WO2022206145A1

WO2022206145A1 - Soil testing device

Info

Publication number: WO2022206145A1
Application number: PCT/CN2022/073453
Authority: WO
Inventors: 周恒�; 狄圣杰; 陆希; 王明疆; 刘玮; 张莹; 魏鹏; 胡向阳; 黄鹏; 吕佼佼
Original assignee: 中国电建集团西北勘测设计研究院
Priority date: 2021-03-29
Filing date: 2022-01-24
Publication date: 2022-10-06
Also published as: CN113176391A

Abstract

A soil testing device, comprising: a sample container (10), a stress loading assembly (20), a displacement measuring assembly (30), a suction force control assembly (40), and a water volume measuring assembly (50). An accommodating cavity (170) and a flow channel (180) located at the bottom of the accommodating cavity (170) are formed in the sample container (10), and the accommodating cavity (170) is configured to accommodate a soil sample. The stress loading assembly (20) is provided correspondingly to the sample container (10), and is configured to load preset stress to the soil sample in the sample container (10) in a preset direction. The displacement measuring assembly (30) is provided correspondingly to the sample container (10) and is configured to measure a thickness change, along a preset direction, of the soil sample in the sample container (10). The suction force control assembly (40) is communicated with the flow channel (180) and is configured to apply preset matric suction force to the soil sample in the sample container (10). The water volume measuring assembly (50) is connected to the suction force control assembly (40) and is configured to measure the mass of water in the suction force control assembly (40). The soil testing device can perform high-precision test on the hydraulic characteristics of soil.

Description

Soil testing device

technical field

The present disclosure relates to the technical field of geotechnical engineering measurement, and in particular, to a soil testing device.

Background technique

With the rapid development of my country's economy in recent years, a series of infrastructure constructions such as expressways, high-speed railways, and super high-rise buildings have been carried out on a large scale in China. Most of these infrastructures are built on soil sites with unsaturated soils. Researching the hydraulic properties of unsaturated soils is the key to ensuring their good service performance.

Therefore, there is a need to provide a soil testing device to test the hydraulic properties of unsaturated soil with higher accuracy.

It should be noted that the information disclosed in the above Background section is only for enhancement of understanding of the background of the present disclosure, and therefore may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION

The purpose of the embodiments of the present disclosure is to provide a soil testing device capable of testing the hydraulic properties of soil with high precision.

Other features and advantages of the present disclosure will become apparent from the following detailed description, or be learned in part by practice of the present disclosure.

According to an aspect of the embodiments of the present disclosure, there is provided a soil testing device, the soil testing device comprising:

a sample container, which is formed with an accommodation cavity and a flow channel at the bottom of the accommodation cavity, the flow passage communicates with the accommodation cavity, and the accommodation cavity is configured to accommodate soil samples;

a stress loading component, disposed corresponding to the sample container, and configured to load a preset stress along a preset direction on the soil sample in the sample container;

a displacement measuring component, disposed corresponding to the sample container, configured to measure the thickness change of the soil sample in the sample container along the preset direction;

a suction control assembly, in communication with the flow channel, configured to apply a preset matrix suction to the soil sample in the sample container;

A water measurement assembly, connected to the suction control assembly, is configured to measure the quality of water in the suction control assembly.

In an exemplary embodiment of the present disclosure, the soil testing device further includes:

A bubble flushing assembly, in communication with the flow channel, is configured to flush bubbles in the flow channel.

In an exemplary embodiment of the present disclosure, the bubble flushing assembly includes:

a syringe, communicated with the inlet of the flow channel, for injecting flushing agent into the flow channel;

The exhauster, communicated with the outlet of the flow channel, is used for accommodating the liquid flushed out of the flow channel, and the flushed air bubbles can be discharged through the exhaust hole.

In an exemplary embodiment of the present disclosure, the sample container includes:

bottom plate;

a fixing ring, which is arranged on the bottom plate, and cooperates with the bottom plate to form the accommodating cavity with an open end;

Wherein, the flow channel is formed at the corresponding position of the bottom plate and the accommodating cavity, and the inlet and the outlet of the flow channel are drawn out through the bottom plate.

In an exemplary embodiment of the present disclosure, the sample container further includes:

an air intake layer, arranged on the bottom plate;

The filter layer is arranged on the side of the air inlet layer away from the bottom plate, and the soil sample is arranged between the air inlet layer and the filter layer;

a water-permeable layer, located on the side of the filter layer away from the bottom plate;

The top cover is arranged on the side of the water permeable layer away from the bottom plate.

