CN112028571A - Cast-in-place pile for enhancing bearing strength of deep and thick miscellaneous fill area and construction method - Google Patents

Abstract

The invention discloses a cast-in-place pile for enhancing the bearing strength of a deep and thick miscellaneous fill area and a construction method, and relates to the technical field of cast-in-place piles, wherein the cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area is prepared from the following raw materials in parts by weight: cement: 355-365 parts of fly ash: 150 and 160 parts of gravel: 1240 and 1250 parts, river sand: 620 and 625 parts of expanding agent: 12-16 parts of a stabilizer: 6-8 parts of a water reducing agent: 4.2-4.8 parts of water: 175-185 parts; the expanding agent comprises calcium oxide, calcium carbonate and silicon micropowder, wherein the weight ratio of the calcium oxide to the calcium carbonate to the silicon micropowder is (24-26): (12-13): (6-6.5). The cast-in-place pile has the effects of good chloride ion resistance and good sulfate resistance.

Description

Cast-in-place pile for enhancing bearing strength of deep and thick miscellaneous fill area and construction method

Technical Field

The invention relates to the technical field of cast-in-place piles, in particular to a cast-in-place pile for enhancing the bearing strength in deep and thick miscellaneous fill areas and a construction method.

Background

With the continuous promotion of the basic construction of China, the abandoned soil yard fields in a plurality of roads, railways and industrial civil buildings are inevitably utilized as construction fields. A considerable part of the field has a deep miscellaneous filling stratum, and because the miscellaneous filling soil has the characteristics of complicated sources and compositions, uneven properties, poor stability and the like, the miscellaneous filling soil can not be directly used as a building foundation generally, and a cast-in-place pile foundation is required to directly penetrate the miscellaneous filling stratum.

Because the part of the cast-in-place pile buried in the miscellaneous fill area is in a relatively humid environment for a long time, the corrosion efficiency of chloride ions or sulfate on a reinforcement cage in the cast-in-place pile is easily accelerated, the bearing strength of the cast-in-place pile is reduced, and the engineering has relatively large potential safety hazards.

Disclosure of Invention

The first purpose of the invention is to provide a cast-in-place pile for enhancing the bearing strength in deep and thick miscellaneous fill areas, which has the advantages of good chloride ion penetration resistance and good sulfate penetration resistance.

The second purpose of the invention is to provide a construction method of a cast-in-place pile for enhancing the bearing strength in deep and thick miscellaneous fill areas, which has the advantages of good impermeability and high bearing strength.

In order to achieve the first object, the invention provides the following technical scheme:

the cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area is prepared from the following raw materials in parts by weight:

cement: 355-365 parts

Fly ash: 150 portions to 160 portions

Crushing stone: 1240 and 1250 parts

River sand: 620 portion and 625 portion

Swelling agent: 12 to 16 portions of

A stabilizer: 6 to 8 portions of

Water reducing agent: 4.2 to 4.8 portions of

Water: 175 part by weight and 185 parts by weight

The expanding agent comprises calcium oxide, calcium carbonate and silicon micropowder, wherein the weight ratio of the calcium oxide to the calcium carbonate to the silicon micropowder is (24-26): (12-13): (6-6.5).

By adopting the technical scheme, the expanding agent reacts with water to generate a unit cell with larger volume, which is beneficial to reducing the porosity of cast-in-place pile concrete, thereby improving the chloride ion permeability resistance and the sulfate permeability resistance of the cast-in-place pile; the stabilizer and the expanding agent have a synergistic effect, and the stability of unit cell volume is enhanced, so that the chloride ion permeation resistance and the sulfate permeation resistance of the cast-in-place pile are further enhanced.

Further: the stabilizer comprises sodium gluconate and polyisobutylene succinimide, and the weight ratio of the sodium gluconate to the polyisobutylene succinimide is (5-6): (1-2).

By adopting the technical scheme, when sodium gluconate and polyisobutylene succinimide are used as the stabilizing agents, the synergistic effect of the stabilizing agents and the expanding agents is good, and the problem that the unit cell volume is greatly changed due to temperature can be effectively solved, so that the chlorine ion permeation resistance and the sulfate permeation resistance of the cast-in-place pile are further improved.

Further: the preparation method of the expanding agent comprises the following steps:

step 1, preparing calcium oxide, calcium carbonate and silicon micropowder according to a ratio and uniformly mixing to obtain a premix;

step 2, sending the pre-mixture into a ball mill for ball milling for 2-3h at the ball milling speed of 450-;

and 3, drying and crushing the intermediate mixture to obtain the expanding agent with the particle size of less than or equal to 100 microns.

