A method for forming a cured soil cast-in-place pile for deep collapsible loess

Abstract

The application belongs to the technical field of civil engineering, and discloses a curing soil perfusion core-adding pile forming method for deep thick collapsible loess. The pile forming method comprises the following steps: 1) drilling and taking soil of the deep thick collapsible loess foundation to form a pile hole and obtain collapsible loess; 2) sequentially mixing the collapsible loess with water, curing material, dispersing agent and reinforcing agent to obtain a flowable curing soil; and 3) inserting a prefabricated reinforced concrete core pile into the pile hole and keeping it vertical, and then perfusing the flowable curing soil into the pile hole to form a curing soil perfusion core-adding pile. The application takes the deep thick collapsible loess in situ, prepares the collapsible loess into flowable curing soil meeting the flowability requirement, and then adopts the core-adding pile forming process of “inserting core first and then perfusing”, to form a composite foundation meeting the foundation bearing capacity, and the application has important popularization value in the northwest region.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering, and in particular relates to a method for forming solidified soil grouting and core piles for thick collapsible loess. Background Art

[0002] Collapsible loess, under the stress of the overlying soil's deadweight, or the combined effects of deadweight and additional stress, undergoes significant additional deformation after being flooded. Therefore, collapsible loess is generally unsuitable for use as a natural foundation and requires foundation treatment. Cast-in-place concrete piles are one approach to collapsible loess foundation treatment, but due to geographical limitations, construction costs are high and uneconomical. Utilizing loess's own materials to form a composite foundation that meets the foundation's bearing capacity is a hot topic in collapsible loess foundation treatment.

[0003] For deep, collapsible loess foundations, the poor water stability of collapsible loess makes it difficult to form a stable bearing layer at the pile end. The rigidity of the solidified soil cast-in-place piles is low, limiting the treatment depth. Combining fluidized solidified soil cast-in-place piles with precast reinforced concrete core piles to form a cored pile composite foundation can enhance the rigidity of the piles themselves and significantly increase the treatment depth. If this can be achieved, it would have significant promotional value in the treatment of deep, collapsible loess foundations in Northwest China. However, the technical difficulties include two aspects: 1) the lack of a method for preparing fluidized solidified soil for collapsible loess, and 2) the lack of a method for constructing cored piles based on fluidized solidified soil.

[0004] Patent CN114804767A discloses a premixed fluid filling material of easily weathered rock aggregate, which is composed of a mixture of aggregates consisting of easily weathered rock, bentonite, and collapsible loess, a curing agent, an admixture, and water; Patent CN113636809A discloses a collapsible loess aggregate filling material, which is composed of a mixture of aggregate, a curing agent, an admixture, and water, wherein the aggregate contains raw materials such as collapsible loess and red sandstone; the above patents improve the particle distribution of the collapsible loess by adding coarse and fine aggregates to the collapsible loess, and then form the filling material with a curing agent and water. The fluidity requirement is low and the self-compacting requirement of cast-in-place piles cannot be met.

[0005] Patent CN110258542B discloses a soft soil foundation reinforcement method based on cement concrete core piles. Before the cement soil mixing piles are formed and solidified, prefabricated reinforced concrete core piles are inserted into the cement piles to form cement soil core mixing piles. This pile-forming method is an improvement on the traditional mixing piles, but in the process of inserting the core piles into the cement soil piles, the cement soil and the surrounding soil will be squeezed and disturbed, which not only wastes cement, but also reduces or even destroys the pile quality of the cement soil itself.

[0006] Therefore, there is no method for preparing fluidized solidified soil for collapsible loess without adding coarse and fine aggregates, nor is there a method for forming core piles based on fluidized solidified soil. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to address the deficiencies in the existing technology and provide a method for forming solidified soil grouting and cored piles for deep collapsible loess. Soil is taken in situ from the deep collapsible loess and prepared into fluidized solidified soil that meets the fluidity requirements. A cored pile forming process of "first inserting the core and then grouting" is then adopted to form a composite foundation that meets the bearing capacity of the foundation. The method has important promotion value in the northwest region.

[0008] To solve the technical problem raised by the present invention, the present invention provides a method for forming solidified soil grouting and core piles for deep collapsible loess, comprising the following steps:

[0009] 1) Drilling and taking soil from the deep collapsible loess foundation to form pile holes and obtain collapsible loess;

[0010] 2) mixing the collapsible loess and water for a first stirring, adding a solidifying material for a second stirring, adjusting the pH, adding a dispersant for a third stirring, and finally adding a reinforcing agent for a fourth stirring to obtain fluidized solidified soil;

[0011] 3) Insert the prefabricated reinforced concrete core pile into the pile hole and keep it vertical, then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

[0012] In the above solution, the particle size of the collapsible loess is less than 2 cm.