A bracket assembly, the bracket assembly is arranged on the bottom plate, and the stress loading component is arranged on the bracket assembly.

In an exemplary embodiment of the present disclosure, the stress loading assembly includes:

Drive mechanism;

a positioning rod, connected with the driving end of the driving mechanism, and the driving mechanism can drive the positioning rod to move along the preset direction, so as to measure the soil sample in the sample container along the preset direction Load preset stress.

In an exemplary embodiment of the present disclosure, the displacement measurement assembly includes:

The displacement gauge is arranged on the positioning rod and moves synchronously with the positioning rod to measure the thickness change of the soil sample in the sample container along the preset direction.

In an exemplary embodiment of the present disclosure, the suction control assembly includes:

a sealed container, communicated with the flow channel, and a pressure relief port is provided on the sealed container;

A vacuum machine is connected to the airtight container for adjusting the degree of vacuum in the airtight container.

In an exemplary embodiment of the present disclosure, the water measurement assembly includes:

Weight measuring equipment, the sealed container is arranged on the weight measuring equipment.

In the soil testing device provided by the present disclosure, the suction control component can accurately control the matrix suction of the soil sample in the sample container, and the water quantity measurement component can accurately measure the water volume of the soil sample in the sample container; The suction control component and the water measurement component reduce the water content test error caused by changes in ambient temperature and humidity, and eliminate the influence of the precise control of the soil matrix suction during the closed gas relative test under low suction conditions. The preset loading force applied to the soil sample in the container, through the stress loading group and the suction control component, solves the problem that when the existing pressure plate instrument applies different matrix suction states, the pressure change in the sample container transmits the vertical transmission to the loading rod. The influence of stress; through the displacement measurement component, the thickness change of the soil sample in the sample container can be accurately measured along the preset direction; the soil testing device can carry out the confinement compression consolidation of unsaturated soil under low matrix suction, different stresses The soil-water characteristic curve, increase/dehumidification deformation and other tests under the state improve the practicability of the soil testing device.

It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the disclosure and together with the description serve to explain the principles of the disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort. In the attached image:

1 is a schematic diagram of a soil testing device provided by an embodiment of the present disclosure;

2 is a schematic diagram of a sample container, a stress loading assembly, a displacement measurement assembly, and a bracket assembly provided by an embodiment of the present disclosure;

3 is a schematic diagram of a sample container provided by an embodiment of the present disclosure;

4 is a schematic diagram of a bubble flushing assembly and a sample container according to an embodiment of the present disclosure;

5 is a schematic diagram of a bubble flushing assembly, a suction control assembly, and a water volume measuring assembly provided by an embodiment of the present disclosure;

6 is a schematic diagram of a bottom plate provided by an embodiment of the present disclosure;

FIG. 7 provides soil-water characteristic curves of unsaturated soil under different stress states according to an embodiment of the present disclosure;

FIG. 8 is a collapsible deformation curve of unsaturated soil provided by an embodiment of the present disclosure;

FIG. 9 provides confinement compression curves of unsaturated soil under different matrix suctions according to an embodiment of the present disclosure.

Description of reference numbers:

10. Sample container, 110, bottom plate, 120, clay plate, 130, ring knife sample, 140, permeable stone, 150, top cover, 160, fixing ring, 170, accommodating cavity, 180, flow channel;

20. Stress loading assembly, 210, cylinder, 220, piston, 230, loading rod, 240, positioning rod, 250, second valve port, 260, first valve port;

30. Displacement measuring assembly, 310, Electronic displacement sensor, 320, Sensor contact;

40, suction control assembly, 410, sealed container, 420, vacuum machine, 430, pressure relief port, 440, pressure gauge;

50. Water measurement component, 510, scale, 520, tray;

60. Bubble flushing assembly, 610, syringe, 620, exhauster;

70. Bracket assembly, 710, first support rod, 720, second support rod, 730, sealing ring, 740, positioning plate;

810, the first switch valve, 820, the second switch valve, 830, the third switch valve, 840, the fourth switch valve, 850, the fifth switch valve.

Detailed ways

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments, however, can be embodied in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed descriptions will be omitted.

Although relative terms such as "upper" and "lower" are used in this specification to describe the relative relationship of one component of an icon to another component, these terms are used in this specification only for convenience, such as according to the direction of the example described. It will be appreciated that if the device of the icon is turned upside down, the components described as "on" will become the components on "bottom". When a certain structure is "on" other structures, it may mean that a certain structure is integrally formed on other structures, or that a certain structure is "directly" arranged on other structures, or that a certain structure is "indirectly" arranged on another structure through another structure. other structures.

