Cold region road anti-seepage repairing method based on PCMs-MICP coupling effect

Abstract

The invention discloses a cold region road anti-seepage repair method based on a PCMs-MICP coupling effect, and the method specifically comprises the steps: filling a roadbed with a filler, and carrying out geological survey on an upper base layer of a road inclined plane; testing permeability parameters of the base aggregate, and determining the usage amount of bacterial liquid; the geotextile is treated, microorganisms are adsorbed on the geotextile in a soaking mode, and a tracer agent is sprayed on the surface of the geotextile before soaking; the adsorption effect is detected by utilizing a tracer agent; in addition, a tracing test is conducted in the drill hole; laying the soaked geotextile on the surface of the upper base layer; and a phase change energy storage plate is laid on the geotextile. According to the method, the stability of the temperature between the upper base layer of the roadbed and the surface of the road is maintained by heat absorption and release in the PCMs phase change process, so that the MICP is controlled to be at a suitable temperature for a long time, a large amount of CaCO3 is generated on the surface of the upper base layer to form an impermeable layer, and meanwhile, the bacteria move towards the high-temperature direction due to the thermotaxis of the bacteria so as to repair the cracks of the roadbed.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnics for road engineering, and particularly relates to a method for anti-seepage repair of cold-region roads based on the coupling effect of PCMs-MICP. Background Art

[0002] The strength of the road surface layer is easily affected by freeze-thaw cycles, leading to road damage. In addition, the pore water in the subgrade filler freezes and thaws repeatedly as the road temperature rises and falls, triggering the phenomenon of pore water frost heave, resulting in cracks inside the subgrade and their subsequent expansion, and the road stability is damaged. The waterproof performance of the road surface layer also decreases due to freeze-thaw action, resulting in frequent leakage problems. Therefore, a higher-level waterproof and drainage scheme is required during construction, which increases the cost of cold-region road construction. When the road temperature is too high or too low, the service life of various materials is reduced, seriously affecting the function of cold-region roads.

[0003] Chinese Patent Application (Application No.: 202310585062.2, Publication No.: CN116927814A, Publication Date: May 23, 2023) discloses a method for reducing seepage, strengthening and insulating cold-region tunnels based on PCMs-MICP. By means of grouting, a slurry containing microorganisms is injected into the tunnel lining to solve the problems of reduced strength and increased permeability of the tunnel surrounding rock caused by the freeze-thaw cycle of pore water in cold-region tunnels. However, freeze-thaw damage is fundamentally caused by the volume change caused by the phase change of water when the temperature changes, which damages the subgrade base. Therefore, this solution cannot fundamentally solve the damage problem caused by freeze-thaw cycles. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for anti-seepage repair of cold-region roads based on the coupling effect of PCMs-MICP, which solves the problem of increased permeability after cracks are formed in cold-region roads due to repeated temperature changes in the prior art.

[0005] The technical solution adopted by the present invention is a method for anti-seepage repair of cold-region roads based on the coupling effect of PCMs-MICP, which is specifically implemented according to the following steps:

[0006] Step 1: Fill the subgrade with filler. After the subgrade filler is completed, investigate the upper base layer of the road slope.

[0007] Step 2: Test the penetration parameters of the base aggregate and determine the dosage of the bacterial liquid.

[0008] Step 3: Treat the geotextile. Soak it to make microorganisms adsorbed on the geotextile. Spray a tracer on its surface before soaking; and use the tracer to test the adsorption effect; in addition, conduct a tracer test inside the borehole.

[0009] Step 4: Lay the soaked geotextile on the surface of the upper base layer.

[0010] Step 5: Lay the phase change energy storage board on the geotextile.

[0011] The features of the present invention also lie in that

[0012] In Step 2, specifically:

[0013] First, determine the positions for borehole tests on the upper base course of the road slope surface, and test the initial permeability coefficient of the boreholes through in-situ hydraulic tests; the bacterial solution is Bacillus pasteurii, and the OD 600 value is configured according to the research results of Step 1, and it is used after culturing on-site for 20 - 24 hours. The cementing solution is a mixed solution of CaCl 2 and urea with a concentration of 1.0M - 2.0M, where M CaCl2 : M 尿素溶液 = 1:1. The prepared bacterial solution and cementing solution are sealed and reserved for use; according to the survival properties of bacteria and environmental characteristics, judge the adsorption effect of the geotextile by comparing the change in the concentration of the bacterial solution before and after soaking. Based on the principle of mass conservation, calculate the adsorption amount by measuring the change in concentration before and after adsorption. The bacterial adsorption amount on the surface of unit mass geotextile is calculated by the formula q = (C 0 - C) / m×V; where q is the adsorption amount, C 0 is the initial concentration, C is the final concentration, m is the mass of the geotextile, and V is the volume of the bacterial solution used for soaking; the CaCO 3 content that can be generated by inferring from the adsorption amount is further used to obtain the improved permeability performance, so as to judge whether further soaking is required.

[0014] In Step 3, specifically:

[0015] Spray the tracer on the surface of the geotextile to understand the adsorption effect of microorganisms on the geotextile through the flow path of the tracer; select whether to spray the bacterial solution on the surface of the geotextile and around the boreholes by monitoring the change in the concentration of the tracer: Observe the water level in the borehole where the tracer is injected before the experiment. First, dissolve the tracer into a solution, that is, a sodium chloride solution with a chloride ion concentration of 10,000 mg / L, then inject the tracer into the borehole and inject clear water to make the tracer enter the aquifer. Conduct a pumping test in the designated borehole and take water samples regularly. It is required to take samples for analysis once every 60 - 120 minutes after the tracer is put in, conduct tracer ion reception detection and make a curve of tracer concentration changing with time to understand the internal fracture water flow field and water flow movement speed of the roadbed, so as to infer the flow rate, and further determine the activity of the microorganisms attached to the geotextile and the repair situation inside the borehole.

[0016] In Step 4, specifically: Lay the soaked geotextile on the surface of the upper base course; for the protruding parts on the surface after the upper base course is filled, repeatedly roll them until they are flat.

[0017] The geotextile is laid and hung by the hot-melt method, that is, the geotextile is first pasted with hot-melt gaskets and then fixed with cement nails by a nail gun.

[0018] In step 5, the phase change energy storage board is composed of EVA board A, n-decanoic acid-n-decanol composite phase change material layer, and EVA board B.

[0019] The mass ratio of the composite phase change material used in the n-decanoic acid-n-decanol composite phase change material layer is m 正癸酸 :m 正癸醇 = 55.40:107.38, the phase change temperature is -5 to 0 °C, and the phase change latent heat is 180 to 220 J / g; after the composite phase change material is prepared, it is mixed with expanded graphite, and then aluminum powder is added by the external admixture method and mixed evenly to finally form the n-decanoic acid-n-decanol composite phase change material layer.

[0020] When laying the phase change energy storage board, for the construction of the lap joint, the width of the EVA board A and the EVA board B is not less than 2.5 m, and a lap joint width of at least 10 cm is set on both sides.

[0021] The beneficial effect of the present invention is that the anti-seepage repair method for cold-region roads based on the PCMs-MICP coupling effect regulates the temperature by laying the phase change material waterproof board (PCMs), thereby promoting the anti-seepage repair of the subgrade soil of cold-region roads by the microbial-induced calcium carbonate technology (MICP). A geotextile adsorbed with a large amount of Bacillus pasteurii bacteria solution and reaction solution (a mixed solution of urea and calcium chloride) is arranged on the surface of the upper base course. A large number of bacteria will adhere to the surface of the base course aggregate, and then under the condition of continuously providing a calcium source, the generated CaCO 3 precipitation will fill the cracks developed inside the base course, reduce the porosity of the cracks, and then effectively reduce the crack permeability and reinforce the subgrade. The composite phase change material is placed between two layers of empty waterproof boards, and after compaction, a phase change energy storage board is obtained. The phase change energy storage board is laid outside the geotextile. When the external temperature is lower than the phase change temperature, the phase change material undergoes a phase change and releases the previously absorbed heat energy to raise the temperature, reaching the comfortable range for bacteria survival, inducing the movement direction of bacteria and promoting the formation of CaCO 3 precipitation to form an anti-seepage layer while repairing the cracks, achieving the purpose of waterproof repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the anti-seepage repair method for cold-region roads based on the PCMs-MICP coupling effect of the present invention;

[0023] Figure 2 is an assembly schematic diagram of the anti-seepage repair technology for cold-region roads of the present invention;

[0024] Figure 3 Schematic layout diagram of geotextile in the method of the present invention;

[0025] Figure 4 Schematic diagram of the laying and unfolding of the phase change energy storage board in the method of the present invention;

[0026] Figure 5 Schematic diagram of the structure of the phase change energy storage board in the method of the present invention.