By adopting the technical scheme, the expanding agent prepared by firstly carrying out low-speed ball milling and then carrying out high-speed ball milling on the calcium oxide, the calcium carbonate and the silicon micropowder in the ball mill can reduce the porosity of the cast-in-place pile concrete when being applied to the cast-in-place pile concrete, and is beneficial to improving the chloride ion permeability resistance and the sulfate permeability resistance of the cast-in-place pile.

Further: the water reducing agent comprises a polycarboxylate water reducing agent and a lignosulfonate water reducing agent in a weight ratio of (1.0-1.2) to 1.

By adopting the technical scheme, the water reducing agent adopts the polycarboxylate water reducing agent and the lignosulfonate water reducing agent with the weight ratio of (1.0-1.2):1, and the water reducing agent not only can reduce the water-cement ratio of the cast-in-place pile concrete, but also has good compatibility with other components, and is beneficial to improving the impermeability of the cast-in-place pile.

Further: the feed also comprises the following raw materials in parts by weight:

air entraining agent: 0.7 to 0.9 portion.

Through adopting above-mentioned technical scheme, air entraining agent can bring into little and discontinuous bubble in the concrete to reduce the inside possibility of chloride ion and sulphate infiltration concrete, be favorable to improving the chloride ion barrier property and the sulphate barrier property of bored concrete pile concrete.

Further: the air entraining agent comprises (6-8) by weight: 1 and sucrose.

By adopting the technical scheme, the air entraining agent adopts a mixture of triterpenoid saponin and cane sugar, wherein the triterpenoid saponin is taken as the air entraining agent and can bring tiny and discontinuous bubbles into the concrete, so that the possibility of chloride ions and sulfate penetrating into the concrete is reduced, and the improvement of the chloride ion penetration resistance and the sulfate penetration resistance of the cast-in-place pile is facilitated; and the sucrose has a foam stabilizing effect, can stabilize bubbles introduced by the triterpenoid saponin, and is beneficial to further improving the effect of the air entraining agent.

Further: the cement is P.II42.5R portland cement.

By adopting the technical scheme, the P.II42.5R portland cement has high hydration speed, generates a condensation structure immediately after the cement is hydrated with water, has good water retention property, is not easy to form an open capillary channel when being mixed with concrete, and is beneficial to improving the impermeability of cast-in-place pile concrete.

Further: the fly ash is I-grade fly ash.

By adopting the technical scheme, the grade I fly ash has larger fineness, larger specific surface area and enhanced surface activity, can promote the flocculation decomposition effect of cement hydration, and simultaneously can improve the fluidity of cast-in-place pile concrete and reduce the possibility of pile breakage.

Further: the broken stone is 5-15mm in continuous gradation.

By adopting the technical scheme, when the broken stones are broken stones with the continuous gradation of 5-15mm, the holes among the concrete are favorably reduced, so that the chloride ion permeability resistance and the sulfate permeability resistance of the cast-in-place pile concrete are improved.

The second purpose of the invention is to provide a construction method of any one of the cast-in-place piles for enhancing the bearing strength in the deep and miscellaneous filled-up area, which comprises the following steps:

step S1, drilling: checking whether the formed hole has deflection phenomenon at any time in the drilling process, and correcting in time;

step S2, lowering a reinforcement cage: the reinforcement cage is coaxial with the central shaft of the drill hole;

step S3, preparing concrete: dissolving a stabilizer and a water reducing agent in water according to a ratio to form an additive solution; uniformly mixing cement and fly ash according to a ratio to form a gelled mixture; uniformly mixing broken stone and river sand according to a ratio to form an aggregate mixture; uniformly stirring the gelled mixture, the aggregate mixture, the expanding agent and the additive solution to obtain fresh concrete;

step S4, pouring concrete: and continuously pouring the fresh concrete into the drilled hole, standing, and forming the cast-in-place pile after the concrete is condensed.

By adopting the technical scheme, after the cast-in-place pile is poured by the fresh concrete prepared by the formula and the method, the cast-in-place pile has excellent chloride ion permeability resistance and sulfate permeability resistance, can reduce the corrosion action of chloride ions and sulfate on a reinforcement cage, is favorable for ensuring the bearing strength of the cast-in-place pile, and further reduces the potential safety hazard in engineering.

In conclusion, the invention has the following beneficial effects:

firstly, as the expanding agent reacts with water to generate a unit cell with larger volume, the porosity of cast-in-place pile concrete is favorably reduced, so that the chloride ion permeability resistance and the sulfate permeability resistance of the cast-in-place pile are improved; the stabilizer and the expanding agent have a synergistic effect, and the stability of unit cell volume is enhanced, so that the chloride ion permeation resistance and the sulfate permeation resistance of the cast-in-place pile are further enhanced.

