An inclined-axis multi-plane three-dimensional mixing drill and construction method

Abstract

The present application provides an inclined-axis multi-plane three-dimensional mixing drill and a construction method, wherein the three-dimensional mixing drill comprises a top flange, and an upper horizontal mixing assembly, an oblique mixing assembly, and a lower horizontal mixing assembly sequentially arranged thereon; the upper horizontal mixing assembly comprises an upper core tube and a plurality of upper horizontal mixing blades; the oblique mixing assembly comprises a middle core tube and a plurality of oblique mixing blades that rotate obliquely with the tube; the lower horizontal mixing assembly comprises a lower core tube and a plurality of lower horizontal mixing blades and a plurality of toothed blades; the upper core tube, the middle core tube, and the lower core tube are connected together to form a grouting pipe, and the side wall of the lower core tube is provided with a slurry outlet connected to the grouting pipe. The present application enhances the three-dimensional mixing performance by providing the upper horizontal mixing blade, the oblique mixing blade, the lower horizontal mixing blade, and the toothed blade, which can promote the mixing of soil and mortar in the radial direction of the pile and promote the uniformity of the cohesion degree on the cross section of the pile body.

Description

Technical Field

[0001] The present application relates to the technical field of mixing pile construction, and in particular to an inclined-axis multi-plane three-dimensional mixing drill and a construction method. Background Art

[0002] Mixing piles are a common reinforcement method for soft soil foundations. During construction, the drill rod is braked, which drives the mixing blades to rotate, cutting the soil and mixing it with the sprayed curing agent. Through repeated sinking and lifting of the drill rod, a pile with a certain strength and rigidity is eventually formed in the soft foundation, thereby improving the bearing capacity. However, for the mudflats and silt sites involved in land reclamation projects, the geological conditions are complex and the spatial properties of the soft soil vary greatly, making it difficult to control the mixing uniformity. Using conventional mixing drill tools reduces construction efficiency and cannot guarantee the construction quality.

[0003] In response to the above problems, drilling tool research and development is committed to improving mixing performance. Among the related technologies, the Chinese patent application number 202210986306.3 proposes a three-dimensional deep mixing drilling tool and construction method. In addition to the horizontal plane, the drilling tool also has the ability to mix on the vertical plane, which can enhance the axial uniformity of the mixing pile.

[0004] However, horizontal mixing, using the drill rod as the axis, essentially involves mixing along the circumference of the pile core. This does not directly promote the flow and mixing of premixed soft soil along the pile diameter, and its mixing capacity is particularly weak near the pile core. Vertical mixing, on the other hand, has a small radial component and weak mixing capacity along the pile diameter. Furthermore, insufficient mixing along the pile diameter makes it difficult to ensure uniform hardening across the horizontal cross-section of the pile, effectively reducing the effective load-transfer area and limiting the pile's vertical bearing capacity. Summary of the Invention

[0005] In order to improve the problem of insufficient mixing in the pile diameter direction during existing mixing pile construction and difficulty in ensuring uniform hardening degree on the horizontal cross section of the pile body, the present application provides an inclined-axis multi-plane three-dimensional mixing drill and a construction method.

[0006] In the first aspect, the present application provides an inclined-axis multi-plane three-dimensional stirring drill, which adopts the following technical solution:

[0007] An inclined-axis multi-plane three-dimensional stirring drill tool comprises a top flange, on which an upper horizontal stirring assembly, an oblique stirring assembly, and a lower horizontal stirring assembly are sequentially arranged from top to bottom;

[0008] The upper horizontal stirring assembly includes an upper core tube and a plurality of upper horizontal stirring blades that rotate with the top flange;

[0009] The oblique stirring assembly includes a middle core tube that rotates with the top flange and a plurality of oblique stirring blades that rotate obliquely with the rotation;

[0010] The lower horizontal stirring assembly includes a lower core tube rotating with the top flange, a plurality of lower horizontal stirring blades, and a plurality of toothed blades;

[0011] The upper core tube, the middle core tube and the lower core tube are connected together to form a grouting pipeline, and the side wall of the lower core tube is provided with a slurry outlet hole connected to the grouting pipeline.

[0012] Furthermore, a middle shell is provided on the outer rotating sleeve of the middle core tube, a transmission cavity is reserved between the middle shell and the middle core tube, and an upper bearing and a lower bearing are provided at both ends of the transmission cavity, which are used to realize the rotation connection between the middle core tube and the middle shell and bear radial load;

[0013] An upper thrust cylindrical roller bearing and a lower thrust cylindrical roller bearing are respectively provided on opposite sides of the upper bearing and the lower bearing, and are used to realize the relative rotation of the middle core tube and the middle shell and bear the axial load;

[0014] A plurality of oblique rotating shafts are rotatably mounted on the middle shell, and oblique stirring blades are mounted on the oblique rotating shafts. A transmission structure for transmitting the rotational power of the middle core tube relative to the middle shell to the oblique rotating shafts is provided in the transmission cavity.

