Construction method for improving forming quality of cement mixing pile
Through the pre-aggregation and freezing technology of comprehensive temperature monitoring and insulation heating combined with ultrasonic vibration and thermal control supply, the pre-setting and freezing of cement slurry in low-temperature or frozen soil environments is solved, and the high consistency and high-strength forming of cement mixing piles are achieved, improving construction quality and efficiency.
Patent Information
- Application Number
- CN202510893978.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-30
- Publication Date
- 2025-08-15
AI Technical Summary
In low-temperature or frozen soil environments, cement slurry is prone to preset or pipeline freeze due to low ambient temperature, resulting in poor fluidity of the slurry and uneven soil-slurry interface, and it is difficult to guarantee the strength and compactness of the pile body. The feedback mechanism for mild drilling resistance of soil in traditional construction is insufficient, resulting in unstable pile quality and reduced production efficiency.
The comprehensive temperature monitoring and insulation heating measures are adopted, combined with the pre-aggregation and rupture technology of ultrasonic vibration and thermal control supply, and the frozen depth and timing are automatically determined through real-time soil temperature and drilling resistance signals to ensure the fluidity and uniform ratio of the slurry, and closed-loop adjustment is performed in the spraying and lifting mixing process, combined with the online construction record and automatic cleaning mechanism, a closed-loop quality control of the construction process is formed.
It effectively prevents presetting and freezing of cement slurry in low-temperature environments, improves slurry fluidity and mixing uniformity, improves the freezing efficiency, ensures high consistency and high-strength molding of piles, and achieves high reliability construction in severe cold or frozen environments.
Smart Images
Figure CN120486370A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of cement mixing piles, in particular to a construction method for improving the molding quality of cement mixing piles. Background Art
[0002] Cement mixing pile forming is a commonly used foundation reinforcement technology. Cement slurry is injected into the ground and mixed with the original soil using a rotating mixer to form a high-strength soil-slurry composite pile body, which can improve the bearing capacity of the foundation and control settlement. Under normal temperature conditions, this process is relatively mature: cement slurry with a fixed water-cement ratio is usually used to form the pile body through spray drilling and lifting mixing cycles; However, in low-temperature or frozen soil environments, cement slurry is prone to pre-setting or pipe freezing due to the low ambient temperature, resulting in poor slurry fluidity, uneven soil-slurry interface, and difficulty in ensuring pile strength and density. In addition, traditional construction lacks a feedback mechanism for soil temperature and drilling resistance, and adjustment methods mostly rely on manual experience, making it difficult to respond to environmental changes in a timely manner. This results in unstable pile quality, frequent re-mixing and grouting, and reduced production efficiency. Therefore, to address the above problems, a construction method for improving the forming quality of cement-mixed piles is proposed. Summary of the Invention
[0003] The purpose of the present invention is to provide a construction method for improving the molding quality of cement mixing piles, so as to solve the problems that in low temperature or frozen soil environments, cement slurry is prone to pre-setting or pipeline freezing due to excessively low ambient temperature, resulting in poor slurry fluidity, uneven soil-slurry interface, and difficulty in ensuring pile strength and density. In addition, the traditional construction has insufficient feedback mechanism for soil temperature and drilling resistance, and the adjustment means mostly rely on manual experience, which makes it difficult to respond to environmental changes in a timely manner, resulting in unstable pile quality, frequent re-mixing and grouting, and reduced production efficiency.
