A method for agitating pile construction and a construction device thereof

Abstract

This invention discloses a method and equipment for cement-soil mixing and pile driving. The method includes eight steps: equipment setup, drilling, main pile hole drilling, enlarging the diameter of the outer core pile, enlarging the bottom of the outer core pile, drilling again after diameter enlargement, pile driving, and pile driving completion. The equipment includes a mixing drill rig and auxiliary pile driving equipment. The mixing drill rig includes a drive unit, drill rod, and drill bit. The drill bit includes a fixed drill bit and an extended drill bit. The drill rod has spiral blades and mixing blades distributed along its outer diameter from top to bottom. The drill rod contains a grouting pipe, an air jet pipe, and a hydraulic pipe. The outlets of the grouting pipe and the air jet pipe are located at the bottom of the drill bit. The hydraulic pipe is connected to the drive unit of the extended drill bit. Beneficial effects: This invention enables batch construction of cement-soil mixing and diameter / bottom enlargement, allowing for the construction of diameter and bottom enlargements of different sizes and shapes; irregular diameter enlargements improve the overall pile performance; and soil squeezing effects are avoided during pile driving.

Description

Technical Field

[0001] This invention relates to the field of building engineering technology, and in particular to a mixing pile construction system and its construction method. Background Technology

[0002] Precast piles, due to their factory production, offer significant advantages such as reliable quality, high construction efficiency, good economics, relatively low environmental impact, and excellent corrosion resistance, leading to their increasingly widespread application. However, traditional construction methods for precast piles, such as hammering and static pressure, have limited applicability in specific conditions requiring penetration of deep, dense gravel layers and avoidance of soil squeezing effects. By employing a construction method that pre-mixes cement-soil into piles before implanting them, the consolidation of the surrounding soil can be improved, partially increasing the pile's side friction and effectively assisting the precast pile in penetrating deep, dense gravel layers to complete pile driving. Because conventional mixing pile installation does not involve soil removal during construction, only in-situ cement-soil mixing, a certain degree of compression of the surrounding soil is unavoidable during precast pile implantation, resulting in a soil squeezing effect.

[0003] The soil displacement effect during pile foundation construction refers to the squeezing, displacement, and disturbance of the surrounding soil caused by the pile penetrating into the soil. This effect has complex impacts on the engineering geological environment, adjacent structures, and the performance of the pile foundation itself. The adverse effects of the soil displacement effect are as follows: 1. Changes in soil properties Increased pore water pressure: The compression of the pile body leads to a reduction in soil pores, which can easily cause excess pore water pressure, especially in saturated soft clay. This may cause soil liquefaction or a temporary decrease in strength, such as a decrease in bearing capacity in the short term after pile driving.

[0004] Soil displacement and deformation: Horizontal and vertical displacement may affect an area several times the pile diameter, causing ground heave or lateral compression, threatening nearby pipelines and building foundations.

[0005] Soil structural failure: Highly sensitive clay or loose sand may experience structural failure due to disturbance.

[0006] 2. Risks associated with adjacent structures Uneven settlement: Soil displacement causes redistribution of the surrounding foundation soil. For example, during dense pile group construction, it may cause nearby buildings to tilt or crack.

[0007] Damage to underground facilities: Underground pipelines, tunnels, etc. may be deformed or broken due to soil displacement and pressure.

[0008] 3. Impact of pile foundation performance Time effect of bearing capacity: The bearing capacity of displacement piles may be low in the early stage, but gradually increases as the pore water pressure dissipates.

[0009] Defects in pile quality: Especially in strata of alternating soft and hard textures, rapid construction may lead to problems such as pile necking and pile breakage.

[0010] Chinese patent CN103266603A discloses a construction method for pre-drilling, expanding the bottom, and grouting prestressed concrete irregular piles. The first step involves drilling to a set depth using a single-axis drilling rig. The second step is to enlarge the hole at the pile end according to the set diameter and height. The third step involves injecting cement grout at the pile end and around the pile, simultaneously lifting the drill bit. The fourth step involves using the self-weight of the prestressed irregular-shaped concrete pile to drive it into the designed elevation. The fifth step involves hardening the cement grout at the pile end and around the pile, forming a unified structure between the pile, the pile end, and the surrounding soil, creating a pile foundation supported by the precast pile body, the cement grout at the pile end, and the soil. However, the aforementioned prestressed concrete irregular-shaped pile does not form an irregular structure with the surrounding soil that enhances its tensile and compressive strength. While the construction process uses a drilling diameter larger than the outer diameter of the prestressed concrete irregular-shaped pile section, which improves the reliability of the connection between the mixing outer core pile and the inner core pile, the connection between the entire outer core pile body and the surrounding soil cannot share the bearing capacity of the pile end, thus significantly limiting the overall performance improvement of the pile. Summary of the Invention

[0011] Purpose of the Invention: The purpose of this invention is to address the problems existing in the prior art by providing a method and equipment for mixing and planting piles. This invention adjusts and upgrades the existing mixing and planting pile process by removing a portion of the in-situ soil and then mixing it with cement slurry to form a cement-soil mixed outer core pile, which is then implanted as a precast inner core pile. The cement-soil mixed outer core pile has an irregularly shaped, enlarged diameter, further improving the overall pile performance. Since a portion of the in-situ soil is removed before the precast pile is implanted, the remaining in-situ soil is mixed with cement slurry to form flowing cement-soil, allowing the precast inner core pile to sink reliably under its own weight during driving. Therefore, the soil squeezing effect can be effectively avoided during the precast pile implantation process. Technical solution