[0015] Furthermore, the transmission structure includes:

[0016] A flat crown gear is coaxially sleeved and fixed on the outer wall of the middle core tube located in the transmission cavity;

[0017] The driven bevel gear is coaxially fixed to one end of the oblique rotating shaft extending into the transmission cavity, and is meshed with the plane crown gear.

[0018] Furthermore, a plurality of tapered roller bearings are arranged between the oblique rotating shaft and the inner wall of the middle shell, and two adjacent tapered roller bearings are arranged in opposite directions.

[0019] In a second aspect, the present application provides a construction method for an inclined-axis multi-plane three-dimensional stirring drill tool, based on the above-mentioned inclined-axis multi-plane three-dimensional stirring drill tool, comprising the following steps:

[0020] S1. Determine the drill pipe speed (q) and sinking rate (v) based on the three-dimensional stirring resistance experienced by the upper horizontal stirring blade, the oblique stirring blade, the lower horizontal stirring blade, and the toothed blade during soil cutting and mixing. The top flange is mounted on the drill pipe, and the drill is lowered to the pile bottom elevation. Simultaneously, determine the drill pipe's lifting rate (v1) and sinking rate (v2) for crossing the fast zone, and the lifting rate (v3) and sinking rate (v4) for crossing the slow zone, where 0.4 m / min < v3 < v4 ​​= v = v1 < v2 < 1.2 m / min.

[0021] S2. Shotcrete mixing at the pile bottom: stop drilling and mixing at the pile bottom elevation, spray at the rated flow rate for 30 seconds, and inject the slurry into the soft soil through the grouting pipe and the slurry outlet;

[0022] S3. Variable-rate drill lift and shotcrete mixing: When the drill is lifted to the high-speed zone, the drill string is driven by the drill pipe to lift the drill string at a rate of v1 while simultaneously stirring and shotcreting. When the drill is lifted to the low-speed zone, the drill string is driven by the drill pipe to lift the drill string at a rate of v3 while simultaneously stirring and shotcreting. The ratio of the pumping flow rates in the high-speed zone to the low-speed zone is set to v1 / v3, i.e., the amount of shotcrete per linear meter is maintained constant during the drill lift process.

[0023] S4. Variable-rate drilling and shotcreting. After hoisting to the pile top elevation, drill down. When drilling into the high-speed zone, the drill rod drives the drill tool down at a rate of v2 while simultaneously agitating and shotcreting. When drilling into the low-speed zone, the drill rod drives the drill tool down at a rate of v4 while simultaneously agitating and shotcreting. The pumping flow rate ratio between the high-speed and low-speed zones is set to v2 / v4, maintaining a constant shotcrete volume per linear meter during drilling.

[0024] S5. Stop drilling, raise and move the pile driver. After sinking to the pile bottom elevation, stop mixing and spraying, raise the drill rod, clean it and move to the next pile position.

[0025] Furthermore, in step S1, based on the geological survey results, the depth ranges of the soft soil layer, the low-water content clay layer, and the silty / sandy hard soil layer are divided, and the depth of the soil layer interface is determined; the soft soil layer is divided into a low-speed drilling zone, and the low-water content clay layer and the silty / sandy hard soil layer are divided into a high-speed drilling zone;

[0026] In the silty / sandy hard soil layer, the drill rod rotation rate is reduced to q1, where q1 = 0.5q; in the low-water content clay layer, the drill rod rotation rate is changed to q2, where q2>q.

[0027] Furthermore, when the drill rod passes through the soil interface, the drilling rate is controlled to be v5 within a depth range of 0.5m above and below the soil interface, where v5 = 0.5v.

[0028] Furthermore, in step S1, control the drill pipe to cut and sink into the soil at the reference drill pipe rotation speed q and sinking rate v until the pile bottom elevation. During the downhole empty mixing process, the upper horizontal mixing blades, diagonal mixing blades, lower horizontal mixing blades, and toothed blades are resisted during the process of cutting and mixing the soil, and jointly feedback to the drill pipe current. Use an ammeter to collect the current data and output it to the monitoring system;

[0029] According to the change of the drill pipe current with depth monitored, if the current is stable, it indicates that the soil quality is uniform and easy to mix, and the corresponding depth range is divided into the fast drill pipe penetration area; if the current changes sharply or is unstable, it indicates the presence of a soil layer interface or poor soil uniformity and difficult to mix, and the corresponding depth range is divided into the slow drill pipe penetration area.

[0030] Furthermore, in step S3, synchronously monitor the drill pipe current and correct the depth intervals of the fast and slow drill pipe penetration areas; in step S4, synchronously monitor the drill pipe current. If the current is basically stable, continue to execute step S5, otherwise correct the depth intervals of the fast and slow drill pipe penetration areas and re-mix.

