A cement mixing pile construction process

Abstract

The invention discloses a cement-soil mixing pile construction process, aiming to provide a cement-soil mixing pile with good corrosion resistance, stability, strength and durable impermeability, and ensure its stability and safety under complex soil conditions; the technical scheme is as follows: mainly comprising the following steps: measuring and setting out, determining pile positions; positioning and leveling a drilling rig; preparing cement slurry with a water-cement ratio of 1:0.50-0.6; drilling, stirring and spraying a drill rod by sinking a drill rod; lifting the drill rod, spraying and stirring; repeating steps (4) and (5); cleaning a nozzle and moving the machine; wherein the cement used in preparing the cement slurry comprises the following components by weight: 1000 parts of ordinary silicate cement, 100-200 parts of fly ash, 15-25 parts of modified basalt fiber, 3-10 parts of a retarder, and 4-12 parts of a water reducer, and relates to the technical field of building construction.

Description

Technical Field

[0001] The present application relates to the technical field of building construction, and in particular to a cement-soil mixing pile construction process. Background Art

[0002] Cement-soil mixing piles are a type of pile that uses cement as the main curing agent. Cement is sprayed into the soil using a mixing pile machine and fully mixed, so that a series of physical and chemical reactions occur between the cement and the soil to form a cement-soil reinforcement with a certain integrity and strength; thereby increasing the bearing capacity of the foundation and improving the deformation characteristics of the foundation. In addition, cement-soil mixing piles can also form a support structure for retaining soil during foundation pit excavation; they can also form an anti-seepage and water-stopping curtain to prevent groundwater infiltration.

[0003] Since cement-soil mixing piles are used as supporting, anti-seepage and water-stopping structures, the strength requirements for cement-soil mixing piles are relatively high in the cement-soil mixing pile construction process.

[0004] The existing cement-soil mixing pile construction process usually involves mixing cement and water to prepare cement slurry, and then using a pile-mixing machine to drill, spray cement slurry and mix it with soil to form a columnar solid, which is the cement-soil mixing pile. However, due to the complex composition of the underground in-situ soil and water, some sites have certain micro-corrosive or weakly corrosive soil and water; after a long period of weak corrosion, the durability, strength and stability of the cement-soil mixing pile are weakened, thereby reducing its reinforcement effect and even causing safety hazards.

[0005] In addition, in the process of cement-soil mixing pile construction technology, when the setting time is too short, premature initial setting will increase its viscosity and the mixing effect will be poor, and the curing agent and soil will not be fully mixed, thus affecting the strength of the pile; in addition, the soil is not easy to suspend during the mixing process, and the pile diameter is reduced, which in turn affects the bearing capacity of the pile; even hard lumps are formed, which affects the use of cement slurry and causes waste of raw materials. Therefore, it is necessary to ensure a suitable setting time.

[0006] Therefore, in order to ensure the durability and stability of cement-soil mixing piles, improve the strength and anti-seepage performance of the pile body, and ensure its stability and safety under complex soil conditions, we need to design a reasonable cement-soil mixing pile construction process, especially the study of cement slurry components and proportions is particularly important to reduce the occurrence of the above problems. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a cement-soil mixing pile construction process, which ensures that the final cement-soil mixing pile has good corrosion resistance, stability, strength and durable impermeability through research on cement slurry components and proportions, thereby ensuring its stability and safety under complex soil conditions.