[0027] In the figure, 1, subbase; 2, lower base course; 3, upper base course; 4, geotextile; 5, phase change energy storage board; 6, road surface; 7, gasket; 8, drilling hole; 9, cement nail; 10, hot melt gasket; 11, lapping width; 12, EVA board A; 13, n-decanoic acid - n-decanol composite phase change material layer; 14, EVA board B. Specific embodiments

[0028] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] The anti-seepage repair method for cold region roads based on the PCMs-MICP coupling effect of the present invention has a process as Figure 1 shown, and is specifically implemented according to the following steps:

[0031] Step 1: Fill the roadbed with fillers. After the roadbed filling is completed, conduct a geological survey on the upper base course 3 of the road inclined surface;

[0032] Step 2: Test the penetration parameters of the base course aggregate and determine the dosage of the bacterial solution; specifically:

[0033] Based on the previous geological survey, test the permeability coefficient of the roadbed aggregate through the pumping water test of the drilling hole, and calculate the soaking time of the geotextile, so as to ensure that the MICP can form a complete anti-seepage layer.

[0034] As Figure 2 shown, first determine the position of the drilling test on the upper base course 3 of the road inclined surface. The layout position of the holes understands the base course distribution and aggregate characteristics through geological exploration. Combining the exploration results, engineering design, construction method and safety requirements, and in combination with the laying principle of the geotextile, conduct drilling treatment at a position that largely coincides with the required drilling position. Test the initial permeability coefficient of the drilling hole through the on-site hydraulic test method. The specific steps are as follows: Isolate a certain section of the drilling test section with a water stop device, and then use a water pump or the self-weight of the water column to press water into this section of the drilling hole. The water seeps into the base course through the cracks around the hole wall, and finally the seepage water volume will tend to a stable value. According to the pumping water head, test section length and stable infiltration water volume, judge the permeability of the base course aggregate, expressed by the permeability q. The relationship between the permeability coefficient K and the permeability q is estimated as: K = q × 1.5 × 10 -5 .

[0035] The bacterial solution is Bacillus pasteurianus, OD 600 The value (1.84-4.6) is configured according to the survey results of step 1 and used after 20-24 hours of on-site cultivation. The cementing fluid is CaCl with a concentration of 1.0M-2.0M 2 and urea mixed solution, wherein M CaCl2 :M 尿素溶液 =1:1, and the prepared bacterial solution and cementing solution are packaged for later use. According to the survival properties of bacteria and environmental characteristics, the adsorption effect of geotextiles is judged by comparing the concentration changes of bacterial solution before and after immersion. Based on the principle of mass conservation, the adsorption amount is calculated by measuring the concentration changes before and after adsorption. The bacterial adsorption amount per unit mass of geotextile surface is given by the formula q=(C 0 -C) / m×V. Where q is the adsorption amount, C 0 is the initial concentration, C is the final concentration, m is the mass of the geotextile, and V is the volume of the bacterial solution used for immersion. The amount of CaCO that can be generated can be calculated from the adsorption amount. 3 The content can further be used to determine the permeability that can be improved, thereby determining whether further soaking is needed.

[0036] Step 3, treating the geotextile 4, spraying a tracer on its surface before soaking; soaking the geotextile 4 so that the microorganisms are adsorbed on the geotextile 4, and using the tracer to test the adsorption effect; in addition, a tracer test is performed inside the borehole;

[0037] According to the experimental results of step 2 (considering the repair and plugging of the borehole), the geotextile 4 is immersed in the bacterial solution for a certain period of time, and the adsorption effect of the geotextile 4 is tested; at the same time, the tracer is injected into the test borehole to determine the repair effect on the inside of the borehole;

[0038] The details are as follows:

[0039] Spray the tracer on the surface of the geotextile 4 to understand the adsorption effect of microorganisms on the geotextile 4 through the flow path of the tracer; select the soaking duration of the geotextile 4 by monitoring the change of the tracer concentration. At the same time, inject the tracer into the borehole to understand the flow path of the microorganisms attached to the geotextile inside the borehole through the flow path of the tracer; select whether to spray the bacterial solution on the surface of the geotextile 4 and around the borehole by monitoring the change of the tracer concentration: Observe the water level in the borehole where the tracer is injected before the experiment. First, dissolve the tracer into a solution, that is, a sodium chloride solution with a chloride ion concentration of 10,000 mg / L, and then inject the tracer into the borehole and inject clear water to make the tracer enter the aquifer. Conduct a pumping test in the designated borehole and take water samples regularly. It is required to take samples once every 60 - 120 minutes for analysis after the tracer is put in, conduct tracer ion reception detection and make a curve of the tracer concentration changing with time to understand the fissure water flow field and water flow movement speed inside the subgrade, thereby calculating the flow rate, and further determining the activity of the microorganisms attached to the geotextile 4 and the repair situation inside the borehole;

[0040] Step 4: Lay the soaked geotextile 4 on the surface of the upper base course 3;

[0041] For the protruding parts on the surface after the upper base course 3 is filled, repeatedly roll them until they are flat; use the hot melt method to lay and hang the geotextile 4, that is, on the surface of the upper base course 3, as Figure 3 shown, first stick the geotextile 4 with the hot melt gasket 10, and then use a nail gun to nail and anchor the cement nails. The length of the cement nails 9 shall not be less than 50 mm, and 3 - 4 drill holes 8 are arranged per square meter on average at the top arch, 2 and 2 - 3 drill holes are arranged per square meter on the side wall 2 . In addition, for a road without a slope, relevant structures can be selected to be arranged at the anti - drainage ditch part to achieve a better anti - drainage effect;

[0042] Step 5: Lay the phase - change energy storage board 5 on the geotextile 4;

[0043] As Figure 5 shown, the phase - change energy storage board 5 is composed of an EVA board A12, a capric acid - decanol composite phase - change material layer 13, and an EVA board B14;

[0044] The mass ratio of the composite phase - change material used in the capric acid - decanol composite phase - change material layer 13 is m 正癸酸 : m 正癸醇 = 55.40:107.38, the phase - change temperature is - 5 - 0 °C, and the phase - change latent heat is 180 - 220 J / g. After the composite phase - change material is prepared, it is mixed with expanded graphite in a certain proportion and then added with an appropriate amount of aluminum powder by the external admixture method, and fully mixed with a magnetic stirrer to increase the heat absorption and release amount, and finally form the capric acid - decanol composite phase - change material layer;

[0045] When laying the phase change energy storage board 5, it is hot-melted on the hot-melt gasket 10 using a manual special fusion welder, and the peel strength of the bonded part between the two shall not be less than the tensile strength of the waterproof board; as Figure 4 shown, when constructing the lap joint, for the 1.5-mm-thick EVA board A12 and EVA board B14, the width of each side is not less than 2.5 m, and a lap width 11 of at least 10 cm is provided on both sides of each board.

[0046] The reaction bacteria used in the anti-seepage repair technology provided by the present invention are harmless bacteria naturally present in natural soil, which have the advantages of no pollution, low grouting pressure, good reinforcement effect, low slurry viscosity, easy reaction control, etc.; the phase change material used has good thermal stability after multiple phase change cycles, stable phase change temperature and phase change latent heat, good heat storage and release effect, meets the cost control requirements of cold region road engineering, and does not have toxic corrosiveness, flammability and explosiveness, volatility, etc. during use, and will not cause environmental pollution, meeting the use requirements of green building materials.

[0047] Example 2

[0048] The cold region road anti-seepage repair method based on the PCMs-MICP coupling effect of the present invention has an assembly structure as Figure 2 shown, including a subbase 1, a lower base course 2, and an upper base course 3. A geotextile 4 is laid on the upper base course 3 of the road inclined surface. After the geotextile 4 is laid, a layer of phase change energy storage board 5 is laid above it. The heat absorption and release during the PCMs phase change are used to maintain the temperature stability between the upper base course 3 of the roadbed and the road surface 6, so as to control the MICP to be at an appropriate temperature for a long time. Furthermore, a large amount of CaCO 3 is formed to form an anti-seepage layer. At the same time, due to the thermotaxis of bacteria, they will move towards the direction of high temperature to repair the cracks in the roadbed. This method strengthens the MICP activity by regulating the temperature, prevents the roadbed damage caused by water seepage during freeze-thaw cycles, and repairs the existing cracks.