[0031] Furthermore, according to the geological exploration results, if it is all soft soil layer, change to the following construction method:

[0032] P1. Drill down and spray lime for mixing, control the drill pipe to cut and sink into the soil at the reference drill pipe rotation speed q and sinking rate v until the pile bottom elevation. Spray lime during the downhole process, and the lime powder is pressed into the soft foundation through the slurry injection pipeline from the slurry outlet hole; control the lime delivery pressure p1 within the depth range of 8 m, where 0.4 MPa < p1 < 0.5 MPa. After the depth is greater than 8 m, increase the lime delivery pressure to p2, where p1 < p2 < 0.6 MPa;

[0033] P2. Spray lime for mixing at the pile bottom, stop drilling when reaching the pile bottom elevation and control the drill pipe to rotate and mix at a conventional speed q for 30 s. Spray lime at the rated lime delivery pressure during the mixing process;

[0034] P3. Lift the drill pipe and spray lime for mixing, control the drill pipe to lift at the reference drill pipe rotation speed q and sinking rate v until the pile top elevation. Spray lime during the lifting process, and the lime powder is pressed into the soft foundation through the slurry injection pipeline from the slurry outlet hole; control the lime delivery pressure p1 within the depth range of 8 m, where 0.4 MPa < p1 < 0.5 MPa. After the depth is greater than 8 m, increase the lime delivery pressure to p2, where p1 < p2 < 0.6 MPa;

[0035] [[ID=(21]]P4. Move the pile driver, lift to the pile top elevation, stop mixing and spraying lime, lift out and clean, and then move to the next pile position.

[0036] In summary, the present application includes at least one of the following beneficial technical effects:

[0037] 1. Four non-parallel mixing planes expand the three-dimensional mixing space, enhance the mixing capacity and three-dimensional characteristics, and help reduce the spatial anisotropy of the mixing pile. At the same time, the multi-plane and multi-angle three-dimensional mixing method can sensitively sense the mixing resistance in the space rather than in a single plane or direction, and effectively reflect the soil properties through the drill pipe current, which is more conducive to the joint monitoring system for the refined construction of mixing piles.

[0038] 2. Oblique mixing can mix the soil and curing agent along the axial and radial directions of the pile, enhancing the uniformity of the hardening degree in the axial direction and cross section of the pile, overcoming the adverse effects of local soil unevenness and stratum interface on the continuity of pile formation, thereby expanding the effective load transfer area, increasing the vertical load transfer efficiency and improving the vertical bearing capacity of the pile;

[0039] 3. The upper horizontal stirring assembly and the lower horizontal stirring assembly are respectively connected to the middle assembly through threads and matched with U-shaped pins to prevent loosening, which provides convenience for disassembly and ensures the smooth flow and good sealing of the injection pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present application;

[0042] Figure 2 This is a side view of the overall structure of an embodiment of the present application;

[0043] Figure 3 is a schematic cross-sectional structural diagram of an embodiment of the present application;

[0044] Figure 4 2 is a schematic cross-sectional view of the connection between the upper core tube and the middle core tube of an embodiment of the present application;

[0045] Figure 5 A construction flow chart of a mixing pile construction method adapted to stratum conditions according to an embodiment of the present application;

[0046] Figure 6 This is a construction flow chart of the refined construction method of mixing piles with combined current monitoring according to an embodiment of the present application;

[0047] Figure 7 This is a construction flow chart of the high-moisture-content soft base powder injection pile construction method of an embodiment of the present application.

[0048] Reference numerals:

[0049] 1. Upper horizontal stirring assembly; 101. Top flange; 102. Upper core tube; 103. Upper horizontal stirring blade; 104. Upper faceted bolt; 105. Upper U-shaped pin;

[0050] 2. Middle assembly; 201. Upper end hole nut; 202. Middle core tube; 203. Middle housing; 204. Core tube seal; 205. Upper bearing; 206. Upper end thrust cylindrical roller bearing; 207. Flat crown gear; 208. Tapered roller bearing; 209. Oblique seal; 210. Lower end thrust cylindrical roller bearing; 211. Lower bearing; 212. Lower end hole nut;

[0051] 3. Lower horizontal stirring assembly; 301. Lower chamfered bolt; 302. Lower U-shaped pin; 303. Lower core tube; 304. Lower horizontal stirring blade; 305. Toothed blade;

[0052] 4. Oblique stirring assembly; 401. Driven bevel gear; 402. Oblique rotating shaft; 403. Oblique stirring blade;

[0053] 5. Grouting pipe; 501. Grouting hole. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0055] Reference Figure 1 、 Figure 2 and Figure 3 The embodiment of the present application discloses an inclined-axis three-dimensional stirring drill tool, which includes a top flange 101 and an upper horizontal stirring component 1, a middle component 2, and a lower horizontal stirring component 3 arranged on the top flange 101 in sequence, and an inclined stirring component 4 is arranged on the middle component 2.

[0056] The upper horizontal stirring assembly 1 includes an upper core tube 102 that rotates with the top flange 101 and a plurality of upper horizontal stirring blades 103.

[0057] The middle component 2 includes:

[0058] The middle core tube 202 is used to connect with the upper horizontal stirring assembly 1 and the lower horizontal stirring assembly 3;

[0059] The middle shell 203 is rotatably sleeved on the outer peripheral wall of the middle core tube 202, and a transmission cavity is reserved between the middle shell 203 and the middle core tube 202;

[0060] The upper bearing 205 and the lower bearing 211 are respectively arranged at both ends of the transmission cavity, and are used to realize the rotational connection between the middle core tube 202 and the middle housing 203, and to bear radial loads. Specifically, the upper bearing 205 and the lower bearing 211 are cylindrical roller bearings, which can bear large radial loads; and

[0061] The upper thrust cylindrical roller bearing 206 and the lower thrust cylindrical roller bearing 210 are arranged on opposite sides of the upper bearing 205 and the lower bearing 211, respectively, for realizing the relative rotation between the middle core tube 202 and the middle shell 203, and bearing the axial load.