[0008] To this end, the technical solution provided by the present invention is as follows:

[0009] A cement soil mixing pile construction process mainly comprises the following steps in sequence:

[0010] (1) Measurement, setting out and stake location;

[0011] (2) Drilling rig positioning and leveling;

[0012] (3) preparing cement slurry with a water-cement ratio of 1:0.50 to 0.6;

[0013] (4) Drilling, mixing and grouting by sinking the drill pipe;

[0014] (5) Drill rod lifting, grouting and mixing;

[0015] (6) Repeat steps (4) and (5)

[0016] (7) Clean the nozzle and move the machine;

[0017] The cement used in preparing cement slurry includes the following components by weight: 1000 parts of ordinary Portland cement, 100-200 parts of fly ash, 15-25 parts of modified basalt fiber, 3-10 parts of retarder, and 4-12 parts of water reducer. Furthermore, in the above-mentioned cement-soil mixing pile construction process, the ordinary Portland cement is 42.5R ordinary Portland cement. Furthermore, in the above-mentioned cement-soil mixing pile construction process, the water reducer is a polycarboxylic acid-based high-performance water reducer.

[0018] Furthermore, in the above-mentioned cement-soil mixing pile construction process, the cement consumption per meter of the mixing pile is not less than 75 kg, which is 18.0% of the wet soil bulk density.

[0019] Furthermore, in the above-mentioned cement soil mixing pile construction process, the modified basalt fiber is prepared by:

[0020] 1) Wash and dry the basalt fiber, then soak it in acetone for 3-5 hours, wash it again, and dry it;

[0021] 2) adding the modified solution of 5-6 times the mass of the basalt fiber to the treated basalt fiber in step 1) and mixing evenly, then reacting at room temperature for 3-6 hours, washing with anhydrous ethanol, and drying to obtain the result;

[0022] The modified solution is calculated based on a total mass of 100%, and the mass ratios of the various components are as follows: 2-4% N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane; 1-2% graphene, 2-5% nano zirconium oxide, and the remainder is ethanol.

[0023] Furthermore, in the above-mentioned cement soil mixing pile construction process, the retarder is a mixture of sulfomethylated sodium lignin sulfonate and calcium lignin sulfonate.

[0024] Furthermore, in the above-mentioned cement soil mixing pile construction process, the mass ratio of the methylated sodium lignin sulfonate to calcium lignin sulfonate is 1:0.8-1.2.

[0025] Furthermore, in the above-mentioned cement soil mixing pile construction process, the cement soil mixing pile adopts a four-mixing and four-spraying process.

[0026] Furthermore, in the above-mentioned cement soil mixing pile construction process, the lifting and sinking speed of the drill rod in step (4) and step (5) is 0.35m-0.50m / min.

[0027] Compared with the prior art, the cement-soil mixing pile construction process of the present invention has the following beneficial effects:

[0028] 1. The technical solution provided by the present invention adopts silicate cement, fly ash, modified basalt fiber, retarder, water reducer and water as cement slurry, which has fluidity and adhesion, and can form a denser structure, thereby effectively preventing the penetration of moisture and harmful substances, improving impermeability, crack resistance and corrosion resistance, thereby extending the service life of the pile body, improving the overall strength and durability of the pile body, and effectively improving the stability and durability of cement-soil mixing piles under complex soil conditions.

[0029] 2. The technical solution provided by the present invention adopts modified basalt fiber to have good tensile strength, high temperature resistance and corrosion resistance, and has excellent compatibility with other components, thereby improving the interface bonding between basalt fiber and cement-based materials: reducing the chance of penetration of corrosive media; enhancing chemical resistance, reducing the corrosion rate of cement-based materials in corrosive environments, extending their service life, and enhancing the mechanical properties of the material, thereby enhancing the tensile strength of the pile body, improving its crack resistance, and effectively preventing the generation of cracks in the pile body during use.

[0030] 3. The technical solution provided by the present invention adopts a mixture of sulfomethylated sodium lignin sulfonate and calcium lignin sulfonate as a retarder, and the compound polycarboxylic acid-based high-performance water reducer not only prolongs the initial and final setting time of the cement slurry, improves the fluidity of the cement slurry, and reduces the shrinkage rate of the cement slurry, thereby improving the durability and stability of the cement-soil mixing piles, while providing a more ample time window for construction and ensuring the construction quality.

