Non-soil-squeezing prestressed X-shaped pile with expansion head and flow-state solidified soil filling construction method

Abstract

The invention discloses a non-soil-squeezing prestressed X-shaped pile with an expanded head and a flow-state solidified soil filling construction method.The pile body of the X-shaped pile comprises at least one pile section, each pile section comprises a core area located in the center and four flanges arranged around the core area at intervals, and the adjacent flanges are in transition connection through inner arc faces; and the whole section of the X-shaped pile is X-shaped. The X-shaped pile is a drilling implantation pile, the space between the outer side wall of the X-shaped pile and the hole wall of the pile hole is filled with flow state solidified soil, and a prefabricated expansion head is assembled at the bottom of a pile body of the X-shaped pile. The prefabricated expanded head has two assembly modes: firstly, the prefabricated expanded head is arranged in a pile hole, and then an X-shaped pile is implanted; and secondly, the X-shaped pile and the prefabricated expanded head are assembled together outside the pile hole and then are synchronously implanted into the pile hole. According to the construction method, the soil squeezing effect is thoroughly eliminated, the pile foundation bearing capacity is remarkably improved, and the innovative design of the prefabricated expansion head solves the problems of installation difficulty and in-hole connection operation caused by hole bottom buoyancy.

Description

Technical Field

[0001] This invention relates to the field of pile foundation technology, specifically to a non-displacement prestressed X-shaped pile with an enlarged head and a method for filling with fluidized solidified soil. Background Technology

[0002] In pile foundation construction, traditional precast piles (such as PHC pipe piles) are prone to significant soil squeezing when driven by hammer or static pressure, which can lead to soil heave, deformation of underground pipelines, and even cracking of existing buildings, making them unsuitable for sensitive sites.

[0003] Although bored piles do not have a soil displacement effect, there are always shortcomings in the filling scheme of the gap between the pile body and the borehole wall: if commercial concrete is used for filling, not only are the raw material costs high and large vibrating equipment required, but the slag generated during the drilling process cannot be utilized, resulting in resource waste and the burden of transporting solid waste; if simple mud or ordinary plain soil is used for backfilling, the lack of solidification properties of the materials leads to problems such as poor compaction, large settlement in the later stage, and insufficient impermeability, which can easily cause hidden dangers such as pile slippage and groundwater infiltration.

[0004] While existing X-shaped pile technology is gradually being adopted due to its reasonable cross-sectional stress and high pile side friction, there are still shortcomings in the selection and application of filling materials. On the one hand, suitable materials are not selected based on the core requirements of pile foundations, namely "density of gap filling, reliability of bonding with the pile body, and environmental protection and economy." The unique advantages of fluidized solidified soil are ignored—it has good fluidity (it can self-fill narrow gaps), self-compacting properties (no need for vibration equipment), early strength (final setting ≤12h, which can quickly enter subsequent processes), and environmental protection (it can utilize borehole slag, construction waste, and other waste materials on-site), which can perfectly solve the pain points of traditional filling materials. On the other hand, even if some solutions mention "solidified soil," they do not specify the material selection criteria (such as misuse of expansive soil or contaminated soil, which will lead to poor durability, and excessively large soil particle size will affect pumping). The advantages of fluidized solidified soil, such as "turning waste soil into treasure" and "stable performance," are not brought into play, resulting in low filling quality and low environmental benefits.

[0005] Traditional irregular piles are mostly friction piles. Generally, the side friction resistance of the pile is improved by increasing the contact area between the pile and the soil. However, the bearing capacity of small-diameter irregular piles is relatively weak, resulting in a limited improvement in the vertical bearing capacity of irregular single piles.

[0006] Therefore, it is urgent to scientifically combine "non-displacement prestressed X-shaped piles with enlarged heads" with "fluidized solidified soil filling" to both retain the environmental protection function of non-displacement technology and solve the gap filling problem through the characteristics of fluidized solidified soil, while simultaneously improving the vertical bearing capacity of prestressed X-shaped piles and utilizing construction waste resources. Summary of the Invention

[0007] The purpose of this invention is to provide a non-displacement prestressed X-shaped pile with an enlarged head. The pile body of the X-shaped pile includes at least one pile section. Each pile section includes a core area located at the center and four flanges spaced apart around the core area. Adjacent flanges are connected by an inner arc surface, so that the cross-section of the X-shaped pile is X-shaped as a whole.

[0008] The X-shaped pile is a drilled pile, and the space between the outer wall of the X-shaped pile and the wall of the pile hole is filled with fluidized solidified soil.

[0009] The bottom of the X-shaped pile is fitted with a prefabricated enlarged head. The prefabricated enlarged head has two assembly methods. Based on the assembly method, the prefabricated enlarged head includes prefabricated enlarged head I and prefabricated enlarged head II.

[0010] Assembly method 1: First, insert the prefabricated enlarged head I into the pile hole, then insert the X-shaped pile, and connect the X-shaped pile and the prefabricated enlarged head in the pile hole.

[0011] Assembly Method 2: Outside the pile hole, assemble the X-shaped pile with the prefabricated enlarged head II, and then simultaneously insert it into the pile hole.

[0012] Furthermore, the major axis width of the pile body cross-section For the wing width 5-10 times that of the inner arc surface. The central angle corresponding to the inner arc surface... The range is 90°-150°.

[0013] Furthermore, the prefabricated enlarged head I / prefabricated enlarged head II is a stepped rotating structure, including a cylindrical structure at the bottom and a frustum-shaped structure at the top. The diameter of the lower base of the frustum-shaped structure is equal to the diameter of the cylindrical structure.

[0014] The center of each prefabricated enlarged head I / prefabricated enlarged head II is provided with an X-shaped mounting groove. The X-shaped mounting groove penetrates the frustum-shaped structure and extends into the cylindrical structure, and the shape of the X-shaped mounting groove is adapted to the cross-sectional shape of the X-shaped pile.

[0015] The truncated cone-shaped structure has several vertical water inlet holes I and II that penetrate the prefabricated enlarged head, spaced apart around the X-shaped mounting groove on its inclined surface and top surface.

[0016] The prefabricated enlarged head II has a pair of pin holes on its sidewall corresponding to the flange of the X-shaped pile. The two ends of each pin hole connect to the outside and the X-shaped mounting groove. The diameter of the pin hole is smaller than the diameter of the vertical water inlet I. The pin holes are threaded. Blind holes are provided on the bottom sidewall of the pile section connected to the prefabricated enlarged head II. The number and position of the blind holes correspond one-to-one with the number and position of the pin holes.

[0017] When the pile section is connected to the prefabricated enlarged head II, the bottom of the pile section is embedded in the X-shaped mounting groove of the prefabricated enlarged head II, and the pin passes through the pin hole and the blind hole to fix the prefabricated enlarged head II on the pile section.

[0018] Furthermore, the diameter of the cylindrical structure of the prefabricated enlarged head I / prefabricated enlarged head II is 1.5-2 times the diameter of the circumscribed circle of the X-shaped pile. The prefabricated enlarged head I / prefabricated enlarged head II is prefabricated using C30-C40 reinforced concrete and has an internal annular steel mesh. The pin is made of Q235 steel.

[0019] Furthermore, the X-shaped pile is precast using C60-C80 prestressed concrete, with longitudinal bars and stirrups pre-embedded inside. The longitudinal bars are made of HRB400E threaded steel, and the stirrups are made of HRB400 spiral stirrups. The effective prestressing ratio is 10%-15%.

[0020] Furthermore, the fluidized solidified soil includes on-site soil material, solidifying agent, water, and additives.

[0021] The on-site soil material refers to the soil material generated during the on-site rotary drilling process. When the on-site soil material is insufficient, plain fill, cohesive soil, silt, sand, or a mixture of the four types of soil shall be used.

[0022] The maximum particle size of the soil particles in the soil is ≤5cm, and the organic matter content in the soil is ≤5%.

[0023] The curing agent includes ,active and The mass ratio is within the range of: Accounting for 40%-60%, active It accounts for 15%-30%. It accounts for 20%-40%.

[0024] The additives include one or more of crystallization inducers, dispersants, surfactants, and micro-expansion agents.

[0025] The mass distribution of each component of the fluidized solidified soil is as follows: when there are 100 parts of soil material on site, the solidifying agent is 6-10 parts and the water is 10-15 parts.

[0026] The slump of the fluidized solidified soil is 180-220 mm, and the permeability coefficient is 1× cm / s-5× cm / s, 7-day unconfined compressive strength is 0.5MPa-5MPa.

[0027] Another objective of this invention is to provide a construction method based on non-displacement prestressed X-shaped piles with enlarged heads. The construction method of assembly method one includes the following steps:

[0028] S1.1. Based on the designed borehole diameter and designed pile bottom elevation, use a rotary drilling rig to rotary drill the pile hole; and clean the sediment at the bottom of the hole after drilling is completed;

[0029] If the drilling area is a soft soil area, mud slurry should be used for wall protection during drilling;

[0030] S1.2. Lower the prefabricated enlarged head I to the bottom of the hole using hoisting equipment;

[0031] S1.3 Install a special external pile clamp at the pile hole opening, and determine whether pile splicing is needed based on the pile hole height and pile section height. If so, proceed to step S1.4; otherwise, jump to step S1.5.

