A method for determining moisture content in soil tests

Abstract

The present application belongs to the field of mine solid material property measurement, and particularly relates to a geotechnical test moisture content determination method. The method comprises the following steps: calculating the mass of a container filled with water; sampling and drying the sample to calculate the moisture content; calculating the dry mass of another sample and the mass of the wet sample weight gain; calculating the K value; and using the K value to calculate the moisture content of other samples. The present application does not need to repeatedly dry the original sample, does not need to use alcohol burning, and can realize rapid determination of the moisture content.

Description

Technical Field

[0001] This invention relates to the field of determining the properties of solid materials in mining, specifically to a method for determining moisture content in geotechnical tests. Background Technology

[0002] In geotechnical testing, moisture content tests are mainly conducted on samples such as coarse-grained soil, fine-grained soil, organic soil, and frozen soil. Methods for determining the moisture content of samples include the drying method, the alcohol burning method, and the gravity method. The drying method is time-consuming and requires specialized drying oven equipment.

[0003] The alcohol burning method has poor safety, is prone to causing fires, and is greatly affected by the sample, the amount of alcohol used, and the degree of combustion. Moreover, the alcohol burning method is only suitable for samples with stable properties, and is not suitable for samples with high organic content or samples that are easily denatured at high temperatures.

[0004] The specific gravity method, along with the drying method and the alcohol burning method, belongs to offline detection methods. However, the specific gravity method has problems such as large detection error and high formula sensitivity, making it difficult to apply in practical engineering. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the moisture content of geotechnical tests. This method does not require drying the sample each time, nor does it require burning the sample with alcohol. It not only provides accurate results, but also enables rapid determination of the moisture content of the sample.

[0006] The specific technical solution of the present invention is as follows: A method for determining the moisture content of a geotechnical test includes the following steps: Step 1: Calculate the mass of the container filled with water. Fill an empty container with water, remove the lid, and make sure the lid completely covers the entire opening of the container to obtain the mass of the container filled with water; Step 2: Take samples and dry them, then calculate the moisture content. Take a representative sample, mix it evenly, and record the mass of the sample before drying and the dry mass of the sample after drying. Calculate the constant moisture content of the sample based on the above mass and dry mass. Step 3: Calculate the dry mass of the other sample and the weight gain of the wet sample. Take another sample of a certain mass from the representative sample in step 2, record the mass of the wet sample, and calculate the dry mass of the other sample based on the fixed moisture content in step (2); Add a small amount of water to the wet sample to obtain a slurry, transfer it to another identical container, fill it with water, add a cover, and obtain the mass of the container, the wet sample and the water. Subtract the mass of the container filled with water in step 1 to obtain the mass of the wet sample gain. Step 4: Calculate the K value The K value is obtained based on the dry mass and the weight gain of the wet sample in step 3; Step 5: Calculate the moisture content of other samples using the K value. In step 2, a certain mass of wet sample is weighed from the representative sample. The mass of the wet sample is obtained by weighing. Following the operation method in step 3, the mass of the container, wet sample, and water, as well as the mass of the wet sample weight gain, are obtained. Based on the mass of the wet sample weight gain and the K value, the mass of the dry sample is calculated. Then, the moisture content is calculated based on the dry sample mass and the wet sample mass.

[0007] As a preferred option, in step 2, for samples with an organic matter content exceeding 5% and those prone to denaturation above 100°C, the samples are dried to constant weight at a constant temperature of 65-70°C.

[0008] As a preferred method, in step 2, take 1-2 kg of representative sample, mix it evenly, place 15-30 g of sample in a drying device, record the mass of the sample before drying, dry it at a constant temperature of 105-110°C for 6-8 hours until constant weight, and record the dry mass of the sample after drying.

[0009] As a preferred option, in step S3, the wet sample is placed in a beaker, a small amount of water is added, the large particles of the wet sample are broken up, air bubbles are initially removed to obtain a slurry, and then all the slurry is poured into a container and the container is filled with water.

[0010] As a preferred option, in step S3, after the transfer, the mixture is stirred thoroughly to remove air bubbles, and if necessary, allowed to stand for a period of time.

[0011] As a preferred option, samples with an organic matter content exceeding 5% include peat soil, humus soil, and organic clay. Samples that are prone to change at temperatures above 100°C include saline soil and frozen soil. Saline soil and frozen soil contain easily soluble salts, including gypsum and mirabilite. Attached Figure Description

[0012] Figure 1 This is a flowchart of a geotechnical test method for determining moisture content according to one embodiment of the present invention. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased.

[0014] Unless otherwise stated, all percentages in this invention represent mass fractions. Ratios are mass percentages, and concentrations are mass concentrations.

