An open-type post-grouting construction technology for cast-in-place piles using a combination of sludge sedimentation and crushed stone.

Abstract

This invention relates to an open-type post-grouting construction process for cast-in-place piles using a combination of sludge sedimentation and crushed stone. The process includes the following steps: drilling holes using expansive cement slurry with a relative density of 1.3–1.5; using a slurry flocculant to settle large suspended sludge particles to the bottom of the pile hole, followed by the addition of graded crushed stone; casting the cast-in-place pile; and injecting grout into the soil-rock mixture. The beneficial effects of this invention are: using high-density sludge to improve the quality of the sludge wall protection, thereby improving the quality of the cast-in-place pile; employing methods to promote sludge sedimentation to accelerate hole cleaning; and addressing the problem of difficult-to-remove sludge generated during high-density sludge wall protection by adding graded crushed stone, which mixes the sludge and crushed stone to form a soil-rock mixture, improving its groutability. Through the open-type post-grouting process, the loose characteristics of the soil-rock mixture allow the grout to easily penetrate it, making the soil at the bottom of the cast-in-place pile denser and increasing the end-bearing area, thus significantly improving the bearing capacity of the cast-in-place pile.

Description

Technical Field

[0001] This invention belongs to the field of efficient pile formation for cast-in-place piles in soft soil layers, and particularly relates to an open post-grouting construction process for cast-in-place piles that combines mud sedimentation and crushed stone, which is applicable to post-grouting cast-in-place pile construction. Background Technology

[0002] Cast-in-place piles are a type of foundation with high bearing capacity, widely used in super high-rise buildings, long-span bridges and marine engineering. With the expansion of engineering fields, adverse geological conditions such as weak subsurfaces are inevitable, which puts forward higher requirements for the efficient pile formation and effective bearing capacity of cast-in-place piles.

[0003] Cast-in-place piles under adverse geological conditions face a greater risk of borehole collapse and cross-hole formation during the drilling stage. In particular, the traditional construction process of cast-in-place piles in soft strata is prone to problems such as borehole wall damage and mud accumulation at the pile bottom. Existing technologies have proposed effective mitigation solutions by increasing the density of the wall-protecting mud and shortening the cleaning time. However, the resulting problems, such as excessive mud sedimentation, can also lead to integrity defects in cast-in-place piles prepared by conventional construction methods. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an open-type post-grouting construction process for cast-in-place piles that combines mud sedimentation and crushed stone.

[0005] This open-type post-grouting construction process for cast-in-place piles, which combines sludge sedimentation with crushed stone, includes the following steps:

[0006] Step 1, Hole Formation: Drill holes for the cast-in-place piles using expansive cement grout with a relative density of 1.3 to 1.5.

[0007] Step 2, Hole Cleaning: Large particles of suspended mud are sludge settled into the bottom of the pile hole using mud flocculant, and then graded crushed stone is added into the pile hole to mix with the mud at the bottom of the pile hole to form a soil-rock mixture.

[0008] Step 3, Pile Formation: Grouting pipes are pre-installed on the steel cage of the cast-in-place pile, and then lowered into the pile hole for casting. The bottom of the cast-in-place pile is supported above the soil-rock mixture.

[0009] Step 4, Open-type post-grouting: Grout is injected into the soil-rock mixture through the grouting pipe to compact the soil-rock mixture and enlarge the bottom end of the cast-in-place pile.

[0010] Preferably, in step two, the pile hole is cleaned by circulating water. The circulating water contains a mud flocculant, which is a high-molecular-weight polymer precipitant or an inorganic flocculant, at a dosage of 0.5–3 kg / m³. 3 The circulating water cleaning process removes some of the scum from the pile hole, while some of the remaining large particles of suspended mud settle to the bottom of the pile hole.

[0011] Preferably, in step two, the thickness of the graded crushed stone is 0.2 to 0.5 m, the maximum particle size is less than or equal to 6 cm, and the soil-rock mixture formed by the graded crushed stone and sludge has a porous structure inside.

