CN118911155A - Deep foundation pit supporting device and construction method - Google Patents

Abstract

The present invention relates to a deep foundation pit support device and a construction method, comprising outer cast-in-place piles, middle cast-in-place piles and inner cast-in-place piles which are arranged in sequence from the outside to the inside, the inner cast-in-place piles and the middle cast-in-place piles having the same height and less than the height of the outer cast-in-place piles, the outer cast-in-place piles are used to be arranged on the outside of the outermost wall of the underground structure, the inner cast-in-place piles are used to be arranged on the outside of the innermost wall of the underground structure, an oblique brace is arranged between the top crown beam of the outer cast-in-place pile and the top crown beam of the inner cast-in-place pile, a connecting beam is arranged between the inner cast-in-place pile and the top crown beam of the middle cast-in-place pile, the connecting beam extends to the outer cast-in-place pile and is fixed to the outer cast-in-place pile to form a triangular support structure, the support device of the present invention has good stability, and meets the support requirements of foundation pits with an excavation depth greater than 10 meters.

Description

A deep foundation pit support device and construction method

Technical Field

The invention relates to the technical field of construction engineering, and in particular to a deep foundation pit supporting device and a construction method.

Background Art

The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

With the development of urban modernization, more and more complex deep foundation pit projects are appearing in construction. Complex foundation pits are affected by factors such as residential buildings around the foundation pits, complex road pipelines, high water levels, and poor geological conditions. As a prerequisite for the smooth construction of the project, the stability, reliability, operability, and impact on the surrounding environment of the foundation pit support are particularly important.

Patent application CN111395353A discloses a foundation pit support device and a support method based on steel sheet piles combined with vertical diagonal braces, which are provided with steel sheet piles, support steel sheet piles and vertical diagonal braces. The above support device and support method have high construction speed, and the steel sheet piles and vertical diagonal braces can be turned over, saving construction costs. However, the above scheme is only applicable to support within a foundation pit depth of 10 meters. Since the support device only has steel sheet piles, support steel sheet piles and vertical diagonal braces, it lacks steel sheet pile internal braces and has an unstable structure. When the foundation pit depth is greater than 10 meters, the plane area of the foundation pit is too large to use steel sheet pile internal braces. The lengthening of the diagonal braces of the above support device causes instability and deformation, and the overall stability is insufficient. The reliability of the support device is poor, which affects the safety of the foundation pit support. In addition, the support steel sheet piles need to be buried inside the soil at the bottom of the foundation pit in the later stage, resulting in a waste of construction materials and an increase in construction costs.

Summary of the invention

In view of the shortcomings of the prior art, the purpose of the present invention is to provide a deep foundation pit support device and a construction method, which ensures the safe use of the foundation pit without using reinforced concrete internal supports, has good overall stability, meets the stable support requirements for foundation pits with excavation depths greater than 10 meters, and at the same time saves construction materials and reduces construction costs.

In order to achieve the above object, the present invention is implemented through the following technical solutions:

In the first aspect, an embodiment of the present invention provides a deep foundation pit support device, comprising outer cast-in-place piles, middle cast-in-place piles and inner cast-in-place piles arranged in sequence from the outside to the inside, the heights of the inner cast-in-place piles and the middle cast-in-place piles are the same and less than the height of the outer cast-in-place piles, the outer cast-in-place piles are used to be arranged on the outside of the outermost wall of the underground structure, the inner cast-in-place piles are used to be arranged on the outside of the innermost wall of the underground structure, an oblique brace is provided between the top crown beam of the outer cast-in-place pile and the top crown beam of the inner cast-in-place pile, a connecting beam is provided between the inner cast-in-place pile and the top crown beam of the middle cast-in-place pile, the connecting beam extends to the outer cast-in-place pile and is fixed to the outer cast-in-place pile to form a triangular support structure.

Optionally, the top crown beam of the outer cast-in-place pile is provided with an inclined iron, and the top crown beam of the inner cast-in-place pile is integrally cast with a support seat, one end of the inclined support is fixed to the inclined iron, and the other end is fixed to the support seat.

