Support structure for deep foundation pit under ultra-wide pipeline and construction method for deep foundation pit under ultra-wide pipeline

Abstract

The present invention belongs to the technical field of urban rail transit engineering construction. Specifically, the present invention relates to a deep foundation pit support structure under an ultra-wide pipeline and a deep foundation pit construction method under an ultra-wide pipeline. The deep foundation pit support structure under an ultra-wide pipeline of the present invention includes retaining piles, a first additional retaining pile, a second additional retaining pile, a transverse support beam, a ground pre-grouting reinforced soil layer, a synchronous grouting reinforced soil layer, a reverse retaining wall, a grouting steel flower pipe, a waist beam, an inner support and a crown beam. The deep foundation pit construction method under an ultra-wide pipeline of the present invention mainly includes the construction of a double-row pile retaining structure, pre-grouting and synchronous grouting reinforcement, and the installation of a transverse support beam. The present invention can reduce construction risks, improve construction efficiency, and has good economic benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of urban rail transit engineering construction, and in particular, relates to a deep foundation pit support structure under an ultra-wide pipeline and a deep foundation pit construction method under an ultra-wide pipeline. Background Art

[0002] With the accelerated development of urban rail transit construction in my country, the spatial conflict between new underground stations and existing municipal facilities is becoming increasingly apparent. During the construction phase, municipal pipelines within the scope of open-cut stations are generally temporarily relocated, permanently relocated, or suspended for protection. When important pipelines such as military cables (military optical cables, electric cables) and high-voltage power corridors are only allowed to be suspended in situ for protection, the retaining structure under the ultra-wide pipeline cannot be normally constructed, resulting in excessive spacing between local retaining piles and difficulty in meeting the design requirements for bearing capacity.

[0003] Under traditional technology, the existing treatment methods are to reinforce the stratum by grouting under the pipe or to construct the retaining structure by reverse construction. When the foundation pit is deep and the stratum conditions are poor, it is difficult to ensure the reinforcement quality by grouting, and soil and sand may leak between the piles, which will lead to local instability of the foundation pit; although the reverse construction retaining structure is safe and reliable, the concrete components have a long curing time, which is easy to affect the construction period. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a deep foundation pit support structure under an ultra-wide pipeline and a deep foundation pit construction method under an ultra-wide pipeline, and the technical scheme thereof is as follows:

[0005] A supporting structure for a deep foundation pit under an ultra-wide pipeline comprises a plurality of retaining piles surrounding the foundation pit. When a projection is generated downward along a vertical direction for the ultra-wide pipeline, the retaining piles are not arranged within the range covered by the projection, and the retaining piles are arranged on both sides of the projection. A first additional retaining pile and a second additional retaining pile are arranged on the outer side of the retaining piles, and the first additional retaining pile and the second additional retaining pile are respectively located on both sides of the projection.

[0006] The deep foundation pit support structure under the super-wide pipeline as described above is further preferably arranged such that: the first additional retaining piles and the retaining piles located on the same side of the super-wide pipeline and arranged close to the super-wide pipeline are arranged side by side along the length direction of the super-wide pipeline; the second additional retaining piles and the retaining piles located on the same side of the super-wide pipeline and arranged close to the super-wide pipeline are arranged side by side along the length direction of the super-wide pipeline.

[0007] The deep foundation pit support structure under the ultra-wide pipeline as described above is further preferably further configured to include a transverse support beam, wherein the transverse support beam is located below the ultra-wide pipeline, and both ends of the transverse support beam are respectively connected to the retaining piles.

[0008] The ultra-wide pipeline under-line deep foundation pit support structure as described above is further preferably: the transverse support beams are multiple, and the multiple transverse support beams are arranged side by side with equal or unequal intervals in the vertical direction.

[0009] The above-mentioned ultra-wide pipeline under-deep foundation pit support structure is further preferably configured such that: the transverse support beam is a steel section, and the flanges at both ends of the transverse support beam are welded and connected to the retaining pile reinforcement of the retaining pile.

[0010] The ultra-wide pipeline downstream deep foundation pit support structure as described above is further preferably further configured to include a ground pre-grouting reinforced soil layer, wherein the ground pre-grouting reinforced soil layer is located outside the retaining piles and above and below the ultra-wide pipeline, and the bottom surface of the ground pre-grouting reinforced soil layer is lower than the bottom surface of the foundation pit.

[0011] The ultra-wide pipeline underground deep foundation pit support structure as described above is further preferably: the bottom surface of the ground pre-grouting reinforced soil layer is not less than 3 meters lower than the bottom surface of the foundation pit; the wall thickness of the ground pre-grouting reinforced soil layer is not less than 3 meters; the thickness of the ground pre-grouting reinforced soil layer on both sides of the projection exceeding the projection is not less than 1.5 times the diameter of a single retaining pile.

[0012] The ultra-wide pipeline under-line deep foundation pit support structure as described above is further preferably further configured to include a synchronous grouting reinforcement soil layer, wherein the synchronous grouting reinforcement soil layer is located outside the retaining piles and below the ultra-wide pipeline.

[0013] The ultra-wide pipeline underground deep foundation pit support structure as described above is further preferably: the wall thickness of the synchronous grouting reinforced soil layer is greater than the wall thickness of the ground pre-grouting reinforced soil layer, and overlaps with the ground pre-grouting reinforced soil layer within the wall thickness range of the ground pre-grouting reinforced soil layer to form a mixed reinforced soil layer.

