CN113213879A

CN113213879A - Reinforced CFG pile mixture, CFG pile and composite foundation suitable for soft soil area and construction method of reinforced CFG pile mixture

Info

Publication number: CN113213879A
Application number: CN202110482058.4A
Authority: CN
Inventors: 徐海宁; 莫秋旭; 娄平; 李特; 焦昕远
Original assignee: Cscec Zhanjiang Avenue Investment Construction Co ltd; Central South University
Current assignee: Cscec Zhanjiang Avenue Investment Construction Co ltd; Central South University
Priority date: 2021-04-30
Filing date: 2021-04-30
Publication date: 2021-08-06

Abstract

The invention provides a reinforced CFG pile mixture, a CFG pile, a composite foundation and a construction method thereof, wherein the CFG pile mixture is prepared from cement, fly ash, fine aggregate, coarse aggregate, water, silicon powder, water glass and a polycarboxylic acid water reducing agent, and the mass ratio of the cement, the fly ash, the fine aggregate, the coarse aggregate, the water, the silicon powder, the water glass and the polycarboxylic acid water reducing agent is 180-220: 110-130: 750-900: 950 to 1200: 110-150: 10-20: 20-40: 1.3 to 1.5. According to the invention, by reducing the using amount of cement in the mixture, increasing the using amount of the fly ash and adding the high-efficiency polycarboxylic acid water reducing agent, the water glass and the silicon powder, the CFG pile cast by the mixture with the mixing ratio has good durability and corrosion resistance, the pile body strength and the bearing capacity of the CFG pile in a soft soil area can be effectively improved, the pile forming quality is improved, the material cost can be reduced by increasing the use amount of the fly ash, and the high-efficiency utilization of industrial byproducts is realized.

Description

Reinforced CFG pile mixture, CFG pile and composite foundation suitable for soft soil area and construction method of reinforced CFG pile mixture

Technical Field

The invention belongs to the technical field of CFG piles, and particularly relates to a reinforced CFG pile mixture, a CFG pile, a composite foundation and a construction method thereof, which are suitable for soft soil areas.

Background

Soft soil has high natural water content, large natural pore ratio, low bearing capacity and shear strength, generally shows a soft-plastic-flow-plastic state, and is not suitable for being directly used as a highway subgrade.

In the technical specification of highway subgrade construction (JTG-T3610-2019), it is pointed out that when the thickness of soft soil is less than 3m, methods such as replacement or shallow layer improvement can be adopted, but CFG piles are recommended to be arranged on thick soft soil layers to improve the bearing capacity of the foundation, and the CFG piles are widely applied to soft soil areas in China.

There are many problems with arranging CFG piles in soft soils. (1) The soft soil often contains more organic matters and inorganic salts, which can reduce the strength of the CFG pile, and particularly, the inorganic salts in the soft soil layer of the coastal area are rich in more sulfate ions and are easy to generate stronger corrosion action on the CFG pile; (2) when the load bearing capacity of the foundation with a high road grade is large, the pile head of the CFG pile is in danger of being damaged.

Concrete mixture C for traditional CFG pile₃The content of A is higher. Mixture major hydration productThe C-S-H gel reacts with sulfate to generate expanded ettringite (AFt) which causes cracking of the set cement and further damages the pile body structure. At the same time, the batch hydration product Ca (OH)₂Reacts with sulfate to generate gypsum, and further reacts with hydrated calcium aluminate to generate ettringite (AFt) to destroy the pile structure. According to the damage mechanism of sulfate to concrete, the reduction of C in the mixture can be found₃A and Ca (OH) in the slurry₂The content of (A) can effectively reduce the damage of sulfate to a concrete structure. The product of the reaction of the mixture hydration product and the sulfate, namely, the ettringite (AFt), mainly realizes the damage to the concrete structure through volume expansion, so that the compactness of the concrete is increased, and the sulfate is difficult to permeate into the structure and is also an important way for the concrete to resist sulfate erosion.