The terms "a", "an", "the", "said" and "at least one" are used to indicate the presence of one or more elements/components/etc; the terms "include" and "have" are used to indicate an open-ended is meant to be inclusive and means that additional elements/components/etc may be present in addition to the listed elements/components/etc; the terms "first", "second" and "third" etc. only Used as a marker, not a limit on the number of its objects.

Unsaturated soil in soil is a three-phase soil. Unlike saturated soil, unsaturated soil not only has solid phase (soil particles and some cemented substances) and liquid phase (water and aqueous solution), but also gas phase (air and water). water vapor, etc.) are present.

The inventors found that the compression and consolidation characteristics of unsaturated soil reflect the deformation of soil under different load and water content conditions, and are an important parameter in the design of infrastructure foundation settlement control. For example, existing high-rise buildings have been compressed and consolidated due to changes in the load and water content of unsaturated foundation soil, and engineering problems such as excessive cracks and inclinations in the building have occurred from time to time. The moisture-increasing/dehumidifying soil-water characteristic curves of unsaturated soil under different stress states reflect the water-holding capacity of the soil and can be used to analyze the permeability characteristics of the soil at the site. For example, the moisturizing and water-holding characteristics of unsaturated soil are necessary parameters for calculating the spatiotemporal distribution of moisture in highway and railway foundations under rainfall conditions, and provide a basis for subsequent deformation and stability analysis of unsaturated soil foundations. The moisture-increasing/dehumidifying deformation test of unsaturated soil under different stress states reflects the collapsibility or expansion deformation characteristics of soil. For example, the first step in infrastructure construction in loess or expansive soil areas in my country is to accurately assess the collapsibility or expansiveness of the unsaturated soils on the site. However, the existing soil testing devices cannot accurately study the hydraulic properties of unsaturated soils.

Under the unsaturated state of soil, there is a gas-liquid two-phase medium in the pores, and the connection state of the two-phase medium is different under different matrix suction conditions. Under low matrix suction, due to high water content, the connected state of gas-liquid two-phase in soil pores is liquid-connected but not gas-connected; under medium-matrix suction, due to moderate water content, gas-liquid two-phase in soil pores All are in a connected state; under high matrix suction, due to the low water content, the connected state of the gas-liquid two phases in the soil pores is that the liquid is not connected but the gas is connected.

At present, most of the devices for testing the hydraulic properties of unsaturated soils use axis translation technology to control the matrix suction of the soil. The basic principle is to control the constant pore water pressure of the soil through the high air-intake value clay plate, and then control the matrix suction by changing the pore air pressure. However, this method of controlling matrix suction is only suitable for medium or high matrix suction states—that is, the gas phase in the soil pores is in a connected state. For the low matrix suction state, because the gas phase in the soil pores is in a non-connected state, it is difficult to precisely control the soil matrix suction by changing the pore pressure.

In addition, due to the application of high air pressure in the existing unsaturated soil test device, during the test process, gas in the container will inevitably dissolve in the water and then be discharged, and accumulate in the water tank under the clay plate to form closed air bubbles. The formation of , greatly affects the accuracy of soil water content measurement; further, in the process of applying different matrix suction, the changed air pressure value in the sample container will offset/enhance the vertical stress transmitted by the loading rod. It is necessary to calculate and adjust the corresponding vertical stress loading value, which makes the test operation complicated. In addition, existing unsaturated soil testing devices are expensive, preventing widespread use.

In view of the above technical problems, embodiments of the present disclosure provide a soil testing device, as shown in FIGS. 1-6 , the soil testing device includes: a sample container 10 , a stress loading assembly 20 , a displacement measuring assembly 30 , a suction force Control assembly 40 and water measurement assembly 50 . The sample container 10 is formed with an accommodating cavity 170 and a flow channel 180 at the bottom of the accommodating cavity 170. The flow channel 180 communicates with the accommodating cavity 170, and the accommodating cavity 170 is configured to accommodate a soil sample (for example, an unsaturated soil sample). ); the stress loading component 20 is set corresponding to the sample container 10, and is configured to load the soil sample in the sample container 10 with a preset stress along a preset direction; the displacement measuring component 30 is set corresponding to the sample container 10, and is configured In order to measure the thickness change of the soil sample in the sample container 10 along a preset direction; the suction control assembly 40 is communicated with the flow channel 180 and is configured to apply a preset matrix suction force to the soil sample in the sample container 10; water volume measurement The assembly 50 is connected to the suction control assembly 40 and is configured to measure the quality of the water in the suction control assembly 40 .

