A method for determining the porosity of coarse-grained soil

Abstract

This invention relates to the field of engineering surveying technology and provides a method for determining the porosity of coarse-grained soil. The method includes: excavating a first trench in the field and removing all the coarse-grained soil from the first trench; determining the total mass m1 of the coarse-grained soil in the first trench; measuring the volume of the first trench in the field as the total pore-containing volume V1 of the coarse-grained soil in the first trench; measuring the total mass m2 of all the coarse-grained soil drained from the first trench in the field using the drainage method; excavating a second trench at a location adjacent to the first trench and taking a sample from the second trench for laboratory measurement to determine the moisture content w of the coarse-grained soil; determining the particle volume V2 of the coarse-grained soil in the first trench based on m1, m2, and w; and determining the porosity of the coarse-grained soil based on V1 and V2. This method solves the problem of particle density representativeness error caused by partial sampling in traditional porosity measurement methods.

Description

Technical Field

[0001] This invention relates to the field of engineering surveying technology, and in particular to a method for determining the porosity of coarse-grained soil. Background Technology

[0002] In geotechnical engineering investigation, soil porosity is a crucial design parameter for grouting reinforcement projects. For shallow coarse-grained soils (such as gravel and pebble layers), accurately obtaining their porosity is a direct basis for assessing soil permeability and groutability, as well as calculating the grouting volume, and is of decisive significance for ensuring project safety and controlling construction costs.

[0003] Currently, the mainstream method for obtaining the porosity of coarse-grained soil in engineering practice is an indirect determination method. Its standard steps are typically as follows: First, a sufficiently large trench is excavated on-site. Then, a portion of the coarse-grained soil samples from the trench are selected and brought back to the laboratory. In the laboratory, the dry density and particle density of these samples are measured respectively. Finally, the dry density and particle density are substituted into the formula n=1-(ρ d / ρ s In the calculation, the porosity n is obtained, where ρ is the porosity. d Dry density, ρ s This refers to particle density. However, this method has the following drawbacks:

[0004] 1. Coarse-grained soil is usually composed of a mixture of various mineral particles such as quartz, feldspar, mica, and rock fragments. The particle density ρ of different minerals varies. s Significant differences exist. Traditional methods only select a portion of samples for indoor particle density testing and use this test value to characterize the soil, which may have uneven composition throughout the trench. When the soil particle composition is spatially uneven, the particle density of this portion of the sample cannot represent the average particle density of the entire soil mass, easily leading to a discrepancy between the calculated porosity of coarse-grained soil and the actual porosity.

[0005] 2. The entire method relies on sophisticated indoor testing equipment (such as specific gravity bottles) to determine particle density. The process is time-consuming and cannot quickly obtain key data.

[0006] Therefore, there is an urgent need for an improved method for determining the porosity of coarse-grained soil. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for determining the porosity of coarse-grained soil, which solves the problem of particle density representativeness error caused by partial sampling in traditional porosity measurement methods, as well as the problems of cumbersome and time-consuming traditional porosity measurement process.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] This invention provides a method for determining the porosity of coarse-grained soil, comprising the following steps:

[0012] The first test trench was excavated on site, and all the coarse-grained soil in the first test trench was removed. The total mass m1 of the coarse-grained soil in the first test trench was measured on site, and the volume of the first test trench was measured on site to be used as the total pore volume V1 of the coarse-grained soil in the first test trench.

[0013] The total mass m2 of all coarse-grained soil in the first trench was measured in the field by placing it in a drainage measurement container. A second trench was excavated at a location adjacent to the first trench, and a sample was taken out from the second trench for laboratory measurement to determine the moisture content w of the coarse-grained soil. The physical state of the sample was consistent with that of the coarse-grained soil in the first trench.

[0014] Based on m1, m2, and w, determine the particle volume V2 of the coarse-grained soil in the first trench, and based on V1 and V2, determine the porosity of the coarse-grained soil.

[0015] Optionally, the particle volume V2 of the coarse-grained soil in the first trench is determined based on m1, m2, and w, including:

[0016] V2=[m2-m1×w / (1+w)] / ρ 水 =m2-m1×w / (1+w);

[0017] In the formula, m1 is the total mass of coarse-grained soil in the first trench; m2 is the total mass of drainage; w is the water content of the coarse-grained soil; ρ 水 Let the density of water be 1.0 g / cm³. 3 .

