Reinforced concrete inner support for deep foundation pit and construction method

Abstract

The present application relates to a kind of deep foundation pit reinforced concrete inner support and construction method, comprising the following steps: foundation pit outer support structure construction and foundation pit earthwork excavation;Foundation pit inner support structure construction;Foundation pit excavation to design depth, then excavate water collecting ditch in foundation pit bottom;Foundation pit inner support structure removal.The beneficial effects of the present application are: waterproof structure at the junction of underground continuous wall and horizontal ring beam, compared with traditional waterproof structure, groundwater can be actively drained, underground water is actively drained to the outside of waterproof felt through inclined water collecting plate, and is discharged through horizontal water collecting pipe and vertical drainage pipe, avoiding existing support structure as part of the main structure, leakage occurs at the interface;Concrete horizontal inner support is poured in sections, and steel support connection is set at the side, effectively avoiding conflict with main structure column, while ensuring effective transmission of horizontal axial force.

Description

Technical Field

[0001] This invention relates to the construction of internal support structures in deep foundation pits, and more particularly to a reinforced concrete internal support for deep foundation pits and its construction method. Background Technology

[0002] During foundation pit excavation, the traditional method involves excavating layer by layer downwards and constructing the support system. After the pit reaches the designed depth, the main structure is then constructed layer by layer upwards from the bottom. However, because the existing support structure is prone to intersecting and colliding with the main structure within the pit, the traditional construction method involves casting the existing support structure within the main structure. After construction is completed, the existing support structure is cut and removed. While this method effectively ensures that the existing support structure is not damaged before the main structure is completed, thus guaranteeing safety within the pit, leakage is likely to occur at the interface between the existing support structure and the main structure. Furthermore, because the existing support structure passes through the main structure, its removal can easily damage the main structure, creating a weak interface within the main structure and reducing its load-bearing capacity. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for constructing reinforced concrete internal supports for deep foundation pits.

[0004] The construction method for this type of deep foundation pit reinforced concrete internal support includes the following construction steps:

[0005] Step 1: Construction of external support structure and excavation of foundation pit: Construct underground continuous wall along the outer side of the foundation pit excavation line, and then excavate one layer of foundation pit soil;

[0006] Step 2: Construction of the support structure within the foundation pit: The construction of horizontal ring beams and horizontal internal bracing forms the support structure within the foundation pit; the horizontal ring beams are connected to vertical drainage pipes.

[0007] Step 3: Repeat Step 1 and Step 2 until the foundation pit is excavated to the design depth. Then, excavate a water collection ditch at the bottom of the foundation pit and extend the vertical drainage pipe into the water collection ditch.

[0008] Step 4: Construction of the main structure: Construct the main structure side walls, main structure columns, and main structure floor slabs in the foundation pit layer by layer from bottom to top. Inject waterproof mortar at the interface between the main structure side walls and the support structure in the foundation pit. The steel sleeve is cast integrally on the main structure columns.

[0009] Step 5: Removal of the support structure inside the foundation pit: Weld steel brackets onto the steel sleeves, then connect the horizontal inner supports and the steel brackets with steel wire ropes. Cut the horizontal inner supports along the side wall of the main structure, release the steel wire ropes, lower the horizontal inner supports as a whole, and finally remove the reaction frame and steel supports, and cut and transport the horizontal inner supports in sections.

[0010] Preferably, in step two, the specific method for constructing the horizontal ring beam is as follows: connecting steel bars are inserted into the diaphragm wall at the contact surface between the horizontal ring beam and the diaphragm wall; then the steel bars of the horizontal ring beam are tied and formwork is erected; then the concrete of the horizontal ring beam is poured, and connecting steel bars are poured inside the horizontal ring beam; when the horizontal ring beam is part of the side wall of the main structure, a horizontal water collection pipe, a vertical drainage pipe, and an inclined water collection plate are installed on the outside of the horizontal ring beam; waterproof felt is laid on the surface of the diaphragm wall; steel mesh is installed on the upper and lower surfaces of the horizontal ring beam; multiple inclined plastic strips are provided on the inclined water collection plate, the plastic strips are inclined outwards, the connecting steel bars pass through the plastic strips, geotextile is wrapped on the inclined water collection plate, and the horizontal water collection pipe is a porous plastic pipe.

