A method for calculating the clay content of a soil

Abstract

The present application relates to the technical field of soil particle analysis, and discloses a method for calculating the content of clay particles in soil, which aims to solve the problem of poor accuracy of existing methods, and mainly comprises the following steps: adding a clay sample filtered by a sieve disc into a dispersing agent, oscillating and dispersing to prepare a suspension; performing a particle analysis test on the suspension by using a sedimentation analysis method to obtain particle analysis test results; fitting and establishing a functional relationship between the sinking depth and sinking time of soil particles in the suspension based on the particle analysis test results; calculating the sinking time required for clay particles to sink to a preset depth according to the functional relationship and based on Stokes' law; determining the corresponding soil particle mass according to the sinking time required for clay particles to sink to the preset depth and based on the particle analysis test results, and taking the determined soil particle mass as the clay particle mass in the clay sample; and calculating the clay particle content of the clay sample according to the clay particle mass. The present application improves the accuracy of clay particle content calculation and is suitable for soil analysis.

Description

Technical Field

[0001] This invention relates to the field of soil particle analysis technology, specifically to a method for calculating the clay content of soil. Background Technology

[0002] Clay particles are the smallest mineral particles in soil. As the finest active component in soil, their content is a core parameter for soil classification and plays a decisive role in the physical, chemical, and engineering properties of soil. Soils with high clay content are prone to absorbing water and swelling, and shrinking when they lose water, which may lead to foundation deformation or soil cracking. In engineering projects, it is necessary to strengthen seepage prevention treatment or improve soil quality. In agriculture, an appropriate amount of clay can enhance water and fertilizer retention capacity, but excessive content will reduce soil permeability. In the protection of soil heritage sites, clay content analysis can guide the selection of reinforcement materials and prevent collapse caused by drying shrinkage cracking.

[0003] In existing technologies, methods for determining clay content mainly include physical separation, chemical analysis, and sedimentation. Physical separation primarily involves centrifuging to separate clay particles and calculating the percentage content, or combining dispersion treatment (such as boiling or using chemical dispersants) with sieving of coarse particles, calculating the clay content based on the mass of the remaining soil particles. However, in this method, high-speed centrifugation may disrupt the bond between clay particles and organic matter or cementing agents, thus underestimating the actual clay content. Sieving is also ineffective in separating clay particles. Chemical analysis mainly uses colorimetry or chemical reagent treatment (such as using H₂O₂-HCl to remove organic matter and cementing agents) to assist in clay separation and determination. However, using chemical reagents to remove organic matter may partially dissolve clay minerals (such as vermiculite), leading to distortion of the measured clay content. The sedimentation method mainly includes the hydrometer method and the pipette method. The hydrometer method calculates the clay content by correcting the hydrometer reading, while the pipette method separates clay particles by utilizing the difference in the settling rate of soil particles. The hydrometer method is easily affected by temperature, dispersant concentration and subjective reading, and is prone to errors, especially when the clay content is low (<10%). The pipette method has higher accuracy.

[0004] Application publication number CN117491210A discloses a method for soil particle analysis, which discloses a method for determining the percentage of soil particles of different sizes in soil based on the pipette method. The main technical solution is as follows: the settling time required for soil particles of different sizes to settle freely to a preset depth is calculated by Stokes' law; a certain amount of soil suspension is taken at the preset depth according to the calculated settling time and weighed; the content of soil particles smaller than a certain size in the taken suspension is calculated; and then the percentage of soil particles of different sizes in the soil sample is calculated. This scheme assumes that the soil particles in the suspension settle at a uniform speed when calculating the settling time required for soil particles of different sizes to freely settle to a preset depth. That is, the settling depth and settling time of the soil particles in the suspension have an ideal linear relationship. However, the inventors found through research that the soil particles in the suspension do not settle at a uniform speed. That is, the settling speed of the soil particles in the suspension is not an ideal linear relationship with time, but a non-linear relationship. The settling time of the soil particles calculated based on the uniform settling speed is not accurate, which in turn leads to the problem of poor accuracy in calculating the proportion of soil particles based on the settling time. Summary of the Invention

[0005] This invention aims to address the problem of poor accuracy in existing methods for determining the clay content of soil, and proposes a method for calculating the clay content of soil.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] A method for calculating the clay content of soil, the method comprising:

[0008] After the clay sample was filtered through a sieve, a dispersant was added and the sample was shaken to disperse it, thus preparing a suspension.

[0009] The suspension was subjected to particle analysis using sedimentation analysis to obtain particle analysis results, which included the sedimentation depth of soil particles corresponding to different sedimentation times and the mass of soil particles after drying of the suspension drawn by the pipette at a preset depth.

