Triaxial sample preparation device based on underwater deposition method

Abstract

The triaxial sample preparation device based on the underwater deposition method comprises a saturator, a support, a water containing base, a vacuum pump and a three-valve mechanism, the saturator is a container used for vacuumizing and saturating underwater sandy soil, a pipeline connected with a pressure-resistant pipe is arranged on a top cover of the saturator, and a first valve is arranged on the top cover of the saturator to control on-off. The other end of the pressure-resistant pipe is connected with a vacuum pump. A pipeline connected with the rubber pipe is arranged below the saturator, and a second valve is installed to control on-off. The three-valve mechanism is a three-axis sample preparation mold, and a water containing base is installed above the three-valve mechanism. The saturator is fixed above the three-valve mechanism and the water containing base through a support. According to the device, the working procedure of preparing the triaxial sample by a traditional underwater deposition method is simplified, the working procedures of heating the sample, injecting air-free water, cooling overnight, transferring a sand solution between a flask and a funnel and the like are omitted, the sample preparation time is greatly shortened, the test operation threshold is reduced, and the test reliability is improved.

Description

Technical Field

[0001] This utility model relates to a triaxial sample preparation device for sand, and more particularly to a triaxial sample preparation device based on underwater sedimentation method, belonging to the technical field of indoor geotechnical testing equipment. Background Technology

[0002] Underwater sedimentation is a method for preparing triaxial sand samples. Proposed as early as the 1980s, this method involves immersing the sand in a water-filled container, boiling it to remove air bubbles, and then directly depositing the sample underwater within a three-valve membrane. Because it employs sedimentation, underwater sedimentation is considered a good way to recreate the sand deposition process. Furthermore, this method can be used to prepare sand samples with a full range of compaction, from loose to dense sand. However, despite decades of development, this method has not achieved large-scale application. The reasons for this are as follows:

[0003] (1) Although the underwater sedimentation method has a complete theory, it requires specialized equipment to be implemented in practice, which has a high threshold for implementation;

[0004] (2) The underwater sedimentation method requires open flame heating, which poses potential risks and is not easy to promote in the laboratory;

[0005] (3) The underwater sedimentation method has a complex sample preparation process, including sample heating, injection of degassing water, overnight cooling, and transfer of sand solution between flask and funnel, which takes a long time to prepare the sample.

[0006] (4) The density of the sample prepared by the underwater sedimentation method is controlled by the sedimentation height of sand in water, but the sedimentation height in water is difficult to guarantee.

[0007] To address the aforementioned issues and promote the application of underwater sedimentation in the preparation of triaxial sand samples, it is necessary to propose an underwater sedimentation sample preparation device. Utility Model Content

[0008] The purpose of this invention is to provide a triaxial sample preparation device and method based on underwater deposition, so as to solve the problem that underwater deposition is difficult to apply to triaxial sample preparation in the prior art.

[0009] To achieve the above objectives, this utility model provides the following technical solution: a triaxial sample preparation device based on underwater deposition method, mainly comprising a saturator, a support, a water-filled base, a vacuum pump, and a three-valve mechanism;

[0010] The saturator is a container for vacuum saturating sand, mainly comprising a saturator cup body, a saturator top cover, a first valve, and a second valve. The saturator top cover is placed on top of the saturator cup body, and has a pipe and a first valve to control its on / off state. The pipe of the saturator top cover is connected to a vacuum pump via a pressure-resistant pipe. The upper part of the saturator cup body is an open hollow cylinder, and the lower part is a hollow cone. A pipe and a second valve are installed at the bottom of the cone to control its on / off state.

[0011] The three-valve membrane mechanism is a triaxial sample preparation mold. The water-filled base is installed on top of the three-valve membrane mechanism to increase the maximum water level within the three-valve membrane structure. The saturator is fixed above the three-valve membrane mechanism and the water-filled base by the bracket. A pipe at the bottom of the saturator cup is connected to a rubber tube, which extends into the water-filled base and the three-valve membrane mechanism.

[0012] Furthermore, a rubber strip is fixed to the upper edge of the saturator cup, and the upper part of the rubber strip is concave crescent-shaped. The top cover of the saturator is placed above the rubber strip, and the rubber strip is used to seal the gap between the saturator cup and the top cover of the saturator during the vacuuming process.

