A structure and construction method for a support and waterproof curtain that penetrates an old foundation slab obstacle.

Abstract

This invention relates to a structure and construction method for a support and cutoff wall that penetrates an existing basement slab obstacle, including a basement slab obstacle, cement-mixed interlocking piles, cast-in-place piles, and high-pressure jet grouting piles. This invention employs a "cement mixing – existing basement slab obstacle – high-pressure jet grouting" method to form a deep-mixed jet grouting cutoff wall complex. This solves the problem that conventional deep foundation pit support and cutoff wall construction methods cannot penetrate thick existing basement slab obstacles, and also addresses the issue of densely packed old buildings surrounding the construction area, making direct high-pressure jet grouting pile construction unsuitable. It adapts to complex site terrain conditions.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a structure and construction method for a support and waterproof curtain that passes through an old foundation slab obstacle. Background Technology

[0002] With rapid economic development, urban renewal projects in densely built-up areas are becoming increasingly common. The construction of deep foundation pit support structures in these projects often encounters old basement slabs with a thickness of 1-2 meters. Conventional construction techniques struggle to directly penetrate these slabs to form cast-in-place piles, and it's also impossible to directly use high-pressure jet grouting or mixing pile machines to create a water-stop curtain. Furthermore, due to the historical practice of extensive construction by demolition teams, after the main components such as the basement roof and intermediate floor slabs are removed, backfilling with miscellaneous soil quickly creates a thick layer of loose fill, making it difficult to form a mud-slurry retaining wall on the upper part of the old basement slab. The thick old slab also makes it easy for a confined water layer to form beneath it, further hindering the formation of a mud-slurry retaining wall. Additionally, these demolition projects are often surrounded by densely packed old buildings. If high-pressure jet grouting is used on the upper part during the construction of the deep foundation pit support structure, the resulting soil compression can affect the foundations of surrounding old buildings.

[0003] The aforementioned unique underground conditions are unfavorable for the construction of new deep foundation pit bored pile support structures, as well as for the construction of new deep foundation pit water-stop curtains. Therefore, it is necessary to propose a structure and construction method for the support and water-stop curtain to penetrate the old foundation slab obstacle, to complete the construction using existing construction techniques, and to meet the requirements of deep foundation pit protection and water-stopping. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to overcome the shortcomings and deficiencies in the prior art and to provide a structure and construction method for a support and water-stop curtain that passes through an old foundation slab obstacle.

[0005] A structure for supporting and sealing a water-stop curtain through an old basement slab obstacle includes an old basement slab obstacle, cement-mixed interlocking piles, cast-in-place piles, and several high-pressure jet grouting piles.

[0006] The cement mixing interlocking piles are arranged around the edge of the foundation pit, and the bottom of the cement mixing interlocking piles extends downward to the top surface of the old basement floor slab obstacle.

[0007] The cast-in-place piles are arranged around the edge of the foundation pit, extending downwards from the ground to below the obstacle of the old basement floor slab. The cast-in-place piles are located on the inner side of the foundation pit relative to the cement mixing interlocking piles. The cast-in-place piles consist of several cast-in-place piles arranged at equal intervals, and each cast-in-place pile is interlocked with the cement mixing interlocking piles.

[0008] Each high-pressure jet grouting pile is installed around the edge of the foundation pit, and the high-pressure jet grouting pile is located below the obstacle of the old basement floor slab, and the gaps between each cast-in-place pile are sealed.

[0009] Furthermore, the cement mixing interlocking pile group is composed of several cement mixing piles interlocking together.

[0010] Furthermore, the core of the cement mixing pile located between two adjacent cast-in-place piles is located on the perpendicular bisector of the line connecting the cores of the two cast-in-place piles; the core of the high-pressure jet grouting pile located between two adjacent cast-in-place piles is located on the perpendicular bisector of the line connecting the cores of the two cast-in-place piles.

[0011] Furthermore, the core of each high-pressure jet grouting pile is located within the coverage area of ​​a corresponding cement mixing pile.

[0012] Furthermore, the borehole diameter of the cast-in-place pile is D; the core spacing of the cement mixing pile is 0.4D; the distance between the centerline of the cement mixing pile and the centerline of the cast-in-place pile is 0.5D; the distance between the core of the high-pressure jet grouting pile and the centerline of the cement mixing interlocking pile is 0.3D; the borehole diameter D of the cast-in-place pile is 1000mm to 1200mm; and the pile diameter of the cement mixing pile is approximately 700 to 800mm.

