A backfill method and structure for ultra-deep large-diameter pile holes

Abstract

The invention discloses a backfill method and structure for an ultra-deep large-diameter pile hole. The invention uses a 300mm conduit to be lowered to the bottom of an empty pile. The hole opening is fixed by a steel beam and a chute is arranged on the conduit. When backfilling, the crushed stone is mixed in a ratio of 4:6 and then unloaded from the material port, and the conduit is slid into the conduit through the chute for backfilling, and the length of the conduit is reduced according to the backfilling amount until it is backfilled below the casing and the conduit is removed. Subsequently, the casing is pulled out as appropriate, and the final backfilling is performed. If the casing cannot be pulled out, backfilling is performed directly. When backfilling, backfilling is performed evenly in layers from the middle to the surrounding areas. After the backfilling is completed, the engineering piles are immediately organized for post-grouting operations, and the empty pile grouting operations are performed at the same time to ensure the quality of the empty pile backfilling. The method of the invention can effectively prevent uneven backfilling caused by direct tilting of the empty pile due to the excessive depth of the engineering pile, and can ensure that the pre-buried pipes such as the grouting pipe, the acoustic detection pipe and the core drilling pipe in the hole are not damaged by the backfill soil.

Description

Technical Field

[0001] The invention relates to a backfilling method and structure for an ultra-deep large-diameter pile hole, belonging to the technical field of foundation construction in industrial and civil construction projects. Background Art

[0002] In the foundation construction of the Shenzhen Evergrande Center project, the average design elevation of the top of the engineering piles is -36.5 to -45.9 meters, with an overfill of 2.5 meters. Therefore, there are empty piles at a depth of about 41.8 meters at the top of the engineering piles, and the diameter is 3 meters. If the existing self-unloading backfilling technology is used, due to the large diameter of the empty piles and the deep depth, the backfill material will be tilted, resulting in uneven and loose backfilling, which can easily cause the adjacent bored piles to collapse when the holes are drilled, and there will be safety hazards such as people falling. In addition, due to the existing self-unloading backfilling technology, when the filler falls from a high place during the backfilling process, it is very easy to damage the grouting pipe, acoustic detection pipe and core drilling pipe in the pile hole. Therefore, the existing technology still has shortcomings and needs further improvement. Summary of the invention

[0003] The purpose of the present invention is to provide a backfill method and structure for ultra-deep large-diameter pile holes to solve the problems of uneven and loose backfilling and damage to grouting pipes, acoustic detection pipes and core drilling pipes in the prior art, thereby overcoming the shortcomings of the prior art.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a backfilling method for an ultra-deep large-diameter pile hole, which is constructed according to the following process:

[0006] a. Make cast-in-place pile reinforcement cage and hollow pile reinforcement cage;

[0007] b. Place the cast-in-place pile reinforcement cage into the hole from the pile mouth. When the top of the cast-in-place pile reinforcement cage is flush with the pile mouth, fix the cast-in-place pile reinforcement cage to the pile mouth.

[0008] c. Lift the empty pile reinforcement cage and weld the bottom of the empty pile reinforcement cage to the top of the cast-in-place pile reinforcement cage; remove the fixation between the cast-in-place pile reinforcement cage and the pile mouth, and place the cast-in-place pile reinforcement cage and the empty pile reinforcement cage together into the bottom of the pile hole;

[0009] d. Lay out the grouting pipe, sonic detection pipe and core drilling pipe in the steel cage in advance according to the design requirements. When welding the cast-in-place pile steel cage with the empty pile steel cage, the grouting pipe, sonic detection pipe and core drilling pipe laid out in advance shall also be welded;

[0010] e. Drive a steel casing with a length of 10 to 13 meters into the pile mouth. The top of the steel casing is a certain distance above the ground, and fix the steel beam in the steel casing at the same level as the ground;

[0011] f. Connect multiple conduits with a diameter of not less than 300 mm end to end to form a combined conduit, and place the bottom end of the combined conduit to the welding point between the bottom end of the empty pile reinforcement cage and the top end of the cast-in-place pile reinforcement cage; and fix the top conduit to the steel beam;

[0012] g. Place the chute at an angle between the pipe mouth of the conduit and the top of the steel casing and secure it.