The soil testing device provided by the present disclosure can accurately control the matrix suction of the soil sample in the sample container through the suction control component, and can accurately measure the water volume of the soil sample in the sample container through the water quantity measuring component; The water content test error caused by the change of ambient temperature and humidity is reduced by the suction control component and the water measurement component, and the influence of the precise control of the soil matrix suction during the relative test of the closed gas under the low suction state is eliminated. The preset loading force applied to the soil sample in the sample container, through the stress loading group and the suction control component, solves the problem that the existing pressure plate instrument transmits vertical pressure to the loading rod due to the change of air pressure in the sample container when different substrate suction states are applied. Through the displacement measurement component, the thickness change of the soil sample in the sample container can be accurately measured along the preset direction; the soil testing device can carry out the confinement compression consolidation of unsaturated soil under low matrix suction Tests such as soil-water characteristic curve and increase/dehumidification deformation under stress state improve the practicability of the test device.

In addition, the soil testing device provided by the present disclosure has short production cycle, clear testing principle, simple structure, simple operation, convenient installation and testing, low cost, strong practicability, and high market competitiveness.

Specifically, as shown in FIG. 1 and FIG. 4 , the soil testing device further includes: a bubble scouring assembly 60 . The bubble flushing assembly 60 communicates with the flow channel 180 and is configured to flush bubbles in the flow channel 180 . Through the air-bubble flushing assembly 60, it is possible to exclude air bubbles from affecting the accuracy of testing the water content of the soil, thereby improving the testing accuracy of the hydraulic properties of the unsaturated soil.

Specifically, as shown in FIGS. 3 and 6 , the sample container 10 includes: a bottom plate 110 and a fixing ring 160 . The fixing ring 160 is arranged on the bottom plate 110 and cooperates with the bottom plate 110 to form a receiving cavity 170 with an open end.

Wherein, the fixing ring 160 can be connected with the bottom plate 110 by a screw, the bottom plate 110 can be provided with a raised installation part, the fixing ring 160 is arranged on the raised installation part, and the fixing ring 160 is provided with a through hole or a threaded hole matched with the screw rod, The bottom plate is provided with threaded holes, and the screws are inserted into the through holes or threaded holes on the fixing ring 160 and the forehead threaded holes on the bottom plate to fix the fixing ring 160 on the bottom plate 110 . In addition, the fixing ring 160 can also be connected to the bottom plate 110 by welding, bonding, snap-fitting, etc., which is not limited in the present disclosure.

Wherein, a flow channel 180 is formed at a position corresponding to the bottom plate 110 and the accommodating cavity 170 , and the inlet and the outlet of the flow channel 180 are drawn out through the bottom plate 110 . The flow channel can be one continuous one or a plurality of flow channels can be arranged in parallel, and one inlet and one outlet of the flow channel 180 can be arranged respectively, or a plurality of flow channels can be arranged, which is not limited in the present disclosure.

Wherein, as shown in FIGS. 3 and 6 , the flow channel 180 located in the accommodating cavity 170 is formed by being recessed from the bottom plate 110 , that is, the flow channel 180 is exposed in the accommodating cavity 170 like a groove, and is located outside the fixing ring 160 . The flow channel 180 is embedded in the bottom plate 110 .

Wherein, as shown in FIG. 6 , when the flow channel 180 is a continuous one, the flow channels 180 in the accommodating cavity 170 are arranged in a continuous S shape. Of course, the flow channels can also be arranged in a straight line or other curved shapes. ; When there are multiple flow channels, the multiple flow channels can be arranged in a straight line and parallel, or in a curved parallel arrangement, or in an irregular arrangement.

Wherein, the depth and width of the flow channel may be, for example, 1 mm-3 mm, such as 1 mm, 2 mm or 3 mm, which are not listed one by one in the present disclosure. Of course, the depth and width of the flow channel can also be less than 1 mm or 3 mm, and the depth and width of the flow channel can be set according to the actual situation, which is not limited in the present disclosure, and is not limited in the present disclosure.

The inlet and outlet of the flow channel 180 may be drawn out from the side wall of the bottom plate 110 or the surface of the bottom plate 110 . One or more inlets and outlets can be set respectively, and multiple flow channels can share the same outlet or inlet.

Wherein, the flow channel 180 exposed in the accommodating cavity 170 and the flow channel 180 buried in the bottom plate 110 may communicate with each other through a via hole. Both ends of the flow channel 180 exposed in the accommodating cavity 170 may be led out respectively through one or more flow channels 180 embedded in the bottom plate 110 .

