Method for preparing flow-state solidified soil from mud cake

Abstract

The method comprises the following steps: carrying out mud-water separation on mud to form the mud cake, drying the mud cake, reducing the water content of the mud cake to 10-15%, pouring the mud cake into a stirrer, and uniformly mixing with a curing agent to form the flow-state solidified soil. According to the method for preparing the flow-state solidified soil from the mud cakes, only the mud cake drying procedure is added, the water content of the mud cakes is reduced, so that the concentration of reactants is increased, the reaction rate is increased, meanwhile, the efficiency of the mud cakes in the transportation and stirring process on the physical level can be improved, and therefore the forming time of the flow-state solidified soil prepared from the mud cakes is shortened; and the uniformity of the stirring process is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solidified soil, and more specifically, to a method for making fluid solidified soil from mud cakes. Background Art

[0002] Shield tunneling is a commonly used technology for tunnel excavation, especially in complex geological conditions such as urban underground or underwater. During the shield tunneling process, the cutting head at the front end of the shield machine will cut the soil or rock in front during the propulsion. In order to reduce the cutting resistance, cool the cutting head, and carry the cut soil, it is usually necessary to use mud or other types of fluids. The mud is pumped to the head of the shield machine and mixed with the cut soil to form a relatively thin mud mixture. The mud mixed with the soil is transported back to the ground and undergoes a series of treatment steps on the ground, such as screening, sedimentation, dehydration, etc. Part of it is reused for subsequent shield tunneling, and part is used as waste muck mud. Finally, after the shield tunneling is completed, a large amount of waste muck mud is obtained.

[0003] Generally, for the waste muck mud generated by shield tunneling, through an extrusion process, the water in the mud is discharged to produce mud cakes. In most construction sites, the mud cakes are transported and discarded as waste, which consumes a large amount of cost and also affects the environment.

[0004] In this case, the technology of solidified soil is proposed to be applied to the shield waste muck mud. Making fluid solidified soil from mud cakes on the shield site and directly using it for synchronous grouting of shield segments, replacing the use of cement slurry. The remaining fluid solidified soil can also be transported out and used for backfilling of foundation pit side slopes, backfilling of roof anti-seepage layers, and system grouting, etc., which is superior to existing building materials.

[0005] However, in the actual process of applying mud cakes to the technology of solidified soil, the processes of transportation, metering, and stirring are very unsmooth. Compared with the fluid solidified soil formed by modulating with sand and soil, the formation of the fluid solidified soil made from mud cakes takes a long time, resulting in a high equipment cost, and the insufficient mixing uniformity affects the properties of the fluid solidified soil, etc. Summary of the Invention

[0006] In order to solve the problems of long formation time and insufficient mixing uniformity during the process of making fluid solidified soil from shield waste muck mud, the present invention provides a method for making fluid solidified soil from mud cakes, which only adds a mud cake drying process to reduce the moisture content of the mud cakes, thereby increasing the concentration of reactants, increasing the reaction rate, and at the same time, it can also physically improve the efficiency of the transportation and stirring processes of the mud cakes, thereby reducing the formation time of the fluid solidified soil made from mud cakes and improving the mixing uniformity during the stirring process.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing fluidized solidified soil from mud cake, in which the slurry is separated by mud-water separation to form a mud cake, the mud cake is dried, the moisture content of the mud cake is reduced to 10%-15%, and the mud cake is poured into a mixer and mixed evenly with a curing agent to form fluidized solidified soil.

[0009] In the above method for preparing fluidized solidified soil from mud cake, the fluidized solidified soil is used for synchronous grouting of shield segments, post-grouting behind the tunnel wall of the mining method, leak plugging grouting, backfilling of foundation trenches, backfilling of underground prefabricated stations, and construction of road and floor structural layers.

[0010] In the above method for preparing fluidized solidified soil from mud cake, the composition of the curing agent includes cement, sodium sulfate and calcium carbonate with a mass ratio of (6-9):(0.5-2):(0.5-2).

[0011] In the above method for preparing fluidized solidified soil from mud cake, the specific gravity of the fluidized solidified soil is greater than 1.5 g / cm 3 .

[0012] In the above method for preparing fluidized solidified soil from mud cake, the viscosity of the fluidized solidified soil > 50 s.

