Method for the construction of a bored pile

Abstract

This invention discloses a method for constructing cast-in-place piles, relating to the field of cast-in-place pile construction technology. The method involves measuring and verifying the pre-set pile position to determine the center location of the pile and the closed layout position of its surrounding stress-relieving annular groove. An annular groove is formed along the closed layout position using a cutting and grooving device. The annular groove is then inspected and cleaned to remove loose soil, mud, and accumulated water. Closed-cell foamed concrete is injected into the annular groove to continuously fill it and form a low-modulus buffer zone. After filling, the annular groove is sealed and cured, and the cast-in-place pile is constructed after it reaches a predetermined stable state. This method utilizes a pre-formed continuous low-modulus buffer zone to isolate and absorb soil squeezing and disturbance during the drilling process, avoiding soil squeezing effects and localized stress concentration that could lead to lateral soil displacement, surface heave, settlement of adjacent buildings, or damage to underground pipelines.

Description

Technical Field

[0001] This invention relates to the field of cast-in-place pile construction technology, and in particular to a method for constructing cast-in-place piles. Background Technology

[0002] As a widely used foundation type in building construction, cast-in-place piles have undergone an evolution in construction technology from traditional driven precast piles to on-site bored and cast-in-place concrete piles. Early precast pile construction suffered from problems such as high noise, strong vibration, and significant soil displacement effects, making it difficult to adapt to densely populated urban areas and complex geological conditions. With the increasing demand for infrastructure construction, cast-in-place pile technology has gradually developed. Starting with manually excavated bored piles, it progressed to forward circulation and reverse circulation bored piles, and further evolved into rotary bored piles, long spiral bored piles, and casing-supported piles. These technologies, through mechanical drilling, mud or casing support, and underwater concrete pouring, have improved pile formation efficiency and adaptability, making cast-in-place piles widely used in high-rise buildings, bridges, ports, and soft soil foundation projects, becoming the mainstream form of modern pile foundations.

[0003] Currently, the construction of cast-in-place piles typically follows this process: First, site leveling, surveying and setting out, and pile location are conducted; then, a drilling rig is used to drill the hole, and depending on the soil conditions, either mud slurry circulation for slag removal or dry drilling is selected, with casing used as needed; after drilling, the hole is cleaned to control the thickness of the sediment, followed by the placement of the reinforcing cage and a second cleaning of the hole; finally, underwater continuous concrete pouring is performed using the tremie method to form the pile body. During construction, the stability of the borehole wall and the density of the concrete are maintained by controlling the mud properties, drilling parameters, and pouring speed to ensure the bearing capacity and integrity of the pile.

[0004] However, during the drilling process, the existing cast-in-place pile construction technology causes the drilling tools to squeeze, shear, and disturb the surrounding soil, resulting in significant soil squeezing effects and local stress concentration. This leads to problems such as lateral displacement of the soil, surface heave, settlement of adjacent buildings, and damage to underground pipelines, which have adverse effects on the surrounding environment and existing facilities. Summary of the Invention

[0005] The main objective of this invention is to propose a method for constructing cast-in-place piles, which aims to solve the technical problems in the prior art where, during the drilling process, the drilling tool squeezes, shears, and disturbs the surrounding soil, resulting in significant soil squeezing effects and local stress concentration, causing lateral displacement of the soil, surface heave, settlement of adjacent buildings, and damage to underground pipelines, which have adverse effects on the surrounding environment and existing facilities.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for constructing cast-in-place piles, comprising the following steps: The preset pile positions of the cast-in-place piles to be constructed are measured and verified to determine the center position of the cast-in-place piles to be constructed and the closed layout position of the stress relief annular grooves around them. An annular groove is formed along the closed layout using a cutting and grooving equipment. The annular groove was inspected and cleaned to remove loose soil, mud and water. Closed-cell foamed concrete is injected into the annular groove to continuously fill the annular groove and form a low-modulus buffer zone. After the annular groove is filled, it is sealed and cured, and after it reaches the predetermined stable state, the cast-in-place pile to be constructed is then constructed.

[0007] The technical solution of this invention determines the center position of the pile to be constructed and the closed layout position of the stress-relieving annular groove by measuring and verifying the preset pile position. The annular groove is then formed along the closed layout position using a cutting and trenching device. The annular groove is inspected and cleaned to remove loose soil, mud, and accumulated water. Closed-cell foamed concrete is injected into the annular groove to continuously fill it and form a low-modulus buffer zone. After filling, the annular groove is sealed and cured, and the pile to be constructed is constructed after it reaches a predetermined stable state. In practice, the coordinates of the center point of the pile to be constructed are first accurately calibrated through measurement and verification, and the closed trajectory of the annular groove is determined by extending outwards based on this coordinates, ensuring that the trajectory completely surrounds the pile position without any gaps. Subsequently, the cutting and trenching device is used to continuously cut soil along the closed trajectory to form an annular groove with a predetermined depth and width, thereby spatially separating the subsequent drilling area from the surrounding undisturbed soil. After initial segmentation, the newly formed annular groove is inspected and cleaned section by section to remove loose soil, mud sediment, and accumulated water from the bottom and walls of the groove. This ensures that the interior of the groove is clean, dense, and free of weak interlayers, providing a uniform contact surface for subsequent grout filling. Closed-cell foamed concrete is then continuously injected from one end of the annular groove until the grout fills the entire groove and overflows. Once it is confirmed that there are no voids, the injection is stopped, allowing the grout to solidify and harden within the groove, forming a continuous, closed low-modulus buffer zone. The elastic modulus of this buffer zone is much lower than that of the surrounding soil, enabling it to undergo significant volumetric compression deformation under pressure, thereby consuming and releasing stress. After the buffer zone has been sealed and cured to reach the predetermined strength and stability, the drilling operation for cast-in-place piles can be carried out in its central area. At this time, the lateral force and shear disturbance generated by the rotation and cutting of the drill bit first act on the soil inside the annular groove and then are transmitted to the low-modulus buffer zone. The buffer zone absorbs most of the energy through its own compression and blocks the stress wave from continuing to propagate to the surrounding soil, thus confining the drilling disturbance within the buffer zone. This invention allows for the sequential connection of the following steps during implementation: measuring and verifying the center position and closed layout position, cutting the trench, inspecting and cleaning, injecting closed-cell foam concrete to form a low-modulus buffer zone, and constructing the cast-in-place pile after sealing and curing. This enables the invention to utilize a pre-formed, continuous low-modulus buffer zone to isolate and absorb soil squeezing, shearing, and disturbance during the drilling process. This avoids the defects of existing cast-in-place pile construction techniques, where the drilling tools exert squeezing, shearing, and disturbance on the surrounding soil during drilling, leading to significant soil squeezing effects and localized stress concentration, which can cause lateral soil displacement, surface heave, settlement of adjacent buildings, or damage to underground pipelines. Furthermore, the closed, continuous filling method of the annular trench forms a complete and uninterrupted buffer zone, providing uniform and comprehensive stress release protection around the pile location, preventing adverse effects on the surrounding environment and existing facilities, and ensuring the safety and controllability of the construction process. The method is reasonable and effective. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0009] Figure 1 A flowchart of the cast-in-place pile construction method provided by the present invention.

