Method for testing expansion and shrinkage characteristics of expansive soil in acidification environment

Abstract

The invention discloses a method for testing expansion and shrinkage characteristics of expansive soil in an acidification environment, and relates to the technical field of expansion and shrinkage characteristic testing. Comprising the following steps: collecting a bentonite test sample, preparing an acid solution with different pH values, soaking the expansive soil test sample into the acid solution, drying the soaked expansive soil test sample, and calculating the expansion and shrinkage coefficient of the expansive soil test sample. The swelling undisturbed soil with different depths is collected and subjected to a series of pretreatment, so that bentonite test samples of soil layers with different depths are obtained and used for subsequent acidification and swelling-shrinkage tests, and it can be ensured that the test samples have representativeness; acid solutions with different pH values are prepared, and acidification soaking and drying are repeatedly carried out on bentonite test samples of soil layers with different depths in different temperature environments, so that the actual acidification environment and the wetting and drying cycle are simulated, and diversified test simulation of the actual environment of the expansive soil is realized; therefore, the reliability of the swelling-shrinkage characteristic test result of the expansive soil is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of expansion and contraction property testing, and in particular to a method for testing the expansion and contraction property of expansive soil in an acidified environment. Background Art

[0002] Expansive soil is a kind of clay with high plasticity. Its main characteristics are swelling when absorbing water, shrinking when losing water, and repeated swelling and shrinking deformation. These characteristics make expansive soil extremely unstable in its natural state. Especially in construction projects, they may cause uneven vertical or horizontal swelling and shrinking deformation of buildings, which in turn may cause displacement, cracking, tilting and even destruction. The swelling and shrinkage characteristic test of expansive soil is to evaluate the behavior of expansive soil during swelling and shrinkage when losing water. These tests are crucial to understanding the engineering properties of expansive soil because they directly affect the stability and safety of buildings and infrastructure.

[0003] An acidified environment refers to a state in which the pH value in the environment decreases, that is, the acidity increases. This phenomenon can occur at different scales, from small local areas (such as soil and lakes) to global ocean and atmospheric systems. The formation of an acidified environment is usually closely related to human activities, but it may also be caused by natural processes. Testing the swelling and shrinkage characteristics of expansive soil in an acidified environment aims to evaluate and understand the effects of acidic conditions on the physical and chemical properties of expansive soil. Understanding the effects of acidic environments on the swelling and shrinkage characteristics of expansive soil will help develop new improvement technologies and materials. For example, using industrial waste for soil improvement not only solves the problem of expansive soil, but also promotes the recycling of resources.

[0004] Most of the existing methods for testing the swelling and shrinkage characteristics of expansive soil have a single process. The expansive soil samples obtained before the test are prone to differences in physical and chemical properties due to the limitations of the sampling process, so that the expansive soil samples obtained cannot fully represent the soil characteristics of the engineering site, thereby reducing the accuracy of the swelling and shrinkage characteristics test of the expansive soil. The test results are not representative, and it is difficult to simulate a variety of actual environments during the test, such as soil temperature and pH, and dry-wet cycles in the actual environment, thereby affecting the reliability of the test results, and thus not conducive to effectively managing and reducing the negative impact of expansive soil on engineering projects. Therefore, the present invention proposes a method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment to solve the problems existing in the prior art. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to propose a method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment, which solves the problem that the soil samples obtained by the existing method for testing the swelling and shrinkage characteristics of expansive soil are not representative, and it is difficult to fully simulate the actual conditions on site during the test, resulting in low accuracy and reliability of the test results.

[0006] In order to achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment, comprising the following steps:

[0007] Step 1: Collect the original expansive soil at different depths at the project site, air-dry, crush and sieve the original expansive soil collected at each depth, and sieve out the required particle size specifications to obtain bentonite test samples of soil layers at different depths;

[0008] Step 2: Place the bentonite test samples of different depths in an oven for drying. After drying, divide each bentonite test sample into several equal volumes and measure the initial volume V of each bentonite test sample. 初始 , then use inorganic acid to prepare solutions of different acid strengths, and pour the obtained acid solutions of different pH values ​​into the measuring cylinder;

[0009] Step 3: Soak the equal-volume expansive soil test samples in acidic solutions of different pH values. During the soaking process, adjust the temperature of the acidic solution and measure the volume change of the expansive soil test samples at regular intervals. After the soaking is completed, measure the expanded volume V of the expansive soil test samples. 膨胀后 ;

