A sample preparation device and method for a saturated sand sample

Abstract

The application provides a kind of saturated sand sample preparation device, comprising: box is provided with sealed box door, power module, constant temperature control module, oxygen detection module and vacuum pumping module;Support is fixed to the internal structure of box is in the shape of door character;Stirring unit includes motor, stirrer, hopper, the hopper is funnel-shaped, installed in the upper part of support, hopper bottom is provided with loading solenoid valve;Sample preparation unit includes sample preparation mold, mold clamp, support seat, the sample preparation mold is in the shape of cylinder, vertically placed on support seat, is located in the lower part of support as a whole;Air inlet unit includes upper air inlet pipe and lower air inlet pipe which are connected with external ethanol gas source;Water inlet unit includes water inlet pipe and water inlet solenoid valve installed on water inlet pipe.The device is simple in structure, convenient to use, can prepare sand sample with ultra-high saturation, and ensures the accuracy of subsequent test results.

Description

Technical Field

[0001] This invention provides a sample preparation device and corresponding sample preparation method for saturated sand samples, belonging to the field of civil engineering testing technology. Background Technology

[0002] Sand liquefaction refers to the process where, under the influence of external or internal forces (usually pore water pressure), sand particles lose their interparticle contact pressure and friction, becoming unable to resist shear stress, and thus liquefaction occurs. After sand liquefaction, pore water moves upwards under excess pore water pressure. If there is no less permeable overburden layer above the sand layer, groundwater will overflow to the surface over a large area. If there is a less permeable cohesive soil layer above the sand layer, when the excess pore water pressure exceeds the strength of the overburden layer, groundwater will carry sand particles and break through the overburden layer or gush to the surface along cracks in the overburden layer, resulting in water gushing and sand eruption.

[0003] To study the kinetic characteristics of sand liquefaction, a large number of saturated sand samples need to be prepared. Existing studies have shown that saturation has a significant impact on liquefaction, and improving the saturation of sand models is crucial for sand liquefaction analysis. Currently, there are two main methods for preparing saturated sand model samples: (1) The water drop sand method, which involves first adding saturated liquid to the model box to a predetermined height, and then uniformly sprinkling sand so that the sand can naturally settle under its own weight to prepare a saturated sand model; the main drawbacks of this method are twofold: first, when saturating a model containing fine-particle sand, since the deposition rate of soil particles in the liquid is proportional to the square of the particle size, severe segregation will lead to uneven sample distribution; second, in general centrifuge model tests, to overcome the contradiction between dynamic time and infiltration time, a liquid with higher viscosity is often used instead of water for saturation. This liquid is difficult to penetrate into the micropores of sand particles due to its high viscosity, so the saturation effect is poor; (2) The air sand rain method, which involves first preparing a dry sand model by sprinkling sand, and then suspending the model box into a saturation device for vacuum saturation; the advantage of this method is that the saturation of the model is greatly improved by vacuuming. However, there are two main drawbacks: (1) After the dry sand model is prepared, it needs to be transported to the saturation device through a transfer device, which will disturb the model. This uncontrollable disturbance will affect the control variables of the experiment. For example, the general sand test needs to strictly control the same relative density, which will affect the accuracy of the test results. (2) The sand model is only vacuumed, but air will still remain in the sand pores, which will affect the saturation of the model and thus lead to large errors or even errors in the test results. If carbon dioxide is used as an auxiliary saturation gas, although carbon dioxide can dissolve in water quickly and reduce the saturation time of the sample, the country also has high requirements for the storage and management of carbon dioxide cylinders, which will undoubtedly increase the management difficulty of the laboratory. Summary of the Invention

[0004] This invention provides a sample preparation device for saturated sand samples, which overcomes the shortcomings of the prior art. The device has a simple structure and is easy to use. It can prepare sand samples with ultra-high saturation, ensuring the accuracy of subsequent test results.

[0005] The technical solution adopted to achieve the above-mentioned objective of this invention is as follows:

[0006] A sample preparation apparatus for saturated sand samples, comprising at least a sample preparation mold, the sample preparation apparatus including:

[0007] The enclosure is equipped with a sealed door, a power module, a constant temperature control module, an oxygen detection module, and a vacuum module. The sealed door has a transparent observation window.

[0008] The bracket is fixed inside the box, and the overall structure is U-shaped.

[0009] The mixing unit includes a motor, a stirrer, and a hopper. The hopper is funnel-shaped and installed on the upper part of the support. A solenoid valve for loading is provided at the bottom of the hopper. The motor is installed on the top of the support. The output shaft of the motor is connected to the stirrer and drives the stirrer to rotate. The stirrer is installed inside the hopper.