[0004] To achieve the above object, the present invention provides the following technical solutions: A construction method for improving the molding quality of cement mixing piles comprises the following steps: Step 1: Construction Preparation: Conduct climate and ground temperature assessments in the construction area to determine daily average air temperature and permafrost temperature changes; Set up a temporary insulation shed and place infrared or convection heaters in it to control the ambient temperature above 5°C; Install insulation jackets or electric heating devices on key equipment such as drilling rigs, mixing heads, slurry pipelines, and cement storage tanks, and set up temperature monitoring points; prepare ordinary Portland cement, antifreeze and water-reducing agent, silica fume, and insulation blanket materials; Step 2: Measure and set out: Use total station or GNSS to perform high-precision layout of pile positions to ensure that the pile spacing and layout meet the design requirements; Markings were set around each pile location and the elevation was checked, which was 7.3m; The piles are arranged in an equilateral triangle with a spacing of 1.4m; Step 3: Equipment in place: Move the drilling rig to the first pile position, adjust the frame to the level and lock the bottom legs; Connect the mixing main unit and pipeline, and check that the electric heating and temperature sensor are operating normally; Ensure that the console automatic recorder is connected to the motor current and shotcrete volume monitoring system; Step 4: Pre-stirring and settling: S41: Pre-drilling is performed at a low speed of 0.5-0.8 m / min using only clean water. Simultaneously, a high-frequency ultrasonic vibration device installed around the mixing head is activated to generate microcracks at the frozen soil interface through ultrasonic waves, achieving dual-mode defreezing. S42: A thermocouple is placed at the front end of the mixing head to collect the surrounding soil temperature in real time ; when Below the preset threshold When the temperature reaches 0.05°C, it will automatically switch to the preheating antifreeze mode. The preheating antifreeze mode is: injecting a mixture of 50°C hot water and antifreeze water-reducing agent into the borehole for temperature control and replenishment; S43: Dynamically obtain drilling resistance using both spindle torque and vibration sensors ; The system decides whether to continue pre-stirring based on the control quantity C(t):
[0005] Where, is the target soil temperature, is the target resistance level, 、 To adjust the weight; When C(t) < 0, it means that the soil is still too cold or the resistance is too large, so maintain ultrasonic + heating pre-mixing; When C(t)≥0, it means that the soil has been loosened and the temperature is sufficient, so the pre-mixing is stopped immediately and the mixing is switched to the spraying mixing. S44: No longer simply exceeding the designed pile length, the end point of thawing is determined based on the change of C(t)C: if thawing is completed and C(t) is ≥ 0 for three consecutive samples, immediately proceed to step 5.
[0006] As a further optimized content of the present invention, the following steps are also included: Step 5: Slurry preparation and delivery: Prepare cement slurry with hot water at about 50°C at a water-cement ratio of 0.5–0.6, add 0.5%–1.0% antifreeze water reducer and 10%–15% silica fume; The mixing tank and slurry discharge pipeline should be kept heated and insulated throughout the entire process, and the temperature should be measured every 1 m in the pipeline to ensure that the slurry temperature is ≥10°C; Start closed-circuit conveying and maintain pressure in the pipe. If slurry needs to be stopped, lower the stirring head to 0.5 m below the pipe mouth and continue stirring at a slow speed. Step 6: Stir and lift: Switch to shotcrete drilling and mixing, control the sinking speed at 0.5-0.8m / min, and implement the shotcrete volume according to the "two-shot four-mixing" standard; After each spraying, lift and stir for 0.3-0.5m, and keep stirring for more than 30s to enhance slurry penetration and soil slurry mixing uniformity; Monitor the motor current and balance torque. If any abnormality occurs, adjust the slurry volume or heat the pipeline immediately. Step 7: Repeat stirring: Repeat the "shotcrete → lifting and mixing" process according to the preset cycle until the pile top elevation is returned; Pause stirring at the top of the pile for 30 seconds, and slowly lift it to the ground and stop the machine after the slurry is initially stabilized.
[0007] As a further optimized content of the present invention, wherein: further comprising the following steps: Step 8: Construction records: The electronic automatic recorder continuously records the spraying volume, mixing time, motor current, and pipeline temperature parameters; Record each spraying depth, construction start / end time, and the lowest temperature of the day in the construction log; Step 9: Pipeline cleaning: After each pile is completed or when a pile connection is required due to a work stoppage of more than 3 hours, the pipeline and mixing head shall be flushed with clean water at high pressure to remove the solidified slurry inside; After flushing, reheat and keep warm, and wait until the temperature inside the pipe returns to normal before proceeding to the next pile construction; Step 10: Rig Shift: After completing one pile, the drilling rig is lifted to the transport height and moved to the next pile position in the direction of the payout; Repeat steps 2 to 9 to complete the construction of all pile positions; Step 11: Quality Inspection: The unconfined compressive strength of the cement-mixed pile after completion is ≥1.0 MPa at 28 days and ≥1.8 MPa at 90 days. The design bearing capacity of the cement-mixed pile composite foundation is 100 kPa.