[0014] The deep foundation pit support structure under the ultra-wide pipeline as described above is further preferably: further comprising a reverse-built retaining wall, wherein the reverse-built retaining wall is located on the inner side of the transverse support beam, connected to the transverse support beam, and located below the ultra-wide pipeline; and both ends of the reverse-built retaining wall are respectively connected to the retaining piles.

[0015] The ultra-wide pipeline under-line deep foundation pit support structure as described above is further preferably configured such that: the top-down retaining wall is a cast-in-place concrete structure with a thickness of 300 mm.

[0016] The ultra-wide pipeline under-deep foundation pit support structure as described above is further preferably: a reverse-built retaining wall steel mesh is arranged in the reverse-built retaining wall, the reverse-built retaining wall steel mesh is a double-layer bidirectional steel mesh, and the reverse-built retaining wall steel mesh is welded and connected to the retaining pile steel bars of the retaining piles.

[0017] The ultra-wide pipeline downstream deep foundation pit support structure as described above is further preferably further comprised of a grouting steel flower pipe, one end of which is connected to the reverse retaining wall, and the other end is a free end extending in a direction away from the foundation pit.

[0018] The ultra-wide pipeline downstream deep foundation pit support structure as described above is further preferably configured such that: the grouting steel flower pipe is inclined downward in a direction away from the foundation pit, and an angle range with the horizontal plane is 10° to 25°.

[0019] The ultra-wide pipeline under-line deep foundation pit support structure as described above is further preferably: the grouting steel flower pipes are multiple, arranged at equal intervals, and arranged in a plum blossom shape or a rectangle.

[0020] The ultra-wide pipeline underground deep foundation pit support structure as described above is further preferably: an additional steel mesh is provided at one end of the grouting steel flower pipe, and the additional steel mesh is anchored in the reverse retaining wall and welded to the reverse retaining wall steel mesh.

[0021] The ultra-wide pipeline under-deep foundation pit support structure as described above is further preferably further configured to include a waist beam, an inner support and a crown beam; the waist beam is located on the inner side of the reverse-built retaining wall, and is connected to the reverse-built retaining wall and the retaining piles, and the inner support is connected to the waist beam; the crown beam is located on the top of the retaining piles, and is respectively connected to the retaining piles, the first additional retaining piles, and the second additional retaining piles.

[0022] A method for constructing a deep foundation pit under an ultra-wide pipeline, comprising the following steps:

[0023] Step 1: Pre-grouting the ground to reinforce the soil at the intersection of the ultra-wide pipeline and the foundation pit to be excavated, and building retaining piles around the foundation pit to be excavated;

[0024] Step 2: excavate the foundation pit to be excavated, and after excavating to the elevation of the super-wide pipeline, construct a first transverse support beam under the super-wide pipeline, and connect the retaining piles at both ends of the first transverse support beam, and the connection point is located outside the plane where the center lines of the two retaining piles are located;

[0025] Step 3: Continue to excavate the foundation pit to be excavated, and after excavating to a certain depth, construct the second transverse support beam, and synchronously grout the soil outside the retaining piles and construct a reverse retaining wall;

[0026] Step 4: Continue to excavate the foundation pit to be excavated, construct the transverse support beam, synchronously grout reinforcement, and construct the reverse retaining wall until the design elevation of the inner support, construct the waist beam and erect the inner support;

[0027] Step 5: Continue to excavate the foundation pit, construct the transverse support beams, perform synchronous grouting reinforcement, and construct the reverse retaining wall until the foundation pit excavation is completed.

[0028] The method for constructing a deep foundation pit under an ultra-wide pipeline as described above is further preferably: in the step one, a pre-grouting sleeve valve pipe is used to perform ground pre-grouting reinforcement on the soil, and the pre-grouting sleeve valve pipe is driven into the soil at a certain angle from both sides of the ultra-wide pipeline to form a ground pre-grouting reinforced soil layer.

[0029] The method for constructing a deep foundation pit for an ultra-wide pipeline as described above is further preferably as follows: in the step one, it also includes constructing a first additional retaining pile and a second additional retaining pile outside the retaining pile; when the ultra-wide pipeline generates a projection downward in the vertical direction, the retaining piles are not arranged within the range covered by the projection, the retaining piles are arranged on both sides of the projection, and the first additional retaining pile and the second additional retaining pile are respectively located on both sides of the projection.

[0030] The method for constructing a deep foundation pit under an ultra-wide pipeline as described above is further preferably: in the step one, after the construction of the retaining piles and the first additional retaining piles and the second additional retaining piles is completed, a cap beam is constructed on the top of the retaining piles, the first additional retaining piles and the second additional retaining piles.

[0031] The method for constructing a deep foundation pit for an ultra-wide pipeline as described above is further preferably: in the step three, a grouting steel pipe is used to reinforce the soil by grouting, and the grouting steel pipe is driven from the foundation pit to be excavated into the ground pre-grouting reinforced soil layer for grouting to form a synchronous grouting reinforced soil layer; the grouting steel pipe is inclined downward in a direction away from the foundation pit, and a plurality of the grouting steel pipes are arranged at equal intervals in a plum blossom or rectangular arrangement.

[0032] The method for constructing a deep foundation pit under an ultra-wide pipeline as described above is further preferably: when connecting the transverse support beam and the retaining pile, the concrete at the connection of the retaining pile is removed to weld the reinforcing bars of the retaining pile to the transverse support beam.

