An experimental device for testing maximum suction of sand and an experimental method thereof

Abstract

The application discloses an experimental device for testing maximum suction stress of sand and an experimental method thereof, belongs to the technical field of geotechnical engineering, and solves the problem that the maximum suction stress of sand cannot be measured in the prior art; the experimental device comprises a base fixed on a table top, a channel is formed in the end face of the base; a sample measuring cylinder is horizontally arranged in the channel and used for containing a sand sample; the sample measuring cylinder comprises a first measuring cylinder and a second measuring cylinder which are detachably connected, the second measuring cylinder is located directly below the first measuring cylinder and is slidingly arranged in the channel; and a sample pulling assembly is used for sliding the second measuring cylinder. The experimental device is simple, convenient to operate and clear in principle, the length of the sand sample falling under the action of a self-weight load can be measured, the maximum suction stress of sand under different water contents and relative compactness states can be calculated through a theoretical formula, the method is reasonable, the experiment can be repeated for many times, and the reliability is high.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, specifically to an experimental apparatus and method for testing the maximum absorbance stress of sand. Background Technology

[0002] In geotechnical engineering, unsaturated soil affects the lateral earth pressure and stability of retaining structures, slope stability and landslides induced by climate change, and the bearing capacity of shallow foundations under varying moisture conditions. Engineering practice shows that the pore pressure in unsaturated soil is generally tensile stress, and its contribution to the total stress depends on the soil saturation and pore size distribution. However, the pore pressure in unsaturated soil is not necessarily a component of the total stress, making the analysis of the stress state of unsaturated soil far more complex than that of saturated soil. The net interparticle force generated between unsaturated soil particles (such as sand and silt) under the combined action of negative pore water pressure and surface tension at the contact surfaces of pore water, pore air, and solid particles is termed "absorption stress." Macroscopically, absorption stress manifests as tensile force, causing soil particles within its action range to move closer together.

[0003] Existing methods for measuring and calculating maximum absorbed stress mostly rely on a microscopic approach, estimating the value by considering the microscopic forces between unsaturated soil and spherical soil particles under ideal conditions. However, this method requires considering the particle size of the soil sample, and the theoretical analysis involves too many assumptions leading to significant deviations. Measuring the maximum absorbed stress of a soil sample using specialized unsaturated soil testing equipment to measure effective stress parameters and matrix suction at sample failure is complex, time-consuming, expensive, and difficult to implement. Applying an external load to tension the soil within a pulling device and measuring the maximum absorbed stress based on the applied load also introduces errors due to friction between the device and the platform during the pulling process. This is particularly problematic for sand samples, where the absorbed stress itself is extremely small, making it difficult to accurately measure the maximum absorbed stress using external loads. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides an experimental apparatus and method for testing the maximum absorbance stress of sand, thus solving the problem that the existing technology has difficulty in measuring the maximum absorbance stress of sand.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] On one hand, an experimental apparatus for testing the maximum absorption stress of sand is provided, comprising: a platform, which is placed horizontally; a base, which is fixed on the platform and has a channel on its end face; a sample measuring cylinder, which is horizontally arranged in the channel for holding a sand sample; the sample measuring cylinder includes a first measuring cylinder and a second measuring cylinder, which are slidably connected, and the second measuring cylinder is located directly below the first measuring cylinder and slidably arranged on the lower half of the channel; and a sample pulling assembly, which is used to drive the second measuring cylinder to slide.

[0007] In this design, the sample measuring cylinder is equipped with a scale. During the process of compacting the sand sample in the sample measuring cylinder, the scale facilitates the control of the relative density of the sand sample. The sample measuring cylinder is divided into a first measuring cylinder and a second measuring cylinder. When the second measuring cylinder is pulled, the bottom of the sand sample can be suspended in the air, forming a cantilever beam structure. Thus, when the sand sample begins to fall, the maximum absorption stress of the sand can be obtained by converting the bending moment of the cantilever beam.

[0008] Furthermore, the first and second graduated cylinders are fitted with clamping rings. The clamping rings restrict the circumferential displacement of the first and second graduated cylinders, facilitating the assembly of the sample graduated cylinders.