[0018] Optionally, the porosity of the coarse-grained soil is determined based on V1 and V2, including:

[0019] n = (V1 - V2) / V2 × 100%;

[0020] In the formula, V1 is the total pore volume of the coarse-grained soil in the first trench; V2 is the particle volume of the coarse-grained soil in the first trench.

[0021] Optionally, the site is leveled, and then the first trench is excavated on site. All the coarse soil in the first trench is removed and poured into at least one first open container. The mass of the coarse soil in each first open container is weighed, and the total mass m1 of the coarse soil in the first trench is determined.

[0022] Optionally, the first trench is in the shape of a cuboid or a cylinder, and the dimensions of the first trench in any plane direction are more than 5 times the maximum particle size of the coarse soil, and the vertical depth of the first trench is more than 3 times the maximum particle size of the coarse soil; wherein, the maximum diameter of the coarse soil is the maximum diameter of the coarse soil in the first trench.

[0023] Optionally, the volume of the first test trench is determined by on-site measurement, including: laying an impermeable membrane that covers at least all the inner walls of the first test trench, then injecting water into the first test trench until the water level is flush with the edge of the first test trench, and determining the volume of the first test trench based on the mass of the injected water.

[0024] Optionally, the measuring container for the drainage method includes a container body, a drainage pipe, and a valve, wherein the drainage pipe is connected to an opening in the side wall of the container body, and the valve is disposed on the drainage pipe;

[0025] Using the drainage method, the total drainage mass m2 of all coarse-grained soil in the first test trench placed in the drainage method measuring container was measured on-site, including:

[0026] A1. Close the valve and fill the container with water until the water level exceeds the opening on the side wall of the container body, then stop filling the water.

[0027] A2. Open the valve and allow water exceeding the opening on the side wall of the container to drain freely through the drain pipe until no water flows out of the drain pipe. Then close the valve.

[0028] A3. Pour all the coarse soil in the first test trench into the container body and let it stand for a period of time until the water above the opening on the side wall of the container body is clear.

[0029] A4. Place the water receiving container at the drain outlet of the drain pipe, open the valve, and drain the water above the opening on the side wall of the container body into the water receiving container. Measure the total mass of the water discharged into the water receiving container to obtain the total mass of the drainage m2.

[0030] Optionally, the container body is made of a rigid material that does not undergo volume deformation after coarse-grained soil and water are added.

[0031] Optionally, the depth of the second trench is the same as the depth of the first trench, and the particle size distribution of the sample is the same as that of the coarse-grained soil in the first trench.

[0032] Optionally, the sample is taken out from the second test trench and placed in a second open container for sealed storage. The moisture content of the sample in the second open container is measured in the laboratory to obtain the moisture content w of the coarse-grained soil.

[0033] (III) Beneficial Effects

[0034] The beneficial effects of this invention are:

[0035] The method for measuring the porosity of coarse-grained soil provided by this invention eliminates the representativeness error of particle density caused by "partial sampling" in traditional porosity measurement methods by using all the coarse-grained soil in the first trench for particle volume determination and directly measuring the total volume using the water filling method. This allows the porosity results to more accurately reflect the overall structure of the soil. Key data for determining porosity, namely the total mass m1 of the coarse-grained soil in the first trench, the total pore-containing volume V1 of the coarse-grained soil in the first trench, and the total drainage mass m2, can all be completed on-site in one go, saving a large amount of soil sample transportation and complex laboratory testing, greatly shortening the testing cycle and enabling rapid acquisition of key data. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the on-site excavation of the first and second test trenches according to a specific implementation method;

[0037] Figure 2 This is a schematic diagram of the structure of a measuring container according to a specific embodiment of the drainage method;

[0038] Figure 3 This is a schematic diagram of the structure of the drainage water body located in the drainage method measurement container according to a specific embodiment;

[0039] Figure 4 This is a schematic diagram of a structure in which coarse-grained soil and drainage water are simultaneously located in a drainage method measurement container according to a specific implementation method.

[0040] Figure 5 for Figure 4 A schematic diagram of the structure of the drainage method measuring container after drainage;

[0041] Figure 6 This is a schematic diagram of measuring the volume of the first test trench using the water filling method.