[0013] In the aforementioned backfilling method for the ultra-deep large-diameter pile hole, the filler is backfilled evenly in layers from the middle to the surrounding areas.

[0014] In the aforementioned backfilling method for ultra-deep large-diameter pile holes, the backfill material for the empty pile section is a mixture of stone powder and crushed stone in a ratio of 4:6, plus 6% p.o. 32.5 ordinary Portland cement; the stone particle size is between 5 and 25 mm, of which the content of stone particles with a size of 15-25 mm is not less than 50%.

[0015] In the aforementioned backfilling method for ultra-deep large-diameter pile holes, when backfilling the empty pile section, the combined conduit is pulled out one section upward after backfilling one section, and the top conduit is removed; at the same time, the lower conduit connected to the top conduit is used as the top conduit and connected to the steel beam.

[0016] In the aforementioned backfilling method for the ultra-deep large-diameter pile hole, when the empty pile section is backfilled to be flush with the bottom end of the steel casing, the steel casing is pulled out and the backfilling is continued to be flush with the ground.

[0017] In the aforementioned backfilling method for ultra-deep large-diameter pile holes, grouting is immediately performed through a grouting pipe after the backfilling of the empty pile section is completed. After the grouting is completely solidified, the quality of the grouting result is inspected through a core drill pipe and an acoustic detection pipe to ensure the backfilling quality.

[0018] The backfill structure of an ultra-deep large-diameter pile hole of the present invention, which is constructed according to the above method and used in the above method, comprises a cast-in-place pile arranged in the pile hole of the ultra-deep large-diameter pile hole, a cast-in-place pile reinforcement cage is arranged in the cast-in-place pile, an empty pile reinforcement cage is arranged on the cast-in-place pile reinforcement cage, and the bottom end of the empty pile reinforcement cage is welded to the top end of the cast-in-place pile reinforcement cage; the bottom end of the cast-in-place pile reinforcement cage contacts the bottom of the pile hole, a grouting pipe, an acoustic detection pipe and a core drilling pipe are arranged in the hole of the pile hole, and the grouting pipe, the acoustic detection pipe and the core drilling pipe are respectively fixed on the cast-in-place pile reinforcement cage and the empty pile reinforcement cage. A steel casing is fixed on the pile mouth of the ultra-deep large-diameter pile hole, and the top of the steel casing is higher than the ground. A steel beam is fixed inside the steel casing at a level with the ground. A combined conduit for filling backfilling is installed on the steel beam, and the upper end of the combined conduit is fixed on the steel beam, and the bottom end of the combined conduit is located at the welding point between the bottom end of the empty pile steel cage and the top end of the cast-in-place pile steel cage; a chute for dumping backfilling is placed obliquely on the steel casing, and the lower end of the chute is arranged on the upper end of the combined conduit, and the upper end of the chute is arranged at the upper end of the steel casing.

[0019] The length of the aforementioned steel casing is 10 to 13 meters.

[0020] The aforementioned combined conduit is composed of two or more conduits with a diameter of not less than 300 mm.

[0021] Due to the adoption of the above technical scheme, compared with the prior art, the method of the present invention can effectively prevent uneven backfilling caused by direct tilting of the empty pile of the engineering pile due to the excessive depth, and can ensure that the pre-buried pipes such as the grouting pipe, the acoustic detection pipe and the core drilling pipe in the hole are not damaged by the backfill soil. A 300mm conduit is lowered to the bottom of the empty pile, and the orifice is fixed by a steel beam to the conduit, and a chute is provided on it. When backfilling, the crushed stone is mixed in a ratio of 4:6 and then unloaded from the material port, and slid into the conduit through the chute for backfilling, and the conduit length is reduced according to the backfill amount until it is backfilled below the casing and the conduit is removed. Subsequently, the casing is pulled out according to the situation, and the final backfill is performed. If the casing cannot be pulled out, it is directly backfilled. When backfilling, backfill evenly in layers from the middle to the surrounding areas. After the backfilling is completed, the post-grouting operation of the engineering pile is immediately organized, and the empty pile grouting operation is performed at the same time to ensure the quality of the empty pile backfill. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention.