[0032] S1.4. Based on the pile hole height and pile section height, determine the required number of pile sections N; lower the first pile section. When the pile section is lowered to the pile hole opening, use a special pile clamp outside the hole to position the pile section, and then connect the second pile section to the first pile section.

[0033] Following the aforementioned method, N pile sections are connected sequentially to form an X-shaped pile;

[0034] S1.5. Use hoisting equipment to hoist the X-shaped pile, so that the X-shaped pile passes through the special pile clamp outside the hole and extends into the bottom of the pile hole, where it fits into the X-shaped installation groove of the prefabricated enlarged head I.

[0035] S1.6. A grouting pipe is laid between the X-shaped pile and the pile hole wall. Fluidized solidified soil is pumped into the grouting pipe using a pumping device until the fluidized solidified soil backfills to the hole opening. During the pumping process, the grouting pipe is lifted.

[0036] S1.7 After the backfilling of the fluidized solidified soil is completed, cover it with geotextile and keep it moist for 7-14 days. After the curing is completed, use the on-site core sampling method to test the unconfined compressive strength of the fluidized solidified soil, and at the same time test the vertical bearing capacity of the pile.

[0037] The construction method for assembly method two includes the following steps:

[0038] S2.1. Based on the designed borehole diameter and designed pile bottom elevation, use a rotary drilling rig to rotary drill the pile hole; and clean the sediment at the bottom of the hole after drilling is completed;

[0039] If the drilling area is a soft soil area, mud slurry should be used for wall protection during drilling;

[0040] S2.2. Outside the hole, insert the pile section into the X-shaped mounting groove of the prefabricated enlarged head II, and then pass the pin through the pin hole on the prefabricated enlarged head II and the blind hole on the pile section to complete the connection between the X-shaped pile and the prefabricated enlarged head II; after the connection is completed, use a tension gauge to test it;

[0041] S2.3 Install a special external pile clamp at the pile hole opening, and determine whether pile splicing is needed based on the pile hole height and pile section height. If so, proceed to step S2.4; otherwise, skip to step S2.5.

[0042] S2.4. Based on the pile hole height and pile section height, determine the required number of pile sections N; lower the first pile section. When the pile section is lowered to the pile hole opening, use a special pile clamp outside the hole to position the pile section, and then connect the second pile section to the first pile section.

[0043] Following the aforementioned method, N pile sections are connected sequentially to form an X-shaped pile;

[0044] S2.5. The X-shaped pile is hoisted using hoisting equipment, so that the X-shaped pile passes through the special pile clamp outside the hole and extends to the bottom of the pile hole;

[0045] S2.6. A grouting pipe is laid between the X-shaped pile and the pile hole wall. Fluidized solidified soil is pumped into the grouting pipe using a pumping device until the fluidized solidified soil backfills to the hole opening. During the pumping process, the grouting pipe is lifted.

[0046] S2.7 After the backfilling of the fluidized solidified soil is completed, cover it with geotextile and keep it moist for 7-14 days. After the curing is completed, use the on-site core sampling method to test the unconfined compressive strength of the fluidized solidified soil, and at the same time test the vertical bearing capacity of the pile.

[0047] Furthermore, in steps S1.3) and S2.3), the special external clamping device includes an outer ring frame, a flange clamping unit, an inner concave arc clamping unit, and several support legs.

[0048] Several of the aforementioned support legs are installed at intervals on the outer ring frame and can be telescopically anchored into the soil for fixation.

[0049] Four flange clamping units and four concave arc clamping units are circumferentially mounted on the outer ring frame. The flange clamping units and the concave arc clamping units are spaced apart.

[0050] The flange clamping unit and the concave arc clamping unit are used to clamp the flange of the X-shaped pile and the inner arc surface of the connecting flange, respectively.

[0051] The flange clamping unit / concave arc clamping unit is a two-stage hydraulic clamping device, including oil inlet / outlet I, oil inlet / outlet II, bottom cover, first-stage clamping device cylinder, second-stage clamping cylinder, piston, oil inlet valve, and oil delivery pipeline.

[0052] The cylinder of the first-stage clamping device is a hollow cylindrical structure with one open end and the other closed. The closed end face of the cylinder has a through hole I, and the open end is connected to the bottom cover of the hydraulic device to form a first-stage piston cavity.

[0053] A secondary clamping cylinder is slidably disposed within the primary piston cavity. The secondary clamping cylinder comprises a large cylindrical section and a small cylindrical section coaxially connected. The large cylindrical section of the secondary clamping cylinder is located within the primary piston cavity, and the end of the small cylindrical section furthest from the large cylindrical section extends out of the primary piston cavity through a through-hole I. The large cylindrical section divides the primary piston cavity into primary piston cavity I and primary piston cavity II. Primary piston cavity I is formed by a bottom cover, a primary clamping device cylinder, and the end face of the large cylindrical section of the secondary clamping cylinder. Primary piston cavity II is formed by a primary clamping device cylinder, a small cylindrical section of the secondary clamping cylinder, and the transition surface between the large and small cylindrical sections of the secondary clamping cylinder.

[0054] The end face of the small cylindrical section of the secondary clamping cylinder, away from the large cylindrical section, is provided with a through hole II. The through hole II communicates with the secondary piston cavity inside the secondary clamping cylinder.

[0055] A piston is slidably connected in the secondary piston cavity of the secondary clamping cylinder. One end of the piston extends out of the through hole II. The piston divides the secondary piston cavity into secondary piston cavity I and secondary piston cavity II. Secondary piston cavity I is located near the bottom cover. An oil inlet valve is provided at the center of the large cylindrical section of the secondary clamping cylinder.

[0056] The hydraulic device has an oil inlet / outlet I on its bottom cover. The oil inlet / outlet I communicates with the first-stage piston cavity I. An oil supply pipe is provided on the side wall of the small cylindrical section of the second-stage clamping cylinder. The two ends of the oil supply pipe communicate with the first-stage piston cavity II and the second-stage piston cavity I, respectively. The first-stage clamping device cylinder has an oil inlet / outlet II on its side wall. The oil inlet / outlet II communicates with the second-stage piston cavity I.

[0057] The piston is provided with a gasket at the end extending out of the secondary clamping cylinder, and the gaskets on the flange clamping unit and the concave arc clamping unit are respectively adapted to the flange and the inner arc surface.

[0058] Furthermore, in steps S1.6) and S2.6), the process of preparing the fluidized solidified soil includes the following steps:

[0059] S6.1 Collect the soil generated during rotary drilling in step S1.1) or step S2.1;

[0060] S6.2. Expansive soil, contaminated soil and saline soil in the soil material are removed by visual observation and laboratory geotechnical test, and the remaining soil material is put into a vibrating screen for crushing and screening to remove particles and impurities with a particle size >5cm.

[0061] S6.3. The organic matter content of the sieved soil is tested by burning. It is determined whether the organic matter content of the sieved soil is less than or equal to 5%. If so, proceed to step S6.4; otherwise, return to step S6.1.

[0062] S6.4, will ,active and Mix according to the preset ratio to make a curing agent;

[0063] S6.5 Select water sources that meet the requirements for concrete water in GB / T14684-2022 "Construction Sand" as mixing water; if groundwater or surface water is used, the chloride ion content, sulfate content and pH value in the water need to be tested to see if they meet the requirements.

[0064] S6.6. Add the soil material from step S6.3) and the curing agent from step S6.4) into the mixer in proportion and perform preliminary mixing; then add the mixing water from step S6.5) into the mixer in proportion, wet mix for Tmin, then stop mixing to complete the production of fluidized solidified soil.

[0065] Furthermore, during the curing process in steps S1.7) and S2.7), watering is used to keep the soil moist, with watering ≥3 times a day. When the ambient temperature is below 5℃, covering and heat preservation measures are taken. For the unconfined compressive strength test of the fluidized solidified soil, at least 3 core samples need to be selected, and the average value of the test results is taken as the final strength value.

[0066] The technical effects of this invention are undeniable, and its beneficial effects are as follows:

[0067] 1. Completely eliminate soil squeezing effect: The process of drilling holes by rotary drilling and then inserting precast piles completely avoids the soil squeezing problem caused by hammering or static pressure, greatly reducing the adverse impact on the surrounding environment, buildings and underground pipelines, and is especially suitable for construction in sensitive urban areas.

[0068] 2. Significantly improved bearing capacity: Combining the dual advantages of high side friction resistance and high bearing capacity at the enlarged head of the X-shaped pile, it effectively improves the vertical bearing capacity of a single pile and optimizes the stress performance of the pile foundation.