[0009] Furthermore, the sample measuring cylinder also includes a soil compactor, which includes a pressure rod with a cylindrical pressure head fixed to one end. The diameter of the pressure head is the same as the inner diameter of the first and second measuring cylinders. The soil compactor facilitates the compaction of sand samples.

[0010] Furthermore, the sample pulling assembly includes a pull wire connected to the bottom cover of the second measuring cylinder. Pulling the pull wire causes the second measuring cylinder to slide within the channel. The pull wire design is simple, convenient, and practical.

[0011] Furthermore, the sample pulling assembly also includes a clamping rod located inside the second measuring cylinder. A connection hole is provided on the bottom plate of the second measuring cylinder, and one end of the pull wire passes through the connection hole and is fixedly connected to the clamping rod.

[0012] Furthermore, the sample pulling assembly also includes a fixed pulley, which is fixed on the table surface and located on the central axis of the channel. The free end of the pull wire passes over the fixed pulley. The fixed pulley facilitates control of the direction of movement of the pull wire, and this placement of the fixed pulley makes it easier for the pull wire to coincide with the center line of the second graduated cylinder, resulting in smoother movement of the second graduated cylinder.

[0013] On the other hand, an experimental method for testing the maximum absorption stress of sand includes the following steps:

[0014] S1. Take a dried sand sample and measure the specific gravity G of the sand sample. s Minimum porosity e min and maximum porosity e max .

[0015] S2, Add a substance with density ρ to the sand sample. ω A sand sample with a water content of ω was prepared using pure distilled water.

[0016] S3. Connect the first and second measuring cylinders to form a sample measuring cylinder, apply lubricant evenly to the inside of the sample measuring cylinder, and place it horizontally in the channel of the base.

[0017] Using a lubricant can reduce the influence of the adsorption force and frictional resistance between the sand sample and the inner wall of the sample cylinder, thereby reducing experimental errors.

[0018] S4. Fill the sand sample into the sample measuring cylinder in layers and compact it. Each time you compact it, use the scale value on the sample measuring cylinder to control the relative density of the sand sample to D. r .

[0019] S5. Pull the second graduated cylinder until the sand sample falls from the first graduated cylinder.

[0020] During the process of pulling the second measuring cylinder, the exposed sand sample is in a suspended state and can be regarded as a cantilever beam.

[0021] S6. Measure the length l of the fallen soil sample by observing the scale on the first measuring cylinder.

[0022] S7. Calculate the maximum absorption stress of the sand sample:

[0023]

[0024] Among them, G s ρ is the specific gravity, ω is the moisture content, g is the acceleration due to gravity, and ρ is the velocity. ω Let l be the density of pure distilled water, l be the length of the dropped soil sample, S be the cross-sectional area of ​​the sample measuring cylinder, y be the cross-sectional height of the sample measuring cylinder, and I be the density of pure distilled water. z The moment of inertia of the cross section of the measuring cylinder, e min Minimum void ratio, e max For maximum void ratio, D r This represents the relative density of the sand sample.

[0025] S8. Complete the experiment.

[0026] Furthermore, in step S1, the specific gravity G s The minimum porosity e was determined by the specific gravity bottle method. min and maximum porosity e max It was measured using the graduated cylinder method.

[0027] Furthermore, in step S2, when preparing the sand sample with a moisture content of ω, the temperature of the pure distilled water used is 4℃, which also allows the entire experimental environment temperature to be controlled at 4℃. 4℃ is the temperature at which pure distilled water has the highest density; at this temperature, the intermolecular distance of pure distilled water is the smallest, and the interaction between water molecules is the largest. This maximizes the stability and relative consistency of the pure distilled water, making the experimental results more accurate and comparable. Moreover, using pure distilled water at 4℃ reduces the influence of temperature on the moisture absorption or loss process of the sample, helping to maintain the repeatability and accuracy of the experiment.

[0028] Furthermore, in step S3, petrolatum is used as the lubricant. Petrolatum is a paraffin-based grease that is insoluble in water. Using petrolatum as a lubricant ensures that water and lubricant do not mix during the test, thus maintaining the accuracy of the experiment. Moreover, petrolatum has good compatibility with sand samples; as an inert substance, it will not chemically react with the sand samples, nor will it change the properties or moisture content of the samples, improving the reliability of the experiment.

