Pile foundation construction process applied to loose foundation

Abstract

The invention discloses a pile foundation construction technology applied to a loose foundation. The pile foundation construction technology comprises the following steps that S1, construction preparation is conducted; s2, embedding a steel casing; s3, drilling for the first time; s4, pre-mixed solid fluidized soil is poured; s5, secondary drilling is carried out; s6, hole cleaning operation is carried out; s7, steel reinforcement cage construction; s8, concrete pouring; and S9, maintaining and detecting a finished product. Compared with the prior art, the method has the following advantages and effects that primary drilling is conducted, the premixed solid fluidized soil is poured into the primary formed hole, traditional concrete is replaced with the premixed solid fluidized soil, pre-filling of the primary drilled hole is achieved, hole collapse of the primary formed hole is avoided, and the concrete consumption and extra cost are reduced; and then secondary drilling is conducted on the premixed solid fluidized soil pile, a reinforcement cage is arranged below the premixed solid fluidized soil pile, construction of a pile foundation is achieved, the hole collapse problem in a pebble bed poor in grading is effectively solved, the using amount of concrete is remarkably reduced, and double optimization of the construction cost and the construction period is achieved.

Description

Technical Field

[0001] This invention relates to the field of building construction, and in particular to a pile foundation construction process applied to loose foundations. Background Technology

[0002] As the construction industry develops towards high-rise and large-scale buildings, the weight of the main structure of buildings continues to increase, and the requirements for the bearing capacity of the foundation become increasingly stringent. Pile foundations are widely used in various construction projects due to their good bearing capacity.

[0003] However, some construction projects are located in remote areas with complex geological conditions. In particular, when the pile foundation passes through a poorly graded pebble layer, problems such as instantaneous loss of mud and collapse of the borehole are very likely to occur during the drilling process, affecting the normal construction of the pile foundation.

[0004] Traditional methods for dealing with collapsed boreholes often involve extending the casing, backfilling with clay, or directly pouring concrete to fill the hole.

[0005] If an extended casing is used, it can only deal with shallow hole collapse. Backfilling with clay is difficult to form effective support. Directly pouring concrete will lead to a significant increase in concrete usage, which will not only greatly increase construction costs, but also affect the overall project progress due to the excessively long treatment cycle. This needs to be improved. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a pile foundation construction process for loose foundations, which can effectively solve the problem of hole collapse in poorly graded gravel layers, significantly reduce the amount of concrete used, and achieve dual optimization of construction cost and construction period.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a pile foundation construction process applied to loose foundations, comprising the following steps: S1, Construction preparation: Clear obstacles in the construction area, level and compact the site to ensure the stability of the drilling rig. Then, use the total station coordinate method to accurately lay out the pile position with the error controlled within ±2cm. At the same time, set cross-shaped protective piles at 1 and 2 times the pile diameter at the center of the pile position and mark the protective piles with reflective stickers. S2. Install steel casing. The inner diameter of the steel casing is 20-40cm larger than the designed pile diameter. It is buried in the ground and the top surface is 0.3m above the construction ground. The steel casing is hoisted after the hole is drilled by rotary drilling rig. The center of the casing is adjusted to coincide with the pile position by the pile protection line. The inclination is controlled within 1%. Clay is backfilled symmetrically around and at the bottom and compacted in layers. The plane position and verticality are checked again. The top elevation of the casing is measured to calculate the designed hole depth. S3, initial drilling: After the drilling rig is in place, use the built-in leveling system to calibrate the verticality of the drill rod. After the level is checked and confirmed to be correct, lock it. Control the drilling speed at 20-30 meters / hour and adjust the drilling pressure to 10-15 tons. Take a cuttings sample every 2 meters to record the geological conditions. If you encounter a boulder, switch to low-speed impact mode to avoid drill bit deviation. S4, premixed solid fluidized soil grouting: First, clean the borehole, thoroughly clean the collapsed area, remove the collapsed soil and debris until the designed hole depth is reached, and then pour the premixed solid fluidized soil into the cleaned hole to ensure that the grouting is dense. S5, secondary drilling: After the drilling rig is in place, adjust the position of the drill rod so that the center of the drill rod is in the same straight line as the center of the solid fluidized soil pile. Then drill and drill a hole in the center of the solid fluidized soil pile. S6, Hole cleaning operation: Lower the reverse circulation guide tube to 30-50cm above the bottom of the hole and connect it to the vacuum pump. Use reverse suction to extract the sediment from the bottom of the hole. If large pebbles are encountered, use the hole cleaning bucket to grab them mechanically. Repeat the operation until the sediment thickness meets the standard. S7. Reinforcing cage construction: A crane is used in conjunction with a guide frame to lower the cage vertically. The lowering speed is controlled at 0.5-1m / min to avoid collision with the hole wall, which could lead to collapse or deformation of the reinforcing cage. The verticality is checked multiple times during the installation process to ensure that the center of the reinforcing cage coincides with the center of the pile position. After it is in place, it is fixed firmly to prevent it from floating or shifting during concrete pouring. S8, concrete pouring, using the tremie pipe method, with the tremie pipe diameter adapted to the pile diameter, a water tightness test is conducted before installation, and the bottom of the hole is checked again before pouring. If the sediment exceeds the standard, the hole is cleaned a second time. The concrete slump is controlled within a reasonable range. During pouring, the tremie pipe is always buried at a depth of 2-6m, and the tremie pipe is pulled out at a uniform speed to avoid the tremie pipe being pulled out of the concrete surface and causing the pile to break. Pour to 0.5-1.0m above the design elevation of the pile top to ensure that the concrete strength at the pile top meets the standard. The pouring process is continuous, and the pouring volume and pouring time are recorded. S9. Finished product curing and testing: After the concrete is poured, it should be covered and cured in a timely manner for no less than 14 days. After the pile is formed, the integrity of the pile body should be tested by low strain reflection wave method or ultrasonic method. The bearing capacity test should be carried out by static load test according to the design requirements to ensure that the pile foundation meets the requirements of the project.

