Pile-forming method for round gravel and pebble stratum

Abstract

This invention relates to the field of jet grouting technology, specifically disclosing a method for pile construction in gravelly sand and pebble strata. The method includes: leveling the site to form a foundation that meets bearing capacity requirements; installing a mixing pile machine on the foundation; controlling the mixing pile machine to rotate and lower its drill rod to drill a hole in the foundation and spray water; controlling the mixing pile machine to rotate and raise its drill rod to perform a first grouting and air jetting on the drill hole; controlling the mixing pile machine to rotate and lower its drill rod to agitate the grout in the drill hole and spray air; controlling the mixing pile machine to rotate and raise its drill rod to perform a second grouting and air jetting on the drill hole, consolidating to form a pile body; moving the drill rod of the mixing pile machine and repeating the above steps to form multiple pile bodies. This method for pile construction in gravelly sand and pebble strata improves construction efficiency and quality.

Description

Technical Field

[0001] This invention relates to the field of jet grouting technology, and in particular to a method for pile construction in gravel and sand strata. Background Technology

[0002] Jet grouting piles achieve good construction results in general strata such as plain fill, miscellaneous fill, cohesive soil, and sand. However, when encountering complex strata such as gravel layers, sand and gravel layers, or boulders, they are prone to drilling difficulties, hole formation problems, or pile position deviations, resulting in slow construction speed. Due to the influence of large-diameter sand and gravel, high-pressure jet grouting piles may experience pile formation interruptions, inconsistent drilling rates, and uneven or insufficient forced mixing of the injected grout with the cut soil particles, leading to poor pile quality. Therefore, there is room for further improvement in the quality and efficiency of jet grouting pile construction in gravel and sandy gravel strata. Summary of the Invention

[0003] The purpose of this invention is to provide a pile-forming method for gravel and sand strata, which can improve construction efficiency and quality.

[0004] To achieve the above objectives, the present invention provides a method for pile construction in gravel and pebble strata, comprising: The site is leveled to form a foundation that meets the bearing capacity requirements; Install a mixing pile machine on the foundation; Control the mixing pile machine to rotate and lower its drill rod to drill holes in the foundation and spray water; Control the mixing pile machine to rotate and raise its drill rod to perform a single grouting and air jetting operation on the borehole; The mixing pile machine is controlled to rotate and lower its drill rod to mix the slurry in the borehole and spray air. The mixing pile machine is controlled to rotate and rise its drill rod to perform secondary grouting and air jetting on the borehole, thereby consolidating and forming a pile body. The drill rod of the mixing pile machine is moved, and the above steps are repeated to form multiple piles.

[0005] In some embodiments, the hydraulic pressure of the sprayed slurry and the sprayed water is greater than or equal to 20 MPa.

[0006] In some embodiments, the drill pipe rotates upward at a speed of 10-20 cm / min.

[0007] In some embodiments, the spraying is cement slurry sprayed, and the water-cement ratio of the cement slurry is 1.0-1.5.

[0008] In some embodiments, repeating the above steps to form a plurality of piles includes: the plurality of piles forming a first row of consolidated bodies and a second row of consolidated bodies, the two rows of consolidated bodies forming a water-stop curtain.

[0009] In some embodiments, the piles of the first row of consolidated bodies are distributed at equal intervals, and the piles of the second consolidated body are distributed at equal intervals.

[0010] In some embodiments, the pile diameter of the pile body is a, and the pile spacing of the first row of consolidated bodies and the pile spacing of the second row of consolidated bodies are both b, then a / b = 0.6-0.8 is satisfied.

[0011] In some embodiments, the pile body of the second consolidated body is constructed after the pile body of the first consolidated body has been consolidated.

[0012] In some embodiments, the piles of the first row of consolidated bodies and the piles of the second row of consolidated bodies are staggered and closely fitted together.

[0013] This invention provides a pile-forming method for gravel and sand strata, which has the following advantages compared with the prior art: By leveling the site to form a foundation that meets the bearing capacity requirements, a mixing pile machine is installed on the foundation. The machine is controlled to rotate and lower its drill rod to drill a hole in the foundation while spraying water. Then, the drill rod is controlled to rotate and rise to perform a first grouting and air jetting on the drill hole. Next, the drill rod is controlled to rotate and lower to agitate the grout within the drill hole while spraying air. Finally, the drill rod is controlled to rotate and rise to perform a second grouting and air jetting on the drill hole, consolidating the grout to form a pile. The drill rod of the mixing pile machine is moved, and the above steps are repeated to form multiple piles. This secondary grouting and air jetting ensures uniform mixing of the grout and the soil, improving pile quality, reducing the risk of drill bit jamming, and increasing construction efficiency. Attached Figure Description

[0014] Figure 1 This is a flowchart of a pile-forming method for gravel and sand strata provided for some embodiments of the present invention.