Optionally, one end of the oblique brace is welded and fixed to the oblique iron, and the other end is welded and fixed to the embedded part in the support seat.

Optionally, the oblique iron is welded and fixed to the embedded part in the crown beam at the top of the outer cast-in-place pile, and the oblique brace is welded and fixed to the embedded part in the support seat.

Optionally, the deep foundation pit supporting device further comprises a plurality of prestressed anchor cables, a set prestressed anchor cable passes through the inner cast-in-place pile and the middle cast-in-place pile, and the remaining prestressed anchor cables pass through the inner cast-in-place pile, the middle cast-in-place pile and the outer cast-in-place pile.

Optionally, the angle between the prestressed anchor cable and the horizontal plane is 55°-65°, preferably 60°.

Optionally, the diagonal braces are angle steel lattice columns.

In a second aspect, an embodiment of the present invention provides a construction method of the deep foundation pit supporting device according to the first aspect, comprising the following steps:

Construct outer cast-in-place piles, middle cast-in-place piles and inner cast-in-place piles, among which the outer cast-in-place piles are reserved for the steel bar structure fixed to the coupling beam;

Carry out earth excavation until the elevation of the inner cast-in-place pile is reached. During excavation, reserve counter-pressure soil above the middle cast-in-place pile and inside the outer cast-in-place pile;

Construct the crown beams on the top of the outer cast-in-place piles and the inner cast-in-place piles, and then install the diagonal braces between the outer cast-in-place piles and the inner cast-in-place piles;

After the installation of the diagonal brace is completed, the counter-pressure soil is excavated. After the counter-pressure soil is excavated, the crown beam and the connecting beam on the top of the middle cast-in-place pile are constructed simultaneously, and the connecting beam is cast as a whole with the outer cast-in-place pile and the inner cast-in-place pile;

Continue to excavate the foundation pit until the set target depth is reached.

Optionally, after the excavation of the counter-pressure soil is completed, rebar is planted at the connection position of the outer cast-in-place pile and the connecting beam and the inner cast-in-place pile crown beam, and then the steel structure of the middle cast-in-place pile crown beam and the steel structure of the connecting beam are tied and fixed, the steel structure of the connecting beam is tied and fixed to the steel structure of the middle cast-in-place pile crown beam, and then the concrete of the connecting beam and the middle cast-in-place pile crown beam is poured.

Optionally, when constructing the crown beam on the top of the inner cast-in-place pile, the support seat located on the top surface of the crown beam of the inner cast-in-place pile is constructed simultaneously. After the construction of the crown beam on the top of the outer cast-in-place pile is completed, the inclined iron is welded and fixed to the embedded parts of the crown beam on the top of the outer cast-in-place pile.

The beneficial effects of the present invention are as follows:

1. In the deep foundation pit support device of the present invention, connecting beams are arranged between the top crown beams of the inner cast-in-place piles, the top crown beams of the middle cast-in-place piles and the outer cast-in-place piles, and a stable triangular support structure is formed between the outer cast-in-place piles, the connecting beams and the diagonal braces. In addition, three cast-in-place piles are arranged, so that the support structure is more stable and has a stronger ability to withstand the lateral pressure of the soil, which meets the support requirements for foundation pits with an excavation depth greater than 10 meters and improves the applicability of the entire support device.

2. The deep foundation pit support device of the present invention adopts inner cast-in-place piles and middle cast-in-place piles. The inner cast-in-place piles and the middle cast-in-place piles can be used as engineering piles of underground structures at the same time, thereby realizing the secondary utilization of the inner cast-in-place piles and the outer cast-in-place piles, avoiding the waste of construction materials, reducing the construction of underground structure engineering piles, shortening the construction period, and reducing the construction cost.