The fly ash is waste material produced by thermal power plant, and has a certain chemical activity capable of being mixed with Ca (OH) in cement₂The reaction occurs to generate new C-S-H gel without reacting with sulfate, and Ca (OH) in the structure is reduced₂The content of (a). The new C-S-H gel can effectively fill the pores in the structure, and enhance the compactness of the structure to prevent sulfate from corroding the interior of the structure. Meanwhile, for CFG piles, the cement consumption can be effectively reduced by increasing the content of the fly ash, and further C in the mixture is reduced₃The content of A can also reduce the construction cost by increasing the using amount of the fly ash from the economic point of view. The great reduction of the cement consumption in the CFG pile mixture can actually reduce C₃The content of A can also cause the strength of the pile body to be reduced.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects and shortcomings mentioned in the background art, and to provide a reinforced CFG pile mixture, a CFG pile, a composite foundation and a construction method thereof, which are suitable for soft soil areas,

in order to solve the technical problems, the technical scheme provided by the invention is as follows:

the reinforced CFG pile mixture is suitable for soft soil areas and is prepared from cement, fly ash, fine aggregate, coarse aggregate, water, silicon powder, water glass and a polycarboxylic acid water reducing agent, wherein the mass ratio of the cement to the fly ash to the fine aggregate to the coarse aggregate to the water to the silicon powder to the water glass to the polycarboxylic acid water reducing agent is 180-220: 110-130: 750-900: 950 to 1200: 110-150: 10-20: 20-40: 1.3 to 1.5.

In the CFG pile mixture, the cement has a cementing effect, the mixture is cemented together through hydration reaction, and the fly ash is doped into the CFG pile mixture to participate in the hydration reaction of the cement to generate new C-S-H gel, so that the sulfate erosion resistance of the CFG pile is improved. In the invention, a proper amount of polycarboxylic acid water reducing agent is introduced into the mixture, so that the pile strength is still kept at a higher level under the condition of higher mixing amount of the fly ash, and the water-cement ratio is reduced. Meanwhile, the strength of the pile body can be improved by adding water glass into the CFG pile mixture, wherein the water glass is Na₂O·SiO₂The aqueous solution can be used as a binder to be well mixed with cement, sand, stone and the like, so that the binding strength of the pile body is enhanced, and micro pores in the pile body are filled. The silicon powder is SiO escaping from silicon smelting industry₂The ultrafine particles of the particles can effectively fill the pores in the pile body, enhance the compactness of the pile body and prevent sulfate from corroding the inside of the pile body.

Preferably, the mass ratio of the cement, the fly ash, the fine aggregate, the coarse aggregate, the water, the silicon powder, the water glass and the polycarboxylic acid water reducing agent is 200: 130: 820: 1040: 130: 10: 30: 1.5.

preferably, the cement model is P.O 42.5.5-grade ordinary portland cement;

the grade of the fly ash is grade II;

the fine aggregate is medium coarse sand;

the coarse aggregate is crushed stone with the particle size of 5-20 mm;

preferably, the particle size of the silicon powder is 100-200 nm; the modulus of the water glass is 2.8-3.0, and the concentration is 15-25 Baume degrees; the polycarboxylate superplasticizer is a polycarboxylate superplasticizer taking methacrylic acid as a main chain. In the present invention, if the water glass modulus is lower than 2.8, the binding effect is not obtained and is weakened, and if the water glass modulus exceeds 3.0, the fluidity of concrete is affected and the slurry is too viscous to be easily stirred. The polycarboxylate superplasticizer adopting methacrylic acid as the main chain can greatly improve the early and later strength of concrete, and can be better suitable for concrete with higher content of fly ash.

As a general technical concept, the invention also provides a reinforced CFG pile suitable for soft soil areas, which comprises a pile body, wherein the pile body is a cast-in-place pile body, and the pile body is prepared from the CFG pile mixture.

Preferably, a pile cap is fixed at the top end of the pile body, the pile cap is a prefabricated reinforced concrete pile cap, the pile cap is of a square structure, a cylindrical groove matched with the top end of the pile body is formed in the bottom end of the pile cap, and the top end of the pile body is located in the cylindrical groove and is fixedly connected with the top surface of the cylindrical groove through a mortar layer.

In order to prevent the pile head from being damaged by pressure, a pile cap can be arranged on the pile head of the pile body. The pile cap can enlarge the bearing area of the top of the CFG pile so as to change the stress form of the pile top, and the strength of the pile cap can be better improved by arranging a certain amount of reinforcing steel bars in the pile cap. The pile cap adopts a prefabricated mode, can be directly buckled at the top of the CFG pile, and improves the construction speed. Meanwhile, a mortar layer is coated between the pile cap and the CFG pile head, so that the dynamic load transmitted to the pile head by the pile cap can be effectively reduced, and the pile head is well protected. The pile cap is set to be a square structure, so that prefabrication and transportation are facilitated.