[0012] A method for constructing concrete mixing piles includes the following steps: Step 1: Set up the equipment. Determine the location of the piles based on the survey results and design requirements, and set up the pile-planting equipment at the corresponding locations. Step 2: Drilling. The drill bit of the mixing drill includes a fixed drill bit and an extended drill bit. The extended drill bit is kept in a tightened state. Start the mixing drill and drill downwards. During the mixing and drilling process, choose to drill directly or spray grout according to the geological conditions. The soil generated during the drilling process is pushed upwards by the spiral blades above the drill bit and squeezed out of the hole. Drill the main pile hole of the outer core column. When the diameter of the fixed drill bit is equal to the diameter of the main pile hole of the outer core column, keep the extended drill bit in a tightened state and continue drilling downwards until the design elevation. When the diameter of the fixed drill bit is smaller than the diameter of the main pile hole of the outer core pile, the drill bit is opened up until its diameter is equal to the diameter of the main pile hole of the outer core pile, and drilling continues downward until the design elevation is reached; During the continued drilling process, the spiral blades above the drill bit push the soil formed during drilling upwards, and the soil is squeezed out of the hole after being stirred by the mixing blades. Step 3: Main pile hole lifting. After the mixing drill reaches the design elevation, the extended drill bit is kept in its original position, and the drill rod is rotated and lifted. During the rotation and lifting process, cement slurry is sprayed. After the slurry is mixed, it forms cement soil with the soil in place. The uniformly mixed soil in the upper part is lifted out of the hole by the spiral blades above the drill bit. Step 4: Expanding the diameter of the outer core pile. After raising the drill bit to the top elevation of the pile, rotate it again and lower it. When it reaches the designed expansion section, open the expansion drill bit according to the outer dimensions of the expansion section and the lowering speed to increase the drilling diameter. At the same time, spray cement grout. After completing the processing of one expansion section, tighten the expansion drill bit until the diameter is equal to the diameter of the main pile hole of the outer core pile, and continue to lower it to the starting point of the next expansion section. Repeat the above processing method for expansion sections until all expansion sections are completed. Step 5: Expand the bottom of the outer core pile. Continue to sink the drill bit to the starting point of the expansion bottom, stop sinking, open the expansion drill bit to enlarge the drilling diameter to the diameter of the expansion bottom, continue to rotate and sink to the design elevation, and stop sinking. At the same time, spray cement slurry and keep the mixing drill machine rotating. Step 6: Expand the diameter and lift the drill bit. Tighten the expanded drill bit and then rotate and lift it. During the rotation and lifting process, spray cement slurry. The soil that is mixed evenly in the upper part is carried out of the hole under the lifting action. Remove the mixing drill. Step 7: Pile driving. After the mixing drilling rig is removed, the precast pile driving equipment is in place, and the precast core pile is driven into the hole from the center of the core pile by its own weight. Step 8: Complete the pile driving and check the pile driving depth. If the pile is driven to the design elevation, the pile driving is completed. If the pile driving does not reach the design elevation, the core pile of the precast pile is pressed to the design elevation using auxiliary pile driving equipment to complete the pile driving.

[0013] The drilling rig of this invention includes a fixed drill bit and an extended drill bit. The opening or closing of the extended drill bit enables batch construction of cement-soil mixing and diameter / base expansion. It can simultaneously construct diameter expansion sections of different sizes and shapes, as well as base expansion sections. By removing part of the in-situ soil and then adding cement slurry for mixing, a cement-soil mixed outer core pile is formed, which is then implanted as a precast inner core pile. The pile body of the cement-soil mixed outer core pile forms an irregularly shaped diameter expansion section, further improving the overall pile performance. Since part of the in-situ soil has been removed before the precast pile is implanted, the remaining in-situ soil is mixed with cement slurry to form a flowing cement-soil mixture that forms the outer core pile. Therefore, the soil squeezing effect can be effectively avoided during the precast pile implantation process.

[0014] The construction method of mixing and planting piles can avoid the problem of unstable pile quality of cement-soil mixed outer core piles. After mixing, the in-situ soil and cement slurry are fully mixed, which can improve the fluidity of cement-soil, ensure the smooth driving of precast inner core piles, and give full play to the bearing capacity of precast inner core piles.

[0015] During the construction of cement-soil mixing core piles, when the mixer descends, the uniformly mixed soil at the top is carried out of the hole due to the upward pushing action of the helical blades on the drill rod. Conversely, when the mixer is lifted, the uniformly mixed soil at the top is carried out of the hole due to the upward lifting action of the helical blades on the drill rod. Therefore, using helical blades for soil removal ensures uniform soil removal throughout the entire cement-soil mixing core pile construction process, guaranteeing the uniformity of the pile body and thus ensuring that the precast core pile can be driven into place primarily by its own weight.

[0016] In a preferred embodiment, to ensure smooth drilling and improve the uniformity of cement-soil mixing, when the grouting function is activated during the downward drilling process in step two, the liquid to be sprayed is selected according to the geological conditions. Water is suitable for old clay or other soil layers with low moisture content, while cement slurry is suitable for soil layers with high moisture content, allowing for simultaneous mixing and settling. The liquid sprayed in steps three through six is ​​cement slurry. The water spraying method used in step two during the mixing and drilling process pre-mixes and loosens the in-situ soil. The subsequent spraying of cement slurry ensures thorough mixing between the cement slurry and the in-situ soil, guaranteeing smooth drilling and the formation of a load-bearing cement-soil mixture.

[0017] In a preferred embodiment, to improve the workability of the cement slurry, the air jet function is activated during steps two to six when the drill gets stuck or has difficulty drilling down during the mixing process.

[0018] During the mixing process, grouting and air jetting are independently controlled by their respective control systems, enabling individual grouting, air jetting, or simultaneous grouting and air jetting. Grouting, air jetting, or simultaneous operation can be selected as needed to achieve uniform mixing of the cement-soil mixture. If the drill gets stuck or drilling becomes difficult during mixing, the air jetting function can be activated to improve the workability of the cement-soil slurry, prevent drill jamming, and promote thorough mixing and uniformity of the cement-soil slurry.