[0042] Explanation of reference numerals in the attached figures

[0043] 1: First test trench;

[0044] 2: The first open container;

[0045] 31: Container body; 32: Drainage pipe; 33: Valve;

[0046] 4: Water receiving container;

[0047] 5: Geomembrane;

[0048] 6: Second test trench;

[0049] 7: Second open container. Detailed Implementation

[0050] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] It should be noted that the porosity measurement method proposed in this invention is particularly suitable for the rapid and accurate on-site determination of the porosity of shallow coarse-grained soil. "Shallow coarse-grained soil" typically refers to coarse-grained soil layers located below the surface, within a depth easily excavated manually or with simple machinery (e.g., within 3 meters). This method effectively solves the problem of porosity determination caused by the uneven composition of such soil layers by optimizing the on-site operation and measurement process.

[0052] This invention provides a method for determining the porosity of coarse-grained soil, comprising the following steps:

[0053] S1. Excavate the first test trench 1 on site and remove all the coarse soil particles in the first test trench 1. Measure the total mass m1 of the coarse soil particles in the first test trench 1 on site.

[0054] Specifically, such as Figure 1 As shown, prepare the first open container 2 and an electronic scale, level the site, then excavate the first trench 1 on site, and remove all the coarse-grained soil from the first trench 1 and pour it into at least one first open container 2. Weigh the mass of the coarse-grained soil in each first open container 2 to determine the total mass m1 of the coarse-grained soil in the first trench 1. In this way, the total mass of the coarse-grained soil in the first trench 1 is measured on site.

[0055] Specifically, the first trench 1 is rectangular or cylindrical in shape, and its dimensions in any planar direction are at least five times the maximum particle size of the coarse-grained soil. The vertical depth of the first trench 1 is at least three times the maximum particle size of the coarse-grained soil. The maximum diameter of the coarse-grained soil refers to the maximum diameter of the particles actually present within the completed first trench 1. This ensures that the excavated trench can accommodate the largest possible particles in the soil and that all soil samples taken fully reflect the true particle size distribution and pore structure of the undisturbed soil, thus laying a reliable physical foundation for the subsequent accurate determination of the porosity of the coarse-grained soil.

[0056] It should be noted that the maximum diameter of coarse-grained soil is an engineering parameter that is dynamically verified and confirmed during the excavation process: before excavation, it can be estimated based on preliminary surveys and the initial size of the trench can be designed accordingly; during the actual widening process, if larger particles are encountered, the trench size needs to be enlarged accordingly to ensure that it always meets the minimum size ratio requirement mentioned above. This dynamic process fundamentally guarantees the representativeness of the volume and structural integrity of the soil samples taken.

[0057] S2. Using the drainage method, measure the total mass m2 of all coarse-grained soil in the first test trench 1 placed in the drainage method measurement container.

[0058] In this way, by taking all the coarse-grained soil in the first trench 1 as a whole for saturated drainage measurement, the overall representativeness of the original data (i.e., total drainage mass) used to determine the particle volume is ensured; and this operation is completed on site in one go, avoiding the errors, time consumption and costs caused by sample reduction, transportation and indoor testing, and providing a reliable data basis for finally determining the porosity that truly reflects the overall pore structure of the soil.

[0059] Preferably, such as Figure 2 As shown, the measuring container for the drainage method includes a container body 31, a drainage pipe 32, and a valve 33. The drainage pipe 32 is connected to an opening in the side wall of the container body 31, and the valve 33 is located on the drainage pipe 32. This design of the drainage method measuring container facilitates drainage method measurements of coarse-grained soil.

[0060] Specifically, such as Figures 2 to 5 As shown, the total mass m2 of all coarse-grained soil in the first test trench 1 placed in the drainage method measurement container was measured on-site using the drainage method, including:

[0061] A1. Close valve 33 and fill the container body 31 with water until the water level exceeds the opening on the side wall of the container body 31, then stop filling the water.

[0062] A2. Open valve 33, and drain pipe 32 will freely discharge water that exceeds the opening on the side wall of container body 31 until no water flows out of drain pipe 32, then close valve 33.

[0063] A3. Pour all the coarse soil particles in the first test trench 1 into the container body 31, let it stand for a period of time until the water above the opening on the side wall of the container body 31 is clear.

[0064] A4. Place the water receiving container 4 at the drain outlet of the drain pipe 32, open the valve 33, and drain the water above the opening on the side wall of the container body 31 into the water receiving container 4. Measure the total mass of the water drained into the water receiving container 4 to obtain the total mass of the drained water m2.