[0010] The sample preparation unit includes a sample preparation mold, a mold clamp, and a support base. The sample preparation mold is cylindrical and placed vertically on the support base, located at the lower part of the support frame. The mold clamp is installed on both sides of the sample preparation mold and is used to clamp and fix the sample preparation mold. The top of the sample preparation mold is an open opening located directly below the hopper. The bottom of the sample preparation mold is closed and has an interface, which is sealed with a mesh screen. The support base is fixed to the bottom of the support frame and has a slot that is sealed to the interface. A T-shaped pipe is connected to the bottom of the slot.

[0011] The air intake unit includes an upper air intake pipe and a lower air intake pipe. Both the upper and lower air intake pipes are connected to an external ethanol gas source. The upper air intake pipe is connected to the top of the loading solenoid valve at the bottom of the hopper, and the lower air intake pipe is connected to the three-way pipe below the support base. Both the upper and lower air intake pipes are equipped with air intake solenoid valves.

[0012] The water inlet unit includes a water inlet pipe and a water inlet solenoid valve installed on the water inlet pipe. One end of the water inlet pipe is connected to an external pure water source, and the other end of the water inlet pipe is connected to a T-shaped pipe under the support base.

[0013] The volume of the hopper is matched with the volume of the sample preparation mold.

[0014] The side wall of the housing is equipped with an upper air intake button and a lower air intake button. The upper air intake button and the lower air intake button are respectively connected to the air intake solenoid valves on the upper air intake pipe and the lower air intake pipe and control the opening and closing of the air intake solenoid valves.

[0015] A water inlet button is provided on the side wall of the box. The water inlet button is connected to the water inlet solenoid valve on the water inlet pipe and controls the opening and closing of the water inlet solenoid valve.

[0016] A loading button is provided on the side wall of the box. The loading button is connected to the loading solenoid valve at the bottom of the hopper and controls the opening and closing of the loading solenoid valve.

[0017] A stirring button is provided on the side wall of the box. The stirring button is connected to the motor and controls the motor's on / off state.

[0018] The present invention also provides a method for preparing saturated sand samples based on the above-mentioned sample preparation device, comprising the following steps:

[0019] (1) Weigh the dry sand particles, then put the sand particles into the hopper, place the sample preparation mold on the support base and fix it with the mold clamp, close the box door and turn on the power.

[0020] (2) Start the motor to stir, and at the same time turn on the constant temperature control module to heat the inside of the box. Set the temperature to 80-90℃, and start the vacuum module to vacuum the inside of the box.

[0021] (3) After the temperature and vacuum level inside the chamber reach the set requirements, start the air intake solenoid valve to pass ethanol gas into the chamber. The oxygen detection module monitors the oxygen content inside the chamber in real time until the oxygen content inside the chamber is lower than the set value. Then, close the air intake solenoid valve and the vacuum module to stop the ethanol gas from being introduced.

[0022] (4) Open the loading solenoid valve. The sand particles in the hopper gradually fall into the sample mold under the stirring of the agitator. After all the sand particles have entered the sample mold, close the loading solenoid valve and the motor agitator.

[0023] (5) Open the water inlet solenoid valve and introduce pure water from the bottom interface of the sample preparation mold. When you observe through the transparent observation window at the box door that the pure water has filled to the top of the sample preparation mold, close the water inlet solenoid valve.

[0024] (6) Turn off the constant temperature control module and open the air inlet valve on the sealed door. After the temperature and air pressure inside the chamber return to normal, open the door and loosen the mold clamp to take out the sample preparation mold.

[0025] Compared with existing technologies, the saturated sand sample preparation device provided in this invention has the following advantages: 1. Since the sand particles are loaded from the outside, the air in the gaps between the sand particles is the most difficult to expel. To solve this problem, this patent adopts a stirring + bottom ventilation method. Specifically, on the one hand, the sand particles in the hopper are continuously stirred and stirred using a motor and a stirrer; on the other hand, high-temperature ethanol gas is introduced from the bottom of the hopper upwards. By combining these two methods, the residual air between the sand particles can be completely expelled. 2. This device innovatively uses high-temperature ethanol gas as an auxiliary saturating gas. Since high-temperature ethanol gas is miscible with water and is easily liquefied, it can ensure ultra-high saturation in the sand sample and avoid residual air in the sand sample. 3. Although high-temperature ethanol gas can ensure ultra-high saturation of sand samples, due to the flammability and explosiveness of high-temperature ethanol gas, for safety reasons, this device is equipped with a vacuum module in the chamber. After the air in the chamber is extracted by the vacuum module, high-temperature ethanol gas is introduced to completely expel the remaining air in the chamber until the air content in the chamber reaches an extremely low value to avoid accidents. Attached Figure Description

[0026] Figure 1 A schematic diagram of the overall structure of the sample preparation device for saturated sand samples provided by the present invention.

