High-crack-resistance expanded precast pile curtain integrated supporting structure and construction method thereof

Abstract

The invention discloses a high-crack-resistance expanded precast pile curtain integrated supporting structure and a construction method thereof.The high-crack-resistance expanded precast pile curtain integrated supporting structure comprises a PRC pipe pile, hoops fixed to the PRC pipe pile at intervals, a plurality of anti-stripping keys fixed to the periphery of each hoop at intervals and fiber cement soil arranged on the PRC pipe pile; the hoop and the anti-stripping key form a hoop component. The invention further comprises a construction method. The discrete keys are arranged on the periphery of the hoop at intervals, the discrete keys flexibly transfer surrounding materials to participate in stress, dangerous concentrated stress at the interface of the PRC pipe pile and cement soil and stress around the discrete keys are effectively dispersed out, the probability that crack initiation lines appear at the interface of the PRC pipe pile and the cement soil and around the discrete keys is greatly reduced, and the performance of the PRC pipe pile is improved. The cracks can be blocked by the discrete keys when reaching the discrete keys, the phenomenon that the cracks penetrate along the PRC pipe piles is prevented, and the overall anti-seepage performance of the expanded precast pile-curtain integrated supporting structure is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of civil engineering, and particularly relates to a high-anti-crack expansion precast pile curtain integrated support structure and a construction method thereof. BACKGROUND With the continuous advancement of urbanization, high-rise buildings, underground rail transit and underground space development projects are increasing, and deep foundation pit engineering is facing new challenges in construction scale and technical difficulty. Under this background, the high-anti-crack expansion precast pile curtain integrated support structure as a kind of efficient support technology can solve the problems of soil stability and groundwater control in the deep foundation pit excavation process, and has begun to be applied in the current engineering. However, the anti-cracking performance of the cement soil curtain wall is poor, and the tensile side of the cement soil curtain wall is prone to initial cracks under the action of soil pressure. With the increase of the excavation depth of the foundation pit, such cracks tend to extend to the inside of the wall, and preferentially extend vertically along the interface between the PRC pipe pile and the cement soil, and finally lead to the failure of the water sealing function of the curtain wall.

[0002] How to design a high-anti-crack expansion precast pile curtain integrated support structure with high anti-cracking performance to reduce the occurrence of through cracks in the support structure and thus affect the anti-permeability of the expansion pile support curtain is a technical problem that needs to be solved at present. SUMMARY

[0003] The present application relates to the technical field of civil engineering, and particularly relates to a high-anti-crack expansion precast pile curtain integrated support structure and a construction method thereof.

[0004] In order to solve the above problems, the technical personnel have done a lot of research and test work, designed solutions from different directions, and carried out verification research, such as thickening the diameter of the PRC pipe pile, changing the formula proportion of the cement soil, and installing a hoop on the PRC pipe pile, etc. Some solutions have little effect, such as thickening the diameter of the PRC pipe pile. Some solutions have effect, but there is a big gap between the ideal effect, and the technical problem still cannot be solved, such as changing the formula proportion of the cement soil, and installing a hoop on the PRC pipe pile, etc. Later, the technical personnel added a continuous ring plate around the hoop, trying to block the expansion path of the fissure by dividing the outer circumference of the PRC pipe pile. The test results show that above and below the ring plate, the cement soil is subjected to overall and annular peeling, which is connected with the vertically expanding fissure to form a larger range of damage. After analysis, it is found that the upper and lower edges of the ring plate will form two continuous and annular stress concentration lines, and the cracks are very easy to initiate and expand on the two pre-prepared stress concentration lines, i.e. the crack initiation lines. Once broken at a certain point, the crack can expand very smoothly along the annular weak point. After a long time of analysis and test, the technical personnel creatively believe that breaking the annular stress concentration line is one of the keys to solving the technical problem, and puts forward a clever technical solution.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is: The high-anti-cracking expanded precast pile curtain integrated support structure comprises a PRC pipe pile, a hoop fixed at intervals on the PRC pipe pile, a plurality of anti-peeling keys fixed at intervals in the circumferential direction of each hoop, and a fiber cement soil arranged on the PRC pipe pile. The hoop and the anti-peeling key form a hoop member.