[0015] Unless otherwise specified, all materials, instruments, and equipment used below are conventional materials, instruments, and equipment or obtained through commercial channels; all testing methods used are existing methods unless otherwise specified.

[0016] Currently, the main methods for determining the moisture content of samples in geotechnical testing include the drying method, the alcohol burning method, and the specific gravity method. The drying method involves placing the sample in a constant-temperature oven at 105-110℃ until it reaches a constant weight. During the operation, 15-30g of sample is weighed and placed in a weighing box of known mass. After accurate weighing, the sample is placed in the oven and dried for 6-8 hours. After cooling, the sample is weighed again, and the moisture content is calculated based on the difference in mass before and after drying. Its advantages are high accuracy and reliable results, and it is suitable for various types of samples; its disadvantages are that it is time-consuming and requires specialized drying equipment.

[0017] The principle of the alcohol burning method is to use the heat generated by the combustion of alcohol to evaporate the moisture in the sample. After repeated burning until constant weight, the moisture content is calculated by the difference in mass. During operation, 10-15g of sample is weighed into an aluminum box, alcohol is sprayed until the sample is submerged, and the sample is allowed to burn. After the flame extinguishes, the spraying and burning are repeated 2-3 times until constant weight is achieved. After cooling, the sample is weighed and the weight is calculated. Its advantages are simple operation, speed, no need for complex equipment, and suitability for rapid on-site determination. Its disadvantages are poor safety, a high risk of fire, and significant influence from the sample, the amount of alcohol used, and the degree of combustion. The alcohol burning method is only suitable for samples with stable properties and is not suitable for samples with high organic content or those prone to denaturation at high temperatures.

[0018] The specific gravity method is based on the three-phase composition of the sample. By weighing the wet sample and the different masses of the specific gravity bottle filled with water and then filled with water, combined with the known specific gravity of the sample particles, the ratio of the mass of water to the mass of the sample particles is indirectly derived by utilizing the relationship between the volume of water displaced by the wet sample and the volume of the sample particles and water. This allows for the calculation of the sample's moisture content. The specific gravity method, along with the drying method and the alcohol burning method, belongs to offline detection methods. However, the specific gravity method suffers from large detection errors and high formula sensitivity, making it difficult to apply in practical engineering. Therefore, this invention provides a method for determining the moisture content of a geotechnical test, including the following steps: Step 1: Calculate the mass of the container filled with water. Fill an empty container with water, remove the lid, and make sure the lid completely covers the entire opening of the container to obtain the mass of the container filled with water.

[0019] Step 2: Take samples and dry them, then calculate the moisture content. Take a representative sample, mix it evenly, and record the mass of the sample before drying and the dry mass of the sample after drying. Calculate the constant moisture content of the sample based on the above mass and dry mass.

[0020] Step 3: Calculate the dry mass of the other sample and the weight gain of the wet sample. Take another sample of a certain mass from the representative sample in step 2, record the mass of the wet sample, and calculate the dry mass of the other sample based on the fixed moisture content in step (2).

[0021] Add a small amount of water to the wet sample to obtain a slurry, transfer it to another identical container, fill it with water, add a cover, and obtain the mass of the container, the wet sample, and the water. Subtract the mass of the container filled with water in step 1 to obtain the mass increase of the wet sample.

[0022] Step 4: Calculate the K value The K value is obtained based on the dry mass and the weight gain of the wet sample in step 3; Step 5: Calculate the moisture content of other samples using the K value. In step 2, a certain mass of wet sample is weighed from the representative sample. The mass of the wet sample is obtained by weighing. Following the operation method in step 3, the mass of the container, wet sample, and water, as well as the mass of the wet sample weight gain, are obtained. Based on the mass of the wet sample weight gain and the K value, the mass of the dry sample is calculated. Then, the moisture content is calculated based on the dry sample mass and the wet sample mass.

[0023] The container can be a conical flask, etc. When venting, the glass plate completely covers the entire mouth of the flask. During the process, the residual air is squeezed out by the contact between the glass plate and the water surface to ensure that no bubbles are generated.

[0024] This invention involves placing the original sample into a conical flask and filling it with water. The total mass of the sample and water is weighed, and the mass of the water when the conical flask is full is subtracted to obtain the mass difference of the sample. The moisture content of the wet sample is determined according to the national standard GB / T 50123-2019 "Standard for Geotechnical Testing Methods," and the mass of the dry sample is calculated. A constant is obtained by dividing the mass of the dry sample by the mass difference of the samples. This constant can be used to determine different moisture contents of the same sample in subsequent tests. This method eliminates the need for repeated drying of the original sample or alcohol burning, and enables rapid determination of moisture content.