[0065] Steps A1 and A2 work together to establish a precise and stable reference water level (i.e., the lower edge of the side wall opening) within the container body 31, providing a reliable reference for subsequent volume change measurements. Step A3 ensures the soil sample is fully saturated and air between particles is effectively expelled, thus guaranteeing that the volume of water discharged subsequently corresponds exactly to the total volume occupied by the water content of solid particles and coarse soil particles, avoiding measurement errors caused by air bubbles. The total mass of drainage obtained in step A4 can be converted into the total volume occupied by the water content of solid particles and coarse soil particles through water density conversion.

[0066] Furthermore, the container body 31 is made of a rigid material that does not undergo volume deformation after the addition of coarse-grained soil and water. This avoids measurement errors caused by deformation of the container body 31.

[0067] S3. The volume of the first trench 1 is determined by on-site measurement and used as the total pore volume V1 of the coarse-grained soil in the first trench 1.

[0068] The total pore volume of coarse-grained soil is the total volume occupied by the coarse-grained soil itself (including solid particles and the pores between particles).

[0069] Specifically, such as Figure 6 As shown, the volume of the first trench 1 is determined by on-site measurement, including: laying a waterproof membrane 5 covering at least all the inner walls of the first trench 1; then injecting water into the first trench 1 until the water level is flush with the edge of the first trench 1; and determining the volume of the first trench 1 based on the mass of the injected water. By using the water injection method with the waterproof membrane 5 to determine the volume of the first trench 1, the total volume of the soil containing pores can be obtained directly, accurately, and efficiently. Specifically, an impermeable membrane 5 (such as a plastic film) is laid to completely cover the inner wall of the first test trench 1, preventing the injected water from seeping into the surrounding soil. This ensures that the volume of injected water completely and uniquely corresponds to and fills the internal space of the test trench. When the water level is flush with the edge of the test trench, the volume of injected water is strictly equal to the volume of the first test trench 1. By recording the total mass of the injected water and utilizing the physical property that water has a stable density under standard conditions (usually taken as 1.0 g / cm³), the accurate volume of the first test trench 1 can be directly calculated using the formula "Volume of first test trench 1 = Mass of injected water / Density of water". This method transforms complex volume measurement into simple mass measurement, avoiding measurement errors caused by soil wall leakage and irregular shape. It is simple and quick to operate, and all work can be completed on-site without relying on complex instruments or transporting soil samples.

[0070] S4. Excavate a second trench 6 near the first trench 1, and take out a sample from the second trench 6 to determine the moisture content w of the coarse-grained soil in the laboratory.

[0071] Specifically, such as Figure 1 As shown, a second trench 6 is excavated adjacent to the completed first trench 1. The "adjacent location" refers to a position where a sample with a substantially consistent physical state with the coarse-grained soil in the first trench 1 can be obtained. Furthermore, the depth of the second trench 6 is the same as the depth of the first trench 1, and the particle size distribution of the sample is consistent with that of the coarse-grained soil in the first trench 1. Thus, the moisture content value w of the sample can effectively represent the average moisture content of all the coarse-grained soil in the first trench 1.

[0072] The second trench 6 is used to obtain a small amount of moisture content samples. Its planar size can be much smaller than that of the first trench 1. It only needs to be able to take out a representative amount of samples. Usually, its size in any planar direction is not less than twice the maximum particle size of coarse soil to meet the operation requirements.

[0073] Preferably, the edge distance between the second trench 6 and the first trench 1 is no more than 2 meters, and the two are located within the same engineering geological unit.

[0074] Preferably, the sample is taken out from the second test trench 6 and placed in a second open container 7 for sealed storage. The moisture content of the sample in the second open container 7 is then determined in the laboratory to obtain the moisture content w of the coarse-grained soil. This prevents the sample from evaporating moisture and improves the accuracy of the moisture content determination.

[0075] S5. Based on m1, m2 and w, determine the particle volume V2 of the coarse soil in the first trench 1, and based on V1 and V2, determine the porosity of the coarse soil.

[0076] Specifically, based on m1, m2, and w, the particle volume V2 of the coarse-grained soil in the first trench 1 is determined, including:

[0077] V2=[m2-m1×w / (1+w)] / ρ 水 =m2-m1×w / (1+w);

[0078] In the formula, m1 is the total mass of coarse-grained soil in the first trench 1; m2 is the total mass of drainage; w is the water content of the coarse-grained soil; ρ 水 Let the density of water be 1.0 g / cm³. 3 .

