A large-diameter cast-in-place pile bottom soft soil layer reinforcement system and method

Abstract

The application discloses a large-diameter cast-in-place pile bottom soft soil layer reinforcing system and method, and solves the problem that the existing technology is complex in processing the soft soil layer, has the beneficial effects of convenient operation and time saving, and specifically has the following technical scheme: a large-diameter cast-in-place pile bottom soft soil layer reinforcing system, which comprises a spray pipe, the spray pipe is connectable with a drilling machine, the spray pipe is insertable into a central grouting hole of a large-diameter cast-in-place pile and extendable into a pile bottom soft soil layer at the bottom of the large-diameter cast-in-place pile, a first nozzle, a second nozzle and a third nozzle are sequentially arranged on the top of the spray pipe from top to bottom, the first nozzle is connected with a slurry supply component, the second nozzle is connected with a gas supply component, the third nozzle is connected with a water supply component, the second nozzle and the third nozzle are annular, the first nozzle is inserted into a hollow portion of the second nozzle, the second nozzle is inserted into a hollow portion of the third nozzle, and the third nozzle is fixedly connected with a spray pipe body.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of geotechnical and foundation engineering construction technology, in particular to a large-diameter bored pile bottom soft soil layer reinforcement system and method. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] Large-diameter bored piles are widely used in deep foundation engineering due to their strong adaptability, high bearing capacity, and convenient construction. However, during the construction of large-diameter bored piles, due to factors such as construction equipment, technical process level, and complex engineering geological conditions, different thicknesses of soft soil layers such as sediment or virtual soil are inevitably left at the bottom of the large-diameter bored pile. These soft soil layers are difficult to completely remove during construction, and the presence of soft soil layers such as sediment or virtual soil can lead to a decrease in the vertical compressive bearing capacity of the single pile, a decrease in the stability of the foundation, and a significant increase in the settlement of the pile top, resulting in engineering quality accidents.

[0004] Due to the long construction period and high cost of large-diameter bored piles, if the supporting force of the pile side soil and the pile end soil layer cannot be effectively utilized, it will not only affect the construction progress of the project, but also result in a situation where the vertical compressive bearing capacity of the single pile does not meet the design requirements. In the current commonly used reinforcement treatment measures, in many projects, due to the excessive thickness of the soft soil layer at the bottom of the pile, multiple hole cleaning or secondary sediment treatment by opening a hole at the top of the pile is performed before pouring concrete. In addition, high-pressure jet grouting method double-tube method is also used to treat soft soil layers around the bored pile, which has good effect, but this construction requires a certain number of drill holes around the pile, which is complicated and requires a relatively large construction operation range, with limited application scope. Even worse, some important projects need to construct new bored piles to meet the bearing capacity requirements of the pile foundation.

[0005] In summary, the existing methods for treating soft soil layers are complex, have a large impact on the surrounding environment, seriously affect the construction progress of the project, and also consume a large amount of manpower, financial resources, and material resources, causing great waste of resources. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide a large-diameter bored pile bottom soft soil layer reinforcement system, which has a simple treatment method and utilizes high-pressure jet grouting to mix the virtual soil and sediment at the bottom of the pile with the injected slurry to form a high-strength consolidated body.

[0007] To achieve the above-mentioned purposes, the present application is realized by the following technical solutions:

[0008] The application discloses a large-diameter bored pile bottom soft soil layer reinforcing system, which comprises a nozzle.

[0009] The first nozzle is connected with a slurry supply component, the second nozzle is connected with a gas supply component, and the third nozzle is connected with a water supply component.

[0010] The bottom of the third nozzle is protruded downward, and a bottom opening is arranged at the protruded position.

[0011] The bottom opening is a threaded hole, and the third nozzle is connected with the nozzle body through a threaded structure.

[0012] The first nozzle comprises a first shell, the bottom of the first shell is protruded toward the second nozzle, and a first opening is formed at the protruded position to spray cement slurry.

[0013] The top of the second nozzle is provided with a first recess to support the bottom protruded position of the first nozzle.