[0008] Take samples from the test pile area to conduct freeze-thaw cycle tests to verify the strength and uniformity of the pile body under multiple freeze-thaw cycles; Compare the test results with the design standards and indoor comparative test data, and optimize the slurry formula or insulation plan if necessary.
[0009] As a further optimization of the present invention, in step 2, the measurement and layout uses three-dimensional laser scanning and drone orthophoto fusion to construct a BIM model, and combines the shallow ground radar detection results to mark the underground pipelines and the top surface of the permafrost layer, so as to pre-identify obstacles and brittle areas before laying out the lines.
[0010] As a further optimization of the present invention, the equipment placement in step 3 includes self-checking and calibrating the pipelines, electric heating devices and temperature sensors of the drilling rig and slurry delivery system, and real-time verification of the drilling rig center point position through the RTK / GNSS mobile station and AR terminal to ensure a placement accuracy of ±5 cm.
[0011] As a further optimization of the present invention, in step 5, the slurry preparation adopts a composite admixture of hot water slurry, antifreeze water-reducing agent and silica fume, and a temperature monitoring point and closed-loop electric heating control are set in the conveying pipeline to achieve automatic maintenance of the slurry temperature ≥10°C.
[0012] As a further optimization of the present invention, in the stirring, lifting and repeated stirring stages in steps 6 and 7, a high-frequency ultrasonic vibration device is simultaneously started on the periphery of the drill bit to ultrasonically assist in breaking up frozen soil, and the stirring speed and the number of spraying and stirring cycles are automatically adjusted according to the preset control amount based on the real-time torque and vibration signals.
[0013] As a further optimization of the present invention, in step 8, the construction record synchronously collects the spraying volume, motor current and pipeline temperature through an electronic automatic recorder, and automatically triggers the re-mixing and re-spraying or pipeline cleaning process when it is found that the parameters are out of limit or the shutdown exceeds 3 hours.
[0014] As a further optimization of the present invention, the quality inspection in step 11 includes conducting an unconfined compressive strength test at the age of 28 days and performing a freeze-thaw cycle simulation on the test pile area to verify the strength and uniformity of the pile body under the action of periodic freeze-thaw, and the feedback results are used to optimize the insulation and formulation scheme.
[0015] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, by introducing all-round temperature monitoring and thermal insulation heating measures, the pre-solidification or freezing of cement slurry in the pipeline and during the spraying and mixing process under low temperature conditions is effectively prevented, thereby ensuring the continuous fluidity and uniform proportion of the slurry; the pre-mixing and defreezing technology combining ultrasonic vibration and thermal control supply is utilized, and the defreezing depth and timing are automatically determined through control quantities based on the real-time collected soil temperature and drilling resistance signals, which can adaptively complete the efficient crushing and loosening of the frozen soil layer, greatly improving the defreezing efficiency of the pre-mixing stage; in the spraying and lifting mixing processes, the spraying amount, mixing depth and suspension time are closed-loop regulated to ensure the dense and uniform soil-slurry mixture; finally, the online construction record and automatic pipeline cleaning mechanism, as well as the freeze-thaw cycle and strength detection feedback, enable the entire construction process to form a closed-loop quality control, and achieve high consistency, high strength and high reliability in the formation of cement mixing piles in severe cold or frozen soil environments. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 A schematic diagram of pile foundation arrangement for a construction method for improving the molding quality of cement mixing piles according to the present invention; Figure 2 The present invention is a flow chart of a construction method for improving the molding quality of cement mixing piles. DETAILED DESCRIPTION