[0023] The markings in the figure are as follows: 1- cast-in-place pile reinforcement cage, 2- empty pile reinforcement cage, 3- grouting pipe, 4- sonic detection pipe, 5- core drilling pipe, 6- steel casing, 7- ground, 8- combined conduit, 9- steel beam, 10- chute, 11- cast-in-place pile. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] A backfilling method for an ultra-deep large-diameter pile hole according to the present invention is as follows: Figure 1 As shown, Figure 1 In order to clearly see the cast-in-place pile 11 with the cast-in-place pile reinforcement cage 1, the cast-in-place pile 11 is cut off; the actual cast-in-place pile 11 is an integral structure from bottom to top; in addition, since the entire pile hole is very deep, Figure 1The vertical proportion is compressed and not drawn according to the actual proportion, mainly highlighting the structure of the empty pile part above the top of the bored pile 11; the method is constructed according to the following process: make a bored pile reinforcement cage 1 and an empty pile reinforcement cage 2 → put the bored pile reinforcement cage 1 into the hole from the pile mouth, when the top of the bored pile reinforcement cage 1 is flush with the pile mouth, fix the bored pile reinforcement cage 1 to the pile mouth → lift the empty pile reinforcement cage 2, and weld the bottom end of the empty pile reinforcement cage 2 to the top of the bored pile reinforcement cage 1; remove the fixation of the bored pile reinforcement cage 1 to the pile mouth, put the bored pile reinforcement cage 1 and the empty pile reinforcement cage 2 into the bottom of the pile hole together → put the grouting pipe 3, the acoustic detection pipe 4 and the core drilling pipe 5 in the hole in advance according to the design requirements, and the bored pile reinforcement cage and the empty pile reinforcement cage are fixed together. When welding the steel cage, the grouting pipe, sonic detection pipe and core drilling pipe that have been laid out in advance are also welded → a steel casing 6 with a length of 10 to 13 meters is driven into the pile mouth, the top of the steel casing 6 is a distance above the ground 7, and a steel beam is fixed in the steel casing 6 at a horizontal position with the ground 7 → multiple conduits with a diameter of not less than 300 mm are connected end to end to form a combined conduit 8, and the bottom end of the combined conduit 8 is placed at the welding point between the bottom end of the empty pile steel cage 2 and the top end of the cast-in-place pile steel cage 1; and the top section conduit is fixedly connected to the steel beam 9 → the chute 10 is tilted and placed between the pipe mouth of the conduit and the top of the steel casing 6 and fixed → the backfill is unloaded from the top of the chute 10, and slides into the conduit through the chute 10 for backfilling.

[0026] In the specific implementation, the filler is backfilled evenly in layers from the middle to the surroundings. The backfill is divided into two sections: the cast-in-place pile section and the empty pile section; the backfill material is a mixture of stone powder and crushed stone with a ratio of 4:6, plus 6% p.o32.5 ordinary Portland cement; the stone particle size is between 5 and 25 mm, of which the content of stone particles with a size of 15-25 mm is not less than 50%. When backfilling the empty pile section, after backfilling a section, the combined guide tube 8 is pulled out one section upward, and the top section guide tube is removed. When the empty pile section is backfilled to the same level as the bottom end of the steel casing 6, the steel casing 6 is pulled out and the backfill is continued to be flush with the ground 7. After the backfilling of the empty pile section is completed, the grouting operation is immediately carried out through the grouting pipe 3. After the grouting is completely solidified, the grouting result is quality inspected through the core drilling pipe 5 and the acoustic detection pipe 4 to ensure the quality of the backfill.