[0010] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0011] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0012] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0013] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0014] This invention proposes a method for constructing cast-in-place piles.

[0015] Please see Figure 1 To facilitate understanding, this method for constructing cast-in-place piles includes the following steps: S100. Measure and verify the preset pile position of the pile to be constructed, and determine the center position of the pile to be constructed and the closed layout position of the stress relief annular groove around it.

[0016] Specifically, when measuring and verifying the pre-set pile positions of the piles to be constructed, a total station combined with a GPS positioning system is used to perform a secondary verification of the already marked pile positions on site, accurately determining the center position of the piles to be constructed. After determining this center position, the outer stress relief annular groove is delineated outward from this center, based on the pile diameter, the hardness of the soil layer, and the sensitivity of surrounding existing buildings or pipelines. The closed layout position is a complete closed annular trajectory to ensure that the subsequent buffering effect covers the main stress influence range.

[0017] S200. A ring-shaped groove is formed by using a cutting and grooving equipment along the closed layout position.

[0018] Specifically, the trenching equipment can be a tracked hydraulic trenching machine, whose milling head continuously cuts and advances along a predetermined closed trajectory, cutting and simultaneously removing the soil to form a trench with a width of 500-800 mm. During the cutting process, the milling speed and mud circulation volume are controlled to keep the trench walls upright and stable, preventing collapse. Once the annular trench is formed, it constitutes the spatial carrier for subsequent filling operations.

[0019] S300. Inspect and clean the annular groove to remove loose soil, mud and water from the groove.

[0020] Specifically, a high-pressure water gun is used in conjunction with an air-lift reverse circulation device to flush the tank walls and bottom, thoroughly removing loose soil, mud, and water residue from the cutting process. At the same time, an inclinometer and a depth sounding hammer are used to check the verticality of the tank walls and the elevation of the tank bottom. If necessary, irregularities are repaired to ensure that the tank is clean, dry, and meets the required geometric dimensions.

[0021] S400. Inject closed-cell foamed concrete into the annular groove to continuously fill the annular groove and form a low-modulus buffer zone.

[0022] Specifically, the closed-cell foamed concrete is prepared by mixing ordinary silicate cement, composite foaming agent, foam stabilizer, and appropriate amount of water-reducing agent according to a predetermined mix ratio, with a wet density controlled between 300 and 800 kg / m³, exhibiting good fluidity and a closed-cell structure. The slurry is continuously pumped from the bottom of the trench using a concrete pump truck until it fills the entire annular trench and slightly overflows the opening, thereby continuously filling the annular trench and forming a low-modulus buffer zone. The elastic modulus of the low-modulus buffer zone is significantly lower than that of the surrounding undisturbed soil and the subsequent cast-in-place pile concrete, enabling it to preferentially undergo compressive deformation.

[0023] S500. After the annular groove is filled, it is sealed and cured, and after it reaches the predetermined stable state, the cast-in-place pile to be constructed is constructed.

[0024] Specifically, geotextile is covered with soil on the top of the trench to prevent excessive moisture evaporation and external mechanical disturbance, and the curing period is no less than 7 days. After the low-modulus buffer zone reaches the predetermined stable state (the compressive strength measured on-site is not less than 0.8 MPa and the deformation tends to converge), conventional procedures such as drilling, cleaning, lowering of the reinforcing cage, and underwater concrete pouring of the cast-in-place piles to be constructed are carried out.

[0025] Because a low-modulus buffer zone is pre-formed around the pile location, the compression, shearing, and disturbance of the surrounding soil caused by the drilling tool during the subsequent pile drilling and concrete pouring process first act on the buffer zone. The buffer zone absorbs and releases most of the radial stress and displacement through its own compression deformation, which significantly reduces the stress concentration transmitted to the surrounding soil. This effectively mitigates adverse effects such as surface uplift, settlement of adjacent buildings, and deformation of underground pipelines, while also reducing quality defects such as borehole wall collapse and concrete segregation, improving pile integrity, and protecting the surrounding environment.

[0026] Of course, in some preferred embodiments, the cutting and grooving equipment is replaced by a chain cutter type grooving machine, whose chain cutters continuously cut along a closed layout position, suitable for cohesive soil layers, and the width of the formed annular groove can be adjusted to 250-400 mm. The closed-cell foamed concrete is mixed with polypropylene short fibers based on the original mix proportion, and the density is adjusted to 500-700 kg / m³ to further improve the toughness and crack resistance of the buffer zone. The predetermined stable state is determined by on-site monitoring using embedded strain gauges. When the strain rate of the buffer zone is lower than the set threshold, it is considered to have reached stability, and then the cast-in-place piles to be constructed are constructed. This embodiment also utilizes the preferential deformation of the low-modulus buffer zone to absorb soil displacement stress, further adapting to different soil conditions and ensuring the stability of the stress release effect.

[0027] In another embodiment, the radius of the closed-loop layout is dynamically adjusted based on the soil compression modulus determined by on-site static cone penetration tests, with a larger value used in soft soil areas and a smaller value used in hard soil areas. The depth of the annular groove exceeds the bottom elevation of the pile to be constructed by 1-2 m to form a closed buffer space at the bottom. The closed-cell foamed concrete is poured in two layers: the lower layer uses a lower density to enhance the bottom buffer, and the upper layer uses a slightly higher density to improve the top stability. Curing is performed by covering with a film and regularly spraying water to keep it moist. This embodiment, through more precise parameter matching, makes the low-modulus buffer zone more effective in mitigating the soil squeezing effect, further reducing the disturbance range to the surrounding soil.

