Carbonization and flocculation combined multi-position vacuum preloading treatment test method and test device

Abstract

The invention relates to a carbonization and flocculation combined multi-position vacuum preloading treatment test method and device, and the method comprises the following steps: S1, forming a negative pressure in a pressure-resistant test barrel in which blow-filled soft soil mixed with a calcium-based flocculant is located, setting a test temperature, injecting carbon dioxide to increase the pressure intensity of the pressure-resistant test barrel at intervals in a stepped manner, and carrying out carbonization and flocculation treatment on the pressure-resistant test barrel; the pH, pressure, flow and liquid level changes are detected at the same time; s2, when the mud-water interface descends to be smaller than the preset height in the reaction period, carbon dioxide injection is stopped; s3, taking all the supernate, reserving a sample for testing, and sampling and testing by utilizing a lower soil body to obtain soil body strength data; s4, vacuum preloading is conducted on drainage water at the bottom and the middle of the pressure-resistant test barrel and drainage water at the bottom, the middle and the top of the pressure-resistant test barrel, the corresponding water drainage amount and pore pressure stress are collected, and the water content and the carbon sequestration rate are calculated. According to the invention, combined experiment in one test device can be realized, the process is simplified, and different vacuum preloading model tests can be carried out.

Description

Technical Field

[0001] The invention relates to the technical field of environmental geotechnical engineering, and in particular to a carbonization flocculation combined with multi-position vacuum preloading treatment test method and device. Background Art

[0002] Land reclamation is an ancient and important way for humans to use marine resources to obtain a wider living space. By filling the sea and building new land, land reclamation can not only increase the land area of ​​the region, but also promote economic development. With the gradual acceleration of urbanization in my country, the shortage of land resources in large, medium and small cities has become increasingly severe, especially in the economically developed provinces and cities along the southeast coast, where land reclamation activities have increased year by year. Most of the land for sea reclamation is filled with dredged mud, which has a high water content, a thick soft soil layer, and extremely poor engineering properties. Dehydration and reinforcement treatment is required to improve the strength of the soft soil foundation and provide a solid foundation for the construction of buildings.

[0003] The vacuum preloading method has better economy and reinforcement processing capacity, and has obvious advantages in large-scale soft soil foundation treatment, and has gradually become the mainstream method for treating soft soil sites. However, vacuum preloading has disadvantages such as easy clogging of the filter membrane and too long reinforcement cycle. In recent years, people have introduced chemical flocculants into the vacuum preloading soft soil foundation treatment. Studies have shown that chemical agents combined with vacuum preloading can well overcome the above two shortcomings. Commonly used inorganic chemical flocculants are CaO and Ca(OH)2, which will react with carbon dioxide in the air or water to form calcium carbonate, which can be called carbon absorption flocculants. CaCO3 cement is attached to the surface of soil particles and acts as a connection between adjacent soil particles. CaCO3 is very stable and can make carbon dioxide exist in the foundation in the form of compounds for a long time to achieve foundation carbon fixation.

[0004] By adding carbon dioxide gas to the blown fill soft soil treatment process combined with vacuum preloading, the composition of elements and compounds in the dredged sludge, as well as the microstructures such as the particle size and connection mode of soil particles, pore size, shape and connectivity, etc., are changed, thereby changing its macroscopic properties such as consolidation, permeability, compression, and strength. This is another blown fill soft soil foundation treatment method that is different from the current vacuum preloading method and incorporates the concept of carbon fixation.