[0049] Example 3

[0050] The cold region road anti-seepage repair method based on PCMs temperature control for MICP is specifically as follows:

[0051] S1: Investigate the geological environment of the cold region road subgrade. According to the physical and mechanical properties, water stability, and compaction of the filler, divide the roadbed stability into three grades A, B, and C, and select an appropriate concentration of bacterial solution to soak the geotextile according to the grade.

[0052] S2: Based on the previous geological investigation, test the permeability coefficient of the roadbed aggregate through a borehole water pressure test, calculate the soaking duration range of the geotextile, so as to ensure that the MICP can form a complete anti-seepage layer. At the same time, test the effect of the bacterial attachment tracer in the culture medium.

[0053] By regulating the concentration of the bacterial solution, it was found that there was an obvious positive correlation between it and the permeability of the specimen. As the concentration of the bacterial solution increased, the permeability of the specimen showed a gradually weakening trend. When the OD 600 value reached 1.84, the permeability coefficient of the specimen reached the maximum value, which was 9.439×10 -7 . When the concentration of the bacterial solution was further increased to 3.22, the permeability coefficient decreased by 1.903×10 -7 , and the value was 7.536×10 -7 , and the decline rate reached 20.16%. When the concentration of the bacterial solution was further increased to 4.6, the permeability coefficient decreased by 4.228×10 -7 , and the value was 5.211×10 -7 , and the decline rate expanded to 30.85%.

[0054] This research result reveals the significant regulatory effect of the bacterial solution concentration on the permeability of the specimen. The fundamental reason is that at low bacterial solution concentrations, the dispersion degree of microbial cells in the solute is relatively low. The distribution of these cells in the fractured specimen appears relatively sparse, which leads to a limited number of calcium carbonate crystals induced by the MICP process, and its filling efficiency is not very ideal. These factors together result in a decrease in the compactness between quartz sand particles and an increase in pore volume, thus showing a relatively high permeability. On the contrary, when the concentration of the bacterial solution increases, the microbial cells no longer show a dispersed state in the solute, which promotes the MICP reaction to produce more calcium carbonate. These crystals aggregate and cement with each other in a cluster form, and also cement with the quartz sand particles around the fracture, effectively providing filling and cementing effects, thereby improving the hydrogeological properties of the fractured specimen. Thus, while repairing the fracture, the water-insoluble chemical property of CaCO 3 is used to form an anti-seepage layer on the surface of the upper base course.

[0055] When the subgrade grade is A or B, the OD 600 value selected for MICP is 2.29 mol / L; when the subgrade grade is C, the OD 600 value selected for MICP is 4.6 mol / L.

[0056] S3: Based on the occurrence characteristics of the fissures and the surface characteristics of the roadbed, a tracer test is carried out on the drill holes and the surface of the upper base course. Inject the tracer into the drill holes and fissures, analyze the flow path and concentration change of the tracer, and determine the reasonable intake of the bacterial liquid and the reaction liquid: Convert the tracer into a solution (i.e., a sodium chloride solution with a chloride ion concentration of 10,000 mg / L), and inject a certain amount of clear water to enable the tracer to enter the aquifer. Conduct a pumping test in the designated drill hole and take water samples regularly. It is required to take samples for analysis once every 60 minutes after injecting the tracer, conduct tracer ion reception detection and make a curve of tracer concentration changing with time to understand the flow field and flow velocity of the fissure water in the base course, and determine the reasonable injection amount of the bacterial liquid and the reaction liquid;

[0057] S4: Treat the upper base course of the road to ensure it is flat and has no sharp edges. Use a working trolley to fix the geotextile to the predetermined position, and fix it with gaskets 7 or cement nails 9. Lay the phase change energy storage board on the geotextile and fix it on the special hot-melt gasket 10. Carry out double-weld hot melting on the joints between the phase change energy storage boards, and finally conduct an air inflation inspection on the welds to ensure that the weld quality meets the design requirements.

[0058] Regarding the proportion of the phase change composite material layer in the phase change energy storage board, according to the principles of maximizing the phase change latent heat, small supercooling degree, and long phase change time, the final determined mass mixing ratio of the composite phase change material is m 正癸酸 :m 正癸醇 =55.40:107.38, its phase change temperature is -1.778 °C, the phase change latent heat is 231.17 J / g, and the phase change duration is 7050 s.

