Construction method of prestressed pipe pile group near deep foundation pit engineering

Abstract

The present application relates to a kind of prestressed pipe pile group construction method of adjacent deep foundation pit engineering, comprising the following steps: at least one stress release hole being constructed in the second foundation pit needing to carry out prestressed pipe pile group construction and being separated between prestressed pipe pile group construction area and adjacent first foundation pit;A anti-extrusion ditch is constructed in the second foundation pit and is separated between the stress release hole and the first foundation pit;The construction of each prestressed pipe pile is carried out in the order of 1 to m for prestressed pipe pile group distributed in m × n (m is row number, n is column number) matrix, wherein the first row is relatively close to the first foundation pit, and the mth row is relatively far away from the first foundation pit.The method can greatly reduce the influence of prestressed pipe pile on adjacent existing or under-construction structures during pile sinking process, and meet the construction requirements of adjacent deep foundation pit engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of foundation pit construction, in particular to a prestressed pipe pile group construction method near a deep foundation pit project. BACKGROUND

[0002] Since the prestressed pipe pile (including PC pipe pile, PHC pipe pile and PTC pipe pile, etc.) has fast construction speed and low requirement on construction site, its application is more and more widely used. However, in the process of pile sinking, the surrounding soil is extruded by the pile body, which causes the rise of pore water pressure in a short time, and makes the soil heave and extrude laterally. It is easy to affect the nearby existing or under-construction buildings, roads and the like. At present, for the occasions where the distance is too close, the prestressed pipe pile is usually adjusted to a cast-in-place pile to change the pile type to solve the above problems. However, as is known to all, the construction of the cast-in-place pile is more complicated than that of the prestressed pile, the construction progress is slow, and the construction site has high requirement. SUMMARY

[0003] In order to solve the above problems, the present application provides a prestressed pipe pile group construction method near a deep foundation pit project, which can greatly reduce the influence of the prestressed pipe pile on the nearby existing or under-construction buildings in the process of pile sinking, and meet the construction requirements of the deep foundation pit project.

[0004] The present application is realized by the following scheme: a prestressed pipe pile group construction method near a deep foundation pit project, comprising the steps of:

[0005] constructing at least one stress release hole in a second foundation pit in which the prestressed pipe pile group construction is needed, and which is separated between the prestressed pipe pile group construction area and a nearby first foundation pit;

[0006] constructing a prevention extrusion ditch in the second foundation pit, which is separated between the stress release hole and the first foundation pit;

[0007] constructing each prestressed pipe pile in order from 1 to m in columns for the prestressed pipe pile group distributed in an m*n (m is the number of rows, and n is the number of columns) matrix, wherein the first row is relatively close to the first foundation pit, and the mth row is relatively far away from the first foundation pit.

[0008] The prestressed pipe pile group construction method near a deep foundation pit project of the present application is further improved in that after each stress release hole is constructed, a plastic pipe is placed in the stress release hole in time, and sand is backfilled in the gap around the plastic pipe.

[0009] The prestressed pipe pile group construction method near a deep foundation pit project of the present application is further improved in that the diameter of the plastic pipe is not less than one third of the diameter of the stress release hole and not more than one half of the diameter of the stress release hole.

[0010] The further improvement of the prestressed pipe pile group construction method for the deep foundation pit engineering is that the depth of the stress release hole is not less than the design depth of the pile hole of the prestressed pipe pile when the stress release hole is constructed.

[0011] The further improvement of the prestressed pipe pile group construction method for the deep foundation pit engineering is that the stress release hole is constructed in the second foundation pit and is arranged between the prestressed pipe pile group construction area and the first foundation pit.

[0012] The further improvement of the prestressed pipe pile group construction method for the deep foundation pit engineering is that the stress release hole is constructed in the second foundation pit and is arranged between the prestressed pipe pile group construction area and the first foundation pit.

[0013] The prestressed pipe pile group construction method for the deep foundation pit engineering provided by the application can greatly reduce the influence of the prestressed pipe pile on the adjacent existing or under-construction buildings and roads during the pile sinking process, meet the construction requirements of the deep foundation pit engineering, and is more economical and has higher construction efficiency than the traditional measures of directly replacing the prestressed pipe pile with a cast-in-place pile or changing the pile type. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The flow chart of the prestressed pipe pile group construction method is shown.

[0015] Figure 2 The plan position schematic diagram of the prestressed pipe pile group construction area, the stress release hole and the anti-extrusion trench is shown.

[0016] Figure 3 The traditional prestressed pipe pile group construction sequence diagram is shown. DETAILED DESCRIPTION

[0017] In order to reduce the influence of the prestressed pipe pile on the adjacent existing or under-construction buildings, roads and the like during the pile sinking process, the application provides a prestressed pipe pile group construction method for the deep foundation pit engineering. The prestressed pipe pile group construction method for the deep foundation pit engineering is further described below in combination with the drawings.

[0018] Referring to Figure 1 and Figure 2 , Figure 1 The flow chart of the prestressed pipe pile group construction method is shown, Figure 2This invention illustrates a schematic diagram of the planar location of the prestressed concrete pipe pile group construction area, stress relief holes, and anti-crushing trenches. The first foundation pit 1 has only completed its foundation slab construction and is currently still in the underground structure construction stage. The curtain wall of the second foundation pit 2 is in the prestressed concrete pipe pile construction stage. The net distance d between the second foundation pit 2 and the diaphragm wall of the first foundation pit 1 is only 15 meters. Based on the above construction background, this invention provides a prestressed concrete pipe pile group construction method for near-deep foundation pit projects, including the following steps:

[0019] Step 1: Construct at least one row of stress relief holes 3 in the second foundation pit 2 where prestressed pipe pile group construction is required, between the prestressed pipe pile group construction area and the adjacent first foundation pit 1.