[0013] Furthermore, the saturator cup body needs to be pressure resistant and should preferably be made of stainless steel or aluminum alloy. The top cover of the saturator should preferably be made of transparent tempered glass to observe the gas release from the sand and water mixture inside the saturator.

[0014] Furthermore, the support includes a base, a straight rod, a C-clamp, a small iron ring, and a large iron ring. The straight rod is fixed to the base. One end of the small iron ring is fixed to the straight rod, and the other end is an O-shaped iron ring with an inner diameter smaller than the maximum outer diameter of the saturator, used to support the saturator. The large iron ring is located above the small iron ring, with one end fixed to the straight rod and the other end being an O-shaped iron ring with an inner diameter approximately equal to the maximum outer diameter of the saturator, used to constrain its horizontal degree of freedom. One end of the C-clamp is fixed to the straight rod, and the other end is clamped to other fixed objects to increase the stability of the support.

[0015] Furthermore, the water-holding base includes a side wall, a base, a first graduation, and a third valve. The side wall is a thin-walled cylinder made of transparent material, with an overflow prevention hole along its upper edge and a first graduation for observing the underwater sedimentation height of sand and soil on its side. The base is fixed to the bottom of the side wall, and the base has a circular opening at its center that extends downwards to form a thin-walled cylindrical latch. The diameter of the circular opening is approximately equal to the outer diameter of the transparent three-lobed membrane, allowing it to be secured to the membrane, thus facilitating the fixation of the water-holding base to the membrane mechanism. The base has a drainage pipe and a third valve to control the flow of the pipe.

[0016] Furthermore, the three-valve mechanism is a structure commonly used in triaxial testing, including a transparent three-valve membrane and a ring. The transparent three-valve membrane is made of transparent material, and its outer wall is provided with a second scale for observing the underwater sedimentation height of sand. The three-valve mechanism is mounted on a triaxial base.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] This device is equipped with a saturator and a vacuum pump, allowing for the direct preparation of underwater saturated sand samples within the saturator via vacuum extraction. Compared to open flame heating for degassing, this method eliminates the need for an open flame, offering better safety and suitability for laboratory operation. Furthermore, this device simplifies the preparation of triaxial samples using underwater sedimentation, eliminating steps such as sample heating, injection of degassed water, overnight cooling, and transfer of the sand solution between the flask and funnel. This significantly reduces sample preparation time, lowers the operational threshold, and improves experimental reliability.

[0019] Furthermore, in the underwater sedimentation method for preparing triaxial samples, the density of the prepared samples is controlled by the underwater sedimentation height of the sand (the sedimentation height directly affects the mass of sand submerged in the three-valve membrane (m2-m1)). This device is equipped with a water-filled base, which increases the maximum water level within the three-valve membrane, thereby expanding the range of possible sample density. Both the water-filled base and the three-valve membrane mechanism are made of transparent material and have graduations, facilitating observation and control of the sand sedimentation height during sample loading, thus improving the uniformity of sample density and the reliability of the experiment. Attached Figure Description

[0020] Figure 1 This is a three-dimensional side view of the sample preparation device of this utility model;

[0021] Figure 2 This is a front view of the sample preparation device of this utility model;

[0022] Figure 3 This is a top view of the saturator structure of this utility model;

[0023] Figure 4 This is a three-dimensional front view of the saturator structure of this utility model;

[0024] Figure 5 This is a cross-sectional view of the saturator AA of this utility model;

[0025] Figure 6 This is a front view of the water-holding base of this utility model.

[0026] Figure 7 This is a three-dimensional top view of the water-holding base of this utility model;

[0027] Figure 8 This is a three-dimensional bottom view of the water-holding base of this utility model;

[0028] Figure 9 This is a front view of the water-holding base and the three-valve membrane connection structure of this utility model;

[0029] Figure 10 This is a cross-sectional structural diagram of the sample preparation device of this utility model;

[0030] In the diagram: 1. Saturator; 101. Saturator cup; 102. Saturator top cover; 103. Rubber strip; 104. First valve; 105. Second valve; 2. Support; 201. Base; 202. Straight rod; 203. C-clamp; 204. Small iron ring; 205. Large iron ring; 3. Water-filled base; 301. Side wall of water-filled base; 302. Overflow hole; 303. Base of water-filled base; 304. Third valve; 305. First graduation; 401. Pressure-resistant pipe; 402. Rubber tube; 5. Vacuum pump; 6. Three-valve mechanism; 601. Transparent three-valve diaphragm; 602. Ring; 603. Second graduation; 7. Three-axis base. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0032] Please see Figure 1-10 This utility model provides a technical solution: a triaxial sample preparation device based on underwater deposition method, mainly including a saturator 1, a support 2, a water-filled base 3, a vacuum pump 5 and a three-valve mechanism 6;