[0014] The bottom of the second nozzle is provided with a plurality of second openings to spray gas flow.

[0015] The second nozzle is welded with the first nozzle.

[0016] The top of the third nozzle is provided with a second recess to support the second nozzle.

[0017] The third nozzle is connected with the second nozzle through welding or fasteners.

[0018] The slurry supply component is a slurry mixer, which is connected with the first nozzle through a grouting pump.

[0019] The water supply component is connected with the third nozzle through a water pump, and the water supply component supplies high-pressure water flow to the third nozzle.

[0020] In some schemes, the inner diameter of the second nozzle is matched with the outer diameter of the first nozzle to support the first nozzle, and the inner diameter of the third nozzle is matched with the outer diameter of the second nozzle to support the second nozzle, so that the first nozzle is inserted into the second nozzle, and the second nozzle is inserted into the third nozzle.

[0021] In a second aspect, the present application further provides a method for reinforcing a soft soil layer at the bottom of a large-diameter bored pile, which adopts the reinforcing system for reinforcing a soft soil layer at the bottom of a large-diameter bored pile.

[0022] The method for reinforcing a soft soil layer at the bottom of a large-diameter bored pile includes the following contents.

[0023] After the large-diameter bored pile is constructed and maintained, the position of the central grouting hole is determined.

[0024] The drilling machine is positioned, the drilling machine and the drill rod are installed at the preset hole position, the central grouting hole is formed by drilling, and the depth of the central grouting hole is greater than the depth of the large-diameter bored pile hole.

[0025] The nozzle is inserted into the central grouting hole, and the bottom of the nozzle is inserted into the soft soil layer below the pile bottom to a set depth.

[0026] The first nozzle is connected with the slurry supply component, the second nozzle is connected with the gas supply component, and the third nozzle is connected with the water supply component. The gas flow is injected through the second nozzle, the water flow is injected through the third nozzle, the soil is cut together to form a gap, and then the slurry with a set pressure is injected through the first nozzle to fill the gap, so that the sludge at the bottom of the large-diameter bored pile, the virtual soil, and the slurry form a consolidated body.

[0027] The drilling machine gradually lifts the nozzle, and the injection is completed when the slurry is discharged at the central grouting hole, and then the nozzle is pulled out.

[0028] After a set time, the central grouting hole is filled.

[0029] The slurry supply component provides the silicate cement slurry to the first nozzle, and different admixtures are added to the silicate cement slurry according to different soft soil layers.

[0030] The beneficial effects of the present application are as follows:

[0031] 1) The reinforcing system structure in the application is reasonable, three nozzles are arranged at the top of the spray pipe, water flow and air flow are sprayed into the spray pipe through two nozzles respectively, the water flow and the air flow enter the soft soil layer at the bottom of the large-diameter bored pile through the spray pipe body, the soil body can be effectively cut, and then cement slurry is sprayed through the other nozzle, the sprayed slurry can be combined with the cut soil body and sediment to form a reinforced body with high strength, the soft soil layer at the bottom of the pile does not need to be dug out, the direct utilization is used to form the reinforced body with high strength at the bottom of the pile, the virtual soil at the bottom of the pile and the sediment are fully utilized, and the environment is not polluted.

[0032] 2) In the application, a hole is drilled in the center of the large-diameter bored pile by using a drilling machine, and a central grouting hole is formed, the spray pipe is inserted into the central grouting hole, water flow, air flow and grouting are realized by using the spray pipe, the spray pipe is used as a triple pipe, the influence on the surrounding environment is small, the sediment is fully utilized, the bearing capacity of the pile foundation is high, and the adaptability is strong.

[0033] 3) In the application, the first nozzle, the second nozzle and the third nozzle are arranged at the top of the spray pipe, so that the sprayed water flow is at the lowest position, the sprayed air flow is at the middle position, the two cut the soil body in advance, the slurry is injected at the same time, and the soil body is combined with the slurry quickly.