[0019] In a preferred embodiment, in order to improve the strength of the cement-soil mixture and ensure the forming quality of the enlarged diameter section and the enlarged bottom section, the water-cement ratio is 0.6~1.2 when spraying cement slurry in steps two, three and six; and the water-cement ratio is reduced by 0.1~0.5 within the range of the ultimate bearing capacity of the grouting pipe when spraying cement slurry in steps four and five.

[0020] When spraying cement slurry in steps two, three, and six, the water-cement ratio should be controlled between 0.6 and 1.2. Within the range of the ultimate bearing capacity of the spraying pipe, the water-cement ratio should be reduced as much as possible, which is beneficial to improving the strength of cement-soil. Different water-cement ratios are used during the equal-diameter mixing, diameter expansion, and bottom expansion processes to ensure the cement-soil strength of each part. Under the same geological and depth conditions, since the stress area of ​​the diameter expansion section and the bottom expansion section is smaller and farther than the pile core, it is necessary to reduce the water-cement ratio of the cement slurry during mixing to improve the cement-soil strength, thereby ensuring the forming quality of the diameter expansion section and the bottom expansion section. This ensures that the diameter expansion section and the bottom expansion section can fully play their role and effectively transfer the side friction and end resistance to the surrounding soil during the pile foundation stress process, thus ensuring the performance of the single pile bearing capacity.

[0021] In a preferred embodiment, to ensure uniform mixing of cement and soil at the bottom and to ensure more regular dimensions of the bottom, when expanding the bottom of the outer core pile in step five, after completing the first bottom expansion drilling, the drill bit is kept at its current diameter and rotated up and down between the starting point of the bottom expansion and the design elevation, while simultaneously spraying cement slurry. Finally, the drill bit proceeds to step six from the design elevation.

[0022] Because the amount of cement and soil to be mixed for bottom enlargement is relatively large, and a spherical surface is formed when the enlargement drill bit rotates and opens, in order to make the bottom enlargement form a regular cylindrical shape, the irregular shape formed when the enlargement drill bit first opens during the enlargement process can be corrected by rotating and mixing it up and down.

[0023] A construction device for implementing a mixing pile driving method includes a mixing drill and auxiliary pile driving equipment. The mixing drill includes a drive unit, a drill rod, and a drill bit. The top end of the drill rod is connected to the drive unit, and the drill bit is fixedly installed at the bottom of the drill rod. The drill bit includes a fixed drill bit and an extended drill bit. The drill rod has spiral blades and mixing blades distributed on the outer diameter of the drill rod in sequence from the top of the drill rod. The drill rod is provided with a grouting pipe, an air jet pipe, and a hydraulic pipe. The outlets of the grouting pipe and the air jet pipe are respectively arranged at the lower part of the drill bit, and the hydraulic pipe is connected to the drive part of the extended drill bit.

[0024] The drill bit of the mixing drill includes a fixed drill bit and an extended drill bit. The cement-soil mixing and diameter and bottom expansion can be carried out in batches by opening or closing the extended drill bit. At the same time, different sizes of diameter and bottom expansion can be achieved. During the construction of cement-soil mixing core piles, when the mixer descends, the uniformly mixed soil at the top is carried out of the hole due to the upward pushing action of the helical blades on the drill rod. Conversely, when the mixer is lifted, the uniformly mixed soil at the top is carried out of the hole due to the upward lifting action of the helical blades on the drill rod. Therefore, using helical blades for soil removal ensures uniform soil removal throughout the entire cement-soil mixing core pile construction process, guaranteeing the uniformity of the pile body and thus ensuring that the precast core pile can be driven into place primarily by its own weight.

[0025] Using spiral blades to extract soil can effectively reduce the environmental impact of cement slurry discharge during the cement-soil mixing core pile construction process, reduce the costs incurred from cement slurry discharge, and allow the extracted soil to be collected and mixed thoroughly with cement to form cement-soil for reuse.

[0026] During the mixing process, grouting and air jetting are independently controlled by their respective control systems, enabling individual grouting, air jetting, or simultaneous grouting and air jetting. Grouting, air jetting, or simultaneous operation can be selected as needed to achieve uniform mixing of the cement-soil mixture. If the drill gets stuck or drilling becomes difficult during mixing, the air jetting function can be activated to improve the workability of the cement-soil slurry, prevent drill jamming, and promote thorough mixing and uniformity of the cement-soil slurry.

[0027] The expansion drill bit can be fully or partially opened or closed via hydraulic lines. The maximum outer diameter of the fully opened expansion drill bit is the same as the maximum diameter of the designed expansion section or base. During the expansion process, the expansion drill bit can first fully open before expanding the diameter or base, or it can open or close simultaneously while maintaining pressure and limiting the drilling process. Furthermore, it can form expansions of different sizes at different locations above and below the drill bit, according to design requirements, to meet various expansion needs. To ensure more reasonable stress distribution during expansion, the expansion drill bit can form an inverted T-shaped expansion for tension piles, ensuring full utilization of the tension bearing capacity.

[0028] Mixing and pile driving can be carried out using integrated or separate equipment. When using integrated equipment for mixing and auxiliary pile driving, the integrated equipment should have functions such as centering, pile clamping, and pile driving. When using separate equipment, temporary fixing fixtures should be used to fix the first precast pile during the driving process to prevent it from falling into the cement-soil mixing pile hole, thus making full use of existing equipment and avoiding repeated equipment investment.