[0010] Based on the particle analysis test results, a functional relationship between the sinking depth and sinking time of soil particles in the suspension was established.

[0011] Based on the functional relationship and Stokes' law, the sinking time required for the clay particles to sink to the preset depth is calculated.

[0012] The mass of the corresponding soil particles is determined based on the settling time required for the clay particles to sink to the preset depth and the particle analysis test results, and the determined mass of the soil particles is used as the mass of the clay particles in the clay sample.

[0013] The clay content of the clay sample is calculated based on the clay mass, the total mass of the clay sample, the total volume of the suspension, and the volume of suspension drawn by the pipette.

[0014] Furthermore, the functional relationship between the settling depth of the soil particles and the settling time is as follows:

[0015]

[0016] Where L represents the settling depth of the soil particles, t represents the settling time of the soil particles, and W and K m This represents the characteristic constant.

[0017] Furthermore, Stokes' law is as follows:

[0018]

[0019] The formula for calculating the sinking time required for the clay particles to sink to the preset depth is as follows:

[0020]

[0021] Where v represents the settling velocity of the clay particles, ρ s ρ represents the density of clay particles. w Let ρ represent the density of water at 4℃, η represent the viscosity coefficient of water, g represent the acceleration due to gravity, d represent the particle size of the clay particles, and t represent the density of water at 4℃. i This indicates the settling time of the clay particles.

[0022] Furthermore, the particle size of the clay particles is less than or equal to 0.005 mm.

[0023] Furthermore, determining the corresponding soil particle mass based on the settling time required for the clay particles to sink to the preset depth and on the results of particle analysis tests specifically includes calculating the corresponding soil particle mass using a linear interpolation method, with the calculation formula as follows:

[0024]

[0025] Where, m dx The t represents the mass of soil particles corresponding to the settling time required for clay particles to sink to the preset depth. i t represents the settling time of the clay particles. i-1 and t i+1 This represents two adjacent settling times corresponding to clay particles in the particle analysis test results, in m. di-1 and m di+1 These represent two adjacent settling times t in the particle analysis test results. i-1 and t i+1 The corresponding soil particle mass.

[0026] Furthermore, the formula for calculating the clay content is as follows:

[0027]

[0028] Where X represents the clay content of the clay sample, m dx The mass of clay particles in a clay sample is represented by m. d V represents the total mass of the clay sample, and V represents the total volume of the suspension. x This indicates the volume of suspension drawn up by the pipette.

[0029] Furthermore, particle analysis of the suspension was performed using sedimentation analysis, specifically including:

[0030] At different settling times, the settling depth of soil particles in the suspension was measured using a suspension settling meter. A pipette was used to draw up the suspension at a preset depth, the drawn up suspension was dried, and the dried soil particles were weighed to obtain the corresponding soil particle mass.

[0031] Furthermore, the dispersant is sodium hexametaphosphate.

[0032] Furthermore, the preset depth is 10cm.

[0033] Furthermore, the sieve used to filter the clay sample had an aperture of 0.075 mm.

[0034] The beneficial effects of this invention are as follows: The method for calculating the clay content of soil provided by this invention uses the sedimentation method to determine the clay content, which improves the accuracy of clay content calculation compared to physical separation methods and chemical analysis methods. Furthermore, this invention fits the true functional relationship between the sinking depth and sinking time of soil particles in the suspension based on particle analysis test results, and calculates the sinking time required for clay particles to sink to a preset depth based on this functional relationship and Stokes' law, thereby improving the accuracy of sinking time calculation and thus improving the accuracy of clay content calculation. In addition, this invention calculates the clay content based on the calculated sinking time and particle analysis test results, further improving the accuracy of clay content calculation. Attached Figure Description

[0035] Figure 1 A schematic diagram illustrating the calculation process for soil clay content provided in this embodiment;

[0036] Figure 2 A schematic diagram of the particle analysis test procedure provided for the embodiments;

[0037] Figure 3 A schematic diagram of the correlation curve between the settling depth and settling time of soil particles in the suspension provided in the example;

[0038] Figure 4 This is a schematic diagram illustrating the relationship between the logarithm of the settling time of soil particles in the suspension provided in the example and the mass of soil particles after the absorbed suspension has been dried. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings.

[0040] In some of the processes described in the specification and accompanying drawings of this invention, multiple operations are included in a specific order. However, it should be clearly understood that these operations may not be executed in the order they appear herein or may be executed in parallel. The sequence number of the operation is only used to distinguish the different operations and does not represent any execution order itself. In addition, these processes may include more or fewer operations, and these operations may be executed sequentially or in parallel.