[0028] In this embodiment, the center position of the pile to be constructed and the closed layout position of the stress-relieving annular groove are determined by measuring and verifying the preset pile position. The annular groove is then formed along the closed layout position using a cutting and trenching equipment. The annular groove is inspected and cleaned to remove loose soil, mud, and accumulated water. Closed-cell foamed concrete is injected into the annular groove to continuously fill it and form a low-modulus buffer zone. After filling, the annular groove is sealed and cured, and the pile to be constructed is constructed after it reaches a predetermined stable state. In practice, the coordinates of the center point of the pile to be constructed are first accurately calibrated through measurement and verification, and the closed trajectory of the annular groove is determined by extending outwards based on this coordinates, ensuring that the trajectory completely surrounds the pile position without any gaps. Subsequently, the cutting and trenching equipment is used to continuously cut soil along the closed trajectory to form an annular groove with a predetermined depth and width, thereby spatially separating the subsequent drilling area from the surrounding undisturbed soil. After initial separation, the newly formed annular groove is inspected and cleaned section by section to remove loose soil, mud sediment, and accumulated water from the bottom and walls of the groove. This ensures that the interior of the groove is clean, dense, and free of weak interlayers, providing a uniform contact surface for subsequent grout filling. Closed-cell foamed concrete is then continuously injected from one end of the annular groove until the grout fills the entire groove and overflows. Once no voids are confirmed, the injection is stopped, allowing the grout to solidify and harden within the groove, forming a continuous, closed low-modulus buffer zone. The elastic modulus of this buffer zone is much lower than that of the surrounding soil, enabling it to undergo significant volumetric compression deformation under pressure, thereby consuming and releasing stress. After the buffer zone has been sealed and cured to reach the predetermined strength and stability, the drilling operation for cast-in-place piles can be carried out in its central area. At this time, the lateral force and shear disturbance generated by the rotation and cutting of the drill bit first act on the soil inside the annular groove and then are transmitted to the low-modulus buffer zone. The buffer zone absorbs most of the energy through its own compression and blocks the stress wave from continuing to propagate to the surrounding soil, thus confining the drilling disturbance within the buffer zone. This invention allows for the sequential connection of the following steps during implementation: measuring and verifying the center position and closed layout position, cutting the trench, inspecting and cleaning, injecting closed-cell foam concrete to form a low-modulus buffer zone, and constructing the cast-in-place pile after sealing and curing. This enables the invention to utilize a pre-formed, continuous low-modulus buffer zone to isolate and absorb soil squeezing, shearing, and disturbance during the drilling process. This avoids the defects of existing cast-in-place pile construction techniques, where the drilling tools exert squeezing, shearing, and disturbance on the surrounding soil during drilling, leading to significant soil squeezing effects and localized stress concentration, which can cause lateral soil displacement, surface heave, settlement of adjacent buildings, or damage to underground pipelines. Furthermore, the closed, continuous filling method of the annular trench forms a complete and uninterrupted buffer zone, providing uniform and comprehensive stress release protection around the pile location, preventing adverse effects on the surrounding environment and existing facilities, and ensuring the safety and controllability of the construction process. The method is reasonable and effective.

[0029] In one embodiment, step S100 includes: S110. Verify the preset pile position of the cast-in-place pile to be constructed to obtain the pile center control point.

[0030] S120. Using the center control point of the pile as a reference, offset outward by a predetermined distance to determine the center line of the annular groove; S130. Perform closed layout along the center line of the annular groove; S140. Verify and correct the closed layout position to determine the center position of the cast-in-place pile to be constructed and the closed layout position of its surrounding stress release annular groove.

[0031] Specifically, firstly, a total station is used to verify the preset pile position on-site. The center control point of the pile is obtained by observing with both upright and reverse mirrors and taking the average value of multiple measurements. The plane coordinate error of this control point is controlled within 5 mm. Then, using this pile center control point as a reference, the center line of the annular groove is determined by offsetting outward by a predetermined distance. The predetermined distance is selected according to the pile diameter and soil conditions. For example, for a cast-in-place pile with a diameter of 800 mm, the offset is 1.0 meter in cohesive soil, or for a cast-in-place pile with a diameter of 1200 mm, the offset is 1.5 meters in sandy soil. Next, a closed layout is carried out along the center line of the annular groove using a steel ruler and a total station. A temporary control point is set every 2 meters to form a complete closed loop trajectory. Finally, the closed layout position is checked and corrected again with a total station to eliminate the closure error and finally determine the center position of the cast-in-place pile to be constructed and the precise closed layout position of the stress relief annular groove around it.

[0032] In this embodiment, a precise control point for the pile center is obtained by verifying the preset pile position. Using this as a reference, the centerline of the annular groove is determined by offsetting outwards by a predetermined distance. Closed layout and verification are then performed along the centerline to accurately define the relative position between the center of the cast-in-place pile and the surrounding stress-relieving annular groove. During subsequent drilling and concrete pouring, this annular groove forms a continuous stress-relieving space in the soil around the pile, absorbing and dissipating the lateral earth pressure generated by borehole compression and the self-weight of the concrete, effectively controlling the displacement and stress concentration of the surrounding soil. Precise positioning ensures a suitable distance between the annular groove and the pile body, avoiding both insufficient spacing leading to borehole instability or reduced pile quality, and excessive spacing weakening the stress-relieving effect. Compared to positioning methods without verification and correction, this step reduces local stress concentration or uneven soil disturbance caused by layout deviations, thereby reducing the impact of soil squeezing on the surrounding soil, improving the integrity of the cast-in-place pile, reducing quality defects such as necking and mud inclusion, and protecting adjacent buildings and underground pipelines from settlement or uplift damage.

[0033] In another embodiment, the verification of the pile center control point is completed using a real-time dynamic differential global positioning system. The coordinates of the control point are obtained by continuously observing for no less than 30 seconds and taking the average value. The predetermined distance is adjusted according to the soil compression modulus determined by the on-site static cone penetration test. A smaller offset of 0.6 to 0.8 meters is used for soft soil to enhance the release effect, and a larger offset of 1.6 to 2.0 meters is used for hard soil to reduce the disturbance to the soil around the pile. The closed layout is carried out using the polar coordinate method in conjunction with a laser rangefinder. The spacing between control points is adjusted to 1.5 meters, and the ring closure error is required not to exceed 8 mm during verification and correction. This implementation method can also accurately determine the center position of the cast-in-place pile and the closed layout position of the stress release ring groove, so that the ring groove can continuously play a stress dissipation role during construction, further reducing the soil squeezing effect and stress concentration of the surrounding soil, improving construction quality and reducing the impact on the surrounding environment.