Preferably, the length of the pile body is 8.5-10.5 m, and the pile diameter is 0.35-0.5 m; the length and the width of the pile cap are both 0.8-1.2 m, the thickness is 0.3-0.5 m, and the depth of the cylindrical groove is 0.09-0.11 m; the thickness of the mortar layer is 1.9-2.2 cm.

As a general technical concept, the present invention also provides a CFG pile composite foundation, including a foundation and a plurality of rows of the CFG piles distributed on the foundation.

Preferably, two adjacent rows of CFG piles are arranged in a staggered mode, the distance between any two adjacent pile bodies on the foundation is equal, and the distance between the axial leads of any two adjacent pile bodies is 1.5-2.0 m.

As a general technical concept, the present invention also provides a construction method of a CFG pile composite foundation, including the steps of:

1) leveling the construction site to a design elevation, compacting the soft soil layer on the surface, and taking a water-proof and drainage measure in the site;

2) arranging piles, driving a wooden pile mark in the center of a pile position and using lime to scatter grid lines;

3) moving a drilling machine to the center of a pile position, aligning a drill rod to the center of the pile position, ensuring that the verticality deviation of the CFG pile is less than 1%, and marking scales on the drill rod to judge the depth of a scale;

4) stirring the mixture according to a determined mixing proportion, sequentially feeding water glass, silicon powder, coarse aggregate, cement, water, fly ash, a polycarboxylic acid water reducing agent and fine aggregate, uniformly stirring the raw materials in a stirring barrel for 110-120 s, controlling the slump to be 160-200 mm, and conveying the obtained mixture;

5) moving the long spiral drilling machine to enable the drill bit to touch the ground, starting the drilling machine to drill slowly and then quickly, and stopping drilling when the pile tip reaches the designed drilling depth;

6) pumping the mixture into the drill hole, and starting to draw the drill pipe when the drill pipe core pipe is filled with the mixture; static lifting is adopted, continuous lifting is guaranteed, the minimum depth of the core pipe inserted into the mixture in the filling process is controlled to be 100cm, the pumping capacity of the mixture is matched with the pipe pulling speed, and the pipe pulling speed is controlled to be 2-3 m/min; covering the pile head with a cement bag after pouring and forming the pile, and protecting, wherein the elevation of the pile top is 40-50 cm higher than the designed elevation;

7) moving the long spiral drilling machine to the next pile position, and repeating the steps 3) -6);

8) after the CFG pile is poured for 28 days, cleaning soil between piles to a designed elevation, marking the designed elevation, and leveling the soil around the pile head to be 10cm lower than the designed elevation of the pile top;

9) laying a cutter walking groove, cutting the pile head from the designed elevation mark of the pile head, and polishing the cut pile head to expose fresh concrete to obtain a pile body;

10) uniformly coating a layer of mortar on the pile head of the pile body, hoisting the pile cap to the position above the pile head by using a crane after the mortar is coated, aligning the column-shaped groove reserved above the pile cap with the pile head, and then putting down the pile cap to fixedly connect the pile body and the pile cap.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the invention, the using amount of cement in the mixture is reduced, the using amount of fly ash is increased, and the high-efficiency polycarboxylic acid water reducing agent, the water glass and the silicon powder are added, so that the CFG pile cast by the mixture with the mixing ratio has good durability and corrosion resistance, and the pile body strength is improved while the pile has good performance of resisting sulfate corrosion. Meanwhile, the invention reduces the cement consumption and increases the fly ash consumption, thereby reducing the material cost and realizing the high-efficiency utilization of the industrial byproduct (fly ash).

2. Compared with the traditional cast-in-place pile cap, the prefabricated CFG pile cap adopted by the invention has better quality control effect, has stronger protection effect on the pile head of the CFG pile and can effectively improve the bearing capacity of the pile top. The mortar layer between the pile cap and the pile head can also play a good role in protecting the pile head of the CFG pile.