[0006] Preferably, the anti-peeling keys on adjacent hoop members are arranged in a staggered manner in the vertical direction, so that the anti-peeling keys on each hoop member form a continuous or overlapping projection structure in vertical projection.

[0007] Preferably, the interval distance between adjacent hoop members is two meters, the length of the anti-peeling key is three to five centimeters, and the thickness is less than or equal to three millimeters. The anti-peeling key is semicircular and the two side surfaces are flat.

[0008] Preferably, the hoop is a split pipe clamp hoop, comprising two semicircular hoop pieces and connecting bolts at the ends of the hoop pieces.

[0009] Preferably, the fiber cement soil comprises 4-6 parts by weight of basalt fiber, 2.5-5 parts by weight of sisal fiber, 1300-1600 parts by weight of soil, 280-350 parts by weight of cement, 80-100 parts by weight of fly ash, 200-250 parts by weight of water, and 3-5 parts by weight of water reducing agent.

[0010] The construction method of the high-anti-crack expansion precast pile curtain integrated support structure comprises the following steps: S1, precast component processing: a split pipe clamp hoop is made through the diameter of the pipe pile, and a semi-elliptical anti-peeling key is fixed on the surface of the hoop by welding process; S2, fiber preparation: the basalt fiber length is selected to be 10-12mm, and the sisal fiber length can be selected to be 10-15mm. The sisal fiber is soaked in 1% sodium hydroxide solution for 30 minutes, then washed clean with water and naturally dried, which can remove the impurities and grease on the surface of the fiber; The basalt fiber is soaked in 10% glacial acetic acid solution for 6 hours, then washed clean with water and naturally dried, which can slightly etch the surface of the fiber and increase the roughness; S2, fiber cement soil preparation: according to the fiber cement soil ratio, the soil, cement and fly ash are poured into the mixer and dry-mixed for 1-2 minutes; then, the basalt fiber and sisal fiber are pre-mixed with a small amount of dry material, and then slowly and evenly scattered into the mixer, and dry-mixed for 2-3 minutes to make the fiber fully wrapped and dispersed by the dry material; the water reducing agent is dissolved in water in advance to form a uniform solution, and the water containing the water reducing agent is added in batches under the operation state of the mixer, and the mixture is continuously stirred for 3-5 minutes to form a homogeneous slurry; (4) support structure construction: long spiral drilling machine is used to implement continuous drilling operation, the drill rod rotates to cut the soil layer, and the spiral blade realizes vertical transportation of the soil body at the same time, and auxiliary compressed air is sprayed to remove the soil; after reaching the design elevation, the drill rod is lifted at a constant rate, and the fiber cement soil is simultaneously injected through the central passage of the drill bit, after the drill rod is lifted, the drill moves to the next pile position, and the above steps are repeated to realize continuous construction; before the fiber cement soil is initially cured, the PRC pipe pile is pressed into the design elevation by using the pile press; the following steps are used to install the hoop component in the specified pipe pile section during the pile pressing process: a. surface treatment: the floating slurry, oil stains and loose materials at the installation position of the pipe pile section where the pile holding component is installed are removed by using a mechanical polishing tool; b. coating adhesive: the surface of the clean PRC pipe pile and the inner side joint surface of the hoop are uniformly coated with a layer of room temperature rapid curing type epoxy resin structural adhesive; c. installation and fastening: the glued hoop is accurately positioned and sleeved on the PRC pipe pile at the designed position, and the bolt is immediately fastened, so that the adhesive is uniformly extruded from the joint, ensuring that the hoop and the pipe pile are in full-area contact and form an initial bonding strength; d. subsequent pile pressing: after the hoop installation is completed, the pile pressing is continued to the next installation station, and the above steps are repeated until the pile pressing is completed, and finally a high-anti-crack expansion precast pile curtain integrated support structure with good overall performance is formed.