[0069] 3. High ease of construction and reliability: The innovative prefabricated enlarged head design (with water inlet and pin connection mechanism) solves the installation difficulties caused by buoyancy at the bottom of the hole and the challenges of in-hole connection operations. The dedicated external pile clamp, designed specifically for the cross-sectional characteristics of X-shaped piles, provides stable and reliable clamping and precise positioning, effectively ensuring the verticality of the pile splicing and lowering process.

[0070] 4. Green, environmentally friendly, and economical: The core filling material—fluidized solidified soil—can consume a large amount of waste soil generated during rotary drilling, realizing "waste soil resource utilization" and reducing transportation costs and environmental burden. Fluidized solidified soil has excellent engineering characteristics such as self-compacting, vibration-free operation, controllable strength development, and good impermeability, ensuring filling quality while reducing construction energy consumption and complexity. Attached Figure Description

[0071] Figure 1 This is a schematic diagram of a prestressed X-shaped pile, in which... Figure 1 (a) is the front view. Figure 1 (b) Side view, Figure 1 (c) is a top view;

[0072] Figure 2 This is a schematic diagram of the prefabricated enlarged head I, in which... Figure 2 (a) is a top view. Figure 2 (b) is Figure 2 (a) Sectional view of section AA, Figure 2 (c) is the front view. Figure 2 (d) Side view;

[0073] Figure 3 This is a schematic diagram of the prefabricated enlarged head II, in which... Figure 3 (a) is a top view. Figure 3 (b) is Figure 3 (a) Sectional view of BB section, Figure 3 (c) is the front view. Figure 3 (d) Side view;

[0074] Figure 4 This is a schematic diagram of a special-purpose pile driver for external borehole applications. Figure 4 (a) is a top view. Figure 4 (b) is Figure 4 (a) Sectional view of section C, Figure 4 (c) is the front view. Figure 4 (d) is a side view;

[0075] Figure 5 This is a schematic diagram of a two-stage hydraulic clamping device, in which... Figure 5 (a) is a schematic diagram of piston retraction. Figure 5 (b) is a schematic diagram of the piston extending;

[0076] Figure 6 Construction process for prestressed X-shaped piles and fluidized solidified soil filling;

[0077] In the diagram: 1-Pile body; 41-Precast enlarged head I; 42-Precast enlarged head II; 401-X-shaped mounting groove; 5-External pile clamp; 6-Rotary drilling machine; 7-Flange; 8-Core area; 9-Central angle; 12-Vertical water inlet hole I; 13-Vertical water inlet hole II; 14-Pin hole; 15-Outer ring; 16-Flange clamping unit; 17-Concave arc clamping unit; 18-Inlet / outlet port I; 19-Inlet / outlet port II ; 20- Bottom cover; 21- Primary clamping device cylinder body; 22- Secondary clamping cylinder body; 24- Piston; 25- Oil inlet valve; 26- Primary piston cavity I; 27- Primary piston cavity II; 28- Oil pipeline; 29- Secondary piston cavity I; 30- Secondary piston cavity II; 31- Rotary drilling bit; 32- Soil transport pipeline; 33- Hydraulic support system; 34- Lifting pulley; 35- Cab; 36- Tracked walking system. Detailed Implementation

[0078] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0079] Example 1:

[0080] A non-displacement prestressed X-shaped pile with an enlarged head, wherein the pile body 1 of the X-shaped pile includes at least one pile segment, each pile segment including a core region 8 located at the center and four flanges 7 spaced apart around the core region 8, and adjacent flanges 7 are connected by an inner arc surface to make the cross section of the X-shaped pile as an whole X-shape.

[0081] The X-shaped pile is a drilled pile, and the space between the outer wall of the X-shaped pile and the wall of the pile hole is filled with fluidized solidified soil.

[0082] The bottom of the X-shaped pile body 1 is equipped with a prefabricated enlarged head. The prefabricated enlarged head has two assembly methods. Based on the assembly method, the prefabricated enlarged head includes prefabricated enlarged head I41 and prefabricated enlarged head II42.

[0083] Assembly method 1: First, insert the prefabricated enlarged head I41 into the pile hole, then insert the X-shaped pile. The X-shaped pile and the prefabricated enlarged head 4 are connected in the pile hole.

[0084] Assembly Method 2: Outside the pile hole, assemble the X-shaped pile with the prefabricated enlarged head II42, and then simultaneously insert it into the pile hole.

[0085] Example 2:

[0086] The main structure of this embodiment is the same as that of Embodiment 1. Further, the major axis width of the pile body 1 section is... For the wing width 5-10 times that of the inner arc surface. The central angle corresponding to the inner arc surface... The range of 9 is 90°-150°.

[0087] Example 3:

[0088] The main structure of this embodiment is the same as any one of embodiments 1-2. Furthermore, the prefabricated enlarged head I41 / prefabricated enlarged head II42 is a stepped rotating structure, including a cylindrical structure at the bottom and a frustum-shaped structure at the top. The diameter of the lower base of the frustum-shaped structure is equal to the diameter of the cylindrical structure.

[0089] The center of the prefabricated enlarged head I41 / prefabricated enlarged head II42 is provided with an X-shaped mounting groove 401. The X-shaped mounting groove 401 penetrates the frustum-shaped structure and extends into the cylindrical structure, and the shape of the X-shaped mounting groove 401 is adapted to the cross-sectional shape of the X-shaped pile.

[0090] The inclined surface and top surface of the frustum-shaped structure are respectively provided with several vertical water inlet holes I12 and II13 that penetrate the prefabricated enlarged head 4 around the X-shaped mounting groove 401.

[0091] The prefabricated enlarged head II42 X-shaped mounting groove 401 has a pair of pin holes 14 at positions corresponding to the flange of the X-shaped pile. The two ends of each pin hole 14 are connected to the outside and to the X-shaped mounting groove 401, respectively. The diameter of each pin hole 14 is smaller than the diameter of the vertical water inlet I12. Each pin hole 14 is threaded.

[0092] Blind holes are provided on the bottom sidewall of the pile section connected to the prefabricated enlarged head II42. The number and position of the blind holes correspond one-to-one with the number and position of the pin holes 14.

[0093] When the pile section is connected to the prefabricated enlarged head II42, the bottom of the pile section is embedded in the X-shaped mounting groove 401 of the prefabricated enlarged head II42, and the pin passes through the pin hole 14 and the blind hole to fix the prefabricated enlarged head II42 on the pile section.

[0094] Example 4:

[0095] The main structure of this embodiment is the same as any one of embodiments 1 to 3. Furthermore, the diameter of the cylindrical structure of the prefabricated enlarged head I41 / prefabricated enlarged head II42 is 1.5-2 times the diameter of the outer circle of the X-shaped pile. The prefabricated enlarged head I41 / prefabricated enlarged head II42 is prefabricated using C30-C40 reinforced concrete and has an internal annular steel mesh.

[0096] The pin is made of Q235 steel.

[0097] Example 5:

[0098] The main structure of this embodiment is the same as any one of embodiments 1 to 4. Furthermore, the X-shaped pile is precast with C60-C80 prestressed concrete, and longitudinal bars and stirrups are pre-embedded in the pile. The longitudinal bars are HRB400E threaded steel bars, and the stirrups are HRB400 spiral stirrups. The effective prestress application ratio is 10%-15%.

[0099] Example 6:

[0100] The main structure of this embodiment is the same as any one of embodiments 1 to 5. Furthermore, the fluidized solidified soil includes on-site soil material, solidifying agent, water and additives.

[0101] The on-site soil material refers to the soil material generated during the on-site rotary drilling process. When the on-site soil material is insufficient, plain fill, cohesive soil, silt, sand, or a mixture of the four types of soil shall be used.

[0102] The maximum particle size of the soil particles in the soil is ≤5cm, and the organic matter content in the soil is ≤5%.

[0103] The curing agent includes ,active and The mass ratio is within the range of: Accounting for 40%-60%, active It accounts for 15%-30%. It accounts for 20%-40%.

[0104] The additives include one or more of crystallization inducers, dispersants, surfactants, and micro-expansion agents.

[0105] The mass distribution of each component of the fluidized solidified soil is as follows: when there are 100 parts of soil material on site, the solidifying agent is 6-10 parts and the water is 10-15 parts.

[0106] The slump of the fluidized solidified soil is 180-220 mm, and the permeability coefficient is 1× cm / s-5× cm / s, 7-day unconfined compressive strength is 0.5MPa-5MPa.

[0107] Example 7:

[0108] A construction method for non-displacement prestressed X-shaped piles with enlarged heads as described in any one of Examples 1 to 6, wherein the construction method of assembly method one includes the following steps:

[0109] S1.1 Based on the designed borehole diameter and designed pile bottom elevation, use a rotary drilling rig to rotary drill the pile hole. The designed pile diameter is 50-100mm larger than the bottom diameter of the prefabricated enlarged head.

[0110] After drilling is completed, clean the sediment at the bottom of the hole to ensure that the sediment thickness is ≤50mm;

[0111] In areas with good geological conditions, mud wall protection is not required. In soft soil areas, mud wall protection is used in the borehole, and the mud specific gravity is controlled at 1.1-1.2.