[0013] In the above solution, the water-cement ratio of the fluidized solidified soil is 0.65-0.9.

[0014] In the above scheme, the amount of water used is determined according to the water-cement ratio, and the amount of water used when adjusting the water-cement ratio includes the water introduced into the collapsible loess.

[0015] In the above solution, the solidifying material is composed of the following raw materials in percentage by mass: 30-40% cement, 50-60% S95 granulated blast furnace slag, 3-8% fly ash, and 3-8% industrial by-product gypsum.

[0016] Preferably, the industrial by-product gypsum is desulfurized gypsum or phosphogypsum.

[0017] In the above solution, the amount of the solidifying material is 14-25% of the mass of the collapsible loess.

[0018] In the above scheme, the dispersant is added after adjusting the pH to 6.8-7.2 in step 2).

[0019] In the above solution, the dispersant is one or a combination of sodium hexametaphosphate and sodium polyacrylate.

[0020] Preferably, when the powder content of the collapsible loess is less than 60%, the dispersant is sodium hexametaphosphate.

[0021] Preferably, when the powder content of the collapsible loess is ≥60%, the dispersant is a combination of sodium hexametaphosphate and sodium polyacrylate, with the mass proportion of sodium hexametaphosphate being 30-40% and the mass proportion of sodium polyacrylate being 60-70%.

[0022] In the above scheme, the dosage of the dispersant is 0.5-1.5‰ of the mass of the collapsible loess.

[0023] In the above solution, the reinforcing agent is acrylate.

[0024] In the above solution, the dosage of the reinforcing agent is 1-5% of the mass of the collapsible loess.

[0025] In the above scheme, the stirring rate of the first stirring is 30-60 r / min, and the stirring time is 10-15 min.

[0026] In the above scheme, the stirring rate of the second stirring is 30-60 r / min, and the stirring time is 10-15 min.

[0027] In the above scheme, the stirring rate of the third stirring is 80-120 r / min, and the stirring time is 5-10 min.

[0028] In the above scheme, the stirring rate of the fourth stirring is 30-60 r / min, and the stirring time is 15-20 min.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The present invention uses in-situ collapsible loess as the main material. In view of the characteristics of collapsible loess with a large porosity and strong collapsibility, it is equipped with a curing material, a dispersant and a reinforcing agent to realize the production of fluidized solidified soil under medium and low speed stirring conditions, thereby solving the problem of waste soil recycling of collapsible loess in the northwest region. Compared with the traditional fluidized solidified soil production process, there is no need to improve the particle distribution of the in-situ collapsible loess to make the fluidity of the solidified soil meet the requirements of pourable self-compacting. By adjusting the dispersant according to the content of clay particles in the collapsible loess, the configuration of the fluidized solidified soil is more flexible, and the controllable range of the project cost is larger.

[0031] 2) The present invention adopts the "first core insertion and then pouring" core pile forming process. Compared with the traditional "first mixing and then core insertion" pile forming process, since the fluidized solidified soil pile body is not disturbed and damaged by the "core insertion" process, the quality of the formed pile body is more stable, and the soil between the piles will not be affected by the soil squeezing effect caused by the pile construction. The composite foundation can better exert its bearing capacity; at the same time, the "first core insertion and then pouring" core pile forming process has no special requirements for the cross-sectional shape of the core pile. Therefore, prefabricated reinforced concrete core piles with specific cross-sectional shapes can be customized according to project needs to improve the bearing capacity of the core pile, which can better adapt to the foundation treatment of collapsible loess. DETAILED DESCRIPTION

[0032] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0033] In the following examples, slump is used to reflect the fluidity and pourability of fluidized solidified soil. The determination method is as follows: a trumpet-shaped slump bucket with an upper opening of 100 mm, a lower opening of 200 mm, and a height of 300 mm is used to pour the fluidized solidified soil into the soil. After compaction, the soil is smoothed and then the bucket is pulled up. The fluidized solidified soil collapses due to its own weight. The slump is calculated by subtracting the height of the highest point of the fluidized solidified soil after collapse from the height of the bucket.