[0031] 4. The technical solution provided by the present invention adopts a four-stirring and four-spraying process to ensure sufficient mixing of cement slurry and soil, so that the combination of the pile body and the surrounding soil body is tighter, and the bearing capacity of the pile body is improved; by optimizing the lifting and sinking speed of the drill rod, the vibration and noise during the construction process are reduced, while ensuring the continuity of construction and the uniformity of the pile body. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0033] First, the "Standard for Geotechnical Test Methods"〔GB / T50123-2019〕 carried out an evaluation of the corrosiveness of soluble salts on the in-situ soil and surveyed two groups of soluble salt test samples from the soil on site. The main indicators are as follows:

[0034] (1) Evaluation of the corrosiveness of groundwater

[0035] During this survey, two groups of water samples were collected from the boreholes on site, recorded as ZK24 and ZK493 groundwater. The main indicators are as follows:

[0036]

[0037] The construction site is classified as a Class A environment. Groundwater causes slight corrosion to the concrete structure and slight corrosion to the steel bars in the reinforced concrete structure.

[0038] (2) Evaluation of the corrosiveness of soluble salts in soil

[0039] Two groups of soluble salt test samples were taken from the site during this survey, recorded as Zk20-2 and Zk73-1. Their main indicators are as follows:

[0040]

[0041] According to the analysis of the soluble salt content in the soil, the soil on this site is weakly corrosive to the concrete structure and slightly corrosive to the steel bars in the concrete structure. In summary, the groundwater on the site is slightly corrosive to the concrete structure and slightly corrosive to the steel bars in the reinforced concrete structure, and the soil is weakly corrosive to the concrete structure and slightly corrosive to the steel bars in the reinforced concrete structure.

[0042] The invention provides a cement-soil mixing pile construction process, which comprises the following steps in sequence: site leveling → measurement and setting out → pile location → drilling rig positioning and leveling → cement slurry preparation → sinking drilling, mixing, and grouting → lifting, grouting, and stirring → repeated sinking, spraying, and stirring → repeated lifting, stirring, and spraying → cleaning the nozzle → moving the machine → carrying out the next mixing construction.

[0043] The details are as follows:

[0044] (1) Site leveling: Before construction, the site must be cleaned in accordance with construction technical specifications and obstacles on the ground and underground must be removed.

[0045] (2) Measurement and layout: The guide points and level points given in the design shall be reviewed with the client and the supervising engineer before construction and used only after confirmation.

[0046] (3) Determining pile positions: Surveyors carry out surveying and setting out work such as the mixing pile positions, original ground elevations, and hole elevations according to the construction design drawings.

[0047] (4) Positioning and leveling of drilling rig: The crane suspends the mixer to the designated pile position; when the ground is uneven, the lifting equipment should be kept level; align the mixer with the pile position and adjust the levelness of the machine.

[0048] (5) Preparation of cement slurry: Prepare a shotcrete tank and weigh the following components:

[0049] 250KG water, 500kg 42.5R ordinary Portland cement, 75kg fly ash, 10kg modified basalt fiber, 2.5kg sulfomethylated sodium lignin sulfonate and 2.5kg calcium lignin sulfonate, 8kg polycarboxylic acid high performance water reducer SPC-100.

[0050] The modified basalt fiber is prepared by:

[0051] 1) Wash the basalt fiber, dry it, soak it in acetone for 5 hours, wash it again, and dry it at 100°C for 3 hours;

[0052] 2) adding the modified solution of 5 times the mass of the basalt fiber to the treated basalt fiber in step 1) and mixing evenly, then reacting at room temperature for 5 hours, washing with anhydrous ethanol, and drying at 100° C. for 5 hours;

[0053] The modified solution is calculated based on a total mass of 100%, and the mass ratios of the components are as follows: 3% N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane; 2% graphene, 3% silicon dioxide, and the balance is ethanol.

[0054] Make good preparations before mixing; since cement slurry is used as a curing agent, the slurry should be sprayed in time after mixing to prevent slurry segregation.