3. The method can effectively improve the pile body strength of the CFG pile in the soft soil area, improve the pile forming quality, effectively improve the bearing capacity of the CFG pile composite foundation in the soft soil area, and has obvious economic benefit and wide application prospect.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a graph showing the change in compressive strength of a cured test piece;

FIG. 2 is a graph showing the variation of the compressive strength of a corrosion test piece;

FIG. 3 is a front view of a reinforced CFG pile;

FIG. 4 is a cross-sectional view A-A of FIG. 3;

FIG. 5 is a cross-sectional view B-B of FIG. 3;

FIG. 6 is a top view of a CFG pile composite foundation;

FIG. 7 is a top view of the pile body distributed on the foundation;

FIG. 8 is a diagram of the bearing capacity range of the pile body;

illustration of the drawings:

1. CFG piles; 11. a pile body; 12. pile caps; 121. a cylindrical groove; 13. a mortar layer; 2. and (5) foundation construction.

Detailed Description

In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Examples 1 to 6 and comparative examples 1 to 10:

a CFG pile mixture is prepared from the following raw materials: cement, fly ash, fine aggregate, coarse aggregate, water, silicon powder, water glass and polycarboxylic acid water reducing agent. Wherein the cement type is P.O 42.5.5-grade ordinary portland cement; the grade of the fly ash is grade II; the fine aggregate is medium coarse sand; the coarse aggregate is crushed stone with the particle size of 5-20 mm; the particle size of the silicon powder is 100-200 nm; the modulus of the water glass is 2.9, and the concentration is 20 Baume degrees; the polycarboxylate superplasticizer is a polycarboxylate superplasticizer taking methacrylic acid as a main chain, and specifically is a CQJ-JSS002 polycarboxylate superplasticizer of Dingli brand.

Concrete test pieces are prepared from the CFG pile mixture, and the mixing proportion of the concrete test pieces in examples 1-6 and comparative examples 1-10 is specifically shown in Table 1.

The preparation method of the concrete test piece comprises the following steps: sequentially adding water glass, silicon powder, coarse aggregate, cement, water, fly ash and a polycarboxylic acid water reducing agent into a stirring barrel, finally adding fine aggregate, setting the stirring time to be 120s, pouring the mixture into a concrete sample mould, carrying out vibration molding by using a standard vibration table, trowelling after finishing vibration, collecting slurry, and trowelling once again, wherein the height difference between the surface of the slurry and the edge of the mould is not more than 0.5mm, and the size of the concrete sample is 100mm multiplied by 100 mm.

The concrete test piece is divided into a maintenance test piece and a corrosion test piece after being demoulded, the maintenance test piece and the corrosion test piece are firstly put into a constant-temperature clean water maintenance box (the temperature is 20 +/-2 ℃) for maintenance for 28 days, and after 28 days, the corrosion test piece is put into Na with the concentration of 15 percent₂SO₄The solution is soaked completely to simulate the corrosion environment (the temperature is 20 +/-2 ℃), the solution is replaced once a week to ensure the pH value to be stable, and the solution is maintained in the corrosion environment for 180 days.

According to the GBT 50081-2019 concrete physical and mechanical property test method standard, a 200t universal testing machine is adopted in the test to test the compression strength of the test piece. The compressive strength of the cured test piece cured by the clean water curing box for 28d and the compressive strength of the corrosion test piece cured by the clean water curing box for 28d and the corrosion test piece cured in the corrosion environment for 180d are shown in table 1, the compressive strength change curve of the concrete cured test piece is shown in fig. 1, and the compressive strength change curve of the corrosion test piece is shown in fig. 2. The mixing amount of the cement in the mixture for preparing the test piece is 200g, and the mixing amounts of other materials are mixed according to the mixing ratio in the table 1.

TABLE 1 concrete specimen matching ratio and compressive strength values of maintenance specimen and corrosion specimen

As can be seen from Table 1 and FIG. 1, the more fly ash is added, the more the compressive strength of the test piece is reduced, because the cement in the mixture plays a main role in cementation, and the excessive fly ash can affect the cementation of the cement; in addition, the more the water glass is mixed, the higher the compressive strength of the test piece is, because the viscosity of the water glass can ensure that the test piece is firmer, and meanwhile, partial holes in the test piece are filled up, so that the compactness of the test piece is better. And when the blending amount of the fly ash exceeds 150g, the compressive strength of the test piece does not meet the design requirement (the compressive strength of the CFG pile is not lower than 15MPa after 28d of maintenance).