[0027] Figure 2 A schematic diagram of the connection structure between the support base and the sample preparation mold;

[0028] In the diagram: 1-box body, 2-support, 3-motor, 4-stirrer, 5-hopper, 6-feeding solenoid valve, 7-sample mold, 8-mold clamp, 9-support base, 10-interface, 11-mesh, 12-slot, 13-tee pipe, 14-upper air inlet pipe, 15-lower air inlet pipe, 16-air inlet solenoid valve, 17-water inlet pipe, 18-water inlet solenoid valve. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the scope of protection of the present invention is not limited to the following embodiments.

[0030] The sample preparation device for saturated sand provided in this embodiment has the following overall structure: Figure 1 As shown, it includes:

[0031] The enclosure 1 is equipped with a sealed door, a power module, a temperature control module, an oxygen detection module, and a vacuum module. The sealed door has a transparent observation window. Figure 1(The middle cabinet door is not shown); In this embodiment, the cabinet can be made of conventional metal or organic plastic. The power supply module, temperature control module, oxygen detection module, and vacuum module used are all commercially available conventional modules, and the technology used is currently very mature. Therefore, this patent does not need to describe the above modules in detail.

[0032] The bracket 2 is fixed inside the enclosure, and its overall structure is U-shaped. The bottom of the bracket is fixed to the enclosure with bolts, and the bracket as a whole is used to support the various modular units inside the enclosure.

[0033] The mixing unit includes a motor 3, a stirrer 4, and a hopper 5. The hopper is funnel-shaped and installed on the upper part of the support frame. A solenoid valve 6 for loading is installed at the bottom of the hopper. The motor is installed on the top of the support frame, and its output shaft is connected to the stirrer to drive the stirrer to rotate. The stirrer is installed inside the hopper. A stirring button is installed on the side wall of the housing, which is connected to the motor and controls the motor's on / off state. The volume of the hopper matches the volume of the sample preparation mold. A loading button is also installed on the side wall of the housing, which is connected to the solenoid valve at the bottom of the hopper and controls the opening and closing of the solenoid valve.

[0034] The sample preparation unit includes a sample preparation mold 7, a mold clamp 8, and a support base 9. The sample preparation mold is cylindrical in shape and is placed vertically on the support base, located at the lower part of the bracket. The mold clamp is installed on both sides of the sample preparation mold and is used to clamp and fix the sample preparation mold. The top of the sample preparation mold is an open opening located directly below the hopper, and the bottom of the sample preparation mold is closed, with an interface 10 provided at the bottom. Figure 2 As shown, a mesh screen 11 is provided to seal the interface; the support base is fixed to the bottom of the bracket, and a slot 12 is provided on the support base to seal the interface. A three-way pipe 13 is connected to the bottom of the slot.

[0035] The air intake unit includes an upper air intake pipe 14 and a lower air intake pipe 15. Both the upper and lower air intake pipes are connected to an external ethanol gas source. The upper air intake pipe is connected to the top of the loading solenoid valve at the bottom of the hopper, and the lower air intake pipe is connected to the three-way pipe below the support base. Both the upper and lower air intake pipes are equipped with air intake solenoid valves 16. The side wall of the housing is equipped with an upper air intake button and a lower air intake button. The upper air intake button and the lower air intake button are respectively connected to the air intake solenoid valves on the upper and lower air intake pipes and control the opening and closing of the air intake solenoid valves.

[0036] The water inlet unit includes an inlet pipe 17 and an inlet solenoid valve 18 installed on the inlet pipe. One end of the inlet pipe is connected to an external pure water source, and the other end is connected to a T-shaped pipe below the support base. A water inlet button is provided on the side wall of the housing. The water inlet button is connected to the inlet solenoid valve on the inlet pipe and controls the opening and closing of the inlet solenoid valve.

[0037] The present invention also provides a method for preparing saturated sand samples based on the above-mentioned sample preparation device, comprising the following steps:

[0038] (1) Weigh the dry sand particles, then put the sand particles into the hopper, place the sample preparation mold on the support base and fix it with the mold clamp, close the box door and turn on the power.

[0039] (2) Start the motor to stir, and at the same time turn on the constant temperature control module to heat the inside of the box. Set the temperature to 80-90℃, and start the vacuum module to vacuum the inside of the box.

[0040] (3) After the temperature and vacuum level inside the chamber reach the set requirements, start the air intake solenoid valve to pass ethanol gas into the chamber. The oxygen detection module monitors the oxygen content inside the chamber in real time until the oxygen content inside the chamber is lower than the set value. Then, close the air intake solenoid valve and the vacuum module to stop the ethanol gas from being introduced.

[0041] (4) Open the loading solenoid valve. The sand particles in the hopper gradually fall into the sample mold under the stirring of the agitator. After all the sand particles have entered the sample mold, close the loading solenoid valve and the motor agitator.