[0055] (6) Drilling, mixing, and grouting: After the cooling water circulation of the mixer is normal, start the mixer motor, loosen the crane wire rope, and let the mixer sink along the guide frame to mix and cut the soil. The sinking speed can be controlled by the motor's current detection meter. The working current should not be greater than 70A. If the sinking speed is too slow, water can be supplied from the slurry delivery system to facilitate drilling. The mixer sinks and rotates while mixing, and the slurry pump is started to spray slurry, and drills to the designed pile bottom.

[0056] (7) Lifting, grouting and mixing: After the drill bit sinks to the designed depth, lift the mixing drill bit strictly according to the required lifting speed and grouting pressure, start the slurry pump at the same time, control the grouting pressure and increase the mixing speed, and spray while lifting to the designed pile top elevation; the slurry stopping surface during construction should be 500 mm higher than the designed elevation of the pile top, stir for a few seconds to ensure that the pile head is evenly compacted; wait for the pile top to press the beam, and then chisel off the excess part during construction.

[0057] (8) Repeated sinking and mixing: In order to fully mix the soil and cement slurry, sink the mixing drill again, start the mortar pump, and spray and mix to the designed concentration.

[0058] (9) Repeat the lifting and then lift the mixing drill bit again, for a total of four mixing and four spraying, until the slurry is mixed to the designed elevation.

[0059] (10) Cleaning: Pour an appropriate amount of clean water into the emptied aggregate hopper, open the mortar cleaning pipeline to remove the cement slurry remaining in the pipeline, and clean the mud attached to the mixing drill bit.

[0060] (11) Shifting: Repeat the above steps (1) to (10) to proceed with the construction of the next pile.

[0061] It should be noted that: Quality control of mixing pile construction process

[0062] 1) When the slurry is stopped for some reason during construction, the mixing head will be sunk to 500㎜ above the slurry stopping point, and then raised again when the slurry supply is restored.

[0063] 2) The interval between piles should not be greater than 12 hours. If the interval is too long and the quality of the overlap cannot be guaranteed, local pile reinforcement or grouting measures should be taken.

[0064] 3) During construction, the flow pump is used to control the slurry delivery speed and keep it constant. The sinking depth of the drill rod is controlled according to the machine table elevation and the designed pile length. The lifting speed of the last mixing should not exceed 0.50m per minute (in the sand layer position, the lifting and sinking speed during the construction process is required to be controlled to be no more than 0.35m per minute);

[0065] 4) If the slurry is stopped for some reason during construction, the mixer should be sunk to 0.50m below the slurry stopping point, and then the slurry can be sprayed and lifted when the slurry supply is restored;

[0066] 5) Mixing piles should be constructed continuously, and the interval between adjacent pile construction should not exceed 2 hours. The overlap time of pile rows should not exceed 24 hours. If it exceeds the specified time, the last pile to be overlapped should be drilled to leave a tenon for the next batch of piles to overlap. If overlap is not possible, additional piles should be added;

[0067] 6) The integrity and depth of the mixing piles shall be checked by the core drilling method. The number of water-stop curtain mixing piles to be sampled shall not be less than 1% of the total number of piles, and shall not be less than 6;

[0068] 5) The cement consumption per meter of the mixing pile shall not be less than 75 kg (about 18.0-20% of the wet soil bulk density), and the unconfined compressive strength of the cement soil in the pile body at 28 days shall not be less than 1.00 MPa;

[0069] 7) Keep good time records for each pile. The depth recording error should be less than 100㎜, and the time recording error should be less than 5S.