[0059] By combining MICP with the phase change board of PCMs materials in the present invention, the temperature in the fissures can be maintained within the range suitable for microbial growth throughout the day, providing a good living environment for microorganisms, overcoming the extreme weather conditions of large temperature differences between day and night in alpine regions, accelerating the rate of microbial-induced calcium carbonate precipitation, and realizing the seepage reduction, reinforcement, and heat preservation of roads in alpine regions. The microbial (Bacillus pasteurii) solution and PCMs (n-decanoic acid - n-decanol) materials used in the present invention are all very friendly to the environment, and can achieve engineering application of seepage reduction, reinforcement, and heat preservation of cold-region roads without damaging the environment, realizing the purpose of reinforcing seepage reduction of roadbeds of different grades and keeping the roadbed at a constant temperature under the premise of protecting the construction and surrounding environment.

[0060] Example 4

[0061] The MICP cold-region road anti-seepage repair method based on PCMs temperature control in the present invention, when the environmental temperature range is -30 °C to 30 °C (considering the supercooling problem generated by the phase change material under the influence of the external environment), specifically:

[0062] S1. After the site layout is completed, fill the roadbed with fillers. After the roadbed filling is completed, conduct a geological survey on the upper base course;

[0063] S2. Determine the soaking time of the geotextile in the bacterial solution by means of a borehole water pressure test; and add a tracer to the pre-prepared bacterial solution;

[0064] S3. Treat the geotextile, and soak it to make microorganisms adsorb on the geotextile. Use the tracer to test the adsorption effect, and at the same time conduct a tracer test inside the borehole;

[0065] S4. Lay the geotextile on the surface of the filled upper base course, and lay the phase change energy storage board on the geotextile;

[0066] Among them, the phase change energy storage board is composed of EVA board A, a capric acid-capric alcohol composite phase change material layer, and EVA board B. The mass ratio of the composite phase change material used in the capric acid-capric alcohol composite phase change material layer is m 正癸酸 :m 正癸醇 =55.40:107.38, the phase change temperature is -5 to 0 °C, the phase change latent heat is 180 to 220 J / g. Put the composite phase change material and expanded graphite into a constant temperature stirrer according to the mass ratio m 正癸酸 :m 正癸醇 =55.40:107.38 and stir for 4 h to ensure that the expanded graphite is evenly absorbed; finally, place the shaped phase change particles in the EVA waterproof board with a hollow interior, and the thickness is 30 mm.

[0067] According to the external environment change range, when the environmental temperature is only in the range of -20 °C to 20 °C, change the material ratio of the phase change energy storage board. The composite phase change material and expanded graphite are in the mass ratio of m capric acid:m capric alcohol = 55.40:107.38, and at the same time add 5 wt% aluminum powder, put it into a constant temperature stirrer and stir for 4 h to ensure that the expanded graphite is evenly absorbed and the aluminum powder is fully mixed with it; finally, place the shaped phase change particles in the EVA waterproof board with a hollow interior, and the thickness is 20 mm.

[0068] Example 5

[0069] The MICP cold region road anti-seepage repair method based on PCMs temperature control of the present invention is specifically implemented according to the following steps for the roadbed anti-drainage ditch part when the environmental temperature range is -30 °C to 30 °C (considering the supercooling problem generated by the phase change material affected by the external environment):

[0070] S1. After the site layout is completed, fill the roadbed with fillers. After the roadbed filling is completed, conduct a geological survey on the surface of the anti-drainage ditch;

[0071] S2. Determine the soaking time of the geotextile in the bacterial solution by means of a borehole water pressure test; and add a tracer to the pre-prepared bacterial solution;

[0072] S3. Process the geotextile, adopt the soaking method to make microorganisms adsorb on the geotextile, use a tracer to test the adsorption effect, and conduct a tracer test inside the borehole at the same time;

[0073] S4. Lay the geotextile on the surface of the anti-drainage ditch, and lay the phase change energy storage board on the geotextile;

[0074] Among them, the phase change energy storage board is composed of EVA board A, n-decanoic acid-n-decanol composite phase change material layer, and EVA board B. The mass ratio of the composite phase change material used in the n-decanoic acid-n-decanol composite phase change material layer is m 正癸酸 :m 正癸醇 =55.40:107.38, the phase change temperature is 0 - 5°C, the phase change latent heat is 180 - 220 J / g. Put the composite phase change material and expanded graphite into a constant temperature stirrer according to the mass ratio m n-decanoic acid:m n-decanol = 55.40:107.38 and stir for 4 h to ensure that the expanded graphite is evenly absorbed; finally, place the shaped phase change particles in the EVA waterproof board with a hollow interior, and the thickness is 20 mm.