[0008] In a preferred embodiment, the present invention can be further configured as follows: in step S5, when secondary drilling is performed, bentonite slurry is used for wall protection, and the slurry density is maintained at 1.1-1.2 g / cm³. If the pebble layer has extremely high permeability, causing slurry loss, a polymer additive is added to enhance the adhesion.

[0009] In a preferred embodiment, the present invention may be further configured such that the premixed solid fluidized soil is composed of slag, cement, curing agent and water, wherein the mass ratio of each component is 100:8:2:25.

[0010] In a preferred embodiment, the present invention can be further configured as follows: in step S4, before grouting the premixed solid fluidized soil, the wire mesh is first wound into a cylindrical shape, the sections of wire mesh are connected and lowered into the initial hole, and then the premixed solid fluidized soil is grouted.

[0011] In a preferred embodiment, the present invention can be further configured such that the diameter of the cylindrical shape formed by the wire mesh is 3-5 cm smaller than the diameter of the hole initially drilled.

[0012] In a preferred embodiment, the present invention can be further configured such that: a locking element is provided between two adjacent sections of wire mesh, the locking element including a pair of locking plates and a pair of locking hooks, the pair of locking plates being arranged in layers, the locking hooks being provided on the opposite side of each locking plate and used to hook the upper and lower ends of the wire mesh, and each locking plate having a locking tooth on the side opposite to the locking hook, the locking tooth being used to pass through the opposite locking plate and engage with the locking plate for fixation.

[0013] In a preferred embodiment, the present invention can be further configured such that the closed openings of two adjacent sections of the wire mesh are staggered.

[0014] In a preferred embodiment, the present invention may be further configured such that: the lower end of the wire mesh is provided with an insertion rod, and the upper end is provided with an insertion ring for inserting the insertion rod.

[0015] In summary, the present invention has the following beneficial effects: 1. By performing an initial drilling and injecting pre-mixed solid fluidized soil into the initial hole, the pre-filling of the initial hole is achieved by using pre-mixed solid fluidized soil to replace traditional concrete, thus avoiding the collapse of the initial hole, reducing the amount of concrete used and additional expenses. Then, a second drilling is performed on the pre-mixed solid fluidized soil pile, and a steel cage is placed below to realize the construction of the pile foundation. This effectively solves the problem of hole collapse in poorly graded gravel layers, significantly reduces the amount of concrete used, and achieves dual optimization of construction costs and construction period. 2. By setting a cylindrical structure made of wire mesh inside the initial hole as a reinforcing cage, the structural strength of the premixed solid fluidized soil pile is improved after the premixed solid fluidized soil is formed. In the later pile foundation forming process, the inner and outer reinforcing cages are formed to support the pile foundation, thereby improving the structural strength of the pile foundation. This method is suitable for pile forming on loose foundations such as gravel layers. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the wire mesh structure in the embodiment; Figure 2 This is a schematic diagram of the connection relationship of the wire mesh in the embodiment; Figure 3This is a schematic diagram of the locking component in an embodiment.