[0034] In one embodiment, the predetermined distance is 20 to 50 cm, and the center line of the annular groove is concentric or approximately concentric with the center of the cast-in-place pile to be constructed.

[0035] Specifically, during construction, the center coordinates of the pile to be constructed are first determined using surveying equipment or a positioning system. Then, a ring-shaped trench is precisely excavated or formed within a distance of 20-50cm around this center, with the center line of the ring-shaped trench concentric or nearly concentric with the center of the pile. In practice, site surveying and layout are first conducted to calculate the precise distance range of 20-50cm. A dedicated positioning device or laser measuring instrument is used to mark the center point at the location of the ring-shaped trench, ensuring that the geometric center of the ring-shaped trench is completely or nearly aligned with the center line of the pile to be constructed. Subsequently, a drilling rig or dedicated excavation equipment is used to excavate the ring-shaped trench, controlling the excavation depth and width to match the predetermined distance of 20-50cm. After the ring-shaped trench is formed, the hole is cleaned to ensure no residual debris remains. After the hole is cleaned, underwater continuous concrete pouring is performed using the tremie method. The ring-shaped trench area acts as a buffer zone. During the pouring process, the soil stability within the ring-shaped trench is maintained by controlling the drilling parameters and pouring speed, avoiding direct disturbance to the central area of ​​the pile.

[0036] In this embodiment, the predetermined distance ensures that the distance between the annular groove and the center of the pile is within an effective control range, avoiding stress concentration caused by excessively close distances or insufficient buffering effect caused by excessively far distances. At the same time, the concentric arrangement ensures the uniform distribution and symmetry of the annular groove, effectively dispersing the vibration and stress wave propagation paths during construction, and reducing the soil squeezing effect and stress concentration of the surrounding soil.

[0037] In one embodiment, step S200 includes: S210. Align the drill bit with the starting point of the annular groove and drill down to the predetermined depth; S220. Start the high-pressure jet cutting system and rotate the drill bit; S230. Simultaneously lift or lower the drill bit in a rotating state to cut the soil and form a trench. S240. The construction is carried out segment by segment using an overlapping method until a closed and continuous annular groove is formed.

[0038] Specifically, the drill bit is aligned with the starting point of the annular groove and drilled to a predetermined depth. The starting point is selected on the closed layout line based on pre-completed measurements. The drill bit is slowly lowered while maintaining a vertical position. The predetermined depth is determined based on the soil layer distribution and the required isolation range of the annular groove, typically reaching the designed bottom elevation of the groove to ensure that subsequent cutting can cover the entire depth. The high-pressure jet cutting system is activated and the drill bit is rotated. The high-pressure jet cutting system continuously sprays high-pressure cutting media through nozzles on the drill bit, while the drill bit rotates at a stable speed, allowing the cutting media to act evenly on the surrounding soil in a circumferential direction, achieving initial scouring and loosening. While rotating, the drill bit is simultaneously raised to cut the soil and form the groove. During the raising process, jetting and rotation continue, with the raising speed coordinated with the jetting pressure, gradually cutting out regular groove segments from bottom to top. In another embodiment, a synchronous lowering of the drill bit is used to cut downwards from the ground surface to form the groove, suitable for situations where the surface soil is relatively dense or where the upper soil layer needs to be treated first. After completing the current trench segment, the drill bit is moved to the starting point of the next adjacent segment using a segmented overlapping method. This starting point overlaps with the ending point of the previous segment, with an overlap length sufficient to allow the soil in the adjacent trench segment to be fully cut and penetrated without leaving any residual partitions. Then, the drilling, jetting, rotation, and lifting or sinking cutting processes are repeated. This cycle is repeated until the beginning and end of each segment are connected, forming a closed and continuous annular trench.

[0039] In this embodiment, drilling to the predetermined depth with the drill bit aligned with the starting point ensures the accuracy of the annular trench's position and depth. The high-pressure jet cutting system, combined with the drill bit's rotation, primarily uses fluid scouring to cut the soil, avoiding the large lateral thrust generated by traditional mechanical excavation. The trenching process itself significantly reduces disturbance to the surrounding soil. Synchronous lifting or lowering ensures continuous and uniform cutting action along the depth direction, forming a trench with consistent width and relatively flat walls. The segmented overlapping method ensures complete connectivity between adjacent trench segments, resulting in a continuous, uninterrupted, and completely closed annular trench. During subsequent pile drilling and concrete pouring, this annular trench can confine the lateral displacement and stress changes of the soil caused by construction to the inside of the trench, effectively preventing the outward transmission of the soil squeezing effect, thereby reducing the impact of soil squeezing and stress concentration on the surrounding soil. Stable trenching quality helps ensure the integrity and bearing capacity of the pile body, while reducing disturbance to existing buildings, underground pipelines, and the surface environment, improving construction quality and protecting the surrounding environment.

[0040] In one embodiment, the annular groove satisfies at least one of the following grooving parameters: The width of the annular groove is 50-80 cm; The depth of the annular groove is 1 / 2 of the designed pile length; The injection pressure of the high-pressure jet cutting system is 20–35 MPa; The rotational speed of the drill bit is 8–15 r / min; The lifting or lowering speed is 0.05 to 0.10 m / min.

[0041] Specifically, the cutting energy of the high-pressure fluid is matched with the rhythm of the drill bit movement, resulting in a uniform and continuous cutting surface, a stable trench width within a set range, and a flat trench bottom concentric with the pile hole axis. This avoids local over-excavation causing loosening of the hole wall or under-excavation causing trench defects. The cast-in-place pile construction method of this application controls the annular trench forming process through the above-mentioned trenching parameters, ensuring precise trench geometry. During subsequent concrete pouring, the grout can fully fill the trench and tightly interlock with the surrounding undisturbed soil, significantly improving the pile side friction and overall bearing capacity. Simultaneously, the moderate injection pressure and slow lifting and sinking speed reduce impact disturbance to the hole wall, effectively suppressing the risk of hole collapse, shortening the trenching cycle, and improving construction continuity.