[0017] Example 1: Example of construction in a cold frozen soil environment: Environmental characteristics: The surface temperature is usually between -15℃ and -5℃, the frozen soil layer is about 1.2m deep, and the temperature difference between day and night is small; See also Figure 1-Figure 2 The present invention provides a technical solution: a construction method for improving the molding quality of cement mixing piles. Steps 1-3: Preparation, laying out and positioning: Set up a heat preservation shed and install electric heaters to maintain the temperature inside the shed above 5°C; High-precision line setting was performed using a total station + GNSS, with an elevation of 7.30 m. Stakes were arranged in an equilateral triangle with a spacing of 1.40 m. After line setting, the center error was verified using an AR terminal to within ±5 cm. When the drilling rig is in place, self-check and calibrate the pipeline, electric heating device and temperature sensor to ensure the monitoring system is connected; Step 4: Ultrasonic + thermal control pre-stirring and sinking: The soil was pre-mixed with clean water at a low speed of 0.8 m / min, and the ultrasonic vibration device was activated to break up the frozen soil; The thermocouple at the front end of the stirring head detects the temperature. If it drops to ≤3°C, 50°C preheated antifreeze liquid (containing 0.8% antifreeze water reducer) will be automatically injected. The control quantity C(t) is calculated based on the torque and vibration sensors. When C(t) is ≥ 0 for three consecutive times and the highest depth reaches the designed pile length + 0.2 m, the pre-mixing is stopped and the mixture is switched to the shotcrete mixing. Steps 5-7: Slurry preparation and spraying: Use 50 ℃ hot water to prepare the slurry (water-cement ratio 0.55, add 1.0% antifreeze + 12% silica fume), and keep the pipelines thermally insulated throughout, with the temperature ≥ 12 ℃; The spraying sinking rate is 0.5-0.8 m / min. Perform two spraying and four stirring, lift 0.4 m and stir for 20 s; repeat the cycle to the top of the pile, stop stirring for 30 s to stabilize it, and then pull it out; Steps 8-9: Recording and cleaning: Automatic recorders record the spraying volume (110 L / m), pipe temperature, motor current, etc. If the work is stopped for more than 3 hours, the pipeline is cleaned with high pressure and the work is resumed after it is restored; Steps 10–11: Shift and Detection: The drilling rig moves to the next pile position along the arrangement direction and repeats the above process; The 28-day core sampling test showed that the pile strength reached 1.3 MPa; the strength retention rate after three freeze-thaw cycles was >90%.
[0018] Example 2: Example of construction in a high-altitude freeze-thaw environment: Environmental characteristics: large temperature difference between day and night, with the lowest temperature reaching -20°C, and the frozen soil depth is about 1.5 m; See also Figure 1-Figure 2 The present invention provides a technical solution: a construction method for improving the molding quality of cement mixing piles, steps 1-3: preparation, laying out and positioning: Build a double-layer insulation tent, install a fuel heater inside, and keep the temperature above 8°C; Based on the fusion of drone images, the elevation is 7.30 m and the spacing between triangle stakes is 1.40 m. The error is verified by GNSS + total station and is ≤±3 cm. The drilling rig is in place to self-check the pipeline, electric heating and sensor functions, and confirm that the recorder linkage is normal; Step 4: Dual-mode defrosting and pre-stirring: Pre-stir the water at a speed of 0.8 m / min and activate the ultrasonic vibrator; When the thermocouple detects ≤2°C, 60°C hot water + 0.7% antifreeze will be automatically injected to raise the local temperature to above 8°C; The control value C(t) is used to determine that the frost breaking is complete (C(t) ≥ 0 for three consecutive times and the vibration amplitude drops). Switching is performed after the depth reaches the pile length + 0.3 m. Steps 5-7: Hot and cold spray mixing: 50 ℃ hot water slurry (water-cement ratio 0.55, 0.8% antifreeze + 15% slag powder), closed-circuit electric heating to maintain the temperature at 15 ℃; Two-spray four-stir process, spraying speed 0.5-0.8m / min, lifting 0.5m and stirring for 30s; circulate to the top, stop stirring for 1min to form temperature control protection; Steps 8-9: Monitoring and Cleaning: The automatic recorder uploads parameters in real time. If the limit is exceeded or the shutdown is greater than 2 hours, the pipeline is cleaned and the slurry is added before recovery. Steps 10–11: Shift and Evaluate: The drilling rig is precisely moved to the pile lowering position and the process is repeated; The 28-day core sampling test showed that the pile strength reached 1.4 MPa; the strength retention rate after 5 freeze-thaw cycles was >88%.