[0029] This invention discloses an experimental apparatus and method for testing the maximum absorption stress of sand, the beneficial effects of which are:

[0030] The experimental apparatus of this invention is simple, easy to operate, and has a clear principle. It measures the length of a sand sample falling under its own weight. The maximum absorption stress of sand under different moisture contents and relatively dense states can be calculated by theoretical formulas. The method is reasonable, can be repeated multiple times, and has high reliability. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the experimental setup;

[0032] Figure 2 This is a schematic diagram showing the movement of the second graduated cylinder;

[0033] Figure 3 This is a structural diagram of the countertop;

[0034] Figure 4 This is a schematic diagram of the base structure;

[0035] Figure 5 This is a schematic diagram of the structure of the measuring cylinder for testing;

[0036] Figure 6 This is a schematic diagram of the hoop structure;

[0037] Figure 7 This is a schematic diagram of the soil compactor.

[0038] Figure 8 This is a schematic diagram of the clamp's structure;

[0039] Figure 9 This is a schematic diagram of the wire structure;

[0040] Figure 10 This is a schematic diagram of a fixed pulley.

[0041] Figure 11 This is a side view of the measuring cylinder.

[0042] Figure 12 This is a mechanical structure diagram of a sand sample.

[0043] Figure 13 This is a schematic diagram illustrating the mechanical principles of a sand sample.

[0044] Figure 14 Shear force diagram of sand sample;

[0045] Figure 15 The bending moment diagram of the sand sample is shown.

[0046] The components are as follows: 1. Platform; 101. First through hole; 102. Second through hole; 103. Third through hole; 104. Fourth through hole; 2. Base; 201. Bottom cover; 202. Channel; 203. Wing plate; 204. First threaded hole; 205. Second threaded hole; 3. Sample measuring cylinder; 301. First measuring cylinder; 302. Second measuring cylinder; 303. Hoop ring; 304. Soil compactor; 305. Connecting hole; 4. Sample pulling assembly; 401. Clamping rod; 402. Pull wire; 403. Fixed pulley. Detailed Implementation

[0047] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0048] Example 1

[0049] refer to Figures 1 to 11 This embodiment provides an experimental apparatus for testing the maximum absorption stress of sand, including a platform 1, a base 2, a sample measuring cylinder 3, and a sample pulling assembly 4.

[0050] refer to Figures 1-3 The tabletop 1 can be a horizontally placed tabletop on the ground, used to support the fixed base 2 and the sample pulling assembly 4.

[0051] refer to Figure 4 The base 2 has a rectangular structure and is fixed on the platform 1.

[0052] Both sides of the base 2 are provided with wing plates 203. The end faces of the two wing plates 203 are respectively provided with a first threaded hole 204 and a second threaded hole 205. The middle part of the platform 1 is symmetrically provided with a first through hole 101 and a second through hole 102. The first threaded hole 204 and the second threaded hole 205 are respectively bolted to the first through hole 101 and the second through hole 102.

[0053] A cylindrical channel 202 is horizontally opened on the end face of the base 2, and the channel 202 is used for the sliding of the second measuring cylinder 302.

[0054] refer to Figure 2 and Figure 5 The sample measuring cylinder 3 is used to hold the sand sample and is horizontally set in the channel 202. The sample measuring cylinder 3 includes, but is not limited to, square measuring cylinders and round measuring cylinders. In this embodiment, the sample measuring cylinder 3 is preferably a round measuring cylinder. The sample measuring cylinder 3 is divided into two parts along the axial direction: a first measuring cylinder 301 and a second measuring cylinder 302. The first measuring cylinder 301 and the second measuring cylinder 302 are respectively provided with mutually cooperating grooves and slide rails. The first measuring cylinder 301 and the second measuring cylinder 302 are slidably connected through the grooves and slide rails. The first measuring cylinder 301 is detachably fixed in the channel 202. The second measuring cylinder 302 is located directly below the first measuring cylinder 301 and is slidably set on the lower half of the channel 202.

[0055] refer to Figure 11 The sample measuring cylinder 3 is divided into a first measuring cylinder 301 and a second measuring cylinder 302 in the middle. This allows the bottom of the sand sample to be suspended in the air during the pulling of the second measuring cylinder 302, forming a cantilever beam structure. Thus, when the sand sample begins to fall, the maximum absorption stress of the sand can be obtained by converting the bending moment of the cantilever beam.