[0112] S1.2. Lower the prefabricated enlarged head I41 to the bottom of the hole using hoisting equipment; ensure that the axis of the prefabricated enlarged head coincides with the axis of the hole using a temporary guide frame at the hole opening, and slowly lower it to the bottom of the hole;

[0113] S1.3 Install a special external pile clamp 5 at the pile hole opening, and determine whether pile splicing is required based on the pile hole height and pile section height. If it is required, proceed to step S1.4; otherwise, jump to step S1.5.

[0114] S1.4. Based on the pile hole height and pile section height, determine the required number of pile sections N; lower the first pile section. When the pile section reaches the pile hole opening, use a special external pile clamp 5 to position the pile section, and then connect the second pile section to the first pile section; the connection method is welding or flange connection. After the pile is connected, check the verticality of the pile body to ensure that the verticality deviation is ≤0.5%;

[0115] Following the aforementioned method, N pile sections are connected sequentially to form an X-shaped pile;

[0116] S1.5. Use hoisting equipment to hoist the X-shaped pile, so that the X-shaped pile passes through the special pile clamp 5 outside the hole and extends into the bottom of the pile hole, where it fits into the X-shaped mounting groove 401 of the prefabricated enlarged head I41.

[0117] S1.6. A grouting pipe is installed between the X-shaped pile and the pile hole wall. Fluidized solidified soil is pumped into the grouting pipe using a pumping device until the fluidized solidified soil is backfilled to the hole opening. During the pumping process, the grouting pipe is raised. The fluidity of the fluidized solidified soil is checked every 30 minutes during the backfilling process.

[0118] S1.7 After the backfilling of the fluidized solidified soil is completed, cover it with geotextile and keep it moist for 7-14 days. After the curing is completed, use the on-site core sampling method to test the unconfined compressive strength of the fluidized solidified soil, and at the same time test the vertical bearing capacity of the pile.

[0119] The construction method for assembly method two includes the following steps:

[0120] S2.1 Based on the designed borehole diameter and designed pile bottom elevation, use a rotary drilling rig to rotary drill the pile hole. The designed pile diameter is 50-100mm larger than the bottom diameter of the prefabricated enlarged head.

[0121] After drilling is completed, clean the sediment at the bottom of the hole to ensure that the sediment thickness is ≤50mm;

[0122] In areas with good geological conditions, mud wall protection is not required. In soft soil areas, mud wall protection is used in the borehole, and the mud specific gravity is controlled at 1.1-1.2.

[0123] S2.2. Outside the hole, insert the pile section into the X-shaped mounting groove 401 of the prefabricated enlarged head II42, and then pass the pin through the pin hole 14 on the prefabricated enlarged head II42 and the blind hole on the pile section to complete the connection between the X-shaped pile and the prefabricated enlarged head II42; after the connection is completed, use a tension gauge to test and ensure that the connection force is ≥50kN;

[0124] S2.3 Install a special external pile clamp 5 at the pile hole opening, and determine whether pile splicing is required based on the pile hole height and pile section height. If it is required, proceed to step S2.4; otherwise, jump to step S2.5.

[0125] S2.4. Based on the pile hole height and pile section height, determine the required number of pile sections N; lower the first pile section. When the pile section reaches the pile hole opening, use a special external pile clamp 5 to position the pile section, and then connect the second pile section to the first pile section; the connection method is welding or flange connection. After the pile is connected, check the verticality of the pile body to ensure that the verticality deviation is ≤0.5%;

[0126] Following the aforementioned method, N pile sections are connected sequentially to form an X-shaped pile;

[0127] S2.5. The X-shaped pile is hoisted using hoisting equipment, so that the X-shaped pile passes through the special pile clamp (5) outside the hole and extends to the bottom of the pile hole; the lowering speed is controlled at 0.3-0.8m / min, and the verticality of the pile is adjusted in real time through the positioning adjustment mechanism during the lowering process to ensure that the verticality deviation is ≤0.5%;

[0128] S2.6. A grouting pipe is laid between the X-shaped pile and the pile hole wall. Fluidized solidified soil is pumped into the grouting pipe using a pumping device until the fluidized solidified soil is backfilled to the hole opening. During the pumping process, the grouting pipe is raised. The fluidity of the fluidized solidified soil is checked every 30 minutes during the backfilling process.

[0129] S2.7 After the backfilling of the fluidized solidified soil is completed, cover it with geotextile and keep it moist for 7-14 days. After the curing is completed, use the on-site core sampling method to test the unconfined compressive strength of the fluidized solidified soil, and at the same time test the vertical bearing capacity of the pile.

[0130] Example 8:

[0131] The main structure of this embodiment is the same as that of embodiment 7. Further, in steps S1.1) and S2.1), the rotary drilling rig model needs to be selected according to the nature of the bottom layer and the diameter of the prestressed X-shaped pile. When the pile diameter is less than 1000mm, the XR220-XR280 rotary drilling rig is selected, and when the pile diameter is greater than 1000mm, the XR360-XR460 rotary drilling rig is selected.

[0132] Example 9:

[0133] The main structure of this embodiment is the same as any one of embodiments 7 to 8. Further, in steps S1.3) and S2.3), the special external clamping device 5 includes an outer ring frame 15, a flange clamping unit 16, an inner concave arc clamping unit 17, and several support legs.

[0134] Several support legs are installed at intervals on the outer ring frame 15 and can be telescopically anchored into the soil for fixation. Four flange clamping units 16 and four concave arc clamping units 17 are installed circumferentially on the outer ring frame 15. The flange clamping units 16 and concave arc clamping units 17 are spaced apart.

[0135] The flange clamping unit 16 and the concave arc clamping unit 17 are used to clamp the flange 7 of the X-shaped pile and the inner arc surface connecting the flange 7, respectively.

[0136] The flange clamping unit 16 / concave arc clamping unit 17 is a two-stage hydraulic clamping device, including an oil inlet / outlet I18, an oil inlet / outlet II19, a bottom cover 20, a first-stage clamping device cylinder 21, a second-stage clamping cylinder 22, a piston 24, an oil inlet valve 25, and an oil delivery pipe 28.

[0137] The cylinder body 21 of the first-stage clamping device is a cylindrical structure that is hollow inside, open at one end and closed at the other end. The closed end face of the cylinder body is provided with a through hole I, and the open end is connected to the bottom cover 20 of the hydraulic device to form a first-stage piston cavity.

[0138] A secondary clamping cylinder 22 is slidably disposed within the primary piston cavity. The secondary clamping cylinder 22 comprises a large cylindrical section and a small cylindrical section coaxially connected. The large cylindrical section of the secondary clamping cylinder 22 is located within the primary piston cavity, and the end of the small cylindrical section away from the large cylindrical section extends out of the primary piston cavity through a through hole I. The large cylindrical section divides the primary piston cavity into a primary piston cavity I26 and a primary piston cavity II27. The primary piston cavity I26 is formed by the bottom cover 20, the primary clamping device cylinder 21, and the end face of the large cylindrical section of the secondary clamping cylinder 22. The primary piston cavity II27 is formed by the primary clamping device cylinder 21, the small cylindrical section of the secondary clamping cylinder 22, and the transition surface between the large and small cylindrical sections of the secondary clamping cylinder 22.

[0139] The end face of the small cylindrical section of the secondary clamping cylinder 22, away from the large cylindrical section, is provided with a through hole II. The through hole II communicates with the secondary piston cavity inside the secondary clamping cylinder 22.

[0140] A piston 24 is slidably connected in the secondary piston cavity of the secondary clamping cylinder 22. One end of the piston 24 extends out of the through hole II. The piston 24 divides the secondary piston cavity into a secondary piston cavity I29 and a secondary piston cavity II30. The secondary piston cavity I29 is located near the bottom cover 20. An oil inlet valve 25 is provided at the center of the large cylindrical section of the secondary clamping cylinder 22.

[0141] The hydraulic device's bottom cover 20 is provided with an oil inlet / outlet port I18. The oil inlet / outlet port I18 communicates with the first-stage piston cavity I26. An oil supply pipe 28 is provided on the side wall of the small cylindrical section of the second-stage clamping cylinder 22. The two ends of the oil supply pipe 28 communicate with the first-stage piston cavity II27 and the second-stage piston cavity I29, respectively. The first-stage clamping device cylinder 21 is provided with an oil inlet / outlet port II19 on its side wall. The oil inlet / outlet port II19 communicates with the second-stage piston cavity I29.

[0142] The piston 24 is provided with a gasket at the end extending out of the secondary clamping cylinder 22, and the gaskets on the flange clamping unit 16 and the concave arc clamping unit 17 are respectively adapted to the flange 7 and the inner arc surface.