[0062] The oblique stirring assembly 4 includes:

[0063] Multiple oblique rotating shafts 402 are provided, which are arranged obliquely and rotatably mounted on the middle housing 203. Specifically, the angle between the oblique rotating shaft 402 and the middle core tube 202 is set to 30° to 60°. In this embodiment, there are three oblique rotating shafts 402, and the angles between the axes of the three oblique rotating shafts 402 are equal.

[0064] A plurality of oblique stirring blades 403 are provided, which are fixed to one end of the oblique rotating shaft 402 located outside the middle shell 203; and

[0065] The transmission structure is provided between the oblique rotating shaft 402 and the middle core tube 202 , and is used to transmit the rotational power of the middle core tube 202 relative to the middle shell 203 to the oblique rotating shaft 402 .

[0066] The lower horizontal stirring assembly 3 includes a lower core tube 303 that rotates with the top flange 101 and a plurality of lower horizontal stirring blades 304 and a plurality of toothed blades 305 fixed on the lower core tube 303; the upper core tube 102, the middle core tube 202 and the lower core tube 303 are connected together to form a grouting pipe 5, and the side wall of the lower core tube 303 is provided with a slurry outlet hole 501 connected to the grouting pipe 5.

[0067] In this way, after the stirring drill tool of the present application is installed on the drill pipe, the middle core tube 202 follows the rotation, and with the help of the setting of the upper end thrust cylindrical roller bearing 206 and the lower end thrust cylindrical roller bearing 210, the middle core tube 202 and the middle shell 203 can cause relative rotation during rotation; thus, compared with the middle shell 203, the middle core tube 202 rotates on it, and then the rotational power is transmitted to the multiple inclined rotating shafts 402 on the middle shell 203 through the transmission structure, so that the multiple inclined rotating shafts 402 rotate synchronously with the middle core tube 202, and then the multiple inclined stirring blades 403 on different inclined rotating shafts 402 perform oblique stirring. Such oblique stirring can not only mix the soil at different depths, but also promote the mixing of soil and mortar in the radial direction of the pile, promote the uniformity of the degree of coagulation on the cross section of the pile, thereby expanding the effective load transfer area and improving the vertical load transfer efficiency, and improving the vertical bearing performance of the pile.

[0068] In order to ensure the stable rotation of the oblique shaft 402 on the middle shell 203, refer to Figure 3 , the transmission structure includes:

[0069] The flat crown gear 207 is coaxially sleeved and fixed on the outer wall of the middle core tube 202 located in the transmission cavity;

[0070] The driven bevel gear 401 is coaxially fixed to one end of the oblique rotating shaft 402 extending into the transmission cavity, and is meshed with the flat crown gear 207 .

[0071] A plurality of tapered roller bearings 208 are disposed between the oblique rotating shaft 402 and the inner wall of the middle housing 203 , with adjacent tapered roller bearings 208 disposed in opposite directions.

[0072] The flat crown gear 207 on the central core tube 202 can simultaneously drive the rotation of multiple driven bevel gears 401, thereby achieving stable rotation of multiple oblique shafts 402. Furthermore, the arrangement of two oppositely-oriented tapered roller bearings 208 provides strong centering for the oblique shafts 402 as they rotate on the central housing 203, ensuring the stability of the tilted oblique shafts 402 during rotation.

[0073] In addition, refer to Figure 3 An oblique sealing ring 209 is provided between the end of the oblique rotating shaft 402 near the oblique stirring blade 403 and the central housing 203. A core tube sealing ring 204 is provided between the upper and lower portions of the central housing 203 and the outer peripheral wall of the central core tube 202. This improves the sealing performance of the transmission cavity and prevents external slurry from seeping into the central housing 203 and affecting the stability of the transmission components.

[0074] And, refer to Figure 1 、 Figure 2 and Figure 3 The top flange 101 of the upper horizontal stirring assembly 1 is bolted to the upper drill pipe for transmission. The toothed blades 305 of the lower horizontal stirring assembly 3 are shorter than the lower horizontal stirring blades 304 and are inlaid with alloy teeth. The bottom end of the lower core tube 303 is tapered to facilitate the insertion and sinking of the drill tool. The upper core tube 102, the middle core tube 202, and the lower core tube 303 are sequentially detachably connected, and their hollow portions are connected to form the aforementioned grouting pipe 5.

[0075] In this way, by setting the upper horizontal stirring blade 103, the oblique stirring blade 403, the lower horizontal stirring blade 304 and the toothed blade 305, four non-parallel stirring plane directions can be formed, which expands the three-dimensional stirring space of the stirring drill tool of the present application, enhances the three-dimensional stirring performance, and can further reduce the spatial anisotropy of the stirring pile.