[0033] The saturator 1 is a container for vacuum saturating sand, mainly comprising a saturator cup body 101, a saturator top cover 102, a first valve 104, and a second valve 105. The saturator top cover 102 is placed on top of the saturator cup body 101. A pipe is located at the center of the saturator top cover 102, and the first valve 104 is installed to control its opening and closing. The pipe of the saturator top cover 102 is connected to a vacuum pump 5 via a pressure-resistant pipe 402. The vacuum pump 5 is used to vacuum saturate the underwater sand sample inside the saturator 1. The upper part of the saturator cup body 101 is an open hollow cylinder, and the lower part is a hollow cone. A pipe is located below the cone, and the second valve 105 is installed to control its opening and closing.

[0034] The saturator is fixed above the three-valve membrane mechanism 6 and the water-holding base 3 by the bracket 2. A rubber tube 401 is connected to the bottom of the saturator cup 101, extending into the water-holding base 3 and the three-valve membrane mechanism 6. The water-holding base 3 is installed on top of the three-valve membrane mechanism 6 to increase the maximum water level within the three-valve membrane structure 6.

[0035] A rubber strip 103 is fixed to the upper edge of the saturator cup 101, and the upper part of the rubber strip 103 is concave crescent-shaped. The saturator top cover 102 is placed above the rubber strip 103, and the rubber strip 103 is used to seal the gap between the saturator cup 101 and the saturator top cover 102 during the vacuuming process.

[0036] The saturator cup 101 has a pressure resistance requirement and is preferably made of stainless steel or aluminum alloy. The top cover 102 of the saturator is preferably made of transparent tempered glass to observe the gas release of the sand and water mixture inside the saturator 1.

[0037] The support 2 includes a base 201, a straight rod 202, a C-shaped clamp 203, a small iron ring 204, and a large iron ring 205. The straight rod 202 is fixed to the base 201. One end of the small iron ring 204 is fixed to the straight rod 202 by a clamp, and the other end is an O-shaped iron ring with an inner diameter smaller than the maximum outer diameter of the saturator 1, used to support the saturator 1. The large iron ring 205 is located above the small iron ring 204, with one end fixed to the straight rod 202 by a clamp, and the other end is an O-shaped iron ring with an inner diameter approximately equal to the maximum outer diameter of the saturator 1, used to constrain its horizontal degree of freedom. One end of the C-shaped clamp 203 is fixed to the straight rod 202 by a clamp, and the other end is clamped to another fixed object to increase the stability of the support 2.

[0038] The water-holding base 3 includes a water-holding base sidewall 301, a water-holding base base 303, a first scale 305, and a third valve 304. The water-holding base is used to raise the maximum water level within the three-valve mechanism, thereby increasing the controllable height range of underwater sand deposition. The water-holding base sidewall 301 is a thin-walled cylinder made of transparent material, with an overflow hole 302 along its upper edge, allowing overflowing water to flow out during sand deposition. The side of the water-holding base sidewall 301 has a first scale 305 for observing the underwater sand deposition height. The bottom of the water-holding base sidewall 301 is fixed to the water-holding base base 303, which has a circular opening at its center that extends downwards to form a thin-walled cylindrical latch. The diameter of the circular opening is approximately equal to the outer diameter of the transparent three-valve membrane 601, allowing it to be secured to the transparent three-valve membrane, facilitating the fixation of the water-holding base 3 to the three-valve mechanism 6. Meanwhile, during the preparation of the triaxial sample, the top of the transparent three-valve membrane 601 is provided with an outward-turned sheepskin membrane, which can ensure the sealing of the connection between the water-filled base 3 and the three-valve membrane mechanism 6. The water-filled base 303 is provided with a drainage pipe and equipped with a third valve 304 to control the opening and closing of the pipe.