[0033] The method for constructing a deep foundation pit under an ultra-wide pipeline as described above is further preferably: when constructing the reverse-built retaining wall, a reverse-built retaining wall steel mesh is arranged inside the reverse-built retaining wall, and the left and right ends of the reverse-built retaining wall are connected to the retaining piles; when connecting, the concrete at the connection of the retaining piles is removed, so that the reverse-built retaining wall steel mesh of the reverse-built retaining wall is welded and connected to the retaining pile steel bars of the retaining piles.

[0034] The method for constructing a deep foundation pit for an ultra-wide pipeline as described above is further preferably: when the grouting steel pipe is driven into the pipe, one end of the grouting steel pipe away from the foundation pit is a free end, and an additional steel mesh is arranged on the other end, the additional steel mesh is welded and connected to the steel mesh of the reverse retaining wall, and the grouting steel pipe is anchored to the reverse retaining wall.

[0035] It can be seen from the analysis that compared with the prior art, the advantages and beneficial effects of the present invention are:

[0036] In the ultra-wide pipeline under-deep foundation pit support structure of the present invention, the retaining piles, the first additional retaining piles, and the second additional retaining piles form a double-row pile retaining structure, which can solve the problem that the bearing capacity is difficult to meet the design requirements due to the excessive spacing between local retaining piles to a certain extent, and improve the bearing strength of the support structure. The two ends of the transverse support beam are respectively connected to the two retaining piles in the double-row pile retaining structure. The transverse support beam is a steel section, which can play a supporting role after installation, and no maintenance is required. The construction is convenient and fast, and the construction period can be effectively shortened. The ground pre-grouting reinforcement soil layer can improve the physical and mechanical properties of the soil and ensure the smooth implementation of the project. The synchronous grouting reinforcement soil layer can further guarantee the reinforcement effect, and the grouting steel flower pipe driven into the soil can be used as an emergency measure for the safety remediation of the foundation pit. The reverse retaining wall is a molded cast-in-place concrete structure with good controllability of the pouring quality, which can avoid soil and sand leakage between piles and ensure the local safety of the foundation pit. The grouting steel flower pipe can grout the soil and support the soil, and can also play a certain supporting role for the transverse support beam. The waist beam can change the supporting function of the inner support from point support to surface support, thereby improving the supporting strength. The crown beam is connected to the retaining pile, the first additional retaining pile, and the second additional retaining pile respectively, and can connect the first additional retaining pile, the second additional retaining pile, and multiple retaining piles into one, thereby improving the structural strength. The ultra-wide pipeline under-deep foundation pit support structure of the present invention can reduce construction risks, improve construction efficiency, and has good economic benefits.

[0037] In the method for constructing a deep foundation pit under an ultra-wide pipeline of the present invention, a double-row pile retaining structure is adopted for support. The double-row pile retaining structure is subjected to force synergistically, which can improve the distribution of soil pressure and optimize the reinforcement of the retaining piles. The soil outside the pit is reinforced by ground pre-grouting, which can reduce the disturbance of the ground when the transverse support beam is installed, making the construction process safer and more reliable. The synchronous grouting reinforcement can further ensure the reinforcement effect of the soil outside the pit, and can also be used as an emergency measure for the safety remediation of the foundation pit. At the same time, the grouting steel flower pipe can also provide support force for the transverse support beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a plan schematic diagram of the ultra-wide pipeline underground deep foundation pit support structure of the present invention.

[0039] Figure 2 It is a front elevation schematic diagram of the ultra-wide pipeline underground deep foundation pit support structure of the present invention.

[0040] Figure 3 It is a side elevation schematic diagram of the ultra-wide pipeline underground deep foundation pit support structure of the present invention.

[0041] Figure 4It is a schematic diagram of the connection between the reverse retaining wall and the grouting steel flower pipe of the present invention.

[0042] In the figure: 1-lateral support beam; 2-retaining pile; 3-first additional retaining pile; 4-reinforcement of retaining pile; 5-reverse retaining wall; 6-second additional retaining pile; 7-grouting steel flower pipe; 8-synchronous grouting reinforcement soil layer; 9-ground pre-grouting reinforcement soil layer; 10-extra-wide pipeline; 11-ground; 12-pre-grouting sleeve valve pipe; 13-crown beam; 14-additional steel mesh; 15-waist beam; 16-inner support; 17-reverse retaining wall steel mesh. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] In the description of the present invention, the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention. In the present invention, "inside" and "outside" are described with the foundation pit as the base point. The side close to the foundation pit is the inside, and the side away from the foundation pit is the outside. Ultra-wide pipelines generally refer to pipelines with a width greater than 2.5m, and the construction of retaining piles is affected because relocation is not allowed during construction. During construction, the projection of the ultra-wide pipeline conflicts with the retaining structure and affects the construction of retaining piles. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate component. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0045] Please refer to Figures 1 to 4 ,in, Figure 1 It is a schematic plan view of the deep foundation pit support structure under the ultra-wide pipeline of the present invention; Figure 2 It is a schematic front elevation view of the ultra-wide pipeline under-line deep foundation pit support structure of the present invention; Figure 3 It is a side elevation schematic diagram of the ultra-wide pipeline under-line deep foundation pit support structure of the present invention; Figure 4 It is a schematic diagram of the connection between the reverse retaining wall and the grouting steel flower pipe of the present invention. Figure 1 The omitted part in the lower middle is the location of the foundation pit; Figure 3The omitted part on the middle right is the location of the foundation pit.