[0029] In a preferred embodiment, to improve the adaptability of the drill rod and enable a single drill rod to be used for the construction of cement-soil mixing piles of various diameters, the mixing blade includes a fixing element and a detachable blade. The fixing element is used to fix the detachable blade, and the diameter of the detachable blade is equal to the inner diameter of the main pile hole of the outer core pile. The detachable blade can be replaced to meet the requirements of different main pile hole diameters for outer core piles, thereby improving the adaptability of the drill rod.

[0030] In a preferred embodiment, in order to increase the number of times the cement-soil is mixed, increase its uniformity, and prevent it from solidifying too early, the mixing blades are distributed on the outer diameter of the drill rod within a range of 1m to 30m above the spiral blades.

[0031] In a preferred embodiment, in order to achieve different soil extraction volumes and thus reduce or avoid the soil squeezing effect, the spiral blades are distributed on the outer diameter of the drill rod within a range of 1m to 8m above the drill bit. The diameter of the spiral blades is equal to the inner diameter of the main pile hole of the outer core pile. The spiral angle of the spiral blades is 5° to 15°, and the pitch of the spiral blades is 200mm to 1100mm. The pitch increases with the increase of the spiral blades.

[0032] The use of helical blades for soil extraction allows for different soil extraction functions and volumes by using helical blades of varying axial lengths, typically ranging from 1m to 8m. This reduces or eliminates the soil squeezing effect, thus avoiding the impact of traditional mixing pile foundation construction on surrounding buildings, pipelines, underground structures, and other existing structures, expanding the application scope of mixing piles. Adjusting the helical angle and pitch can regulate the soil extraction and mixing effects of the helical blades, ensuring thorough mixing of cement and soil while meeting the soil extraction objectives.

[0033] The soil-taking function of the helical blades can be adjusted by setting the axial length of the helical blades. When the axial length of the helical blades is in the range of 4m to 8m, the amount of soil taken during the construction of cement-soil mixing core piles is relatively large. This can completely avoid the squeezing effect on the soil around the pile during the construction of cement-soil mixing core piles and the implantation of precast core piles, and fully realize the self-weight pile driving of precast core piles. At this time, the soil squeezing effect can be completely avoided.

[0034] When the axial length of the spiral blade is in the range of 1m to 4m, the amount of soil taken during the construction of cement-soil mixing outer core piles is small, which can effectively reduce the squeezing effect on the soil around the pile during the construction of cement-soil mixing outer core piles and the implantation of precast inner core piles, and partially realize the self-weight pile driving of precast inner core piles. At this time, it only plays the role of reducing the soil squeezing effect.

[0035] Without the spiral blades, soil cannot be removed during the excessive weight of the cement-soil mixing outer core pile. In this case, the squeezing effect on the soil around the pile cannot be reduced during the pile formation process of the cement-soil mixing outer core pile and the implantation process of the precast inner core pile, and the self-weight pile driving of the precast inner core pile cannot be achieved.

[0036] In a preferred embodiment, to meet the drilling requirements at different elevations, the drill rod adopts quick-release joints, and the joints of the grouting pipe, air jet pipe, and hydraulic pipe inside the drill rod all adopt quick-release joints; the compressive bearing capacity of the grouting pipe, air jet pipe, and hydraulic pipe in the drill rod must be no less than 10MPa, 3MPa, and 60MPa, respectively.

[0037] The drill pipe uses quick-release joints. When the drill pipe length is insufficient and extension is required, the internal guide pipe joint uses a quick-release joint, allowing for rapid assembly and disassembly. The pressure bearing capacity of the grouting, air purging, and hydraulic control guide pipes in the mixing drill pipe must be no less than 10MPa, 3MPa, and 60MPa respectively, to meet the maximum required pressure and have a certain safety reserve.

[0038] Beneficial effects: The drill bit of the mixing drill of this invention includes a fixed drill bit and an extended drill bit. The opening or closing of the extended drill bit enables the phased construction of cement-soil mixing and diameter and bottom expansion. At the same time, it can realize the construction of diameter expansion sections of different sizes and shapes as well as bottom expansion. By removing part of the in-situ soil and then adding cement slurry for mixing, a cement-soil mixed outer core pile is formed, and then a precast inner core pile is implanted. The pile body of the cement-soil mixed outer core pile forms an irregular diameter expansion section, which further improves the overall performance of the pile body. Since part of the in-situ soil has been removed before the precast pile is implanted, the remaining in-situ soil is mixed with cement slurry to form a flowing cement-soil mixture that forms the outer core pile. Therefore, the soil squeezing effect can be effectively avoided during the precast pile implantation process.

[0039] The construction method of mixing and planting piles can avoid the problem of unstable pile quality of cement-soil mixed outer core piles. After mixing, the in-situ soil and cement slurry are fully mixed, which can improve the fluidity of cement-soil, ensure the smooth driving of precast inner core piles, and give full play to the bearing capacity of precast inner core piles.

[0040] During the construction of cement-soil mixing core piles, when the mixer descends, the uniformly mixed soil at the top is carried out of the hole due to the upward pushing action of the helical blades on the drill rod. Conversely, when the mixer is lifted, the uniformly mixed soil at the top is carried out of the hole due to the upward lifting action of the helical blades on the drill rod. Therefore, using helical blades for soil removal ensures uniform soil removal throughout the entire cement-soil mixing core pile construction process, guaranteeing the uniformity of the pile body and thus ensuring that the precast core pile can be driven into place primarily by its own weight. Attached Figure Description

[0041] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0042] Figure 1 This is a front view of the extended drill bit of the mixing drill of the present invention in the closed state; Figure 2 This is a left view of the extended drill bit of the mixing drill of the present invention in the deployed state; Figure 3 This is a schematic diagram of the structure of the mixing pile planting of the present invention.