[0017] Reference numerals: 1. Wire mesh; 11. Insert rod; 12. Insert ring; 2. Locking element; 21. Locking plate; 22. Locking hook; 23. Locking tooth. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings.

[0019] A pile foundation construction process for loose foundations includes the following steps: S1. Construction preparation: Clear obstacles in the construction area, level and compact the site to ensure the stability of the drilling rig. Then, use the total station coordinate method to accurately lay out the pile position with the error controlled within ±2cm. At the same time, set cross-shaped protective piles at 1 and 2 times the pile diameter at the center of the pile position, and mark the protective piles with reflective stickers.

[0020] S2. Install steel casing. The inner diameter of the steel casing is 20-40cm larger than the designed pile diameter. It is buried in the ground, and the top surface is 0.3m above the construction ground. The steel casing is hoisted after the hole is drilled by a rotary drilling rig. The center of the casing is adjusted to coincide with the pile position by the pile guide line. The inclination is controlled within 1%. Clay is backfilled symmetrically around and at the bottom and compacted in layers. The plane position and verticality are checked again. The top elevation of the casing is measured to calculate the designed hole depth.

[0021] S3, initial drilling: After the drilling rig is in place, use the built-in leveling system to calibrate the verticality of the drill rod. After verifying the accuracy of the level, lock it in place. Control the drilling speed at 20-30 meters per hour and adjust the drilling pressure to 10-15 tons. Take a cuttings sample every 2 meters to record the geological conditions. If you encounter a boulder, switch to low-speed impact mode to avoid drill bit deviation.

[0022] S4, premixed solid fluidized soil grouting, first clean the borehole, including the collapsed area, to remove the collapsed soil and debris until the designed borehole depth.

[0023] Then, the wire mesh 1 is rolled into a cylindrical shape, and the sections of wire mesh 1 are connected and lowered into the initial hole. The diameter of the cylindrical shape formed by rolling the wire mesh 1 is 3-5 cm smaller than the diameter of the initial hole. This ensures that the wire mesh 1 can be lowered smoothly and that it is formed inside the premixed solid fluidized soil pile later and located on the outside, so as not to affect the secondary drilling.

[0024] Finally, premixed solid fluidized soil is poured into the cleaned ducts to ensure compaction. The premixed solid fluidized soil is composed of slag, cement, solidifying agent, and water, with a mass ratio of 100:8:2:25.

[0025] S5, secondary drilling: After the drilling rig is in place, adjust the position of the drill rod so that the center of the drill rod is in the same straight line as the center of the solid fluidized soil pile. Then drill and drill a hole in the center of the solid fluidized soil pile.

[0026] When secondary drilling is carried out, bentonite slurry is used for wall protection, and the slurry density is maintained at 1.1-1.2 g / cm³. If the pebble layer has high permeability and causes slurry loss, polymer additives are added to enhance the adhesion.

[0027] S6, Hole cleaning operation: Lower the reverse circulation guide tube to 30-50cm above the bottom of the hole and connect it to the vacuum pump. Use reverse suction to extract the sediment from the bottom of the hole. If large pebbles are encountered, use the hole cleaning bucket to grab them mechanically. Repeat the operation until the sediment thickness meets the standard.

[0028] S7. For the construction of the reinforcing cage, a crane is used in conjunction with a guide frame to lower it vertically. The lowering speed is controlled at 0.5-1m / min to avoid collision with the hole wall, which could lead to collapse or deformation of the reinforcing cage. During the installation process, the verticality is checked multiple times to ensure that the center of the reinforcing cage coincides with the center of the pile position. After it is in place, it is firmly fixed to prevent it from floating or shifting during concrete pouring.

[0029] S8, concrete pouring, using the tremie pipe method, with the tremie pipe diameter adapted to the pile diameter. A water tightness test is conducted before installation. Before pouring, the sediment at the bottom of the hole is checked again. If it exceeds the standard, the hole is cleaned a second time. The concrete slump is controlled within a reasonable range. During pouring, the tremie pipe is always buried at a depth of 2-6m. The tremie pipe is pulled out at a uniform speed to avoid the tremie pipe being pulled out of the concrete surface, which could cause the pile to break. Pour to 0.5-1.0m above the design elevation of the pile top to ensure that the concrete strength at the pile top meets the standard. The pouring process is continuous, and the pouring volume and pouring time are recorded.