[0039] The three-lobe mechanism 6 is a structure commonly used in triaxial testing, including a transparent three-lobe 601, a ring 602, and a second scale 603. Its main feature is that the transparent three-lobe 601 is made of transparent material, and the outer wall is provided with a second scale 603 for observing the underwater sedimentation height of sand and soil.

[0040] This embodiment also provides a method for preparing samples using this device, the specific steps of which are as follows:

[0041] Step 1: Install the three-valve mechanism 6

[0042] The installation of the three-valve membrane mechanism 6 is consistent with the conventional process for preparing triaxial sand samples. It mainly includes installing the sheepskin membrane on the triaxial base 7 and fixing it with an "O" ring. Then, permeable stones and filter paper are placed on the triaxial base in sequence. The transparent three-valve membrane 601 is then installed on the triaxial base 7 and fixed with a hose clamp 602. The part of the sheepskin membrane that extends beyond the transparent three-valve membrane 601 is turned outwards onto the upper part of the outer wall of the transparent three-valve membrane 602.

[0043] Step 2: Install water-filled base 3

[0044] The water-holding base 3 is installed on the three-valve membrane mechanism 6. Since the diameter of the circular opening of the water-holding base 303 is approximately the same as the outer diameter of the transparent three-valve membrane 601, the sheepskin membrane, which folds outward onto the upper part of the outer wall of the transparent three-valve membrane 601, fills the space between the circular opening at the bottom of the water-holding base 3 and the transparent three-valve membrane 601, thus forming a watertight seal. The outward folding height of the sheepskin membrane is approximately 1 cm, minimizing obstruction of the markings on the three-valve membrane.

[0045] Step 3: Install saturator 1

[0046] Fix the bracket 2 to the test bench, install the rubber tube 401 at the bottom of the saturator 1, and then fix the saturator 1 inside the small iron ring 204 and the large iron ring 205 of the bracket 2. Adjust the position of the saturator 1 so that the axis of the saturator 1 is aligned with the axis of the transparent three-lobe membrane 6.

[0047] Step 4: Prepare saturated sand

[0048] Close the second valve 105 of the saturator, weigh out a mass of sand m1 and put it into the saturator 1, then inject distilled water until it completely submerges the sand to a certain height, then install the top cover 102 of the saturator, connect the top cover 102 of the saturator and the vacuum pump 5 through the pressure-resistant pipe 402, and open the first valve 104 and the vacuum pump 5 in sequence to maintain a vacuum negative pressure state in the saturator 1 for at least 2 hours to ensure that the underwater sand reaches saturation.

[0049] Step 5: Underwater deposition preparation of triaxial samples

[0050] Turn off vacuum pump 5 and remove pressure-resistant pipe 402. Slowly open first valve 104 to restore the pressure inside saturator 1 to atmospheric pressure. Then, inject degaussed water into the three-valve mechanism 6 and water-filled base 3. Observe the first scale 305 and the second scale 603. Slowly open second valve 105 to allow the sand to fall slowly. By controlling the up and down movement of the saturator, control the distance between the bottom of rubber tube 401 and the sand deposition surface, ensuring that the distance between the bottom of rubber tube 401 and the sand deposition surface remains constant during the deposition process, thereby ensuring the uniform density of the sand sample. When the sample inside the transparent three-valve diaphragm 601 reaches the specified height, close second valve 105.

[0051] Step Six: Remove saturator 1 and water-filled base 3

[0052] Carefully remove saturator 1, taking care to prevent sand and liquid from spilling out. Slowly open the third valve 304 of the water-containing base 3 to drain the solution from the water-containing base 3. After draining, remove the water-containing base 3.

[0053] Step 7: Install the top cap and remove the three-valve mechanism 6

[0054] The installation of the top cap and removal of the three-valve membrane mechanism 6 are consistent with the conventional triaxial sample preparation process for sand, mainly including: installing filter paper, permeable stone and triaxial top cap in sequence on the top of the sample, turning the sheepskin membrane that is turned outward on the upper part of the transparent three-valve membrane 601 onto the triaxial top cap and fixing it with an "O" ring, and finally removing the hose clamp and transparent three-valve membrane in sequence to complete the sample preparation.

[0055] Step 8: Calculate the sample density

[0056] The remaining sand in saturator 1 is dried and weighed, with the mass recorded as m2. The dry density ρ of the sample is then calculated. d The porosity e is calculated using the following formulas:

[0057] (1)

[0058] (2)

[0059] In the formula, V is the total volume of the sample, and G s ρ is the specific gravity of soil particles, m1 is the total mass of sand, and ρ is the total mass of sand. w This is the density of water.

