Foundation pit fender post open construction method

Abstract

The invention relates to the field of foundation pit supporting, and discloses a foundation pit fender post open construction method which comprises the following steps: step 1, excavating a first foundation pit, preparing a plurality of steel casings, and embedding the lower ends of the plurality of steel casings into the bottom of the first foundation pit; secondly, an upper retaining wall is poured between the steel casings, and meanwhile the first foundation pit is backfilled; and thirdly, cast-in-place piles are poured in the first foundation pit, and a second foundation pit is excavated. The influence of an existing structure of a first foundation pit on a newly-built second foundation pit is reduced, and the construction difficulty is lowered.

Description

Technical Field

[0001] The invention relates to the field of foundation pit support, and in particular to a method for constructing foundation pit retaining piles. Background Art

[0002] In foundation pit engineering, due to environmental constraints, it is sometimes necessary to construct two overlapping foundation pits that cannot be excavated at the same time. It is necessary to excavate a first foundation pit first, and then backfill and excavate another second foundation pit after the structure in the first foundation pit is completed.

[0003] However, when backfilling and then excavating the second foundation pit, drilling piles may cause damage to the structure in the first foundation pit. For example, when the location is very limited, high construction accuracy is required and drilling piles are prone to deviation, which may lead to damage to the existing structure and loss of balance in the stability of the existing structure, which may easily lead to safety risks.

[0004] Therefore, a construction method is needed to reduce the impact of the existing structure of the first foundation pit on the newly built second foundation pit and reduce the construction difficulty. Summary of the invention

[0005] The present invention aims to provide a method for constructing foundation pit retaining piles, which can reduce the influence of the existing structure of the first foundation pit on the newly-built second foundation pit, reduce the construction difficulty, and avoid the influence of the newly-built structure in the first foundation pit when the second foundation pit is excavated or the retaining piles are constructed.

[0006] To achieve the above object, the present invention adopts the following technical solution: a construction method of foundation pit retaining piles, comprising the following steps:

[0007] Step 1: excavate a first foundation pit, prepare a plurality of steel casings, and embed the lower ends of the plurality of steel casings into the bottom of the first foundation pit;

[0008] Step 2: Cast the upper retaining wall between the steel casings and backfill the first foundation pit at the same time; construct the second retaining piles of the second foundation pit through positioning of the steel casing;

[0009] Step 3: Cast in-situ piles in the first foundation pit and excavate the second foundation pit.

[0010] The beneficial effects of this program are:

[0011] 1. In this scheme, after the construction of the first foundation pit is completed, in order to ensure the safety of the implemented structure, before backfilling the first foundation pit, the steel casing and the upper retaining wall (as the support of the second foundation pit) located in the first foundation pit are completed first, and then the first foundation pit is backfilled. Then piles are drilled through the steel casing, and retaining piles are directly installed in the steel casing. In this way, when the second foundation pit is constructed, the excavation of the second foundation pit or the installation of retaining piles will not affect the newly built structure in the first foundation pit.

[0012] 2. The retaining piles are positioned through steel casings to guide the subsequent drilling, making it difficult for the drilled piles to deviate, ensuring the verticality of the cast-in-place piles, making the force-bearing performance of the cast-in-place piles better, and reducing the difficulty of construction.

[0013] Furthermore, in step one, the support of the first foundation pit includes a first retaining pile. After the steel casing is positioned, a limiting device is installed, the limiting device is connected to the upper end of the steel casing, and the end of the limiting device is connected to the upper end of the first retaining pile.

[0014] Furthermore, the limiting device includes two steel sections arranged in parallel on both sides of the steel casing, the middle part of the steel section is respectively connected to both sides of the upper end of the steel casing, and the steel section is perpendicular to the side wall of the first foundation pit.

[0015] Further, in step 2, the first foundation pit includes an overlapping area and a non-overlapping area, and the step of backfilling the first foundation pit is:

[0016] 2.1 The top elevation of the upper retaining wall is lower than the top of the steel casing, and the overlapping area and the non-overlapping area are backfilled to the horizontal support design elevation of the second foundation pit; then, the second retaining piles of the second foundation pit are constructed;

[0017] 2.2 Excavate the second foundation pit to the design elevation of the horizontal support, construct the horizontal support, connect one end of the horizontal support to the top of the upper retaining wall, and connect the other end of the horizontal support to the second retaining pile.

[0018] Furthermore, in step 2.2, before constructing the horizontal support, the first retaining pile within the corresponding height range is removed.