[0013] In the above method for preparing fluidized solidified soil from mud cake, the determination test of the moisture content of the mud cake includes the adhesion test of the mud cake, the dispersibility test of the crushed mud cake and the swelling degree test of the crushed mud cake.

[0014] Furthermore, the adhesion test of the mud cake includes a pipeline transportation test and a mixer stirring test. The mud cake is respectively put into a pipeline transportation simulation device and a small mixer, and the pipeline transportation simulation device and the small mixer are respectively made to work for a certain period of time. The adhered soil is scraped at each test point of the pipeline transportation simulation device and the small mixer, weighed respectively, and the total adhered weight of the pipeline transportation simulation device and the small mixer is calculated respectively.

[0015] Furthermore, the process of the dispersibility test of the crushed mud cake includes: preparing crushed mud cakes with different moisture contents; taking several grams of crushed mud cakes with different moisture contents and putting them into a colorimetric dish containing a certain amount of deionized water, using a magnetic stirrer to stir at a fixed speed for a certain number of minutes to fully disperse the mud cake in water; putting the colorimetric dish containing the dispersion liquid into a spectrophotometer and measuring the transmitted light intensity at a wavelength of 550 nm, and recording the data.

[0016] Further, swelling degree test of the mud cake powder: Prepare mud cake powder with different water contents; accurately weigh a certain mass of the mud cake powder sample and record the initial weight; put the mud cake powder sample into a container, add excessive deionized water, gently stir with a stirring rod or magnetic stirrer to evenly disperse the mud cake powder sample in water, and then let it stand for a period of time; remove the unabsorbed solvent by filtration or centrifugation, leaving the swollen gel-like substance; place the separated swollen mud cake powder sample for a period of time, let its surface dry, and then record the weight after swelling; calculate the swelling degree according to the initial weight and the weight after swelling.

[0017] For the present invention according to the above solution, its beneficial effects are as follows. The present invention only adds a mud cake drying process to reduce the water content of the mud cake, thereby making the process of making fluidized solidified soil from the mud cake smoother, reducing the time-consuming for making the fluidized solidified soil, and improving the formation quality of the fluidized solidified soil.

[0018] The core of this technology lies in the selection of the mud cake material (actually the water content), the configuration of the equipment (which can be compiled by oneself), and the process (selecting uniqueness).

[0019] The production of shield mud cake adopts flocculant precipitation to quickly improve production efficiency. The negative effect is that the water content of the mud cake is too high, unstable, and has high viscosity, forming lumps and being difficult to disperse, making it difficult to measure, transport, and mix in the mixing station to produce fluidized solidified soil. Therefore, the present invention dries the mud cake to a certain water content state. The first purpose is to reduce the bonding ability between particles, making it in a dispersed state, facilitating transportation and measurement. The second purpose is that it is easily soluble in water, facilitating uniform mixing. Specific implementation mode

[0020] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] A method for making fluidized solidified soil from mud cake, where the slurry undergoes mud-water separation to form a mud cake, the mud cake is dried, the water content of the mud cake is reduced to 10%-15%, and the mud cake is poured into a mixer and mixed evenly with a curing agent to form fluidized solidified soil.

[0022] The present invention reduces the water content of the mud cake, making the concentrations of the respective reaction components relatively increased, the contact closer, and the reaction can proceed more rapidly, thereby effectively shortening the formation time of the fluidized solidified soil. In addition, the reduction of the water content reduces the water lumps or mud lumps generated during the mixing process, making the texture of the mud cake easier to control, enabling it to be better mixed evenly with the curing agent, additives, etc., making the mixing process smoother, improving the mixing uniformity of the fluidized solidified soil, and further ensuring the stability of its properties.

[0023] In addition, the mud cake with a high moisture content has high viscosity and is likely to adhere to the inner wall of the pipeline during pipeline transportation. As the transportation process continues, the adhesions in the pipeline gradually increase, which will lead to a reduction in the effective flow area of the pipeline and an increase in the flow resistance of the slurry, thereby affecting the transportation efficiency. At the same time, it will also cause the amount of mud cake actually participating in the stirring to be unstable, and the mud cake will also adhere to the mixer accordingly, resulting in the instability of the amount of mud cake actually participating in the stirring, seriously affecting the mixing uniformity.