[0076] Specifically, refer to Figure 3 The two ends of the middle core tube 202 are respectively connected to the upper end opening nut 201 and the lower end opening nut 212, the bottom end of the upper core tube 102 is connected to the upper chamfered bolt 104 threadedly adapted to the upper end opening nut 201, and the top end of the lower core tube 303 is connected to the lower chamfered bolt 301 threadedly adapted to the lower end opening nut 212;

[0077] An upper U-shaped pin 105 is passed through the upper end opening nut 201, and a lower U-shaped pin 302 is passed through the lower end opening nut 212. The upper U-shaped pin 105 and the lower U-shaped pin 302 are respectively in contact with the chamfered surfaces of the upper chamfered bolt 104 and the lower chamfered bolt 301.

[0078] In this way, when assembling the stirring drill tool of the present application, the upper faceted bolt 104 is threadedly connected to the upper end hole nut 201 to connect the upper core tube 102 and the middle core tube 202. The upper U-shaped pin 105 can prevent the two from being loosened after being screwed together, thereby preventing the stirring drill tool of the present application from being separated during rotation. The lower faceted bolt 301 is threadedly connected to the lower end hole nut 212 to connect the middle core tube 202 and the lower core tube 303. The lower U-shaped pin 302 can prevent the two from being loosened after being screwed together, thereby preventing the stirring drill tool of the present application from being separated during rotation. In this way, the upper core tube 102, the middle core tube 202 and the lower core tube 303 can be easily assembled and disassembled, providing convenience for disassembly, while ensuring that the grouting pipe 5 is unobstructed and well sealed.

[0079] The present application also discloses a method for constructing an inclined-axis multi-plane three-dimensional stirring drill tool. Based on the above-mentioned inclined-axis multi-plane three-dimensional stirring drill tool, the following technical solution is adopted:

[0080] A construction method for an inclined-axis multi-plane three-dimensional mixing drill, referring to Figure 5 and Figure 6 , includes the following steps:

[0081] S1. Zoning and speed setting: Based on the three-dimensional mixing resistance suffered by the upper horizontal mixing blade 103, the inclined mixing blade 403, the lower horizontal mixing blade 304 and the toothed blade 305 during the process of cutting and mixing the soil, set the reference drill pipe rotation speed q and sinking rate v, where 40 r / min < q < 80 r / min, and 0.4 m / min < v < 0.8 m / min; and install the top flange onto the drill pipe and drill down to the pile bottom elevation; at the same time, determine the drill pipe lifting rate v1 and sinking rate v2 when passing through the fast zone, and the drill pipe lifting rate v3 and sinking rate v4 when passing through the slow zone, where 0.4 m / min < v3 < v4 = v = v1 < v2 < 1.2 m / min.

[0082] S2. Jet grouting and mixing at the pile bottom: Stop drilling and mix at the pile bottom elevation, spray grout at the rated flow rate for 30 s, and the grout is injected into the soft foundation soil through the grouting pipe 5 from the grout outlet 501.

[0083] S3. Lifting the drill with variable speed and jet grouting and mixing: When lifting the drill to the fast zone, drive the drill tool to lift at a rate of v1 through the drill pipe, and at the same time mix and spray grout; when lifting the drill to the slow zone, drive the drill tool to lift at a rate of v3 through the drill pipe, and at the same time mix and spray grout; and the ratio of the pumping flow rates in the fast zone to the slow zone is set as v1 / v3, that is, keep the grout injection volume per meter unchanged during the drill lifting process, and the corresponding pumping pressure is determined through pre-test piling; stop lifting the drill, mixing and spraying grout after reaching the pile top elevation.

[0084] S4. Lowering the drill with variable speed and jet grouting and mixing: After lifting to the pile top elevation, lower the drill. When lowering the drill to the fast zone, drive the drill tool to sink at a rate of v2 through the drill pipe, and at the same time mix and spray grout; when lowering the drill to the slow zone, drive the drill tool to sink at a rate of v4 through the drill pipe, and at the same time mix and spray grout; and the ratio of the pumping flow rates in the fast zone to the slow zone is set as v2 / v4, that is, keep the grout injection volume per meter unchanged during the drill lowering process, and the corresponding pumping pressure is determined through pre-test piling; stop lowering the drill, mixing and spraying grout after reaching the pile bottom elevation.

[0085] S5. Stop drilling, lift the drill and move the pile driver: After sinking to the pile bottom elevation, stop mixing and spraying grout and lift the drill pipe, and after cleaning, move to the next pile position.

[0086] In specific construction, according to the actual construction conditions, a refined construction method for mixing piles with combined current monitoring or a construction method for mixing piles adapted to the formation conditions can be adopted, or a combination of the two construction methods can be used for construction.

[0087] Specifically, in the construction method for mixing piles adapted to the formation conditions, referring to Figure 5, step S1 specifically includes:

[0088] S11a. Delineate the soil layers. Based on geological survey results, define the depth ranges of soft soil layers, low-moisture clay layers, and silty / sandy hard soil layers. Also, clearly define the depth of the soil layer interfaces. Soft soil layers are designated as the low-speed drill rod penetration zone, while low-moisture clay layers and silty / sandy hard soil layers are designated as the high-speed drill rod penetration zone. Soft soil layers are defined as soil layers with a moisture content above the liquid limit and above 40%, and low-moisture clay layers are defined as soil layers with a moisture content below the liquid limit or below 40%.