Claims

1. A triaxial specimen preparation apparatus based on an underwater deposition method, characterized by, It includes a saturator (1), a support (2), a water-filled base (3), a vacuum pump (5), and a three-valve mechanism (6); The saturator (1) is a container for vacuum saturating underwater sand, including a saturator cup body (101), a saturator top cover (102), a first valve (104), and a second valve (105); the saturator top cover (102) is placed on the saturator cup body (101), the saturator top cover (102) is provided with a pipe and is equipped with a first valve (104) to control the on / off state, and the pipe of the saturator top cover (102) is connected to the vacuum pump (5) through a pressure-resistant pipe (402); the upper part of the saturator cup body (101) is an open hollow cylinder, and the lower part is a hollow cone. The bottom of the cone is provided with a pipe and is equipped with a second valve (105) to control the on / off state; The three-valve membrane mechanism (6) is a mold for triaxial sample preparation. The water-filled base (3) is installed on the top of the three-valve membrane mechanism (6) to increase the maximum height of the water level inside the three-valve membrane mechanism (6). The saturator is fixed above the water-filled base (3) by the bracket (2). The pipe at the bottom of the saturator cup (101) is connected to the rubber tube (401). The rubber tube (401) extends into the water-filled base (3) and the three-valve membrane mechanism (6).

2. A triaxial specimen preparation apparatus based on underwater deposition method according to claim 1, characterized in that: A rubber strip (103) is fixed to the upper edge of the saturator cup (101). The upper part of the rubber strip (103) is concave crescent-shaped. The saturator top cover (102) is placed above the rubber strip (103). The rubber strip (103) is used to seal the gap between the saturator cup (101) and the saturator top cover (102) during the vacuuming process.

3. A triaxial specimen preparation apparatus based on underwater deposition method as claimed in claim 1, wherein: The saturator cup (101) is made of stainless steel or aluminum alloy, and the saturator top cover (102) is made of transparent tempered glass to observe the gas release of the sand and water mixture inside the saturator (1).

4. The triaxial specimen preparation apparatus based on underwater deposition method according to claim 1, wherein: The bracket (2) includes a base (201), a straight rod (202), a C-shaped clamp (203), a small iron ring (204), and a large iron ring (205). The straight rod (202) is fixed on the base (201). One end of the small iron ring (204) is fixed to the straight rod (202), and the other end is an O-shaped iron ring with an inner diameter smaller than the maximum outer diameter of the saturator (1) to support the saturator (1). The large iron ring (205) is located above the small iron ring, with one end fixed to the straight rod (202) and the other end being an O-shaped iron ring with an inner diameter equal to the maximum outer diameter of the saturator (1) to constrain its horizontal degree of freedom. One end of the C-shaped clamp (203) is fixed to the straight rod (202), and the other end is clamped to other fixed objects to increase the stability of the bracket (2).

5. The triaxial specimen preparation apparatus based on underwater deposition method as claimed in claim 1, wherein: The water-holding base (3) includes a water-holding base sidewall (301), a water-holding base base (303), a first scale (305), and a third valve (304). The water-holding base sidewall (301) is a thin-walled cylinder made of transparent material. An overflow hole (302) is provided on the upper edge, and a first scale (305) for observing the underwater sedimentation height of sand and soil is provided on the side. The bottom of the water-holding base sidewall (301) is fixed with the water-holding base base (303). The center of the base has a circular opening that extends downward to form a thin-walled cylindrical latch. The diameter of the circular opening is equivalent to the outer diameter of the transparent three-lobe membrane (601) and can be latched onto the transparent three-lobe membrane, so that the water-holding base (3) is fixed on the three-lobe membrane mechanism (6). The water-holding base base (303) is provided with a drainage pipe and is equipped with a third valve (304) to control the opening and closing of the pipe.

6. The triaxial specimen preparation apparatus based on underwater deposition method according to claim 1, wherein: The three-lobe mechanism (6) includes a transparent three-lobe (601) and a ring (602). The transparent three-lobe (601) is made of transparent material and has a second scale (603) on its outer wall for observing the underwater sedimentation height of sand. When in use, the three-lobe mechanism (6) is set on a three-axis base (7).

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