3. The deep foundation pit support device of the present invention is provided with prestressed anchor cables, which are combined with the triangular support structure formed by the outer cast-in-place piles, connecting beams and diagonal braces, which greatly enhances the reliability of the support device and meets the support needs of foundation pits with an excavation depth greater than 10 meters.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

FIG1 is a schematic diagram of the overall structure of Embodiment 1 of the present invention;

Among them, 1. Inner cast-in-place piles, 2. Crown beams, 3. Outer cast-in-place piles, 4. Support seats, 5. Diagonal braces, 6. Counterpressure soil, 7. Connecting beams, 8. The first prestressed anchor cable, 9. Waist beams, 10. The innermost wall of the basement, 11. Inclined irons, 12. Middle cast-in-place piles, 13. The outermost wall of the basement, and 14. The second prestressed anchor cable.

DETAILED DESCRIPTION

Example 1

The present embodiment provides a deep foundation pit supporting device, as shown in FIG1 , comprising a plurality of outer cast-in-place piles 3 arranged along the edge of the foundation pit, wherein the inner side of the outer cast-in-place piles 3 is provided with middle cast-in-place piles 12 parallel thereto, and the inner side of the middle cast-in-place piles 12 is provided with inner cast-in-place piles 1 parallel thereto, wherein the height of the middle cast-in-place piles 12 is the same as that of the inner cast-in-place piles 1 and is smaller than that of the outer cast-in-place piles 3, and the bottom surfaces of the outer cast-in-place piles 3, the middle cast-in-place piles 12 and the inner cast-in-place piles 1 are flush and located at the same height.

The outer cast-in-place piles 3 are used to be arranged on the outer side of the outermost wall 13 of the underground structure, and the inner cast-in-place piles 1 are used to be arranged on the outer side of the innermost wall 10 of the underground structure.

The outer cast-in-place pile 3 has a crown beam 2 on its top, which is the outer cast-in-place pile crown beam; the middle cast-in-place pile 12 has a crown beam 2 on its top, which is the middle cast-in-place pile crown beam; the inner cast-in-place pile 1 has a crown beam 2 on its top, which is the inner cast-in-place pile crown beam.

The side of the outer cast-in-place pile crown beam is provided with an inclined iron 11, and the top surface of the inner cast-in-place pile crown beam is provided with a support seat 4. The corresponding outer cast-in-place pile 3 and the inner cast-in-place pile 1 are provided with an inclined support 5 between the inclined iron 11 and the support seat 4 to resist the soil pressure of the outer cast-in-place pile.

In this embodiment, the diagonal brace 5 adopts the existing angle steel lattice column, which is welded by multiple Q235 gusset plates and angle steels. The existing structure can be used, and its specific structure will not be described in detail here.

The size of the angle steel lattice column can be calculated and determined according to the actual needs of the project. It will not be described in detail here. The angle steel lattice column is processed in an off-site factory and then directly transported to the construction site for use.

The inclined iron 11 is welded and fixed to the embedded parts in the outer cast-in-place pile crown beam, and has an inclined surface for welding with the angle steel lattice column, so as to better transfer the soil pressure on the outer cast-in-place pile to the angle steel lattice column. The support seat 4 adopts a concrete structure, which is cast integrally with the inner cast-in-place pile crown beam. Embedded parts are embedded inside the support seat 4. The support seat 4 is provided with an inclined surface that fits with the end of the angle steel lattice column and is welded and fixed to the angle steel lattice column through the embedded parts.

A connecting beam 7 is also arranged between the inner cast-in-place pile crown beam and the middle cast-in-place pile crown beam. The connecting beam 7 is perpendicular to the inner cast-in-place pile 1 and the middle cast-in-place pile 12. One end of the connecting beam is connected to the inner cast-in-place pile crown beam, and the other end is connected to the outer cast-in-place pile 3. The outer cast-in-place pile 3, the connecting beam 7 and the diagonal brace 5 form a stable triangular support structure. At the same time, three cast-in-place piles are arranged to stabilize the force on the top of the inner cast-in-place pile 1, so that the support structure is more stable and has a stronger ability to withstand the lateral pressure of the soil, which meets the support requirements of foundation pits with an excavation depth greater than 10 meters and improves the applicability of the entire support device.