[0019] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method of the present invention and its core ideas. The above is only a preferred implementation method of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of the present invention.
Claims
1. A construction method for improving the molding quality of cement mixing piles, characterized in that: The following steps are involved: Step 1: Construction Preparation: Conduct climate and ground temperature assessments in the construction area to determine daily average air temperature and permafrost temperature changes; Set up a temporary insulation shed and place infrared or convection heaters in it to control the ambient temperature above 5°C; Install insulation jackets or electric heating devices on key equipment such as drilling rigs, mixing heads, slurry pipelines, and cement storage tanks, and set up temperature monitoring points; prepare ordinary Portland cement, antifreeze and water-reducing agent, silica fume, and insulation blanket materials; Step 2: Measure and set out: Use total station or GNSS to perform high-precision layout of pile positions to ensure that the pile spacing and layout meet the design requirements; Markings were set around each pile location and the elevation was checked, which was 7.3m; The piles are arranged in an equilateral triangle with a spacing of 1.4m; Step 3: Equipment in place: Move the drilling rig to the first pile position, adjust the frame to the level and lock the bottom legs; Connect the mixing main unit and pipeline, and check that the electric heating and temperature sensor are operating normally; Ensure that the console automatic recorder is connected to the motor current and shotcrete volume monitoring system; Step 4: Pre-stirring and settling: S41: Pre-drilling is performed at a low speed of 0.5-0.8 m / min using only clean water. Simultaneously, a high-frequency ultrasonic vibration device installed around the mixing head is activated to generate microcracks at the frozen soil interface through ultrasonic waves, achieving dual-mode defreezing. S42: A thermocouple is placed at the front end of the mixing head to collect the surrounding soil temperature in real time ; when Below the preset threshold When the temperature reaches 0.05°C, it will automatically switch to the preheating antifreeze mode. The preheating antifreeze mode is: injecting a mixture of 50°C hot water and antifreeze water-reducing agent into the borehole for temperature control and replenishment; S43: Dynamically obtain drilling resistance using both spindle torque and vibration sensors ; The system decides whether to continue pre-stirring based on the control quantity C(t):
2. In the formula, is the target soil temperature, is the target resistance level, 、 To adjust the weight; When C(t) < 0, it means that the soil is still too cold or the resistance is too large, so maintain ultrasonic + heating pre-mixing; When C(t)≥0, it means that the soil has been loosened and the temperature is sufficient, so the pre-mixing is stopped immediately and the mixing is switched to the spraying mixing. S44: No longer simply exceeding the designed pile length, the end point of thawing is determined based on the change of C(t)C: if thawing is completed and C(t) is ≥ 0 for three consecutive samples, immediately proceed to step 5.
3. A construction method for improving the molding quality of cement mixing piles according to claim 1, characterized in that: The following steps are also included: Step 5: Slurry preparation and delivery: Prepare cement slurry with hot water at about 50°C at a water-cement ratio of 0.5–0.6, add 0.5%–1.0% antifreeze water reducer and 10%–15% silica fume; The mixing tank and slurry discharge pipeline are kept heated and insulated throughout the process, and the temperature is measured every 1 m in the pipeline to ensure that the slurry temperature is ≥10℃; Start closed-circuit conveying and maintain pressure in the pipe. If slurry needs to be stopped, lower the stirring head to 0.5 m below the pipe mouth and continue stirring at a slow speed. Step 6: Stir and lift: Switch to shotcrete drilling and mixing, control the sinking speed at 0.5-0.8 m / min, and implement the "two-shot four-mixing" standard for the shotcrete volume; After each spraying, lift and stir for 0.3–0.5 m and keep stirring for more than 30 seconds to enhance slurry penetration and soil slurry mixing uniformity; Monitor the motor current and balance torque. If any abnormality occurs, adjust the slurry volume or heat the pipeline immediately. Step 7: Repeat stirring: Repeat the "shotcrete → lifting and mixing" process according to the preset cycle until the pile top elevation is returned; Pause stirring at the top of the pile for 30 seconds, and slowly lift it to the ground after the slurry is initially stable and stop the machine.