[0010] Step 4: Take out the soaked expansive soil test sample from the acid solution and dry it in an oven. After drying, measure the volume of the expansive soil test sample again to obtain the shrinkage volume V of the expansive soil test sample. 收缩后 , then repeat the operation in step 3, repeat soaking and drying 2 to 3 times;

[0011] Step 5: According to the initial volume V of the expansive soil test sample 初始 、Volume after expansion 膨胀后 And the volume after contraction V 收缩后 , the expansion rate, shrinkage rate and expansion / contraction coefficient of the expansive soil test samples under different acidification and temperature environments were calculated respectively, so as to analyze the influence of different pH values ​​and temperatures on the expansion / contraction characteristics of the expansive soil according to the calculation results.

[0012] A further improvement is that in step one, the specific steps for collecting the original state of expansive soil are: first conduct a comprehensive survey of the project site, then plan the depth position and number of sampling points based on the results of the on-site survey, and then use a core drill to drill vertically downward in layers to obtain soil samples according to the predetermined sampling depth and number. The drilled soil samples of each layer are placed in different sealed containers for storage and standby, and are marked separately.

[0013] A further improvement is that in step one, the specific steps of air-drying, crushing and sieving the original expansive soil are as follows: first, the collected original expansive soil is naturally air-dried, then the air-dried soil blocks are crushed by a crusher, and then the crushed soil blocks are passed through sieves with different apertures to separate soil samples with the required particle size.

[0014] A further improvement is that in step 2, the expansive soil test sample is dried and the initial volume V is measured. 初始 The specific steps are as follows: first, evenly spread the expansive soil test sample on the tray in the oven, then dry the expansive soil test sample at a temperature of 105-110°C for 20-24 hours, take out the expansive soil test sample after drying, pour it into a measuring cylinder, and measure the initial volume V by reading the measuring cylinder. 初始 .

[0015] A further improvement is that in the step 2, the inorganic acid is selected from one of hydrochloric acid or sulfuric acid, and the specific steps for preparing acidic solutions with different pH values ​​are: first determine the target pH value and final volume of the required acidic solution, then calculate the volume of the required acid and the volume of distilled water according to the target pH value, then use a measuring cylinder to measure a certain amount of acid according to the calculated result, and slowly pour it into a container containing a certain amount of distilled water, stirring while pouring, and after stirring evenly, an acidic solution with the target pH value is obtained, and the above steps are repeated to obtain acidic solutions with different pH values.

[0016] A further improvement is that in the step three, the immersion time of the expansive soil test sample in the acidic solution is 10 to 12 hours, and the temperature of the acidic solution during the immersion of the expansive soil test sample is controlled at 15 to 25°C.

[0017] A further improvement is that in step three, the step of timing measurement of the volume change of the expansive soil test sample is as follows: first record the initial total volume of the mixture after the expansive soil test sample is added with the acid solution, and then record the total volume of the mixture at a frequency of once per hour, ensuring that each measurement is performed at the same time interval, and subtract the initial total volume from the total volume measured each time to obtain the volume change of the expansive soil sample at different time points.

[0018] A further improvement is that in step 5, the expansion rate calculation formula of the expansive soil test sample is:

[0019] Expansion rate (%) = (V 膨胀后 -V 初始 ) / V 初始 ×100

[0020] The shrinkage calculation formula of the expansive soil test sample is:

[0021] Shrinkage (%) = (V 初始 -V收缩后 ) / V 初始 ×100

[0022] The expansion and contraction coefficient calculation formula of the expansive soil test sample is:

[0023] Expansion coefficient = expansion rate / contraction rate.

[0024] The beneficial effects of the present invention are as follows: the present invention collects original expansive soil of different depths and performs a series of pretreatments on the expansive soil to obtain bentonite test samples of soil layers of different depths for subsequent acidification and swelling and shrinkage tests, thereby ensuring that the test samples are representative, thereby improving the accuracy of the swelling and shrinkage characteristic test of the expansive soil to a certain extent, and by configuring acidic solutions of different pH values ​​and repeatedly performing acidification immersion and drying on the bentonite test samples of soil layers of different depths under different temperature environments, thereby simulating an actual acidification environment and a dry-wet cycle, achieving diversified test simulations of the actual environment of the expansive soil, thereby ensuring the reliability of the swelling and shrinkage characteristic test results of the expansive soil, being conducive to effectively managing and reducing the negative impact of the expansive soil on engineering projects, and worthy of wide promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 It is a flow chart of a method for testing the swelling and shrinking characteristics of expansive soil in an acidified environment according to the present invention. DETAILED DESCRIPTION

[0027] 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.