[0034] In the following examples, the unconfined compressive strength is used to represent the curing strength of the fluidized solidified soil. The determination method is as follows: a cubic test mold with dimensions of 70.5 mm × 70.5 mm × 70.5 mm is selected, the test mold is poured with the fluidized solidified soil, the mold is demolded after 48 hours, and the test piece is placed in a standard curing room with a temperature of 20±2°C and a relative humidity of >95% for curing for 7 days, 14 days, 28 days, and 60 days. The compressive strength of the test piece is then tested using an unconfined uniaxial press.

[0035] Example 1

[0036] A method for forming solidified soil grouting and cored piles for thick collapsible loess comprises the following steps:

[0037] 1) Drilling and sampling soil from a deep collapsible loess foundation to form a pile hole with a length of 15 m and a diameter of 500 mm, and retaining collapsible loess with a particle size of less than 2 cm; testing revealed that the silt content of the collapsible loess was 62%;

[0038] 2) Mix collapsible loess and water and stir at a rate of 30 r / min for 15 minutes; add a solidifying material at a rate of 20% by weight of the collapsible loess and stir at a rate of 30 r / min for 10 minutes; adjust the pH to 6.8 with sodium hydroxide and sodium bicarbonate, add a dispersant at a rate of 1‰ by weight of the collapsible loess and stir at a rate of 80 r / min for 6 minutes; finally, add an acrylic acid ester at a rate of 2% by weight of the collapsible loess and stir at a rate of 30 r / min for 15 minutes to obtain a fluidized solidified soil with a water-cement ratio of 0.7;

[0039] In the above steps, the curing material is composed of the following raw materials in percentage by mass: 30% of ordinary Portland cement, 50% of S95 granulated blast furnace slag, 4% of fly ash, and 3% of phosphogypsum; the dispersant is composed of the following raw materials in percentage by mass: 30% of sodium hexametaphosphate and 70% of sodium polyacrylate;

[0040] 3) Insert a prefabricated reinforced concrete core pile with a length of 15m, a diameter of 200mm and a circular cross-section into the pile hole and keep it vertical, then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

[0041] Example 2

[0042] A method for forming solidified soil grouting and cored piles for thick collapsible loess comprises the following steps:

[0043] 1) Drilling and collecting soil from a deep collapsible loess foundation to form a pile hole with a length of 14 m and a diameter of 500 mm, and retaining collapsible loess with a particle size of less than 2 cm; testing showed that the silt content of the collapsible loess was 65%;

[0044] 2) Mix collapsible loess and water and stir at a rate of 40 r / min for 13 minutes; add a solidifying material at a rate of 21% by weight of the collapsible loess and stir at a rate of 40 r / min for 12 minutes; adjust the pH to 6.8 with sodium hydroxide and sodium bicarbonate, add a dispersant at a rate of 1‰ by weight of the collapsible loess and stir at a rate of 90 r / min for 7 minutes; finally, add an acrylic acid ester at a rate of 3% by weight of the collapsible loess and stir at a rate of 40 r / min for 16 minutes to obtain a fluidized solidified soil with a water-cement ratio of 0.75;

[0045] In the above steps, the curing material is composed of the following raw materials in percentage by weight: 34% of ordinary Portland cement, 53% of S95 granulated blast furnace slag, 6% of fly ash, and 5% of phosphogypsum; the dispersant is composed of the following raw materials in percentage by weight: 35% of sodium hexametaphosphate and 65% of sodium polyacrylate;

[0046] 3) Insert a prefabricated reinforced concrete core pile with a length of 14m, a side length of 150mm and a square cross-section into the pile hole and keep it vertical. Then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

[0047] Example 3

[0048] A method for forming solidified soil grouting and cored piles for thick collapsible loess comprises the following steps:

[0049] 1) Drilling and collecting soil from a deep collapsible loess foundation to form a pile hole with a length of 16 m and a diameter of 500 mm, and retaining collapsible loess with a particle size of less than 2 cm; testing showed that the silt content of the collapsible loess was 63%;

[0050] 2) Mix collapsible loess and water and stir at a rate of 50 r / min for 10 minutes; add a solidifying material at a rate of 25% by weight of the collapsible loess and stir at a rate of 50 r / min for 11 minutes; adjust the pH to 6.8 with sodium hydroxide and sodium bicarbonate, add a dispersant at a rate of 1‰ by weight of the collapsible loess and stir at a rate of 100 r / min for 8 minutes; finally, add acrylic acid at a rate of 4% by weight of the collapsible loess and stir at a rate of 50 r / min for 18 minutes to obtain a fluidized solidified soil with a water-cement ratio of 0.73;