[0013] This invention also provides a construction method for a structure of support and water-stop curtain passing through an old foundation slab obstacle, including...

[0014] Step 1: Construct cement mixing interlocking piles around the edge of the foundation pit, with the bottom of the cement mixing interlocking piles extending downwards to the top surface of the old basement floor slab obstacle.

[0015] Step 2: Construct cast-in-place piles around the edge of the foundation pit. The cast-in-place piles extend from the ground to the designed depth below the obstacle of the old basement floor slab. The cast-in-place piles are located on the inner side of the foundation pit relative to the cement mixing interlocking piles, and the cast-in-place piles interlock and overlap with the cement mixing interlocking piles.

[0016] Step 3: Construct high-pressure jet grouting piles around the edge of the foundation pit. The high-pressure jet grouting piles will block the gaps between the cast-in-place piles below the obstacle of the old basement floor slab.

[0017] Furthermore, in step 2, the power conversion device of the multi-functional hydraulic drilling rig is used to drive the cutting shoe sleeve, so that the cutting shoe sleeve drills into the old basement floor slab obstacle at the corresponding construction position of the cast-in-place pile, thus completing the separation of the old basement floor slab obstacle at the construction hole position of the cast-in-place pile; the cutting tooth rock stratum core drilling bit is replaced by the multi-functional drilling rig to remove the old basement floor slab obstacle after separation at the construction hole position; then the hole is drilled again to carry out the cast-in-place pile construction.

[0018] Because the location of the cast-in-place piles overlaps with that of the cement-mixed interlocking piles, a cutting shoe sleeve process was adopted for the construction of the cast-in-place piles. This allowed the soil reinforced by the cement-mixed interlocking piles in step 1 to be completely cut and separated, preventing cracking and damage to the cement-mixed soil outside the cast-in-place pile holes. Consequently, the cement-mixed interlocking piles could interlock with the cast-in-place piles on the same plane. Furthermore, by adopting the cutting shoe sleeve process for the construction of the cast-in-place piles, the cutting shoe sleeve could replace the mud slurry wall protection function for the upper soil of the cast-in-place pile holes, thus mitigating the adverse effects of loose fill soil. For the lower soil of the cast-in-place pile holes, the mud slurry mix ratio was improved, and the mud slurry specific gravity was repeatedly measured and controlled to ensure it remained between 1.20 and 1.25 as auxiliary measures to address the adverse effects of "confined water".

[0019] Furthermore, in step 3, the core of each high-pressure jet grouting pile is located within the coverage area of ​​the cement mixing interlocking pile group.

[0020] Furthermore, in step 3, a pilot hole is constructed on the corresponding cement mixing interlocking pile using a geological drilling rig until the pilot hole passes through the obstacle of the old basement floor slab, and then a high-pressure jet grouting pile is constructed using a dual-axis high-pressure jet grouting pile machine.

[0021] Furthermore, the cast-in-place pile group consists of several cast-in-place piles arranged at equal intervals, and each cast-in-place pile is interlocked with a cement-mixed interlocking pile group; the cement-mixed interlocking pile group is composed of several cement-mixed piles interlocking; the core of the cement-mixed pile located between two adjacent cast-in-place piles is located on the perpendicular bisector of the line connecting the cores of the two cast-in-place piles; the core of the high-pressure jet grouting pile located between two adjacent cast-in-place piles is located on the perpendicular bisector of the line connecting the cores of the two cast-in-place piles; the borehole diameter of the cast-in-place pile is D; the core spacing of the cement-mixed piles is 0.4D; the distance between the centerline of the cement-mixed pile and the centerline of the cast-in-place pile group is 0.5D; the distance between the core of the high-pressure jet grouting pile and the centerline of the cement-mixed interlocking pile group is 0.3D; the borehole diameter D of the cast-in-place pile group is 1000mm to 1200mm; the diameter of the cement-mixed pile is approximately 700 to 800mm.

[0022] The structure and construction method of the support and water-stop curtain that the present invention describes for penetrating the old basement slab obstacle adopts the method of "cement mixing - existing old basement slab obstacle - high pressure jet grouting" to form a deep mixing and jet grouting water-stop curtain complex. It can solve the problem that conventional deep foundation pit support water-stop curtain construction methods cannot penetrate the thick old basement slab obstacle. At the same time, it solves the problem that the high pressure jet grouting pile is not suitable for the upper part of the dense old buildings around the construction area, and adapts to the complex terrain conditions on site.