[0005] In summary, it can be seen that the existing flocculation combined with vacuum preloading has not fully explored and utilized the carbon fixation capacity of the soft fill foundation. The carbonization flocculation combined with vacuum preloading treatment process can not only use carbonization flocculation to stably fix a large amount of greenhouse gases in the foundation soil, but also use carbonization products to change the properties of the soft fill and promote the vacuum preloading reinforcement effect. However, the carbonization flocculation combined with vacuum preloading of soft fill foundation is still in its infancy. The carbonization flocculation mechanism of soft fill is not clear, and the pretreatment process still needs to be further improved. The vacuum preloading characteristics after carbonization flocculation are very different from the past, and further in-depth research is urgently needed. This requires fully considering the influencing factors of carbonization flocculation vacuum preloading treatment of soft fill foundation, developing corresponding test equipment and test methods, and providing theoretical basis and practical reference for soft fill foundation treatment, which is of great significance to the promotion of carbonization flocculation vacuum preloading technology. Summary of the invention

[0006] In view of this, the problem to be solved by the present invention is to provide a carbonization flocculation combined with multi-position vacuum pre-pressing treatment test method and experimental device.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a carbonization flocculation combined with multi-position vacuum preloading treatment test method, comprising the following steps: Step S1: forming a negative pressure in the pressure test barrel where the dredger fill soft soil mixed with the calcium-based flocculant is located, setting the test temperature, injecting carbon dioxide to increase the pressure step interval of the pressure test barrel, and detecting changes in pH, pressure, flow rate and liquid level at the same time; Step S2: When the mud-water interface drops below a preset height during the reaction period, the carbon dioxide injection is stopped; Step S3: Take all the supernatant and keep samples for testing, and use the lower soil to sample and test to obtain soil strength data; Step S4: vacuum pre-pressing the bottom, middle and bottom, middle and top drainage of the pressure test barrel respectively, collecting the corresponding drainage volume and pore pressure stress, and calculating the moisture content and carbon fixation rate.

[0008] In the present invention, preferably, the vacuum pre-pressurization of the bottom of the pressure test barrel in step S4 is specifically as follows: the top of the soil in the pressure test barrel is sealed, a low-level drainage board and a piezometer are placed at the bottom, and negative pressure is used to drain water to the liquid collecting bottle.

[0009] In the present invention, preferably, the middle and bottom of the pressure test barrel are vacuum pre-pressurized in step S4 as follows: the top of the soil in the pressure test barrel is sealed, a low-level drainage board is placed at the bottom, a mid-level drainage board and a piezometer are placed in the middle, and negative pressure is used to drain water to the liquid collecting bottle.

[0010] In the present invention, preferably, the vacuum pre-pressurization of the middle part of the pressure test barrel in step S4 is specifically as follows: the top of the soil in the pressure test barrel is sealed, a spring drain pipe is inserted between the pressure test barrel and the top of the soil, the middle part of the spring drain pipe is connected to a hole pressure gauge, and negative pressure is used to drain water to a liquid collecting bottle.

[0011] In the present invention, preferably, the vacuum pre-pressurization of the top of the pressure test barrel in step S4 is specifically as follows: the top of the soil in the pressure test barrel is sealed, a spring drain pipe is inserted between the pressure test barrel and the top of the soil, the top of the spring drain pipe is connected to a piezometer, and negative pressure is used to drain water to a liquid collecting bottle.

[0012] The carbonization flocculation combined with multi-position vacuum pre-pressure treatment test device of the present invention comprises a pressure test barrel and a drainage mechanism. The pressure test barrel is vertically provided with a scale, the bottom of the pressure test barrel is connected to a carbon dioxide source, and the top of the pressure test barrel is connected to a vacuum mechanism.

[0013] In the present invention, preferably, the drainage mechanism is configured as a low-level drainage plate, and the low-level drainage plate is disposed at the bottom of the pressure test barrel and is connected to a piezometer.

[0014] In the present invention, preferably, the drainage mechanism is configured as a low-level drainage board and a middle-level drainage board, the low-level drainage board is arranged at the bottom of the pressure test barrel, the middle-level drainage board is fixedly connected to the low-level drainage board through a vertical supporting structure, and the low-level drainage board and the middle-level drainage board are both connected to a piezometer.

[0015] In the present invention, preferably, the drainage mechanism is configured as a spring drain pipe, and a piezometer is connected to the middle or top of the spring drain pipe.