[0089] S12a. Drill down and mix, and drill down to the pile bottom elevation according to the set rotation speed and drilling rate of the drill rod passing through the low-speed zone and the high-speed zone.

[0090] During the process of lifting and lowering the drill, the drill rod rotation rate is reduced to q1 when passing through the silty / sandy hard soil layer, where q1=0.5q. In addition, water can be injected in an appropriate amount when the excavation slows down to improve the mixing properties; when passing through the low-water-content clay layer, the drill rod rotation rate is changed to q2, where q2>q.

[0091] In addition, when the drill rod passes through the soil layer interface, the drilling rate is controlled to be v5 within a depth range of 0.5m above and below the soil layer interface, where v5 = 0.5v. At the same time, based on the three-dimensional stirring function of the three-dimensional stirring drill tool of this application, the number of stirring times per meter depth is increased to improve the continuity at the soil layer interface.

[0092] For step S2, if the pile bottom elevation is located in the silty / sandy hard soil layer, the drill rod rotation rate is changed to q1, where q1 = 0.5q; at the same time, grouting is performed at the rated flow rate for 30 seconds, and the mortar is injected into the soft soil through the grouting pipe and the slurry outlet hole.

[0093] In the refined construction method of mixing piles with combined current monitoring, Figure 6 , step S1 specifically includes:

[0094] S11b. Drill down for mixing and monitor the drill pipe current. First, control the drill pipe to cut and sink the soil at a reference drill pipe rotation speed q and sinking rate v until the pile bottom elevation. During the drilling and air mixing process, the upper horizontal mixing blade 103, the oblique mixing blade 403, the lower horizontal mixing blade 304 and the toothed blade 305 are subjected to resistance in the process of cutting and mixing the soil and are collectively fed back to the drill pipe current. The current data is collected using an ammeter and output to the monitoring system. Since the three-dimensional mixing drill tool of the present application has three-dimensional mixing characteristics, the collected current reflects the stirring resistance in the corresponding space rather than the stirring resistance in a specific direction or plane, thereby enhancing sensitivity and reliability.

[0095] S12b. Divide the depth intervals based on the monitored changes in drill pipe current with depth. If the current is stable, it indicates that the soil is uniform and easy to mix. The corresponding depth range is divided into the fast drill pipe crossing zone. If the current changes sharply or is unstable, it indicates the presence of a soil interface or poor soil uniformity, making mixing difficult. The corresponding depth range is divided into the slow drill pipe crossing zone.

[0096] In addition, step S3 also includes S31. Monitoring the drill current and correcting the depth interval, synchronously monitoring the drill rod current and correcting the depth interval of the drill rod passing through the fast zone and the low speed zone; step S4 also includes S41. Monitoring the drill current and verifying the stirring effect, synchronously monitoring the drill rod current, if the current is basically stable, continue to execute step S5, otherwise correct the drill rod to pass through the depth interval of the fast zone and the low speed zone and re-stir.

[0097] Therefore, according to the characteristics of the two construction methods, the refined construction method of mixing piles with combined current monitoring and the construction method of mixing piles adapted to stratum conditions, the construction method of mixing piles adapted to stratum conditions can divide the drill rod crossing the fast-speed zone and the low-speed zone of the target pile position in advance according to the geological survey results, and set the corresponding drilling rate near the soil layer interface, which is suitable for high-efficiency construction under relatively simple geological conditions.

[0098] The refined construction method of mixed piles with combined current monitoring relies on the current collection and monitoring during the first air-mixing drilling to feedback and determine whether the drill rod at the target pile position passes through the fast zone and the low-speed zone. Although the air-mixing drilling process is added compared to the mixed pile construction method that adapts to the formation conditions, the division of the drill rod at the target pile position through the fast zone and the low-speed zone through current monitoring feedback is more accurate. Moreover, during the drilling and lifting process, this current monitoring feedback mechanism works in real time, which can realize the instant adjustment of the drill rod rotation speed and the drilling rate or the lifting rate. It has higher flexibility and accuracy, can greatly promote the uniformity of the hardening degree of the pile body in the axial and cross-section, overcome the adverse effects of local soil unevenness and formation interface on the continuity of pile formation, and thus expand the effective load transfer area, improve the vertical load transfer efficiency and improve the vertical bearing performance of the pile body. It is especially suitable for construction in complex formations or when the geological survey results are less representative.

[0099] Therefore, in some projects with higher construction requirements, the above two methods can be further combined. For example, with the help of geological survey results, the drill rod of the target pile position can be divided into a fast-speed zone and a low-speed zone in advance, and the soil layer interface can be determined, and the drilling can be controlled to be constructed according to the above steps according to the set corresponding rotation speed and drill lowering rate or drill lifting rate; and in the process of drilling and lifting the drill rod, the drill rod current can be monitored synchronously with the help of the current monitoring feedback mechanism, and the preset corresponding drill rod crossing fast zone and low-speed zone can be corrected. This can further improve the flexibility and precision of the construction on the basis of ensuring construction efficiency.