[0034] 4) The bottom of the first nozzle is provided with a first opening, the first opening of the first nozzle can be inserted into the first recess of the second nozzle, so as to facilitate the stability of the connection between the first nozzle and the second nozzle, and the bottom of the second nozzle can be inserted into the second recess at the top of the third nozzle, so as to facilitate the reliability of the connection between the second nozzle and the third nozzle.

[0035] 5) The reinforcing method disclosed by the application directly drills a central grouting hole in the center of the large-diameter bored pile, and inserts the spray pipe into the hole, air flow, water flow and slurry can be sprayed through the spray pipe, the drilling process around the pile is simplified, the hole is drilled in the center of the large-diameter bored pile, the structure is simple, the arrangement is flexible, and the operation is convenient; the single-hole drilling construction efficiency of the pile center is high, the construction period can be shortened, and the engineering cost can be saved. BRIEF DESCRIPTION OF DRAWINGS

[0036] The drawings accompanying the specification of the application form a part of the application and serve to further provide a further understanding of the application, the illustrative embodiments of the application and the explanations thereof serve to explain the application, and do not constitute an improper limitation of the application.

[0037] Figure 1 is a schematic view of a soft soil layer reinforcing system at the bottom of a large-diameter bored pile according to one or more embodiments of the application.

[0038] Figure 2 is a sectional view of a first nozzle in a soft soil layer reinforcing system at the bottom of a large-diameter bored pile in embodiment one of the application.

[0039] Figure 3 is a cross-sectional view of a second nozzle in a large-diameter bored pile bottom soft soil layer reinforcement system according to Embodiment 1 of the present application.

[0040] Figure 4 is a cross-sectional view of a third nozzle in a large-diameter bored pile bottom soft soil layer reinforcement system according to Embodiment 1 of the present application.

[0041] Figure 5 is a schematic view of a first nozzle, a second nozzle, and a third nozzle in a large-diameter bored pile bottom soft soil layer reinforcement system according to Embodiment 2 of the present application.

[0042] Figure 6 is a schematic view of a hole drilled in the center of a large-diameter bored pile in a large-diameter bored pile bottom soft soil layer reinforcement method according to Embodiment 3 of the present application.

[0043] Figure 7 is a plan view of a large-diameter bored pile bottom soft soil layer reinforcement method according to Embodiment 3 of the present application during construction.

[0044] In the drawings: the mutual distances or dimensions are exaggerated for showing the positions of the parts, and the schematic views are merely schematic.

[0045] In the drawings: 1. large-diameter bored pile, 2. reinforcement body, 3. pile bottom soft soil layer, 4. center grouting hole, 5. drill rod, 6. nozzle, 7. drilling machine, 8. grouting pump, 9. air compressor, 10. high-pressure water pump, 11. slurry mixer, 12. gas flowmeter, 13. injection mechanism;

[0046] 6-1. first nozzle, 6-2. second nozzle, 6-3. third nozzle, 6-4. nozzle body;

[0047] 6-11. connecting port, 6-12. first housing, 6-13. first opening;

[0048] 6-21. first recess, 6-22. second housing, 6-23. second opening;

[0049] 6-31. second recess, 6-32. third opening, 6-33. third housing, 6-34. bottom opening. DETAILED DESCRIPTION

[0050] It should be noted that the following detailed description is illustrative only, and is intended to provide further description in connection with the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0051] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0052] As introduced in the background, the prior art has a problem that the process for treating the soft soil layer at the bottom of the large-diameter bored pile is complicated, in order to solve the above technical problem, the present application provides a large-diameter bored pile bottom soft soil layer reinforcement system.