4. A construction method for improving the molding quality of cement mixing piles according to claim 1, characterized in that: Further comprising the steps of: Step 8: Construction records: The electronic automatic recorder continuously records the spraying volume, mixing time, motor current, and pipeline temperature parameters; Record each spraying depth, construction start / end time, and the lowest temperature of the day in the construction log; Step 9: Pipeline cleaning: After each pile is completed or when a pile connection is required due to a work stoppage of more than 3 hours, the pipeline and mixing head shall be flushed with clean water at high pressure to remove the solidified slurry inside; After flushing, reheat and keep warm, and wait until the temperature inside the pipe returns to normal before proceeding to the next pile construction; Step 10: Rig Shift: After completing one pile, the drilling rig is lifted to the transport height and moved to the next pile position in the direction of the payout; Repeat steps 2 to 9 to complete the construction of all pile positions; Step 11: Quality Inspection: The unconfined compressive strength of the cement-mixed pile after completion is ≥1.0 MPa at 28 days and ≥1.8 MPa at 90 days. The design bearing capacity of the cement-mixed pile composite foundation is 100 kPa.
5. Take samples from the test pile area to conduct freeze-thaw cycle tests to verify the strength and uniformity of the pile body under multiple freeze-thaw cycles; Compare the test results with the design standards and indoor comparative test data, and optimize the slurry formula or insulation plan if necessary.
6. The construction method for improving the molding quality of cement mixing piles according to claim 1, characterized in that: The surveying and layout described in step 2 uses a fusion of three-dimensional laser scanning and drone orthophotos to construct a BIM model, and combines shallow ground radar detection results to mark underground pipelines and the top surface of the permafrost layer to pre-identify obstacles and brittle areas before laying out the lines.
7. The construction method for improving the molding quality of cement mixing piles according to claim 1, characterized in that: The equipment placement described in step 3 includes self-checking and calibration of the pipelines, electric heating devices and temperature sensors of the drilling rig and slurry delivery system, and real-time verification of the drilling rig center point position through the RTK / GNSS mobile station and AR terminal to ensure a positioning accuracy of ±5 cm.
8. The construction method for improving the molding quality of cement mixing piles according to claim 2, characterized in that: In step 5, the slurry is prepared by using a composite formula of hot water slurry, antifreeze water reducer and silica fume, and a temperature monitoring point and closed-loop electric heating control are set in the conveying pipeline to achieve automatic maintenance of the slurry temperature ≥10°C.
9. The construction method for improving the molding quality of cement mixing piles according to claim 2, characterized in that: During the stirring, lifting and repeated stirring stages described in steps 6 and 7, a high-frequency ultrasonic vibration device is simultaneously activated on the periphery of the drill bit to ultrasonically assist in breaking up the frozen soil, and the stirring speed and the number of spraying and stirring cycles are automatically adjusted according to the preset control amount based on the real-time torque and vibration signals.
10. The construction method for improving the molding quality of cement mixing piles according to claim 3, characterized in that: In step 8, the construction record synchronously collects the shotcrete volume, motor current and pipeline temperature through the electronic automatic recorder, and automatically triggers the re-mixing and re-spraying or pipeline cleaning process when it is found that the parameters are out of limit or the work is stopped for more than 3 hours.
11. The construction method for improving the molding quality of cement mixing piles according to claim 3, characterized in that: The quality inspection described in step 11 includes an unconfined compressive strength test at the age of 28 days and a freeze-thaw cycle simulation of the test pile area to verify the strength and uniformity of the pile body under the action of periodic freeze-thaw. The feedback results are used to optimize the insulation and mix ratio scheme.