[0042] In some preferred embodiments, the width of the annular groove is 6.5 cm, the depth is still half the designed pile length, the injection pressure is 28 MPa, the drill rotation speed is 12 r / min, the lifting speed is 0.07 m / min, the cutting trajectory is more compact, the groove wall surface is smooth without protrusions, and there is no obvious weak layer at the interface between the concrete and the groove wall, further eliminating the problems of pile quality dispersion and insufficient bearing capacity caused by fluctuations in existing trenching parameters.

[0043] In one embodiment, step S300 includes: S310. Use a probe, depth measuring tool or visual inspection to check the closure, depth and width of the annular groove; S320. Remove the loose soil in the annular groove; S330. Remove the mud and accumulated water from the annular groove; S340. After cleaning, the tank is checked to ensure that the annular groove remains continuous and unobstructed.

[0044] Specifically, the steps for inspecting and cleaning the annular trench, removing loose soil, mud, and accumulated water, are as follows: First, use a probe, depth measuring tool, or visual inspection to check the closure, depth, and width of the annular trench: Construction personnel hold a probe and continuously slide it along the circumference of the annular trench towards the bottom to confirm that the trench forms a complete closed ring without any local collapse or interruption; simultaneously, use depth measuring tools such as a measuring rope or laser rangefinder to evenly distribute measuring points around the trench to measure the depth, verifying that the predetermined depth has been reached and that the deviation at each point is within the allowable range; then, visual inspection combined with a measuring tape is used to check whether the trench width is uniform and continuous, and whether there are any local inward or outward expansions in the trench walls. If poor closure, insufficient depth, or abnormal width is found during the inspection, immediate local adjustments are made. Next, the loose soil in the annular trough is removed: using manual shovels and small cleaning shovels, the loose soil is removed section by section along the bottom and walls of the trough. The removed soil is bagged and transported to a designated storage point to prevent it from falling back into the trough. For tightly adhered loose soil, a wire brush can be used to gently scrape it before shoveling, ensuring that the original dense soil layer is exposed on the trough walls and bottom. Then, the mud and accumulated water in the annular trough are drained: a temporary collection pit is set up in the low-lying area at the bottom of the trough, and a submersible pump or mud pump is used to pump out the accumulated water and mud and discharge it into a sedimentation tank. During the pumping process, the seepage of water on the trough walls is observed simultaneously, and temporary water-retaining embankments are added if necessary to prevent external water backflow. Finally, the trough is checked after cleaning: the closure is checked again using a sliding probe, the depth is checked again using a depth measuring tool, and the width is checked visually and with a measuring tape. Only after confirming that the annular trough is continuous and uninterrupted, that the depth and width meet the requirements, and that there are no residual impurities in the trough, and that it remains unobstructed, can the next process begin.

[0045] In this embodiment, inspection and cleaning systematically confirm the geometric integrity and internal cleanliness of the annular groove, thoroughly removing loose soil, mud, and accumulated water to ensure continuous and unobstructed flow within the groove. During subsequent concrete pouring, the concrete flows evenly along the groove wall and fully fills it, bonding tightly with the soil layer. This avoids mud inclusions or localized voids caused by residual impurities, thereby improving the density, integrity, and bearing capacity of the cast-in-place pile. This effectively solves the quality risks caused by insufficient inspection and cleaning of the annular groove in existing technologies.

[0046] In another embodiment, the inspection process prioritizes visual inspection to initially assess the overall appearance of the annular trench. This is followed by verification of the trench depth at key locations using depth sounding tools. For areas where visual inspection is insufficient to confirm closure, probe insertion is employed. When removing loose soil, high-pressure air is first used to blow away surface soil from the trench walls, followed by manual removal of the remaining loose material. Mud and water are drained using vacuum suction equipment in conjunction with a diversion channel for faster and more thorough emptying. During verification, the above combination of methods is repeated to confirm the trench's continuity and unobstructed flow. This implementation method also ensures the quality of the annular trench, resulting in uniform and dense concrete pouring, further enhancing the reliability and durability of the pile foundation construction.

[0047] In one embodiment, step S400 includes: S410. Convey closed-cell foamed concrete to the bottom of the annular trough; S420, The closed-cell foamed concrete is continuously lifted and filled into the tank from bottom to top; S430. Maintain continuous injection during the filling process to avoid forming cavities or broken bands; S440. Refill the annular groove with filler material at the localized sinking or material shortage location until the groove is filled and a continuous buffer zone is formed.

[0048] Specifically, an annular trench is continuously arranged around the outer perimeter of the cast-in-place pile. The trench has a predetermined depth and width, with its bottom being the lowest point and connecting to the surrounding soil or retaining wall. Prepared closed-cell foamed concrete is delivered to the bottom of the annular trench via a conveying pipeline. The pipeline outlet is positioned close to the trench bottom and can be moved or fixed circumferentially, allowing the grout to accumulate at the bottom. The grouting equipment is then activated, causing the closed-cell foamed concrete to rise from the bottom under continuous pressure. The grout, relying on its own fluidity and the lifting thrust, gradually fills the trench cross-section and propels upwards until it approaches the trench opening. Grouting is maintained continuously throughout the filling process. By controlling the pump flow rate and pressure, the grout remains in a flowing filling state, avoiding interruptions that could lead to initial setting, stratification, or the formation of cavities and breaks in the trench walls. At the same time, the slurry level in the tank is observed or monitored in real time. Once local subsidence, slurry drop or material shortage occurs, a slurry replenishment pipe is immediately inserted near the location for fixed-point replenishment. The replenishment amount is determined according to the missing volume until the entire annular tank is completely filled with slurry and the liquid surface is level with no visible gaps. After solidification, a continuous and complete low-modulus buffer zone is formed.