[0020] Specifically, this embodiment sets up two rows of stress relief holes 3, with multiple φ300 stress relief holes 3 spaced apart along the critical line direction of the second foundation pit 2 in each row. The spacing between adjacent stress relief holes 3 is 1.0m, and the row spacing is 0.8m, arranged in a staggered pattern to ensure that the stress relief holes 3 meet the anti-soil displacement requirements of this project. Preferably, the depth of the stress relief hole 3 should not be less than the design depth of the prestressed concrete pipe pile hole, and preferably equal to the design depth of the pile hole, to avoid unnecessary waste of construction costs. In this project, the main building pile foundation is 33 meters deep. Including the pile driving depth, the design depth of the prestressed concrete pipe pile hole is approximately 38 meters. Therefore, the depth of the stress relief hole 3 in this embodiment is set to 38 meters. Preferably, after each stress relief hole 3 is constructed, a plastic pipe is promptly installed through the stress relief hole 3, and yellow sand is backfilled in the gaps around the plastic pipe to prevent the hole from collapsing and affecting the stress relief effect. The diameter of the plastic tube is not less than one-third and not more than half the diameter of the stress relief hole. In this embodiment, the diameter of the plastic tube is set to φ100. Through the comprehensive design of matching the diameter of the plastic tube with the stress relief hole 3 and filling the gap with yellow sand, the collapse of the hole is prevented and a better stress relief effect is ensured.

[0021] Step 2: Construct an anti-squeezing trench 4 within the second foundation pit 2, between the stress relief hole 3 and the first foundation pit 1.

[0022] Specifically, the anti-squeezing trench 4 is 1.5 meters wide and 2.5 meters deep, and is set along the critical line of the second foundation pit 2 to further reduce the impact of the prestressed pipe piles on the adjacent first foundation pit 1 during the pile driving process.

[0023] Step 3: For the prestressed pipe pile group distributed in an m×n matrix (m is the number of rows and n is the number of columns), construct each prestressed pipe pile in order from 1 to m. The first row is relatively close to the first foundation pit 1, and the m-th row is relatively far away from the first foundation pit 1.

[0024] Specifically, refer to Figure 3 , Figure 3 The construction sequence diagram of the traditional prestressed pipe pile group is shown. Taking 4 rows x 5 columns as an example, the construction sequence of the traditional prestressed pipe pile group is single-row east-west sequential construction, that is, single-row construction in the order of the first row (the row close to the first foundation pit 1) to the fourth row (the row away from the first foundation pit 1). This construction sequence will continuously increase the lateral pressure of the support maintenance structure of the first foundation pit 1, causing the first foundation pit 1 to have large stress deformation at a certain period, increasing the safety risk. In combination with the shown, the construction sequence of the traditional prestressed pipe pile group is adjusted to column-by-column construction from north to south, that is, the first column is constructed first in the direction of the first row to the fourth row, and then the second column to the fourth column is constructed in turn. The order of the columns is not limited to this, for example, the fourth column to the first column, or the order of every other column, but when each column is constructed, it should be ensured that the order from close to the first foundation pit 1 to away from the first foundation pit 1 is followed to avoid continuous impact on the first foundation pit 1. Figure 2

[0025] The present application reduces the influence of the prestressed pipe pile on the adjacent existing or under-construction structures during the pile sinking process to a great extent, meets the construction requirements of the adjacent deep foundation pit project, and is more economical and has higher construction efficiency compared to the traditional measures of changing the pile type by directly replacing the prestressed pipe pile with a cast-in-place pile.

[0026] The above embodiments of the present application are described in detail in combination with the drawings, and those of ordinary skill in the art can make various changes to the present application according to the above description. Therefore, some details in the embodiments should not constitute a limitation on the present application, and the scope of protection of the present application will be defined by the appended claims.​

Claims

1. A construction method for a group of prestressed pipe piles near a deep foundation pit, characterized in that, Including the following steps: Construct at least one row of stress relief holes in the second foundation pit where prestressed pipe pile group construction is required, between the prestressed pipe pile group construction area and the adjacent first foundation pit. Construct an anti-squeezing trench within the second foundation pit, separating the stress relief hole from the first foundation pit; For a group of prestressed pipe piles distributed in an m×n matrix, each prestressed pipe pile is constructed in sequence from 1 to m, where m is the number of rows and n is the number of columns. The first row is relatively close to the first foundation pit, and the m-th row is relatively far away from the first foundation pit.

2. The construction method of prestressed pipe pile group for near-deep foundation pit engineering as described in claim 1, characterized in that, After each stress relief hole is constructed, a plastic pipe is promptly inserted into the stress relief hole, and sand is backfilled into the gaps around the plastic pipe.

3. The construction method of prestressed pipe pile group for near-deep foundation pit engineering as described in claim 2, characterized in that, The diameter of the plastic tube is not less than one-third and not greater than one-half of the diameter of the stress relief hole.

4. The construction method for prestressed pipe pile groups in near-deep foundation pit engineering as described in claim 1, characterized in that, When constructing the stress relief hole, the depth of the stress relief hole shall not be less than the design depth of the prestressed pipe pile hole.

5. The construction method for prestressed pipe pile groups in near-deep foundation pit engineering as described in claim 1, characterized in that, Two rows of stress relief holes were constructed in the second foundation pit, separating the prestressed pipe pile group construction area from the first foundation pit.

6. The construction method of prestressed pipe pile group for near-deep foundation pit engineering as described in claim 5, characterized in that, The stress relief holes are constructed in a plum blossom pattern.

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