As can be seen from table 1 and fig. 2, the compressive strength of the corrosion test pieces was decreased to a different degree after the sulfate attack than that of the cured test pieces. When the adding amount of the water glass is 10g, the compressive strength is reduced by about 3.1 MPa; when the adding amount of the water glass is 20g, the compressive strength is reduced by about 1.5 MPa; when the adding amount of the water glass is 30g, the compressive strength is reduced by about 0.5 MPa; when the amount of the water glass is 40g, the compressive strength is reduced by about 0.3 MPa.

From the above, the CFG pile mixture corresponding to embodiments 1 to 6 is suitable for preparing reinforced CFG piles suitable for soft soil areas. And comprehensive comparison shows that the mass ratio of cement, fly ash, fine aggregate, coarse aggregate, water, silicon powder, water glass and polycarboxylic acid water reducing agent in the CFG pile mixture is 200: 130: 820: 1040: 130: 10: 30: 1.5, the CFG pile has better economical efficiency and corrosion resistance.

Example 7:

as shown in fig. 3 to 5, in the reinforced CFG pile suitable for the soft soil area in this embodiment, the CFG pile 1 includes a pile body 11, the pile body 11 is a cast-in-place pile body, and the pile body 11 is prepared from any one of the CFG pile mixtures in embodiments 1 to 6.

In this embodiment, a pile cap 12 is fixed at the top end of the pile body 11, the pile cap 12 is a prefabricated reinforced concrete pile cap, the pile cap 12 is a square structure, a cylindrical groove 121 matched with the top end of the pile body 11 is formed at the bottom end of the pile cap 12, and the top end of the pile body 11 is located in the cylindrical groove 121 and is fixedly connected with the top surface of the cylindrical groove 121 through a mortar layer 13.

In order to prevent the pile head from being damaged by pressure, a pile cap 12 is arranged on the pile head of the pile body 11. The pile cap can enlarge the bearing area of the top of the CFG pile 1 so as to change the stress form of the pile top, and the strength of the pile cap can be better improved by arranging a certain number of reinforcing steel bars in the pile cap 12. Pile cap 12 adopts the prefabricated mode, can directly detain at pile body 11 top, has improved construction speed. Meanwhile, a mortar layer 13 is coated between the pile head of the pile cap 12 and the pile body 11, so that the dynamic load transmitted to the pile head by the pile cap 12 can be effectively reduced, and the pile head is well protected.

In the embodiment, the length of the pile body 11 is 8.5-10.5 m, and the pile diameter is 0.35-0.5 m; the length and the width of the pile cap 12 are both 0.8-1.2 m, the thickness is 0.3-0.5 m, and the depth of the cylindrical groove 121 is 0.09-0.11 m; the thickness of the mortar layer 13 is 1.9-2.2 cm.

In this embodiment, pile cap 12 is prefabricated C35 reinforced concrete pile cap, and the stirrup diameter is 7 ~ 9mm in pile cap 12, and the stirrup interval is 90 ~ 110mm, and the reinforcing bar model is HRB 235. The pile cap 12 is suitable in stirrup arrangement, high in strength and uniform in overall stress.

Example 8:

as shown in fig. 6 to 7, the CFG pile composite foundation in the present embodiment includes a foundation 2 and multiple rows of CFG piles 1 in embodiment 7 distributed on the foundation 2. In this embodiment, two adjacent rows of CFG piles 1 are staggered, and the distance between any two adjacent pile bodies 11 on the foundation 2 is equal, that is, each CFG pile and two CFG piles closest to the CFG pile in the other adjacent row of CFG piles are distributed in a regular triangle. The distance between the axial leads of any two adjacent pile bodies 11 is 1.5-2.0 m.

In the present embodiment, the pile pitch is calculated from numerical simulation, and relates to the engineering properties of the soil, the pile side friction, and the like. Through numerical simulation, the pile body 11 can obviously improve the bearing capacity of the soil body within a certain range, and the range is circular (shown as a shaded part in figure 8). The pile bodies 11 are arranged according to equal triangles (shown as a in fig. 8), so that the pile density in the same area is higher, the bearing effect is better, if the pile bodies are arranged according to a regular quadrangle (shown as b in fig. 8), the blank part in the middle is larger than that according to the equal triangle, and the cooperation effect of the pile soil arranged according to the equal triangle is better.