[0049] In this embodiment, when injecting closed-cell foamed concrete into the annular groove, the slurry is first transported to the bottom and then continuously lifted and filled from bottom to top. This gradual upward movement of the slurry effectively drives away residual air, moisture, and impurities within the groove, achieving dense, gapless continuous filling and avoiding the defects of traditional top-down injection, which easily traps gas and forms cavities. Maintaining continuous injection ensures that the slurry completes filling during its flow, preventing weak interfaces or material breaks due to interruptions, and guaranteeing the uniformity and overall continuity of the buffer zone in both the circumferential and vertical directions. Timely replenishment at locations of localized subsidence or material shortage addresses volume losses that may occur during construction due to minor soil disturbances, slurry bleeding and shrinkage, or localized deformation of the groove wall, ultimately ensuring that the annular groove is completely filled and forms an uninterrupted low-modulus buffer zone. The resulting continuous buffer zone can uniformly absorb and disperse the lateral pressure and uneven settlement deformation transmitted from the surrounding soil, reduce local stress concentration in the pile, provide flexible isolation, and reduce the risk of cracking, tilting, or damage to the pile caused by rigid contact. Simultaneously, the low modulus characteristics imparted by the closed-cell structure further enhance the buffering effect, thus solving the problems of buffer failure, subsequent settlement differences, or decreased isolation function caused by discontinuous filling in existing methods, and improving the construction quality and long-term stability of the cast-in-place pile. In another embodiment, multiple conveying pipes are uniformly arranged circumferentially along the bottom of the annular groove for simultaneous grout injection, achieving multi-point synchronous bottom-up jacking filling. This accelerates the overall filling speed and further reduces the risk of local cavities that may occur with single-point injection. Supplementary injection operations can also be carried out in sections using these pipes, ensuring the continuous uniformity of the buffer zone throughout the entire annular direction.

[0050] In one embodiment, the closed-cell foamed concrete satisfies at least one of the following performance parameters: The wet density is 300–800 kg / m³; The compressive strength is 0.3–1.5 MPa; The elastic modulus is 1 / 10 or less of the elastic modulus of the surrounding natural soil. The closed-cell ratio is higher than that of ordinary foamed concrete.

[0051] Specifically, the pile hole is first drilled and cleaned using conventional methods. Then, the grout is prepared: cement is used at a rate of 180–220 kg / m³, and an animal protein-based foaming agent is added. The mixture is then stirred at high speed to ensure uniform foam dispersion. The water-cement ratio is adjusted to 0.55–0.65, stabilizing the wet density of the freshly mixed grout at approximately 400 kg / m³. This grout is continuously poured into the pile hole from the bottom through a guide pipe. The grout surface rises at a rate of 2–3 m / hour within the annular groove, filling the pile hole from bottom to top due to its own fluidity. Because the wet density is only 1 / 5 to 1 / 4 that of traditional concrete, the lateral pressure on the hole wall during pouring is significantly reduced, making it less prone to soil extrusion or localized collapse, thus significantly minimizing construction disturbance. After hardening, the pile body is lightweight, resulting in less additional stress on the bearing stratum and effective control of post-construction settlement.

[0052] In some preferred embodiments, the closed-cell foamed concrete meets the requirement of a compressive strength of 0.3–1.5 MPa. During preparation, the water-cement ratio is adjusted to 0.6–0.75, and an appropriate amount of early-strength component is added. After the grout is poured, it is cured under natural conditions, and the compressive strength reaches 0.8–1.2 MPa after 28 days. This strength range is close to the in-situ strength of soft soil or silty soil, ensuring uniform stress transfer at the pile-soil interface after pouring, avoiding penetrating damage or stress concentration in soft soil due to excessive pile hardness. Slight lifting of the guide pipe during pouring ensures sufficient filling of the pile hole with the grout. After hardening, the pile can bear the superstructure load while maintaining deformation coordination with the surrounding soil, reducing the risk of interface shear failure.

[0053] Furthermore, the closed-cell foamed concrete meets the requirement that its elastic modulus is 1 / 10 or lower than that of the surrounding natural soil. The elastic modulus of the soil around the pile is first measured on-site (e.g., 15–25 MPa). During preparation, the foam volume content is increased to 55%–65%, reducing the elastic modulus of the hardened grout to below 1.5 MPa. After grouting, it naturally compacts under its own weight. The low modulus characteristic allows the pile to undergo similar deformations simultaneously when the soil is compressed, reducing the relative displacement between the pile and the soil, maintaining the skin friction around the pile, and improving overall stability. This parameter is particularly suitable for projects sensitive to differential settlement.

[0054] Furthermore, the closed-cell foamed concrete described herein achieves a higher closed-cell rate than ordinary foamed concrete. While the closed-cell rate of ordinary foamed concrete is typically between 50% and 70%, this application increases the amount of foam stabilizer and employs a secondary slow-mixing process to achieve a closed-cell rate exceeding 80%. This high closed-cell structure significantly reduces interconnected pores, allowing the water absorption rate of the hardened slurry to be controlled below 5%. When poured into strata with high groundwater levels, water is less likely to penetrate the slurry, resulting in minimal strength loss and ensuring the long-term durability of the pile.

[0055] It should be specifically and clearly stated that the performance parameters exemplified in this embodiment can be used individually or in any combination. When the following conditions are met simultaneously: wet density of 400 kg / m³, compressive strength of 1.0 MPa, elastic modulus not exceeding 1 / 10 of the soil mass, and closed-pore rate of 85%, the grout can form a complete pile body by continuous injection in one go after hole formation. This results in high construction efficiency, minimal disturbance to the surrounding soil, coordinated pile-soil deformation, and low risk of water absorption and softening. Thus, it comprehensively solves the disturbance, settlement, and durability problems caused by the high density, mismatched modulus, and insufficient closed-pore rate of traditional grouts. It is suitable for cast-in-place pile projects in soft soil, silt, and where deformation control is critical.

[0056] In one embodiment, step S500 includes: S510. After sealing the opening of the annular groove, the filled annular groove is moisturized or protected against water loss. S520. Avoid mechanical disturbance before the closed-cell foamed concrete reaches the predetermined initial strength. S530. After the annular groove forms a stable buffer zone, the pile to be constructed is sequentially subjected to hole drilling, hole cleaning, lowering of the reinforcing cage and concrete pouring operations to construct the pile to be constructed.