[0025] This invention utilizes the property that a certain constant remains constant within the sample. First, this constant is determined. Then, a certain mass of wet sample is weighed, and the mass difference is calculated. The dry mass of the sample is then calculated using the constant, thus yielding the sample's moisture content. This method eliminates the need for drying or alcohol ignition of samples with fluctuating moisture content during each measurement. The method is convenient, rapid, provides accurate and reliable data, and is simple to understand. It is applicable to various samples, enables rapid moisture content determination, aligns with current green and environmentally friendly principles, and has broad applicability.

[0026] For samples with known fixed constants, the moisture content can be obtained by measuring the mass of the sample and the mass gain of the sample.

[0027] As one implementation method, for samples with an organic matter content exceeding 5% and that are prone to denaturation at temperatures above 100°C, they are dried to constant weight at a constant temperature of 65-70°C.

[0028] For soil samples with an organic matter content exceeding 5% and samples prone to physical and chemical changes at temperatures above 100°C, the conventional drying method of 105°C ± 2°C should not be used. This is because in such soil samples, at high temperatures of 100°C and above, organic matter is easily oxidized, decomposed, and carbonized, and easily soluble minerals such as salts will lose their water of crystallization or decompose and volatilize, resulting in additional weight loss due to non-water evaporation. This leads to an overestimation and distortion of the moisture content measurement results. On the other hand, 65~70°C can slowly and thoroughly evaporate the free water and weakly bound water in the soil without damaging the soil sample's own composition, ensuring the accuracy of the moisture content measurement results.

[0029] In one implementation method, in step 2, take 1-2 kg of representative sample, mix it evenly, place 15-30 g of sample in a drying device, record the mass of the sample before drying, dry it at a constant temperature of 105-110°C for 6-8 hours until constant weight, and record the dry mass of the sample after drying to ensure accurate results.

[0030] In one implementation method, in step S3, the wet sample is placed in a beaker, a small amount of water is added to break up the large particles of the wet sample, and air bubbles are initially removed to obtain a slurry. Then, all the slurry is poured into a container and the container is filled with water to make the sample evenly dispersed.

[0031] In one implementation method, in step S3, after the transfer, the mixture is stirred thoroughly to remove air bubbles, and if necessary, it is left to stand for a period of time to ensure that the air is completely expelled.

[0032] As one implementation method, samples with an organic matter content of more than 5% include peat soil, humus soil, and organic clay. Samples that are easily deformed above 100°C are samples that are prone to physical and chemical changes above 100°C, including saline soil and frozen soil. Saline soil and frozen soil contain easily soluble salts, including gypsum and mirabilite.

[0033] This invention targets soil samples with an organic matter content exceeding 5% (such as peat soil, humus soil, organic clay, etc.) and samples that are prone to physical and chemical changes at temperatures above 100°C (such as saline soil containing easily soluble salts such as gypsum and mirabilite, frozen soil, etc.). By drying them to constant weight at a constant temperature of 65~70°C, the moisture content measurement results are guaranteed to be true and accurate.

[0034] To further illustrate the present invention, the following describes in detail a method for determining the moisture content of a geotechnical test provided by the present invention, in conjunction with embodiments. Example 1

[0035] The method for determining the moisture content of the geotechnical test in this embodiment is as follows: Step 1: Calculate the mass of the container filled with water. Take a 300ml or 500ml conical flask, ensuring it is dry inside and out. Fill the empty flask with water. Take a glass plate with an area at least twice the size of the flask's opening and press its edge against one side of the opening. Then, smoothly and horizontally push the glass plate from the pressed side to the other side, completely covering the opening. During this process, use the pressure between the glass plate and the water surface to expel any remaining air, ensuring no air bubbles are generated. Determine the mass of the water when the flask is full, denoted as M, where M = 647.94g. Divide the mass of the water in the flask by the density of water to obtain the volume of the flask when it is full. The required electronic balance for this experiment has an accuracy of 0.01g.

[0036] Step 2: Take samples and dry them, then calculate the moisture content. Take a representative sample of 2 kg, which is tailings from a beneficiation plant with an organic carbon content of 5.49%, and mix it thoroughly. Place 30 g of the sample in an oven and record the mass m of the sample before drying. 湿 .

[0037] The sample was dried at a constant temperature of 105°C for 8 hours until constant weight was achieved, and the dry weight m of the dried sample was recorded. 干 Bake at a constant temperature of 65°C until constant weight.