[0016] In the present invention, preferably, the vacuum mechanism comprises a vacuum pump, and the vacuum pump is used to provide negative pressure for the pressure test barrel.

[0017] The present invention proposes a carbonization flocculation combined with multi-position vacuum preloading treatment test method and test device. Aiming at the characteristics of high moisture content and low bearing capacity of soft soil foundation in blown fill, the performance and mechanism of carbonization flocculation combined with vacuum preloading treatment under the influence of different carbonization pressures, carbonization temperatures, drainage board types and vacuum preloading methods are studied. The invention can comprehensively consider the influencing factors of carbonization flocculation vacuum preloading, derive the influence rules of various factors, and guide the determination of the process parameter optimization scheme. The application scheme can provide research support for carbonization flocculation and multi-position vacuum preloading processes for blown fill soft foundations, and is of great significance to the construction of blown fill projects and the promotion of carbonization flocculation combined with vacuum preloading processes.

[0018] The advantages and positive effects of the present invention are: (1) The conventional flocculation vacuum test device and method firstly conducts the flocculation test in a measuring cylinder and then transfers the flocs into a vacuum preloaded model barrel. The test device and test method of the present application can realize a combined experiment in one test device, thus simplifying the test process.

[0019] (2) Traditional carbonization test devices are mostly used for concrete or solidified soil with a certain degree of self-stability, and flocculation test devices can only be used under normal pressure conditions, and are almost impossible to be used for carbonization and flocculation tests of high-water-content dredger fill soft soil under pressure. The test device and test method of this application can realize the carbonization and flocculation test of high-water-content dredger fill soft soil in a fluid state, and can study the influence of carbonization temperature and carbonization pressure.

[0020] (3) Conventional vacuum preloading test devices can generally only consider one type of drain board parameter and vacuum preloading condition. However, the test device and test method of the present application can select different components for different working conditions, connect them to the corresponding ports, and conduct different vacuum preloading model tests according to the test method. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a structural schematic diagram of the carbonization flocculation combined with multi-position vacuum pre-pressing treatment test device of the present invention; Figure 2 It is a schematic cross-sectional structure diagram of a carbonization flocculation combined with multi-position vacuum pre-pressing treatment test device of the present invention; Figure 3 is a schematic structural diagram of Embodiment 1 of the present invention; Figure 4 is a schematic structural diagram of Embodiment 2 of the present invention; Figure 5 is a schematic structural diagram of Embodiment 3 of the present invention; Figure 6 is a schematic structural diagram of a fourth embodiment of the present invention; In the figure: 1. Steel top cover; 2. Acrylic flange; 201. Flange trapezoidal reinforcement rib; 3. Fastening bolts; 4. Acrylic tube; 5. Acrylic bottom plate; 501. Bottom plate trapezoidal reinforcement rib; 6. Fixed support; 7. Middle position vent valve; 8. Low position vent valve; 9. Positive and negative pressure gauges; 10. Three-way valve; 11. Temperature control device; 1101. Thermostat; 1102. Heater; 12. Steel wire air pipe; 13. Vacuum pump; 14. Carbon dioxide pressure regulator valve; 15. flow meter; 16. carbon dioxide cylinder; 17. carbon dioxide pressure reducing valve; 18. alkali liquid tank; 19. camera; 20. computer; 21. pH meter; 22. low-level drainage board; 23. sewage outlet; 24. round acrylic plate; 25. pore pressure gauge; 26. laser displacement meter; 27. liquid collecting bottle; 28. vacuum gauge; 29. ​​electronic scale; 30. middle-level drainage board; 31. geomembrane; 32. spring drain pipe; 33. tee. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0025] Embodiment 1: The carbonization flocculation combined with multi-position vacuum preloading treatment experimental method of the present invention studies the carbonization flocculation characteristics of dredger fill soft soil under the influence of different carbonization pressures and carbonization temperatures, and comprises the following steps: Step S1: forming a negative pressure in the pressure test barrel where the dredger fill soft soil mixed with the calcium-based flocculant is located, setting the test temperature, injecting carbon dioxide to increase the pressure step interval of the pressure test barrel, and detecting the pH, pressure, flow rate and liquid level changes at the same time. For different dredger fill soft soils, different types or different mixing amounts of calcium-based flocculants can be selected to achieve different variable controls; Step S2: When the mud-water interface drops below a preset height during the reaction period, the carbon dioxide injection is stopped; Step S3: taking all the supernatant and keeping samples for testing, taking samples from the lower soil for testing, and obtaining soil strength data; Step S4: perform vacuum preloading on the bottom, middle and bottom, middle and top drainage of the pressure test barrel respectively, collect the corresponding drainage volume and pore pressure stress, calculate the moisture content and carbon fixation rate, so as to select different components for different working conditions, connect them to the corresponding ports and perform different vacuum preloading model tests according to the test method.