Wherein, the flow channel 180 on the bottom plate 110 can be formed by casting, grinding and other processes. The material of the bottom plate 110 can be metal or non-metal, for example, the metal material can be iron, copper, aluminum or its alloy material, and the non-metal material can be, for example, plastic, rubber, etc. The material of the bottom plate 110 can be a hydrophobic material. Personnel can select according to actual needs, which is not limited in the present disclosure.

Wherein, the bottom plate 110 is formed with grooves through depressions at positions corresponding to the accommodation space, and the depths of the grooves are 6mm-10mm, such as 6mm, 7mm, 8mm, 9mm or 10mm, which are not listed one by one in the present disclosure. Of course, the depth of the groove can also be less than 6mm or greater than 10mm, which is not limited in the present disclosure.

Wherein, the diameter of the groove may be 60mm-100mm, such as 60mm, 70mm, 80mm, 90mm or 100mm, which are not listed one by one in the present disclosure. Of course, the diameter of the groove can also be smaller than 60 mm or larger than 100 mm, which is not limited in the present disclosure.

Wherein, the groove may be a side wall, a straight wall, or an inclined wall with an angle, which is not limited in the present disclosure.

Specifically, as shown in FIG. 3 , the sample container 10 further includes: an air inlet layer 120 , a filter layer (not shown in the figure), a water permeable layer 140 and a top cover 150 located in the accommodating cavity 170 . On the bottom plate 110, the filter layer is arranged on the side of the air inlet layer 120 away from the bottom plate 110, the unsaturated soil sample (ring knife sample 130) is arranged between the air inlet layer 120 and the filter paper during the test, and the water permeable layer 140 is arranged on the side of the bottom plate 110. The filter layer is on the side away from the bottom plate 110 , and the top cover 150 is disposed on the side of the water permeable layer 140 away from the bottom plate 110 . The constant pore water pressure of the soil body can be controlled by the air intake layer 120 with high air intake value, and then the suction force of the matrix can be controlled by changing the pore air pressure. The filter layer can filter the moisture of the ring knife sample 130 . The water-permeable layer 140 can accommodate the water flowing out of the ring knife sample 130 through the filter layer.

Wherein, the air intake layer 120 may be a clay plate. Clay board, also known as pottery board, can be made of natural clay as the main raw material, without adding any other ingredients, through high pressure extrusion, low temperature drying and high temperature firing at 1200℃-1250℃.

Wherein, the filter layer can be filter paper. The filter paper can be composed of cotton fibers, and there are countless small holes on the surface for liquid particles to pass through, while larger solid particles cannot pass through, so that the mixed liquid and solid substances can be separated.

Wherein, the permeable layer 140 may be a permeable stone. Permeable stone is a solid form of ecological permeable concrete, which is composed of cement, water, permeable concrete reinforcing agent and high-quality aggregates of the same particle size or discontinuous gradation, and has a certain porosity. Water absorption and drainage performance.

The shape and size of the clay plate match the shape and size of the accommodating space. When the clay plate is placed on the bottom plate 110 in the accommodating space, the gap between the clay plate and the fixing ring 160 is small and is within a preset range. The clay plate is located in the groove, and the gap between it and the side walls around the groove is sealed with glue, such as epoxy glue.

Specifically, as shown in FIG. 4 , the bubble flushing assembly 60 includes: a syringe 610 and an exhauster 620. The injector 610 communicates with the inlet of the flow channel 180 through the pipeline, and the exhauster 620 communicates with the outlet of the flow channel 180 through the pipeline. The syringe 610 flushes the flow channel 180 by filling the liquid for flushing out air bubbles, so that the water with bubbles in the flow channel 180 is flushed into the container of the exhauster 620, and the container of the exhauster 620 is provided with an exhaust gas The flushed gas can be exhausted through the exhaust hole.

As shown in FIG. 1 , FIG. 4 and FIG. 5 , the bubble flushing assembly 60 and the suction control assembly 40 share a pipeline and communicate with the flow channel 180 . The flow channel 180 is provided with a first switch valve 810 , a second switch valve 820 , and a third switch The valve 830 and the fourth switch valve 840. When the bubbles in the flow channel 180 are flushed by the bubble flushing assembly 60, the first switch valve 810 and the third switch valve 830 are opened, and the second switch valve 820 and the fourth switch valve 840 are closed, so that the syringe 610, the flow channel 180 and the drain valve are closed. The aerators 620 are connected in series to block the communication between the suction control assembly 40 and the flow channel 180 . The bubble flushing component 60 can flush the bubbles once every 24 hours, which greatly reduces the influence of the bubbles generated at the bottom of the clay plate on the suction and drainage.