[0011] 1. The present application proposes to arrange discrete keys at intervals around the hoop, which is different from the rigid, continuous constraint of the circular plate and the stress concentration on its own edge. The discrete keys flexibly mobilize the surrounding material to participate in force, effectively dispersing the dangerous concentrated stress at the PRC pipe pile and cement soil interface and the stress around the discrete key, greatly reducing the probability of the occurrence of the cracking line at the PRC pipe pile and cement soil interface and around the discrete key. If a crack occurs in the PRC pipe pile, the crack mainly extends along the interface between the PRC pipe pile and the cement soil, and is blocked by the discrete key. If the expansion force of the crack is relatively large, the crack can only continue to expand by bypassing the discrete key after being blocked by the discrete key. In this process, the expansion path is lengthened and changed, the expansion energy is dissipated, and the crack expansion ability is greatly weakened. The crack expands at the same time as the interface peels off. The anti-peeling key can also block the peeling process, further weaken the energy of the crack, and eventually stop the expansion of the crack, thereby achieving "passivation" and prevention of the crack along the PRC pipe pile. The overall anti-seepage performance of the expanded body precast pile-curtain integrated support structure is significantly improved.

[0012] 2. Interface bonding strength and synergistic working mechanism: The anti-peeling key is embedded in the cement soil, producing a significant mechanical embedding effect, and changing the interface connection from pure bonding and friction to the combined action of mechanical interlocking and friction. This design can greatly improve the interface shear strength.

[0013] 3. Material performance optimization: Basalt fibers and sisal fibers are added to the cement soil to take advantage of the synergistic effect of the fibers: basalt fibers have high elastic modulus and mainly provide primary reinforcement to inhibit the generation of microcracks; sisal fibers have good toughness and large elongation, and mainly provide secondary toughening to prevent macrocrack expansion. The combination of the two can improve the strength and deformation capacity of the cement soil, thereby improving the crack resistance of the cement soil curtain wall.

[0014] 4. The anti-peeling keys on adjacent hoop members are arranged in a staggered manner in the vertical direction, so that the anti-peeling keys on each hoop member form a continuously arranged or overlapping arranged projection structure in vertical projection. In this way, for cracks with relatively high crack expansion energy, even if they pass the first anti-peeling key, they will still encounter the same blocking or weakening effect of the next anti-peeling key, preventing the formation of a through crack.

[0015] This invention addresses the safety hazards of the overall structure through innovative structural design and localized, low-cost construction measures. The anti-stripping bonds and the composite fibers in the fiber-reinforced cementitious soil form a synergistic defense. The fibers suppress micro-cracks in the cementitious soil matrix at the microscale, while the anti-stripping bonds block penetrating cracks along the interface at the macroscale. Together, they ensure the integrity of the support structure during deep foundation excavation. Compared to simply increasing material usage or using fully tough cement-based materials, the cost increase is less than 5%, but the overall structural reliability and life-cycle cost-effectiveness are significantly optimized. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the construction of the high crack resistance precast pile curtain integrated support structure in this invention; Figure 2 This is a schematic diagram of a PRC pipe pile containing a clamping component in this invention; Figure 3 This is a schematic diagram of the clamp component in this invention; Figure 4 This is a schematic diagram of crack propagation in this invention.

[0017] In the diagram: 1. PRC pipe pile; 2. Anti-peeling key; 3. Clamp; 4. Bolt; 5. Fiber cement soil; 6. Crack. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. The following specific embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should also be noted that, for ease of description, only the parts related to the present invention are shown in the drawings, and not all of them. Example

[0019] Highly crack-resistant precast pile curtain wall integrated support structure, such as Figures 1-4 As shown, the structure includes a PRC pipe pile 1, clamps 3 fixed at intervals on the PRC pipe pile, multiple anti-peeling keys 2 fixed at circumferential intervals in each clamp, and fiber cement soil 5 provided on the PRC pipe pile. The clamps and anti-peeling keys form a clamp component. The anti-peeling keys on adjacent clamp components are staggered in the vertical direction, so that the anti-peeling keys on each clamp component form a continuous or overlapping projection structure in the vertical projection. In this way, for cracks 6 with relatively high crack propagation energy, even if they have passed the first anti-peeling key, they will still encounter the same blocking or weakening effect of the next anti-peeling key, preventing the crack from forming a through crack.