[0053] Embodiment one

[0054] In a typical embodiment of the present application, referring to Figure 1 As shown in the figure, a large-diameter bored pile bottom soft soil layer reinforcement system, comprising a spray pipe 6, the spray pipe can be connected with a drilling machine 7, the spray pipe can be inserted into the center grouting hole 4 of the large-diameter bored pile 1, and extend into the pile bottom soft soil layer 3 at the bottom of the large-diameter bored pile;

[0055] The first nozzle 6-1, the second nozzle 6-2 and the third nozzle 6-3 are sequentially arranged from top to bottom at the top of the spray pipe 6, the first nozzle 6-1 is connected with the slurry supply component, the second nozzle 6-2 is connected with the gas supply component, and the third nozzle 6-3 is connected with the water supply component, the second nozzle and the third nozzle are annular, the first nozzle is inserted into the hollow of the second nozzle, the second nozzle is inserted into the hollow of the third nozzle, and the third nozzle is fixedly connected with the spray pipe body 6-4, and the second nozzle and the third nozzle are respectively connected with the first nozzle.

[0056] Among them, it needs to be explained that the large-diameter bored pile 1 is formed by artificial hole digging or mechanical hole forming, the diameter of the large-diameter bored pile 1 is greater than or equal to 0.8m, the hole diameter is slightly larger than the designed pile diameter, and the pile length and the pile diameter of the large-diameter bored pile 1 need to be determined according to the specific construction site and construction requirements.

[0057] The lower part of the large-diameter bored pile 1 is the pile bottom soft soil layer 3 such as virtual soil and sediment.

[0058] The center of the large-diameter bored pile 1 is provided with a center grouting hole 4, the depth and the drilling diameter of the center grouting hole 4 are determined according to the size of the diameter of the large-diameter bored pile 1, the center grouting hole 4 is drilled by using a 50mm drill rod 5 and a drilling machine 7, the depth of the center grouting hole is greater than the pile length of the large-diameter bored pile 1, and the depth is at least 50cm deeper than the large-diameter bored pile.

[0059] It is easily understood that the slurry supply component is the slurry mixer 11, the slurry mixer 11 is connected with the first nozzle 6-1 through the grouting pump 8; the air supply component adopts the air compressor 9, the pipeline connected with the second nozzle is provided with the gas flow meter 12 for obtaining the gas flow at the pipeline; the water supply component is connected with the third nozzle through the water pump, the water supply component supplies the high-pressure water flow to the third nozzle, the water supply component can be a water well or a water tank, and the three nozzles, the slurry mixer, the air compressor and the water pump form the jet mechanism 13.

[0060] In the embodiment, the outer diameters of the first nozzle, the second nozzle and the third nozzle gradually increase, the high-pressure water is jetted from the third nozzle at the lowermost position, the high-pressure gas flow is jetted from the second nozzle at the middle position, and the two are jetted through the nozzle body to finally reach the soft soil layer at the pile bottom to cut the soil body, and finally the cement slurry is jetted from the first nozzle.

[0061] Referring to Figure 2 As shown in the figure, the first nozzle includes a first shell 6-12, the cross section of the first shell is a circular shape, the bottom of the first shell protrudes towards the second nozzle, and the protruding part forms a first opening 6-13 for jetting the cement slurry, and the side of the first shell is provided with a connecting port 6-11 connected with the grouting pump 8, and the first opening is arranged to facilitate the downward jetting of the slurry along the first opening.

[0062] Specifically, the first opening has a set depth, and the shape of the first opening is a circular truncated cone, and the outer diameter of the bottom of the first opening is smaller than the outer diameter of the top of the first opening.

[0063] Referring to Figure 3 As shown in the figure, the second nozzle 6-2 includes a second shell 6-22, the cross section of the second shell 6-22 is a circular ring, the second shell has a set height, the side of the second shell is provided with a gas inlet connected with the air compressor, and the top of the second shell is provided with a first recess 6-21 for supporting the bottom protruding part of the first nozzle, the size of the first recess is matched with the size of the first opening, and the shape of the first recess is also a circular truncated cone, the first recess is engaged with the bottom protruding part of the first nozzle, which is beneficial to the stability of the connection between the two; the first opening of the first nozzle is inserted into the first recess of the second nozzle, and considering the installation space, the second nozzle is welded with the first nozzle;