[0026] In this embodiment, further, a test method for the vacuum preloading characteristics of the bottom position of the pressure test barrel is provided. In step S4, the vacuum preloading of the bottom of the pressure test barrel is specifically performed as follows: the top of the soil in the pressure test barrel is sealed, specifically, all valves on the pressure test barrel are adjusted to a closed state, the steel top cover 1 is removed, the low-level drainage board 22 is connected to the low-level ventilation valve 8 through a hose, and the low-level drainage board 22 is horizontally placed in the acrylic cylinder 4, the blown fill soft soil and the calcium-based flocculant are mixed and poured into the barrel, and the calibrated pH is stirred evenly with a constant speed stirrer. The meter 21 is attached to the upper part of the interior of the acrylic tube 4, and the probe of the pH meter 21 is inserted into the soil. The steel top cover 1 is fixed by the fastening bolts 3 to form a completely closed space in the pressure test barrel; the vacuum pump 13 is connected to the three-way valve 10 through the steel wire air pipe, and the three-way valve 10 is adjusted to the vacuum state, and the vacuum pump 13 is turned on. When the readings of the positive and negative pressure gauges 9 reach -60kPa, the vacuum valve is closed, and the readings of the positive and negative pressure gauges 9 are observed to see whether they drop, and the air tightness of the pressure test barrel is tested. When the vacuum pressure drops, check the valves and air pipes on the steel top cover 1 and the pressure test barrel. Connection status: A low-level drainage plate 22 and a piezometer 25 are placed at the bottom, and negative pressure is used to drain water to the liquid collecting bottle 27. The signal transmission line of the piezometer 25 passes through the geomembrane 31 and the center hole of the circular acrylic plate 24 in sequence and is connected to the computer 20; the low-level ventilation valve 8 is connected to the air pipe, and is connected to the liquid collecting bottle 27 and the vacuum pump 13 in sequence. The liquid collecting bottle 27 is placed on an electronic scale 29 and is equipped with a vacuum gauge 28; the middle-level ventilation valve 7 and the low-level ventilation valve 8 are connected to the tee 33 through the air pipe, and the tee 33 is connected to the liquid collecting bottle 27 and the vacuum pump 13 in sequence. The liquid collecting bottle 27 is provided with The vacuum gauge 28 is placed on the electronic scale 29; the mid-position ventilation valve 7 is connected to the air pipe, and is connected to the liquid collecting bottle 27 and the vacuum pump 13 in turn. The liquid collecting bottle 27 is placed on the electronic scale 29 and is equipped with a vacuum gauge 28; the vacuum pump 13 is connected to one port of the three-way valve 10 through the air pipe; when the positive and negative pressure gauges 9 read 0, unscrew the fastening bolts 3, remove the steel top cover 1, remove the pH meter 21, remove the pipeline on the low-position ventilation valve 8, take out all the supernatant through the beaker and the liquid collector and keep the sample for testing, use the soil sampling cup to sample the lower soil for testing, and the carbonization flocculation test is completed.