[0024] Experiment 1: Mud cake adhesion test.

[0025] Pour the waste soil into the extrusion type slurry separator to obtain a preliminarily formed wet mud cake. Randomly select 3 - 5 small mud cake samples, accurately weigh them with an electronic balance, record as m1, put them into the drying oven, dry them to a constant weight at 105°C ± 5°C, and weigh them again, record as m2. If you want to obtain a mud cake with a moisture content of 35%, assuming the initial mud cake weight m1 = 1000 grams and the moisture content ω0 = 30%, first calculate the dry soil mass ω d = m1×(1 - ω0)= 1000×0.7 = 700 grams. Let the mass of water to be added be x. According to the target moisture content formula: (m1 + x - m d ) / (m1 + x)= 0.35, and the solution is x≈77 grams.

[0026] According to the calculation result, slowly add the required water to the initial mud cake, and fully stir with tools while adding water to ensure uniform distribution of water, obtaining a mixed material. Put the mixed material into the extrusion type slurry separator (with unchanged parameters) again, and extrude a formed mud cake. Select at least 5 samples from different parts of the new mud cake, each sample weighs about 50 grams, and measure the wet weight m 湿 and the dry weight m 干 after drying respectively, and calculate the moisture content ω=(m 湿 - m 干 ) / m 湿 ×100%. If the calculated moisture content is not equal to 35%, calculate the required increase or decrease in the amount of water and soil again according to the deviation, and repeat the steps of drying, adding water and stirring, secondary forming and measurement until the average moisture content of the mud cake samples reaches the standard.

[0027] Finally, the actual moisture content of the mud cake for the test can reach the standard of the target moisture content ±0.5%. According to this standard, prepare mud cakes with different moisture contents, and conduct pipeline transportation tests and mixer stirring tests on the mud cakes with different moisture contents respectively.

[0028] Pipeline transportation test: Put the mud cake into the feeding port of the pipeline transportation simulation device, set a fixed transportation flow rate, pipe diameter, and pipeline inclination angle. After transporting a fixed length (such as 5 meters), stop the transportation, open the pipeline, and observe and record the thickness and weight of the mud cake adhered to the inner wall of the pipeline at 3 equally spaced measurement points (starting section, middle section, and ending section) of the pipeline. Then clean the pipeline to restore it to its original state. (The total mass of the mud cake sample for the test is 500 grams)

[0029] Mixing test with a blender: Put the mud cake into a small blender and stir at a fixed speed for 5 minutes. After stopping the machine, observe the adhesion conditions at 6 different positions such as the blender blades and the inner wall (3 positions for the blades and 3 positions for the inner wall, and the material taking position is fixed). Scrape off the adhered mud cake and weigh it separately, and then sum up to obtain the total adhesion weight. (The total mass of the mud cake sample for the test is 500 grams)

[0030] The data of the above two tests are shown as follows.

[0031]

[0032]

[0033] From the above data, it can be seen that as the moisture content of the mud cake increases, the average adhesion weight generally shows an upward trend, but it is not a linear growth. In the moisture content range of 1% - 10%, the total adhesion weight increases relatively smoothly; in the moisture content range of 10% - 15%, the total adhesion weights are relatively close, and the adhesion performance is relatively stable, without significant differences in adhesion weight due to small changes in moisture content. In the moisture content range of 15% - 20%, the average adhesion weight increases significantly. When the moisture content exceeds 20%, the total adhesion weight increases significantly, and the adhesion performance deteriorates severely at high moisture content.

[0034] The water in the mud cake with high moisture content makes the cohesive force between the mud cake particles weak. During the mixing process, it is difficult for the mud cake particles to disperse quickly and come into full contact with other solidifying materials and react. After reducing the moisture content of the mud cake, the cohesive force between the mud cake particles is enhanced, and it is easier to disperse and more uniform during mixing. In this way, it can be more quickly and evenly mixed with materials such as curing agents, accelerating the curing reaction, and thus shortening the formation time.

[0035] Test two: Mud cake dispersion test.