[0046] like Figures 1 to 3 As shown, the present invention provides a supporting structure for a deep foundation pit under an ultra-wide pipeline, which is located below the ground 11 and mainly includes a plurality of retaining piles 2 surrounding the foundation pit. When the ultra-wide pipeline 10 generates a projection downward in the vertical direction, no retaining piles 2 are provided within the range covered by the projection, and retaining piles 2 are provided on both sides of the projection. A first additional retaining pile 3 and a second additional retaining pile 6 are provided on the outside of the retaining pile 2, and the first additional retaining pile 3 and the second additional retaining pile 6 are respectively located on both sides of the projection.

[0047] Specifically, the first additional retaining pile 3 of the present invention is arranged side by side with the retaining pile 2 located on the same side of the super-wide pipeline 10 and arranged close to the super-wide pipeline 10 along the length direction of the super-wide pipeline 10; the second additional retaining pile 6 is arranged side by side with the retaining pile 2 located on the same side of the super-wide pipeline 10 and arranged close to the super-wide pipeline 10 along the length direction of the super-wide pipeline 10. The first additional retaining pile 3 and the second additional retaining pile 6 are respectively located on both sides of the projection and on the outside of the retaining pile 2, thereby forming a double-row pile retaining structure on both sides of the projection of the super-wide pipeline 10 adjacent to the projection, which can solve the problem that the bearing capacity is difficult to meet the design requirements due to the excessive spacing between the local retaining piles 2 to a certain extent, and improve the bearing strength of the support structure.

[0048] As an improvement to the present invention, Figures 1 to 4 As shown, the present invention also provides the following improved solution:

[0049] Furthermore, the present invention also includes a transverse support beam 1, which is located below the super-wide pipeline 10, and the two ends of the transverse support beam 1 are respectively connected to two retaining piles 2 in the double-row pile retaining structure. The cross-section of the retaining pile 2 is circular, and when the transverse support beam 1 is connected to the retaining pile 2, the connection point is located outside the line connecting the center points of the two retaining piles 2 (that is, compared to the plane where the center lines of the two retaining piles 2 are located, the connection points of the left and right ends of the transverse support beam 1 and the retaining piles 2 are farther away from the foundation pit), and the retaining piles 2 can play a certain supporting role on the transverse support beam 1, thereby improving the bearing strength of the transverse support beam 1.

[0050] Furthermore, in the present invention, there are multiple transverse support beams 1, which are constructed sequentially from top to bottom as the foundation pit is excavated, and can support the side walls of the excavated foundation pit (the side walls of the foundation pit below the ultra-wide pipeline 10). During construction, multiple transverse support beams 1 are arranged side by side at equal or unequal intervals in the vertical direction. For example, when they are arranged side by side at equal intervals, the interval can be 0.5 meters; as the excavation depth increases, the soil pressure increases, and the interval can also be less than 0.5 meters.

[0051] Furthermore, in the present invention, the transverse support beam 1 is a rolled or welded steel section, which can play a supporting role after installation, and does not require maintenance. The construction is convenient and quick, and the construction period can be effectively shortened. During construction, the transverse support beam 1 is simply supported on the retaining pile 2, and the flanges at both ends of the transverse support beam 1 are welded and connected to the retaining pile reinforcement 4 of the retaining pile 2. The transverse support beam 1 is preferably an I-beam. During installation, the two flanges are arranged vertically and the web is arranged horizontally, which can play a bearing role on the soil.

[0052] Furthermore, the present invention also includes a ground pre-grouting reinforcement soil layer 9, which is formed by grouting using a pre-grouting sleeve valve pipe 12 before excavating the foundation pit. The ground pre-grouting reinforcement soil layer 9 is located on the outside of the retaining pile 2, and extends from the top of the super-wide pipeline 10 to the bottom of the super-wide pipeline 10, which can improve the physical and mechanical properties of the soil. The bottom surface of the ground pre-grouting reinforcement soil layer 9 is lower than the bottom surface of the foundation pit, so that it can be ensured that the soil above and below the super-wide pipeline 10 within the elevation range of the foundation pit is improved, ensuring the smooth implementation of the project. Preferably, the bottom surface of the ground pre-grouting reinforcement soil layer 9 is not less than 3 meters lower than the bottom surface of the foundation pit; the wall thickness of the ground pre-grouting reinforcement soil layer 9 is not less than 3 meters; the thickness of the ground pre-grouting reinforcement soil layer 9 on both sides of the projection exceeding the projection is not less than 1.5 times the diameter of a single retaining pile, which is beneficial to the safety of the foundation pit and can also be adjusted according to actual working conditions.

[0053] Furthermore, the present invention also includes a synchronous grouting reinforcement soil layer 8. The synchronous grouting reinforcement soil layer 8 is located outside the retaining pile 2 and below the ultra-wide pipeline 10. The wall thickness of the synchronous grouting reinforcement soil layer 8 is greater than the wall thickness of the ground pre-grouting reinforcement soil layer 9, and overlaps with the ground pre-grouting reinforcement soil layer 9 within the wall thickness range of the ground pre-grouting reinforcement soil layer 9 to form a mixed reinforcement soil layer. The synchronous grouting reinforcement soil layer 8 is formed by grouting with the grouting steel flower pipe 7 during the foundation pit construction. With the excavation of the foundation pit, the soil of the ground pre-grouting reinforcement soil layer 9 and the soil outside the ground pre-grouting reinforcement soil layer 9 can be improved for the second time, further reinforced, and ensure the reinforcement effect of the soil; it can also form an anchor body with the grouting steel flower pipe 7 to reduce the span of the transverse support beam 1. At the same time, the grouting steel flower pipe 7 driven into the soil can also be used as an emergency measure for the safety remediation of the foundation pit.