[0023] By setting cement-mixed interlocking piles above the old basement floor slab obstacle, it can adapt to the terrain of deep and loose miscellaneous fill soil layers and the environment of dense surrounding old buildings; by setting high-pressure jet grouting piles below the old basement floor slab obstacle, it can pass through the old basement floor slab obstacle and form piles at a deeper location; by interlocking the cast-in-place piles with support function with cement-mixed interlocking piles and high-pressure jet grouting piles, a composite support system of water-stop curtain is formed, which improves the integrity of the structure.

[0024] In addition, the pilot hole of the geological drilling rig is located within the effective range of the upper cement mixing pile. The geological formation after the soil consolidation makes the pilot hole of the drilling rig less prone to collapse, which allows the dual-tube high-pressure jet grouting drill to quickly reach the working section. It is easy to operate, economical and efficient, and has great value for promotion and application.

[0025] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0026] Figure 1 This is a plan view of the structure of the support and water-stop curtain of the present invention passing through the obstacle of the old base plate;

[0027] Figure 2 for Figure 1 A cross-sectional view at point AA.

[0028] In the diagram: 10. Obstacles in the old basement floor slab; 20. Cement mixing interlocking piles; 21. Pilot hole; 30. Cast-in-place piles; 40. High-pressure jet grouting piles; D. Pit diameter of the cast-in-place pile. Detailed Implementation

[0029] Please see Figure 1 and Figure 2 The structure of a support and water-stop curtain passing through an old basement slab obstacle in this embodiment includes an old basement slab obstacle 10 with a thickness of 1 meter, cement mixing interlocking piles 20, cast-in-place piles 30 and several high-pressure jet grouting piles 40.

[0030] Specifically, the cement mixing interlocking pile 20 is arranged around the edge of the foundation pit, and the bottom of the cement mixing interlocking pile 20 extends downward to the top surface of the old basement floor slab barrier 10;

[0031] More specifically, the cement mixing interlocking pile 20 is composed of several cement mixing piles interlocking together;

[0032] Specifically, the cast-in-place piles 30 are arranged around the edge of the foundation pit, and the cast-in-place piles 30 extend downward from the ground to below the old basement floor obstacle 10. The cast-in-place piles 30 are located on the inner side of the foundation pit relative to the cement mixing interlocking piles 20. The cast-in-place piles 30 are composed of several cast-in-place piles arranged at equal intervals, and each cast-in-place pile is interlocked with the cement mixing interlocking piles 20.

[0033] More specifically, the core of the cement mixing pile located between two adjacent cast-in-place piles is located on the perpendicular bisector of the line connecting the cores of the two cast-in-place piles; the core of the high-pressure jet grouting pile 40 located between two adjacent cast-in-place piles is located on the perpendicular bisector of the line connecting the cores of the two cast-in-place piles.

[0034] Specifically, each high-pressure jet grouting pile 40 is set around the edge of the foundation pit, and the high-pressure jet grouting pile 40 is located below the obstacle 10 of the old basement floor slab, and seals the gap between each cast-in-place pile.

[0035] More specifically, the core of each high-pressure jet grouting pile 40 is located within the coverage area of ​​a corresponding cement mixing pile.

[0036] Specifically, the borehole diameter D of the cast-in-place pile is 1000mm to 1200mm, preferably 1000mm in this embodiment, and the core spacing between the cast-in-place piles is 1.25D; the pile diameter of the cement mixing pile is 700 to 800mm, preferably 700mm in this embodiment, and the core spacing between the cement mixing piles is 0.4D; the distance between the centerline of the cement mixing pile and the centerline of the cast-in-place pile 30 is 0.5D; the pile diameter of the high-pressure jet grouting pile 40 is 600mm, and the distance between the core of the high-pressure jet grouting pile 40 and the centerline of the cement mixing interlocking pile 20 is 0.3D.

[0037] This embodiment also provides a construction method for the above-mentioned water-stop curtain structure, including...

[0038] Step 1: Construct cement mixing interlocking piles around the edge of the foundation pit, with the bottom of the cement mixing interlocking piles extending downwards to the top surface of the old basement floor slab obstacle.

[0039] Step 2: Construct cast-in-place piles around the edge of the foundation pit. The cast-in-place piles extend from the ground to the designed depth below the obstacle of the old basement floor slab. The cast-in-place piles are located on the inner side of the foundation pit relative to the cement mixing interlocking piles, and the cast-in-place piles interlock and overlap with the cement mixing interlocking piles.