[0038] The constant moisture content ω of the sample is calculated using equation (1): =30.12%. (1) In the above formula, ω represents the moisture content of the sample, %; m 湿 - Mass of the sample before drying, g, m 干 - The dry mass of the sample after drying, in g.

[0039] Step 3: Calculate Δm and m 干 Take another 30g sample from the representative sample in step 2 and record the mass m of the wet sample. 湿 The dry mass m of the additional sample is calculated using equation (1). 干 ,Right now =23.06g.

[0040] Next, place the wet sample into a beaker, add a small amount of water, and use a spatula to break up the large particles of the wet sample to initially remove air bubbles and obtain a slurry.

[0041] Then use a dropper to pour all the slurry into the conical flask and fill the flask with water. During this process, use a glass rod to stir thoroughly to remove air bubbles, and let it stand for a period of time if necessary.

[0042] Finally, use a glass plate twice the size of the conical flask opening to horizontally push along the flask opening to cover it, ensuring no air bubbles are generated, and obtain the mass m of the wet sample and water.

[0043] Calculate Δm using equation (2): =13.81g(2) In the above formula, Δm is the mass of the wet sample gain, g; m is the mass of water added to the wet sample, g; and M is the mass of water when the conical flask is filled with water, g.

[0044] Step 4: Calculate the K value Calculate the K value using equation (3): =1.67(3) In the above formula, K is a constant, and m 干 - The dry mass of the sample in step 3, g; Δm - the mass of the wet sample gain, g.

[0045] Step 5: Calculate moisture content using the K value In step 2, 50g of wet sample m1 is weighed from the representative sample. Following the operation method in step 4, the mass m0 of the wet sample and water is obtained. Δm1 is calculated using equation (2), i.e. The mass m2 of the dry sample is calculated using equation (3), i.e. .

[0046] The moisture content ω1 is calculated using equation (1), i.e. K=1.67, which is the K value of the representative sample in step 2. Example 2

[0047] The method for determining the moisture content of the geotechnical test in this embodiment is as follows: Step 1: Calculate the mass of the container filled with water. This step is the same as in Example 1.

[0048] Step 2: Take samples and dry them, then calculate the moisture content. Take a representative sample of 2 kg, which is phosphogypsum produced by the wet-process phosphoric acid production method, and mix it thoroughly. Place 30 g of the sample in an oven and record the mass m of the sample before drying. 湿 .

[0049] The sample was dried at a constant temperature of 105°C for 8 hours until constant weight was achieved, and the dry weight m of the dried sample was recorded. 干 Bake at a constant temperature of 65°C until constant weight.

[0050] The constant moisture content ω of the sample is calculated using equation (1): =15.85%(1) In the above formula, ω represents the moisture content of the sample, %; m 湿 - Mass of the sample before drying, g, m 干 - The dry mass of the sample after drying, in g.

[0051] Step 3: Calculate Δm and m 干 Take another 30g sample from the representative sample in step 2 and record the mass m of the wet sample. 湿 The dry mass m of the additional sample is calculated using equation (1). 干 ,Right now =25.9g.

[0052] Next, place the wet sample into a beaker, add a small amount of water, and use a spatula to break up the large particles of the wet sample to initially remove air bubbles and obtain a slurry.

[0053] Then use a dropper to pour all the slurry into the conical flask and fill the flask with water. During this process, use a glass rod to stir thoroughly to remove air bubbles, and let it stand for a period of time if necessary.

[0054] Finally, use a glass plate twice the size of the conical flask opening to horizontally push along the flask opening to cover it, ensuring no air bubbles are generated, and obtain the mass m of the wet sample and water.

[0055] Calculate Δm using equation (2): =17.04g(2) In the above formula, Δm is the mass of the wet sample gain, g; m is the mass of water added to the wet sample, g; and M is the mass of water when the conical flask is filled with water, g.

[0056] Step 4: Calculate the K value Calculate the K value using equation (3): =1.52(3) In the above formula, K is a constant, and m 干 - The dry mass of the sample in step 3, g; Δm - the mass of the wet sample gain, g.

[0057] Step 5: Calculate moisture content using the K value In step 2, 50g of wet sample m1 is weighed from the representative sample. Following the operation method in step 4, the mass m0 of the wet sample and water is obtained. Δm1 is calculated using equation (2), i.e. The mass m2 of the dry sample is calculated using equation (3), i.e. .

[0058] The moisture content ω1 is calculated using equation (1), i.e. K=1.52, which is the K value of the representative sample in step 2.

[0059] The moisture content of different batches of samples from Examples 1 and 2 was determined using the drying method, the K-value method of the examples, and the specific gravity method. The moisture contents determined by the three methods were ω, ω1, and ω2, respectively. The principles and operations of the drying method and the specific gravity method for determining the moisture content were referred to the "Geotechnical Testing Procedures" (SL237-1999).