[0056] Preferred but not limited to, for reference Figure 6 The first measuring cylinder 301 and the second measuring cylinder 302 are fitted with clamping rings 303. The clamping rings 303 restrict the circumferential displacement of the first measuring cylinder 301 and the second measuring cylinder 302, which facilitates the assembly of the sample measuring cylinder 3. When the second measuring cylinder 302 is pulled, the clamping rings 303 can be removed to avoid affecting the axial sliding of the second measuring cylinder 302 between the first measuring cylinders 301.

[0057] The bottom cover 201 of the first measuring cylinder 301 is removable. The removed bottom cover 201 is fixed to the upper half of the channel 202. (Refer to...) Figure 4 This arrangement prevents the first measuring cylinder 301 from moving within channel 202 during the movement of the second measuring cylinder 302.

[0058] To better compact the sand sample, refer to Figure 7The sample measuring cylinder 3 may also include a soil compactor 304 for use in conjunction with it. The soil compactor 304 includes a pressure rod, and a cylindrical pressure head is fixed on one end of the pressure rod. The diameter of the pressure head is the same as the inner diameter of the first measuring cylinder 301 and the second measuring cylinder 302. The first measuring cylinder 301 is equipped with a scale. During the process of compacting the sand sample in the sample measuring cylinder 3, the scale is used to facilitate the control of the relative density of the sand sample.

[0059] refer to Figures 8-10 The sample pulling assembly 4 is used to drive the second measuring cylinder 302 to slide. The sample pulling assembly 4 includes a clamping rod 401, a pull wire 402 and a fixed pulley 403.

[0060] The clamping rod 401 is located inside the second measuring cylinder 302. The bottom plate of the second measuring cylinder 302 is provided with a connecting hole 305. One end of the pull wire 402 passes through the connecting hole 305 and is fixedly connected to the clamping rod 401. By manually pulling the pull wire 402, the clamping rod 401 is driven, and the clamping rod 401 drives the second measuring cylinder 302 to move. The structure is simple, convenient and practical.

[0061] The fixed pulley 403 is fixed on the table 1, and the free end of the pull line 402 passes around the hub of the fixed pulley 403. The fixed pulley 403 is designed to facilitate control of the movement direction of the pull line 402.

[0062] Specifically, a third through hole 103 and a fourth through hole 104 are symmetrically provided on the end of the platform 1. The fixed pulley 403 is rotatably mounted on its matching fixed plate. The fixed plate of the fixed pulley 403 is provided with a third threaded hole and a fourth threaded hole. The third through hole 103 and the fourth through hole 104 are respectively bolted to the third threaded hole and the fourth threaded hole.

[0063] Preferably, but not limited to, the fixed pulley 403 in this embodiment is located on the central axis of the channel 202. This arrangement of the fixed pulley 403 facilitates the alignment of the pull line 402 with the center line of the second measuring cylinder 302, making the movement of the second measuring cylinder 302 smoother.

[0064] Preferably, but not limited to, the dimensions of this solution can be as follows:

[0065] The countertop 1 is 1000mm long, 400mm wide, and 6mm thick.

[0066] The diameters of the first through hole 101, the second through hole 102, the third through hole 103, and the fourth through hole 104 are 10 mm.

[0067] The base 2 is 200mm long, 50mm wide, and 183mm high. The wing plate 203 is 50mm long, 80mm wide, and 20mm high. The diameters of the first threaded hole 204 and the second threaded hole 205 are 10mm.

[0068] The first measuring cylinder 301 has an inner diameter of 40mm, an outer diameter of 60mm, and a length of 490mm. The bottom cover 201 is a semicircle with a diameter of 60mm and a thickness of 10mm.

[0069] The second measuring cylinder 302 has an inner diameter of 40mm, an outer diameter of 60mm, a length of 500mm, a bottom thickness of 10mm, and a connecting hole 305 with a diameter of 4mm; the hoop 303 has a wall thickness of 5mm.

[0070] The soil compactor 304 has a compactor head diameter of 40mm and a height of 5mm, and a compactor bar diameter of 10mm and a height of 55mm.