[0012] Preferably, in step four, the grout penetrates into the porous structure inside the soil-rock mixture through infiltration, thereby achieving compaction of the soil-rock mixture.

[0013] Preferably, in step three, the outlet end of the grouting pipe extends into the soil-rock mixture area.

[0014] Preferably, in step one, a sleeve is installed inside the pile hole after drilling; in step three, after the reinforcing cage of the cast-in-place pile is lowered into the pile hole, the sleeve is pulled out, and then the cast-in-place pile is poured.

[0015] The beneficial effects of this invention are:

[0016] 1) This invention first uses high-density mud to improve the quality of mud wall protection, thereby improving the quality of cast-in-place piles. It adopts a method to promote mud sedimentation to accelerate hole cleaning. In order to address the problem that the mud residue generated during high-density mud wall protection is difficult to remove, graded crushed stone is added to mix the mud residue with the crushed stone to form a soil-rock mixture, which improves its groutability and facilitates subsequent open-type post-grouting. Through the open-type post-grouting process, the loose characteristics of the soil-rock mixture are utilized to make the grout easily penetrate into it, making the soil at the bottom of the cast-in-place pile dense and increasing the end bearing area, which greatly improves the bearing capacity of the cast-in-place pile.

[0017] 2) This invention uses mud flocculant added to circulating water to settle large particles of suspended mud that cannot be carried away by conventional circulating water flushing, and utilizes the loose and porous characteristics of soil-rock mixture to facilitate open-type post-grouting, thereby enhancing the pouring effect of grout at the bottom of the cast-in-place pile. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention;

[0019] Figure 2 This is a schematic diagram showing the pile hole after punching and installing the sleeve.

[0020] Figure 3 A schematic diagram showing the mud sedimentation process followed by the addition of graded crushed stone.

[0021] Figure 4 This is a schematic diagram of a pre-embedded grouting pipe;

[0022] Figure 5 This is a schematic diagram of open-type post-grouting. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0024] Example 1

[0025] As one example, such as Figure 1 As shown, this open-type post-grouting construction process for cast-in-place piles using a combination of sludge sedimentation and crushed stone includes the following steps:

[0026] Step 1, Hole Formation: (e.g.) Figure 2 As shown, the pile holes for cast-in-place piles are drilled using high-density expansive cement grout. The high density corresponds to a relative density of 1.3–1.5, which increases the pressure of the grout on the hole wall and prevents hole collapse. A sleeve is then installed inside the drilled pile hole.

[0027] Step 2, Clean the hole: (e.g.) Figure 3 As shown, large particles of suspended mud are sunk to the bottom of the pile hole using mud flocculant.

[0028] The mud flocculant can be a high-molecular-weight polymer precipitant, PAM (polyacrylamide), at a dosage of 0.5-3 kg per cubic meter. For highly expansive cement slurry, inorganic flocculants such as aluminum chloride (AlCl3) combined with cellulose-based materials can also be used to promote the formation of small lumps in the mud. A mud test must be conducted before implementation.

[0029] After large particles of suspended mud sink to the bottom of the pile hole, graded crushed stone is added to the bottom of the pile hole, so that the graded crushed stone and mud mix at the bottom of the pile hole to form a soil-rock mixture.

[0030] This means that it is not necessary to completely remove the mud generated during the hole cleaning process, thus solving the problem of mud debris caused by the use of high-density mud. The soil-rock mixture formed by graded crushed stone and mud has a relatively rich and multi-layered pore structure, thus having good groutability.

[0031] Step 3, Pile Construction: (e.g., ...) Figure 4 As shown, a grouting pipe is pre-installed on the steel cage of the cast-in-place pile. After being hoisted into the pile hole, the sleeve is pulled out and the cast-in-place pile is poured. The bottom of the cast-in-place pile is supported above the soil-rock mixture to ensure that the outlet end of the grouting pipe extends into the soil-rock mixture area. After the cast-in-place pile is quality inspected, step four is implemented.