[0060] Where |ω1-ω| is the absolute error between the K-value method and the drying method, and |ω2-ω| is the absolute error between the specific gravity method and the drying method. The results of |ω1-ω2| are shown in Table 1.

[0061] Table 1 For the three batches of Sample 1 and Sample 2, the moisture content ω1 of the same batch of samples was measured in parallel using the K-value method of the embodiment. The results showed that the parallel difference of the moisture content of the three batches did not exceed 1%, indicating that the parallel difference of the moisture content determination by the K-value method complies with the "Standard for Geotechnical Testing Methods" (GBT50123-2019). Furthermore, the absolute error of the moisture content calculated by the K-value method of the embodiment compared with the drying method is smaller than the absolute error of the moisture content calculated by the specific gravity method compared with the drying method. The absolute error of the moisture content determined by the K-value method of the embodiment is below 1%, indicating that the data is accurate and reliable, and the K-value method of the embodiment can be used to replace the drying method to calculate the moisture content.

[0062] After calculating the K-value of the sample, the method of this invention can complete the moisture content detection of the sample in only 15 minutes. Compared with the traditional drying method, which takes at least 6 hours, the detection cycle is significantly shortened, and it has the advantages of fast detection speed and high accuracy, and can basically realize real-time moisture content detection. For special samples with organic matter content greater than 5% and those that are easily denatured at high temperatures, the traditional drying method requires strict temperature control at 65~70℃, which further prolongs the detection time; however, the method of this invention can still achieve rapid and accurate detection for such samples, demonstrating good applicability and promotional value in the moisture content detection of such special samples.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for determining the moisture content of a geotechnical test, characterized in that, Includes the following steps: Step 1: Calculate the mass of the container filled with water. Fill an empty container with water, remove the lid, and make sure the lid completely covers the entire opening of the container to obtain the mass of the container filled with water; Step 2: Take samples and dry them, then calculate the moisture content. Take a representative sample, mix it evenly, and record the mass of the sample before drying and the dry mass of the sample after drying. Calculate the constant moisture content of the sample based on the above mass and dry mass. Step 3: Calculate the dry mass of the other sample and the weight gain of the wet sample. Take another sample of a certain mass from the representative sample in step 2, record the mass of the wet sample, and calculate the dry mass of the other sample based on the fixed moisture content in step (2); Add a small amount of water to the wet sample to obtain a slurry, transfer it to another identical container, fill it with water, add a cover, and obtain the mass of the container, the wet sample and the water. Subtract the mass of the container filled with water in step 1 to obtain the mass of the wet sample gain. Step 4: Calculate the K value The K value is obtained based on the dry mass and the weight gain of the wet sample in step 3; Step 5: Calculate the moisture content of other samples using the K value. In step 2, a certain mass of wet sample is weighed from the representative sample. The mass of the wet sample is obtained by weighing. Following the operation method in step 3, the mass of the container, wet sample, and water, as well as the mass of the wet sample weight gain, are obtained. Based on the mass of the wet sample weight gain and the K value, the mass of the dry sample is calculated. Then, the moisture content is calculated based on the dry sample mass and the wet sample mass.

2. The method for determining the moisture content of geotechnical tests according to claim 1, characterized in that, In step 2, for samples with an organic matter content exceeding 5% and those prone to denaturation above 100°C, they are dried to constant weight at a constant temperature of 65-70°C.

3. The method for determining the moisture content of geotechnical tests according to claim 1, characterized in that, In step 2, take 1-2 kg of representative sample, mix it evenly, place 15-30 g of sample in a drying device, record the mass of the sample before drying, dry it at a constant temperature of 105-110°C for 6-8 hours until constant weight, and record the dry mass of the sample after drying.

4. The method for determining the moisture content of geotechnical tests according to claim 1, characterized in that, In step S3, the wet sample is placed in a beaker, a small amount of water is added, and the large particles of the wet sample are broken up to initially remove air bubbles and obtain a slurry. Then, all the slurry is poured into a container and the container is filled with water.

5. The method for determining the moisture content of geotechnical tests according to claim 1, characterized in that, In step S3, after the transfer, stir thoroughly to remove air bubbles, and let it stand for a period of time if necessary.

6. The method for determining the moisture content of geotechnical tests according to claim 2, characterized in that, Samples with an organic matter content exceeding 5% include peat soil, humus soil, and organic clay. Samples that are prone to change at temperatures above 100°C include saline soil and frozen soil. Saline soil and frozen soil contain soluble salts, including gypsum and mirabilite.

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