[0041] The technical solution of this invention is applicable to soil clay content analysis, such as foundation soil, agricultural soil, and soil heritage protection.

[0042] Currently, the sedimentation method is generally used to analyze the clay content of soil, which assumes that soil particles in the suspension fall at a constant speed. However, the inventors have discovered that soil particles in the suspension do not fall at a constant speed. Therefore, the method of analyzing the clay content of soil based on the constant speed of soil particle settling has poor accuracy.

[0043] Based on this, the technical solution of the present invention is proposed. In the present invention, a clay sample filtered through a sieve is added to a dispersant and dispersed by shaking to form a suspension. A sedimentation analysis method is used to perform particle analysis on the suspension to obtain particle analysis results. The particle analysis results include the settling depth of soil particles corresponding to different settling times and the mass of soil particles after drying the suspension drawn by a pipette at a preset depth. Based on the particle analysis results, a functional relationship between the settling depth and settling time of soil particles in the suspension is established. The settling time required for the clay particles to settle to the preset depth is calculated based on the functional relationship and Stokes' law. The corresponding soil particle mass is determined based on the settling time required for the clay particles to settle to the preset depth and the particle analysis results, and the determined soil particle mass is used as the clay particle mass in the clay sample. The clay content of the clay sample is calculated based on the clay particle mass, the total mass of the clay sample, the total volume of the suspension, and the volume of suspension drawn by the pipette.

[0044] Specifically, this invention first prepares a clay sample into a suspension and conducts particle analysis on the suspension, recording the sinking depth of soil particles corresponding to different sinking times, and recording the mass of soil particles after drying, obtained by pipetting at a preset depth at different sinking times. Then, based on the sinking depth of soil particles corresponding to different sinking times in the particle analysis test results, a true functional relationship between the sinking depth and sinking time of soil particles in the suspension is fitted, and then the sinking time required for clay particles to sink to the preset depth is calculated based on the functional relationship and Stokes' law. Next, based on the calculated sinking time and the mass of soil particles corresponding to different sinking times in the particle analysis test results, the corresponding clay mass is calculated. Finally, the percentage of clay content in the clay sample is calculated based on the clay mass. Compared with existing physical separation and chemical analysis methods, this invention improves the accuracy of clay content calculation. Furthermore, by calculating the settling time required for clay particles to sink to a preset depth using a fitted functional relationship, this invention improves the accuracy of settling time calculation, thereby improving the accuracy of clay content calculation. In addition, this invention calculates clay content based on particle analysis test results, further improving the accuracy of clay content calculation.

[0045] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0046] Figure 1 A flowchart illustrating a method for calculating the clay content of soil is shown below. Please refer to [link / reference]. Figure 1 The method includes the following steps:

[0047] Step 1: After filtering the clay sample through a sieve, add a dispersant and shake to disperse it, thus preparing a suspension.

[0048] In practical applications, clay samples can be filtered through a sieve with a pore size of 0.075 mm, and then a dispersant can be added to make a suspension. The dispersant can be sodium hexametaphosphate.

[0049] Step 2: Perform particle analysis on the suspension using sedimentation analysis to obtain particle analysis results. The particle analysis results include the sedimentation depth of soil particles corresponding to different sedimentation times and the mass of soil particles after drying of the suspension drawn by the pipette at a preset depth.

[0050] Please see Figure 2 In practical applications, the sinking depth of soil particles in a suspension can be measured using a suspension sinking meter at different sinking times. A pipette is used to draw up a suspension at a preset depth, the drawn suspension is dried, and the dried soil particles are weighed to obtain the sinking depth and soil particle mass corresponding to different sinking times.

[0051] In this embodiment, a 30g clay sample was filtered through a sieve with a pore size of 0.075mm, and then a dispersant was added and the sample was shaken to disperse it, resulting in a suspension with a total volume of V = 1000mL. The settling depth of the soil particles in the suspension was measured at different settling times (0, t1, t2, t3, ...), and the mass of the soil particles after drying the suspension at a depth of 10cm was recorded. The particle analysis test results are shown in Table 1.

[0052] Table 1 - Results of particle analysis tests

[0053]

[0054] Step 3: Based on the particle analysis test results, establish a functional relationship between the sinking depth and sinking time of soil particles in the suspension.

[0055] Based on particle analysis test results, it can be found that the settling behavior of soil particles in the suspension conforms to the soil mechanics theory of suspension settling; however, the settling velocity of soil particles in the suspension is not uniform. Please refer to [link / reference]. Figure 3 Based on the particle analysis test results, a correlation curve between the settling time and the settling depth of soil particles in the suspension can be obtained by fitting. By analyzing the correlation curve between the settling time and the settling depth, it can be found that the curve basically conforms to the curve law of the Michaelis-Menten equation, which represents a hyperbola.