[0030] S9. Finished product curing and testing: After the concrete is poured, it should be covered and cured in a timely manner for no less than 14 days. After the pile is formed, the integrity of the pile body should be tested by low strain reflection wave method or ultrasonic method. The bearing capacity test should be carried out by static load test according to the design requirements to ensure that the pile foundation meets the requirements of the project.

[0031] Therefore, by performing the initial drilling and injecting pre-mixed solid fluidized soil into the initial hole, the pre-filling of the initial hole can be achieved by using pre-mixed solid fluidized soil instead of traditional concrete, thus avoiding the collapse of the initial hole and reducing the amount of concrete used and additional costs.

[0032] Then, secondary drilling is carried out on the pre-mixed solid fluidized soil piles, and a steel cage is placed below to realize the construction of the pile foundation. This effectively solves the problem of hole collapse in the poorly graded gravel layer, significantly reduces the amount of concrete used, and achieves dual optimization of construction cost and construction period.

[0033] Compared to traditional methods for dealing with collapsed boreholes, the economic benefits of premixed solid fluidized soil technology are mainly reflected in two aspects: Firstly, it saves direct costs by avoiding the problem of concrete usage increasing exponentially in traditional methods. The cost of premixed solid fluidized soil material is lower, which significantly reduces the direct costs of hole collapse treatment. Secondly, indirect costs were optimized. By controlling the solidification time, the processing period was shortened, reducing indirect costs such as equipment idleness and labor waiting, thus achieving the optimal solution for both cost and time.

[0034] like Figure 1 , Figure 2 As shown, the closed openings of adjacent sections of wire mesh 1 are staggered to enhance the structural strength of the wire mesh 1 and prevent collapse during the pouring of pre-mixed solid fluidized soil. A locking element 2 is installed between adjacent sections of wire mesh 1 to connect and fix them, increasing the structural strength and stability of the wire mesh 1. A rod 11 is installed at the lower end of the wire mesh 1, and a ring 12 is installed at the upper end for inserting the rod 11, thus limiting and fixing adjacent sections of wire mesh 1, ensuring that the wire mesh 1 is lowered in a straight line into the initial hole, guaranteeing the accuracy of the wire mesh 1's position.

[0035] like Figure 2 , Figure 3 As shown, the locking component 2 includes a pair of locking plates 21 and a pair of locking hooks 22. The pair of locking plates 21 are arranged in upper and lower layers, and the locking hooks 22 are located on opposite sides of each locking plate 21 and are used to hook the upper and lower ends of the wire mesh 1. Each locking plate 21 has a locking tooth 23 on the side opposite to the locking hook 22. The locking tooth 23 is used to pass through the opposite locking plate 21 and engage with the locking plate 21 for fixation.

[0036] When it is necessary to connect two adjacent sections of wire mesh 1, a pair of locking hooks 22 are positioned on the two adjacent sections of wire mesh 1. Then, the teeth 23 on each locking plate 21 are inserted into the other locking plate 21. The pair of locking plates 21 are then brought closer to each other, so that the locking hooks 22 hook the wire mesh 1. At the same time, under the action of the teeth 23, the locking plates 21 are locked and fixed, thus completing the quick connection and fixation of the wire mesh 1.