[0079] Specifically, the porosity of coarse-grained soil is determined based on V1 and V2, including:

[0080] n = (V1 - V2) / V2 × 100%;

[0081] In the formula, V1 is the total pore volume of the coarse-grained soil in the first trench 1; V2 is the particle volume of the coarse-grained soil in the first trench 1.

[0082] In the coarse-grained soil porosity measurement method provided by this invention, by using all the coarse-grained soil in the first trench 1 for particle volume determination and directly measuring the total volume using the water filling method, the representativeness error of particle density caused by "partial sampling" in traditional porosity measurement methods is eliminated, making the porosity results more realistically reflect the overall soil structure. The key data used to determine porosity, namely the total mass m1 of the coarse-grained soil in the first trench 1, the total pore-containing volume V1 of the coarse-grained soil in the first trench 1, and the total drainage mass m2, can all be completed at the exploration site in one go, saving a large amount of soil sample transportation and complex indoor testing, greatly shortening the testing cycle, and achieving rapid acquisition of key data. Based on the fundamental drainage method and volume replacement principle, and with a cleverly designed dedicated measuring container capable of establishing an accurate benchmark water level, the entire method has low equipment dependence and standardized operation, making it particularly suitable for implementation in field exploration environments. From the standardized design of the first test trench 1 and the use of the impermeable membrane 5, to obtaining representative moisture content samples through the adjacent second test trench 6, every step of the entire process is dedicated to reducing sources of error, thereby ensuring the reliability of the final porosity data as a whole.

[0083] It should be noted that in the coarse-grained soil porosity measurement method provided by the present invention, there is a sequential relationship between S1 and S2, between S1 and S3, and between S1 and S4, but there is no sequential relationship between S2, S3 and S4, and they can be executed simultaneously.

[0084] Example 1

[0085] The coarse-grained soil sample was a mixed gravel layer deposited in the riverbed. Its main mineral components were quartz (density 2.65 g / cm³), feldspar (density 2.70 g / cm³), and a small amount of dark-colored minerals (density >3.0 g / cm³). The particle size ranged from 5 to 40 mm, with a maximum size of 40 mm. The gradation was poor, and the mineral composition was spatially unevenly distributed. The coarse-grained soil sample was in a medium-dense state, with a natural water content (w) of approximately 5%.

[0086] Traditional measurement method: A trench meeting the dimensional requirements (250mm plane dimension, 150mm depth) is excavated in the same area according to specifications. Three independent samples, each weighing approximately 5kg, are selected from different locations (left, center, and right) within the trench and numbered A-1, A-2, and A-3 respectively. The porosity (n) of each sample is determined according to standard methods (sand cone method for dry density, hydrometer bottle method for particle density). trad .

[0087] Sample A-1: ​​Porosity n was measured trad1 =34.2%;

[0088] Sample A-2: Porosity n was measured trad2 =29.8%;

[0089] Sample A-3: Porosity n was measured trad3 =32.1%.

[0090] The three results show significant dispersion, with a range of 4.4%. Their arithmetic mean is taken as the "best estimate" of the porosity of the soil in the trench: n avg = (34.2% + 29.8% + 32.1%) / 3 = 32.0%. This dispersion directly reflects the particle density error caused by partial sampling, which in turn affects the porosity measurement results.

[0091] The method of the present invention measures: Steps S1-S5 of the present invention are performed in the same area, wherein the first trench 1 has a plane dimension of 250mm and a depth of 150mm, the second trench 6 has a plane dimension of 100mm and a depth of 150mm, the water content of the coarse-grained soil measured in S4 is 5.2%, and the final determined porosity is n=31.7%.

[0092] As can be seen, the single measurement result of the method of this invention is very close to the average value of multiple sampling results of the traditional method, with a deviation of only 0.3%. This indicates that the reliability of single sampling test results of the traditional method is low and is greatly affected by the sampling location. The method of this invention obtains a value that is closer to the true porosity of the soil as a whole in a single measurement, which is much closer to the value obtained by the traditional method, which requires multiple sampling and averaging. It is efficient and accurate. The porosity measurement method of this invention eliminates the representativeness problem caused by compositional inhomogeneity to a certain extent.