[0019] Furthermore, in step 1, the steel section is a channel steel or an I-beam;

[0020] In step 2.1, the lower flange and web of the steel section are buried during backfilling.

[0021] Furthermore, the upper retaining wall in step 2.1 is constructed in layers, and the upper retaining wall includes several layers of steel meshes, and the steel meshes include an inner steel mesh and an outer steel mesh. The inner steel mesh is arranged horizontally, and two sides of the inner steel mesh are respectively connected to the steel casing, and the remaining two sides of the inner steel mesh are respectively connected to the outer steel mesh, and the outer steel mesh is arranged vertically.

[0022] Furthermore, in step three, the steps of excavating the second foundation pit are:

[0023] 3.1. Excavate the overlapping area to the bottom elevation of the first foundation pit;

[0024] 3.2. Dig out the cast-in-place piles and use the reverse method to construct the lower retaining wall between the cast-in-place piles

[0025] 3.3, excavate the part outside the overlapping area of ​​the second foundation pit. This step is in no particular order with step 3.1 and step 3.2;

[0026] 3.4. Remove the first retaining pile in the overlapping area.

[0027] Furthermore, before removing the first retaining pile in the overlapping area, the steel sections in the overlapping area and the non-overlapping area are cut, and the first retaining pile in the overlapping area and above the horizontal support is removed.

[0028] This solution also has the following effects:

[0029] 1. Steel reinforcement stage: connect the steel and the first support to complete the positioning of the steel; then, connect the steel and the upper end of the steel casing to complete the positioning of the upper end of the steel casing, so that the upper end of the steel casing is no longer in a cantilevered state, thereby avoiding overturning and displacement of the steel casing.

[0030] 2. Backfill stage: In the overlapping area, backfilling is not necessary, but in order to stabilize the steel casing and prevent it from tilting or deflecting during construction, it is necessary to symmetrically backfill the overlapping and non-overlapping areas at the same time, so that both sides of the steel casing are evenly stressed. As the amount of backfill increases, the embedded depth of the steel casing increases, and the possibility of tilting or deflection decreases;

[0031] While pouring the upper retaining wall, backfill to the top elevation of the upper retaining wall, then connect the horizontal support and the upper end of the upper retaining wall to complete the conversion of the force system of the steel casing and the upper retaining wall, so that when backfilling the soil in the overlapping area is excavated later, the horizontal support replaces the backfill soil in the overlapping area to support one side of the steel casing, thereby ensuring the stability of the steel casing and the upper retaining wall.

[0032] The upper retaining wall includes a steel mesh, from which an inner steel mesh and an outer steel mesh are separated, which are effectively connected with the steel casing through welding to bear force synergistically. The inner steel mesh and the outer steel bars are welded to the steel casing from different angles respectively to avoid the welding positions being concentrated in the same direction of the steel casing, thereby optimizing the force structure and ensuring the stability of the structure.

[0033] 4. Second foundation pit excavation stage: After backfilling the first foundation pit, the backfill soil limits the steel casing, and the steel section is no longer needed for fixation. Therefore, the part of the steel section located in the overlapping area is cut and recycled to avoid the shaking caused by breaking the first retaining pile in the overlapping area at a later time being transmitted to the steel casing.

[0034] In order to improve the structural stability and give full play to the supporting role of the first retaining piles in the overlapping area, in this plan, the second foundation pit is excavated in layers. Specifically, the overlapping area is excavated first, then the non-overlapping area is excavated, and finally the first retaining piles in the overlapping area are removed. The first retaining piles are used as temporary supports for the second foundation pit to separate the steel casing from the non-overlapping area of ​​the second foundation pit to prevent accidents such as deformation or overturning of the casing and control the impact range of the danger. In addition, when the casing overturns, the first retaining piles can support the casing to reduce casualties. The closer the distance between the casing and the first retaining piles, the better the supporting effect.

[0035] If the steel casing sinks during the excavation process, the remaining steel sections will produce tension on the steel casing to prevent it from sinking. Compared with concrete structures, steel sections have better tensile properties and can effectively provide tension for the steel sections and produce horizontal components on the steel casing to prevent it from overturning toward the inside of the second foundation pit. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the embodiment after the first foundation pit is excavated;

[0037] Figure 2 It is a schematic diagram of an embodiment after the steel casing and the steel section are constructed;

[0038] Figure 3 It is a schematic diagram of an embodiment after the first foundation pit is backfilled;

[0039] Figure 4 A schematic diagram of an embodiment after excavation of the overlapping area;