[0056] Based on this, this embodiment establishes a functional relationship between the settling time and settling depth of soil particles (including clay particles) in suspension by fitting the particle analysis test results, as follows:

[0057]

[0058] Where L represents the settling depth of the soil particles (cm), t represents the settling time of the soil particles (min), and W and K m The characteristic constant is represented by the constant, which is obtained by regression calculation following the Michaelis-Menten equation.

[0059] In this embodiment, the functional relationship obtained by fitting the particle analysis test results in Table 1 is as follows:

[0060]

[0061] Step 4: Calculate the sinking time required for the clay particles to sink to the preset depth based on the functional relationship and Stokes' law.

[0062] It is understandable that Stokes' law can be used to calculate the settling velocity of soil particles in fluids. The expression for calculating the settling velocity of clay particles in a suspension using Stokes' law can be:

[0063]

[0064] Where v represents the settling velocity of the clay particles, ρ s Density of clay particles (g / cm³) 3 ), ρ w This indicates the density of water at 4℃ (g / cm³). 3 ), where η represents the viscosity coefficient of water (1×10⁻⁶). -6 kPa·s), where g represents the acceleration due to gravity (981 cm / s²). 2 ), where d represents the particle size (mm) of the clay particles.

[0065] By establishing an integral equation, a formula for calculating the settling time required for clay particles to sink to the preset depth can be derived, namely:

[0066]

[0067] Among them, t i This indicates the sinking time (in minutes) required to sink to the preset depth.

[0068] In practical applications, by substituting the density and particle size of the clay particles into the above formula, the settling time required for the clay particles to sink to the preset depth can be calculated. In this embodiment, soil particles with a particle size less than or equal to 0.005 mm are used as clay particles, i.e., d = 0.005 mm. Substituting these values ​​into the above formula yields the settling time t required for the clay particles to sink to a depth of 10 cm. i = 64.43 min.

[0069] Step 5: Determine the corresponding soil particle mass based on the settling time required for the clay particles to sink to the preset depth and the particle analysis test results, and use the determined soil particle mass as the clay particle mass in the clay sample.

[0070] Based on the particle analysis test results, a table showing the correspondence between the logarithm of the settling time of soil particles in the suspension and the mass of soil particles after drying the suspension can be obtained. Please refer to Table 2.

[0071] Table 2 - Correspondence between the logarithm of settling time and the mass of soil particles after drying the extracted suspension

[0072]

[0073]

[0074] Please see Figure 4Based on the correspondence table shown in Table 2, a graph showing the relationship between the logarithm of the settling time of soil particles in the suspension and the mass of soil particles after the suspension has been dried can be obtained. Constructing this correspondence by taking the logarithm of the settling time reduces computational complexity, avoids numerical overflow or underflow problems, thereby simplifying the calculation and improving computational efficiency.

[0075] Based on the correlation between the logarithm of the settling time of soil particles in the suspension and the mass of soil particles after drying the suspension, an interpolation method can be used to calculate the mass of soil particles after drying the suspension corresponding to the settling time required for clay particles to sink to the preset depth, and this mass can be taken as the clay particle mass. The calculation formula is as follows:

[0076]

[0077] Where, m dx The t represents the mass of soil particles corresponding to the settling time required for clay particles to sink to the preset depth. i t represents the settling time of the clay particles. i-1 and t i+1 This represents two adjacent settling times corresponding to clay particles in the particle analysis test results, in m. di-1 and m di+1 These represent two adjacent settling times t in the particle analysis test results. i-1 and t i+1 The corresponding soil particle mass.

[0078] Based on the particle analysis results shown in Table 1, it is assumed that the settling time t required for clay particles to settle to a depth of 10 cm has been calculated. i =64.43min, then in the particle analysis test results, the two adjacent settling times are 50min and 120min, respectively, i.e. t i-1 =50min,t i+1 =120min, the corresponding soil particle masses after drying the suspension were 7.5mg and 5.5mg, respectively, i.e. m di-1 =7.5mg, m di+1 =5.5mg. Substitute the above data into the formula to calculate the mass of soil particles corresponding to the clay settling to a depth of 10cm:

[0079]

[0080] Step 6: Calculate the clay content of the clay sample based on the clay mass, the total mass of the clay sample, the total volume of the suspension, and the volume of suspension drawn by the pipette.