[0100] On the other hand, according to the geological exploration results, if the target pile positions are all soft soil layers, the construction method of dry jet mixing piles with high water content soft foundation is adopted. Refer to Figure 7 , and the construction is carried out according to the following method:

[0101] P1. Drill and spray lime for mixing, control the drill pipe to cut into the soil and sink at the reference drill pipe rotation speed q and sinking rate v until the pile bottom elevation. Among them, 40 r / min < q < 80 r / min, 0.4 m / min < v < 0.8 m / min; spray lime during the down-drilling process, and the lime powder is pressed into the soft foundation through the grouting pipeline 5 from the slurry outlet hole 501; control the lime feeding pressure p1 within the depth range of 8 m, where 0.4 MPa < p1 < 0.5 MPa, and increase the lime feeding pressure to p2 after the depth is greater than 8 m, where p1 < p2 < 0.6 MPa;

[0102] P2. Spray lime for mixing at the pile bottom, sink to the pile bottom elevation, stop drilling, and control the drill pipe to rotate and mix at the normal rate q for 30 s, and spray lime at the rated lime feeding pressure during the mixing process;

[0103] P3. Lift the drill pipe and spray lime for mixing, control the drill pipe to lift at the reference drill pipe rotation speed q and sinking rate v until the pile top elevation. Spray lime during the lifting process, and the lime powder is pressed into the soft foundation through the grouting pipeline 5 from the slurry outlet hole 501; control the lime feeding pressure p1 within the depth range of 8 m, where 0.4 MPa < p1 < 0.5 MPa, and increase the lime feeding pressure to p2 after the depth is greater than 8 m, where p1 < p2 < 0.6 MPa;

[0104] P4. Move the pile driver, lift to the pile top elevation, stop mixing and spraying lime, lift out and clean, and then move to the next pile position.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A construction method for an inclined-axis multi-plane three-dimensional stirring drill, characterized in that: The stirring drill tool includes a top flange, on which an upper horizontal stirring assembly, an oblique stirring assembly, and a lower horizontal stirring assembly are sequentially arranged from top to bottom; The upper horizontal stirring assembly includes an upper core tube rotating with the top flange and a plurality of upper horizontal stirring blades; The oblique stirring assembly includes a middle core tube that rotates with the top flange and a plurality of oblique stirring blades that rotate obliquely with the rotation; The lower horizontal stirring assembly includes a lower core tube rotating with the top flange, a plurality of lower horizontal stirring blades and a plurality of toothed blades; The upper core pipe, the middle core pipe and the lower core pipe are connected together to form a grouting pipe, and the side wall of the lower core pipe is provided with a slurry outlet hole connected to the grouting pipe; The construction method includes the following steps: S1. Zone-by-zone speed determination: The reference drill pipe speed q and sinking rate v are determined based on the three-dimensional stirring resistance experienced by the upper horizontal mixing blades, oblique mixing blades, lower horizontal mixing blades, and toothed blades during soil cutting and mixing. The top flange is then installed on the drill pipe, and the drill is lowered to the pile bottom elevation. The drill pipe's lifting and lowering rates v1 and v2 are also determined for passage through the high-speed zone, and v3 and v4 for passage through the low-speed zone, where 0.4 m / min < v3 < v4 ​​= v = v1 < v2 < 1.2 m / min. S2. Shotcrete mixing at the pile bottom: Stop drilling and mix at the pile bottom elevation. Shotcrete at the rated flow rate for 30 seconds. The slurry is injected into the soft soil through the grouting pipe and the slurry outlet hole. S3. Variable-rate drill lift and shotcrete mixing: When the drill is lifted to the high-speed zone, the drill string is driven by the drill pipe to lift the drill string at a rate of v1 while simultaneously stirring and shotcreting. When the drill is lifted to the low-speed zone, the drill string is driven by the drill pipe to lift the drill string at a rate of v3 while simultaneously stirring and shotcreting. The ratio of the pumping flow rates in the high-speed zone to the low-speed zone is set to v1 / v3, i.e., the amount of shotcrete per linear meter is maintained constant during the drill lift process. S4. Variable-rate drilling and shotcreting. After hoisting to the pile top elevation, drill down. When drilling into the high-speed zone, the drill rod drives the drill tool down at a rate of v2 while simultaneously agitating and shotcreting. When drilling into the low-speed zone, the drill rod drives the drill tool down at a rate of v4 while simultaneously agitating and shotcreting. The pumping flow rate ratio between the high-speed and low-speed zones is set to v2 / v4, maintaining a constant shotcrete volume per linear meter during drilling. S5. Stop drilling, raise the pile driver, and move it to the next pile location. After sinking to the pile bottom elevation, stop mixing and spraying, raise the drill rod, clean it, and move it to the next pile location. In step S1, the drill rod is controlled to cut and sink the soil at a reference drill rod speed q and sinking rate v until the pile bottom elevation is reached. During the drilling and mixing process, the upper horizontal mixing blade, the oblique mixing blade, the lower horizontal mixing blade, and the toothed blade are subjected to resistance in the process of cutting and mixing the soil, and the resistance is fed back to the drill rod current. The current data is collected by an ammeter and output to the monitoring system. According to the monitored changes in drill rod current with depth, if the current is stable, it means that the soil is uniform and easy to mix, and the corresponding depth range is divided into the drill rod crossing fast zone; if the current changes sharply or is unstable, it means that a soil layer interface appears or the soil is poorly uniform and difficult to mix, and the corresponding depth range is divided into the drill rod crossing slow zone.