[0040] Figure 5 It is a schematic diagram of the embodiment after the second foundation pit is excavated;

[0041] Figure 6 A schematic diagram of the connection between the steel casing and the upper retaining wall steel mesh of the embodiment;

[0042] Figure 7 A schematic top view of a steel casing and a steel section of an embodiment;

[0043] Figure 8 Schematic diagram of the first foundation pit and the second foundation pit in an embodiment. DETAILED DESCRIPTION

[0044] The following is further described in detail through specific implementation methods:

[0045] The figure marks in the drawings of the specification include: steel casing 1, cast-in-place piles 2, second retaining piles 3, outer steel mesh 4, inner steel mesh 5, steel section 6, first foundation pit 7, second foundation pit 8, first retaining piles 9, backfill 10, new box culvert 11, horizontal support 12, overlapping area 13, non-overlapping area 14, upper retaining wall 15.

[0046] Example

[0047] The embodiment is basically as follows Figure 1-Figure 8 As shown: a method for constructing foundation pit retaining piles, there are a first foundation pit 7 and a second foundation pit 8 that overlap and cannot be excavated at the same time, and the position relationship diagram is as shown in Figure 8 As shown, the depth of the second foundation pit 8 is greater than that of the first foundation pit 7, and the following steps are included:

[0048] Step 1: Figure 1 As shown, the first foundation pit 7 is excavated, and the first support of the first foundation pit 7 is built: the first retaining pile 9, according to the design, a new box culvert 11 is built in the first foundation pit 7, and a plurality of steel casings 1 are prepared and arranged in a row, as shown in FIG. Figure 2 As shown, the lower end of the steel casing 1 is embedded in the bottom of the first foundation pit 7 to complete the positioning of the steel casing 1, and the upper end of the steel casing 1 is higher than the top of the first foundation pit 7; a limiting device is installed, and the limiting device includes two steel sections 6 arranged in parallel on both sides of the steel casing 1, and the steel sections 6 are all I-beams, such as Figure 7 As shown, the middle parts of the two steel sections 6 are welded to the two sides of the upper end of the steel casing 1 respectively, the two steel sections 6 are perpendicular to the side walls of the first foundation pit 7, and the ends are connected to the upper end of the first retaining pile 9 (retaining piles are usually not constructed individually by several piles, and retaining walls are required to be constructed between the piles to achieve the support effect, so the piles are not shown as circular piles in the figure). In this embodiment, the connection method of the concrete structure and the steel structure is: pre-embedded steel plates in the concrete structure, and the steel plates and steel structures are welded.

[0049] Step 2: The first foundation pit 7 includes an overlapping area 13 and a non-overlapping area 14. The steel casing 1 is arranged at the boundary of the overlapping area 13 and the non-overlapping area 14. The upper retaining wall 15 is cast between the steel casings 1. Figure 6 As shown, the upper figure is a top view, and the lower figure is a main view. The upper retaining wall 15 includes two layers of vertically arranged outer steel meshes 4 and a plurality of horizontally arranged inner steel meshes 5. The interlayer spacing of the inner steel meshes 5 is 25-35 cm. In this embodiment, the interlayer spacing is 30 cm. Two sides of the inner steel meshes 5 are respectively welded to the steel casing 1, and the remaining two sides of the inner steel meshes 5 are respectively welded to the two layers of outer steel meshes 4. Adjacent outer steel meshes 4 are tied and connected. The two layers of outer steel meshes 4 are respectively located on both sides of the steel casing 1 and welded to the steel casing 1.

[0050] At the same time, if Figure 3 As shown, the first foundation pit 7 is backfilled with backfill soil 10; the steps of backfilling the first foundation pit 7 are:

[0051] 2.1 The top elevation of the upper retaining wall 15 is lower than the top of the steel casing 1, and the overlapping area 13 and the non-overlapping area 14 are backfilled to the top elevation of the upper retaining wall 15; at the same time, the second retaining piles 3 of the second foundation pit 8 are constructed;

[0052] 2.2 Excavate the second foundation pit 8 to the height of the top of the upper retaining wall 15, remove the first retaining pile 9 at the corresponding position, and construct the horizontal support 12, which is an I-beam, so that the left end of the horizontal support 12 is connected to the top of the upper retaining wall 15, and the right end of the horizontal support 12 is connected to the second retaining pile 3;

[0053] 2.3 Backfill the non-overlapping area 14 to the height of the steel section 6, and bury the lower flange and web of the steel section 6 after backfilling.