Of course, the air-bubble flushing assembly 60 and the suction control assembly 40 are respectively provided with pipelines to communicate with the flow channel 180, and a switch valve can be provided at the outlet and the inlet where the air-bubble flushing assembly 60 and the suction control assembly 40 communicate with the flow channel 180 respectively.

Specifically, the stress loading assembly 20 includes: a driving mechanism and a positioning rod 240, the positioning rod 240 is connected with the driving end of the driving mechanism, and the driving mechanism can drive the positioning rod 240 to move in a preset direction, so as to adjust the non-displacement of the sample container 10. Saturated soil samples are loaded with preset stresses along preset directions.

As shown in FIG. 1 and FIG. 2 , the testing device further includes: a bracket assembly 70 , the bracket assembly 70 is disposed on the bottom plate 110 , and the stress loading assembly 20 is disposed on the bracket assembly 70 . The bracket assembly 70 includes a plurality of first support rods 710, and the plurality of first rods are used to support the driving mechanism, so that the driving mechanism and the bottom plate 110 are relatively fixedly arranged, so that the distance between the driving mechanism and the bottom plate 110 is maintained at a fixed value, thereby making The distance between the accommodating cavities 170 of the driving mechanism is maintained at a fixed value to ensure the accuracy of stress application and improve the test accuracy.

As shown in FIG. 2 , the driving mechanism is a pressure cylinder 210 , a piston 220 is arranged in the cylinder 210 , and the positioning rod 240 is connected with the piston 220 . The movement of the piston 220 in the cylinder 210 drives the positioning rod 240 to move. The piston 220 separates the cylinder 210 into an upper cylinder 210 and a lower cylinder 210, and the piston 220 is driven to move in the cylinder 210 by exhausting or adding air from the upper cylinder 210 and the lower cylinder 210. When the locating rod 240 moves after being stressed, the air pressure of the upper cylinder 210 and the lower cylinder 210 can be released in advance through the air inlet and outlet to be the same as the external ambient air pressure, so that the locating rod 240 drives the piston 220 to move, and the unsaturated soil test is accurately measured. The thickness variation of the sample along the preset direction.

For example, the pressure cylinder 210 may further include a loading rod 230 connected with the piston 220 . The diameter of the cylinder 210 may be 100mm and the height may be 180mm. The piston 220 is connected with the lower positioning rod 240 through the loading rod 230 . The first valve port 260 of the upper cylinder 210 is connected to the pressure supply source of the external air compressor to provide uniform air pressure to the cylinder chamber, and the loading rod 230 provides different vertical stress to the lower unsaturated soil sample under different pressure values. During pressure relief sampling, the air pressure source supplies pressure to the second valve port 250 of the lower cylinder 210, so that the pressure value of the lower part of the dense piston 220 in the cylinder 210 is greater than the pressure value of the upper part, and then the loading rod 230 is lifted upward to facilitate the weighing of the sample.

In addition, the driving mechanism can also be a motor, and the driving shaft of the motor is connected with the positioning rod 240 to drive the positioning rod 240 to reciprocate. Those skilled in the art may also adopt other types of bit driving mechanisms, and any transformation involving the driving mechanism falls within the protection scope of the present disclosure.

The plurality of first support rods 710 may be telescopic rods. By adjusting the height of the first support rods 710 , the distance between the driving mechanism and the accommodating cavity 170 is adjusted.

Wherein, the first support rod 710 may be connected with the bottom plate 110 by welding, screwing, riveting and the like. The first support rod can be a metal material, such as iron, aluminum, copper or alloys thereof, and the first support rod can also be a non-metallic material, such as a hard plastic. Those skilled in the art can make selections as required, and all changes involving the material of the first strut fall within the protection scope of the present disclosure.

Among them, four first support rods 710 may be provided, which are evenly distributed on the bottom plate 110 to form a stable support for the driving mechanism. Of course, two, three, five or more first struts may also be provided to form a support for the driving mechanism, which is not limited in the present disclosure.

The first support rod 710 can be a threaded column, and one end of the first support rod 710 is fixedly connected with the driving mechanism by bolts;

In addition, the first support rod 710 can also be placed on the workbench together with the bottom plate 110, and the bracket assembly 70 is fixed on the workbench.

Among them, as shown in FIG. 2 , the positioning rod 240 is in contact with the top cover 150 , and the support of the top cover 150 is squeezed. The cover 150 is in precise contact to avoid left-right movement. For example, a concave portion may be provided at the end of the positioning rod 240 , and a convex portion may be provided on the top cover 150 , and the concave portion and the convex portion cooperate to form a position where the positioning rod 240 abuts against the top cover 150 . Wherein, the concave portion and the convex portion may be in a hemispherical shape, or may be in a shape such as a triangle or a rectangle, which is not limited in the present disclosure.