[0070] 8) Allowable deviation of mixing pile construction:

[0071] Pile verticality Pile position deviation Pile diameter deviation Pile top elevation Pile bottom elevation <0.5% pile length ≤30㎜ ≤4% pile diameter >Design elevation 30㎜ Should be 100-200mm deeper

[0072] Performance Testing

[0073] The cement-soil mixing piles provided in this embodiment are cured for 28, 60, and 90 days in the state according to GB / T17671-2021 "Test Method for Unconfined Compressive Strength of Cement" and JJG147-2016 "Test Procedure for Unconfined Compressive Strength of Cement". When each age is reached, a core drill is used to extract core samples, and unconfined compressive strength tests and core sample integrity evaluations are carried out, which is recorded as Example 1, and an equal amount of basalt fiber is added instead of modified basalt fiber, which is recorded as Comparative Example 1; an equal amount of methylated sodium lignin sulfonate is used instead of calcium lignin sulfonate, which is recorded as Comparative Example 2; an equal amount of calcium sulfonate is used instead of methylated sodium lignin sulfonate, which is recorded as Comparative Example 3. The test results are shown in Table 1.

[0074]

[0075]

[0076] It can be seen from Table 1 that the construction technology proposed in this application significantly improves the stability and compressive strength of the pile body.

[0077] The test results of Example 1 show that the unconfined compressive strength of the cement-soil mixing pile gradually increases with the extension of the curing time and reaches a peak value at 90 days. The evaluation of the pile integrity shows that the pile integrity of Example 1 exceeds 98%, which is higher than the pile integrity of Comparative Examples 1, 2, and 3, indicating that the mixing pile construction technology used in this example enhances the stability and compressive strength of the pile.

Claims

1. A cement soil mixing pile construction process, characterized in that: The steps are mainly as follows: (1) Measurement, setting out and stake location; (2) Drilling rig positioning and leveling; (3) preparing cement slurry with a water-cement ratio of 1:0.50 to 0.6; (4) Drilling, mixing and grouting by sinking the drill pipe; (5) Drill rod lifting, grouting and mixing; (6) Repeat steps (4) and (5) (7) Clean the nozzle and move the machine; The cement used in preparing cement slurry includes the following components by weight: 1000 parts of ordinary Portland cement, 100-200 parts of fly ash, 15-25 parts of modified basalt fiber, 3-10 parts of retarder, and 4-12 parts of water reducer.

2. The cement soil mixing pile construction process according to claim 1 is characterized in that: The ordinary Portland cement is 42.5R ordinary Portland cement.

3. The cement soil mixing pile construction process according to claim 1 is characterized in that: The water reducing agent is a polycarboxylic acid high performance water reducing agent.

4. The cement soil mixing pile construction process according to claim 1, characterized in that: According to claim 1 The cement-soil mixing pile construction process is characterized in that the cement consumption per meter of the mixing pile is not less than 75 kg, which is 18.0% of the wet soil bulk density.

5. The cement-soil mixing pile construction process according to claim 1, characterized in that: The modified basalt fiber is prepared by: 1) Wash and dry the basalt fiber, then soak it in acetone for 3-5 hours, wash it again, and dry it; 2) adding the modified solution of 5-6 times the mass of the basalt fiber to the treated basalt fiber in step 1) and mixing evenly, then reacting at room temperature for 3-6 hours, washing with anhydrous ethanol, and drying to obtain the result; The modified solution is calculated based on a total mass of 100%, and the mass ratios of the various components are as follows: 2-4% N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane; 1-2% graphene, 2-5% nano zirconium oxide, and the remainder is ethanol.

6. The cement-soil mixing pile construction process according to claim 1 is characterized in that: The retarder is a mixture of sulfomethylated sodium lignin sulfonate and calcium lignin sulfonate.

7. The cement-soil mixing pile construction process according to claim 6 is characterized in that: The mass ratio of the methylated sodium lignin sulfonate to calcium lignin sulfonate is 1:0.8-1.

2.

8. The cement-soil mixing pile construction process according to claim 1, characterized in that: Cement soil mixing piles adopt the four-mixing and four-spraying process.

9. The cement-soil mixing pile construction process according to claim 1, characterized in that: In step (4) and step (5), the lifting and sinking speed of the drill pipe is 0.35m-0.50m / min.

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