[0051] In the above steps, the curing material is composed of the following raw materials in percentage by weight: 36% of ordinary Portland cement, 56% of S95 granulated blast furnace slag, 8% of fly ash, and 8% of phosphogypsum; the dispersant is composed of the following raw materials in percentage by weight: 33% of sodium hexametaphosphate and 67% of sodium polyacrylate;

[0052] 3) Insert a tubular prefabricated reinforced concrete core pile with a length of 16m, an outer diameter of 300mm, and an inner diameter of 150mm into the pile hole and keep it vertical. Then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

[0053] Example 4

[0054] A method for forming solidified soil grouting and cored piles for thick collapsible loess comprises the following steps:

[0055] 1) Drilling and sampling soil from a deep collapsible loess foundation to form a pile hole with a length of 15 m and a diameter of 500 mm, and retaining collapsible loess with a particle size of less than 2 cm; testing revealed that the silt content of the collapsible loess was 58%;

[0056] 2) Mix collapsible loess and water and stir at a rate of 50 r / min for 11 minutes; add a solidifying material at a rate of 15% by weight of the collapsible loess and stir at a rate of 50 r / min for 14 minutes; adjust the pH to 7 with sodium hydroxide and sodium bicarbonate, add a dispersant at a rate of 0.6‰ by weight of the collapsible loess and stir at a rate of 80 r / min for 9 minutes; finally, add an acrylic acid ester at a rate of 1% by weight of the collapsible loess and stir at a rate of 50 r / min for 19 minutes to obtain a fluidized solidified soil with a water-cement ratio of 0.68;

[0057] In the above steps, the curing material is composed of the following raw materials in percentage by mass: 35% of ordinary Portland cement, 55% of S95 granulated blast furnace slag, 5% of fly ash, and 5% of phosphogypsum; the dispersant is sodium hexametaphosphate;

[0058] 3) Insert a prefabricated reinforced concrete core pile with a length of 15m, a diameter of 200mm and a circular cross-section into the pile hole and keep it vertical, then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

[0059] Example 5

[0060] A method for forming solidified soil grouting and cored piles for thick collapsible loess comprises the following steps:

[0061] 1) Drilling and sampling soil from a deep collapsible loess foundation to form a pile hole with a length of 14 m and a diameter of 500 mm, and retaining collapsible loess with a particle size of less than 2 cm; testing revealed that the silt content of the collapsible loess was 56%;

[0062] 2) Mix collapsible loess and water and stir at a rate of 60 r / min for 10 minutes; add a solidifying material at a rate of 18% by weight of the collapsible loess and stir at a rate of 60 r / min for 13 minutes; adjust the pH to 7.1 with sodium hydroxide and sodium bicarbonate, add a dispersant at a rate of 0.8‰ by weight of the collapsible loess and stir at a rate of 100 r / min for 5 minutes; finally, add an acrylic acid ester at a rate of 3% by weight of the collapsible loess and stir at a rate of 60 r / min for 18 minutes to obtain a fluidized solidified soil with a water-cement ratio of 0.78;

[0063] In the above steps, the curing material is composed of the following raw materials in percentage by mass: 38% of ordinary Portland cement, 58% of S95 granulated blast furnace slag, 8% of fly ash, and 8% of phosphogypsum; the dispersant is sodium hexametaphosphate;

[0064] 3) Insert a prefabricated reinforced concrete core pile with a length of 14m, a side length of 150mm and a square cross-section into the pile hole and keep it vertical. Then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

[0065] Example 6

[0066] A method for forming solidified soil grouting and cored piles for thick collapsible loess comprises the following steps:

[0067] 1) Drilling and sampling soil from a deep collapsible loess foundation to form a pile hole with a length of 16 m and a diameter of 500 mm, and retaining collapsible loess with a particle size of less than 2 cm; testing revealed that the silt content of the collapsible loess was 72%;

[0068] 2) Mix collapsible loess and water and stir at a rate of 60 r / min for 12 minutes; add a solidifying material at a rate of 20% by weight of the collapsible loess and stir at a rate of 60 r / min for 11 minutes; adjust the pH to 7.2 with sodium hydroxide and sodium bicarbonate, add a dispersant at a rate of 1.2‰ by weight of the collapsible loess and stir at a rate of 90 r / min for 6 minutes; finally, add acrylic acid at a rate of 4% by weight of the collapsible loess and stir at a rate of 60 r / min for 20 minutes to obtain a fluidized solidified soil with a water-cement ratio of 0.8;