[0040] In step 2, since the full-sleeve rotary drilling rig is not suitable for deployment in the case of limited working space in dense old building complexes, this embodiment chooses to drive the cutting shoe sleeve through the rotary drilling bit, so that the cutting shoe sleeve drills into the old basement floor slab obstacle at the corresponding grouting pile construction position, and completes the separation of the old basement floor slab obstacle at the grouting pile construction hole position.

[0041] Since the location of the cast-in-place piles overlaps with that of the cement-mixed interlocking piles, the cast-in-place piles are constructed using a rotary drilling rig with a cutting shoe sleeve. This allows the soil reinforced by the cement-mixed interlocking piles in step 1 to be completely cut and separated, and the cement-mixed soil outside the cast-in-place pile holes does not crack or break. This allows the cement-mixed interlocking piles to interlock with the cast-in-place piles on the same plane.

[0042] In the specific construction process, (1) before rotary drilling, the soil around the pile hole is leveled, and the sleeve anti-fall frame is installed according to the on-site measurement and positioning. The four sides of the anti-fall frame are equipped with fastening bolts, which can play a temporary fastening role when the sleeve is extended or the drill bit is replaced to prevent the cutting shoe sleeve from falling or deviating during the process, affecting the obstacle breaking efficiency and construction quality.

[0043] (2) When the proposed pile location encounters a thick old basement slab, most of the area within the cutting shoe sleeve hole is a reinforced concrete obstacle. The rotary drilling rig can gradually penetrate the old basement slab by replacing the cutting tooth core drill bit, and remove the concrete block by relying on the friction between the drill bit and the separated concrete block. Furthermore, since the old base slab is of limited thickness, and the cutting tooth core drill bit achieves penetration and hole formation by core sampling, the obstacle breaking surface is relatively flat. The drill bit can continue drilling at the original obstacle breaking hole location without needing to cut the sleeve for further drilling to prevent the drill bit from slipping or deviating.

[0044] (3) When the proposed pile location encounters an obstacle such as the side wall of an old basement or a semi-soil, semi-concrete structure, the core drilling bit with cutting teeth cannot smoothly separate the rock strata and extract the concrete block through friction. Therefore, the rotary drilling rig uses an open-body cutting tooth drill bit to break up the old obstacles in the hole. For every 1.2m that the open-body cutting tooth drill bit drills into the obstacle, the cutting shoe sleeve drills to the same depth simultaneously to prevent the drill bit from slipping or deviating.

[0045] (4) During rotary drilling, the rotary drilling rig drives the cutting shoe sleeve to rotate via the drive device. After the cutting shoe sleeve quickly passes through the upper soft soil, it drills into the thick old underground structure obstacle about 0.5m deep, which serves to fix the pile hole position and prevent the drill bit from slipping or deviating. Furthermore, based on the obstacle breaking inside the sleeve, it also greatly reduces the impact on the surrounding soil disturbance.

[0046] (5) After the rotary drilling is completed, the multi-functional hydraulic drilling machine is replaced with a core drilling bit for rock strata cutting and the old basement floor slab obstacle after the construction hole is separated is removed.

[0047] (6) Finally, the grouting construction of the pile foundation is carried out; specifically, the mud ratio is optimized through multiple on-site tests, with a mixture of bentonite and water at a ratio of 8.1:100 as the base mud, and 0.4% industrial sodium carbonate and 0.05% CMC-Na cellulose thickener are added to improve the cementitious properties of the mud. After the borehole passes through the thick bottom plate obstacle, the mud specific gravity is measured and controlled in stages to keep it between 1.20 and 1.25. If necessary, an appropriate amount of perlite powder is added to increase the mud specific gravity and prevent the borehole wall from collapsing due to excessive pressure from the pressurized water at the bottom of the thick bottom plate.

[0048] Step 3: Construct high-pressure jet grouting piles around the edge of the foundation pit. The high-pressure jet grouting piles will block the gaps between the cast-in-place piles below the obstacle of the old basement floor slab.

[0049] In step 3, the core of each high-pressure jet grouting pile is located within the coverage area of ​​the cement mixing interlocking pile; a guide hole is constructed on the corresponding cement mixing interlocking pile using a geological drilling rig until the guide hole passes through the obstacle of the old basement floor slab, and then high-pressure jet grouting pile is constructed using a dual-axis high-pressure jet grouting pile, with the high-pressure jet grouting pile reaching the impermeable rock surface; wherein, the diameter of the jet grouting pipe of the dual-pipe high-pressure jet grouting pile foundation is 50mm~70mm, and the diameter of the guide hole is 90mm.