[0027] The backfill structure of an ultra-deep large-diameter pile hole of the present invention, which is constructed according to the above method and used in the above method, is as follows: Figure 1As shown, the structure includes a cast-in-place pile 11 arranged in a pile hole of an ultra-deep large-diameter pile hole, a cast-in-place pile steel cage 1 is arranged in the cast-in-place pile 11, an empty pile steel cage 2 is arranged on the cast-in-place pile steel cage 1, the bottom end of the empty pile steel cage 2 is welded to the top of the cast-in-place pile steel cage 1; and the bottom end of the cast-in-place pile steel cage 1 is in contact with the bottom of the pile hole, and a grouting pipe 3, an acoustic detection pipe 4 and a core drilling pipe 5 are arranged in the hole of the pile hole in a conventional manner. When setting, in order to prevent the grouting pipe 3, the acoustic detection pipe 4 and the core drilling pipe 5 from being damaged during the working process, the grouting pipe 3, the acoustic detection pipe 4 and the core drilling pipe 5 are respectively fixed on the cast-in-place pile steel cage 1 and the empty pile steel cage 2, and then a steel casing 6 is fixed on the pile mouth of the ultra-deep large-diameter pile hole, the length of the steel casing 6 is controlled within the range of 10 to 13 meters, and the top of the steel casing 6 is about 0.5 meters higher than the ground 7. A distance of 1 to 2 meters is provided, a steel beam 9 is fixed in the steel casing 6 at a horizontal position with the ground 7, a combined conduit 8 for filling backfill is installed on the steel beam 9, the upper end pipe mouth of the combined conduit 8 is fixed on the steel beam 9, and the bottom port of the combined conduit 8 is located at the welding place between the bottom end of the empty pile reinforcement cage 2 and the top end of the cast-in-place pile reinforcement cage 1. Under normal circumstances, the combined conduit 8 can be formed by connecting two conduits with a diameter of not less than 300 mm. When the depth of the ultra-deep large-diameter pile hole is long, three or more conduits with a diameter of not less than 300 mm can be used to connect the combined conduit 8 according to the length requirements; a chute 10 for dumping backfill is placed obliquely on the steel casing 6, the lower port of the chute 10 is set on the upper end pipe mouth of the combined conduit 8, and the upper port of the chute 10 is set at the upper end of the steel casing 6. Example

[0028] The following is a detailed description of the backfill method of the ultra-deep large-diameter pile hole of the present invention, taking the Evergrande Center project as an example. In this project, since the top design elevation of the bored pile 11 is -36.5 to -45.9m, and the over-casting is 2.5m, there are about 41.8m of empty piles. Considering the depth, diameter and other characteristics of the empty piles, the traditional self-unloading backfilling will result in the empty pile depth being too large, the backfill material being tilted, resulting in uneven backfilling, and the self-unloading backfilling cannot ensure that the pre-buried pipes such as the grouting pipe 3, the sonic detection pipe 4 and the core drilling pipe 5 in the hole are not damaged by the backfill material. In order to ensure that the backfill material can be densely backfilled, ensure that the pre-buried pipes such as the grouting pipe 3, the sonic detection pipe 4 and the core drilling pipe 5 in the hole are not damaged by the backfill material to affect the construction process. Therefore, the catheter is used in combination with a graded sand and gravel material machine for backfilling. The specific method is as follows:

[0029] 1. It is planned to extend the cast-in-place pile reinforcement cage 1 to the hole mouth (extended by about 41.8m, according to the actual length of each pile). The reinforcement cage is made in two stages. First, the cast-in-place pile reinforcement cage 1 required by the design is completed, and then the extended part of the empty pile reinforcement cage 2 is completed. When the cast-in-place pile reinforcement cage 1 is hoisted into the hole, the cast-in-place pile reinforcement cage 1 is fixed when the top is flush with the hole mouth, and then the empty pile reinforcement cage 2 is hoisted and firmly connected with the cast-in-place pile reinforcement cage 1. After the connection is completed, they are lowered together to the required position at the bottom of the pile hole.