The construction method of the CFG pile composite foundation specifically comprises the following steps:

1) and removing attachments on the earth surface of the construction site, leveling the construction site to a designed elevation, compacting the soft soil layer on the surface, and taking water prevention and drainage measures in the site.

2) Pile arrangement is carried out on site according to a pile arrangement design drawing, a total station is used for lofting and taking out the center of a pile position, a wooden pile mark is driven into the center of the pile position, and lime is used for scattering grid lines.

3) And moving the drilling machine to the center of the pile position, and checking the guide rods of the tower body by using vertical marker posts at the front, the back, the left and the right of the tower body of the tower crane to correct the position, so that the drill rod is aligned to the center of the pile position, and the verticality deviation of the CFG pile is ensured to be less than 1%. Meanwhile, scales are marked on the drill rod to judge the depth of the drilling rod.

4) The method comprises the steps of stirring a mixture according to a determined mixing proportion, sequentially feeding water glass, silicon powder, coarse aggregate, cement, water, fly ash, a polycarboxylic acid water reducing agent and fine aggregate, uniformly stirring the raw materials in a stirring barrel, setting the stirring time to be 120s, controlling the slump to be 160-200 mm, conveying the mixture by using a concrete tank truck, and keeping the tank truck to rotate all the time in the conveying and waiting process.

5) And moving the long spiral drilling machine to enable the drill bit to touch the ground, starting the drilling machine to drill slowly and quickly, controlling the swing degree of the drill rod in the drilling process, checking the deviation of the drilled hole at any time to ensure the hole forming quality, and stopping drilling when the pile tip reaches the designed drilling depth. The waste soil generated by drilling holes is transported to a waste soil yard for centralized stacking and cannot be discarded at will.

6) And pumping the mixture into the drill hole, and drawing the pipe when the drill pipe core pipe is filled with the mixture. Static lifting is adopted, continuous lifting is guaranteed, reverse insertion is strictly forbidden during pipe pulling, overspeed lifting and first pipe pulling and then material pumping are strictly forbidden during construction. The minimum depth of the core tube inserted into the mixture during the pouring process is preferably controlled according to 100 cm. The pumping quantity of the mixture is matched with the tube drawing speed, and the tube drawing speed is controlled to be 2-3 m/min. And covering the pile head with a cement bag after pouring and forming the pile, and protecting, wherein the elevation of the pile top is 50cm higher than the designed elevation. After construction 28d no construction machine must travel on it.

7) And moving the long spiral drilling machine to the next pile position, and repeating the steps 3) -6). It should be noted that the CFG pile is drilled and discharged with a lot of soil during the field construction, and the surrounding pile positions are often covered, so the position of the CFG pile needs to be rechecked before the next CFG pile is constructed.

8) And after the CFG pile is poured for 28 days, cleaning soil among the piles to a designed elevation, marking the designed elevation, and leveling the soil around the pile head to be 10cm lower than the designed elevation of the pile top.

9) Laying a cutter walking groove, cutting the pile head from the designed elevation mark of the pile head, and polishing the cut pile head to expose fresh concrete to obtain a pile body 11.

10) Uniformly coating a layer of mortar on the pile head of the pile body 11, hanging the pile cap 12 above the pile head by a crane after the mortar is coated, aligning the column-shaped groove 121 reserved above the pile cap with the pile head, then putting down, and finally, fixedly connecting the pile body 11 and the pile cap 12 through the mortar layer 13. The arrangement of pile cap reinforcement is shown in figure 2.

Cutting the redundant part of the pile head of the CFG pile into a test piece of 100mm multiplied by 100mm (the mixture of the CFG pile adopts the mixture ratio in the embodiment 5), and adding Na with the concentration of 15 percent₂SO₄And (4) putting the mixture in the solution for 180d, and performing a compression test on the mixture. The test results and pile body test results are shown in table 2.

TABLE 2 pile head compression test and pile body test results

Note: the pile end of the type I pile is obviously reflected and has no defects.

The results in table 2 show that the CFG pile manufactured by the present invention has good durability and corrosion resistance. The construction method is applied to the construction of the Zhanjiang great road first-class highway.