[0011] Preferably, in step two, the upper and lower ends of the inclined water collection plate are located on the outer side of the waterproof felt, respectively.

[0012] Preferably, in step two, during the construction of the horizontal inner support, the planar position of the horizontal inner support is measured and laid out, the horizontal inner support reinforcement is tied, the formwork is erected, and then the horizontal inner support is poured.

[0013] Preferably, in step two, when the horizontal inner support intersects with the main structure column, the horizontal inner support is disconnected at the intersection, and U-shaped ends are placed at the two disconnected ends. Then, the side formwork of the horizontal support is erected along the side of the U-shaped ends, and the concrete of the horizontal inner support is poured. After the concrete of the horizontal inner support reaches the design strength, the side formwork of the horizontal support is removed, and then the reaction frame and steel support are installed and fixed on the two U-shaped ends using fastening bolts. Arc-shaped pads are provided between the steel supports, and the two U-shaped ends are temporarily fixed with positioning steel bars, which are spot-welded to the U-shaped ends.

[0014] Preferably, in step two, a pre-embedded bolt sleeve is provided on the U-shaped end, and the fastening bolt is screwed into the pre-embedded bolt sleeve.

[0015] Preferably, in step four, the main structural side walls, main structural columns, and main structural floor slabs within the foundation pit are constructed layer by layer from bottom to top. Upper and lower grouting pipes are installed at the contact interface between the main structural side walls and the horizontal ring beam and horizontal internal support. After the main structural side walls are cast, waterproof mortar is injected into the contact interface between the main structural side walls and the horizontal ring beam and horizontal internal support through the upper and lower grouting pipes. The main structural columns pass through the two U-shaped ends of the horizontal internal support and are integrally cast. A steel sleeve is installed at the segment passing through the horizontal internal support as a side formwork for the main structural column, and the steel sleeve is integrally cast onto the main structural column. The inner side of the steel sleeve is provided with studs.

[0016] Preferably, step five specifically involves first welding steel brackets onto the steel sleeve, then fixing one end of a steel wire rope to the steel support and the other end to the steel bracket, and tightening the wire rope to keep it taut. Then, the horizontal inner support is cut along the side wall of the main structure. After the horizontal inner support is cut, square wooden blocks are placed on the floor slab of the main structure, the wire rope is released, and the entire horizontal inner support is lowered onto the square wooden blocks. Finally, the reaction frame and steel support are removed, and the horizontal inner support is cut into sections and transported away.

[0017] The reinforced concrete internal support for the deep foundation pit is obtained by any of the methods described above.

[0018] The beneficial effects of this invention are:

[0019] 1) The waterproof structure at the junction of the underground continuous wall and the horizontal ring beam can actively divert groundwater compared to traditional waterproof structures. The groundwater is actively diverted to the outside of the waterproof asphalt felt through the inclined water collection plate and discharged through the horizontal water collection pipe and the vertical drainage pipe, thus avoiding leakage at the interface when the existing support structure is part of the main structure.

[0020] 2) The concrete horizontal internal support is poured in sections, and steel support is set on the side to connect it, which effectively avoids conflict with the main structure columns and ensures the effective transmission of horizontal axial force.

[0021] 3) U-shaped ends are set at the sections of the concrete horizontal inner support, which improves the strength and reliability of the connection node between the steel support and the horizontal inner support. Positioning steel bars are set between the U-shaped ends for temporary fixation, ensuring the relative position between the U-shaped ends and reducing the difficulty of installing the steel support later.

[0022] 4) Square steel sleeves are installed at the intersection of the main structural columns and the horizontal internal supports. This avoids the problem of difficulty in setting up formwork at the intersection and improves the structural strength of the intersection, providing stable and reliable support for the installation of the steel brackets.

[0023] 5) The horizontal inner support is hoisted to the ground as a whole by the steel bracket welded to the steel sleeve, and then cut and dismantled in sections, which reduces the difficulty of dismantling the horizontal inner support and ensures the safety of the dismantling workers. Attached Figure Description

[0024] Figure 1 This is a flowchart of the construction process for reinforced concrete internal supports in deep foundation pits.