[0064] In addition, the bottom of the second nozzle is provided with a plurality of second openings 6-23 for jetting the gas flow;

[0065] Referring to Figure 4As shown, the third nozzle 6-3 includes a third shell 6-33 having a set height, a liquid inlet connected with the water pump is arranged at the side of the third shell, the transverse section of the third shell is a circular ring, a second recess 6-31 is arranged at the top of the third shell to support the second nozzle, the outer diameter of the second nozzle is matched with the inner diameter of the second recess of the third shell, the bottom side of the second nozzle can be directly clamped into the second recess, and the arrangement of the second recess facilitates the positioning of the second nozzle and the connection of the second nozzle with the third nozzle.

[0066] A plurality of third openings 6-32 are arranged at the inner side wall of the third nozzle to spray water flow, and the central axis of the third opening is arranged obliquely to the central axis of the third nozzle, so that the third opening sprays water flow obliquely downward.

[0067] To ensure the stability of the connection of the second nozzle with the third nozzle, after the bottom side of the second nozzle is clamped into the second recess, the third nozzle is connected with the second nozzle by welding.

[0068] It is easily understood that the bottom of the third nozzle is arranged protruding downward, and a bottom opening 6-34 is arranged at the protruding position, and the top of the nozzle body 6-4 is inserted into the bottom opening of the third nozzle.

[0069] Specifically, the bottom opening 6-34 is a threaded hole, and the third nozzle is connected with the nozzle body by a threaded structure to realize the connection of the third nozzle with the nozzle body.

[0070] It should be noted that to break the soil, the water pump is a high-pressure water pump, the high-pressure water pump 10 can spray a high-pressure water jet with a pressure ≥ 35 MPa, and the diameter of the third opening can be 2-3 mm; the air compressor 9 sprays a cylindrical air flow with a pressure of 0.5-0.7 MPa through the second nozzle, and the diameter of the second nozzle is 1-2 mm; the diameter of the bottom end of the first opening is 10-20 mm; the nozzle body is a hollow pipe, and the outer diameter of the nozzle body is generally φ75 or φ90 mm.

[0071] In addition, the slurry mixer stirs the water slurry, and the slurry mixer is an existing cement concrete mixing device, and the water-cement ratio of the water slurry before stirring by the slurry mixer is 1:1:1.2.

[0072] In some examples, the device further includes a controller connected with the grouting pump, the slurry mixer, the air supply component, the gas flow meter 12 and the water pump, the controller can be a PLC controller or other types of controllers, the controller controls the opening or closing of each component, and the gas flow at the pipeline is obtained through the gas flow meter, and the controller has a display screen to display the size of the gas flow.

[0073] The device provided by the embodiment sprays and cuts the soil through the coaxial jetting of the high-pressure water jet flow and the airflow by the water pump and the air compressor, forms a larger gap, and then fills the gap by injecting the slurry with a set pressure by the grouting pump 8, so that the sediment at the bottom of the large-diameter bored pile, the virtual soil and the slurry form a consolidated body, effectively treating the sediment at the bottom of the pile while improving the bearing capacity of the pile foundation, and having good market prospect and economic benefit.

[0074] Embodiment two

[0075] The difference between the embodiment and the embodiment one is that:

[0076] Considering the support of the second nozzle to the first nozzle, referring to Figure 5 , the inner diameter of the second nozzle is matched with the outer diameter of the first nozzle to support the first nozzle, and the inner diameter of the third nozzle is matched with the outer diameter of the second nozzle to support the second nozzle, so that the first nozzle is clamped into the second nozzle, and the second nozzle is clamped into the third nozzle.

[0077] The same as the embodiment one is that the bottom of the first nozzle is provided with a grouting hole, the bottom of the second nozzle is provided with an airflow hole, and the sidewall of the third nozzle is provided with a water jet hole, and the position of the water jet hole is lower than the bottom of the second nozzle;

[0078] Moreover, after the first nozzle is inserted into the inner wall of the second nozzle, the two are welded; after the second nozzle is inserted into the inner wall of the third nozzle, the two are welded; in order to limit the position of the first nozzle, a first limiting step can be arranged on the upper side of the inner wall of the second nozzle, the first limiting step can be a first protrusion, and the first protrusion can be an annular protrusion;

[0079] In order to limit the position of the second nozzle, a second limiting step can be arranged on the upper side of the inner wall of the third nozzle, the second limiting step can be a second protrusion, and the second protrusion can be an annular protrusion.