Secondly, sodium gluconate and polyisobutylene polysuccinimide are preferably adopted as the stabilizing agents, the synergistic effect of the stabilizing agents and the expanding agents is good, and the problem that the unit cell volume is greatly changed due to temperature can be effectively solved, so that the chloride ion permeation resistance and the sulfate permeation resistance of the cast-in-place pile are further improved.

Thirdly, after the cast-in-place pile is poured by the fresh concrete prepared by the formula and the method, the cast-in-place pile has excellent chloride ion permeability resistance and sulfate permeability resistance, can reduce the corrosion action of chloride ions and sulfate on a reinforcement cage, and is beneficial to ensuring the bearing strength of the cast-in-place pile, thereby reducing the potential safety hazard in engineering.

Detailed Description

The present invention will be described in further detail below.

The sources of the raw materials involved in the present invention are shown in table 1 below.

Table 1 sources of materials to which the invention relates

Preparation example

The components and proportions of the swelling agents of preparation examples 1 to 3 are shown in Table 2 below.

TABLE 2 composition and ratio (unit/kg) of swelling agent in preparation examples 1-3

Components	Preparation example 1	Preparation example 2	Preparation example 3
				Calcium oxide	24	25	26
Calcium carbonate	12	12.5	13
				Silicon micropowder	6	6.2	6.5

Preparation example 1

The preparation method of the expanding agent comprises the following steps:

step 1, preparing calcium oxide, calcium carbonate and silicon micropowder according to the proportion in table 2, and uniformly mixing to obtain a premix;

step 2, sending the pre-mixture into a ball mill to perform ball milling for 2 hours at a ball milling speed of 650rad/min, increasing the ball milling speed of the ball mill to 800rad/min, and continuing ball milling for 30 minutes to obtain an intermediate mixture;

and 3, drying and crushing the intermediate mixture to obtain the expanding agent with the particle size of less than or equal to 100 microns.

Preparation example 2

An expanding agent, which is different from the preparation example 1 in that:

and 2, conveying the pre-mixture into a ball mill, carrying out ball milling for 2.5h at the ball milling speed of 550rad/min, increasing the ball milling speed of the ball mill to 850rad/min, and continuing ball milling for 25min to obtain an intermediate mixture.

Preparation example 3

An expanding agent, which is different from the preparation example 1 in that:

and 2, feeding the pre-mixture into a ball mill, carrying out ball milling for 3h at the ball milling speed of 450rad/min, increasing the ball milling speed of the ball mill to 900rad/min, and continuing ball milling for 20min to obtain an intermediate mixture.

Preparation example 4

An expanding agent, which is different from the preparation example 1 in that:

and 2, feeding the pre-mixture into a ball mill, performing ball milling for 2 hours at a ball milling speed of 800rad/min, increasing the ball milling speed of the ball mill to 650rad/min, and continuing ball milling for 30 minutes to obtain an intermediate mixture.

Preparation example 5

An expanding agent, which is different from the preparation example 1 in that:

and 2, feeding the pre-mixture into a ball mill to perform ball milling for 2 hours at a ball milling speed of 650rad/min to obtain an intermediate mixture.

Preparation example 6

An expanding agent, which is different from the preparation example 1 in that:

and 2, conveying the pre-mixture into a ball mill to perform ball milling for 30min at the ball milling speed of 800rad/min to obtain an intermediate mixture.

Preparation example 7

An expanding agent, which is different from the preparation example 1 in that:

and 3, drying and crushing the intermediate mixture to obtain the expanding agent with the particle size of less than or equal to 300 mu m.

Examples

The components and proportions of the cast-in-place pile for enhancing the bearing strength in the deep and thick miscellaneous fill area in examples 1-3 are shown in Table 3 below.

TABLE 3 composition and ratio (unit/kg) of cast-in-place pile in examples 1-3

The construction method of the cast-in-place pile for enhancing the bearing strength in the deep and thick miscellaneous fill area in the above embodiment 1-3 is as follows:

step S1, drilling: checking whether the formed hole has deflection phenomenon at any time in the drilling process, and correcting in time;

step S2, lowering a reinforcement cage: the central shaft of the reinforcement cage is coaxial with the central shaft of the drill hole;

step S3, preparing concrete: weighing cement, fly ash, broken stone, river sand, the expanding agent, the stabilizing agent, the water reducing agent and water prepared in the preparation example 1 according to the mixture ratio in the table 3; dissolving a stabilizer and a water reducing agent in water to form an additive solution; uniformly mixing cement and fly ash according to a ratio to form a gelled mixture; uniformly mixing broken stone and river sand according to a ratio to form an aggregate mixture; uniformly stirring the gelled mixture, the aggregate mixture, the expanding agent prepared in the preparation example 1 and the additive solution to obtain fresh concrete;

step S4, pouring concrete: and continuously pouring the fresh concrete into the drilled hole, standing, and forming the cast-in-place pile after the concrete is condensed.