[0057] Specifically, after the annular groove is filled and cured, and the construction of the cast-in-place piles is carried out only after it reaches the predetermined stable state, the groove opening is first sealed. This is done by covering the opening with a precast cover plate or by backfilling and compacting the soil in layers to isolate it from external rainwater, debris, and air convection. After sealing, the filled annular groove is kept moist by covering the slurry surface with a damp geotextile or non-woven fabric and spraying water mist every 4-6 hours to replenish moisture, keeping the slurry surface moist and preventing moisture loss from the closed-cell foamed concrete. Before the closed-cell foamed concrete reaches the predetermined initial strength, i.e., before the compressive strength of the field-sampled test blocks reaches 0.4 MPa or the penetration resistance meets the initial setting index, a work isolation zone is demarcated, and any mechanical equipment is prohibited from approaching or causing vibration to avoid disturbing the unhardened skeleton structure of the slurry. After the grout in the annular groove has fully hardened to form a stable buffer zone, i.e., when the overall strength is stable and the elastic modulus meets the buffer isolation requirements, the subsequent operations for the cast-in-place piles to be constructed are carried out in sequence: First, the hole is formed by using a rotary drilling rig to slowly drill and remove soil according to the designed hole diameter and depth, while monitoring the verticality of the hole wall in real time and controlling the drilling speed to not exceed the bearing limit of the buffer zone; after the hole is formed, the hole is cleaned immediately by using positive circulation mud flushing or slag removal to remove the sediment at the bottom of the hole and the mud skin on the hole wall, ensuring that the thickness of the sediment does not exceed the specification limit; after the hole is cleaned and accepted, the reinforcing cage is lowered, and the prefabricated reinforcing cages in sections are vertically hoisted into the hole by a crane, welded together section by section and positioned to the design elevation to prevent the cage from tilting or floating; finally, concrete is poured by continuously pouring commercial concrete using the tremie method, controlling the tremie depth and pouring speed until the concrete surface exceeds the design pile top elevation by a certain height, thus completing the construction of the cast-in-place piles to be constructed.

[0058] In this embodiment, by sealing and curing the annular groove after filling, the groove opening is blocked to prevent external interference sources. Moisture protection ensures sufficient moisture in the closed-cell foam concrete throughout the hydration and hardening process, promoting the full reaction of the cementitious materials to form a uniform and dense hardened body, and avoiding volume shrinkage or pore connectivity disruption caused by water loss. Avoiding mechanical disturbance protects the fragile connection structure of the grout in the early stages of setting from external force damage, allowing it to harden completely and continuously into a stable buffer zone. This stable buffer zone supports and isolates the surrounding soil during subsequent drilling, reducing borehole wall collapse caused by drilling disturbance; maintains borehole wall integrity during the cleaning stage, facilitating thorough removal of sediment; provides guidance and restraint during the lowering of the reinforcing cage, preventing deviation; and buffers impact loads and prevents lateral concrete loss during concrete pouring, ensuring a dense and continuous pile body. This effectively solves the problem of buffer zone failure due to insufficient curing, improves the stability of the cast-in-place pile borehole and the quality of the pile body, and reduces the risk of construction defects such as borehole collapse and mud inclusion.

[0059] In some specific embodiments, after sealing the annular groove opening, the filled annular groove is protected against water loss. Specifically, a plastic film is fully laid on the top surface of the slurry and the edges are compacted to form a sealing layer, or a special concrete curing agent is sprayed to form a dense film on the surface, preventing internal moisture from evaporating outward. The remaining sealing and curing and subsequent construction steps are the same as in the previous embodiment, that is, mechanical disturbance is strictly avoided before the closed-cell foam concrete reaches the predetermined initial strength. After the annular groove forms a stable buffer zone, the drilling, cleaning, lowering of the reinforcing cage, and concrete pouring operations are carried out in sequence. This method can also maintain the internal moisture balance of the slurry, ensure uniform strength growth, and form a reliable and continuous stable buffer zone, thereby providing effective isolation support in each construction stage of the pile to be constructed, ensuring that the borehole wall does not collapse, the borehole is thoroughly cleaned, the reinforcing cage is successfully positioned, and the concrete is poured densely, thus improving the overall construction reliability and pile foundation bearing capacity.

[0060] In one embodiment, step S530 further includes: S531. Monitor the displacement of the pile tops of existing piles, ground settlement or heave, and lateral deformation of adjacent soil to obtain current monitoring data; S532. When the current monitoring data exceeds the preset control range, suspend subsequent construction and verify the continuity and filling integrity of the annular groove.

[0061] Specifically, after the annular trough forms a stable buffer zone, the drilling, cleaning, lowering of the reinforcing cage, and concrete pouring operations are carried out sequentially for the piles to be constructed. Monitoring is conducted simultaneously during this process. Specifically, observation markers are pre-set at the top of the completed piles, and a total station is used to periodically collect horizontal and vertical displacement readings on a fixed-cycle basis. Settlement observation points are set up on the ground surface within the construction influence area, and a precision level is used to measure elevation changes according to second-order leveling requirements to obtain settlement or uplift amounts. Inclinometer tubes are pre-embedded in the adjacent soil, and a sliding inclinometer is used to measure lateral displacement segment by segment along the tube. These three types of readings are recorded on-site and compared to form the current monitoring data. The pre-set control range is determined based on site geological parameters and allowable values ​​for pile foundation design; for example, the pile top displacement limit is 5mm, the surface settlement or uplift limit is 8mm, and the soil lateral deformation limit is 12mm. If any current monitoring data exceeds the corresponding limit, subsequent drilling and grouting operations must be immediately stopped, and a verification process initiated: First, ground-penetrating radar is used to continuously scan along the axis of the annular trench to identify any discontinuities, misalignments, or voids in the filling material; then, exploratory trenches are excavated or core samples are drilled in the suspected sections to directly check the continuous distribution and compaction of the filling material. If discontinuities or incomplete filling are found, supplementary grouting or refilling is carried out on the defective sections until both radar images and core sampling results show that the trench has returned to a continuous and compact state before subsequent construction can resume.

[0062] In this embodiment, the entire process from drilling to grouting is carried out after the annular groove forms a stable buffer zone. The annular groove pre-isolates the soil displacement stress and vibration transmission path generated by subsequent construction, thereby reducing direct disturbance to the existing piles and surrounding soil. Monitoring operations are conducted throughout the drilling, cleaning, reinforcement cage lowering, and concrete grouting stages, acquiring quantitative data on pile top displacement, surface settlement or heave, and lateral deformation of adjacent soil in real time, keeping the construction status continuously visible and controllable. Once the current monitoring data exceeds the preset control range, it is determined that the buffer effect may be weakening. Operations are then suspended, and the continuity and filling integrity of the annular groove are checked. Defects are accurately located and repaired through a combination of scanning and core sampling, ensuring that the buffer zone regains its complete isolation capacity. As a result, deformation is promptly contained within the allowable range, preventing excessive pile top displacement, abnormal surface heave, or further expansion of soil lateral displacement caused by buffer failure, thus ensuring the integrity of the existing piles and the stability of the surrounding environment. Compared to a one-time inspection only after construction is completed, this method embeds monitoring and verification into the construction process, enabling intervention at the stage when anomalies occur, significantly reducing construction risks and improving the overall quality and reliability of pile foundations.