[0143] Example 10:

[0144] The main structure of this embodiment is the same as any one of embodiments 7 to 9. Further, in steps S1.6) and S2.6), the process of producing the fluidized solidified soil includes the following steps:

[0145] S6.1 Collect the soil generated during rotary drilling in step S1.1) or step S2.1;

[0146] S6.2. Expansive soil, contaminated soil and saline soil in the soil are removed by visual observation and laboratory geotechnical test. The remaining soil is put into a vibrating screen for crushing and screening to remove particles and impurities with a diameter >5cm (such as gravel, grass roots, hard lumps of construction waste, etc.).

[0147] S6.3. The organic matter content of the sieved soil is tested by burning. It is determined whether the organic matter content of the sieved soil is less than or equal to 5%. If so, proceed to step S6.4; otherwise, return to step S6.1.

[0148] S6.4, will ,active and Add the ingredients to a vertical dry powder mixer according to the preset ratio and dry mix for 1-1.5 minutes until the mixture is uniform to form a curing agent;

[0149] S6.5. Select water sources that meet the requirements for concrete water in GB / T14684-2022 "Construction Sand" as mixing water;

[0150] If groundwater or surface water is used, the chloride ion content (≤1000mg / L), sulfate content (≤2000mg / L), and pH value (6.5-8.5) in the water must be tested to ensure that the water quality is non-corrosive;

[0151] S6.6. Add the soil material from step S6.3) and the curing agent from step S6.4) into a twin-shaft horizontal special mixer in proportion. First, dry mix for 1-2 minutes to allow the soil material and curing agent to be initially mixed. Then, slowly add the mixing water from step S6.5) into the mixer in proportion (if liquid additives are needed, they can be diluted in the mixing water in advance). After wet mixing for 2-3 minutes (the total mixing time should be controlled at 3-5 minutes. During the mixing process, check the state of the mixture through the observation window to ensure that there are no lumps and the color is uniform), stop mixing to complete the production of fluidized solidified soil.

[0152] Example 11:

[0153] The main structure of this embodiment is the same as any one of embodiments 7 to 10. Furthermore, during the curing process in steps S1.7) and S2.7), watering is used to keep the soil moist, with watering ≥ 3 times a day. When the ambient temperature is below 5℃, covering and heat preservation measures are taken. At least 3 core samples need to be selected for the unconfined compressive strength test of the fluidized solidified soil, and the average value of the test results is taken as the final strength value.

[0154] Example 12:

[0155] The main structure of this embodiment is the same as any one of embodiments 7 to 11. Further, in step S2.5), the state of the elastic pin needs to be checked before the connector is lowered to ensure that the pin can extend and retract flexibly without jamming. If the hole wall collapses slightly during the lowering process, the lowering should be stopped and the hole wall should be reinforced by high-pressure grouting. The lowering should continue after the hole wall is stable.

[0156] Example 13:

[0157] The main structure of this embodiment is the same as any one of embodiments 1 to 12. Furthermore, the present invention aims to solve multiple technical pain points existing in current pile foundation construction and structural design, as detailed below:

[0158] 1. Soil squeezing effect and interference with the surrounding environment: When traditional precast piles (such as PHC pipe piles) are driven by hammer or static pressure, they are prone to squeezing the surrounding soil, causing heave and displacement, resulting in cracking of existing buildings and deformation of underground pipelines. They are not suitable for sensitive scenarios such as dense urban building areas and complex underground pipelines. While existing bored piles do not have a soil squeezing effect, the filling materials for the gap between the pile body and the borehole wall (such as commercial concrete and ordinary soil) are either expensive and require vibration, or have poor density and large settlement in the later stage, making it difficult to balance environmental protection and performance.

[0159] 2. The enlarged head has a single function and is stuck when lowering. Most of the existing enlarged heads of the expanded piles are single solid structures. When there is mud or groundwater at the bottom of the hole, the sinking speed is slow due to buoyancy. In addition, the connection between the enlarged head and the X-shaped pile often requires working inside the hole, which results in a small operating space, low connection efficiency, and easy installation misalignment.

[0160] 3. The reliability of positioning and clamping of external piles: The existing X-shaped pile splicing lacks a dedicated positioning and clamping device and relies only on conventional hoisting guidance. Due to the irregular cross-section of the pile body (the coexistence of flange and concave arc surface), the clamping is not firm, and the verticality deviation after splicing exceeds the standard, which affects the overall stability of the pile foundation.

[0161] 4. Issues with the configuration and performance stability of fluidized solidified soil: Existing technologies for fluidized solidified soil suffer from non-standard soil material selection (easily contaminated with expansive or contaminated soil), ambiguous curing agent ratios, and coarse mixing processes. This results in poor fluidity (large fluctuations in slump), low strength (7-day compressive strength less than 0.5 MPa), and poor impermeability (permeability coefficient > 1× The speed (cm / s) is insufficient to meet the filling requirements of pile foundation gaps and does not make full use of the on-site soil generated by rotary drilling, resulting in resource waste and the burden of waste transportation.

[0162] II. Technical Solution

[0163] To address the problems of soil displacement interference, insufficient function of the enlarged head, unreliable pile splicing positioning, and unstable performance of fluidized solidified soil in existing pile foundation construction, this invention provides a non-displacement prestressed X-shaped pile with an enlarged head and a construction method for filling fluidized solidified soil. Through a combination of "pile structure optimization + construction technology innovation," it achieves a synergistic improvement in environmental friendliness, load-bearing capacity, and construction efficiency. The specific technical solution is as follows:

[0164] The pile system mainly includes prestressed X-shaped piles, prefabricated enlarged heads 2, special pile clamps outside the hole 5, rotary drilling machinery 6, and fluidized solidified soil.

[0165] The cross-section of the prestressed X-shaped pile consists of four identical flanges 7 and a central core portion 8. The opening angle of the X-shaped cross-section ranges from 90° to 150°. The major axis width of the X-shaped cross-section is generally 5 to 10 times the flange width.

[0166] Preferably, the flange width is 1 / 5 to 1 / 10 of the circumscribed circle diameter of the precast prestressed X-shaped pile. The pile is precast with C60-C80 prestressed concrete, the longitudinal reinforcement is HRB400E threaded steel, the stirrups are HRB400 spiral stirrups, and the effective prestress application ratio is 10%-15%.

[0167] The prefabricated enlarged head 2 has a frustum-shaped structure, with a centrally reserved X-shaped concave hole 10 and an outer ring 11 around it. The bottom diameter of the prefabricated enlarged head is approximately 1.5 to 2 times the diameter of the outer circle of the prefabricated prestressed X-shaped pile. It is made of C30-C40 reinforced concrete and has an internal ring-shaped steel mesh.

[0168] Furthermore, the prefabricated enlarged head can be designed as a prefabricated enlarged head 3 with a hole at the bottom, which has a vertical water inlet I12 and a vertical water inlet II13 inside. The channel passes through the outer ring of the enlarged head and / or the concave hole inside the enlarged head. This structure can provide an overflow channel for fluid when there is mud or groundwater at the bottom of the rotary drilling hole, effectively avoiding the problem of slow sinking of the enlarged head due to buoyancy.

[0169] Furthermore, the prefabricated enlarged head can be designed as a prefabricated enlarged head 4 with a pin, which adds a through transverse pin hole 14 to the prefabricated enlarged head 3 with a hole at the bottom. A retractable elastic pin is fitted inside the pin hole, preferably made of Q235 steel, with a guide bevel at its end. Positioning holes corresponding to the pin holes are opened on the side wall of the corresponding slot of the prefabricated prestressed X-shaped pile. By inserting the elastic pin into the positioning hole, a quick and reliable pre-connection between the prefabricated enlarged head and the prefabricated prestressed X-shaped pile outside the hole can be achieved, solving the problem of difficult installation inside the hole.

[0170] The external borehole clamping device 5 includes an outer ring frame 15, a flange clamping unit 16 mounted thereon, and an arc-shaped clamping unit 17 that matches the concave curvature of the X-shaped pile. This clamping device typically has 3-4 adjustable support legs, with a leg length generally between 1.0 and 1.5 meters, and can be equipped with retractable ground anchors. The ground anchors have a soil penetration depth of not less than 500 mm to ensure stability during borehole operation.

[0171] Preferably, the clamping unit is a two-stage hydraulic clamping device. This device includes an oil inlet / outlet I18, an oil inlet / outlet II19, a hydraulic device bottom cover 20, a primary clamping cylinder 21, a secondary clamping cylinder 22, a primary clamping piston 23, a secondary clamping piston 24, an oil inlet valve 25, cylinder protrusion structures 26-27, an oil supply pipe 28, a primary piston cavity 29, and a secondary piston cavity 30. For the special cross-section of the X-shaped pile, the clamping unit uses a flat shim at the contact point with the flange, and an arc-shaped shim matching the curvature at the contact point with the concave arc surface of the X-shaped pile, to achieve comprehensive and stable clamping.

[0172] The fluidized solidified soil is prepared by mixing soil, solidifying agent, water, and additives in a preset ratio. The key is that the soil used should preferably be excavated soil generated during rotary drilling, but unsuitable soil types such as expansive soil, contaminated soil, and saline soil must be excluded. The maximum particle size of the soil particles should be controlled to ≤5cm, and the organic matter content should be ≤5%.