[0050] Compared with existing technologies, this invention forms a deep mixing and spraying water-stop curtain complex by adopting the method of "cement mixing - existing old basement floor slab obstacle - high pressure jet grouting". This can solve the problem that conventional deep foundation pit support water-stop curtain construction methods cannot penetrate the thick old basement floor slab obstacle. At the same time, it solves the problem that the construction area is surrounded by dense old buildings and it is not suitable to directly use high pressure jet grouting for pile formation on the upper part, adapting to the complex terrain conditions on site.

[0051] By installing cement-mixed interlocking piles above the old basement floor slab obstacle, it is possible to adapt to the terrain of deep and loose fill soil layers and the environment of dense surrounding old buildings; by installing high-pressure jet grouting piles below the old basement floor slab obstacle, it is possible to penetrate the old basement floor slab obstacle and form piles at a deeper location; by interlocking the cast-in-place piles with support function, cement-mixed interlocking piles, and high-pressure jet grouting piles, a composite support system of water-stop curtain is formed, improving the overall integrity of the structure.

[0052] In addition, the pilot hole of the geological drilling rig is located within the effective range of the upper cement mixing pile. The geological formation after the soil consolidation makes the pilot hole of the drilling rig less prone to collapse, which allows the dual-tube high-pressure jet grouting drill to quickly reach the working section. It is easy to operate, economical and efficient, and has great value for promotion and application.

[0053] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A construction method for a structure of support and waterproof curtain penetrating an old foundation slab obstacle, characterized in that, include Step 1: Construct cement mixing interlocking piles (20) around the edge of the foundation pit, with the bottom of the cement mixing interlocking piles (20) constructed downwards to the top surface of the old basement floor barrier (10); Step 2: Construct cast-in-place piles (30) around the edge of the foundation pit. The cast-in-place piles (30) extend from the ground to the impermeable rock surface below the obstacle (10) of the old basement floor slab. The cast-in-place piles (30) are located on the inner side of the foundation pit relative to the cement mixing interlocking piles (20), and the cast-in-place piles (30) interlock and overlap with the cement mixing interlocking piles (20). Step 3: Construct high-pressure jet grouting piles (40) around the edge of the foundation pit. The high-pressure jet grouting piles (40) block the gap between the piles of the cast-in-place piles (30) below the obstacle (10) of the old basement floor slab. In step 2, the cutting shoe sleeve is driven by the power conversion device of the multi-functional hydraulic drilling machine, so that the cutting shoe sleeve drills into the old basement floor obstacle (10) at the construction position of the cast-in-place pile (30), and the old basement floor obstacle (10) at the construction hole position of the cast-in-place pile (30) is separated; then the multi-functional hydraulic drilling machine is replaced with a core drilling bit for rock strata, and the old basement floor obstacle (10) after the construction hole position is separated is removed; then the hole is drilled and the cast-in-place pile (30) construction is carried out. In step 3, the core of each high-pressure jet grouting pile (40) is located within the coverage area of ​​the cement mixing interlocking pile (20); In step 3, a pilot hole (21) is constructed on the corresponding cement mixing interlocking pile (20) by a geological drilling rig until the pilot hole (21) passes through the obstacle (10) of the old basement floor slab, and then the high pressure jet grouting pile (40) is constructed by a dual-axis high pressure jet grouting pile machine. The cast-in-place pile (30) consists of several cast-in-place piles arranged at equal intervals, and each cast-in-place pile is connected to the cement mixing interlocking pile (20); the cement mixing interlocking pile (20) consists of several cement mixing piles interlocking; the core of the cement mixing pile located between two adjacent cast-in-place piles is located on the vertical line of the line connecting the cores of the two cast-in-place piles; the core of the high-pressure jet grouting pile (40) located between two adjacent cast-in-place piles is located on the vertical line of the line connecting the cores of the two cast-in-place piles.

2. The construction method of the structure for supporting and waterproofing curtains penetrating old foundation slab obstacles according to claim 1, characterized in that, The diameter of the cast-in-place pile is D; the core spacing of the cement mixing pile is 0.4D; the distance between the center line of the cement mixing pile and the center line of the cast-in-place pile (30) is 0.5D; the distance between the core of the high-pressure jet grouting pile (40) and the center line of the cement mixing interlocking pile (20) is 0.3D; the diameter D of the cast-in-place pile (30) is 1000mm to 1200mm; the diameter of the cement mixing pile is 700 to 800mm.

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