[0020] In this embodiment, the spacing between adjacent clamp components is two meters. The anti-peeling key is three to five centimeters long and less than or equal to three millimeters thick. In this embodiment, a length of five centimeters and a thickness of three millimeters are used. The anti-peeling key is semi-elliptical with two flat sides. The clamp is a split-type pipe clamp, including two semi-circular clamp plates and connecting bolts 4 at the ends of the clamp plates. The fiber cement soil includes 4-6 parts by weight of basalt fiber, 2.5-5 parts by weight of sisal fiber, 1300-1600 parts by weight of soil, 280-350 parts by weight of cement, 80-100 parts by weight of fly ash, 200-250 parts by weight of water, and 3-5 parts by weight of water-reducing agent. Example

[0021] Construction methods for high crack-resistant precast pile curtain integrated support structures, such as... Figures 1-4 As shown, it includes the following steps: S1. Precast component processing: Split pipe clamps are made according to the diameter of the pipe pile, and semi-elliptical anti-peeling keys are fixed to the surface of the clamp using welding process. S2. Fiber preparation: Basalt fiber length should be 10-12mm, and sisal fiber length should be 10-15mm. Sisal fibers are soaked in a 1% sodium hydroxide solution for 30 minutes, then rinsed with clean water and air-dried naturally. This treatment can remove impurities and grease from the fiber surface. Basalt fibers are soaked in a 10% glacial acetic acid solution for 6 hours, then rinsed with clean water and air-dried. This treatment can slightly etch the fiber surface and increase its roughness. S2. Preparation of fiber-reinforced cement soil: Based on basalt fiber 5kg / m³ 3 3kg / m³ of sisal fiber 3 ; Soil material 1500kg / m 3 Cement 320kg / m 3 ; fly ash 80kg / m 3 Water 240kg / m 3 Water-reducing agent 3kg / m 3 To prepare the fiber cement soil, pour the soil, cement, and fly ash into the mixer and dry mix for 1-2 minutes until evenly mixed. Then, premix the basalt fiber and sisal fiber with a small amount of dry material, and slowly and evenly sprinkle them into the mixer. Continue to dry mix for 2-3 minutes to ensure that the fibers are fully coated and dispersed by the dry material. Dissolve the water-reducing agent in water in advance to form a uniform solution. While the mixer is running, add the water containing the water-reducing agent in batches and continue mixing for 3-5 minutes to form a homogeneous slurry. (4) Support structure construction: long spiral drilling machine is used to implement continuous drilling operation, the soil is vertically transported through the spiral blade while the drill pipe is rotating and cutting the soil layer, and compressed air is sprayed to assist soil removal; after reaching the design elevation, the drill pipe is lifted at a constant rate, and the fiber cement soil is injected through the drill bit center channel at the same time, after the drill pipe is lifted, the drill moves to the next pile position, and the above steps are repeated to realize continuous construction; for the excavation depth of 8m foundation pit engineering, PRC pipe pile with length of 14m and diameter of 500mm is used, and curtain wall with thickness of 800mm is used, before the fiber cement soil is initially cured, the PRC pipe pile is pressed into the design elevation by the pile presser, and a PRC pipe pile is pressed into every 1.5m; a. Surface treatment: the pipe pile section where the pile holding member is installed is cleaned of the floating slurry, oil stains and loose materials at the installation site using a mechanical polishing tool; b. Coating adhesive: treating the clean PRC pipe pile surface and the inner side joint surface of the hoop, evenly coating a layer of room temperature rapid curing type epoxy resin structural adhesive; c. Installation and fastening: accurately positioning and sleeving the glued hoop at the designed position of the PRC pipe pile, immediately fastening the bolt, making the adhesive uniformly extruded from the joint, ensuring that the hoop and the pipe pile are in full-area contact and form initial bonding strength; d. Subsequent pile pressing: after the hoop installation is completed, continue to press the pile to the next installation station, repeat the above steps until the pile pressing is completed, and finally form the integrated high crack-resistant expanded precast pile curtain integrated support structure.

[0022] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it. Those skilled in the art should understand that it is not necessary or possible to exhaust all embodiments. It should be noted that without departing from the concept of the present application, the device can be deformed or modified. These are within the scope of the present application. Any modification, equivalent replacement and improvement made within the spirit and principles of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A high-crack-resistant precast pile curtain integrated support structure, characterized in that: It includes PRC pipe piles, clamps fixed at intervals on the PRC pipe piles, multiple anti-peeling keys fixed at circumferential intervals in each clamp, and fiber cement soil provided on the PRC pipe piles. The clamps and anti-peeling keys form a clamp component.