[0015] Figure 2 This is the elevation view of the first row of solidified structures.

[0016] Figure 3 This is an elevation view of the first and second rows of consolidated structures. Detailed Implementation

[0017] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0018] It should be understood that in the description of this application, the terms "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. That is, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, unless otherwise stated, "a plurality of" means two or more.

[0019] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0020] like Figure 1 As shown in the embodiment of the present invention, the pile construction method for gravel and sand strata includes the following steps: S1. Level the site to form a foundation that meets the bearing capacity requirements. Specifically, remove surface debris and boulders, and use equipment such as road rollers to level and compact the construction area. The leveled site should be able to support heavy equipment such as the mixing pile machine to ensure that the mixing pile machine does not sink or tilt during movement and operation. In addition, for local weak areas, replacement or reinforcement treatment is required.

[0021] S2. Install a mixing pile machine on the foundation; specifically, the drill rod of the mixing pile machine has a core tube for the cement slurry, water and air required for high-pressure jet grouting piles. The top of the drill rod has a reserved cement delivery pipe inlet to ensure that the back-end pipeline can be connected to the core tube of the drill rod. At the same time, the outer wall of the drill rod has spiral blades to further and fully mix the soil.

[0022] S3. Control the mixing pile machine to rotate and lower its drill rod to drill holes in the foundation and spray water; in this way, the high-pressure water jet pre-cuts and loosens the strata, reduces drill bit wear, helps the drill rod to smoothly penetrate the gravel and pebble layers, and at the same time partially fills the pores, creating favorable conditions for subsequent grouting.

[0023] S4. Control the mixing pile machine to rotate and raise its drill rod to perform a grouting and air jetting operation on the borehole. This is the first injection of cement grout during the drill rod's lifting process, while the agitation of compressed air allows the grout to mix more thoroughly and evenly with the formation, especially forming preliminary cementation in the gaps between pebbles. Specifically, use P.O42.5 grade or higher cement to prepare the cement grout.

[0024] S5. Control the mixing pile machine to rotate and lower its drill rod to mix the grout in the borehole and spray air; in this way, without spraying grout, the preliminary mixture formed by the first grouting is strongly sheared and mixed by the re-descent and mixing of the drill rod, breaking up any possible grout clumps, and the grout is more evenly wrapped and combined with the formation particles (especially large-diameter pebbles) by air jet mixing.

[0025] S6. Control the mixing pile machine to rotate and rise its drill rod to perform secondary grouting and air jetting on the borehole, consolidating and forming the pile body; in this way, the remaining cement grout is added to ensure that the total cement content fully meets the design requirements. The secondary air jet mixing further homogenizes the grout in the pile body, promotes pile compaction, reduces porosity, and forms a complete and continuous pile body.

[0026] S7. Move the drill rod of the mixing pile machine and repeat the above steps to form multiple piles. Optionally, the machine can be moved and constructed in the order determined by the construction organization design (such as skip-driving method, continuous curtain method, etc.).

[0027] Based on the above-mentioned pile construction method, the grout and stratum are mixed evenly through secondary grouting and air jetting, which can improve the quality of the pile body, reduce the risk of stuck drill bit, and improve construction efficiency.

[0028] In some embodiments, for complex gravel and pebble layers with extremely high density and containing large-diameter boulders or rock fragments, the hydraulic pressure for grouting and water spraying is greater than or equal to 20 MPa. This allows for the effective cutting, crushing, and pre-dispersing of large particles and hard nodules in the formation via ultra-high pressure jets, significantly reducing drill bit wear and drilling torque. High-pressure grouting ensures that the cement slurry can penetrate and fill the pores of the dense formation with sufficient kinetic energy, achieving forced mixing of the slurry and the formation, overcoming the difficulty of slurry diffusion under conventional pressure. Grouting and water spraying are achieved by equipping the system with a high-power, high-pressure plunger pump, high-pressure resistant drill pipes, delivery pipelines, and nozzles.

[0029] In some embodiments, for projects with extremely high requirements for pile uniformity, strength, and water tightness, or when using grout with a high water-cement ratio, the drill rod rotation speed is 10-20 cm / min. This control of the drill rod's lifting speed, combined with a constant rotation speed, significantly increases the number of mixing operations and grout injection time per unit soil layer. This ensures the cement grout and soil particles are thoroughly mixed and integrated, eliminating mixing blind spots, which is crucial for forming a uniform, dense pile body free of weak interlayers.