[0028] Expansive soil has various causes, including residual, slope accumulation, alluvial, flood accumulation, lacustrine, marine, and glacial accumulation. Among them, residual, alluvial, and lacustrine are the most common. They were mainly formed in the Tertiary System and the entire Quaternary Period. The material sources include residual expansive soil formed by the weathering, alteration, and leaching of igneous rocks, sedimentary rocks, and metamorphic rocks, as well as slope deposits formed under the action of gravity. In summary, expansive soil is a special soil body. Its complex physical and chemical properties have brought many challenges to engineering construction. The comprehensive use of a variety of prevention and control measures can effectively reduce the impact of expansive soil on engineering and the environment.

[0029] In an acidic environment, the expansibility of expansive soil will change. The limit expansion rate of expansive soil and the maximum vertical stress affecting expansive soil will increase with the increase of environmental acidity. This is because the pH value of soil in an acidic environment is less than 7, and the surface of soil particles carries positive charges, which makes it easy for negatively charged soil particles to adsorb on the surface of positively charged particles, thus increasing the expansibility of soil.

[0030] The main purpose of the swelling and shrinkage test of expansive soil is to evaluate and understand the behavior of expansive soil during water absorption and expansion and water loss and shrinkage. This is essential to ensure the safety and stability of buildings and infrastructure. It is a key step to ensure safe and sustainable construction in expansive soil areas. Through the swelling and shrinkage test of expansive soil, the negative impact of expansive soil on engineering projects can be effectively managed and mitigated.

[0031] Based on the findings in the prior art, most of the existing methods for testing the swelling and shrinkage characteristics of expansive soil have the problem that the expansive soil samples obtained cannot fully represent the soil characteristics of the engineering site, and it is difficult to simulate a variety of actual environments during the test process.

[0032] Embodiment 1

[0033] Based on the problems existing in the above prior art, see Figure 1 This embodiment provides a method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment, comprising the following steps:

[0034] Step 1: Bentonite test sample collection

[0035] First, conduct a comprehensive survey of the project site to understand information such as soil layer distribution, soil layer depth, groundwater level and historical use. Then, based on the results of the on-site survey, rationally plan the depth location and number of sampling points to ensure that different soil layers and possible heterogeneity are covered. Then, according to the predetermined depth intervals, use a core drill to vertically drill downward to obtain the original soil of the expansive soil in layers to avoid unnecessary disturbance of the soil samples. The drilled soil samples of each layer are placed in different sealed containers for storage and are marked separately to ensure that the soil samples will not be overly affected by the external environment. The original soil can reflect the natural structure and physical properties of the soil and is more suitable for testing to ensure that the samples are representative.

[0036] The collected expansive soil is evenly spread in a well-ventilated place without direct sunlight to dry naturally to avoid dust and impurity pollution, and then the air-dried soil is crushed by a crusher. Then the crushed soil is passed through sieves with different apertures to separate and collect the particle size specifications required for the test, and stored for later use to obtain bentonite test samples of different depths of soil layers for subsequent testing;

[0037] Step 2: Prepare acidic solutions with different pH values

[0038] First, the bentonite test samples of different depths of soil layers obtained in step 1 are evenly laid on the tray in the oven to ensure that the samples are not stacked so that the heat is evenly distributed. Then, the expanded soil test samples are dried at a temperature of 105°C for 20 hours. After drying, each expanded soil test sample is evenly divided into 3 parts. The bentonite test sample of each depth in step 1 is evenly divided into 3 parts to correspond to the subsequent three acidic solutions with different pH values. Then, the initial volume V of each part is measured. 初始 , and record;