[0173] The curing agent is... ,active and Inorganic hydraulic cementitious materials with cement as the main component can be cement-based and may contain at least one of fly ash or industrial slag powder.

[0174] The additives may include one or more of the following, as needed: crystallization inducers, dispersants, surfactants, and micro-expansion agents. The recommended mass ratio of the fluidized solidified soil is: excavated soil: solidifier: water = 100:(6-10):(10-15). Its performance indicators are: slump 180-220mm, permeability coefficient 1× cm / s-5× cm / s, and the 7-day unconfined compressive strength can reach 0.5MPa to 5MPa.

[0175] The rotary drilling machine 6 is a conventional piece of equipment, mainly including a rotary drill bit 31, a soil transport pipeline 32, a hydraulic support system 33, a hoisting pulley 34, a cab 35, and a tracked stepping system 36, etc.

[0176] This method mainly includes the following steps:

[0177] S1: Rotary drilling. A rotary drilling rig is used to drill a hole according to the designed pile diameter, which is 50-100mm larger than the bottom diameter of the prefabricated enlarged head. After drilling, the sediment at the bottom of the hole is cleaned to ensure its thickness is ≤50mm. Depending on the geological conditions, mud slurry wall protection is not required in stable soil layers; however, it is necessary in soft soil areas, with the mud specific gravity controlled at 1.1-1.2. A suitable rotary drilling rig model can be selected based on the pile diameter and geological conditions.

[0178] S2: Installation of the enlarged head and pile body (two methods).

[0179] Method A (lowering the enlarged head first): The precast enlarged head is vertically hoisted using hoisting equipment, and its alignment is ensured by a temporary guide frame at the borehole opening. It is then slowly lowered to the bottom of the borehole. Subsequently, a special external pile clamp is installed and secured at the borehole opening. The first precast prestressed X-shaped pile is hoisted, guided by the pile clamp, and inserted into the borehole, aligning its slot with the connecting seat of the enlarged head at the bottom of the borehole before pushing it in.

[0180] Method B (External Pre-connection): On the ground, the precast enlarged head is pre-connected to the first precast prestressed X-shaped pile section using a pin mechanism, and the reliability of the connection is checked (ensuring a connection force ≥ 50kN). Then, a special external pile clamp is installed and fixed at the borehole opening. The connector is lifted using hoisting equipment and slowly and controllably lowered to the bottom of the borehole with the help of the pile clamp. The lowering speed should be controlled at 0.3-0.8 m / min. During the process, the verticality of the pile is monitored and adjusted in real time (deviation ≤ 0.5%).

[0181] S3: Pile splicing. If the designed pile length exceeds the length of a single pile section, pile splicing is required. The second pile section is precisely positioned using a special external pile clamp, and the splicing is completed using welding or flange connection. The verticality of the pile must be checked again after splicing.

[0182] S4: Backfilling with fluidized solidified soil. Pre-mixed fluidized solidified soil is pumped into the annular gap between the precast prestressed X-shaped pile and the borehole wall. During grouting, the grouting pipe should be raised slowly and uniformly to avoid segregation of the fill material. Backfilling should be continuous until the borehole opening is filled. The fluidity of the fluidized solidified soil should be checked periodically during construction (e.g., every 30 minutes).

[0183] S5: Curing and Testing. After the fluidized solidified soil is backfilled, it should be covered with geotextile or similar materials for timely moisture retention and curing, which typically lasts 7-14 days. During the curing period, water should be sprayed at least three times a day to maintain moisture. In low-temperature environments, insulation measures should be taken. After curing, the unconfined compressive strength of the fluidized solidified soil should be tested using the core sampling method (at least three core samples should be taken and the average value calculated). At the same time, the vertical bearing capacity of the piles should also be tested.

[0184] Example 14:

[0185] The main structure of this embodiment is the same as any one of embodiments 1 to 13. Furthermore, in a certain transmission line project, the tower site is located on a slope with geological conditions of medium-dense sandy soil interbedded with cohesive soil. The design requires the foundation to adopt embedded pile foundation, which needs to provide high vertical bearing capacity and pull-out force. At the same time, the construction process should minimize the damage to the original terrain and the transportation of excavated soil, in line with the concept of green construction.

[0186] Main construction steps

[0187] S1: Rotary drilling. Based on the designed pile diameter, select a suitable rotary drilling rig for drilling. The borehole diameter should be slightly larger than the bottom diameter of the prefabricated enlarged head to allow space for the filling of the solidified soil along the pile side. During drilling, the use of mud slurry for wall protection will be determined based on the soil stability. After drilling to the design elevation, thoroughly clean the sediment at the bottom of the hole to ensure the sediment thickness meets the specifications.

[0188] S2: External pre-connection. On a leveled site, the "prefabricated enlarged head with pin" is pre-connected to the first section of the "prestressed X-shaped pile" using its pin connection mechanism. During connection, a crisp sound can be heard as the elastic pin snaps into the positioning hole, and the reliability of the connection is verified using a simple tensioning device to ensure a secure connection.

[0189] S3: The prestressed pile and enlarged head are lowered. At the rotary-dug borehole opening, a "dedicated external pile clamp" is installed and leveled, and its retractable support legs and ground anchor mechanism are used to firmly fix it to the ground. Subsequently, the pre-connected enlarged head and X-shaped pile are lifted as a whole using hoisting equipment, allowing it to accurately pass through the annular guide seat of the pile clamp. With the assistance of the hydraulic clamping unit of the pile clamp, the connecting body is slowly and smoothly lowered to the bottom of the borehole. During the lowering process, the verticality of the pile is monitored and adjusted in real time through the adjustment mechanism of the pile clamp to ensure that it remains within the allowable deviation range.

[0190] S4: Pile splicing. If the designed pile length exceeds the length of a single pile section, pile splicing is required. Under the stable support and precise guidance of a specialized pile clamp outside the borehole, the second and subsequent prestressed X-shaped pile sections are hoisted and connected. Pile splicing can be achieved using reliable methods such as welding or flange connections. After pile splicing is completed, the overall verticality of the pile body must be checked again.

[0191] S5: Preparation of fluidized solidified soil material. Qualified excavated soil generated during the rotary drilling process at the base site is preferentially used as the main material for fluidized solidified soil. After simple crushing and screening to remove oversized particles and impurities, the soil is mixed with solidifying agent, water, and necessary additives in a suitable proportion determined through pre-testing. A dedicated mixer is used to ensure the mixture is homogeneous and achieves the required flowability for self-leveling.

[0192] S6: Backfilling with fluidized solidified soil. Using pumping equipment, the mixed fluidized solidified soil is continuously injected into the annular gap between the prestressed X-shaped pile and the borehole wall. Grouting begins from the bottom of the hole and is slowly and uniformly raised as the liquid level rises to prevent segregation. The backfilling process continues until the fluidized solidified soil fills the entire gap and overflows from the borehole opening. The fluidity of the fluidized solidified soil is checked periodically during construction to ensure its workability.

[0193] S7: Curing and Post-Inspection. After the fluidized solidified soil is backfilled, measures such as covering the borehole openings are taken to maintain moisture and curing. The curing time is determined according to the ambient temperature and the solidified soil mix ratio to ensure normal strength development. After the curing period, the strength indicators of the fluidized solidified fill can be tested by methods such as core sampling on site, and the vertical compressive and tensile bearing capacity of the piles are tested according to the specifications.

[0194] Summary of the advantages of this embodiment

[0195] 1) Environmentally Friendly: Rotary drilling is a non-displacement process, minimizing disturbance to the surrounding soil and promoting slope stability; the fluidized solidified soil utilizes a large amount of excavated soil, reducing waste soil transportation and environmental damage. 2) High Bearing Capacity: X-shaped piles provide a large side surface area, combined with enlarged bottom heads, significantly improving the vertical bearing capacity and pull-out resistance of the foundation, making it ideal for the stress characteristics of transmission tower foundations. 3) Controllable Construction Quality: Specialized external pile clamps ensure precise positioning and verticality of the irregularly shaped piles; the self-compacting properties of the fluidized solidified soil guarantee the compaction of the pile side gaps, ensuring reliable overall construction quality. 4) Green and Environmentally Friendly: While ensuring project quality and safety, the resource utilization of waste materials is achieved, reducing material and environmental costs, resulting in significant comprehensive benefits.

[0196] Example 15:

[0197] The main structure of this embodiment is the same as any one of embodiments 1 to 14. Further, the engineering background and design requirements are as follows:

[0198] The underground utility tunnel project in the city center is located on a typical deep soft soil foundation, adjacent to municipal roads and existing underground pipelines. The design requires that the foundation construction strictly limit soil displacement and vibration to avoid adverse impacts on surrounding facilities and the environment, while also requiring the pile foundation to have good vertical bearing capacity and stability.