[0027] Embodiment 2: like Figure 4As shown, different from the first embodiment, the present embodiment provides a test method for studying the vacuum preloading characteristics of the middle position and the bottom position of the pressure test barrel after carbonization and flocculation of blown fill soft soil. The soil in the barrel is taken out until the middle vent valve 7 is exposed, and the middle vent valve 7 is connected to the middle drain plate 30 at one end inside the barrel through an air pipe, and the middle vent valve 7 is connected to the air pipe at one end outside the barrel and then connected to the tee 33. The low-level vent valve 8 is connected to the air pipe and then connected to the tee 33. The top of the soil in the pressure test barrel is sealed, and the drainage mechanism is provided as a low-level drain plate 22 and a middle drain plate 30. The low-level drain plate 22 is provided at the bottom of the pressure test barrel, and the middle drain plate 30 is fixedly connected to the low-level drain plate 22 through a vertical support structure. The low-level drain plate 22 and the middle drain plate 30 are both connected to a perforated pressure gauge 25. The low-level drain plate 22 is placed at the bottom. Place a mid-level drainage board 30 and a piezometer 25 in the middle position, insert the piezometer 25 into the soil using a glass rod, backfill the soil to the initial height and scrape the soil surface flat, pass the piezometer 25 signal transmission line through the geomembrane 31 and the center hole of the circular acrylic plate 24 in turn and connect it to the computer 20, spread the geomembrane 31 flat on the soil surface, insert the edge of the geomembrane 31 into the soil along the inner wall of the acrylic tube 4, apply vaseline around the circular acrylic plate 24 and gently place it on the geomembrane 31, use negative pressure to drain water to the liquid collecting bottle 27, the mid-level drainage board 30 is connected to the mid-level vent valve 7 through a hose and placed horizontally inside the acrylic tube 4, use a high-definition camera 19 to record the readings of the vacuum gauge 28 and the electronic scale 29, and when there is no obvious increase in the liquid in the liquid collecting bottle 27, the test is over, the soil is taken out and the sample is kept, the sewage outlet 23 is opened, and the test equipment is flushed.

[0028] Embodiment three: like Figure 5 As shown, different from Example 1 and Example 2, this embodiment provides a test method for the vacuum preloading characteristics of the middle position of the pressure test barrel along the radial direction of the spring drain pipe 32, and the vacuum preloading of the middle part of the pressure test barrel in step S4 is specifically as follows: the top of the soil in the pressure test barrel is sealed, the drainage mechanism is set as a spring drain pipe 32, and the spring drain pipe 32 is inserted between the pressure test barrel and the top of the soil. The middle part of the spring drain pipe 32 is connected to a hole pressure gauge 25, and negative pressure is used to drain water to the liquid collecting bottle 27. The spring drain pipe 32 is connected to a hose in the middle and is connected to one end 7 of the mid-position vent valve, and the other end of the mid-position vent valve 7 is connected to the liquid collecting bottle 27 through an air pipe.

[0029] Embodiment 4: like Figure 6As shown, different from the first, second and third embodiments, the present embodiment provides a test method for the vacuum preloading characteristics of the top position of the pressure test barrel along the radial direction of the spring drain pipe 32, and the vacuum preloading of the top of the pressure test barrel in step S4 is specifically as follows: the top of the soil in the pressure test barrel is sealed, and the spring drain pipe 32 is placed between the pressure test barrel and the top of the soil, the top of the spring drain pipe 32 is connected to the hole pressure gauge 25, and negative pressure is used to drain water to the liquid collecting bottle 27; the top connecting hose of the spring drain pipe 32 passes through the central holes of the geomembrane 31 and the circular acrylic plate 24 in turn and is connected to the liquid collecting bottle 27 and the vacuum pump 13 in turn.