[0063] In another embodiment, the monitoring operation is replaced by an automated data acquisition system: displacement gauges are installed on the tops of the completed piles, static levels are buried on the ground surface, and distributed fiber optic strain sensing cables are laid in the adjacent soil. Each sensor automatically collects data at a set frequency and wirelessly transmits it to the on-site monitoring terminal, generating the current monitoring data curve in real time. The preset control range is dynamically adjusted according to the test pile results; for example, the displacement limit is set in the range of 3–7 mm, and the settlement limit is set in the range of 6–10 mm. When the curve shows that any parameter is continuously approaching or exceeding the upper limit, the subsequent operation is immediately interrupted, and the verification process is changed to using ultrasonic cross-hole detection to check the uniformity of the wave velocity of the annular trench filling body, combined with the low-strain reflection wave method to determine the continuity of the trench. Sections with abnormal wave velocity or disordered reflection signals are repaired by directional grouting until the detection parameters return to normal. This implementation method also ensures that the buffer zone remains effective throughout the entire construction process, further shortens the abnormal response time and reduces human intervention errors, making deformation control more precise.

[0064] The above are merely exemplary embodiments of the present invention and do not limit the scope of the patent of the present invention. All equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of patent protection of the present invention.

Claims

1. A method for constructing cast-in-place piles, characterized in that, Includes the following steps: The preset pile positions of the cast-in-place piles to be constructed are measured and verified to determine the center position of the cast-in-place piles to be constructed and the closed layout position of the stress relief annular grooves around them. An annular groove is formed along the closed layout using a cutting and grooving equipment. The annular groove was inspected and cleaned to remove loose soil, mud and water. Closed-cell foamed concrete is injected into the annular groove to continuously fill the annular groove and form a low-modulus buffer zone. After the annular groove is filled, it is sealed and cured, and after it reaches the predetermined stable state, the cast-in-place pile to be constructed is then constructed.

2. The method for constructing cast-in-place piles as described in claim 1, characterized in that, The step of measuring and verifying the preset pile position of the pile to be constructed, and determining the center position of the pile and the closed layout position of its surrounding stress relief annular groove, includes: The preset pile positions of the cast-in-place piles to be constructed are checked to obtain the pile center control points; The center line of the annular groove is determined by offsetting a predetermined distance outward from the center control point of the pile. Perform closed-loop layout along the centerline of the annular groove; The closed layout position is checked and corrected to determine the center position of the cast-in-place pile to be constructed and the closed layout position of the stress relief annular groove around it.

3. The method for constructing cast-in-place piles as described in claim 2, characterized in that, The predetermined distance is 20-50cm, and the center line of the annular groove is concentric or nearly concentric with the center of the pile to be constructed.

4. The method for constructing cast-in-place piles as described in claim 3, characterized in that, The step of forming an annular groove by using a cutting and grooving device along the closed layout position includes: Align the drill bit with the starting point of the annular groove and drill down to the predetermined depth; Start the high-pressure jet cutting system and rotate the drill bit; The drill bit is simultaneously raised or lowered while rotating to cut the soil and form a trench. The process is carried out segment by segment using an overlapping method until a closed, continuous annular groove is formed.

5. The method for constructing cast-in-place piles as described in claim 4, characterized in that, The annular groove satisfies at least one of the following grooving parameters: The width of the annular groove is 50-80 cm; The depth of the annular groove is 1 / 2 of the designed pile length; The injection pressure of the high-pressure jet cutting system is 20–35 MPa; The rotational speed of the drill bit is 8–15 r / min; The lifting or lowering speed is 0.05 to 0.10 m / min.

6. The method for constructing cast-in-place piles as described in claim 5, characterized in that, The steps of inspecting and cleaning the annular groove to remove loose soil, mud, and accumulated water include: The closure, depth, and width of the annular groove are checked using a probe, depth measuring tool, or visual inspection. The loose soil within the annular groove is removed; The mud and accumulated water in the annular groove were removed; After cleaning, the tank is checked to ensure that the annular groove remains continuous and unobstructed.

7. The method for constructing cast-in-place piles as described in any one of claims 1 to 6, characterized in that, The step of injecting closed-cell foamed concrete into the annular groove to continuously fill the annular groove and form a low-modulus buffer zone includes: Closed-cell foamed concrete is conveyed to the bottom of the annular trough; The closed-cell foamed concrete is continuously lifted and filled into the tank from bottom to top; Maintain continuous injection during the filling process to avoid forming cavities or breaks in the filling band; Refill the annular groove with filler material at the localized subsidence or material shortage locations until the groove is filled and a continuous buffer zone is formed.

8. The method for constructing cast-in-place piles as described in claim 7, characterized in that, The closed-cell foamed concrete meets at least one of the following performance parameters: The wet density is 300–800 kg / m³; The compressive strength is 0.3–1.5 MPa; The elastic modulus is 1 / 10 or less of the elastic modulus of the surrounding natural soil. The closed-cell ratio is higher than that of ordinary foamed concrete.

9. The method for constructing cast-in-place piles as described in any one of claims 1 to 6, characterized in that, The steps of sealing and curing the filled annular groove, and constructing the cast-in-place pile after it reaches a predetermined stable state, include: After sealing the opening of the annular groove, the filled annular groove is protected against moisture retention or water loss. Avoid mechanical disturbance before the closed-cell foamed concrete reaches the predetermined initial strength. After the annular groove forms a stable buffer zone, the pile to be constructed is sequentially subjected to drilling, hole cleaning, lowering of the reinforcing cage, and concrete pouring operations to construct the pile to be constructed.

10. The method for constructing cast-in-place piles as described in claim 9, characterized in that, After the annular groove forms a stable buffer zone, the steps of constructing the pile to be grouted, including drilling, cleaning, lowering the reinforcing cage, and pouring concrete, further include: Monitoring operations are conducted on the displacement of the pile tops of existing piles, ground settlement or heave, and lateral deformation of adjacent soil to obtain current monitoring data; When the current monitoring data exceeds the preset control range, subsequent construction is suspended, and the continuity and filling integrity of the annular groove are checked.

Images