[0030] 2. To ensure that the embedded pipes such as the grouting pipe 3, the acoustic detection pipe 4 and the core drilling pipe 5 in the hole are not damaged by the backfill soil during backfilling, a 300mm conduit is lowered to the bottom of the empty pile. The conduit is fixed by a steel beam 9 at the hole mouth, and a chute 10 is set on it. The backfill material is a mixture of stone powder and crushed stone with a ratio of 4:6, plus 6% p.o32.5 ordinary Portland cement. The stone specifications are: the particle size is not more than 25mm, the size is between 5 and 25mm, and the content of stone particles of 15 to 25mm is not less than 50%. When backfilling, the backfill material is mixed and unloaded from the material port, and slides into the conduit through the chute 10 for backfilling, and the length of the conduit is reduced according to the backfilling amount until it is backfilled to the bottom of the casing (about 10 to 12m from the hole mouth), and the conduit is removed. Then the casing is pulled out according to the situation, and the final backfilling is carried out. If the casing cannot be pulled out, it is directly backfilled. When backfilling, backfill evenly in layers from the middle to the surrounding areas. After backfilling is completed, immediately organize the post-grouting operation of the engineering piles and carry out the empty pile grouting operation at the same time to ensure the quality of the empty pile backfill.

[0031] 3. When backfilling empty piles, the mud in the hole is first pumped to the mud box by the mud pump, and backfilled every 5m, and backfilled in sequence until the backfilling in the hole is completed, in order to ensure civilized construction on site and avoid mud cross-flow and pollution of the site. The mud in the mud box is then transported out of the site using a mud pool.

[0032] Through field tests using the technical solution of the present invention, it is proved that the present invention can effectively prevent uneven backfilling caused by direct tilting of the empty pile of the engineering pile due to the excessive depth, and can ensure that the pre-buried pipes such as the grouting pipe, the acoustic detection pipe and the core drilling pipe in the hole are not damaged by the backfill soil. A 300mm conduit is lowered to the bottom of the empty pile, and the orifice is fixed by a steel beam to the conduit, and a chute is provided on it. When backfilling, the crushed stone is mixed in a ratio of 4:6 and unloaded from the material port, and slides into the conduit through the chute for backfilling, and the conduit length is reduced according to the backfilling amount until it is backfilled below the casing (about 10 to 12m from the orifice), and the conduit is removed. Then, the casing is pulled out according to the situation, and the final backfill is carried out. If the casing cannot be pulled out, it is directly backfilled. When backfilling, backfill evenly from the middle to the surrounding layers. After the backfilling is completed, the post-grouting operation of the engineering pile is immediately organized, and the empty pile grouting operation is carried out at the same time to ensure the quality of the empty pile backfilling.

Claims

1. A backfilling method for ultra-deep large-diameter pile holes, characterized in that: The method is constructed according to the following process: a. Make cast-in-place pile reinforcement cage and hollow pile reinforcement cage; b. Place the cast-in-place pile reinforcement cage into the hole from the pile mouth. When the top of the cast-in-place pile reinforcement cage is flush with the pile mouth, fix the cast-in-place pile reinforcement cage to the pile mouth. c. Lift the empty pile reinforcement cage and weld the bottom of the empty pile reinforcement cage to the top of the cast-in-place pile reinforcement cage; remove the fixation between the cast-in-place pile reinforcement cage and the pile mouth, and place the cast-in-place pile reinforcement cage and the empty pile reinforcement cage together into the bottom of the pile hole; d. Lay out the grouting pipe, sonic detection pipe and core drilling pipe in the steel cage in advance according to the design requirements. When welding the cast-in-place pile steel cage with the empty pile steel cage, the grouting pipe, sonic detection pipe and core drilling pipe laid out in advance shall also be welded; e. Drive a steel casing with a length of 10 to 13 meters into the pile mouth. The top of the steel casing is a certain distance above the ground, and fix the steel beam in the steel casing at the same level as the ground; f. Connect multiple conduits with a diameter of not less than 300 mm end to end to form a combined conduit, and place the bottom end of the combined conduit to the welding point between the bottom end of the empty pile reinforcement cage and the top end of the cast-in-place pile reinforcement cage; and fix the top conduit to the steel beam; g. Place the chute obliquely between the pipe opening of the combined conduit and the top opening of the steel casing and fix it; h. Remove the backfill material from the top of the chute and slide it through the chute into the combined conduit for backfilling.