[0042] (5) Open the water inlet solenoid valve and introduce pure water from the bottom interface of the sample preparation mold. When you observe through the transparent observation window at the box door that the pure water has filled to the top of the sample preparation mold, close the water inlet solenoid valve.

[0043] (6) Turn off the constant temperature control module and open the air inlet valve on the sealed door. After the temperature and air pressure inside the chamber return to normal, open the door and loosen the mold clamp to take out the sample preparation mold.

Claims

1. A method for preparing saturated sand samples based on a sample preparation device, the sample preparation device comprising: The enclosure is equipped with a sealed door, a power module, a constant temperature control module, an oxygen detection module, and a vacuum module. The sealed door has a transparent observation window. The bracket is fixed inside the box, and the overall structure is U-shaped. The mixing unit includes a motor, a stirrer, and a hopper. The hopper is funnel-shaped and installed on the upper part of the support. A solenoid valve for loading is provided at the bottom of the hopper. The motor is installed on the top of the support. The output shaft of the motor is connected to the stirrer and drives the stirrer to rotate. The stirrer is installed inside the hopper. The sample preparation unit includes a sample preparation mold, a mold clamp, and a support base. The sample preparation mold is cylindrical and placed vertically on the support base, located at the lower part of the support frame. The mold clamp is installed on both sides of the sample preparation mold and is used to clamp and fix the sample preparation mold. The top of the sample preparation mold is an open opening located directly below the hopper. The bottom of the sample preparation mold is closed and has an interface, which is sealed with a mesh screen. The support base is fixed to the bottom of the support frame and has a slot that is sealed to the interface. A T-shaped pipe is connected below the slot. The air intake unit includes an upper air intake pipe and a lower air intake pipe. Both the upper and lower air intake pipes are connected to an external ethanol gas source. The upper air intake pipe is connected to the top of the loading solenoid valve at the bottom of the hopper, and the lower air intake pipe is connected to the three-way pipe below the support base. Both the upper and lower air intake pipes are equipped with air intake solenoid valves. The water inlet unit includes a water inlet pipe and a water inlet solenoid valve installed on the water inlet pipe. One end of the water inlet pipe is connected to an external pure water source, and the other end of the water inlet pipe is connected to a three-way pipe under the support base. The method for preparing the saturated sand sample is characterized by the following steps: (1) Weigh the dry sand particles, then put the sand particles into the hopper, place the sample preparation mold on the support base and fix it with the mold clamp, close the box door and turn on the power; (2) Start the motor to stir, and at the same time turn on the constant temperature control module to heat the inside of the box. Set the temperature to 80~90℃, and start the vacuum module to vacuum the inside of the box. (3) After the temperature and vacuum inside the chamber reach the set requirements, start the air intake solenoid valve to pass ethanol gas into the chamber. The oxygen detection module monitors the oxygen content inside the chamber in real time until the oxygen content inside the chamber is lower than the set value. Then, close the air intake solenoid valve and the vacuum module to stop the ethanol gas from being introduced. (4) Open the loading solenoid valve. The sand particles in the hopper gradually fall into the sample mold under the stirring of the agitator. After all the sand particles have entered the sample mold, close the loading solenoid valve and the motor agitator. (5) Open the water inlet solenoid valve and introduce pure water from the bottom interface of the sample preparation mold. When you observe through the transparent observation window at the box door that the pure water has filled to the top of the sample preparation mold, close the water inlet solenoid valve. (6) Turn off the constant temperature control module and open the air inlet valve on the sealed door. After the temperature and air pressure inside the chamber return to normal, open the door and loosen the mold clamp to take out the sample preparation mold.

2. The method for preparing saturated sand samples according to claim 1, characterized in that: The volume of the hopper is matched with the volume of the sample preparation mold.

3. The method for preparing saturated sand samples according to claim 1, characterized in that: The side wall of the housing is equipped with an upper air intake button and a lower air intake button. The upper air intake button and the lower air intake button are respectively connected to the air intake solenoid valves on the upper air intake pipe and the lower air intake pipe and control the opening and closing of the air intake solenoid valves.

4. The method for preparing a saturated sand sample according to claim 1, characterized in that: A water inlet button is provided on the side wall of the box. The water inlet button is connected to the water inlet solenoid valve on the water inlet pipe and controls the opening and closing of the water inlet solenoid valve.

5. The method for preparing a saturated sand sample according to claim 1, characterized in that: A loading button is provided on the side wall of the box. The loading button is connected to the loading solenoid valve at the bottom of the hopper and controls the opening and closing of the loading solenoid valve.

6. The method for preparing a saturated sand sample according to claim 1, characterized in that: A stirring button is provided on the side wall of the box, and the stirring button is connected to the motor and controls the motor's on / off state.

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