[0030] The specific structure of the pressure test barrel includes a steel top cover 1, an acrylic tube 4 and an acrylic bottom plate 5. The steel top cover 1 is fixedly connected to the acrylic tube 4 through an acrylic flange 2, and the acrylic bottom plate 5 is fixedly connected to the acrylic tube 4; the carbonization flocculation component includes a steel wire air pipe 12, a carbon dioxide pressure regulating valve 14, a flow meter 15, a carbon dioxide cylinder 16, and a carbon dioxide pressure reducing valve 17. The bottom of the acrylic tube 4 is connected to the two The carbon dioxide cylinder 16 is connected to the low-level ventilation valve 8 after being connected to the zeroed flowmeter 15 through the steel wire air pipe; the steel top cover 1 is connected to the alkali liquid tank 18 through the steel wire air pipe 12 and the carbon dioxide pressure reducing valve 17, and the carbon dioxide pressure regulating valve 14 is connected to the flowmeter 15 and the carbon dioxide pressure reducing valve 17 through the steel wire air pipe 12, one end of which is connected to an outlet of the three-way valve 10 through the steel wire air pipe, and the other end is connected to the alkali liquid tank 18 through the steel wire air pipe.

[0031] The vacuum mechanism also includes a circular acrylic plate 24, a liquid collecting bottle 27, a geomembrane 31, and a tee 33. The low-level drainage plate 22 is connected to the opening of the low-level ventilation valve 8 through a hose, and the low-level drainage plate 22 is horizontally placed inside the acrylic tube 4; the geomembrane 31 is laid flat on the soil surface, and the edge of the geomembrane 31 is inserted into the soil along the inner wall of the acrylic tube 4. The circular acrylic plate 24 is coated with vaseline all around and then placed on the geomembrane 31.

[0032] The steel top cover 1 is provided with positive and negative pressure gauges 9, a three-way valve 10 and a temperature control device 11. The temperature control device includes a thermostat 1101 and a heater 1102. The thermostat 1101 is provided on the steel top cover 1, and the free end of the thermostat 1101 is penetrated and extended into the interior of the steel top cover 1, and the end of the thermostat 1101 is fixedly connected to the heater 1102. After the air tightness test is passed, the three-way valve 10 is adjusted to a closed state, the vacuum pump 13 is removed, the carbon dioxide cylinder 16 equipped with a carbon dioxide pressure regulating valve 14 is connected to the zeroed flow meter 15 through a steel wire air pipe and then connected to the low-level ventilation valve 8, the temperature control device 11 is turned on and adjusted to the test temperature, the low-level ventilation valve 8 and the carbon dioxide cylinder 16 are opened, and the carbon dioxide pressure regulating valve 14 is adjusted in stages at 50kPa intervals from the initial 50kPa to the carbonization pressure designed for the test, and each pressure increase must be performed after the readings of the positive and negative pressure gauges 9 are stable; In this embodiment, further, the acrylic tube 4 is provided with a scale 401 in the vertical direction, a pH meter 21 is provided on the upper inner wall of the acrylic tube 4, a low-position vent valve 8 is installed at the bottom of the acrylic tube 4, and a middle-position vent valve 7 is installed in the middle of the acrylic tube 4.

[0033] The structure that plays the role of data monitoring and storage includes positive and negative pressure gauges 9, a camera 19, a computer 20, a pH meter 21, a pore pressure gauge 25, a laser displacement meter 26, a vacuum gauge 28 and an electronic scale 29. The camera 19, the pore pressure gauge 25 and the laser displacement meter 26 are all electrically connected to the computer 20. The camera 19 is used to continuously record the readings of the positive and negative pressure gauges 9, the pH meter 21, the vacuum gauge 28 and the electronic scale 29. All components of the test device are within the shooting range of the camera 19. During the test, the camera 19 is used to record the readings of the pH meter 21, the positive and negative pressure gauges 9, the flow meter 15 and the mud-water interface on the scale 401, and store them in the computer 20; the pH meter 21 is pasted on the inner wall of the acrylic tube 4 with the display screen facing the outside of the tube, the piezometer 25 is vertically arranged in the acrylic tube 4, and the laser displacement meter 26 is arranged on the acrylic flange 2; the beginning of the descent of the mud-water interface marks the beginning of the flocculation reaction. When the mud-water interface drops less than 2 mm in 12 hours, the carbonization flocculation is considered to be completed, the low-level vent valve 8 and the carbon dioxide cylinder 16 are closed, the carbon dioxide pressure reducing valve 17 is adjusted to 50 kPa, and the three-way valve 10 is adjusted to the exhaust state, so that the carbon dioxide in the barrel is slowly discharged to the alkali solution tank 18 at low pressure for carbonization reaction to prevent greenhouse gas pollution.