[0054] Step 3: Drill a hole at the bottom of the steel casing 1 to below the bottom elevation of the second foundation pit 8, cast a cast-in-place pile 2 in the steel casing 1 in the first foundation pit 7, and excavate the second foundation pit 8. The steps of excavating the second foundation pit 8 are as follows:

[0055] 3.1. Excavate the overlapping area 13 to the bottom elevation of the first foundation pit 7;

[0056] 3.2, such as Figure 4 As shown, the lower part of the cast-in-place pile 2 is excavated, and the lower retaining wall is constructed between the cast-in-place piles 2 by reverse construction, and the upper end of the lower retaining wall and the bottom of the upper retaining wall 15 are connected;

[0057] 3.3, excavating the second foundation pit 8 outside the overlapping area 13, this step and step 3.1, step 3.2 are not in particular order;

[0058] 3.4, such as Figure 5 As shown, the steel sections 6 in the overlapping area 13 and the non-overlapping area 14 are cut, the first retaining piles 9 in the overlapping area 13 and above the horizontal support 12 are broken, and then the remaining first retaining piles 9 in the overlapping area 13 are broken. This step and step 3.3 are constructed synchronously and in layers.

[0059] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for constructing foundation pit retaining piles, characterized in that: The following steps are involved: Step 1: excavate a first foundation pit, prepare a plurality of steel casings, and embed the lower ends of the plurality of steel casings into the bottom of the first foundation pit; Step 2: Cast the upper retaining wall between the steel casings and backfill the first foundation pit at the same time; construct the second retaining piles of the second foundation pit through positioning of the steel casing; Step 3: Cast in-situ piles in the first foundation pit and excavate the second foundation pit.

2. A method for constructing foundation pit retaining piles according to claim 1, characterized in that: In step one, the support of the first foundation pit includes a first retaining pile. After the steel casing is positioned, a limiting device is installed. The limiting device is connected to the upper end of the steel casing, and the end of the limiting device is connected to the upper end of the first retaining pile.

3. A method for constructing foundation pit retaining piles according to claim 2, characterized in that: The limiting device comprises two steel sections which are arranged in parallel on both sides of the steel casing, the middle part of the steel sections are respectively connected to both sides of the upper end of the steel casing, and the steel sections are perpendicular to the side wall of the first foundation pit.

4. A method for constructing foundation pit retaining piles according to claim 3, characterized in that: In step 2, the first foundation pit includes an overlapping area and a non-overlapping area, and the steps of backfilling the first foundation pit are: 2.1 The top elevation of the upper retaining wall is lower than the top of the steel casing, and the overlapping area and the non-overlapping area are backfilled to the horizontal support design elevation of the second foundation pit; then, the second retaining piles of the second foundation pit are constructed; 2.2 Excavate the second foundation pit to the design elevation of the horizontal support, construct the horizontal support, connect one end of the horizontal support to the top of the upper retaining wall, and connect the other end of the horizontal support to the second retaining pile.

5. A method for constructing foundation pit retaining piles according to claim 4, characterized in that: In step 2.2, before constructing the horizontal support, remove the first retaining pile within the corresponding height range.

6. A method for constructing foundation pit retaining piles according to claim 5, characterized in that: In step 1, the steel is a channel steel or an I-beam; In step 2.1, the lower flange and web of the steel section are buried during backfilling.

7. A method for constructing foundation pit retaining piles according to claim 6, characterized in that: The upper retaining wall in step 2.1 is constructed in layers. The upper retaining wall includes several layers of steel meshes. The steel meshes include an inner steel mesh and an outer steel mesh. The inner steel mesh is arranged horizontally. Two sides of the inner steel mesh are respectively connected to the steel casing, and the remaining two sides of the inner steel mesh are respectively connected to the outer steel mesh. The outer steel mesh is arranged vertically.

8. The method for constructing foundation pit retaining piles according to claim 3 is characterized by: In step 3, the steps of excavating the second foundation pit are: 3.

1. Excavate the overlapping area to the bottom elevation of the first foundation pit; 3.

2. Dig out the cast-in-place piles and use the reverse method to construct the lower retaining wall between the cast-in-place piles; 3.3, excavate the part outside the overlapping area of ​​the second foundation pit. This step is in no particular order with step 3.1 and step 3.2; 3.

4. Remove the first retaining pile in the overlapping area.

9. A method for constructing foundation pit retaining piles according to claim 8, characterized in that: Before removing the first retaining pile in the overlapping area, cut the steel sections in the overlapping area and the non-overlapping area, and remove the first retaining pile in the overlapping area and above the horizontal support.

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