[0043] In the diagram: drive unit 1, drill rod 2, spiral blade 21, stirring blade 22, drill bit 3, fixed drill bit 31, extended drill bit 32, outer core pile 4, pile body 41, enlarged diameter section 42, enlarged bottom section 43, precast inner core pile 5. Detailed Implementation

[0044] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and 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 invention.

[0046] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0047] like Figure 1 , 2 As shown in Figure 3, a method for constructing mixed-mix piles includes the following steps: Step 1: Set up the equipment. Determine the location of the piles based on the survey results and design requirements, and set up the pile-planting equipment at the corresponding locations. Step 2, Drilling: The drill bit 3 of the mixing drill includes a fixed drill bit 31 and an extended drill bit 32. The extended drill bit 32 is kept in a tightened state. The mixing drill is started to drill downwards. During the mixing and drilling process, direct drilling or grouting is selected according to the geological conditions. The soil generated during the drilling process is pushed upwards by the spiral blades 21 above the drill bit and squeezed out of the hole. Drill the main pile hole of the outer core pile 4. When the diameter of the fixed drill bit 31 is equal to the diameter of the main pile hole of the outer core pile 4, the expansion drill bit 32 remains in a tightened state and continues to drill downwards until the design elevation. When the diameter of the fixed drill bit 31 is smaller than the diameter of the main pile hole of the outer core pile 4, the expansion drill bit 32 is opened until its diameter is equal to the diameter of the main pile hole of the outer core pile 4, and drilling continues downward until the design elevation is reached. During the continued drilling process, the spiral blades 21 above the drill bit push the soil formed during the drilling process upwards, and the soil is squeezed out of the hole after being stirred by the stirring blades 22. Step 3: Main pile hole lifting. After the mixing drill reaches the design elevation, the extended drill bit 32 remains in its original position, and the drill rod 2 is rotated and lifted. During the rotation and lifting process, cement slurry is sprayed. After the sprayed slurry is mixed, it forms cement soil with the soil in place. The uniformly mixed soil in the upper part is lifted upward by the spiral blade 21 above the drill bit and carried out of the hole. Step 4: Expand the diameter section 42 of the outer core pile 4. After the drill bit 3 is raised to the top elevation of the pile, it is rotated and lowered again. When it sinks to the designed diameter section 42, the expansion drill bit 32 is opened to expand the drilling diameter according to the outer dimensions of the diameter section 42 and the sinking speed. At the same time, cement slurry is sprayed. After completing the processing of one diameter section 42, the expansion drill bit 32 is tightened until the diameter is equal to the diameter of the main pile hole of the outer core pile 4. It continues to sink to the starting point of the next diameter section 42. The above processing method of the diameter section 42 is repeated until all diameter sections 42 are processed. Step 5: Expand the bottom 43 of the outer core pile 4. Continue to sink the drill bit to the starting point of the bottom 43, stop sinking, open the expansion drill bit 32 to expand the drilling diameter to the diameter of the bottom 43, continue to rotate and sink to the design elevation, and stop sinking. At the same time, spray cement slurry and keep the mixing drill machine rotating. Step 6: Expand the diameter and lift the drill bit. Tighten the expanded drill bit 32 and then rotate and lift it. During the rotation and lifting process, spray cement slurry. The soil that is mixed evenly in the upper part is carried out of the hole under the lifting action. Remove the mixing drill. Step 7: Pile driving. After the mixing drilling rig is removed, the precast pile driving equipment is in place, and the precast core pile is driven into the hole from the center of the core pile by its own weight. Step 8: Complete the pile driving and check the pile driving depth. If the pile is driven to the design elevation, the pile driving is completed. If the pile driving does not reach the design elevation, the core pile of the precast pile is pressed to the design elevation using auxiliary pile driving equipment to complete the pile driving.

[0048] The drilling rig of this invention includes a fixed drill bit 31 and an extended drill bit 32. The opening or closing of the extended drill bit 32 enables the phased construction of cement-soil mixing and diameter and bottom expansion. At the same time, it can realize the construction of diameter expansion sections 42 of different sizes and shapes, as well as the construction of bottom expansion sections 43. By taking out part of the in-situ soil and then adding cement slurry for mixing, a cement-soil mixed outer core pile 4 is formed, and then a precast inner core pile 5 is implanted. The pile body of the cement-soil mixed outer core pile 4 forms an irregular diameter expansion section 42, which further improves the overall performance of the pile body. Since part of the in-situ soil has been taken out before the precast pile is implanted, the remaining in-situ soil is mixed with cement slurry to form a flowing cement-soil to form the outer core pile 4. Therefore, the soil squeezing effect can be effectively avoided during the precast pile implantation process.

[0049] The construction method of mixing and planting piles can avoid the problem of unstable pile quality of cement-soil mixing outer core piles 4. After mixing, the in-situ soil and cement slurry are fully mixed, which can improve the fluidity of cement-soil and ensure the smooth driving of precast inner core piles 5, and give full play to the pile bearing capacity of precast inner core piles 5.

[0050] During the construction of the cement-soil mixing core pile 4, when the mixing is lowered, the uniformly mixed soil at the top is carried out of the hole due to the upward pushing action of the spiral blades 21 on the drill rod. When the mixing is raised, the uniformly mixed soil at the top is carried out of the hole due to the upward lifting action of the spiral blades 21 on the drill rod. Therefore, using the spiral blades 21 to remove soil can uniformly remove soil throughout the entire cement-soil mixing core pile 4 pile formation process, ensuring the uniformity of the pile body of the cement-soil mixing core pile 4, thereby ensuring that the precast inner core pile 5 can be driven into place basically by its own weight.