Claims

1. The reinforced CFG pile mixture suitable for the soft soil area is characterized by being prepared from cement, fly ash, fine aggregate, coarse aggregate, water, silicon powder, water glass and a polycarboxylic acid water reducing agent, wherein the mass ratio of the cement, the fly ash, the fine aggregate, the coarse aggregate, the water, the silicon powder, the water glass and the polycarboxylic acid water reducing agent is 180-220: 110-130: 750-900: 950 to 1200: 110-150: 10-20: 20-40: 1.3 to 1.5.

2. The reinforced CFG pile mixture suitable for the soft soil area as claimed in claim 1, wherein the mass ratio of the cement, the fly ash, the fine aggregate, the coarse aggregate, the water, the silica powder, the water glass and the polycarboxylic acid water reducing agent is 200: 130: 820: 1040: 130: 10: 30: 1.5.

3. a reinforced CFG pile mix for soft soil areas according to claim 1 or 2, wherein the cement type is P.O 42.5.5 grade portland cement; the grade of the fly ash is grade II; the fine aggregate is medium coarse sand; the coarse aggregate is crushed stone with the particle size of 5-20 mm.

4. The reinforced CFG pile mixture suitable for the soft soil area according to claim 1 or 2, wherein the particle size of the silicon powder is 100-200 nm; the modulus of the water glass is 2.8-3.0, and the concentration is 15-25 Baume degrees; the polycarboxylate superplasticizer is a polycarboxylate superplasticizer taking methacrylic acid as a main chain.

5. A reinforced CFG pile suitable for soft soil areas, which is characterized in that the CFG pile (1) comprises a pile body (11), wherein the pile body (11) is a cast-in-place pile body, and the pile body (11) is prepared from the CFG pile mixture as claimed in any one of claims 1 to 4.

6. The reinforced CFG pile of claim 5, wherein a pile cap (12) is fixed at the top end of the pile body (11), the pile cap (12) is a prefabricated reinforced concrete pile cap, the pile cap (12) is of a square structure, a cylindrical groove (121) matched with the top end of the pile body (11) is formed in the bottom end of the pile cap (12), and the top end of the pile body (11) is located in the cylindrical groove (121) and is fixedly connected with the top surface of the cylindrical groove (121) through a mortar layer (13).

7. A reinforced CFG pile according to claim 5 or 6, wherein the pile body (11) has a length of 8.5-10.5 m and a pile diameter of 0.35-0.5 m; the length and the width of the pile cap (12) are both 0.8-1.2 m, the thickness is 0.3-0.5 m, and the depth of the cylindrical groove (121) is 0.09-0.11 m; the thickness of the mortar layer (13) is 1.9-2.2 cm.

8. A CFG pile composite foundation, characterized in that it comprises a foundation (2) and a plurality of rows of CFG piles (1) distributed over the foundation (2) according to any one of claims 5 to 7.

9. The CFG pile composite foundation as claimed in claim 8, wherein two adjacent rows of CFG piles (1) are arranged in a staggered manner, the distance between any two adjacent pile bodies (11) on the foundation (2) is equal, and the distance between the axial leads of any two adjacent pile bodies (11) is 1.5-2.0 m.

10. A construction method of the CFG pile composite foundation as claimed in claim 8 or 9, comprising the steps of:

3) moving the drilling machine to the center of the pile position, aligning a drill rod to the center of the pile position, ensuring that the verticality deviation of the CFG pile (1) is less than 1 percent, and simultaneously marking scales on the drill rod to judge the depth of the drilling rod;

8) after the CFG pile (1) is poured for 28 days, cleaning soil between piles to a designed elevation, marking at the designed elevation, and leveling the soil around the pile head to enable the soil to be 10cm lower than the designed elevation of the pile top;

9) laying a cutter walking groove, cutting the pile head from the designed elevation mark of the pile head, and polishing the cut pile head to expose fresh concrete to obtain a pile body (11);

10) uniformly coating a layer of mortar on the pile head of the pile body (11), after the mortar is coated, hoisting the pile cap (12) to the upper part of the pile head by using a crane, aligning a reserved cylindrical groove (13) above the pile cap with the pile head, and then putting down the pile head so as to fixedly connect the pile body (11) and the pile cap (12).