The supporting device of this embodiment also includes two prestressed anchor cables, namely the first prestressed anchor cable and the second prestressed anchor cable. The two prestressed anchor cables are arranged in parallel, and the angle between them and the horizontal plane is 55°-65°, preferably 60°. The first prestressed anchor cable 8 on the top passes through the inner cast-in-place pile crown beam, the inner cast-in-place pile 1, the middle cast-in-place pile 12 and the outer cast-in-place pile 3 in sequence, and the second prestressed anchor cable 14 on the bottom passes through the inner waist beam 9 of the inner cast-in-place pile, the inner cast-in-place pile 1, and the middle cast-in-place pile 12 in sequence.

By setting prestressed anchor cables, tensile stress is applied to the inner bored pile 1, thereby further improving the bearing capacity of the inner bored pile. The support device of this embodiment, through the setting of prestressed anchor cables, is combined with the triangular support structure formed between the outer bored pile 3, the connecting beam 7 and the diagonal brace 5, which greatly enhances the reliability of the support device and meets the support requirements for foundation pits with an excavation depth greater than 10 meters. The support device of this embodiment can reliably support foundation pits with a depth of up to 17 meters.

The supporting device of this embodiment adopts inner cast-in-place piles 1 and middle cast-in-place piles 12. Compared with the traditional steel sheet piles, the inner cast-in-place piles 1 and the middle cast-in-place piles 12 can be used as engineering piles of underground structures at the same time, realizing the secondary utilization of the inner cast-in-place piles and the outer cast-in-place piles, avoiding the waste of construction materials, reducing the construction of underground structure engineering piles, shortening the construction period, and reducing the construction cost.

Example 2

This embodiment provides a construction method of the deep foundation pit support device described in Embodiment 1, comprising the following steps:

Step 1: Level the site. Use mechanical equipment to level the site according to the site conditions. This step can be done using existing technology and will not be described in detail here.

Step 2: construct the outer cast-in-place pile 3, the middle cast-in-place pile 12 and the inner cast-in-place pile 1.

The construction method of the outer cast-in-place pile 3, the middle cast-in-place pile 12 and the inner cast-in-place pile 1 can adopt the existing technology, according to the construction process of surveying and setting out → casing burying → drilling rig positioning → mud preparation → drilling hole → final hole cleaning → steel cage production and hoisting → guide tube installation, secondary hole cleaning → pouring underwater concrete. Each process is strictly constructed according to the requirements to speed up the construction progress while ensuring the quality of the pile. The construction method of this step adopts the existing technology and will not be described in detail here. The position of the outer cast-in-place pile 3 does not cross the red line of the land.

Step 3: Excavate the earth until the elevation of the middle cast-in-place pile 12 and the inner cast-in-place pile 1 is reached.

The excavation method can adopt the existing construction method, which will not be described in detail here. During excavation, counter-pressure soil 6 is reserved for the space above the middle cast-in-place pile 12 and inside the outer cast-in-place pile 3. The slope of the counter-pressure soil 6 is 1:1, that is, the slope of the counter-pressure soil toward the side of the foundation pit is 45°.

Preferably, the excavation of the earthwork is carried out in a layered manner until the elevation of the middle cast-in-place piles and the inner cast-in-place piles 12 is reached, that is, the bottom surface of the excavated foundation pit is flush with the top surfaces of the middle cast-in-place piles 12 and the inner cast-in-place piles 1.

Step 4: Construct the first anchor cable. The construction method of the first anchor cable can adopt existing technology. The first anchor cable is constructed at the crown beam position of the inner cast-in-place pile. The first anchor cable passes through the inner cast-in-place pile 1, the middle cast-in-place pile 12 and the outer cast-in-place pile 3. The horizontal and vertical angles between the drill rod and the soil are strictly controlled. The anchor cable and the anchor rod are drilled together for construction. After the construction of the high-pressure rotary jet machine is completed, the drill rod is withdrawn and the prestressed anchor cable is retained. The construction method of the first anchor cable can adopt existing technology and will not be described in detail here.