[0081] In this embodiment, the formula for calculating the clay content is as follows:

[0082]

[0083] Where X represents the clay content (%) of the clay sample, m dx m represents the mass (mg) of clay particles in a clay sample. d V represents the total mass of the clay sample (mg), and V represents the total volume of the suspension (mL). x This indicates the volume (mL) of suspension drawn up by the pipette.

[0084] Assume that the mass m of clay particles in the clay sample obtained in step 5 is calculated. dx =6.08mg, total mass m of clay sample d =30g, total suspension volume V = 1000mL, suspension volume V drawn by pipette x =25mL, substitute the above data into the formula to calculate the clay content of the clay sample:

[0085]

[0086] In summary, this embodiment uses the sedimentation method to determine the clay content, which improves the accuracy of clay content calculation compared to physical separation and chemical analysis methods. Furthermore, this embodiment fits the true functional relationship between the sinking depth and sinking time of soil particles in the suspension based on particle analysis test results. Based on this functional relationship and Stokes' law, it calculates the sinking time required for clay particles to sink to a preset depth, improving the accuracy of sinking time calculation and thus improving the accuracy of clay content calculation. Additionally, this embodiment calculates the clay content based on the calculated sinking time and particle analysis test results, further improving the accuracy of clay content calculation.

Claims

1. A method for calculating the clay content of soil, characterized in that, The method includes: After the clay sample was filtered through a sieve, a dispersant was added and the sample was shaken to disperse it, thus preparing a suspension. The suspension was subjected to particle analysis using sedimentation analysis to obtain particle analysis results, which included the sedimentation depth of soil particles corresponding to different sedimentation times and the mass of soil particles after drying of the suspension drawn by the pipette at a preset depth. Based on the particle analysis test results, a functional relationship between the sinking depth and sinking time of soil particles in the suspension was fitted. Based on the functional relationship and Stokes' law, the sinking time required for the clay particles to sink to the preset depth is calculated. The mass of the corresponding soil particles is determined based on the settling time required for the clay particles to sink to the preset depth and the particle analysis test results, and the determined mass of the soil particles is used as the mass of the clay particles in the clay sample. The clay content of the clay sample is calculated based on the clay mass, the total mass of the clay sample, the total volume of the suspension, and the volume of suspension drawn by the pipette. The functional relationship between the settling depth of the soil particles and the settling time is as follows: ； in, Indicates the depth of soil particles settling. Indicates the settling time of soil particles. and Represents the characteristic constant; The step of determining the corresponding soil particle mass based on the settling time required for the clay particles to sink to the preset depth and on the results of particle analysis tests specifically includes calculating the corresponding soil particle mass using a linear interpolation method, with the calculation formula as follows: ； in, This represents the mass of soil particles corresponding to the settling time required for clay particles to sink to the preset depth. This indicates the settling time of the clay particles. and This represents two adjacent settling times corresponding to clay particles in the particle analysis test results. and These represent two adjacent settling times in the particle analysis test results. and The corresponding soil particle mass.

2. The method for calculating the clay content of soil according to claim 1, characterized in that, Stokes' law is as follows: ； The formula for calculating the sinking time required for the clay particles to sink to the preset depth is as follows: ； in, This indicates the settling velocity of the clay particles. This represents the density of clay particles. This indicates the density of water at 4℃. Indicates the viscosity coefficient of water. Represents gravitational acceleration. Indicates the particle size of the clay particles. This indicates the settling time of the clay particles.

3. The method for calculating the clay content of soil according to claim 2, characterized in that, The particle size of the clay particles is less than or equal to 0.005 mm.

4. The method for calculating the clay content of soil according to claim 1, characterized in that, The formula for calculating the clay content is as follows: ； in, This indicates the clay content of the clay sample. This indicates the mass of clay particles in the clay sample. This represents the total mass of the clay sample. Indicates the total volume of the suspension. This indicates the volume of suspension drawn up by the pipette.

5. The method for calculating the clay content of soil according to claim 1, characterized in that, Particle analysis of the suspension was performed using sedimentation analysis, specifically including: At different settling times, the settling depth of soil particles in the suspension was measured using a suspension settling meter. A pipette was used to draw up the suspension at a preset depth, the drawn up suspension was dried, and the dried soil particles were weighed to obtain the corresponding soil particle mass.

6. The method for calculating the clay content of soil according to claim 1, characterized in that, The dispersant is sodium hexametaphosphate.

7. The method for calculating the clay content of soil according to claim 1, characterized in that, The preset depth is 10cm.

8. The method for calculating the clay content of soil according to claim 1, characterized in that, The sieve used to filter the clay sample has an aperture of 0.075 mm.

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