[0037] The specific embodiments are merely illustrative of the present invention and are not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A pile foundation construction technology applied to loose foundations, characterized in that: Includes the following steps: S1, Construction preparation: Clear obstacles in the construction area, level and compact the site to ensure the stability of the drilling rig. Then, use the total station coordinate method to accurately lay out the pile position with the error controlled within ±2cm. At the same time, set cross-shaped protective piles at 1 and 2 times the pile diameter at the center of the pile position and mark the protective piles with reflective stickers. S2. Install steel casing. The inner diameter of the steel casing is 20-40cm larger than the designed pile diameter. It is buried in the ground and the top surface is 0.3m above the construction ground. The steel casing is hoisted after the hole is drilled by rotary drilling rig. The center of the casing is adjusted to coincide with the pile position by the pile protection line. The inclination is controlled within 1%. Clay is backfilled symmetrically around and at the bottom and compacted in layers. The plane position and verticality are checked again. The top elevation of the casing is measured to calculate the designed hole depth. S3, initial drilling: After the drilling rig is in place, use the built-in leveling system to calibrate the verticality of the drill rod. After the level is checked and confirmed to be correct, lock it. Control the drilling speed at 20-30 meters / hour and adjust the drilling pressure to 10-15 tons. Take a cuttings sample every 2 meters to record the geological conditions. If you encounter a boulder, switch to low-speed impact mode to avoid drill bit deviation. S4, premixed solid fluidized soil grouting: First, clean the borehole, thoroughly clean the collapsed area, remove the collapsed soil and debris until the designed hole depth is reached, and then pour the premixed solid fluidized soil into the cleaned hole to ensure that the grouting is dense. S5, secondary drilling: After the drilling rig is in place, adjust the position of the drill rod so that the center of the drill rod is in the same straight line as the center of the solid fluidized soil pile. Then drill and drill a hole in the center of the solid fluidized soil pile. S6, Hole cleaning operation: Lower the reverse circulation guide tube to 30-50cm above the bottom of the hole and connect it to the vacuum pump. Use reverse suction to extract the sediment from the bottom of the hole. If large pebbles are encountered, use the hole cleaning bucket to grab them mechanically. Repeat the operation until the sediment thickness meets the standard. S7. Reinforcing cage construction: A crane is used in conjunction with a guide frame to lower the cage vertically. The lowering speed is controlled at 0.5-1m / min to avoid collision with the hole wall, which could lead to collapse or deformation of the reinforcing cage. The verticality is checked multiple times during the installation process to ensure that the center of the reinforcing cage coincides with the center of the pile position. After it is in place, it is fixed firmly to prevent it from floating or shifting during concrete pouring. S8, concrete pouring, using the tremie pipe method, with the tremie pipe diameter adapted to the pile diameter, a water tightness test is conducted before installation, and the bottom of the hole is checked again before pouring. If the sediment exceeds the standard, the hole is cleaned a second time. The concrete slump is controlled within a reasonable range. During pouring, the tremie pipe is always buried at a depth of 2-6m, and the tremie pipe is pulled out at a uniform speed to avoid the tremie pipe being pulled out of the concrete surface and causing the pile to break. Pour to 0.5-1.0m above the design elevation of the pile top to ensure that the concrete strength at the pile top meets the standard. The pouring process is continuous, and the pouring volume and pouring time are recorded. S9. Finished product curing and testing: After the concrete is poured, it should be covered and cured in a timely manner for no less than 14 days. After the pile is formed, the integrity of the pile body should be tested by low strain reflection wave method or ultrasonic method. The bearing capacity test should be carried out by static load test according to the design requirements to ensure that the pile foundation meets the requirements of the project.

2. The pile foundation construction technology applied to loose foundations according to claim 1, characterized in that: In step S5, when secondary drilling is performed, bentonite slurry is used for wall protection, and the slurry density is maintained at 1.1-1.2 g / cm³. If the pebble layer has extremely high permeability, causing slurry loss, a polymer additive is added to enhance the bonding strength.

3. The pile foundation construction technology applied to loose foundations according to claim 1, characterized in that: Premixed solid fluidized soil is composed of slag, cement, solidifying agent and water, with the mass ratio of each component being 100:8:2:

25.

4. The pile foundation construction technology applied to loose foundations according to claim 1, characterized in that: In step S4, before grouting the premixed solid fluidized soil, the wire mesh (1) is first rolled into a cylindrical shape, and the sections of wire mesh (1) are connected and lowered into the initial hole before grouting the premixed solid fluidized soil.

5. The pile foundation construction technology applied to loose foundations according to claim 4, characterized in that: The diameter of the cylindrical shape formed by the wire mesh (1) is 3-5 cm smaller than the diameter of the hole drilled initially.

6. The pile foundation construction technology applied to loose foundations according to claim 5, characterized in that: A locking element (2) is provided between two adjacent sections of the wire mesh (1). The locking element (2) includes a pair of locking plates (21) and a pair of locking hooks (22). The pair of locking plates (21) are arranged in layers. The locking hooks (22) are located on the opposite side of each locking plate (21) and are used to hook the upper and lower ends of the wire mesh (1). Each locking plate (21) is provided with a tooth (23) on the side opposite to the locking hook (22). The tooth (23) is used to pass through the opposite locking plate (21) and engage with the locking plate (21) for fixation.

7. The pile foundation construction technology applied to loose foundations according to claim 6, characterized in that: The closed openings of the two adjacent sections of wire mesh (1) are staggered.

8. The pile foundation construction technology applied to loose foundations according to claim 7, characterized in that: The lower end of the wire mesh (1) is provided with a rod (11), and the upper end is provided with a ring (12) for inserting the rod (11).

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