Step 5: Construct the inner cast-in-place pile cap beam and the outer cast-in-place pile cap beam.

Both the inner cast-in-place pile crown beam and the outer cast-in-place pile crown beam are made of reinforced concrete structure, and the construction method can adopt existing technology. When constructing the outer cast-in-place pile crown beam, embedded parts are reserved inside the outer cast-in-place pile crown beam to facilitate welding and fixing with the inclined iron 11. After the construction of the outer cast-in-place pile crown beam is completed, the inclined iron 11 is welded. When constructing the inner cast-in-place pile crown beam, the support seat 4 is cast simultaneously, and embedded parts for welding with the inclined support 5 are embedded in the support seat 4. After the inner cast-in-place pile crown beam reaches the set strength, the first anchor cable is tensioned and fixed to form the first prestressed anchor cable 8. The tensioning and fixing construction method can adopt the existing method, which will not be described in detail here.

Step 6: After the inner cast-in-place pile crown beam and the outer cast-in-place pile crown beam have reached the set strength, one end of the diagonal brace 5 is welded and fixed to the diagonal iron 11 , and the other end of the diagonal brace 5 is welded and fixed to the embedded part in the support seat 4 .

Step 7: excavate the counter-pressure soil 6 to remove the counter-pressure soil 6.

Step 8: After the excavation of the counter-pressure soil 6 is completed, the part of the outer cast-in-place pile 3 used to connect the connecting beam is rebar-planted. After the rebar-planting is completed, the steel structure of the middle cast-in-place pile crown beam and the connecting beam 7 is constructed, and the steel structure of the connecting beam 7 is tied and fixed with the steel structure of the middle cast-in-place pile crown beam and the steel bars implanted in the inner cast-in-place pile crown beam and the outer cast-in-place pile 3, and then the middle cast-in-place pile crown beam and the connecting beam 7 are simultaneously poured with concrete.

Step 9: Continue to excavate the foundation pit. After excavating to the set depth, construct the second anchor cable. The second anchor cable passes through the inner cast-in-place pile 1 and the middle cast-in-place pile 12. The construction method is the same as the construction method of the first anchor cable, which will not be described in detail here. Then, construct the inner cast-in-place pile waist beam 9 at the position of the second anchor cable. The construction method can be based on the existing technology. After the construction is completed, when the inner cast-in-place pile waist beam 9 reaches the set strength, the second anchor cable is tensioned and fixed to form the second prestressed anchor cable 14.

Step 10: Continue excavating until the excavation reaches the set target depth.

After the foundation pit construction is completed, the underground structure construction begins. First, the underground structure part inside the inner cast-in-place pile is constructed. After the construction is completed, backfill is carried out. After backfilling to the elevation of the inner cast-in-place pile 1 and the middle cast-in-place pile 12, the two ends of the diagonal brace 5 are cut and the diagonal brace 5 is removed. During the removal process, ensure that the backfill strength of the backfill part reaches the set strength.

At this time, the inner cast-in-place piles 1 and the middle cast-in-place piles 12 are converted into engineering piles for use, and the underground structure above them is continued to be constructed. The inner cast-in-place piles 1 and the middle cast-in-place piles 12 are connected to the raft foundation steel bars and concrete is poured together to achieve permanent use of the temporary structure.

After all parts of the underground structure are constructed, the foundation pit is backfilled until the backfill is complete.

In the construction method of this embodiment, the inner cast-in-place pile 1 and the middle cast-in-place pile 12 can be used as engineering piles of the underground structure at the same time, thereby realizing the secondary utilization of the inner cast-in-place pile and the outer cast-in-place pile, avoiding the waste of materials, reducing the construction of engineering piles of the underground structure, shortening the construction period, and reducing the construction cost.