[0025] Figure 2 Diagram showing the reinforcement arrangement of diaphragm wall connections;

[0026] Figure 3 Schematic diagram of waterproofing at the junction of the diaphragm wall and the horizontal ring beam;

[0027] Figure 4 Detailed drawing of the junction between the diaphragm wall and the horizontal ring beam;

[0028] Figure 5 This is a schematic diagram of the inclined water collection plate structure;

[0029] Figure 6 Schematic diagram of the support structure in deep foundation pit;

[0030] Figure 7 Schematic diagram of U-shaped support setup in deep foundation pit;

[0031] Figure 8 Schematic diagram of the three-dimensional structure of the deep U-shaped end;

[0032] Figure 9 Schematic diagram of U-shaped support setup in deep foundation pit;

[0033] Figure 10 Schematic diagram of the removal of internal supports in deep foundation pits;

[0034] Figure 11 3D structural schematic diagram of the dismantling of internal supports in a deep foundation pit;

[0035] Figure 12 Schematic diagram of the dismantling and placement of supports in a deep foundation pit.

[0036] The markings in the diagram are: 11-Diaphragm wall, 12-Horizontal ring beam, 13-Horizontal internal support, 14-Main structure side wall, 15-Main structure column, 16-Main structure floor slab, 21-Connecting reinforcement, 22-Horizontal water collection pipe, 23-Inclined water collection board, 24-Geotextile, 25-Waterproof felt, 26-Vertical drainage pipe, 27-Water collection ditch, 31-U-shaped end, 32-Embedded bolt sleeve, 33-Positioning reinforcement, 34-Reaction frame, 35-Steel support, 36-Fasting bolt, 37-Horizontal support side formwork, 41-Reinforcing mesh, 42-Upper grouting pipe, 43-Lower grouting pipe, 51-Steel sleeve, 52-Stokes, 53-Steel bracket, 54-Steel wire rope, 55-Arc-shaped pad, 56-Square wooden block. Detailed Implementation

[0037] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0038] Example 1

[0039] As one example, such as Figures 1 to 12 As shown, the construction method for this deep foundation pit reinforced concrete internal support includes the following construction steps:

[0040] Step 1: Construction of external support structure and excavation of foundation pit: Construct the underground continuous wall support structure on the outside of the foundation pit along the outer edge of the foundation pit excavation line, and then carry out the foundation pit excavation operation. Construct one layer of internal support structure for each layer of excavation.

[0041] Step 2: Construction of the support structure inside the foundation pit: The support structure inside the foundation pit mainly includes the horizontal ring beam 12 and the horizontal internal bracing 13.

[0042] Construction of horizontal ring beam 12: At the contact surface between horizontal ring beam 12 and underground diaphragm wall 11, reinforcing steel bars 21 are inserted into the underground diaphragm wall 11. Then, the reinforcing steel bars of horizontal ring beam 12 are tied and formwork is erected. Then, the concrete of horizontal ring beam 12 is poured, and the reinforcing steel bars 21 are poured into horizontal ring beam 12 together. When horizontal ring beam 12 is part of the main structure side wall 14, horizontal water collection pipe 22, vertical drainage pipe 26 and inclined water collection plate 23 are set on the outside of horizontal ring beam 12, and waterproof felt 25 is laid close to the underground diaphragm wall 11. The upper and lower surfaces of horizontal ring beam 12 are provided with raised steel mesh 41. By setting steel mesh 41, the connection strength at the interface between horizontal ring beam 12 and main structure side wall 14 is improved to avoid leakage.

[0043] Construction of horizontal internal support 13: Measure and lay out the plan position of horizontal internal support 13, tie the steel reinforcement of horizontal internal support 13, erect the formwork, and then pour the horizontal internal support 13; In the case where horizontal internal support 13 intersects with the main structure column 15, disconnect the horizontal internal support 13 at the intersection of horizontal internal support 13 and main structure column 15, and place U-shaped end 31 at the two ends of the disconnection, then erect the horizontal support side formwork 37 close to the side of the U-shaped end 31, and then pour the concrete of horizontal internal support 13. After the concrete of horizontal internal support 13 reaches the design strength, remove the horizontal support side formwork 37, and then use fastening bolts 36 to install and fix the reaction frame 34 and steel support 35 on the two U-shaped end 31;

[0044] Step 3: Continue to excavate the foundation pit, lay waterproof asphalt 25 along the underground continuous wall 11 and extend the vertical drainage pipe 26, and construct the support structure inside the foundation pit layer by layer according to the method described in Step 2 until the foundation pit is excavated to the design depth. Then, excavate the water collection ditch 927 at the bottom of the foundation pit and connect the vertical drainage pipe 26 into the water collection ditch 27.