[0080] Embodiment three

[0081] The embodiment discloses a large-diameter bored pile bottom soft soil layer reinforcing method, and adopts the large-diameter bored pile bottom soft soil layer reinforcing system in the embodiment one or the embodiment two.

[0082] A large-diameter bored pile bottom soft soil layer reinforcing method, referring to Figure 6 and Figure 7 , includes the following contents:

[0083] Before construction, the position of the center grouting hole of the large-diameter bored pile should be reviewed according to the site environment;

[0084] After the construction and maintenance of the large-diameter bored pile are completed, the position of the center grouting hole is determined;

[0085] The drilling machine 7 is positioned, the drilling machine and the drill rod 5 are installed at the preset hole position, the drilling machine is connected with the drill rod 5, the drilling machine forms the central grouting hole through the drill rod, and the depth of the central grouting hole is greater than the depth of the large-diameter cast-in-place pile hole;

[0086] The nozzle is inserted into the central grouting hole, the bottom of the nozzle is inserted into the soft soil layer below the pile bottom to a set depth, such as 30-50 mm, to ensure that a larger range of consolidated bodies is formed;

[0087] The first nozzle is connected with the slurry supply component, the second nozzle is connected with the gas supply component, and the third nozzle is connected with the water supply component; the soil body is cut together by jetting the gas flow through the second nozzle and the water flow through the third nozzle to form a gap, and then the slurry under a set pressure is injected through the first nozzle to fill the gap, so that the settled sediment and the virtual soil at the bottom of the large-diameter cast-in-place pile form the consolidated body together with the slurry;

[0088] The drilling machine gradually lifts the nozzle, and the nozzle continuously operates through the first nozzle, the second nozzle and the third nozzle during the lifting process; during the operation process, soil particles will flow out of the ground together with the slurry, and the jetting is completed when only the slurry is discharged from the central grouting hole, and then the nozzle is pulled out;

[0089] After a set time, the central grouting hole is filled with crushed sand and crushed stone.

[0090] Understandably, the slurry supply component provides the silicate cement slurry to the first nozzle, different admixtures are added to the silicate cement slurry according to different soft soil layers, and the admixture can be slag or fly ash or an existing expanding agent, which can effectively improve the performance of the silicate cement to meet the use requirements; moreover, the cement slurry needs to be strictly filtered and provided with two filter screens, the cement slurry needs to be strictly configured according to the mixing ratio, and the cement slurry needs to be pre-screened to remove lumps.

[0091] In the embodiment, to ensure the lifting of the nozzle, the nozzle body is connected with the drilling machine, the drilling machine can drive the drill rod to realize the drilling of the central grouting hole 4, the drill rod 5 is removed after the drilling is completed, and then the nozzle is installed; the lifting speed of the nozzle 6 is 10 cm / min, and the rotating speed is 10 revolutions / min; if no slurry is discharged during the jetting process, the grouting amount should be increased in time, and the lifting is performed after the slurry is returned; when the nozzle in the application is used for jetting and grouting, the amount of slurry discharged (referring to the amount of soil particles discharged out of the ground along with the slurry during the injection of the slurry) needs to be greater than the jetting amount of the high-pressure water, but the excess amount is less than or equal to 20% of the total amount of the injected slurry, and the total amount of the injected slurry is determined according to the diameter of the large-diameter cast-in-place pile 1.

[0092] In addition, the nozzle 6 is installed before the nozzle body is cleaned of debris to avoid clogging the nozzle body, to ensure that the spray is complete, the nozzle 6 oscillation angle is generally 60°-90°; slurry has enough energy to destroy the weak soil layer at the bottom of the pile, the final injection of cement slurry volume according to the diameter of the large diameter bored pile 1 is determined.