[0075] According to the external environment change range, when the environmental temperature is only in the range of -20°C to 20°C, change the material ratio of the phase change energy storage board. The composite phase change material and expanded graphite are in accordance with the mass ratio m n-decanoic acid:m n-decanol = 55.40:107.38, and at the same time add 5 wt% aluminum powder, put it into a constant temperature stirrer and stir for 4 h to ensure that the expanded graphite absorbs evenly and the aluminum powder is fully mixed with it; finally, place the shaped phase change particles in the EVA waterproof board with a hollow interior, and the thickness is 20 mm.

[0076] Example 6

[0077] The present invention realizes the anti-seepage repair of cold region roads by the way of temperature control adsorption of microorganisms on the surface of the geotextile by the phase change energy storage board. Microorganisms can generate calcium carbonate precipitation through mineralization. After laying the geotextile adsorbed with Bacillus pasteurii on the surface of the upper base course, a large number of urease bacteria will adhere to the surface of the upper base course and the surface of the fissures; then spray urea and CaCl 2 solution, urea hydrolysis produces CO 3 2- , and finally combines with Ca provided by CaCl 2 solution to generate CaCO 2+ precipitation. The generated CaCO 3 precipitation will fill the fissures developed inside the subgrade soil, reduce the porosity of the fissures, and repair the fissures; then under the temperature control of the phase change energy storage board, a large amount of CaCO 3 precipitation continues to be generated on the surface of the upper base course; 3Form an impermeable layer to further reduce the permeability of the subgrade. After the geotextile is laid, a phase change energy storage board is laid above it. The phase change material used in the phase change energy storage board is a capric acid-capric alcohol composite phase change material, which is a solid-liquid phase change material. The phase change temperature of the capric acid-capric alcohol composite phase change material is -1.89 °C. When it is placed in a cold region environment, when the ambient temperature begins to drop, the temperature of the liquid capric acid-capric alcohol composite phase change material also drops. When the ambient temperature is lower than the solidification phase change temperature of the capric acid-capric alcohol composite phase change material, which is -1.89 °C, the liquid capric acid-capric alcohol composite phase change material begins to transform into a solid state. At this time, the latent heat of phase change stored inside the capric acid-capric alcohol composite phase change material is released until the liquid capric acid-capric alcohol composite phase change material is completely solidified. The phase change in this process is called "solidification heat release", so that microorganisms can still be at a suitable temperature for survival in a cold environment. When the external temperature rises, the solid capric acid-capric alcohol composite phase change material continuously absorbs heat and its temperature gradually increases. When the ambient temperature is greater than or equal to the phase change temperature of the capric acid-capric alcohol composite phase change material, which is -1.89 °C, the capric acid-capric alcohol composite phase change material continues to absorb heat and begins to transform from a solid state to a liquid state. This is a process of qualitative change. At this time, the heat absorbed by the capric acid-capric alcohol composite phase change material will be stored in the form of latent heat to form a phase change cycle, so that the temperature at the lower part of the road surface basically remains unchanged or changes within a small temperature range, realizing the temperature control effect of microbial-induced CaCO 3 . The phase change temperature and latent heat of phase change of this composite phase change material remain stable, having good thermal stability, being recyclable, reducing the use cost, and improving the utilization rate of substances.

Claims

1. A cold region road anti-seepage repair method based on the PCMs-MICP coupling effect, characterized in that: Follow the steps below to implement it: Step 1, fill the roadbed with filler, and after the roadbed filling is completed, conduct a geological survey on the upper base of the inclined surface of the road; Step 2, testing the penetration parameters of the base aggregate and determining the amount of bacterial solution to be used; Step 3, treating the geotextile by soaking it so that the microorganisms are adsorbed on it, spraying a tracer on its surface before soaking; and using the tracer to test the adsorption effect; in addition, a tracer test is performed inside the borehole; Step 4, placing the soaked geotextile on the surface of the upper base; Step 5: Lay the phase change energy storage board on the geotextile.