2. The construction method of a slant-axis multi-plane three-dimensional stirring drill according to claim 1, characterized in that: An outer rotating sleeve of a middle core tube is provided with a middle housing. A transmission cavity is reserved between the middle housing and the middle core tube. An upper bearing and a lower bearing are respectively arranged at both ends of the transmission cavity. The two are used to realize the rotational connection between the middle core tube and the middle housing and bear radial loads. Upper thrust cylindrical roller bearings and lower thrust cylindrical roller bearings are respectively arranged on two opposite sides of the upper bearing and the lower bearing. The two are used to realize the relative rotation between the middle core tube and the middle housing and bear axial loads. A plurality of inclined rotating shafts are rotatably installed on the middle housing. Inclined stirring blades are installed on the inclined rotating shafts. A transmission structure for transmitting the rotational power of the middle core tube relative to the middle housing to the inclined rotating shafts is arranged in the transmission cavity.

3. The construction method of the inclined-axis multi-plane three-dimensional stirring drill according to claim 2, characterized in that: The transmission structure includes: A flat crown gear coaxially sleeved and fixed on the outer wall of the middle core tube located in the transmission cavity; A driven bevel gear coaxially fixed to one end of the inclined rotating shaft extending into the transmission cavity and meshed with the flat crown gear.

4. The construction method of the inclined-axis multi-plane three-dimensional stirring drill according to claim 2, characterized in that: A plurality of tapered roller bearings are arranged between the inclined rotating shaft and the inner wall of the middle housing. The adjacent two tapered roller bearings are arranged in opposite directions.

5. The construction method of the inclined-axis multi-plane three-dimensional stirring drill according to claim 1, characterized in that: In step S1, according to the geological exploration results, divide the depth ranges of the soft soil layer, the low moisture content clay layer, and the silt / sandy hard soil layer, and at the same time clarify the depth of the soil layer interface; divide the soft soil layer as the low-speed area for the drill pipe to pass through, and divide the low moisture content clay layer and the silt / sandy hard soil layer as the high-speed areas for the drill pipe to pass through; And reduce the rotation rate of the drill pipe to q1 in the silt / sandy hard soil layer, where q1 = 0.5q; change the rotation rate of the drill pipe to q2 in the low moisture content clay layer, where q2 > q.

6. The construction method of the inclined-axis multi-plane three-dimensional stirring drill according to claim 5, characterized in that: When the drill pipe passes through the soil layer interface, control the drilling rate to v5 within a depth range of 0.5 m above and below the soil layer interface, where v5 = 0.5v.

7. The construction method of the inclined-axis multi-plane three-dimensional stirring drill according to claim 1, characterized in that: In step S3, synchronously monitor the current of the drill pipe and correct the depth intervals of the high-speed area and the low-speed area for the drill pipe to pass through; in step S4, synchronously monitor the current of the drill pipe. If the current is basically stable, continue to execute step S5, otherwise correct the depth intervals of the high-speed area and the low-speed area for the drill pipe to pass through and re-stir.

8. The construction method of the inclined-axis multi-plane three-dimensional stirring drill according to claim 1, characterized in that: According to the geological exploration results, if it is all soft soil layer, change to the following construction method: P1. Drill down and spray lime for stirring, control the drill pipe to cut the soil and sink at the reference drill pipe rotation speed q and sinking rate v until the pile bottom elevation. Spray lime during the drill-down process. The lime powder is pressed into the soft foundation through the slurry injection pipeline from the slurry outlet hole; control the lime delivery pressure p1 within a depth range of 8 m, where 0.4 MPa < p1 < 0.5 MPa, and increase the lime delivery pressure to p2 after the depth is greater than 8 m, where p1 < p2 < 0.6 MPa; P2. Spray lime and stir at the pile bottom, sink to the pile bottom elevation, stop drilling, and control the drill pipe to rotate and stir at the conventional speed q for 30 s. Spray lime at the rated lime delivery pressure during the stirring process; P3. Lift the drill pipe and spray lime for stirring, control the drill pipe to lift at the reference drill pipe rotation speed q and sinking rate v until the pile top elevation. Spray lime during the lifting process. The lime powder is pressed into the soft foundation through the slurry injection pipeline from the slurry outlet hole; control the lime delivery pressure p1 within a depth range of 8 m, where 0.4 MPa < p1 < 0.5 MPa, and increase the lime delivery pressure to p2 after the depth is greater than 8 m, where p1 < p2 < 0.6 MPa; P4. Move the pile driver to the pile top elevation, stop mixing and spraying, lift it out and clean it before moving to the next pile position.

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