As shown in FIG. 2 , the displacement measuring assembly 30 includes a displacement gauge, which is arranged on the positioning rod 240 and moves synchronously with the positioning rod 240 to measure the thickness change of the unsaturated soil sample in the sample container 10 along a preset direction.

Wherein, as shown in FIG. 2 , the bracket assembly 70 further includes a positioning plate 740 and a plurality of second support rods 720 , and the plurality of second support rods 720 are used to support the positioning plate 740 , and the positioning plate 740 may be arranged in parallel with the bottom plate 110 , The positioning plate 740 is provided with a positioning hole through which the positioning rod 240 can extend to the accommodating space. The positioning of the hole can improve the stability of the positioning rod 240 when moving up and down. The displacement meter is arranged on the positioning rod 240 on the side of the positioning plate away from the bottom plate 110, and the measuring end of the displacement meter is in contact with the positioning plate. When the displacement meter moves with the positioning rod 240, the extrusion between the measuring end and the positioning plate The force will change to obtain the distance that the positioning rod 240 moves, so that the thickness change of the unsaturated soil sample in the measuring sample container 10 along the preset direction can be determined.

Wherein, the displacement meter can be, for example, an electronic displacement meter, and the inside of the electronic displacement sensor 310 can be composed of a primary coil, a secondary coil, and a moving iron core. The primary coil inputs a stable sine wave excitation signal. When the sensor contact 320 moves back and forth, it drives the iron core, so that the mutual inductance between the primary coil and the secondary coil changes, and the secondary induction coil outputs a sine wave signal whose amplitude changes accordingly. . Collect the amplitude of this sine wave, you can know the contact moving distance. Of course, the displacement meter can also be a mechanical displacement meter. By measuring the extrusion force between the end and the positioning plate, the elastic force of the spring is changed, thereby changing the position of the pointer, and the displacement of the measurement end can be read through the position of the pointer. , or read the displacement-related data, and obtain the displacement of the measurement tip through calculation. Those skilled in the art can also adopt other types of displacement gauges, and all transformations involving displacement gauges belong to the protection scope of the present disclosure.

The plurality of second support rods 720 may be telescopic rods, and the distance between the displacement meter and the positioning plate can be adjusted by adjusting the height of the second support rods 720 . The displacement gauge can also be arranged on the positioning rod 240 in a position-adjustable manner.

Wherein, the second support rod 720 may be connected with the bottom plate 110 by welding, screwing, riveting, or the like. The second support rod 720 may be a metal material, such as iron, aluminum, copper or alloys thereof, and the second support rod 720 may also be a non-metallic material, such as a hard plastic. Those skilled in the art can make selections as needed, and all changes involving the material of the second strut 720 fall within the protection scope of the present disclosure.

Among them, four second support rods 720 can be provided, which are evenly distributed on the bottom plate 110 to form a stable support for the driving mechanism. Of course, two, three, five or more second support rods 720 may also be provided to form a support for the driving mechanism, which is not limited in the present disclosure.

In addition, the second support rod 720 and the bottom plate 110 can also be placed on the workbench, and the bracket assembly 70 is fixed on the workbench.

Wherein, as shown in FIG. 2, the bracket assembly 70 further includes a sealing ring 730, the sealing ring 730 is arranged on the base, the fixing ring 160 is located in the sealing ring 730, and the sealing ring 730 is enclosed with the positioning plate and the bottom plate 110 to form a closed space, so as to The accommodating space is located in a closed space, so that the entire test process of the unsaturated soil sample is carried out in a closed environment, which avoids the influence of water evaporation on the test results and improves the test accuracy.

The sealing ring 730 has a cylindrical shape, and can be sealedly connected to the positioning plate and the bottom plate 110 by welding, bonding or the like. The sealing ring 730 can be a metal material, such as iron, aluminum, copper or alloys thereof, and the sealing ring 730 can also be a non-metallic material, such as a hard plastic.

The length of the second support rod 720 can be a 185mm threaded post, the positioning plate and one end of the second support rod 720 are connected by bolts, and a rubber sealing ring can be set between the sealing ring 730 and the positioning plate. By adjusting the positioning plate At the position of the second support rod 720, the sealing ring 730 and the positioning plate are sealedly connected through the sealing ring; the bottom plate 110 is provided with a threaded hole, and the other end of the second support rod 720 is fixedly connected to the bottom plate 110 through the screw hole.