[0199] Main construction steps

[0200] S1: Rotary drilling and wall protection: A tracked rotary drilling rig is used to drill at the designed pile location. Because soft soil layers are prone to borehole shrinkage and collapse, high-quality, stable drilling mud is used throughout the drilling process for wall protection, and the mud specific gravity is controlled within a reasonable range to ensure borehole stability. The borehole diameter is determined based on the size of the prefabricated enlarged head, leaving sufficient space for filling with fluidized solidified soil. After drilling to the designed elevation, a borehole cleaning operation is performed to ensure that the thickness of sediment at the bottom of the borehole meets the specified limits.

[0201] S2: Lowering the prefabricated enlarged head. Given the potential presence of pressurized water or thick mud at the bottom of the borehole in soft soil, this example uses a prefabricated enlarged head with vertical water inlets at the bottom. It is slowly and vertically lowered into the borehole using a crane, with alignment ensured by a borehole guide device. During the lowering process, fluid at the bottom of the borehole is smoothly discharged through its internal water inlets, effectively overcoming buoyancy and achieving a stable and rapid descent to the bottom of the borehole.

[0202] S3: The pile body is connected to the bottom. A special external pile clamp is installed at the borehole opening and reliably fixed. The first prestressed X-shaped pile is lifted and, under the precise guidance and firm clamping of the pile clamp, vertically inserted into the hole, ensuring that its bottom slot accurately aligns with the pre-positioned enlarged head connector. A quick and reliable connection between the two at the bottom of the hole is achieved using a flexible pin mechanism.

[0203] S4: Pile splicing. Due to the long pile length, pile splicing is required. With the assistance of a specialized pile clamp outside the borehole, the subsequent X-shaped pile segments are hoisted and connected. A reliable connection method is used, and the overall verticality of the pile body is checked after each splicing to ensure it meets high standards.

[0204] S5: Preparation of fluidized solidified soil. The soft, water-rich soil produced by rotary excavation is initially drained and screened, and used as the main material for fluidized solidified soil. According to the appropriate proportion verified by experiments, it is mixed with special curing agent and cement at the mixing plant to produce fluidized solidified soil with high fluidity and appropriate initial setting time.

[0205] S6: Backfilling with fluidized solidified soil. Fluidized solidified soil is continuously pumped into the annular gap between the pile and the borehole using a high-pressure grouting pump and pipeline. The grouting pipe is embedded below the filling liquid surface and slowly raised while grouting, utilizing its self-leveling and self-compacting properties to fill the entire gap until grout overflows from the borehole opening. The fluidity of the fluidized solidified soil is monitored during construction to ensure a dense, void-free filling.

[0206] S7: Curing and Testing. After backfilling, the borehole openings are covered and kept moist for curing. The curing time is sufficient to ensure that the fluidized solidified soil reaches the performance strength required by the design. After curing, the strength of the fill material is verified using standard methods, and the bearing capacity of the engineering piles is tested.

[0207] Summary of the advantages of this embodiment

[0208] 1) Minimal Environmental Disturbance: The non-displacement rotary drilling and installation process completely avoids soil compression and vibration caused by traditional pile driving or pile pressing, effectively protecting adjacent municipal roads and underground pipelines, making it suitable for sensitive urban areas. 2) Overcoming Soft Soil Construction Challenges: The prefabricated enlarged head with water inlet solves the problem of soft soil holes being prone to floating and difficult to sink; specialized pile clamps ensure the accuracy and verticality of irregularly shaped pile installation in soft soil conditions. 3) Waste Utilization and Green Construction: High-moisture, difficult-to-dispose-of soft soil on-site is transformed into useful engineering materials (fluidized solidified soil), realizing the resource utilization of waste materials and reducing environmental impact and spoilage costs. 4) Reliable Foundation Performance: The combination of X-shaped piles and enlarged heads provides superior bearing capacity; the fluidized solidified soil filler integrates well with the pile body and soil, forming a composite foundation with good integrity, effectively controlling long-term settlement of soft soil foundations.

Claims

1. A non-displacement prestressed X-shaped pile with an enlarged head, characterized in that: The pile body (1) of the X-shaped pile includes at least one pile section. Each pile section includes a core area (8) located at the center and four flanges (7) spaced apart around the core area (8). The adjacent flanges (7) are connected by an inner arc surface, so that the cross section of the X-shaped pile is X-shaped as a whole. The X-shaped pile is a drilled pile, and the space between the outer wall of the X-shaped pile and the wall of the pile hole is filled with fluidized solidified soil; The bottom of the pile body (1) of the X-shaped pile is equipped with a prefabricated enlarged head; the prefabricated enlarged head has two assembly methods; based on the assembly method of the prefabricated enlarged head, the prefabricated enlarged head includes prefabricated enlarged head I (41) and prefabricated enlarged head II (42). Assembly method 1: First, insert the prefabricated enlarged head I (41) into the pile hole, and then insert the X-shaped pile. The X-shaped pile and the prefabricated enlarged head (4) are connected in the pile hole. Assembly method 2: Outside the pile hole, the X-shaped pile is assembled with the prefabricated enlarged head II (42) and then simultaneously implanted into the pile hole.

2. The non-displacement prestressed X-shaped pile with enlarged head according to claim 1, characterized in that: The major axis width of the pile body (1) section For the wing width 5-10 times; the central angle corresponding to the inner arc surface (9) ranges from 90° to 150°.

3. A non-displacement prestressed X-shaped pile with an enlarged head according to claim 1, characterized in that: The prefabricated enlarged head I (41) / prefabricated enlarged head II (42) is a stepped rotating body structure, including a cylindrical structure at the bottom and a frustum structure at the top; the diameter of the bottom surface of the frustum structure is equal to the diameter of the cylindrical structure. The center of the prefabricated enlarged head I (41) / prefabricated enlarged head II (42) is provided with the X-shaped mounting groove (401); the X-shaped mounting groove (401) penetrates the frustum-shaped structure and extends into the cylindrical structure, and the shape of the X-shaped mounting groove (401) is adapted to the cross-sectional shape of the X-shaped pile; The inclined surface and top surface of the frustum-shaped structure are respectively provided with a number of vertical water inlet holes I (12) and vertical water inlet holes II (13) that penetrate the prefabricated enlarged head (4) around the X-shaped mounting groove (401). The prefabricated enlarged head II (42) has a pair of pin holes (14) at the position corresponding to the X-shaped pile flange on the side wall of the X-shaped mounting groove (401). The two ends of the pin holes (14) are respectively connected to the outside and the X-shaped mounting groove (401). The diameter of the pin holes (14) is smaller than the diameter of the vertical water inlet I (12). The pin holes (14) are threaded. Blind holes are provided on the bottom sidewall of the pile section connected to the prefabricated enlarged head II (42); the number and position of the blind holes correspond one-to-one with the number and position of the pin holes (14); When the pile section is connected to the prefabricated enlarged head II (42), the bottom of the pile section is embedded in the X-shaped mounting groove (401) of the prefabricated enlarged head II (42), and the pin passes through the pin hole (14) and the blind hole to fix the prefabricated enlarged head II (42) on the pile section.

4. A non-displacement prestressed X-shaped pile with an enlarged head according to claim 3, characterized in that: The diameter of the cylindrical structure of the prefabricated enlarged head I (41) / prefabricated enlarged head II (42) is 1.5-2 times the diameter of the outer circle of the X-shaped pile; the prefabricated enlarged head I (41) / prefabricated enlarged head II (42) is prefabricated with C30-C40 reinforced concrete and has an internal ring steel mesh; the material of the pin is Q235 steel.

5. A non-displacement prestressed X-shaped pile with an enlarged head according to claim 1, characterized in that: The X-shaped piles are precast using C60-C80 prestressed concrete, with longitudinal bars and stirrups embedded inside. The longitudinal bars are made of HRB400E threaded steel, and the stirrups are made of HRB400 spiral stirrups. The effective prestressing ratio is 10%-15%.

6. A non-displacement prestressed X-shaped pile with an enlarged head according to claim 1, characterized in that: The fluidized solidified soil includes on-site soil material, solidifying agent, water, and additives; The on-site soil material refers to the soil material generated during the on-site rotary drilling process. When the on-site soil material is insufficient, plain fill, cohesive soil, silt, sand, or a mixture of the four types of soil shall be used. The maximum particle size of the soil particles in the soil is ≤5cm, and the organic matter content of the soil is ≤5%. The curing agent includes ,active and The mass ratio is within the range of: Accounting for 40%-60%, active It accounts for 15%-30%. It accounts for 20%-40%; The additives include one or more of crystallization inducers, dispersants, surfactants, and micro-expansion agents; The mass fraction of each component of the fluidized solidified soil is as follows: when there are 100 parts of soil material on site, the solidifying agent is 6-10 parts and the water is 10-15 parts. The slump of the fluidized solidified soil is 180-220 mm, and the permeability coefficient is 1× cm / s-5× cm / s, 7-day unconfined compressive strength is 0.5MPa-5MPa.

7. A construction method for a non-displacement prestressed X-shaped pile with an enlarged head as described in any one of claims 1 to 6, characterized in that: The construction method for assembly method one includes the following steps: S1.