[0093] Example 2

[0094] The coarse-grained soil to be tested is an alluvial sand and gravel layer, with quartzite as the main mineral component and a small amount of sandstone fragments. The particle size ranges from 0.5 to 60 mm, with a maximum particle size of 60 mm. It is poorly graded, with local enrichment of coarse particles (pebbles) and fine particles (coarse sand). The coarse-grained soil to be tested is in a slightly dense state, with a natural moisture content w of approximately 3%.

[0095] Traditional measurement method: A test trench meeting the dimensional requirements (350mm plane dimension, 200mm depth) is excavated in the same area according to specifications. Four independent samples, each weighing approximately 5kg, are selected from four different locations from left to right within the test trench and numbered B-1, B-2, B-3, and B-4 respectively. The porosity n of each sample is determined according to standard methods (dry density measurement using the sand cone method and particle density measurement using the hydrometer bottle method). trad .

[0096] Sample B-1: Porosity n was measured trad1 =28.2%;

[0097] Sample B-2: Porosity n was measured trad2 =32.9%;

[0098] B-3 sample: Porosity n was measured trad3 =30.1%;

[0099] Sample B-4: Porosity n was measured trad3 =31.4%;

[0100] The three results show significant dispersion, with a range of 4.7%. Their arithmetic mean is taken as the "best estimate" of the porosity of the soil in the trench: n avg = (28.2% + 32.9% + 30.1% + 31.4%) / 4 = 30.7%. This dispersion directly reflects the particle density error caused by partial sampling, which in turn affects the porosity measurement results.

[0101] The method of the present invention measures: Steps S1-S5 of the present invention are performed in the same area, wherein the first trench 1 has a plane dimension of 350mm and a depth of 200mm, the second trench 6 has a plane dimension of 150mm and a depth of 200mm, the water content of the coarse-grained soil measured in S4 is 3.1%, and the final determined porosity is n=30.8%.

[0102] As can be seen, the single measurement result of the method of the present invention is very close to the average value of the multiple sampling results of the traditional method, with a deviation of only 0.1%.

[0103] Example 3

[0104] The coarse-grained soil to be tested is a residual gravel layer. Its main mineral components include strongly weathered rock fragments (easily disintegrating), hard gravel, and a small amount of clay filling. The particle size ranges from 7-80 mm, with a maximum size of 80 mm. Particle strength varies, and some weathered particles soften easily upon contact with water. The mineral composition is spatially unevenly distributed. The coarse-grained soil is in a loose to medium-dense state with uneven moisture content, and the overall moisture content w is approximately 8%.

[0105] Traditional measurement method: A trench meeting the dimensional requirements (400mm plane dimension, 250mm depth) is excavated in the same area according to specifications. Three independent samples, each weighing approximately 5kg, are selected from different locations (left, center, and right) within the trench and numbered C-1, C-2, and C-3 respectively. The porosity (n) of each sample is determined according to standard methods (sand cone method for dry density, hydrometer bottle method for particle density). trad .

[0106] C-1 sample: Porosity n was measured trad1 =36.8%;

[0107] C-2 sample: Porosity n was measured trad2 =33.2%;

[0108] C-3 sample: Porosity n was measuredtrad3 =42.1%.

[0109] The three results exhibited significant dispersion, with a range of 8.9%. Their arithmetic mean was taken as the "best estimate" of the porosity of the soil in the trench: n avg = (36.8% + 33.2% + 42.1%) / 3 = 37.4%. This dispersion directly reflects the particle density error caused by partial sampling, which in turn affects the porosity measurement results.

[0110] The method of the present invention measures: Steps S1-S5 of the present invention are performed in the same area, wherein the first trench 1 has a plane dimension of 400mm and a depth of 250mm, the second trench 6 has a plane dimension of 160mm and a depth of 250mm, the water content of the coarse-grained soil measured in S4 is 7.2%, and the final determined porosity is n=36.8%.