2. The backfilling method of the ultra-deep large-diameter pile hole according to claim 1 is characterized in that: During the filling process, the filler is backfilled evenly in layers from the middle to the surrounding areas.

3. The backfilling method of the ultra-deep large-diameter pile hole according to claim 1 is characterized in that: The backfill material for the empty pile section is a mixture of stone powder and crushed stone in a ratio of 4:6, plus 6% p.o32.5 ordinary Portland cement; the stone particle size is between 5 and 25 mm, of which the content of stone particles with a size of 15-25 mm is not less than 50%.

4. The backfilling method of the ultra-deep large-diameter pile hole according to claim 3 is characterized in that: When the empty pile section is backfilled, the combined conduit is pulled out one section upward after backfilling one section, and the top conduit is removed; at the same time, the lower conduit connected to the top conduit is used as the top conduit to be connected to the steel beam.

5. The backfilling method of the ultra-deep large-diameter pile hole according to claim 3 is characterized in that: When the empty pile section is backfilled to be flush with the bottom end of the steel casing, the steel casing is pulled out and backfilled to be flush with the ground.

6. The backfilling method of the ultra-deep large-diameter pile hole according to claim 1 is characterized in that: After the backfill of the empty pile section is completed, grouting operations are immediately carried out through the grouting pipe. After the grouting is completely solidified, the quality of the grouting results is inspected through the core drill pipe and the acoustic detection tube to ensure the quality of the backfill.

7. A backfill structure for an ultra-deep large-diameter pile hole constructed according to any one of claims 1 to 6, comprising a cast-in-place pile (11) arranged in the pile hole of the ultra-deep large-diameter pile hole, a cast-in-place pile reinforcement cage (1) arranged in the cast-in-place pile (11), characterized in that: An empty pile steel cage (2) is provided on the cast-in-place pile steel cage (1), and the bottom end of the empty pile steel cage (2) is welded to the top end of the cast-in-place pile steel cage (1); the bottom end of the cast-in-place pile steel cage (1) contacts the bottom of the pile hole, a grouting pipe (3), an acoustic detection pipe (4) and a core drilling pipe (5) are provided in the pile hole, the grouting pipe (3), the acoustic detection pipe (4) and the core drilling pipe (5) are respectively fixed to the cast-in-place pile steel cage (1) and the empty pile steel cage (2), a steel casing (6) is fixed to the pile mouth of the ultra-deep large-diameter pile hole, the top of the steel casing (6) is higher than the ground (7), and the steel casing (6) is provided with a plurality of steel casings (6). A steel beam (9) is fixed at a position horizontal to the ground (7), a combined conduit (8) for filling backfill is installed on the steel beam (9), and the upper end of the combined conduit (8) is fixed on the steel beam (9), and the bottom end of the combined conduit (8) is located at the welding point between the bottom end of the empty pile reinforcement cage (2) and the top end of the cast-in-place pile reinforcement cage (1); a chute (10) for pouring backfill is placed obliquely on the steel casing (6), the lower end of the chute (10) is arranged on the upper end of the combined conduit (8), and the upper end of the chute (10) is arranged at the upper end of the steel casing (6).

8. The backfill structure of the ultra-deep large-diameter pile hole according to claim 7 is characterized in that: The length of the steel casing (6) is 10 to 13 meters.

9. The backfill structure of the ultra-deep large-diameter pile hole according to claim 7, characterized in that: The combined conduit (8) is formed by connecting two or more conduits with a diameter of not less than 300 mm.

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