[0034] The flowmeter in the middle of the pressure test barrel is used to record instantaneous flow and cumulative flow; the liquid level change is collected by recording the mud-water interface (the supernatant is clear after flocculation and the interface can be visually seen) on the barrel scale through a camera, and then a curve graph is drawn manually; the soil strength is tested at different locations with a cross-plate shear instrument after the test; the drainage is calculated using the weight of the water in the water collection bottle; the pore pressure is automatically recorded in the computer through the pore pressure probe. The pH value reflects the changes in the chemical environment of the blown fill soft soil during the experiment, which can reveal the influence of the reaction rate and environment; pressure refers to the carbonization pressure. Under different pressures, the carbonization rate is different and the final carbon fixation amount is different; flow rate is auxiliary data, which is used to ensure the uniformity of other conditions of parallel experiments; liquid level changes reflect the flocculation rate of the blown fill soft soil and the water output during the deadweight flocculation stage; soil strength refers to the cross-plate shear strength, which can be directly read in situ tests; drainage and pore pressure are used to reveal the vacuum rate and vacuum effect as well as the distribution of the vacuum field, thereby clarifying the mechanism of vacuum preloading. The moisture content is calculated through drying experiments, and the carbon fixation rate is obtained through the carbonate detection method in the soil. For relevant national standards, please refer to JTG 3430-2020 and GB9835-88.

[0035] The acrylic flange 2 is fixed with fastening bolts 3 and flange trapezoidal reinforcement ribs 201, and the pressure test barrel also includes a fixed support 6; the acrylic bottom plate 5 is provided with bottom plate trapezoidal reinforcement ribs 501, and the bottom of the acrylic bottom plate 5 is provided with a sewage outlet 23 with a switch; the carbon dioxide pressure regulating valve 14 is installed on the outlet of the carbon dioxide cylinder 16; the diameter of the circular acrylic plate 24 is smaller than the inner diameter of the acrylic tube 4, and a 9mm hole is opened at the center of the circular acrylic plate 24; the steel top cover 1 forms a completely enclosed space with the acrylic flange 2, the acrylic tube 4 and the acrylic bottom plate 5 through the fastening bolts 3; the acrylic flange 2 and the acrylic bottom plate 5 are provided with limiting grooves; the valves connecting the air pipes all use quick-plug connectors of uniform caliber; all or part of the components can be selectively installed in the corresponding positions according to different test conditions. Among them, the mid-position vent valve 7, the low-position vent valve 8, the three-way valve 10, the carbon dioxide pressure regulating valve 14 and the flow meter 15 all use quick-release connectors.

[0036] The present invention proposes a carbonization flocculation combined with multi-position vacuum preloading treatment test method and test method. In view of the characteristics of high moisture content and low bearing capacity of blown fill soft soil foundation, the performance and mechanism of carbonization flocculation combined with vacuum preloading treatment under the influence of different carbonization pressures, carbonization temperatures, drainage board types and vacuum preloading methods are studied. The invention can comprehensively consider the influencing factors of carbonization flocculation vacuum preloading, derive the influence rules of each factor, and guide the determination of the process parameter optimization scheme. The application scheme can provide research support for blown fill soft foundation carbonization flocculation and multi-position vacuum preloading technology, which is of great significance to the construction of blown fill projects and the promotion of carbonization flocculation combined with vacuum preloading technology.