[0093] It should be noted that the center of the drill 7 when drilling the center of the pile 1 is aligned with the center of the large diameter bored pile 1 (measured with a hammer), and the level of the drill 7 and the verticality of the drill 7 are adjusted (measured with a ruler), the position error is less than or equal to 5mm, the inclination error is less than or equal to 0.5°.

[0094] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A large-diameter cast-in-place pile bottom soft soil layer reinforcement system, characterized in that, The nozzle is connected with a drilling machine, and is inserted into a central grouting hole of the large-diameter bored pile and extends into a soft soil layer at the bottom of the large-diameter bored pile. The first nozzle is connected with the slurry supply component, the second nozzle is connected with the gas supply component, and the third nozzle is connected with the water supply component. The first nozzle includes a first shell, the bottom of the first shell protrudes towards the second nozzle, and a first opening is formed at the protruding position to spray cement slurry. The bottom of the second nozzle is provided with a plurality of second openings to spray gas flow. The inner wall of the third nozzle is provided with a plurality of third openings to spray water flow.

2. The soft soil layer reinforcement system for a large-diameter cast-in-place pile according to claim 1, characterized in that, The bottom of the third nozzle is protruding downward, and a bottom opening is formed at the protruding position. The bottom opening is a threaded hole, and the third nozzle is connected with the nozzle body through a threaded structure.

3. The system for reinforcing soft soil layer at the bottom of a large-diameter cast-in-place pile according to claim 1, characterized in that, The top of the second nozzle is provided with a first recess to support the bottom protruding position of the first nozzle. The second nozzle is connected with the first nozzle through welding.

4. The system for reinforcing soft soil layer at the bottom of a large-diameter cast-in-place pile according to claim 1, characterized in that, The top of the third nozzle is provided with a second recess to support the second nozzle. The third nozzle is connected with the second nozzle through welding or fasteners.

5. The system for reinforcing soft soil layer at the bottom of a large-diameter cast-in-place pile according to claim 1, characterized in that, The slurry supply component is a slurry mixer, which is connected with the first nozzle through a grouting pump. The water supply component is connected with the third nozzle through a water pump.

6. The system for reinforcing soft soil layer at the bottom of a large-diameter cast-in-place pile according to claim 1, characterized in that, The inner diameter of the second nozzle is matched with the outer diameter of the first nozzle to support the first nozzle, and the inner diameter of the third nozzle is matched with the outer diameter of the second nozzle to support the second nozzle.

7. A method for reinforcing a weak soil layer at the bottom of a large-diameter cast-in-place pile, characterized by, The large-diameter bored pile bottom soft soil layer reinforcement system of any one of claims 1-6 is adopted.

8. The method according to claim 7, wherein the method is characterized by, The following contents are included: After the large-diameter bored pile is constructed and maintained, the position of the central grouting hole is determined; The drilling machine is positioned, the drilling machine and the drill rod are installed at the preset hole position, the hole is drilled to form the central grouting hole, and the depth of the central grouting hole is greater than the depth of the large-diameter bored pile hole; The nozzle is inserted into the central grouting hole, and the bottom of the nozzle is inserted into the soft soil layer below the bottom of the pile to a set depth; The first nozzle is connected with the slurry supply component, the second nozzle is connected with the gas supply component, and the third nozzle is connected with the water supply component. The soil is cut by the gas flow sprayed through the second nozzle and the water flow sprayed through the third nozzle to form a void, and then the first nozzle is used to inject slurry at a set pressure to fill the void. The drilling machine gradually lifts the nozzle, and the nozzle is pulled out when the slurry is discharged at the central grouting hole.

9. The method according to claim 8, wherein the method is characterized by, After a set time, the central grouting hole is filled. The slurry supply component provides silicate cement slurry to the first nozzle, and different admixtures are added to the silicate cement slurry according to different soft soil layers.

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