[0036] Prepare mud cakes with different water contents in the same way as in Experiment 1, and use a hammer mill to crush the mud cakes into crushed mud cake materials with the same average particle size. Take 10 g of the crushed mud cake materials with different water contents and put them into a colorimetric dish containing a fixed amount (100 ml) of deionized water. Use a magnetic stirrer to stir at a fixed speed (500 r / min) for 15 minutes to fully disperse the crushed mud cake materials in water. Put the colorimetric dish containing the dispersion into a spectrophotometer and measure the transmitted light intensity at a wavelength of 550 nm, and record the data. Each sample is measured 3 times, and the average value is taken as the measurement result of the sample.

[0037] Water content (%) Average value of transmitted light intensity (relative unit) 1 90.0 3 86.5 5 83.0 7 78.0 9 72.0 10 68.0 12 62.0 14 54.0 16 52.0 18 57.0 20 63.0 22 71.0 23 75.0 25 85.0 27 93.0 30 105.0 32 113.0 35 125.0 37 135.0 40 150.0 42 160.0 45 175.0

[0038] It can be seen that in the water content range of 1% - 15% of the mud cake, the transmitted light intensity gradually decreases, and the dispersibility increases. After the water content is greater than 15%, the transmitted light intensity rises, and the dispersibility decreases. At about 25%, the transmitted light intensity rises significantly, and the dispersibility deteriorates sharply. After the water content is greater than 25%, the transmitted light intensity continues to rise, and the decrease in dispersibility is greater than that between 15% - 25%.

[0039] The mud cake will undergo a swelling reaction when it comes into contact with water or other liquids. If the swelling degree is too small, due to swelling, the volume of the mud cake particles increases, the specific surface area of the mud cake is relatively small, the contact area between the mud cake and substances such as curing agents and water is limited, the chemical reaction rate is restricted, and if the swelling degree is too small, it is difficult for water to penetrate into the interior of the mud cake particles, and the mud cake cannot be fully wetted and softened, and the substances inside the mud cake cannot be effectively dissolved and dispersed, thus affecting the formation rate of the fluidized solidified soil; but if the swelling degree is too large, the whole system becomes too soft and dilute, the concentration of the curing agent decreases relatively, resulting in a slowdown in the hydration reaction rate, and the overly swollen mud cake particles may agglomerate due to changes in surface charge and hydration film, hindering the contact and reaction between the curing agent and water, thereby increasing the stirring time and input energy, and thus leading to a slowdown in the formation rate of the fluidized solidified soil.

[0040] Experiment 3: Swelling degree test.

[0041] Prepare mud cakes with different water contents in the same way as in Experiment 1, and use a hammer mill to crush the mud cakes into crushed mud cake materials with the same average particle size. Accurately weigh a certain mass (such as 100 g) of the crushed mud cake material sample and record the initial weight as m1. Put the crushed mud cake material sample into a container, add an excessive amount of deionized water, and gently stir it with a stirring rod or a magnetic stirrer to evenly disperse the crushed mud cake material sample in water, and then let it stand for a period of time (about 30 minutes). Remove the unabsorbed solvent by filtration or centrifugation, leaving the swollen gel-like substance. Let the separated swollen crushed mud cake material sample stand for a period of time until its surface is dry, and then record the swollen weight m2. Calculate the swelling degree from the initial weight and the swollen weight, that is

[0042]

[0043] Among them, S is the degree of swelling.

[0044]

[0045] From the above data, it can be seen that the degree of swelling reaches the highest value at a water content of 15%, and it can be considered that the degree of swelling of the mud cake is the best at this water content.

[0046] Test Four: The time-consuming test of making fluid-solidified soil from the mud cake.

[0047] Prepare mud cakes with different water contents in the same way as in Test One. Accurately weigh a certain mass of the mud cake, add the mud cake into the mixer, and start timing. During the mixing process, add a certain amount of water and curing agent until it is evenly mixed, then stop timing and record the cumulative time. (Usually, the personal feeling of the tester is used to judge whether it is evenly mixed. Then, after stopping the mixing, take a sample and weigh it, calculate the specific gravity with water, and then judge whether the specific gravity reaches 1.67. If it reaches, it is considered that the fluid-solidified soil is formed and there is no need to mix anymore. If it does not reach, restart the mixer and continue timing. If it exceeds 1.67, start preparing the fluid-solidified soil from the mud cake again. Usually, the specific gravity of 1.67 is determined by the ratio of water to the mud cake, and the influence of the curing agent and the mixing time is relatively small. Therefore, this test is basically determined by the feeling of the construction personnel like on-site construction. Further, the fluid-solidified soil can also be tested by slump test, uniformity test and setting time test to see if it meets the standard requirements, construction requirements or the requirements during the proportion design, and determine whether it is made according to the test results, so as to determine the making time.)