[0037] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of this patent.

Claims

1. Carbonization flocculation combined with multi-position vacuum preloading treatment test method, characterized in that: The steps include: Step S1: forming a negative pressure in the pressure test barrel where the soft soil mixed with the calcium-based flocculant is located, setting the test temperature, injecting carbon dioxide to increase the pressure step interval of the pressure test barrel, and detecting changes in pH, pressure, flow rate and liquid level at the same time; Step S2: When the mud-water interface drops below a preset height during the reaction period, the carbon dioxide injection is stopped; Step S3: Take all the supernatant and keep samples for testing, and use the lower soil to sample and test to obtain soil strength data; Step S4: vacuum pre-pressing the bottom, middle and bottom, middle and top drainage of the pressure test barrel respectively, collecting the corresponding drainage volume and pore pressure stress, and calculating the moisture content and carbon fixation rate.

2. The carbonization flocculation combined with multi-position vacuum preloading treatment test method according to claim 1 is characterized in that: In step S4, the bottom of the pressure test barrel is vacuum pre-pressurized as follows: the top of the soil in the pressure test barrel is sealed, a low-level drainage board and a piezometer are placed at the bottom, and negative pressure is used to drain water to the liquid collecting bottle.

3. The carbonization flocculation combined with multi-position vacuum preloading treatment test method according to claim 1 is characterized in that: In step S4, the middle and bottom of the pressure test barrel are vacuum pre-pressurized as follows: the top of the soil in the pressure test barrel is sealed, a low-level drainage board is placed at the bottom, a mid-level drainage board and a piezometer are placed in the middle, and negative pressure is used to drain water to the liquid collecting bottle.

4. The carbonization flocculation combined with multi-position vacuum preloading treatment test method according to claim 1 is characterized in that: In step S4, vacuum pre-pressurization is performed on the middle part of the pressure test barrel as follows: the top of the soil in the pressure test barrel is sealed, a spring drain pipe is inserted between the pressure test barrel and the top of the soil, the middle part of the spring drain pipe is connected to a hole pressure gauge, and negative pressure is used to drain water to a liquid collecting bottle.

5. The carbonization flocculation combined with multi-position vacuum preloading treatment test method according to claim 1 is characterized in that: In step S4, vacuum pre-pressurization is performed on the top of the pressure test barrel as follows: the top of the soil in the pressure test barrel is sealed, a spring drain pipe is inserted between the pressure test barrel and the top of the soil, the top of the spring drain pipe is connected to a piezometer, and negative pressure is used to drain water to a liquid collecting bottle.

6. An experimental device using the carbonization flocculation combined with multi-position vacuum preloading treatment test method as described in any one of claims 1 to 5, characterized in that: The invention comprises a pressure test barrel and a drainage mechanism. The pressure test barrel is vertically provided with a scale. The bottom of the pressure test barrel is connected to a carbon dioxide source. The top of the pressure test barrel is connected to a vacuum mechanism.

7. The experimental device according to claim 6, characterized in that: The drainage mechanism is configured as a low-position drainage plate, and the low-position drainage plate is disposed at the bottom of the pressure test barrel and is connected to a piezometer.

8. The experimental device according to claim 6, characterized in that: The drainage mechanism is configured as a low-position drainage board and a middle-position drainage board. The low-position drainage board is arranged at the bottom of the pressure test barrel. The middle-position drainage board is fixedly connected to the low-position drainage board through a vertical supporting structure. The low-position drainage board and the middle-position drainage board are both connected to a piezometer.

9. The experimental device according to claim 6, characterized in that: The drainage mechanism is configured as a spring drainage pipe, and a piezometer is connected to the middle or top of the spring drainage pipe.

10. The experimental device according to claim 6, characterized in that: The vacuum mechanism comprises a vacuum pump, and the vacuum pump is used to provide negative pressure for the pressure test barrel.

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