The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. The utility model provides a deep foundation pit supporting device, its characterized in that, including outside bored concrete pile, middle bored concrete pile and the inboard bored concrete pile that sets gradually from outside to inside, the height of inboard bored concrete pile and middle bored concrete pile is the same and is less than the height of outside bored concrete pile, and outside bored concrete pile is used for setting up in the underground structure outside wall body outside of the most inboard wall body outside, and inboard bored concrete pile is used for setting up in the underground structure outside, is equipped with the bracing between outside bored concrete pile top crown roof beam and the inboard bored concrete pile top crown beam, be equipped with between inboard bored concrete pile and the middle bored concrete pile top crown beam and link the roof beam, link the roof beam to extend to outside bored concrete pile and fix with outside bored concrete pile in order to form triangle-shaped bearing structure.

2. The deep foundation pit supporting device according to claim 1, wherein the top crown beam of the outer cast-in-place pile is provided with a diagonal iron, the top crown beam of the inner cast-in-place pile is integrally cast with a supporting seat, one end of the diagonal iron is fixed with the diagonal iron, and the other end of the diagonal iron is fixed with the supporting seat.

3. The deep foundation pit supporting device according to claim 2, wherein one end of the diagonal brace is welded and fixed with the diagonal iron, and the other end of the diagonal brace is welded and fixed with an embedded part in the supporting seat.

4. The deep foundation pit supporting device according to claim 1, wherein the diagonal members are welded and fixed with embedded parts in the crown beams at the top of the outer cast-in-place pile, and the diagonal members are welded and fixed with embedded parts in the supporting seat.

5. The deep foundation pit supporting device according to claim 1, further comprising a plurality of pre-stressed anchor cables, wherein the pre-stressed anchor cables are arranged to pass through the inner cast-in-place pile and the middle cast-in-place pile, and the rest of the pre-stressed anchor cables pass through the inner cast-in-place pile, the middle cast-in-place pile and the outer cast-in-place pile.

6. A deep pit support according to claim 5, wherein the angle of the pre-stressed anchor cable to the horizontal is 55 ° -65 °, preferably 60 °.

7. The deep foundation pit supporting device of claim 1, wherein said diagonal braces are angle steel lattice columns.

8. A method of constructing a deep foundation pit support assembly as claimed in any one of claims 1 to 7, comprising the steps of:

Constructing an outer side filling pile, a middle filling pile and an inner side filling pile;

Performing earth excavation until the elevation of the middle filling pile and the elevation of the inner filling pile are excavated, and reserving back pressure soil in the inner space of the outer filling pile above the middle filling pile during excavation;

Constructing crown beams at the tops of the outer filling pile and the inner filling pile, and then installing diagonal braces between the crown beams at the tops of the outer filling pile and the inner filling pile;

After the diagonal bracing is installed, excavating back pressure soil, and after the back pressure soil is excavated, synchronously constructing a crown beam and a connecting beam at the top of the middle filling pile, and casting the connecting beam, the outer filling pile and the inner filling pile into a whole;

And excavating the foundation pit continuously until the foundation pit is excavated to the set target depth.

9. The construction method of the deep foundation pit supporting device according to claim 8, wherein after the back pressure soil excavation is completed, the steel bar structure of the middle cast-in-place pile crown beam and the steel bar structure of the connecting beam are bound and fixed at the connection position of the outer cast-in-place pile and the connecting beam and the inner cast-in-place pile crown beam, the steel bar structure of the connecting beam and the steel bar structure of the middle cast-in-place pile crown beam are bound and fixed, the steel bar structure of the connecting beam and the steel bars implanted in the outer cast-in-place pile and the inner cast-in-place pile crown beam are bound and fixed, and then the concrete pouring of the connecting beam and the middle cast-in-place pile crown beam is carried out.

10. The construction method of deep foundation pit supporting device according to claim 8, wherein when the top crown beam of the inner side filling pile is constructed, the supporting seat positioned on the top surface of the top crown beam of the inner side filling pile is synchronously constructed, and after the construction of the top crown beam of the outer side filling pile is completed, the oblique iron and the embedded part of the top crown beam of the outer side filling pile are welded and fixed.