[0071] The diameter of the lever 401 is 2mm and the length is 25mm.

[0072] The 402 drawstring is a 700mm long nylon thread.

[0073] The fixing plate of the positioning pulley is 80mm long, 80mm wide, and 2mm high. The diameter of the pulley is 20mm and the thickness is 10mm.

[0074] Example 2

[0075] This embodiment is based on Embodiment 1 with further limitations. The specific improvement lies in how to conduct the experiment to test the maximum absorption stress of sand. Other parts not mentioned refer to Embodiment 1 or the prior art.

[0076] This embodiment provides an experimental method for testing the maximum absorption stress of sand, including the following steps:

[0077] S1. Take a dried sand sample and measure the specific gravity G of the sand sample. s Minimum porosity e min and maximum porosity e max .

[0078] Specific gravity G s The minimum porosity e was determined by the specific gravity bottle method. min and maximum porosity e max It was measured using the graduated cylinder method.

[0079] S2, Add a substance with density ρ to the sand sample. ω A sand sample with a water content of ω was prepared using pure distilled water.

[0080] Preferably, but not limited to, this embodiment uses pure distilled water at a temperature of 4°C; however, the entire experimental environment temperature can also be controlled at 4°C. 4°C is the temperature at which pure distilled water has the highest density, at which point the density of pure distilled water is 1 g / cm³. 3At 4°C, the intermolecular distance is minimal, and the interaction between water molecules is maximized, ensuring the stability and relative consistency of pure distilled water to the greatest extent possible, making the test results more accurate and comparable. Furthermore, pure distilled water at 4°C reduces the influence of temperature on the moisture absorption or loss process of the sample, helping to maintain the repeatability and accuracy of the test.

[0081] S3. Connect the first measuring cylinder 301 and the second measuring cylinder 302 to form a sample measuring cylinder 3, and apply lubricant evenly to the inner side of the sample measuring cylinder 3 and place it horizontally in the channel 202 of the base 2.

[0082] Using a lubricant can reduce the influence of the adsorption force and frictional resistance between the sand sample and the inner wall of the sample measuring cylinder 3, thereby reducing experimental errors.

[0083] Preferably, but not limited to, the lubricant used in this embodiment is petrolatum. Petrolatum is a paraffinic grease that is insoluble in water. Using petrolatum as a lubricant ensures that water and lubricant do not mix during the test, thus maintaining the accuracy of the test. Furthermore, petrolatum has good compatibility with sand samples; as an inert substance, it will not chemically react with the sand samples, nor will it change the properties or moisture content of the samples, improving the reliability of the experiment.

[0084] S4. Place the sand sample into the sample measuring cylinder 3 in layers and compact it. Each time you compact it, use the scale value on the sample measuring cylinder 3 to control the relative density of the sand sample to D. r .

[0085] S5. Pull the second measuring cylinder 302 until the sand sample falls from the first measuring cylinder 301.

[0086] Specifically, the pull wire 402 on the positioning pulley is pulled at a constant speed, causing the second measuring cylinder 302 to slide within the channel 202. During the process of pulling the second measuring cylinder 302, the exposed sand sample is in a suspended state, which can be regarded as a cantilever beam.

[0087] S6. Measure the length l of the fallen soil sample by observing the scale on the first measuring cylinder 301.

[0088] S7. Calculate the maximum absorption stress of the sand sample:

[0089]

[0090] Among them, G s ρ is the specific gravity, ω is the moisture content, g is the acceleration due to gravity, and ρ is the velocity. ω Let l be the density of pure distilled water, l be the length of the dropped soil sample, S be the cross-sectional area of ​​the sample measuring cylinder, y be the cross-sectional height of the sample measuring cylinder, and I be the density of pure distilled water. z The moment of inertia of the cross section of the measuring cylinder, e min Minimum void ratio, e maxFor maximum void ratio, D r This represents the relative density of the sand sample.

[0091] S8. Complete the experiment.