Example 4

The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area is different from the cast-in-place pile in the embodiment 1 in that:

the swelling agent in step S3 was the swelling agent prepared in preparation example 2.

Example 5

The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area is different from the cast-in-place pile in the embodiment 1 in that:

the swelling agent in step S3 was the swelling agent prepared in preparation example 3.

Example 6

The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area is different from the cast-in-place pile in the embodiment 1 in that:

the swelling agent in step S3 was the swelling agent prepared in preparation example 4.

Example 7

The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area is different from the cast-in-place pile in the embodiment 1 in that:

the swelling agent in step S3 was the swelling agent prepared in preparation example 5.

Example 8

The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area is different from the cast-in-place pile in the embodiment 1 in that:

the swelling agent in step S3 was the swelling agent prepared in preparation example 6.

Example 9

The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area is different from the cast-in-place pile in the embodiment 1 in that:

the swelling agent in step S3 was the swelling agent prepared in preparation example 7.

Examples 10 to 12

The components and proportions of the cast-in-place piles for reinforcing the bearing strength in the deep and miscellaneous fill areas in examples 10 to 12 are shown in Table 4 below.

TABLE 4 composition and ratio (unit/kg) of cast-in-place pile in examples 10-12

The cast-in-place piles for reinforcing the bearing strength in the deep and miscellaneous fill areas in the examples 10 to 12 are different from the cast-in-place piles in the example 1 in that:

step S3, preparing concrete: weighing cement, fly ash, crushed stone, river sand, the expanding agent, the stabilizing agent, the water reducing agent, the air entraining agent and water prepared in the preparation example 1 according to the mixture ratio in the table 4; dissolving a stabilizer and a water reducing agent air entraining agent in water to form an additive solution; uniformly mixing cement and fly ash according to a ratio to form a gelled mixture; uniformly mixing broken stone and river sand according to a ratio to form an aggregate mixture; the gelled mixture, the aggregate mixture, the expanding agent prepared in preparation example 1 and the admixture solution were uniformly stirred to obtain fresh concrete.

Example 13

The difference between the cast-in-place pile for enhancing the bearing strength in the deep and thick miscellaneous fill area and the example 10 is that:

the air entraining agent is replaced by triterpenoid saponin with the same amount.

Example 14

The difference between the cast-in-place pile for enhancing the bearing strength in the deep and thick miscellaneous fill area and the example 10 is that:

the air entraining agent is replaced by the same amount of sodium abietate.

Example 15

The difference between the cast-in-place pile for enhancing the bearing strength in the deep and thick miscellaneous fill area and the example 10 is that:

the air entraining agent is replaced by the same amount of sodium fatty alcohol-polyoxyethylene ether sulfonate.

Comparative example

Comparative example 1

The difference from example 1 is that:

no swelling agent was added.

Comparative example 2

The difference from example 1 is that:

no stabilizer was added.

Comparative example 3

The difference from example 1 is that:

no bulking agent and stabilizing agent were added.

Performance test

Sample preparation:

concrete samples with the same shape and size are prepared according to the methods for preparing concrete in the above examples 1 to 15 and comparative examples 1 to 3, and after the samples are placed in the same environment and cured for 28d, the electric flux method in GB/T50082-2009 test method Standard for Long-term Performance and durability of ordinary concrete is used for detecting the samples, and the sulfate penetration resistance of the samples is detected according to the sulfate erosion resistance test in GB/T50082-2009 test method Standard for Long-term Performance and durability of ordinary concrete, and specific results are shown in Table 5 below.

TABLE 5 data for performance measurements of samples from examples 1-15 and comparative examples 1-3

Test specimen

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Electric flux/C

132

123

127

129

138

202

Sulfate resistance grade

KS150

KS150

KS150

KS150

KS150

KS120

Test specimen

Example 7

Example 8

Example 9

Example 10

Example 11

Example 12

Electric flux/C

226

267

169

88

85

91

Sulfate resistance grade

KS120

KS120

KS120

KS150

KS150

KS150

Test specimen

Example 13

Example 14

Example 15

Comparative example 1

Comparative example 2

Comparative example 3

Electric flux/C

108

105

111

332

529

543

Sulfate resistance grade

KS150

KS150

KS150

KS60

KS60

KS60

According to the data in table 5 in combination with the data in examples 1 and comparative examples 1-3, the electric flux of the sample is greatly reduced and the sulfate resistance rating is greatly improved when the swelling agent and the stabilizer are used together, which indicates that the swelling agent and the stabilizer have a synergistic effect and can enhance the chloride ion permeation resistance and the sulfate permeation resistance of the sample.