1. Based on the designed borehole diameter and designed pile bottom elevation, use a rotary drilling rig to rotary drill the pile hole; and clean the sediment at the bottom of the hole after drilling is completed; If the drilling area is a soft soil area, mud slurry should be used for wall protection during drilling; S1.2, Lower the prefabricated enlarged head I (41) to the bottom of the hole using hoisting equipment; S1.3 Install a special external pile clamp (5) at the pile hole opening, and determine whether pile splicing is required based on the pile hole height and pile section height. If so, proceed to step S1.4; otherwise, jump to step S1.

5. S1.

4. Based on the height of the pile hole and the height of the pile section, determine the required number of pile sections N; lower the first pile section. When the pile section is lowered to the opening of the pile hole, use the special pile clamp (5) outside the hole to position the pile section, and then connect the second pile section to the first pile section. Following the aforementioned method, N pile sections are connected sequentially to form an X-shaped pile; S1.

5. Use hoisting equipment to hoist the X-shaped pile, so that the X-shaped pile passes through the special pile clamp (5) outside the hole and extends into the bottom of the pile hole, and fits into the X-shaped installation groove of the prefabricated enlarged head I (41) (401). S1.

6. A grouting pipe is laid between the X-shaped pile and the pile hole wall. Fluidized solidified soil is pumped into the grouting pipe using a pumping device until the fluidized solidified soil backfills to the hole opening. During the pumping process, the grouting pipe is lifted. S1.7 After the backfilling of the fluidized solidified soil is completed, cover it with geotextile and keep it moist for 7-14 days. After the curing is completed, use the on-site core sampling method to test the unconfined compressive strength of the fluidized solidified soil, and at the same time test the vertical bearing capacity of the pile. The construction method for assembly method two includes the following steps: S2.

1. Based on the designed borehole diameter and designed pile bottom elevation, use a rotary drilling rig to rotary drill the pile hole; and clean the sediment at the bottom of the hole after drilling is completed; If the drilling area is a soft soil area, mud slurry should be used for wall protection during drilling; S2.

2. Outside the hole, insert the pile section into the X-shaped mounting groove (401) of the prefabricated enlarged head II (42), and then pass the pin through the pin hole (14) on the prefabricated enlarged head II (42) and the blind hole on the pile section to complete the connection between the X-shaped pile and the prefabricated enlarged head II (42); after the connection is completed, use a tension gauge to test; S2.3 Install a special external pile clamp (5) at the pile hole opening, and determine whether pile splicing is required based on the pile hole height and pile section height. If so, proceed to step S2.4; otherwise, jump to step S2.

5. S2.

4. Based on the height of the pile hole and the height of the pile section, determine the required number of pile sections N; lower the first pile section. When the pile section is lowered to the opening of the pile hole, use the special pile clamp (5) outside the hole to position the pile section, and then connect the second pile section to the first pile section. Following the aforementioned method, N pile sections are connected sequentially to form an X-shaped pile; S2.

5. The X-shaped pile is hoisted by hoisting equipment, so that the X-shaped pile passes through the special pile clamp (5) outside the hole and extends to the bottom of the pile hole; S2.

6. A grouting pipe is laid between the X-shaped pile and the pile hole wall. Fluidized solidified soil is pumped into the grouting pipe using a pumping device until the fluidized solidified soil backfills to the hole opening. During the pumping process, the grouting pipe is lifted. S2.7 After the backfilling of the fluidized solidified soil is completed, cover it with geotextile and keep it moist for 7-14 days. After the curing is completed, use the on-site core sampling method to test the unconfined compressive strength of the fluidized solidified soil, and at the same time test the vertical bearing capacity of the pile.

8. The construction method of the non-displacement prestressed X-shaped pile with enlarged head according to claim 7, characterized in that: In steps S1.3) and S2.3), the external hole-specific clamping device (5) includes an outer ring frame (15), a flange clamping unit (16), an inner concave arc clamping unit (17), and several support legs; Several of the aforementioned support legs are installed at intervals on the outer ring frame (15) and can be telescopically anchored into the soil for fixation; The outer ring frame (15) is circumferentially equipped with four flange clamping units (16) and four concave arc clamping units (17); the flange clamping units (16) and the concave arc clamping units (17) are spaced apart; The flange clamping unit (16) and the concave arc clamping unit (17) are respectively used to clamp the flange (7) of the X-shaped pile and to clamp the inner arc surface of the connecting flange (7); The flange clamping unit (16) / concave arc clamping unit (17) is a two-stage hydraulic clamping device, including oil inlet / outlet I (18), oil inlet / outlet II (19), bottom cover (20), first-stage clamping device cylinder (21), second-stage clamping cylinder (22), piston (24), oil inlet valve (25), and oil delivery pipeline (28). The cylinder body (21) of the first-stage clamping device is a cylindrical structure with a hollow interior, one open end and the other closed end. The closed end face of the cylinder body is provided with a through hole I, and the open end is connected to the bottom cover (20) of the hydraulic device to form a first-stage piston cavity. A secondary clamping cylinder (22) is slidably disposed within the primary piston cavity; the secondary clamping cylinder (22) comprises a large cylindrical section and a small cylindrical section coaxially connected; the large cylindrical section of the secondary clamping cylinder (22) is located within the primary piston cavity, and the end of the small cylindrical section away from the large cylindrical section extends out of the primary piston cavity through a through hole I; the large cylindrical section divides the primary piston cavity into primary piston cavity I (26) and primary piston cavity II (27); the primary piston cavity I (26) is formed by clamping the end face of the large cylindrical section of the primary clamping device cylinder (21) and the secondary clamping cylinder (22); the primary piston cavity II (27) is formed by clamping the small cylindrical section of the primary clamping device cylinder (21) and the transition surface between the large cylindrical section and the small cylindrical section of the secondary clamping cylinder (22); The end face of the small cylindrical section of the secondary clamping cylinder (22) away from the large cylindrical section is provided with a through hole II; the through hole II is connected to the secondary piston cavity inside the secondary clamping cylinder (22); A piston (24) is slidably connected in the secondary piston cavity of the secondary clamping cylinder (22); one end of the piston (24) extends out of the through hole II; the piston (24) divides the secondary piston cavity into secondary piston cavity I (29) and secondary piston cavity II (30); the secondary piston cavity I (29) is located near the bottom cover (20); an oil inlet valve (25) is provided at the center of the large cylindrical section of the secondary clamping cylinder (22). The hydraulic device bottom cover (20) is provided with an oil inlet / outlet port I (18); the oil inlet / outlet port I (18) is connected to the first-stage piston cavity I (26); an oil delivery pipe (28) is provided on the side wall of the small cylindrical section of the second-stage clamping cylinder (22); the two ends of the oil delivery pipe (28) are connected to the first-stage piston cavity II (27) and the second-stage piston cavity I (29) respectively; an oil inlet / outlet port II (19) is provided on the side wall of the first-stage clamping device cylinder (21); the oil inlet / outlet port II (19) is connected to the second-stage piston cavity I (29); The piston (24) has a gasket at the end extending out of the secondary clamping cylinder (22), and the gaskets on the flange clamping unit (16) and the concave arc clamping unit (17) are respectively adapted to the flange (7) and the inner arc surface.

9. The construction method of the non-displacement prestressed X-shaped pile with enlarged head according to claim 7, characterized in that: In steps S1.6) and S2.6), the process of preparing the fluidized solidified soil includes the following steps: S6.1 Collect the soil generated during rotary drilling in step S1.1) or step S2.1; S6.

2. Expansive soil, contaminated soil and saline soil in the soil material are removed by visual observation and laboratory geotechnical test, and the remaining soil material is put into a vibrating screen for crushing and screening to remove particles and impurities with a particle size >5cm. S6.

3. The organic matter content of the sieved soil is tested by burning. It is determined whether the organic matter content of the sieved soil is less than or equal to 5%. If so, proceed to step S6.4; otherwise, return to step S6.

1. S6.4, will ,active and Mix according to the preset ratio to make a curing agent; S6.5 Select water sources that meet the requirements for concrete water in GB / T14684-2022 "Construction Sand" as mixing water; if groundwater or surface water is used, the chloride ion content, sulfate content and pH value in the water need to be tested to see if they meet the requirements. S6.

6. Add the soil material from step S6.3) and the curing agent from step S6.4) into the mixer in proportion and perform preliminary mixing; then add the mixing water from step S6.5) into the mixer in proportion, wet mix for Tmin, then stop mixing to complete the production of fluidized solidified soil.

10. The construction method of the non-displacement prestressed X-shaped pile with enlarged head according to claim 7, characterized in that: During the curing process in steps S1.7) and S2.7), watering is used to keep the soil moist, with watering ≥3 times a day. When the ambient temperature is below 5℃, covering and heat preservation measures are taken. For the unconfined compressive strength test of fluidized solidified soil, at least 3 core samples need to be selected, and the average value of the test results is taken as the final strength value.

Images