[0111] It can be seen that the single measurement result of the method of the present invention is close to the average value of the multiple sampling results of the traditional method, with a deviation of 0.6%.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the porosity of coarse-grained soil, characterized in that, Includes the following steps: The first trench (1) was excavated on site, and all the coarse soil in the first trench (1) was removed. The total mass m1 of the coarse soil in the first trench (1) was measured on site, and the volume of the first trench (1) was measured on site as the total pore volume V1 of the coarse soil in the first trench (1). The total mass m2 of all coarse soil particles in the first trench (1) was measured in the field by the drainage method. A second trench (6) was excavated at a location adjacent to the first trench (1), and a sample was taken out from the second trench (6) to determine the moisture content w of the coarse soil particles in the laboratory. The physical state of the sample was consistent with the physical state of the coarse soil particles in the first trench (1). Based on m1, m2 and w, determine the particle volume V2 of the coarse soil in the first trench (1), and determine the porosity of the coarse soil based on V1 and V2.

2. The method for determining the porosity of coarse-grained soil according to claim 1, characterized in that, Based on m1, m2, and w, determine the particle volume V2 of the coarse-grained soil in the first trench (1), including: V2 = [m2 - m1 × w / (1 + w)] / ρ 水 =m2 - m1×w / (1+w); In the formula, m1 is the total mass of coarse-grained soil in the first trench (1); m2 is the total mass of drainage; w is the water content of the coarse-grained soil; ρ 水 Let the density of water be 1.0 g / cm³. 3 .

3. The method for determining the porosity of coarse-grained soil according to claim 1, characterized in that, Based on V1 and V2, determine the porosity of coarse-grained soil, including: n = (V1 - V2) / V2 × 100%; In the formula, V1 is the total volume of the coarse-grained soil with pores in the first trench (1); V2 is the volume of the coarse-grained soil particles in the first trench (1).

4. The method for determining the porosity of coarse-grained soil according to claim 1, characterized in that, Level the site, then excavate the first trench (1) on site, and take out all the coarse soil in the first trench (1) and pour it into at least one first open container (2). Weigh the mass of the coarse soil in each first open container (2) and determine the total mass m1 of the coarse soil in the first trench (1).

5. The method for determining the porosity of coarse-grained soil according to claim 1, characterized in that, The first trench (1) is in the shape of a cuboid or cylinder. The dimensions of the first trench (1) in any plane direction are more than 5 times the maximum particle size of the coarse soil, and the vertical depth of the first trench (1) is more than 3 times the maximum particle size of the coarse soil. The maximum diameter of the coarse soil is the maximum diameter of the coarse soil in the first trench (1).

6. The method for determining the porosity of coarse-grained soil according to claim 1, characterized in that, The volume of the first test trench (1) was determined by on-site measurement, including: Lay an impermeable membrane (5) covering at least all the inner walls of the first test trench (1) inside the first test trench (1), and then inject water into the first test trench (1) until the water surface is level with the edge of the first test trench (1). Determine the volume of the first test trench (1) based on the mass of the injected water.

7. The method for determining the porosity of coarse-grained soil according to claim 1, characterized in that, The measuring container used for the drainage method includes a container body (31), a drainage pipe (32) and a valve (33). The drainage pipe (32) is connected to the side wall opening of the container body (31), and the valve (33) is installed on the drainage pipe (32). The total mass m2 of all coarse-grained soil in the first trench (1) was measured in the field using the drainage method, including: A1. Close valve (33), fill the container body (31) with water until the water level exceeds the opening on the side wall of the container body (31), then stop filling the water; A2. Open valve (33) and drain pipe (32) freely discharge water that exceeds the opening on the side wall of container body (31) until no water flows out of drain pipe (32), then close valve (33). A3. Pour all the coarse soil in the first test trench (1) into the container body (31), let it stand for a period of time until the water above the opening on the side wall of the container body (31) is clear. A4. Place the water receiving container (4) at the drain outlet of the drain pipe (32), open the valve (33), and drain the water above the opening on the side wall of the container body (31) into the water receiving container (4). Measure the total mass of the water discharged into the water receiving container (4) to obtain the total mass of the drainage m2.

8. The method for determining the porosity of coarse-grained soil according to claim 7, characterized in that, The container body (31) is made of a rigid material that does not deform in volume after coarse soil and water are added.

9. The method for determining the porosity of coarse-grained soil according to claim 1, characterized in that, The depth of the second trench (6) is the same as the depth of the first trench (1), and the particle size distribution of the sample is the same as that of the coarse soil in the first trench (1).

10. The method for determining the porosity of coarse-grained soil according to claim 1, characterized in that, The sample was taken out from the second test trench (6) and sealed in the second open container (7). The moisture content of the sample in the second open container (7) was measured in the laboratory to obtain the moisture content w of the coarse-grained soil.

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