[0051] To ensure smooth drilling and improve the uniformity of cement-soil mixing, in step two, when the grouting function is activated during the downward drilling process, the liquid to be sprayed is selected according to the geological conditions. Clean water is suitable for old clay or other soil layers with low moisture content, while cement slurry is suitable for soil layers with high moisture content, allowing the mixture to settle while being stirred. The liquid sprayed in steps three through six is ​​cement slurry. In step two, the method of spraying water during the mixing and drilling process can pre-stir and loosen the in-situ soil. After spraying cement slurry and mixing, the cement slurry and the in-situ soil are fully mixed, ensuring smooth drilling and the formation of a cement-soil mixture with load-bearing capacity.

[0052] To improve the workability of the cement-soil slurry, in steps two through six, the air jet function is activated when the drill gets stuck or has difficulty drilling down during the mixing process.

[0053] During the mixing process, grouting and air jetting are independently controlled by their respective control systems, enabling individual grouting, air jetting, or simultaneous grouting and air jetting. Grouting, air jetting, or simultaneous operation can be selected as needed to achieve uniform mixing of the cement-soil mixture. If the drill gets stuck or drilling becomes difficult during mixing, the air jetting function can be activated to improve the workability of the cement-soil slurry, prevent drill jamming, and promote thorough mixing and uniformity of the cement-soil slurry.

[0054] In order to improve the strength of cement-soil and ensure the forming quality of the enlarged diameter section 42 and the enlarged bottom section 43, the water-cement ratio is 0.6~1.2 when spraying cement slurry in steps two, three and six; and the water-cement ratio is reduced by 0.1~0.5 within the range of the ultimate bearing capacity of the grouting pipe when spraying cement slurry in steps four and five.

[0055] When spraying cement slurry in steps two, three, and six, the water-cement ratio should be controlled between 0.6 and 1.2. Within the range of the ultimate bearing capacity of the spraying pipe, the water-cement ratio should be reduced as much as possible, which is beneficial to improving the strength of cement-soil. Different water-cement ratios are used during the equal-diameter mixing, diameter expansion, and bottom expansion processes to ensure the cement-soil strength of each part. Under the same geological and depth conditions, since the stress-bearing area of ​​the diameter expansion section 42 and the bottom expansion section 43 is smaller and farther away from the pile core, it is necessary to reduce the water-cement ratio of the cement slurry during mixing to improve the cement-soil strength, thereby ensuring the forming quality of the diameter expansion section 42 and the bottom expansion section 43. This ensures that the diameter expansion section 42 and the bottom expansion section 43 can fully play their role and effectively transmit the side friction and end resistance to the surrounding soil during the pile foundation stress process, thus ensuring the performance of the single pile bearing capacity.

[0056] To ensure uniform mixing of cement and soil at the bottom 43 and to ensure more regular dimensions of the bottom 43, during the expansion drilling of the outer core pile 4 in step five, after the first expansion drilling of the bottom 43 is completed, the expansion drill bit 32 maintains its current diameter and rotates up and down between the starting point of the bottom 43 and the design elevation to stir, while spraying cement slurry. Finally, it proceeds to step six from the design elevation.

[0057] Since the amount of cement soil to be mixed in the bottom expansion 43 is relatively large, and a spherical surface will be formed when the expansion drill bit 32 rotates and opens, in order to make the bottom expansion 43 form a regular cylindrical shape, the irregular shape formed when the expansion drill bit 32 first opens during the expansion of the bottom expansion 43 can be corrected by rotating and mixing up and down.

[0058] A construction device for implementing a mixing pile driving method includes a mixing drill and an auxiliary pile driving device. The mixing drill includes a drive unit 1, a drill rod 2, and a drill bit 3. The top end of the drill rod 2 is connected to the drive unit 1, and the drill bit 3 is fixedly installed at the bottom of the drill rod 2. The drill bit 3 includes a fixed drill bit 31 and an extended drill bit 32. The drill rod 2 is provided with spiral blades 21 and mixing blades 22 distributed on the outer diameter of the drill rod 2 from the top of the drill bit 3. The drill rod 2 is provided with a grouting pipe, an air jet pipe, and a hydraulic pipe. The outlets of the grouting pipe and the air jet pipe are respectively arranged at the lower part of the drill bit 3, and the hydraulic pipe is connected to the drive part of the extended drill bit 32.

[0059] The drill bit 3 of the mixing drill includes a fixed drill bit 31 and an extended drill bit 32. The cement-soil mixing and diameter and bottom expansion can be carried out in batches by opening or closing the extended drill bit 32. At the same time, different sizes of diameter and bottom expansion can be achieved. During the construction of the cement-soil mixing core pile 4, when the mixing is lowered, the uniformly mixed soil at the top is carried out of the hole due to the upward pushing action of the spiral blades 21 on the drill rod 2. When the mixing is raised, the uniformly mixed soil at the top is carried out of the hole due to the upward lifting action of the spiral blades 21 on the drill rod 2. Therefore, using the spiral blades 21 to remove soil can uniformly remove soil throughout the entire cement-soil mixing core pile 4 pile formation process, ensuring the uniformity of the pile body 41 of the cement-soil mixing core pile 4, thereby ensuring that the precast inner core pile 5 can be driven into place basically by its own weight.

[0060] Using the spiral blade 21 to extract soil can effectively reduce the environmental impact of cement slurry discharge during the cement-soil mixing core pile 4-stage pile construction process, reduce the cost of cement slurry discharge, and at the same time, the extracted soil can be collected and placed in a centralized manner, and can be fully mixed with cement to form cement-soil for reuse.

[0061] During the mixing process, grouting and air jetting are independently controlled by their respective control systems, enabling individual grouting, air jetting, or simultaneous grouting and air jetting. Grouting, air jetting, or simultaneous operation can be selected as needed to achieve uniform mixing of the cement-soil mixture. If the drill gets stuck or drilling becomes difficult during mixing, the air jetting function can be activated to improve the workability of the cement-soil slurry, prevent drill jamming, and promote thorough mixing and uniformity of the cement-soil slurry.