[0045] Step 4: Construction of the main structure: The main structure side walls 14, main structure columns 15, and main structure floor slabs 16 within the foundation pit are constructed layer by layer from bottom to top. When the main structure side walls 14 are constructed close to the underground continuous wall 11, damage to the waterproof felt 25 should be avoided. At the interface between the main structure side walls 14 and the existing horizontal ring beam 12 and horizontal internal support 13, upper grouting pipes 42 and lower grouting pipes 43 are installed. After the main structure side walls 14 are cast, waterproof mortar is injected into the interface through the upper grouting pipes 42 and lower grouting pipes 43. The main structure columns 15 pass directly between the two U-shaped ends 31 of the horizontal internal support 13 and are cast integrally. A steel sleeve 51 is installed as the side formwork of the main structure column 15 at the section passing through the horizontal internal support 13, and the steel sleeve 51 is cast integrally on the main structure column 15.

[0046] Step 5: Removal of the support structure inside the foundation pit: First, weld steel brackets 53 onto the steel sleeve 51. Then, fix one end of the wire rope 54 to the steel support 35 and the other end to the steel bracket 53, and tighten the wire rope 54 to keep it taut. Then, cut the horizontal inner support 13 along the side wall 14 of the main structure. After the horizontal inner support 13 is cut, place square wooden blocks 56 on the floor slab 16 of the main structure, slowly release the wire rope 54, and lower the horizontal inner support 13 as a whole onto the square wooden blocks 56. Finally, remove the reaction frame 34 and the steel support 35, and cut the horizontal inner support 13 into sections and transport it away.

[0047] Example 2

[0048] As another embodiment, this embodiment two proposes a more specific construction method for deep foundation pit reinforced concrete internal support based on embodiment one.

[0049] In step two, the inclined water collection plate 23 is provided with multiple inclined plastic strips, which are inclined outwards. The connecting steel bars 21 pass through the plastic strips, and the inclined water collection plate 23 is wrapped with geotextile 23.

[0050] The upper and lower ends of the inclined water collection plate 23 are located on the outer side of the waterproof felt 25, respectively.

[0051] An arc-shaped pad 55 is provided between the steel supports 35.

[0052] The two U-shaped ends 31 are temporarily fixed with positioning steel bars 33, and the positioning steel bars 33 are spot welded to the U-shaped ends 31.

[0053] The U-shaped end 31 is provided with a pre-embedded bolt sleeve 32, and the fastening bolt 36 is screwed into the pre-embedded bolt sleeve 32.

[0054] The horizontal water collection pipe 22 is a porous plastic pipe.

[0055] In step four, the inner side of the steel sleeve 51 is provided with a stud 52.

[0056] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiment 1 can be referred to each other, and will not be repeated in this application.