[0092] The specific principle is as follows:

[0093] Referring to 11, it can be seen that as the second measuring cylinder 302 moves under the traction of the tension wire 402, the compacted soil inside the sample measuring cylinder 3 is gradually exposed to the outside, and its mechanical structure is referenced. Figure 12 The exposed soil is considered a cantilever beam, and the end face is considered the cantilever end. Refer to the mechanical principle diagram. Figure 13 As the second measuring cylinder 302 moves forward under the traction of the pull wire 402, the soil on the cantilever generates a bending moment M on the cantilever end under the action of gravity q = mg. When the soil extends a certain distance l, the vertical force generated is greater than the net intergranular force at the cantilever end, causing the soil on the cantilever to fall off. The falling length is l. During this process, the shear force diagram and bending moment diagram are referenced. Figure 14 and Figure 15 .

[0094] Based on the above mechanical structural analysis, the maximum absorbent stress generated at the fracture surface can be equivalent to:

[0095]

[0096] in, q = mg, m = ρV = ρSl,

[0097] e = (1-D) r )e max +D r e min , .

[0098] m: mass of fallen sand, ρ: density of sand, e: void ratio of sand, g: acceleration due to gravity, ρ ω The density of pure distilled water at 4℃, D r The relative density of sandy soil, e max : Maximum void ratio of sand sample, e min Minimum void ratio of sand sample, G s : Specific gravity of sand, ω: Moisture content of sand, l: Length of dropped soil sample, S: Cross-sectional area of ​​the sample measuring cylinder, y: Height of the sample measuring cylinder, I z : Moment of inertia of the cross section of the measuring cylinder.

[0099] The maximum suction stress σ is obtained by combining the above formulas. max Calculation formula:

[0100]

[0101] Specifically, when the sample measuring cylinder 3 is a circular measuring cylinder, the cross-section of the sample measuring cylinder is circular, therefore:

[0102]

[0103]

[0104] Where D is the diameter of the sample measuring cylinder 3.

[0105] When the sample measuring cylinder 3 is a square measuring cylinder, the cross-section of the sample measuring cylinder is rectangular, therefore:

[0106] m=ρV=ρbhl、

[0107]

[0108] Where b: width of cross section 3 of the sample measuring cylinder, and h: height of cross section 3 of the sample measuring cylinder.

[0109] In this embodiment, a circular sample measuring cylinder 3 is preferably used. The experimental method in this embodiment can be repeated multiple times to obtain the maximum absorption stress σ of the prepared sand sample under different moisture contents ω. max .

[0110] Specifically, sand samples with moisture contents ω of 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, and 22% were prepared and the experimental setup was assembled. The sand sample with the lowest moisture content ω1 was selected first and processed according to step S4, with three compaction passes. After compaction, the soil sample was positioned approximately 25 cm on the ruler to control the relative density D of the soil sample. r =2 / 3, observe the scale of the initial soil sample in the upper sample measuring cylinder 3 after compaction, x1 = 24.8cm. Pull the string 402 at a uniform speed to ensure the second measuring cylinder 302 slides at a uniform speed. When the soil in the sample measuring cylinder 3 begins to fall, stop pulling. Observe the final scale value of the soil sample in the first measuring cylinder 301 after falling, x2 = 21.6cm. The length of the soil sample falling can be calculated as l1 = x1 - x2 = 3.2cm. Thus, the first set of experimental data ω1, l1 is obtained. Subsequently, change the soil samples with different moisture contents, and follow the above operation to compact the soil samples in layers with moisture contents of ω2, ω3, ω4, ω5, ω6, ω7, ω8, ω9, ω 10 ω 11The soil samples were sized at percentages of 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, and 22%, respectively. The lengths of the fallen soil samples were measured as follows: l2 = 5.1 cm, l3 = 4.1 cm, l4 = 4.5 cm, l5 = 4.6 cm, l6 = 4.8 cm, l7 = 4.2 cm, l8 = 3.7 cm, l9 = 3.7 cm, and l... 10 =3.9cm, l 11 = 3.8cm. Substituting the above experimental data into the formula in S7, Where g is the acceleration due to gravity, ρ ω The density of pure distilled water at 4℃ is used to determine the maximum absorbent stress σ of the prepared sand samples under different moisture contents ω. max .

[0111] The experimental setup of this scheme is simple, easy to operate, and has a clear principle. Based on the length of the sand sample falling under its own weight, the maximum absorption stress of sand under different moisture contents and relatively dense conditions can be calculated by theoretical formula. The method is reasonable, can be repeated multiple times, and has high reliability.