2. The high crack-resistant precast pile curtain integrated support structure as described in claim 1, characterized in that: The anti-peeling keys on adjacent clamping components are staggered in the vertical direction, so that the anti-peeling keys on each clamping component form a continuous or overlapping projection structure in the vertical projection.

3. The high crack-resistant precast pile curtain integrated support structure as described in claim 1, characterized in that: The spacing between adjacent clamp components is two meters. The length of the anti-peeling key is three to five centimeters and the thickness is less than or equal to three millimeters. The anti-peeling key is semi-elliptical and has two flat sides.

4. The high crack-resistant precast pile curtain integrated support structure as described in claim 2, characterized in that: The clamp is a split-type pipe clamp, which includes two semi-circular clamp plates and connecting bolts at the ends of the clamp plates.

5. The high crack-resistant precast pile curtain integrated support structure as described in claim 3, characterized in that: The fiber cement soil comprises 4-6 parts by weight of basalt fiber, 2.5-5 parts by weight of sisal fiber, 1300-1600 parts by weight of soil, 280-350 parts by weight of cement, 80-100 parts by weight of fly ash, 200-250 parts by weight of water, and 3-5 parts by weight of water-reducing agent.

6. A construction method for a high crack-resistant precast pile curtain integrated support structure, characterized in that... Includes the following steps: S1. Precast component processing: Split pipe clamps are made according to the diameter of the pipe pile, and semi-elliptical anti-peeling keys are fixed to the surface of the clamp using welding process. S2. Fiber preparation: Basalt fiber length should be 10-12mm, and sisal fiber length should be 10-15mm. Sisal fibers are soaked in a 1% sodium hydroxide solution for 30 minutes, then rinsed with clean water and air-dried naturally. This treatment can remove impurities and grease from the fiber surface. Basalt fibers are soaked in a 10% glacial acetic acid solution for 6 hours, then rinsed with clean water and air-dried. This treatment can slightly etch the fiber surface and increase its roughness. S2. Preparation of fiber cement soil: According to the fiber cement soil ratio described in claim 4, the soil material, cement, and fly ash are poured into a mixer and dry-mixed for 1-2 minutes until uniformly mixed; then, basalt fiber and sisal fiber are premixed with a small amount of dry material and slowly and evenly sprinkled into the mixer, and dry-mixed for another 2-3 minutes to ensure that the fibers are fully coated and dispersed by the dry material; the water-reducing agent is dissolved in water in advance to form a uniform solution, and while the mixer is running, water containing the water-reducing agent is added in portions, and the mixture is continuously stirred for 3-5 minutes to form a homogeneous slurry; (4) Support structure construction: Continuous drilling is carried out using a long spiral drilling machine. While the drill rod rotates and cuts the soil layer, the soil is vertically transported through the spiral blades, and compressed air is injected to assist in soil removal. After reaching the design elevation, the drill rod is raised at a constant rate, and fiber cement soil is injected through the central channel of the drill bit. After the drill is lifted, the drilling rig is moved to the next pile position, and the above steps are repeated to achieve continuous construction. Before the fiber cement soil initially sets, the PRC pipe piles are driven into the design elevation using a pile driver. The pile driving process involves installing clamp components on the designated pipe pile section according to the following steps: a. Surface treatment: On the pipe pile section where the pile clamping component is installed, use mechanical grinding tools to remove laitance, oil stains and loose materials from the installation area; b. Apply adhesive: Clean the surface of the PRC pipe pile and the inner joint surface of the clamp, and evenly apply a layer of room temperature fast curing epoxy resin structural adhesive. c. Installation and fastening: After applying the adhesive, accurately align the clamp and fit it into the designed position of the PRC pipe pile. Immediately tighten the bolts to allow the adhesive to be evenly squeezed out from the interface, ensuring that the clamp and the pipe pile are in full contact and form initial bond strength. d. Subsequent pile driving: After the clamps are installed, continue pile driving to the next installation position, repeating the above steps until pile driving is completed, ultimately forming a high crack-resistant precast pile curtain integrated support structure with good integrity.

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