[0032] Step 4, Open-type post-grouting: (e.g.) Figure 5As shown, grout is injected into the soil-rock mixture through a grouting pipe. This utilizes the loose soil layer at the bottom of the pile caused by the sediment at the pile bottom. The grout penetrates into the void structure inside the soil-rock mixture, which not only compacts the soil-rock mixture but also expands the bottom end of the cast-in-place pile, compacts the surrounding soil, and further improves the bearing capacity of the cast-in-place pile foundation, thus achieving efficient pile formation under adverse geological conditions.

[0033] Example 2

[0034] As another embodiment, this embodiment two, based on embodiment one, proposes an open-type post-grouting construction process for cast-in-place piles that combines mud sedimentation and crushed stone, and a specific method for sinking large particles of suspended mud sediment into the bottom of the pile hole using mud flocculant.

[0035] In step two, the pile hole is cleaned by circulating water. Mud flocculant is added to the circulating water. The scum generated during the cleaning process is discharged and treated by conventional circulation methods. The large particles of suspended mud remaining during the cleaning process settle to the bottom of the pile hole under the action of cellulose. By adding graded crushed stone into the pile hole, the graded crushed stone and mud can be mixed at the bottom of the pile hole to form a soil-rock mixture.

[0036] The crushed stone should be well-graded, with a maximum particle size not exceeding 6 cm. It should be introduced using a guide pipe after the borehole cleaning is basically completed to prevent separation of the crushed stone from the mud. The crushed stone must not be thrown directly from the top of the borehole to avoid damaging the borehole wall. The thickness of the crushed stone layer should be 0.2–0.5 m, and the greater the density of the mud, the more crushed stone should be added.

[0037] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiment 1 can be referred to each other, and will not be repeated in this application.

[0038] Example 3

[0039] As another embodiment, based on embodiments one and two, this embodiment proposes an open-type post-grouting construction process for cast-in-place piles that combines mud sedimentation and crushed stone. It is also possible to eliminate the use of mud flocculants to settle large-particle suspended mud, that is, to clean and discharge it through conventional means, and simply to put graded crushed stone into the bottom of the pile hole. In step four, the grout enters the pore structure of the graded crushed stone through permeation.

[0040] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiments 1 and 2 can be referred to each other, and will not be repeated in this application.

[0041] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

Claims

1. A post-grouting construction process for open-type cast-in-place piles using a combination of sludge sedimentation and crushed stone, characterized in that, Includes the following steps: Step 1, Hole Formation: Drill the pile hole for the cast-in-place pile using expansive cement grout with a relative density of 1.3 to 1.5; install a sleeve inside the drilled pile hole. Step 2, Hole Cleaning: Large particles of suspended mud are sludge settled into the bottom of the pile hole using mud flocculant, and then graded crushed stone is added into the pile hole to mix with the mud at the bottom of the pile hole to form a soil-rock mixture. The pile hole is cleaned by circulating water containing mud flocculant, which is either a high-molecular polymer precipitant or an inorganic flocculant, at a dosage of 0.5–3 kg / m³. 3 The circulating water cleaning process removes some of the scum from the pile hole, while some of the remaining large particles of suspended mud settle to the bottom of the pile hole. The thickness of the graded crushed stone is 0.2-0.5m, and the maximum particle size is less than or equal to 6cm. The soil-rock mixture formed by the graded crushed stone and mud has a porous structure inside. Step 3: Pile construction: A grouting pipe is pre-installed on the reinforcing cage of the cast-in-place pile. After being hoisted into the pile hole, the cast-in-place pile is poured. The bottom of the cast-in-place pile is supported above the soil-rock mixture. The outlet end of the grouting pipe extends into the soil-rock mixture area. After the reinforcing cage of the cast-in-place pile is hoisted into the pile hole, the sleeve is pulled out, and then the cast-in-place pile is poured. Step 4, Open-type post-grouting: Grout is injected into the soil-rock mixture through the grouting pipe to compact the soil-rock mixture and enlarge the bottom end of the grouting pile; the grout penetrates into the void structure inside the soil-rock mixture through the infiltration process, thereby achieving the compaction of the soil-rock mixture.

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