[0112] Although specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. An experimental method for testing the maximum absorption stress of sand, characterized in that, Includes the following steps: S1. Take a dried sand sample and measure its specific gravity. G s Minimum porosity e min and maximum porosity e max ; S2, Add a density of [missing information] to the sand sample. The pure distilled water is prepared with a water content of Sandy soil sample; S3. Connect the first and second measuring cylinders to form a sample measuring cylinder, and apply lubricant evenly to the inside of the sample measuring cylinder and place it horizontally in the channel of the base. S4. Layer the sand sample into the measuring cylinder and compact it. During each compaction, use the graduations on the measuring cylinder to control the relative density of the sand sample. ; S5. Pull the second graduated cylinder until the sand sample falls from the first graduated cylinder; S6. Measure the length of the fallen soil sample by observing the scale on the first graduated cylinder. l ; S7. Calculate the maximum absorption stress of the sand sample: in, For specific gravity, For moisture content, g For gravitational acceleration, The density of pure distilled water, l S is the length of the fallen soil sample, S is the cross-sectional area of ​​the sample measuring cylinder, and y is the cross-sectional height of the sample measuring cylinder. For the moment of inertia of the cross section of the measuring cylinder, e min For minimum porosity, e max For maximum porosity, This represents the relative density of the sand sample. S8. Complete the experiment; The experimental apparatus for testing the maximum absorption stress of sand includes: The tabletop (1) is placed horizontally; The base (2) is fixed on the table (1), and a channel (202) is provided on the end face of the base (2). A sample measuring cylinder (3) is horizontally arranged in the channel (202) for holding a sand sample. The sample measuring cylinder (3) includes a first measuring cylinder (301) and a second measuring cylinder (302). The first measuring cylinder (301) and the second measuring cylinder (302) are slidably connected, and the second measuring cylinder (302) is located directly below the first measuring cylinder (301) and is slidably arranged on the lower half of the channel (202). The sample pulling assembly (4) is used to drive the second measuring cylinder (302) to slide.

2. The experimental method for testing the maximum absorption stress of sand according to claim 1, characterized in that, The first measuring cylinder (301) and the second measuring cylinder (302) are fitted with clamping rings (303).

3. The experimental method for testing the maximum absorption stress of sand according to claim 1, characterized in that, The sample measuring cylinder (3) also includes a soil presser (304), which includes a pressure rod. A cylindrical pressure head is fixed to one end of the pressure rod. The diameter of the pressure head is the same as the inner diameter of the first measuring cylinder (301) and the second measuring cylinder (302).

4. The experimental method for testing the maximum absorption stress of sand according to claim 1, characterized in that, The sample pulling assembly (4) includes a pull wire (402), which is connected to the bottom cover of the second measuring cylinder (302). Pulling the pull wire (402) causes the second measuring cylinder (302) to slide in the channel (202).

5. The experimental method for testing the maximum absorption stress of sand according to claim 4, characterized in that, The sample pulling assembly (4) also includes a clamping rod (401), which is located inside the second measuring cylinder (302). A connecting hole (305) is provided on the bottom plate of the second measuring cylinder (302), and one end of the pull wire (402) passes through the connecting hole (305) and is fixedly connected to the clamping rod (401).

6. The experimental method for testing the maximum absorption stress of sand according to claim 5, characterized in that, The sample pulling assembly (4) also includes a fixed pulley (403), which is fixed on the table (1) and located on the central axis of the channel (202). The free end of the pull line (402) passes around the fixed pulley (403).

7. The experimental method for testing the maximum absorption stress of sand according to claim 1, characterized in that, The specific gravity in step S1 G s The minimum void ratio was determined by the specific gravity bottle method. e min and maximum porosity e max It was measured using the graduated cylinder method.

8. The experimental method for testing the maximum absorption stress of sand according to claim 1, characterized in that, Step S2 configures the moisture content to be... The temperature of the pure distilled water used for the sand sample was 4℃.

9. The experimental method for testing the maximum absorption stress of sand according to claim 1, characterized in that, In step S3, petrolatum is used as the lubricant.

Images