[0054] Furthermore, in the present invention, a reverse-built retaining wall 5 is also included. The reverse-built retaining wall 5 is located on the inner side of the transverse support beam 1, is connected to the transverse support beam 1, and is located below the super-wide pipeline 10. The two ends of the reverse-built retaining wall 5 are respectively connected to the retaining piles 2, which can further improve the supporting force of the support structure. The reverse-built retaining wall 5 is a molded cast-in-place concrete structure with good controllability of pouring quality. It can avoid soil and sand leakage between piles and ensure the local safety of the foundation pit. The reverse-built retaining wall 5 is built with a reverse-built retaining wall steel mesh 17. The reverse-built retaining wall steel mesh 17 is a double-layer bidirectional steel mesh, which can improve the bearing capacity of the reverse-built retaining wall 5 and can be welded to the retaining pile steel bars 4 of the retaining pile 2 when connected to the retaining pile 2. Preferably, the thickness of the reverse-built retaining wall 5 is 300 mm.

[0055] Furthermore, the present invention also includes a grouting steel flower pipe 7, which can grout the soil and support the soil. One end of the grouting steel flower pipe 7 is connected to the reverse retaining wall 5, and the other end is a free end, extending in the direction away from the foundation pit. Preferably, the grouting steel flower pipe 7 is inclined downward in the direction away from the foundation pit, and the angle range with the horizontal plane is 10° to 25°, which can prevent the grouting liquid from flowing out, and can play a certain role in advance reinforcement of the foundation pit excavation. During construction, there are multiple grouting steel flower pipes 7, and the multiple grouting steel flower pipes 7 are arranged at equal intervals to ensure the grouting effect, and the arrangement form is plum blossom or rectangular.

[0056] Furthermore, in the present invention, one end of the grouting steel flower pipe 7 is connected with an additional steel mesh 14, which is anchored in the reverse retaining wall 5 and welded to the reverse retaining wall steel mesh 17, which is not only conducive to the fixation of the grouting steel flower pipe 7, but also enables the grouting steel flower pipe 7 to play a certain supporting role on the transverse support beam 1 (the grouting steel flower pipe 7 can be used as a span-reducing support for the transverse support beam 1). Multiple grouting steel flower pipes 7 are flush at one end connected to the reverse retaining wall 5. In terms of length selection, generally speaking, the length of the grouting steel flower pipe 7 should be greater than twice the spacing between the retaining piles 2 under the ultra-wide pipeline. Multiple grouting steel flower pipes 7 can be selected to have equal lengths, such as 6 meters.

[0057] Furthermore, in the present invention, a waist beam 15, an inner support 16 and a crown beam 13 are also included. The waist beam 15 is located on the inner side of the reverse retaining wall 5, and can be divided into multiple layers in the vertical direction according to the support requirements of the foundation pit, such as a first layer of waist beams 15, a second layer of waist beams 15, etc. The waist beam 15 is connected to the reverse retaining wall 5 and the retaining piles 2, and the inner support 16 is connected to the waist beam 15. The waist beam 15 can change the support of the inner support 16 to the side wall of the foundation pit (also including the retaining piles 2 and the reverse retaining wall 5) from point support to surface support, thereby improving the support strength. The crown beam 13 is located at the top of the retaining piles 2, the first additional retaining piles 3, and the second additional retaining piles 6, and is respectively connected to the retaining piles 2, the first additional retaining piles 3, and the second additional retaining piles 6. There is one crown beam 13, and the crown beam 13 is a ring with an opening, and the opening is located at the super-wide pipeline 10. One crown beam 13 connects all the retaining piles 2 and the first additional retaining pile 3 and the second additional retaining pile 6, which is equivalent to the ring-shaped crown beam 13 being interrupted by the super-wide pipeline 10, and then turning to the first additional retaining pile 3 and the second additional retaining pile 6, and finally terminating, so that the first additional retaining pile 3, the second additional retaining pile 6, and multiple retaining piles 2 can be connected as one, thereby improving the structural strength.

[0058] In summary, the ultra-wide pipeline underground deep foundation pit support structure of the present invention includes retaining piles 2, first additional retaining piles 3, second additional retaining piles 6, transverse support beams 1, ground pre-grouting reinforced soil layer 9, synchronous grouting reinforced soil layer 8, reverse retaining wall 5, grouting steel flower pipe 7, waist beam 15, inner support 16 and crown beam 13. The retaining piles 2, the first additional retaining piles 3, and the second additional retaining piles 6 form a double-row pile retaining structure, which can to a certain extent solve the problem that the bearing capacity is difficult to meet the design requirements due to the excessive spacing between local retaining piles 2, and improve the bearing strength of the support structure. The two ends of the transverse support beam 1 are respectively connected to the two retaining piles 2 in the double-row pile retaining structure. The transverse support beam 1 is a steel section, which can play a supporting role after installation. No maintenance is required. The construction is convenient and quick, and the construction period can be effectively shortened. The ground pre-grouting reinforced soil layer 9 can improve the physical and mechanical properties of the soil and ensure the smooth implementation of the project. The synchronous grouting reinforcement soil layer 8 can further guarantee the reinforcement effect, and the synchronous grouting reinforcement soil layer 8 can also be used as an emergency measure for the safety remediation of the foundation pit. The reverse retaining wall 5 is a molded cast-in-place concrete structure with good controllability of the pouring quality, which can avoid leakage of soil and sand between piles and ensure the local safety of the foundation pit. The grouting steel flower pipe 7 can grout the soil and support the soil, and can also play a certain supporting role for the transverse support beam 1. The waist beam 15 can change the supporting function of the inner support 16 from point support to surface support, thereby improving the support strength. The crown beam 13 is respectively connected to the retaining pile 2, the first additional retaining pile 3, and the second additional retaining pile 6, and can connect the first additional retaining pile 3, the second additional retaining pile 6, and multiple retaining piles 2 into one, thereby improving the structural strength. The ultra-wide pipeline line deep foundation pit support structure of the present invention can reduce construction risks, improve construction efficiency, and has good economic benefits.

