Cantilever type side wall self-stabilizing system applied to deep foundation pit support and construction method of cantilever type side wall self-stabilizing system

Abstract

The invention discloses a cantilever type side wall self-stabilizing system applied to deep foundation pit supporting and a construction method thereof.The cantilever type side wall self-stabilizing system applied to deep foundation pit supporting comprises two waterproof curtains, a supporting pile and a concrete slope protection, a plurality of soil nails are arranged in the concrete slope protection, a top beam is arranged at the top of the supporting pile, a wet-lean concrete layer is arranged on the inner side of the supporting pile, and the cantilever type side wall self-stabilizing system further comprises an underpass channel box culvert; a plurality of columns of additional supporting steel bars arranged at intervals are arranged in structural steel bars of the underpass channel box culvert, the underpass channel box culvert comprises an underpass channel bottom plate, an underpass channel top plate and two underpass channel side walls, one ends of the additional supporting steel bars are inserted into the underpass channel side walls, and the other ends of the additional supporting steel bars penetrate through vertical side wall sections of the underpass channel bottom plate. The side wall panel is arranged on the transverse bottom wall section of the underpass channel bottom plate and is bent and inserted into the transverse bottom wall section of the underpass channel bottom plate so as to ensure the bending bearing capacity of the underpass channel bottom plate, so that a switching support structure in the prior art can be replaced, the pressure intensity of the side wall panel is small, the rigidity and the shock resistance of the whole structure are improved, and the construction period can be obviously shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit support, and in particular to a cantilever side wall self-stabilizing system used for deep foundation pit support and a construction method thereof, which is particularly suitable for foundation pit support operations with complex geology around the foundation pit, many underground pipelines, and an inner support depth of no more than 8 meters. Background Art

[0002] The foundation pit project is to excavate an underground space from the ground, with vertical retaining structures set up around it, and generally an inserted plate (or pile) wall structure of a certain depth is set under the base of the excavation surface.

[0003] At present, the foundation pit support often adopts the inverted support structure to reduce the deformation of the surrounding structure and control the bending moment of the wall. However, since the inverted support directly supports the inner surface of the side wall panel, the force-bearing area of ​​the side wall panel is very small, which can easily lead to deformation and damage of the side wall panel.

[0004] In addition, each section of the box culvert structure is generally equipped with 9 switch supports, and the switch supports of each section need to be repeatedly installed and removed, which is very time-consuming and labor-intensive. Summary of the invention

[0005] To this end, in order to solve the above-mentioned problem, the present invention provides a cantilever side wall self-stabilizing system and a construction method for deep foundation pit support, which can replace the existing inverted support structure, and the pressure of the side wall panel is relatively small, and the stiffness and seismic resistance of the overall structure are improved, and the construction period can be significantly shortened.

[0006] To achieve the above purpose, the technical solution provided by the present invention is as follows:

[0007] The present invention provides a cantilever side wall self-stabilizing system used for deep foundation pit support, comprising two water-stop curtains, supporting piles arranged between the water-stop curtains, and concrete slope protection arranged between the water-stop curtains and the supporting piles, wherein a plurality of soil nails are arranged in the concrete slope protection, a cap beam is arranged on the top of the supporting pile, and a wet-lean concrete layer is arranged on the inner side of the supporting pile, and further comprising an underpass box culvert arranged between the two wet-lean concrete layers; a plurality of rows of additional supporting steel bars arranged at intervals are arranged in the structural steel bars of the underpass box culvert, and the system comprises an underpass bottom plate, an underpass top plate, and two underpass side walls located between the underpass bottom plate and the underpass top plate, wherein one end of the additional supporting steel bar is inserted into the underpass side wall, and the other end thereof passes through the vertical side wall section of the underpass bottom plate, and is bent and inserted into the transverse bottom wall section of the underpass bottom plate, so as to ensure the bending bearing capacity of the underpass bottom plate.

[0008] Furthermore, at least 4 additional supporting steel bars are added per linear meter in the side wall of the underpass box culvert.

[0009] Furthermore, the diameter of the additional supporting steel bars is 28 mm, and the spacing between them is 25 mm.

[0010] Furthermore, the additional supporting steel bars include a vertical section and an elbow section, one end of the vertical section is inserted into the side wall of the underpass, and the other end of the vertical section is inserted into the vertical side wall section of the bottom plate of the underpass; the elbow section is inserted into the transverse bottom wall section of the bottom plate of the underpass.