It can be seen from examples 1 to 5 and examples 6 to 9 in combination with the data in Table 5 that the low-speed ball milling and then the high-speed ball milling of the premixture of calcium oxide, calcium carbonate and fine silica powder are preferred in the preparation of the swelling agent, because the swelling agent thus prepared has better synergistic effect with the stabilizer in use, thereby enhancing the chloride ion permeation resistance and the sulfate permeation resistance of the sample.

From example 1 and examples 10-12 in combination with the data in Table 5, it can be seen that the addition of an air entraining agent can reduce the electric flux, indicating that the addition of an air entraining agent can further improve the chloride ion permeation resistance of the sample.

From example 10 and examples 13 to 15 in combination with the data in table 5, it can be seen that the electric flux can be further reduced when the air-entraining agent is a combination of triterpenoid saponin and sucrose, which indicates that the chlorine ion permeation resistance of the sample can be further improved when the air-entraining agent is a combination of triterpenoid saponin and sucrose.

The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.

Claims (10)

1. Strengthen bored concrete pile of dark thick miscellaneous fill area bearing strength, its characterized in that: the feed is prepared from the following raw materials in parts by weight:

cement: 355-365 parts

Fly ash: 150 portions to 160 portions

Crushing stone: 1240 and 1250 parts

River sand: 620 portion and 625 portion

Swelling agent: 12 to 16 portions of

A stabilizer: 6 to 8 portions of

Water reducing agent: 4.2 to 4.8 portions of

Water: 175 part by weight and 185 parts by weight

The expanding agent comprises calcium oxide, calcium carbonate and silicon micropowder, wherein the weight ratio of the calcium oxide to the calcium carbonate to the silicon micropowder is

（24-26）：（12-13）：（6-6.5）。

2. The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area according to claim 1, wherein: the stabilizer comprises sodium gluconate and polyisobutylene succinimide, and the weight ratio of the sodium gluconate to the polyisobutylene succinimide is (5-6): (1-2).

3. The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area according to claim 1, wherein: the preparation method of the expanding agent comprises the following steps:

step 1, preparing calcium oxide, calcium carbonate and silicon micropowder according to a ratio and uniformly mixing to obtain a premix;

step 2, sending the pre-mixture into a ball mill for ball milling for 2-3h at the ball milling speed of 450-;

and 3, drying and crushing the intermediate mixture to obtain the expanding agent with the particle size of less than or equal to 100 microns.

4. The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area according to claim 1, wherein: the water reducing agent comprises a polycarboxylate water reducing agent and a lignosulfonate water reducing agent in a weight ratio of (1.0-1.2) to 1.

5. The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area according to claim 1, wherein: the feed also comprises the following raw materials in parts by weight:

air entraining agent: 0.7 to 0.9 portion.

6. The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area according to claim 5, wherein: the air entraining agent comprises (6-8) by weight: 1 and sucrose.

7. The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area according to claim 1, wherein: the cement is P.II42.5R portland cement.

8. The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area according to claim 1, wherein: the fly ash is I-grade fly ash.

9. The cast-in-place pile for enhancing the bearing strength of the deep and thick miscellaneous fill area according to claim 1, wherein: the broken stone is 5-15mm in continuous gradation.

10. The construction method of the cast-in-place pile for enhancing the bearing strength in the deep and thick miscellaneous fill area is characterized by comprising the following steps of: a cast-in-place pile for enhancing bearing strength in deep and miscellaneous fill areas according to any of the preceding claims 1 to 9, comprising the steps of:

step S1, drilling: checking whether the formed hole has deflection phenomenon at any time in the drilling process, and correcting in time;

step S2, lowering a reinforcement cage: the reinforcement cage is coaxial with the central shaft of the drill hole;

step S3, preparing concrete: dissolving a stabilizer and a water reducing agent in water according to a ratio to form an additive solution; uniformly mixing cement and fly ash according to a ratio to form a gelled mixture; uniformly mixing broken stone and river sand according to a ratio to form an aggregate mixture; uniformly stirring the gelled mixture, the aggregate mixture, the expanding agent and the additive solution to obtain fresh concrete;

step S4, pouring concrete: and continuously pouring the fresh concrete into the drilled hole, standing, and forming the cast-in-place pile after the concrete is condensed.