[0059] like Figures 1 to 4 As shown, the present invention also provides a method for constructing a deep foundation pit under an ultra-wide pipeline, comprising the following steps:

[0060] Step 1: Ground pre-grouting is used to reinforce the soil at the intersection of the ultra-wide pipeline 10 and the foundation pit to be excavated, and retaining piles 2 are constructed around the foundation pit to be excavated.

[0061] 1.1 Use the pre-grouting sleeve valve pipe 12 to carry out ground pre-grouting reinforcement on the soil.

[0062] During ground pre-grouting reinforcement, the pre-grouting sleeve valve pipe 12 is driven into the soil at a certain angle from both sides of the super-wide pipeline 10 to form a ground pre-grouting reinforced soil layer 9 (just ensure the formation of the predetermined ground pre-grouting reinforced soil layer 9. Due to the influence of the super-wide pipeline 10, the pre-grouting sleeve valve pipe 12 cannot be set vertically and can only be driven into the bottom of the super-wide pipeline 10 at a certain angle on both sides of the super-wide pipeline 10. The angle range of the pre-grouting sleeve valve pipe 12 during ground pre-grouting reinforcement can be determined according to the actual working conditions). The soil is improved before excavation to ensure smooth construction of the project.

[0063] 1.2 Construct retaining piles 2.

[0064] A plurality of retaining piles 2 are constructed around the edge of the foundation pit to be excavated, and a first additional retaining pile 3 and a second additional retaining pile 6 are constructed. The positions of the retaining piles 2, the first additional retaining piles 3 and the second additional retaining piles 6 are as follows: when the projection of the super-wide pipeline 10 is generated downward in the vertical direction, no retaining piles 2 are arranged within the range covered by the projection, and retaining piles 2 are arranged on both sides of the projection, and the first additional retaining piles 3 and the second additional retaining piles 6 are respectively arranged on both sides of the projection, thereby forming a double-row pile retaining structure on both sides of the projection of the super-wide pipeline 10, close to the projection, which can solve the problem that the bearing capacity is difficult to meet the design requirements due to the excessive spacing between the local retaining piles 2 to a certain extent.

[0065] 1.3 Construct the crown beam 13.

[0066] After the construction of the retaining piles 2 and the first additional retaining piles 3 and the second additional retaining piles 6 is completed, the soil is excavated and a cap beam 13 is built on the top of the retaining piles 2, the first additional retaining piles 3 and the second additional retaining piles 6, thereby connecting the first additional retaining piles 3, the second additional retaining piles 6 and multiple retaining piles 2 into one, thereby improving the structural strength.

[0067] Step 2: Dig the foundation pit to be excavated. After digging to the elevation of the super-wide pipeline 10, construct the first transverse support beam 1 under the super-wide pipeline 10, and connect the left and right ends of the first transverse support beam 1 to the retaining piles 2. The connection point is located outside the plane where the center lines of the two retaining piles 2 are located, that is, compared with the plane where the center lines of the two retaining piles 2 are located, the connection points between the left and right ends of the transverse support beam 1 and the retaining piles 2 are farther away from the foundation pit.

[0068] 2.1 Excavate the foundation pit to the 10th elevation of the super-wide pipeline.

[0069] 2.2 Construct the first transverse support beam 1.

[0070] When constructing the first transverse support beam 1, the concrete at the connection point of the retaining pile 2 is chiseled out to expose the retaining pile reinforcement 4, and the flanges at both ends of the transverse support beam 1 are welded to the retaining pile reinforcement 4. Spot welding or full welding can be used according to the connection strength requirements. The first additional retaining pile 3, the second additional retaining pile 6, and the plurality of retaining piles 2 form a double row of retaining piles. The plurality of retaining piles 2 can be collectively referred to as the front row retaining piles, and the first additional retaining pile 3 and the second additional retaining pile 6 can be collectively referred to as the rear row retaining piles. The transverse support beam 1 is connected to the front row retaining piles, and the connection point is located between the plane where the center line of the front row retaining piles is located and the plane where the center line of the rear row retaining piles is located, which can ensure the firmness of the connection.

[0071] Step 3: Continue to excavate the foundation pit. After excavating to a certain depth, construct the second transverse support beam 1, and synchronously grout the soil outside the retaining piles 2 and construct the reverse retaining wall 5.

[0072] 3.1 Continue to excavate the foundation pit until it is 0.5 meters away from the first transverse support beam.

[0073] 3.2 Construct the second transverse support beam 1.

[0074] 3.3 Drive the grouting steel pipe 7 to reinforce the soil by grouting.