[0011] Furthermore, the lengths of the vertical section and the elbow section are configured to be equal.

[0012] The present invention provides a construction method of the cantilever side wall self-stabilizing system used for deep foundation pit support, comprising the following steps: S1, leveling the construction site, then constructing a water-stop curtain, performing slope excavation between two water-stop curtains, and then constructing at least three soil nails to form slope support, and then spraying concrete slope protection and driving supporting piles in sequence; S2, after draining the groundwater in the construction site, excavating the soil at the top of the supporting piles, and constructing a crown beam on the top of the supporting piles, and constructing a reinforced concrete support between the two crown beams; after the concrete strength of the crown beam and the reinforced concrete support meets the design requirements, continue to excavate the lower earthwork, and erect steel purlins and steel supports to form a deep foundation pit; S3, respectively arrange the structural steel bars of the side walls and the bottom plate of the underpass on both sides and the bottom of the deep foundation pit according to the pre-designed arrangement, and arrange them at a distance from the supporting piles, then arrange additional supporting steel bars, and then cast the bottom plate of the underpass; after the concrete strength of the bottom plate of the underpass meets the design requirements, After the strength of the wet lean concrete in S3 meets the design requirements, the steel support and the steel purlin are removed in sequence, and then the side wall of the underpass is cast; after the concrete strength of the side wall of the underpass meets the design requirements, the wet lean concrete is backfilled in the fat trough between the supporting pile and the side wall of the underpass; S5, after the strength of the wet lean concrete in S4 meets the design requirements, the reinforced concrete support is removed, and then a disc-type full-span scaffolding is erected, and then the top plate of the underpass is constructed above the disc-type full-span scaffolding; after the concrete strength of the bottom plate of the underpass meets the design requirements, the wet lean concrete is backfilled in the fat trough between the supporting pile and the top plate of the underpass; S6, after the strength of the wet lean concrete in S5 meets the design requirements, the disc-type full-span scaffolding is towed as a whole to the working surface of the next section by the towing moving device, and S2 to S5 are repeated until the underpass box culvert is obtained.

[0013] Furthermore, at least 4 additional supporting steel bars are added per linear meter in the side wall of the underpass box culvert.

[0014] Furthermore, the diameter of the additional supporting steel bars is 28 mm, and the spacing between them is 25 mm.

[0015] Furthermore, in S2, the over-excavation depth during the erection of each support does not exceed 0.5m.

[0016] Furthermore, it also includes S7; in S7, the earth is backfilled and compacted in layers above the top plate of the underpass.

[0017] The technical solution provided by the present invention has the following beneficial effects:

[0018] The underpass box culvert of the present invention is a beam-column-free structure, and compared with the inverted support structure of the prior art, the side wall panel of the present invention is subjected to less pressure under the same soil pressure, and the integrity and safety of its side wall structure are higher. Therefore, the present invention can not only effectively replace the inverted support structure, but also improve the rigidity and seismic resistance of the overall structure, strengthen the crack resistance of concrete and improve the safety of redundant structures, thereby ensuring that the underpass is in a safe use state for a long time.

[0019] The present invention does not require the installation or removal of the inverted support structure of the prior art. Therefore, the present invention can also significantly shorten the construction period, effectively save construction costs, and improve construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shown is a schematic diagram of the underpass box culvert in the embodiment;

[0021] Figure 2 Shown is a reinforcement diagram of the underpass box culvert in the embodiment;

[0022] Figure 3 Shown Figure 2 Sectional view of AA in the middle;

[0023] Figure 4 The figure shows a state schematic diagram of step S1 of the construction method in the embodiment;

[0024] Figure 5 The figure shows a state schematic diagram of step S2 of the construction method in the embodiment;

[0025] Figure 6 The figure shows a state schematic diagram of step S3 of the construction method in the embodiment;

[0026] Figure 7 The figure shows a state schematic diagram of step S4 of the construction method in the embodiment;

[0027] Figure 8 The figure shows a state diagram of step S5 of the construction method in the embodiment;

[0028] Fig. 9 It is a state schematic diagram of step S6 of the construction method in the embodiment. DETAILED DESCRIPTION

[0029] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0030] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.