[0062] The expansion drill bit 32 can be fully or partially opened or closed via hydraulic lines. The maximum outer diameter of the fully opened expansion drill bit 32 is the same as the maximum diameter of the designed enlargement section 42 or enlargement base 43. During the enlargement process, the expansion drill bit 32 can first fully open before enlarging the diameter or base, or it can open or close while maintaining pressure and limiting movement during drilling, and can also form different sizes of enlargement and base at different positions above and below according to design requirements to meet different enlargement and base needs. To ensure more reasonable stress distribution during enlargement, the expansion drill bit 32 can form an inverted T-shaped enlargement for tension piles to ensure full utilization of the tension bearing capacity.

[0063] Mixing and pile driving can be carried out using integrated or separate equipment. When using integrated equipment for mixing and auxiliary pile driving, the integrated equipment should have functions such as centering, pile clamping, and pile driving. When using separate equipment, temporary fixing fixtures should be used to fix the first precast pile during the driving process to prevent it from falling into the cement-soil mixing pile hole, thus making full use of existing equipment and avoiding repeated equipment investment.

[0064] To improve the adaptability of the drill rod and enable a single drill rod to be used for the construction of cement-soil mixing piles of various diameters, the mixing blade includes a fixing component and a detachable blade. The fixing component is used to secure the detachable blade, and the diameter of the detachable blade is equal to the inner diameter of the main pile hole of the cement-soil mixing core pile 4. The detachable blade can be replaced to meet the requirements of different inner diameters of the main pile hole of the cement-soil mixing core pile 4, thereby improving the adaptability of the drill rod.

[0065] In order to increase the number of times the cement-soil is mixed, increase its uniformity, and prevent it from solidifying too early, the mixing blades are distributed on the outer diameter of the drill rod within a range of 1m to 30m above the spiral blades 21.

[0066] In order to achieve different soil extraction volumes and reduce or avoid the soil squeezing effect, the spiral blades 21 are distributed on the outer diameter of the drill rod within a range of 1m to 8m above the drill bit. The diameter of the spiral blades 21 is equal to the inner diameter of the main pile hole of the outer core pile 4. The spiral angle of the spiral blades 21 is 5° to 15°, and the pitch of the spiral blades 21 is 200mm to 1100mm. The pitch increases with the increase of the spiral blades 21.

[0067] The method of using spiral blades 21 for soil extraction can achieve different soil extraction functions and volumes by setting spiral blades 21 with different axial lengths, typically 1m to 8m. This reduces or avoids the soil squeezing effect, thereby avoiding the impact of traditional mixing pile foundation construction on surrounding buildings, pipelines, underground structures, and other existing structures, and expanding the application scope of mixing piles. By adjusting the spiral angle and pitch, the soil extraction and mixing effects of the spiral blades 21 can be adjusted, ensuring that the cement-soil is fully mixed while meeting the soil extraction purpose.

[0068] The soil-taking function of the spiral blade 21 can be adjusted by setting the axial length of the spiral blade 21. When the axial length of the spiral blade 21 is in the range of 4m to 8m, the amount of soil taken during the construction of the cement-soil mixing outer core pile 4 is relatively large, which can completely avoid the squeezing effect on the soil around the pile during the construction of the cement-soil mixing outer core pile and the implantation of the precast inner core pile 5, and fully realize the self-weight pile driving of the precast inner core pile 5. At this time, the soil squeezing effect can be completely avoided.

[0069] When the axial length of the spiral blade 21 is in the range of 1m to 4m, the amount of soil taken during the construction of the cement-soil mixing outer core pile 4 is small, which can effectively reduce the squeezing effect on the soil around the pile during the construction of the cement-soil mixing outer core pile and the implantation of the precast inner core pile 5, and partially realize the self-weight pile driving of the precast inner core pile 5. At this time, it only plays the role of reducing the soil squeezing effect.

[0070] Without the spiral blade 21, soil cannot be removed during the excessive weight of the cement-soil mixing outer core pile 4. At this time, the squeezing effect on the soil around the pile cannot be reduced during the pile formation process of the cement-soil mixing outer core pile and the implantation process of the precast inner core pile 5, and the self-weight pile driving of the precast inner core pile 5 cannot be achieved.

[0071] To meet the drilling requirements at different elevations, the drill rod adopts quick-release joints. The joints of the grouting pipe, air jet pipe, and hydraulic pipe in the drill rod 2 are all quick-release joints. The compressive bearing capacity of the grouting pipe, air jet pipe, and hydraulic pipe in the drill rod 2 must be no less than 10MPa, 3MPa, and 60MPa, respectively.

[0072] Drill rod 2 uses a quick-release connector. When the length of drill rod 2 is insufficient and an extension is required, the inner guide pipe connector of drill rod 2 uses a quick-release connector, which can achieve rapid disassembly and assembly. The pressure bearing capacity of the grouting, air purging and hydraulic control guide pipes in the mixing drill rod 2 must be no less than 10MPa, 3MPa and 60MPa respectively, which can meet the requirements of the maximum required pressure and have a certain safety reserve.