[0075] The soil is reinforced by grouting steel pipe 7. The grouting steel pipe 7 is driven from the foundation pit to be excavated into the ground pre-grouting reinforcement soil layer 9 and grouting the ground pre-grouting reinforcement soil layer 9 and the outer side of the ground pre-grouting reinforcement soil layer 9 to form a synchronous grouting reinforcement soil layer 8, which can further improve the soil. The grouting steel pipe 7 is tilted downward in the direction away from the foundation pit, and multiple grouting steel pipes 7 are arranged at equal intervals in a plum blossom or rectangular arrangement.

[0076] 3.4 Construct reverse retaining wall 5.

[0077] When constructing the reverse-built retaining wall 5, a reverse-built retaining wall steel mesh 17 is arranged inside the reverse-built retaining wall 5, and the left and right ends of the reverse-built retaining wall 5 are connected to the retaining piles 2. When connecting, the concrete at the connecting part of the retaining piles 2 is removed, so that the reverse-built retaining wall steel mesh 17 of the reverse-built retaining wall 5 is welded to the retaining pile steel bars 4 of the retaining piles 2.

[0078] When constructing the reverse-built retaining wall 5, it also includes connecting the reverse-built retaining wall 5 with the grouting steel pipe 7. When connecting, the end of the grouting steel pipe 7 away from the foundation pit is a free end, and the other end is connected to an additional steel mesh 14. The additional steel mesh 14 is welded to the reverse-built retaining wall steel mesh 17, and the grouting steel pipe 7 is anchored to the reverse-built retaining wall 5.

[0079] Step 4: Continue to excavate the foundation pit, construct the transverse support beam 1, simultaneously grouting reinforcement, and construct the reverse retaining wall 5 until the design elevation of the inner support 16, construct the waist beam 15 and erect the inner support 16.

[0080] Step 5: Continue to excavate the foundation pit, construct the transverse support beam 1, perform synchronous grouting reinforcement, and construct the reverse retaining wall 5 until the foundation pit excavation is completed.

[0081] In the method for constructing a deep foundation pit for an ultra-wide pipeline of the present invention, a double-row pile retaining structure is used for support. The double-row pile retaining structure is subjected to force in a coordinated manner, which can improve the distribution of soil pressure and optimize the reinforcement of the retaining piles (the retaining piles 1 on both sides of the ultra-wide pipeline 10 are subjected to greater force due to the large width of the soil body they share, and their bearing capacity is difficult to meet the requirements. The double-row pile retaining structure and the pile top crown beam 13 form a frame system, and the internal force distribution is different from the continuous beam model of the single-row pile, which can significantly reduce the bending moment of the pile body and reduce the reinforcement); the soil outside the pit is reinforced by ground pre-grouting, which can reduce the disturbance of the ground during the installation of the transverse support beam 1, making the construction process safer and more reliable; the synchronous grouting reinforcement can further ensure the reinforcement effect of the soil outside the pit, and can also be used as an emergency measure for the safety remediation of the foundation pit. At the same time, the grouting steel flower pipe 7 can also provide support for the transverse support beam 1.

[0082] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A deep foundation pit support structure for an ultra-wide pipeline, comprising a plurality of retaining piles surrounding the foundation pit, characterized in that: When the projection of the ultra-wide pipeline is generated downward in the vertical direction, the guard piles are not provided within the range covered by the projection, and the guard piles are provided on both sides of the projection; A first additional guard pile and a second additional guard pile are provided outside the guard pile, and the first additional guard pile and the second additional guard pile are respectively located on both sides of the projection. Also includes: A transverse support beam, wherein the transverse support beam is located below the super-wide pipeline, and both ends of the transverse support beam are respectively connected to the retaining piles; A reverse-built retaining wall, the reverse-built retaining wall is located inside the transverse support beam, connected to the transverse support beam, and located below the super-wide pipeline; both ends of the reverse-built retaining wall are respectively connected to the retaining piles; The reverse-built retaining wall is provided with a reverse-built retaining wall steel mesh, the reverse-built retaining wall steel mesh is a double-layer bidirectional steel mesh, and the reverse-built retaining wall steel mesh is welded to the retaining pile steel bars of the retaining piles. Also included: waist beam, inner support and crown beam; The waist beam is located on the inner side of the reverse-built retaining wall and is connected to the reverse-built retaining wall and the retaining piles, and the inner support is connected to the waist beam; The cap beam is located at the top of the retaining pile, and is respectively connected to the retaining pile, the first additional retaining pile, and the second additional retaining pile. The number of the crown beam is one, and the crown beam is in a ring shape with an opening, the opening is located at the super-wide pipeline, and the crown beam connects all the retaining piles and the first additional retaining piles and the second additional retaining piles. The crown beam connects the first additional retaining pile, the second additional retaining pile, and the plurality of retaining piles into one.

2. The ultra-wide pipeline underground deep foundation pit support structure according to claim 1 is characterized in that: There are multiple transverse support beams, and the multiple transverse support beams are arranged side by side with equal or unequal intervals in the vertical direction; The transverse support beam is a steel section, and the flanges at both ends of the transverse support beam are welded to the reinforcement bars of the retaining piles.