[0031] Reference Figures 1 to 9 As shown, this embodiment provides a cantilever side wall self-stabilizing system for deep foundation pit support (hereinafter referred to as the cantilever side wall self-stabilizing system), including: Fig. 9 The two water-stop curtains 2 shown, the supporting piles 1 arranged between the water-stop curtains 2, the concrete slope protection 3 arranged between the water-stop curtains 2 and the supporting piles 1, three soil nails 31 are respectively arranged in the concrete slope protection 3, the top of the supporting piles 1 is arranged with a cap beam 5, and the inner side of the supporting piles 1 is arranged with a wet-lean concrete layer 7.

[0032] The cantilever side wall self-stabilizing system of this embodiment also includes a device arranged between two wet lean concrete layers 7 as follows Figure 1 The underpass box culvert 8 shown in the figure has a plurality of rows of additional supporting steel bars 9 arranged at intervals within the structural steel bars of the underpass box culvert 8, and includes an underpass bottom plate 81, an underpass top plate 83 and two underpass side walls 82 located between the underpass bottom plate 81 and the underpass top plate 83.

[0033] One end of the additional supporting steel bar 9 is inserted into the side wall 82 of the down passage, and the other end thereof passes through the vertical side wall section 811 of the down passage bottom plate 81, and is bent and inserted into the transverse bottom wall section 812 of the down passage bottom plate 81 to ensure the bending bearing capacity of the down passage bottom plate 81.

[0034] In this embodiment, 4 additional supporting steel bars 9 are added per linear meter in the side wall of the underpass box culvert 8, and the diameter of the additional supporting steel bars 9 is 28 mm, and the spacing between them is 25 mm.

[0035] More specifically, Figure 1 , Figure 2 and Figure 3As shown, the additional supporting steel bar 9 includes a vertical section 91 and an elbow section 92. The upper end of the vertical section 91 is inserted into the side wall 82 of the down-passing channel, the lower end of the vertical section 91 is inserted into the vertical side wall section 811 that penetrates the bottom plate 81 of the down-passing channel, and the elbow section 92 is transversely inserted into the transverse bottom wall section 812 of the bottom plate 81 of the down-passing channel. At this time, the vertical section 91 and the elbow section 92 cross each other at 90 degrees, and the lengths of the vertical section 91 and the elbow section 92 are equally configured.

[0036] In specific implementation, the following construction method is used to construct the cantilever side wall self-stabilizing system of this embodiment, and includes the following specific steps:

[0037] like Figure 4 As shown, step S1, level the construction site with a site elevation of 12.0m, then construct a water-stop curtain 2, and then carry out slope excavation between the two water-stop curtains 2, that is, carry out slope excavation on the geology (such as miscellaneous fill, silty clay, etc.) in the range of 12.0m to 6.1m, and then excavate the earth to an elevation of 7.0m, then set the top guardrail 12, and then construct at least three soil nails 31 to form a slope support, and then spray concrete slope protection 3 and drive support piles 1 in sequence.

[0038] like Figure 5 As shown, step S2, at this time the bottom elevation of the foundation pit is 0.5m, the groundwater in the construction site is pumped out, and then the soil on the top of the supporting pile 1 is excavated, and the crown beam 5 is constructed on the top of the supporting pile 1, and then the reinforced concrete support 61 is constructed between the two crown beams 5, and the top elevation of the reinforced concrete support 61 is 7.0m; after the concrete strength of the crown beam 5 and the reinforced concrete support 61 meets the design requirements, continue to excavate the lower earthwork, and erect steel purlins 63 and steel supports 62, and the top elevation of the steel supports 62 is 3.5m, so as to form a deep foundation pit, and the over-excavation depth of each support during erection does not exceed 0.5m.

[0039] like Figure 6 As shown, in step S3, the structural steel bars of the side walls and the bottom plate of the underpass are respectively arranged on both sides and the bottom of the deep foundation pit according to the pre-design, and are arranged at a distance from the supporting piles 1, and then the additional supporting steel bars 9 are arranged in a binding manner, and then the bottom plate 81 of the underpass is cast. The bottom plate 81 of the underpass includes a vertical side wall section 811 and a horizontal bottom wall section 812, and is provided with a cushion layer and a waterproof layer. At this time, the vertical side wall section 811 is a part of the side wall structure, and the top elevation of the vertical side wall section 811 is 2.45m; after the concrete strength of the bottom plate 81 of the underpass meets the design requirements, the wet lean concrete is backfilled in the fertilizer trough between the supporting piles 1 and the bottom plate 81 of the underpass.

