reinforcement required for the second-phase floor structure; S2. construct the cushion layer and waterproof structure under the first-phase base structure; S3, tying the first-stage steel bars required for the first-stage bottom plate structure; S4, reserve a steel bar connector for connecting the first-stage middle steel bars of the first-stage bottom plate structure with the second-stage surface steel bars of the second-stage bottom plate structure; reserve a steel bar connector for connecting the first-stage bottom bars of the first-stage bottom plate structure with the second-stage bottom bars of the second-stage bottom plate structure; reserve a drainage well on the first-stage bottom plate structure; S5, pouring the concrete required for the first-stage base plate structure and forming the groove; S6. After the concrete of the first-stage bottom plate structure reaches the required strength, the shield machine is placed on the groove to perform shield tunneling work; S7. After the shield work is completed, the groove wall of the groove is roughened, that is, the concrete at the interface between the first-phase bottom plate structure and the second-phase bottom plate structure is roughened, and then the second-phase surface reinforcement and the second-phase bottom reinforcement of the second-phase bottom plate structure are tied, and the second-phase surface reinforcement and the second-phase bottom reinforcement are respectively screwed into the reserved steel bar connectors, so that the second-phase surface reinforcement is mechanically connected with the first-phase middle reinforcement, and the second-phase bottom reinforcement is mechanically connected with the first-phase bottom reinforcement; S8. After the second-phase steel bar connection of the second-phase bottom plate structure is completed, concrete required for the second-phase bottom plate structure is poured; S9. After the construction is completed, seal the drainage well.

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