3. The ultra-wide pipeline underground deep foundation pit support structure according to claim 1 is characterized in that: Also includes: A ground pre-grouting reinforced soil layer, wherein the ground pre-grouting reinforced soil layer is located outside the retaining piles and above and below the ultra-wide pipeline, and the bottom surface of the ground pre-grouting reinforced soil layer is lower than the bottom surface of the foundation pit; The bottom surface of the ground pre-grouting reinforced soil layer is not less than 3 meters lower than the bottom surface of the foundation pit; The wall thickness of the ground pre-grouting reinforced soil layer is not less than 3 meters; The thickness of the ground pre-grouting reinforced soil layer beyond the projection on both sides of the projection is not less than 1.5 times the diameter of a single retaining pile.

4. The ultra-wide pipeline underground deep foundation pit support structure according to claim 3 is characterized in that: Also includes: A synchronous grouting reinforcement soil layer, wherein the synchronous grouting reinforcement soil layer is located outside the retaining piles and below the ultra-wide pipeline; The wall thickness of the synchronous grouting reinforced soil layer is greater than the wall thickness of the ground pre-grouting reinforced soil layer, and it overlaps with the ground pre-grouting reinforced soil layer within the wall thickness range of the ground pre-grouting reinforced soil layer to form a mixed reinforced soil layer.

5. The ultra-wide pipeline underground deep foundation pit support structure according to claim 1 is characterized in that: The top-down retaining wall is a cast-in-place concrete structure with a thickness of 300 mm.

6. The ultra-wide pipeline underground deep foundation pit support structure according to claim 1 is characterized in that: Also includes: A grouting steel flower pipe, one end of which is connected to the reverse retaining wall, and the other end is a free end extending in a direction away from the foundation pit.

7. The ultra-wide pipeline underground deep foundation pit support structure according to claim 6 is characterized in that: Also includes: The grouting steel flower pipe is inclined downward in a direction away from the foundation pit, and the angle between the grouting steel flower pipe and the horizontal plane is in the range of 10° to 25°; The grouting steel flower tubes are multiple and are arranged at equal intervals in a plum blossom or rectangular shape; An additional steel mesh is provided at one end of the grouting steel flower pipe, and the additional steel mesh is anchored in the reverse-built retaining wall and is welded to the steel mesh of the reverse-built retaining wall.

8. A method for constructing a deep foundation pit under an ultra-wide pipeline according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Pre-grouting the ground to reinforce the soil at the intersection of the ultra-wide pipeline and the foundation pit to be excavated, and building retaining piles around the foundation pit to be excavated; Step 2: excavate the foundation pit to be excavated, and after excavating to the elevation of the super-wide pipeline, construct a first transverse support beam under the super-wide pipeline, and connect the retaining piles at both ends of the first transverse support beam, and the connection point is located outside the plane where the center lines of the two retaining piles are located; Step 3: Continue to excavate the foundation pit to be excavated, and after excavating to a certain depth, construct the second transverse support beam, and synchronously grout the soil outside the retaining piles and construct a reverse retaining wall; Step 4: Continue to excavate the foundation pit to be excavated, construct the transverse support beam, synchronously grout reinforcement, and construct the reverse retaining wall until the design elevation of the inner support, construct the waist beam and erect the inner support; Step 5: Continue to excavate the foundation pit, construct the transverse support beams, perform synchronous grouting reinforcement, and construct the reverse retaining wall until the foundation pit excavation is completed.

9. The method for constructing a deep foundation pit under an ultra-wide pipeline according to claim 8, characterized in that: In the step 1, the soil is pre-grouted and reinforced on the ground using a pre-grouting sleeve valve pipe, and the pre-grouting sleeve valve pipe is driven into the soil at a certain angle from both sides of the super-wide pipeline to form a ground pre-grouting reinforced soil layer; In the step 1, it also includes constructing a first additional retaining pile and a second additional retaining pile outside the retaining pile; when the ultra-wide pipeline generates a projection downward in the vertical direction, the retaining pile is not arranged within the range covered by the projection, the retaining piles are arranged on both sides of the projection, and the first additional retaining pile and the second additional retaining pile are respectively located on both sides of the projection; In the step 1, after the construction of the retaining piles and the first additional retaining piles and the second additional retaining piles is completed, a cap beam is constructed on the top of the retaining piles, the first additional retaining piles and the second additional retaining piles; In the step three, grouting steel pipes are used to reinforce the soil by grouting. The grouting steel pipes are driven from the foundation pit to be excavated into the ground pre-grouting reinforced soil layer to form a synchronous grouting reinforced soil layer; the grouting steel pipes are inclined downward in the direction away from the foundation pit, and multiple grouting steel pipes are arranged at equal intervals in a plum blossom shape or a rectangular arrangement.

10. The method for constructing a deep foundation pit under an ultra-wide pipeline according to claim 9, characterized in that: When connecting the transverse support beam and the retaining pile, the concrete at the connecting part of the retaining pile is removed, so that the transverse support beam and the retaining pile reinforcement of the retaining pile are welded and connected; When constructing the reverse-built retaining wall, a reverse-built retaining wall steel mesh is arranged inside the reverse-built retaining wall, and the left and right ends of the reverse-built retaining wall are connected to the retaining piles; when connecting, the concrete at the connecting part of the retaining piles is removed, so that the reverse-built retaining wall steel mesh of the reverse-built retaining wall is welded to the retaining pile steel bars of the retaining piles; When the grouting steel pipe is driven in, one end of the grouting steel pipe away from the foundation pit is a free end, and an additional steel mesh is arranged on the other end. The additional steel mesh is welded and connected to the steel mesh of the reverse retaining wall, and the grouting steel pipe is anchored to the reverse retaining wall.

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