[0040] like Figure 7As shown, in step S4, after the strength of the wet lean concrete in step S3 meets the design requirements, the steel supports 62 and the steel purlins 63 are removed in sequence, and then the side walls 82 of the underpass are cast. At this time, the top elevation of the two side walls 82 of the underpass is 5.5m; after the concrete strength of the side walls 82 of the underpass meets the design requirements, the wet lean concrete is backfilled in the fertilizer trough between the support piles 1 and the side walls 82 of the underpass.

[0041] like Figure 8 As shown, in step S5, after the strength of the wet lean concrete in step S4 meets the design requirements, the reinforced concrete support 61 is removed, and then the disc-type full-floor scaffolding 11 is erected, and then the underpass top plate 83 is constructed above the disc-type full-floor scaffolding 11; after the concrete strength of the underpass bottom plate 81 meets the design requirements, the wet lean concrete is backfilled in the fertilizer trough between the supporting piles 1 and the underpass top plate 83.

[0042] like Fig. 9 As shown, step S6, after the wet lean concrete strength in step S5 meets the design requirements, the disc-type full-floor scaffolding 11 is pulled as a whole to the working surface of the next section through the traction and movement device of the utility model patent CN215564490U, and steps S2 to S5 are repeated until the entire underpass box culvert 8 at the construction site is completed.

[0043] Step S7, backfill and roll earthwork in layers above the top plate 83 of the underpass, that is, backfill and roll earthwork in layers from the top plate 83 of the underpass at an elevation of 8.9m to the field level elevation of 12.0m. Of course, a waterproof layer and a protective layer are also provided above the top plate 83 of the underpass.

[0044] When all the construction is completed, the side walls of the underpass box culvert 8 are subjected to earth pressure load, and the bottom thereof is subjected to uniformly distributed load (mainly from the deadweight of the structure and the load of the decoration surface layer). At this time, the bending moment at the connection between the side walls of the underpass box culvert 8 and its bottom is relatively large. Therefore, the elbow section 92 of the additional supporting steel bar 9 is extended to the transverse bottom wall section 812 of the underpass bottom plate 81 to serve as additional steel bars at the bottom of the underpass box culvert 8, and to increase the reinforcement ratio, thereby achieving the effect of increasing its bottom bending bearing capacity.

[0045] In addition, the bottom plate 81 of the underpass in this embodiment is 1.2m thick, the side wall 82 of the underpass is 3.8m high, the retaining wall is 5.0m high, and the back soil density of the retaining wall is 20KN / m 3, the static earth pressure coefficient is 1-sin30°, and then reinforcement calculations and multiple field data tests are carried out to determine that 4 additional supporting steel bars 9 are added per linear meter in the side wall of the underpass box culvert 8, the length of the vertical section 91 of the additional supporting steel bars 9 is 4.9m, the length of the elbow of the additional supporting steel bars 9 is 4.9m, and the material of the additional supporting steel bars 9 is HRB400 steel bars. This can ensure that the maximum crack width of the cantilever side wall self-stabilizing system of this embodiment is less than 0.2mm to meet the crack control requirements.

[0046] In summary, the underpass box culvert 8 of the present embodiment is a beam-column-free structure, and compared with the inverted support structure of the prior art, the side wall panels of the present embodiment are subjected to less pressure under the same soil pressure, and the integrity and safety of the side wall structure are higher. Therefore, the present embodiment can not only effectively replace the inverted support structure, but also improve the stiffness and seismic resistance of the overall structure, strengthen the crack resistance of the concrete and improve the safety of the redundant structure, thereby ensuring that the underpass is in a safe use state for a long time.

[0047] In addition, Table 1 shown below shows the construction days of the prior art switching support, and Table 2 shown below shows the construction days of the cantilever side wall self-stabilizing system of this embodiment.

[0048] Table 1: Construction days for the existing technology of the replacement support

[0049]

[0050] Table 2: Construction days of the cantilever side wall self-stabilizing system of this embodiment

[0051]

[0052] According to Table 1 and Table 2 above, it can be seen that the present embodiment does not require the installation or removal of the prior art switching support structure. Therefore, the present embodiment can also significantly shorten the construction period, effectively save construction costs, and improve construction efficiency.