2. The cold region road anti-seepage repair method based on the PCMs-MICP coupling effect according to claim 1, characterized in that: In the step 2, specifically: First, the location of the borehole test was determined on the upper base of the inclined road surface, and the initial permeability coefficient of the borehole was tested by the on-site hydraulic test method; the bacterial liquid was Bacillus pasteurianus, OD 600 The value is configured according to the survey results of step 1 and used after 20 to 24 hours of on-site cultivation. The cementing liquid is a mixed solution of CaCl2 and urea with a concentration of 1.0M to 2.0M, where M CaCl2 :M 尿素溶液 =1:1, the prepared bacterial solution and cementing solution are packaged for later use; according to the survival properties of bacteria and environmental characteristics, the adsorption effect of geotextiles is judged by comparing the changes in bacterial solution concentration before and after immersion. Based on the principle of mass conservation, the adsorption amount is calculated by measuring the concentration change before and after adsorption. The bacterial adsorption amount per unit mass of geotextile surface is calculated by the formula q=(C0-C) / m×V; wherein q is the adsorption amount, C0 is the initial concentration, C is the final concentration, m is the mass of geotextile, and V is the volume of bacterial solution used for immersion; the CaCO3 content that can be generated is calculated from the adsorption amount, and the permeability that can be improved is further obtained, thereby judging whether further immersion is needed.

3. The cold region road anti-seepage repair method based on the PCMs-MICP coupling effect as claimed in claim 2, characterized in that: In the step 3, specifically: The tracer is sprayed on the surface of the geotextile, and the adsorption effect of the microorganisms on the geotextile is understood through the flow path of the tracer; by monitoring the change of the tracer concentration, it is selected whether to spray the bacterial solution on the surface of the geotextile and around the borehole: before the experiment, the water level in the borehole where the tracer is placed is observed, and the tracer is first converted into a solution, that is, a sodium chloride solution with a chloride ion concentration of 10000 mg / L, and then the tracer is injected into the borehole, and clean water is injected to allow the tracer to enter the aquifer, and a pumping test is carried out in the designated borehole and water samples are taken at regular intervals. It is required to take samples once every 60 to 120 minutes after the tracer is placed for analysis, and the tracer ion reception detection is carried out and a tracer concentration change curve over time is drawn to understand the fissure water flow field and water flow speed inside the roadbed, so as to calculate the flow rate, and then determine the activity of microorganisms attached to the geotextile and the repair situation inside the borehole.

4. The cold region road anti-seepage repair method based on the PCMs-MICP coupling effect as claimed in claim 3, characterized in that: In the step 4, specifically: the soaked geotextile is laid on the surface of the upper base layer; after the upper base layer is filled, the protruding part of the surface is repeatedly rolled until it is flat.

5. The cold region road anti-seepage repair method based on PCMs-MICP coupling effect as claimed in claim 4, characterized in that: The geotextile is laid using the hot melt method, that is, the geotextile is first pasted with a hot melt gasket, and then anchored with cement nails using a nail gun.

6. The cold region road anti-seepage repair method based on PCMs-MICP coupling effect as claimed in claim 4, characterized in that: In step 5, the phase change energy storage plate is composed of an EVA plate A, a decanoic acid-decyl alcohol composite phase change material layer, and an EVA plate B.

7. The cold region road anti-seepage repair method based on PCMs-MICP coupling effect as claimed in claim 6, characterized in that: The mass ratio of the composite phase change material used in the n-decanoic acid-n-decyl alcohol composite phase change material layer is m 正癸酸 :m 正癸醇 =55.40:107.38, the phase change temperature is -5~0℃, and the phase change latent heat is 180~220J / g; after the composite phase change material is prepared, it is mixed with expanded graphite, and then aluminum powder is added by external doping method, mixed evenly, and finally a decanoic acid-decyl alcohol composite phase change material layer is formed.

8. The cold region road anti-seepage repair method based on PCMs-MICP coupling effect as claimed in claim 6, characterized in that: When laying phase change energy storage panels, for the overlap edge construction, the width of EVA board A and EVA board B shall not be less than 2.5m, and an overlap width of at least 10cm shall be set on both sides.

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