[0030] In some embodiments, for sand and gravel layers with low original water content and high water absorption, or in cases where the grout requires excellent fluidity for long-distance penetration and filling, the grouting is done with cement grout, and the water-cement ratio of the cement grout is 1.0-1.5. This higher water-cement ratio significantly enhances the fluidity of the grout, facilitating its diffusion, penetration, and encapsulation of gravel in loose, porous formations. However, it is necessary to control the drill rod lifting speed and extend the mixing time to ensure sufficient strength of the final solidified body, avoiding insufficient pile strength due to excessive moisture.

[0031] like Figure 2 and Figure 3 As shown, in some embodiments, repeating the above steps to form multiple piles includes: multiple piles forming a first row of consolidated bodies and a second row of consolidated bodies, the two rows of consolidated bodies forming a water-stop curtain. This is suitable for projects requiring extremely high water-stopping effects, such as foundation pit support and dam foundation seepage prevention.

[0032] In some embodiments, the piles of the first row of consolidated bodies are distributed at equal intervals, and the piles of the second row of consolidated bodies are also distributed at equal intervals. Thus, the piles of both the first and second rows of consolidated bodies are arranged at equal intervals, ensuring the uniformity of the curtain wall at all points.

[0033] In some embodiments, the pile diameter is 'a', and the pile spacing of the first row of consolidated bodies and the pile spacing of the second row of consolidated bodies are both 'b', thus satisfying a / b = 0.6-0.8. This ensures a radial overlap of 20%-40% between adjacent piles, which is crucial for forming a continuous, leak-free, and weak-link waterstop wall.

[0034] In some embodiments, the construction of the second row of consolidated piles is carried out after the first row of consolidated piles has been consolidated. This ensures that the construction of the second row of consolidated piles proceeds only after the cement-soil of the first row of consolidated piles has reached a certain initial setting strength. This avoids quality disturbance to adjacent unconsolidated piles caused by subsequent pile construction.

[0035] In some embodiments, the piles of the first row of consolidated bodies are staggered and closely fitted together with the piles of the second row of consolidated bodies. The pile positions of the second row of consolidated bodies are staggered (in a quincunx pattern) with the pile positions of the first row of consolidated bodies, and the sides of the two rows of piles are in close contact with each other. This staggered and closely fitted arrangement ensures that the second row of piles precisely interlocks with the gaps in the first row of piles, completely sealing off any possible seepage channels in a two-dimensional plane and maximizing the water-stopping effect.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method of piling in a round gravel and pebble formation, characterized in that, include: The site is leveled to form a foundation that meets the bearing capacity requirements; Install a mixing pile machine on the foundation; Control the mixing pile machine to rotate and lower its drill rod to drill holes in the foundation and spray water; Control the mixing pile machine to rotate and raise its drill rod to perform a single grouting and air jetting operation on the borehole; The mixing pile machine is controlled to rotate and lower its drill rod to mix the slurry in the borehole and spray air. The mixing pile machine is controlled to rotate and rise its drill rod to perform secondary grouting and air jetting on the borehole, thereby consolidating and forming a pile body. The drill rod of the mixing pile machine is moved, and the above steps are repeated to form multiple piles.

2. The pile driving method for gravel and sand strata according to claim 1, characterized in that, The hydraulic pressure of the sprayed slurry and the sprayed water is greater than or equal to 20 MPa.

3. The method of pile founding in round gravel-pebble formations according to claim 1, characterized in that, The drill pipe rotates and rises at a speed of 10-20 cm / min.

4. The method of pile founding in round gravel-pebble-sandy ground according to claim 1, characterized in that, The sprayed grout is a cement grout, and the water-cement ratio of the cement grout is 1.0-1.

5.

5. The method of pile founding in round gravel-pebble formations according to claim 1, characterized in that, Repeating the above steps to form multiple piles includes: the multiple piles forming a first row of consolidated bodies and a second row of consolidated bodies, and the two rows of consolidated bodies forming a water-stop curtain.

6. The pile construction method for gravel and sand strata according to claim 5, characterized in that, The piles in the first row of consolidated bodies are distributed at equal intervals, and the piles in the second row of consolidated bodies are distributed at equal intervals.

7. The method according to claim 6, wherein, The pile diameter is a, the pile spacing of the first row of consolidated bodies and the pile spacing of the second row of consolidated bodies are both b, then a / b = 0.6-0.

8.

8. The method of pile founding in round gravel-pebble formations according to claim 5, characterized in that, After the pile body of the first consolidated body is consolidated, the pile body of the second consolidated body will be constructed.

9. A method of piling in a round boulder and gravel formation according to any one of claims 5-8, characterized in that, The piles of the first row of consolidated bodies are staggered and closely attached to the piles of the second row of consolidated bodies.

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