[0053] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A cantilever side wall self-stabilizing system used for deep foundation pit support, comprising two water-stop curtains, support piles arranged between the water-stop curtains, and concrete slope protection arranged between the water-stop curtains and the support piles, wherein a plurality of soil nails are arranged in the concrete slope protection, a cap beam is arranged on the top of the support pile, and a wet-lean concrete layer is arranged on the inner side of the support pile, characterized in that: Also included is an underpass box culvert disposed between two wet lean concrete layers; The structural reinforcement of the underpass box culvert is provided with a plurality of rows of additional supporting reinforcements arranged at intervals, and includes an underpass bottom plate, an underpass top plate, and two underpass side walls located between the underpass bottom plate and the underpass top plate; one end of the additional supporting reinforcement is inserted into the underpass side wall, and the other end thereof passes through the vertical side wall section of the underpass bottom plate, and is bent and inserted into the transverse bottom wall section of the underpass bottom plate, so as to ensure the bending bearing capacity of the underpass bottom plate.

2. The cantilever side wall self-stabilizing system for deep foundation pit support according to claim 1 is characterized in that: At least 4 additional supporting steel bars are added per linear meter in the side wall of the underpass box culvert.

3. The cantilever side wall self-stabilizing system for deep foundation pit support according to claim 2 is characterized in that: The diameter of the additional supporting steel bars is 28 mm, and the spacing between them is 25 mm.

4. The cantilever side wall self-stabilizing system for deep foundation pit support according to any one of claims 1 to 3, characterized in that: The additional supporting steel bars include a vertical section and an elbow section, one end of the vertical section is inserted into the side wall of the underpass, and the other end of the vertical section is inserted into the vertical side wall section of the bottom plate of the underpass; the elbow section is inserted into the transverse bottom wall section of the bottom plate of the underpass.

5. The cantilever side wall self-stabilizing system for deep foundation pit support according to claim 4 is characterized in that: The lengths of the vertical section and the elbow section are configured to be equal.

6. A construction method for a cantilever side wall self-stabilizing system for deep foundation pit support according to any one of claims 1 to 5, characterized in that: The steps include: S1, level the construction site, then construct a water-stop curtain, excavate the slope between the two water-stop curtains, then construct at least three soil nails to form a slope support, and then spray concrete slope protection and drive support piles in sequence; S2: After draining the groundwater in the construction site, excavate the soil on the top of the supporting piles, construct a cap beam on the top of the supporting piles, and construct reinforced concrete supports between the two cap beams; after the concrete strength of the cap beam and the reinforced concrete support meets the design requirements, continue to excavate the lower earthwork, and erect steel purlins and steel supports to form a deep foundation pit; S3, the structural steel bars of the side walls and the bottom plate of the underpass are respectively arranged on both sides and the bottom of the deep foundation pit according to the pre-design, and are arranged at a distance from the supporting piles, and then additional supporting steel bars are arranged, and then the bottom plate of the underpass is cast; after the concrete strength of the bottom plate of the underpass meets the design requirements, the wet lean concrete is backfilled in the fertilizer groove between the supporting piles and the bottom plate of the underpass; S4, after the strength of the wet lean concrete in S3 meets the design requirements, the steel supports and steel purlins are removed in sequence, and then the side walls of the underpass are cast; after the concrete strength of the side walls of the underpass meets the design requirements, the wet lean concrete is backfilled in the fertilizer trough between the support piles and the side walls of the underpass; S5, after the strength of the wet lean concrete in S4 meets the design requirements, the reinforced concrete support is removed, and then a disc-type full-floor scaffold is erected, and then the top plate of the underpass is constructed above the disc-type full-floor scaffold; after the concrete strength of the bottom plate of the underpass meets the design requirements, the wet lean concrete is backfilled in the fertilizer trough between the support piles and the top plate of the underpass; S6: After the strength of the wet lean concrete in S5 meets the design requirements, the disc-type full-floor scaffolding is towed as a whole to the working surface of the next section by the towing moving device, and S2 to S5 are repeated until the underpass box culvert is obtained.

7. The construction method of the cantilever side wall self-stabilizing system used for deep foundation pit support according to claim 6 is characterized in that: At least 4 additional supporting steel bars are added per linear meter in the side wall of the underpass box culvert.

8. The construction method of the cantilever side wall self-stabilizing system used for deep foundation pit support according to claim 7 is characterized in that: The diameter of the additional supporting steel bars is 28 mm, and the spacing between them is 25 mm.

9. The construction method of the cantilever side wall self-stabilizing system used for deep foundation pit support according to claim 6 is characterized in that: In S2, the over-excavation depth during the erection of each support shall not exceed 0.5m.

10. The construction method of the cantilever side wall self-stabilizing system used for deep foundation pit support according to claim 6, characterized in that: It also includes S7; in S7, the rolled earth is backfilled in layers above the top plate of the underpass.

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