[0057] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

Claims

1. A construction method of a deep foundation pit reinforced concrete inner support, characterized by, The construction steps include: Step one, construction of the outer supporting structure of the foundation pit and excavation of the foundation pit: construct the underground continuous wall along the outside of the foundation pit excavation line, and then excavate the foundation pit soil; Step two, construction of the inner supporting structure of the foundation pit: construct the horizontal ring beam and the horizontal inner support to form the inner supporting structure of the foundation pit; the horizontal ring beam is connected with the vertical drainage pipe; When the horizontal inner support is crossed by the main structure column, the horizontal inner support is disconnected at the intersection of the horizontal inner support and the main structure column, and a U-shaped end head is arranged at the two end heads, then a horizontal support side formwork is arranged along the side of the U-shaped end head, and the concrete of the horizontal inner support is poured; after the concrete of the horizontal inner support reaches the design strength, the horizontal support side formwork is removed, and then the counterforce frame and the steel support are installed and fixed on the two U-shaped end heads by using the fastening bolts; the arc-shaped pads are arranged between the steel supports, and the two U-shaped end heads are temporarily fixed by using the positioning steel bars which are spot-welded with the U-shaped end heads; The U-shaped end head is provided with a pre-buried bolt sleeve, and the fastening bolt is screwed into the pre-buried bolt sleeve; Step three, repeat step one and step two until the foundation pit is excavated to the design depth, and then excavate the water collecting ditch at the bottom of the foundation pit, and connect the vertical drainage pipe to the water collecting ditch; Step four, construction of the main structure: construct the main structure side wall, the main structure column and the main structure floor in the foundation pit layer by layer from bottom to top, and inject waterproof mortar at the contact interface between the main structure side wall and the inner supporting structure of the foundation pit; the steel sleeve is integrally poured on the main structure column; Step five, removal of the inner supporting structure of the foundation pit: weld the steel corbel on the steel sleeve, then connect the horizontal inner support and the steel corbel by using the steel wire rope, cut the horizontal inner support along the main structure side wall, release the steel wire rope, and then integrally lower the horizontal inner support, finally remove the counterforce frame and the steel support, and cut and transport the horizontal inner support in sections. In step two, the specific method for constructing the horizontal ring beam is as follows: implant the connecting steel bars into the underground continuous wall at the contact surface between the horizontal ring beam and the underground continuous wall, then bind the steel bars of the horizontal ring beam and set the formwork, then pour the concrete of the horizontal ring beam, and pour the connecting steel bars in the horizontal ring beam; when the horizontal ring beam is part of the main structure side wall, the horizontal water collecting pipe, the vertical drainage pipe and the inclined water collecting plate are arranged on the outside of the horizontal ring beam, the waterproof oil felt is laid on the surface of the underground continuous wall, and the steel mesh is arranged on the upper and lower surfaces of the horizontal ring beam; the inclined water collecting plate is provided with a plurality of inclined plastic strips, the plastic strips are inclined outward, the connecting steel bars pass through between the plastic strips, the inclined water collecting plate is wrapped with geotextile, and the horizontal water collecting pipe is a porous plastic pipe.

2. The construction method of the deep foundation pit reinforced concrete inner support according to claim 1, characterized in that, In step two, the upper and lower ends of the inclined water collecting plate are located on the outside of the waterproof oil felt.

3. The construction method of the deep foundation pit reinforced concrete inner support according to claim 2, characterized in that, ​ 4. The construction method of the deep foundation reinforced concrete inner support according to claim 1, characterized in that, In the fourth step, the main structure side wall, the main structure column and the main structure floor are constructed layer by layer from bottom to top in the foundation pit, the upper grouting pipe and the lower grouting pipe are arranged at the contact interface of the main structure side wall and the horizontal ring beam and the horizontal inner support, after the main structure side wall is formed by pouring, waterproof mortar is injected into the contact interface of the main structure side wall and the horizontal ring beam and the horizontal inner support through the upper grouting pipe and the lower grouting pipe; the main structure column passes through between the two U-shaped ends of the horizontal inner support and is integrally formed by pouring, a steel sleeve is arranged at the segment passing through the horizontal inner support as a side mold of the main structure column, and the steel sleeve is integrally poured on the main structure column; the inner side of the steel sleeve is provided with pegs.

5. The construction method of the deep foundation pit reinforced concrete inner support according to claim 4, characterized in that, The fifth step is specifically that a steel corbel is welded on the steel sleeve, one end of a steel wire rope is fixed on the steel support and the other end is fixed on the steel corbel, the steel wire rope is tightened to keep it in a taut state, then the horizontal inner support is cut along the main structure side wall, after the horizontal inner support is cut, a square cushion is placed on the main structure floor, the steel wire rope is released, the horizontal inner support is integrally lowered onto the square cushion, finally the counterforce frame and the steel support are removed, and the horizontal inner support is cut and transported away in sections.

6. A reinforced concrete internal support for a deep excavation, characterised in that, Obtained by the method of any one of claims 1 to 5.

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