[0069] In the above steps, the curing material is composed of the following raw materials in percentage by weight: 38% of ordinary Portland cement, 55% of S95 granulated blast furnace slag, 5% of fly ash, and 8% of phosphogypsum; the dispersant is composed of the following raw materials in percentage by weight: 32% of sodium hexametaphosphate and 68% of sodium polyacrylate;

[0070] 3) Insert a tubular prefabricated reinforced concrete core pile with a length of 16m, an outer diameter of 300mm, and an inner diameter of 150mm into the pile hole and keep it vertical. Then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

[0071] Example 7

[0072] A method for forming solidified soil grouting and cored piles for thick collapsible loess comprises the following steps:

[0073] 1) Drilling and sampling soil from a deep collapsible loess foundation to form a pile hole with a length of 15 m and a diameter of 500 mm, and retaining collapsible loess with a particle size of less than 2 cm; testing showed that the silt content of the collapsible loess was 70%;

[0074] 2) Mix collapsible loess and water and stir at a rate of 50 r / min for 15 minutes; add a solidifying material at a rate of 22% by weight of the collapsible loess and stir at a rate of 50 r / min for 15 minutes; adjust the pH to 6.9 with sodium hydroxide and sodium bicarbonate, add a dispersant at a rate of 1.5‰ by weight of the collapsible loess and stir at a rate of 110 r / min for 10 minutes; finally, add acrylic acid at a rate of 5% by weight of the collapsible loess and stir at a rate of 50 r / min for 17 minutes to obtain a fluidized solidified soil with a water-cement ratio of 0.82;

[0075] In the above steps, the curing material is composed of the following raw materials in mass percentage: 35% of ordinary Portland cement, 58% of S95 granulated blast furnace slag, 8% of fly ash, and 5% of phosphogypsum; the dispersant is composed of the following raw materials in mass percentage: 40% of sodium hexametaphosphate and 60% of sodium polyacrylate;

[0076] 3) Insert a prefabricated reinforced concrete core pile with a length of 15m, a diameter of 200mm and a circular cross-section into the pile hole and keep it vertical, then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

[0077] Comparative Example 1

[0078] A conventional cement-soil core mixing pile forming method comprises the following steps:

[0079] 1) Use 425# ordinary Portland cement to mix cement slurry with a water-cement ratio of 0.45-0.5;

[0080] 2) Use a pile mixer to drill and mix the deep, collapsible loess foundation. The mixing head is lowered while mixing the soil. After sinking to a depth of 15m, cement slurry is delivered to the mixing head outlet. The mixing head is lifted while spraying and mixing to ensure that the slurry and soil are fully mixed.

[0081] 3) Insert a prefabricated reinforced concrete core pile with a length of 15m, a diameter of 200mm and a circular cross-section into the pile hole and keep it vertical to form a cement-soil core mixing pile.

[0082] Comparative Example 2

[0083] A conventional cement-soil core mixing pile forming method comprises the following steps:

[0084] 1) Use 425# ordinary Portland cement to mix cement slurry with a water-cement ratio of 0.45-0.5;

[0085] 2) A mixing pile driver is used to drill and mix the deep, collapsible loess foundation. The mixing head is lowered while mixing the soil. After sinking to a depth of 14m, cement slurry is delivered to the mixing head outlet. The mixing head is lifted while spraying and mixing to ensure that the slurry and soil are fully mixed.

[0086] 3) Insert a prefabricated reinforced concrete core pile with a length of 14m, a side length of 150mm and a square cross-section into the pile hole and keep it vertical to form a cement-soil core mixing pile.

[0087] Comparative Example 3

[0088] A conventional cement-soil core mixing pile forming method comprises the following steps:

[0089] 1) Use 425# ordinary Portland cement to mix cement slurry with a water-cement ratio of 0.45-0.5;

[0090] 2) A mixing pile driver is used to drill and mix the deep, collapsible loess foundation. The mixing head is lowered while mixing the soil. After sinking to a depth of 16m, cement slurry is delivered to the slurry outlet of the mixing head. The mixing head is lifted while spraying and mixing to ensure that the slurry and soil are fully mixed.