[0039] Then determine the target pH value and final volume of the required acidic solution, and then calculate the required volume of hydrochloric acid and the volume of distilled water according to the target pH value, then use a measuring cylinder to accurately measure the calculated volume of hydrochloric acid and the volume of distilled water, and pre-place the distilled water in a container, and then slowly pour the measured hydrochloric acid into the measured distilled water, stirring while pouring to prevent violent reaction and splashing, and after stirring evenly, obtain an acidic solution with a target pH value, repeat the above steps to obtain three acidic solutions with different pH values, pour them into measuring cylinders, and use them as acidification environments for standby use. The number of measuring cylinders filled with acidic solutions corresponds to the number of each bentonite test sample;

[0040] Step 3: Soak the expansive soil test sample in an acid solution

[0041] The expansive soil test samples after the equal volume distribution in step 2 were respectively placed in acidic solutions with different pH values ​​and soaked for 10 hours to simulate the acidified environment. During the soaking process, the temperature of the acidic solution was regulated and controlled at 15° C. to simulate the effect of temperature changes in the natural environment on soil expansion and contraction;

[0042] During the soaking process, the volume change of the expansive soil test sample is measured regularly until the soaking is completed, and the expanded volume V of the expansive soil test sample is measured. 膨胀后 The specific steps are as follows: first record the initial total volume of the mixture after the acid solution is added to the expansive soil test sample, then record the total volume of the mixture once an hour, ensuring that each measurement is performed at the same time interval, and subtract the initial total volume from the total volume measured each time to obtain the volume change of the expansive soil sample at different time points. Timed measurement can provide information on the expansion rate, that is, the speed at which the soil sample expands. Continuous measurement can reveal the dynamic characteristics of the expansion process, including the starting point, peak value and stable period of the expansion, which helps to understand whether the acidic environment accelerates or inhibits the expansion process, and how this effect changes over time;

[0043] Step 4: Dry the soaked expansive soil test sample

[0044] After the expansive soil test sample in step 3 is soaked, the expansive soil test sample is taken out from the acid solution and dried in an oven. After drying, the volume of the expansive soil test sample is measured again to obtain the shrinkage volume V of the expansive soil test sample. 收缩后 Then repeat the operation in step 3, and soak and dry the expansive soil test sample twice to simulate the dry-wet cycle in the actual environment;

[0045] Step 5: Calculate the expansion and contraction coefficient of the expansive soil test sample

[0046] According to the initial volume V of the expansive soil test sample in step 2 初始 , the volume V of the expansive soil test sample after expansion in step 3 膨胀后 And the volume V of the expansive soil test sample after shrinkage in step 4 收缩后 , respectively calculate the expansion rate, contraction rate and expansion / contraction coefficient of the expansive soil test sample under different acidification and temperature environments, where the expansion rate calculation formula is:

[0047] Expansion rate (%) = (V 膨胀后 -V 初始 ) / V 初始 ×100

[0048] The shrinkage calculation formula is:

[0049] Shrinkage (%) = (V 初始 -V 收缩后 ) / V 初始 ×100

[0050] The expansion coefficient calculation formula is:

[0051] Expansion coefficient = expansion rate / contraction rate

[0052] Finally, based on the calculation results, the influence of different pH values ​​and temperatures on the swelling and shrinkage characteristics of expansive soil is analyzed.

[0053] Embodiment 2

[0054] Based on the problems existing in the above prior art, see Figure 1 This embodiment provides a method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment, comprising the following steps:

[0055] Step 1: Bentonite test sample collection

[0056] First, conduct a comprehensive survey of the project site to understand information such as soil layer distribution, soil layer depth, groundwater level and historical use. Then, based on the results of the on-site survey, rationally plan the depth location and number of sampling points to ensure that different soil layers and possible heterogeneity are covered. Then, according to the predetermined depth intervals, use a core drill to vertically drill downward to obtain the original soil of the expansive soil in layers to avoid unnecessary disturbance of the soil samples. The drilled soil samples of each layer are placed in different sealed containers for storage and are marked separately to ensure that the soil samples will not be overly affected by the external environment. The original soil can reflect the natural structure and physical properties of the soil and is more suitable for testing to ensure that the samples are representative.