[0048] Water content (%) Manufacturing time (seconds) 1 239 3 215 5 184 7 169 9 148 10 123 12 124 14 132 16 124 18 133 20 142 22 170 23 184 25 204 27 228 30 256 32 286 35 318 37 351 40 372 42 383 45 402

[0049] It can be concluded that within the range of water content from 10% to 20%, the formation time of making fluid-solidified soil from the mud cake is shorter.

[0050] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing fluidized solidified soil from mud cakes, characterized in that: The mud is separated into mud cakes through mud-water separation, and the mud cakes are dried to reduce the moisture content of the mud cakes to 10%-15%. The mud cakes are poured into a mixer and mixed evenly with a curing agent to form fluidized solidified soil.

2. The method for preparing fluidized solidified soil from mud cake according to claim 1, characterized in that: Fluidized solidified soil is used for synchronous grouting of shield segments, grouting behind the mining tunnel wall, plugging grouting, backfilling of fertilizer troughs, backfilling of underground prefabricated stations, and construction of road and floor structure layers.

3. The method for preparing fluidized solidified soil from mud cake according to claim 1, characterized in that: The curing agent comprises cement, sodium sulfate and calcium carbonate in a mass ratio of (6-9):(0.5-2):(0.5-2).

4. The method for preparing fluidized solidified soil from mud cake according to claim 1, characterized in that: The specific gravity of fluidized solidified soil is greater than 1.5g / cm 3 .

5. The method for preparing fluidized solidified soil from mud cake according to claim 1, characterized in that: The viscosity of fluidized solidified soil is >50s.

6. The method for preparing fluidized solidified soil from mud cake according to claim 1, characterized in that: The tests for determining the moisture content of mud cake include the adhesion test of mud cake, the dispersibility test of mud cake crushed material and the swelling test of mud cake crushed material.

7. The method for preparing fluidized solidified soil from mud cake according to claim 6, characterized in that: The adhesion test of the mud cake includes a pipeline transportation test and a mixer stirring test. The mud cake is placed in a pipeline transportation simulation device and a small mixer respectively. The pipeline transportation simulation device and the small mixer are respectively made to work for a certain period of time. The adhered soil is scraped off at each test point of the pipeline transportation simulation device and the small mixer, and weighed respectively. The total adhesion weight of the pipeline transportation simulation device and the small mixer is calculated.

8. The method for preparing fluidized solidified soil from mud cake according to claim 6, characterized in that: The process of the dispersibility test of the mud cake crushed material includes: preparing mud cake crushed materials with different moisture contents; taking several grams of mud cake crushed materials with different moisture contents, putting them into a cuvette filled with a certain amount of deionized water, and using a magnetic stirrer to stir at a fixed speed for several minutes to fully disperse the mud cake in the water; placing the cuvette containing the dispersion into a spectrophotometer, measuring the intensity of the transmitted light at a wavelength of 550nm, and recording the data.

9. The method for preparing fluidized solidified soil from mud cake according to claim 1, characterized in that: Swelling degree test of mud cake crushed material: prepare mud cake crushed materials with different water contents; accurately weigh a certain mass of mud cake crushed material samples and record the initial weight; put the mud cake crushed material samples into a container, add excess deionized water, use a stirring rod or magnetic stirrer to gently stir so that the mud cake crushed material samples are evenly dispersed in the water, and then let it stand for a period of time; remove the unabsorbed solvent by filtering or centrifugation, leaving the swollen gel-like substance; let the separated swollen mud cake crushed material samples stand for a period of time to dry their surfaces, and then record the weight after swelling; calculate the swelling degree based on the initial weight and the weight after swelling.

Images