[0091] 3) Insert a tubular prefabricated reinforced concrete core pile with a length of 16m, an outer diameter of 300mm, and an inner diameter of 150mm into the pile hole and keep it vertical to form a cement-soil core mixing pile.

[0092] The slump and 28d unconfined compressive strength of the fluidized solidified soil prepared in Examples 1-7 were tested, the single pile bearing capacity, composite foundation bearing capacity, collapsible elimination degree, and pile body integrity tests of the solidified soil cast-in-place core piles naturally cured for 28 days in Examples 1-3 were performed, and the unconfined compressive strength, single pile bearing capacity, composite foundation bearing capacity, collapsible elimination degree, and pile body integrity tests of the traditional cement-soil cored mixing piles naturally cured for 28 days in Comparative Examples 1-3 were performed. The results are shown in Table 1.

[0093] The test method for the bearing capacity of a single pile is the static load test of the single pile; the test method for the bearing capacity of a composite foundation is the flat plate load test; the test method for the elimination of wetting resistance is the immersion method; the test method for the integrity of the pile body is coring through drilling and characterization using QRD.

[0094] Table 1

[0095]

[0096] As can be seen from Table 1, the 28d unconfined compressive strength of the fluidized solidified soil prepared in Examples 1-7 reaches about 6 MPa, which is twice the solidification strength of general cement soil; the slump reaches about 240 mm, which meets the pourability requirements and perfectly solves the contradiction between fluidity and strength of the solidified soil.

[0097] It can also be seen from Table 1 that the solidified soil cast-in-place core piles formed in Examples 1-7 have a single pile bearing capacity and a composite foundation bearing capacity that are about 30% higher than those of conventional cement-soil cored mixing piles under the same conditions. The method of inserting the core first and then casting the core reduces the disturbance of the solidified soil and the soil around the pile by the post-insertion process, making the pile body more complete, and the RQD value reaches above 97%, which is much better than conventional cement-soil cored mixing piles.

[0098] The above embodiments are merely examples for clarification and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications may be made based on the above descriptions. It is not necessary and impossible to enumerate all implementation methods here, and any obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for forming solidified soil grouting and core piles for deep collapsible loess, characterized in that: The following steps are involved: 1) Drilling and taking soil from the deep collapsible loess foundation to form pile holes and obtain collapsible loess; 2) Mixing collapsible loess and water for a first stirring, adding a solidifying material for a second stirring, adjusting the pH to 6.8-7.2, adding a dispersant for a third stirring, and finally adding a reinforcing agent for a fourth stirring to obtain fluidized solidified soil; wherein the solidifying material is composed of the following raw materials in percentage by mass: 30-40% cement, 50-60% S95 granulated blast furnace slag, 3-8% fly ash, and 3-8% industrial by-product gypsum; the amount of the solidifying material is 14-25% of the mass of the collapsible loess; the dispersant is one or a combination of sodium hexametaphosphate and sodium polyacrylate, the amount of the dispersant is 0.5-1.5‰ of the mass of the collapsible loess; the reinforcing agent is acrylate, the amount of the reinforcing agent is 1-5% of the mass of the collapsible loess; and the water-cement ratio of the fluidized solidified soil is 0.65-0.9; 3) Insert the prefabricated reinforced concrete core pile into the pile hole and keep it vertical, then pour fluidized solidified soil into the pile hole to form a solidified soil poured core pile.

2. The method for forming solidified soil grouting and cored piles for deep collapsible loess according to claim 1, characterized in that: The particle size of the collapsible loess is less than 2 cm.

3. The method for forming solidified soil grouting and cored piles for deep collapsible loess according to claim 1, characterized in that: When the powder content of the collapsible loess is less than 60%, the dispersant is sodium hexametaphosphate; when the powder content of the collapsible loess is ≥60%, the dispersant is a combination of sodium hexametaphosphate and sodium polyacrylate, with the mass proportion of sodium hexametaphosphate being 30-40% and the mass proportion of sodium polyacrylate being 60-70%.

4. The method for forming solidified soil grouting and cored piles for deep collapsible loess according to claim 1, characterized in that: The stirring rate of the first stirring is 30-60 r / min, and the stirring time is 10-15 min; the stirring rate of the second stirring is 30-60 r / min, and the stirring time is 10-15 min; the stirring rate of the third stirring is 80-120 r / min, and the stirring time is 5-10 min; the stirring rate of the fourth stirring is 30-60 r / min, and the stirring time is 15-20 min.

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