[0057] The collected expansive soil is evenly spread in a well-ventilated place without direct sunlight to dry naturally to avoid dust and impurity pollution, and then the air-dried soil is crushed by a crusher. Then the crushed soil is passed through sieves with different apertures to separate and collect the particle size specifications required for the test, and stored for later use to obtain bentonite test samples of different depths of soil layers for subsequent testing;

[0058] Step 2: Prepare acidic solutions with different pH values

[0059] First, the bentonite test samples of different depths of soil layers obtained in step 1 are evenly laid on the tray in the oven to ensure that the samples are not stacked so that the heat is evenly distributed. Then, the expanded soil test samples are dried at a temperature of 110°C for 24 hours. After drying, each expanded soil test sample is evenly divided into 5 parts. The bentonite test sample of each depth in step 1 is evenly divided into 5 parts to correspond to the subsequent three acidic solutions with different pH values. Then, the initial volume V of each part is measured. 初始 , and record;

[0060] Then determine the target pH value and final volume of the required acidic solution, and then calculate the required volume of sulfuric acid and the volume of distilled water according to the target pH value, then use a measuring cylinder to accurately measure the calculated volume of sulfuric acid and the volume of distilled water, and pre-place the distilled water in a container, and then slowly pour the measured sulfuric acid into the measured distilled water, stirring while pouring to prevent violent reaction and splashing, and after stirring evenly, obtain an acidic solution with a target pH value, repeat the above steps to obtain three acidic solutions with different pH values, pour them into measuring cylinders, and use them as acidification environments for standby use. The number of measuring cylinders filled with acidic solutions corresponds to the number of bentonite test samples;

[0061] Step 3: Soak the expansive soil test sample in an acid solution

[0062] The expansive soil test samples after the equal volume distribution in step 2 were respectively placed in acidic solutions with different pH values ​​and soaked for 12 hours to simulate the acidified environment. During the soaking process, the temperature of the acidic solution was regulated and controlled at 25° C. to simulate the effect of temperature changes in the natural environment on soil expansion and contraction;

[0063] During the soaking process, the volume change of the expansive soil test sample is measured regularly until the soaking is completed, and the expanded volume V of the expansive soil test sample is measured. 膨胀后 The specific steps are as follows: first record the initial total volume of the mixture after the acid solution is added to the expansive soil test sample, then record the total volume of the mixture once an hour, ensuring that each measurement is performed at the same time interval, and subtract the initial total volume from the total volume measured each time to obtain the volume change of the expansive soil sample at different time points. Timed measurement can provide information on the expansion rate, that is, the speed at which the soil sample expands. Continuous measurement can reveal the dynamic characteristics of the expansion process, including the starting point, peak value and stable period of the expansion, which helps to understand whether the acidic environment accelerates or inhibits the expansion process, and how this effect changes over time;

[0064] Step 4: Dry the soaked expansive soil test sample

[0065] After the expansive soil test sample in step 3 is soaked, the expansive soil test sample is taken out from the acid solution and dried in an oven. After drying, the volume of the expansive soil test sample is measured again to obtain the shrinkage volume V of the expansive soil test sample. 收缩后 , and then repeat the operation in step 3, repeatedly immersing and drying the expansive soil test sample 3 times to simulate the dry-wet cycle in the actual environment;

[0066] Step 5: Calculate the expansion and contraction coefficient of the expansive soil test sample

[0067] According to the initial volume V of the expansive soil test sample in step 2 初始 , the volume V of the expansive soil test sample after expansion in step 3 膨胀后And the volume V of the expansive soil test sample after shrinkage in step 4 收缩后 , respectively calculate the expansion rate, contraction rate and expansion / contraction coefficient of the expansive soil test sample under different acidification and temperature environments, where the expansion rate calculation formula is:

[0068] Expansion rate (%) = (V 膨胀后 -V 初始 ) / V 初始 ×100

[0069] The shrinkage calculation formula is:

[0070] Shrinkage (%) = (V 初始 -V 收缩后 ) / V 初始 ×100

[0071] The expansion coefficient calculation formula is:

[0072] Expansion coefficient = expansion rate / contraction rate

[0073] Finally, based on the calculation results, the influence of different pH values ​​and temperatures on the swelling and shrinkage characteristics of expansive soil is analyzed.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment, characterized in that: The following steps are involved: Step 1: Collect the original expansive soil at different depths at the project site, air-dry, crush and sieve the original expansive soil collected at each depth, and sieve out the required particle size specifications to obtain bentonite test samples of soil layers at different depths; Step 2: Place the bentonite test samples of different depths in an oven for drying. After drying, divide each bentonite test sample into several equal volumes and measure the initial volume V of each bentonite test sample. 初始 , then use inorganic acid to prepare solutions of different acid strengths, and pour the obtained acid solutions of different pH values ​​into the measuring cylinder; Step 3: Soak the equal-volume expansive soil test samples in acidic solutions of different pH values. During the soaking process, adjust the temperature of the acidic solution and measure the volume change of the expansive soil test samples at regular intervals. After the soaking is completed, measure the expanded volume V of the expansive soil test samples. 膨胀后 ; Step 4: Take out the soaked expansive soil test sample from the acid solution and dry it in an oven. After drying, measure the volume of the expansive soil test sample again to obtain the shrinkage volume V of the expansive soil test sample. 收缩后 , then repeat the operation in step 3, repeat soaking and drying 2 to 3 times; Step 5: According to the initial volume V of the expansive soil test sample 初始 、Volume after expansion 膨胀后 And the volume after contraction V 收缩后 , the expansion rate, shrinkage rate and expansion / contraction coefficient of the expansive soil test samples under different acidification and temperature environments were calculated respectively, so as to analyze the influence of different pH values ​​and temperatures on the expansion / contraction characteristics of the expansive soil according to the calculation results.

2. The method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment according to claim 1, characterized in that: In the step 1, the specific steps for collecting the original state of the expansive soil are: first conduct a comprehensive survey of the project site, then plan the depth position and number of sampling points based on the results of the on-site survey, and then use a core drill to drill vertically downward to obtain soil samples in layers according to the predetermined sampling depth and number. The drilled soil samples of each layer are placed in different sealed containers for storage and standby use, and are marked separately.

3. The method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment according to claim 1, characterized in that: In the step 1, the specific steps of air-drying, crushing and sieving the original expansive soil are: firstly, the collected original expansive soil is naturally air-dried, then the air-dried soil blocks are crushed by a crusher, and then the crushed soil blocks are passed through sieves with different apertures to separate soil samples with the required particle size.

4. The method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment according to claim 1, characterized in that: In step 2, the expansive soil test sample is dried and the initial volume V is measured. 初始 The specific steps are as follows: first, evenly spread the expansive soil test sample on the tray in the oven, then dry the expansive soil test sample at a temperature of 105-110°C for 20-24 hours, take out the expansive soil test sample after drying, pour it into a measuring cylinder, and measure the initial volume V by reading the measuring cylinder. 初始 .

5. The method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment according to claim 1, characterized in that: In the step 2, the inorganic acid is selected from one of hydrochloric acid and sulfuric acid. The specific steps of preparing acidic solutions with different pH values ​​are: first determine the target pH value and final volume of the required acidic solution, then calculate the volume of the required acid and the volume of distilled water according to the target pH value, then use a measuring cylinder to measure a certain amount of acid according to the calculated result, and slowly pour it into a container containing a certain amount of distilled water, stirring while pouring, and obtaining an acidic solution with the target pH value after stirring evenly, and repeat the above steps to obtain acidic solutions with different pH values.

6. The method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment according to claim 1, characterized in that: In the step 3, the expansive soil test sample is immersed in the acid solution for 10 to 12 hours, and the temperature of the acid solution is controlled at 15 to 25° C. during the immersion of the expansive soil test sample.

7. The method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment according to claim 1, characterized in that: In step three, the timed measurement step for the volume change of the expansive soil test sample is as follows: first record the initial total volume of the mixture after the expansive soil test sample is added with the acid solution, then record the total volume of the mixture at a frequency of once per hour, ensure that each measurement is performed at the same time interval, and subtract the initial total volume from the total volume measured each time to obtain the volume change of the expansive soil sample at different time points.

8. The method for testing the swelling and shrinkage characteristics of expansive soil in an acidified environment according to claim 1, characterized in that: In step 5, the expansion rate calculation formula of the expansive soil test sample is: Expansion rate (%) = (V 膨胀后 -V 初始 ) / V 初始 ×100 The shrinkage calculation formula of the expansive soil test sample is: Shrinkage (%) = (V 初始 -V 收缩后 ) / V 初始 ×100 The expansion and contraction coefficient calculation formula of the expansive soil test sample is: Expansion coefficient = expansion rate / contraction rate.

Images