[0073] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0074] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for constructing piles by mixing water, characterized in that, Includes the following steps: Step 1: Set up the equipment. Determine the location of the piles based on the survey results and design requirements, and set up the pile-planting equipment at the corresponding locations. Step 2: Drilling. The drill bit of the mixing drill includes a fixed drill bit and an extended drill bit. The extended drill bit is kept in a tightened state. Start the mixing drill and drill downwards. During the mixing and drilling process, choose to drill directly or spray grout according to the geological conditions. The soil generated during the drilling process is pushed upwards by the spiral blades above the drill bit and squeezed out of the hole. When drilling the main pile hole of the outer core pile, when the diameter of the fixed drill bit is equal to the diameter of the main pile hole of the outer core pile, the expansion drill bit is kept in a tightened state and drilling continues downward until the design elevation is reached; When the diameter of the fixed drill bit is smaller than the diameter of the main pile hole of the outer core pile, the drill bit is opened up until its diameter is equal to the diameter of the main pile hole of the outer core pile, and drilling continues downward until the design elevation is reached; During the continued drilling process, the spiral blades above the drill bit push the soil formed during drilling upwards, and the soil is squeezed out of the hole after being stirred by the mixing blades. Step 3: Main pile hole lifting. After the mixing drill reaches the design elevation, the extended drill bit is kept in its original position, and the drill rod is rotated and lifted. During the rotation and lifting process, cement slurry is sprayed. After the slurry is mixed, it forms cement soil with the soil in place. The uniformly mixed soil in the upper part is lifted out of the hole by the spiral blades above the drill bit. Step 4: Expanding the diameter of the outer core pile. After raising the drill bit to the top elevation of the pile, rotate it again and lower it. When it reaches the designed expansion section, open the expansion drill bit according to the outer dimensions of the expansion section and the lowering speed to increase the drilling diameter. At the same time, spray cement grout. After completing the processing of one expansion section, tighten the expansion drill bit until the diameter is equal to the diameter of the main pile hole of the outer core pile, and continue to lower it to the starting point of the next expansion section. Repeat the above processing method for expansion sections until all expansion sections are completed. Step 5: Expand the bottom of the outer core pile. Continue to sink the drill bit to the starting point of the expansion bottom, stop sinking, open the expansion drill bit to enlarge the drilling diameter to the diameter of the expansion bottom, continue to rotate and sink to the design elevation, and stop sinking. At the same time, spray cement slurry and keep the mixing drill machine rotating. Step 6: Expand the diameter and lift the drill bit. Tighten the expanded drill bit and then rotate and lift it. During the rotation and lifting process, spray cement slurry. The soil that is mixed evenly in the upper part is carried out of the hole under the lifting action. Remove the mixing drill. Step 7: Pile driving. After the mixing drilling rig is removed, the precast pile driving equipment is in place, and the precast core pile is driven into the hole from the center of the core pile by its own weight. Step 8: Complete the pile driving and check the pile driving depth. If the pile is driven to the design elevation, the pile driving is completed. If the pile driving does not reach the design elevation, the core pile of the precast pile is pressed to the design elevation using auxiliary pile driving equipment to complete the pile driving.

2. The method for mixing and planting piles according to claim 1, characterized in that: When the shotcreting function is activated during the downward drilling process in step two, the liquid to be sprayed is selected according to the geological conditions. Clear water is suitable for old clay or other soil layers with low moisture content, while cement slurry is suitable for soft soil layers. The mixture sinks while being stirred. The liquid sprayed in steps three to six is ​​cement slurry.

3. The method for mixing and planting piles according to claim 1, characterized in that: In steps two through six, if the drill gets stuck or has difficulty going down during the mixing process, activate the air jet function.

4. The method for mixing and planting piles according to claim 1, characterized in that: When spraying cement slurry in steps two, three, and six, the water-cement ratio is 0.6 to 1.2; when spraying cement slurry in steps four and five, the water-cement ratio is reduced by 0.1 to 0.5 within the range of the ultimate bearing capacity of the spraying pipe.

5. The method for mixing and planting piles according to claim 1, characterized in that: In step five, when expanding the bottom of the outer core pile, after completing the first expansion drilling of the bottom, the expansion drill bit is kept at its current diameter and rotated up and down between the starting point of the expansion and the design elevation, while spraying cement slurry. Finally, step six begins from the design elevation.

6. A construction device for implementing the mixing pile driving method of claim 1 or 3, comprising a mixing drill and auxiliary pile driving equipment, wherein the mixing drill comprises a drive unit, a drill rod and a drill bit, the top end of the drill rod is connected to the drive unit, and the drill bit is fixedly installed at the bottom of the drill rod, characterized in that: The drill bit includes a fixed drill bit and an extended drill bit; the drill rod is provided with spiral blades and stirring blades distributed on the outer diameter of the drill rod in sequence from the drill bit upward; the drill rod is provided with a grouting pipe, an air jet pipe and a hydraulic pipe respectively, the outlets of the grouting pipe and the air jet pipe are respectively arranged at the lower part of the drill bit, and the hydraulic pipe is connected to the drive part of the extended drill bit.

7. The method for mixing and planting piles according to claim 6, characterized in that: The stirring blade includes a fixing member and a detachable blade. The fixing member is used to fix the detachable blade, and the diameter of the detachable blade is equal to the diameter of the main pile hole of the outer core pile.

8. The method for mixing and planting piles according to claim 6, characterized in that: The stirring blades are distributed on the outer diameter of the drill rod within a range of 1m to 30m above the spiral blades.

9. The method for mixing and planting piles according to claim 6, characterized in that: The spiral blades are distributed on the outer diameter of the drill rod within a range of 1m to 8m above the drill bit. The diameter of the spiral blades is equal to the inner diameter of the main pile hole of the outer core pile. The spiral angle of the spiral blades is 5° to 15°, and the pitch of the spiral blades is 200mm to 1100mm. The pitch increases with the increase of the diameter of the spiral blades.

10. The method for constructing piles by mixing water according to claim 6, characterized in that: The drill pipe adopts quick-release joints, and the joints of the grouting pipe, air jet pipe and hydraulic pipe in the drill pipe are all quick-release joints; the pressure bearing capacity of the grouting pipe, air jet pipe and hydraulic pipe in the drill pipe must be no less than 10MPa, 3MPa and 60MPa respectively.

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