Specifically, the suction control assembly 40 includes: a sealed container 410 and a vacuum machine 420, the sealed container 410 is in communication with the flow channel 180, and a pressure relief port 430 is provided on the sealed container 410; the vacuum machine 420 is connected with the sealed container 410 for adjusting the sealing The degree of vacuum within the container 410 .

Wherein, the vacuum machine 420 is connected with the sealed container 410 through a pipeline, a fifth on-off valve 850 can be arranged on the pipeline, and the pumping rate is controlled by the opening degree of the fifth on-off valve 850. The sealed container 410 may be provided with a pressure gauge 440 and a pressure relief port 430 , the pressure in the sealed container 410 may be obtained in real time through the pressure gauge 440 , and the pressure in the sealed container 410 may be consistent with the pressure of the external environment through the pressure relief port 430 .

The material of the sealed container 410 may be, for example, a non-metallic material, such as plastic, rubber, etc., or a metal material, such as aluminum, copper, and the like. For example, the sealed container 410 may be an acrylic sealed tub.

The shape of the sealed container 410 may be cylindrical, rectangular, spherical or irregular, which is not limited in the present disclosure.

The diameter of the sealed container 410 may be more than 5 times that of the fixed ring 160 directly. The diameter of the sealed container 410 may be, for example, 400 mm, and the height of the sealed container 410 may be 30 mm. Of course, the diameter of the sealed container 410 may be less than 5 times, for example, 4.5 times the direct diameter of the fixed ring 160; the diameter of the sealed container 410 may also be, for example, 350mm, 450mm, 500mm, etc., and the height of the sealed container 410 may also be 25mm, 35mm, 40mm etc., which is not limited in the present disclosure.

Illustratively, the present disclosure adopts a sealed container 410 with a diameter of 400 mm. When the liquid level in the sealed container 410 is reduced by 1 mm, the mass of water reduced is 125.6 grams, and the volume of the ring knife used is 76.93 cm ³ (70 mm in diameter, 20 mm in height) , therefore, the drop value of the liquid level in the barrel is much less than 1mm during the whole test process; when the height of the liquid level in the barrel decreases by 1mm, the pressure reduction value due to the drop of the liquid level is 0.0098kPa, which is the smallest change in the suction force of the test matrix of this device. Compared with the unit of 1kPa, the error is less than 0.98%, which meets the test requirements. Meanwhile, since the vacuum degree of water vaporization is -100kPa, in order to avoid water vaporization, the relative air pressure range of the vacuum machine 420 is set to 0kPa to -80kPa.

The pipeline connecting the flow channel 180 may be connected to the side wall of the sealed container 410 , and the pressure relief port 430 may also be provided on the side wall of the sealed container 410 . Of course, the pipeline connecting the flow channel 180 can be connected to the top of the sealed container 410 , and the pressure relief port 430 can also be provided on the top of the sealed container 410 .

As shown in FIGS. 1 and 5 , when the sealed container 410 needs to communicate with the flow channel 180 , the first on-off valve 810 and the third on-off valve 830 are closed, and the second on-off valve 820 and the fourth on-off valve 840 are opened.

As shown in FIG. 1 and FIG. 5 , the water quantity measuring assembly 50 includes a weighing device, and the sealed container 410 is arranged on the weighing device, which can reflect the suction and drainage conditions of the ring knife sample 130 .

The weighing device may include a scale 510 and a tray 520, the tray 520 is set on the scale 510, the sealed container 410 is set on the tray 520, and the weight of the sealed container 410 can be obtained through the scale 510, so that the water in the sealed container 410 can be obtained. The quality of the water in the sealed container 410 can then be obtained.

In addition, the water quantity measuring component 50 can also be a volume measuring device. For example, when the sealed container 410 is in the form of a regular cylinder, the volume of water in the sealed container 410, that is, the liquid level height, can be indirectly obtained by measuring the volume of water in the sealed container 410 through the volume measuring device. The quality of the water in the sealed container 410 can be obtained, and then the change in the quality of the water in the sealed container 410 can be obtained. Those skilled in the art can also measure the quality of water in the sealed container 410 by selecting other water quantity measuring components, which is not limited in the present disclosure.

Specifically, the soil testing device provided by the present disclosure controls the substrate suction according to the following formula:

s=u _a -u _w

Among them, s is the matrix suction, u _a is the pore air pressure, and u _w is the pore water pressure. Different from the traditional and improved pressure plate instrument, this device realizes the matrix suction by changing the pore water pressure of the ring knife soil sample. The pore air pressure of the soil sample is always maintained at the standard atmospheric pressure value, 101.325kPa.

The soil testing device provided in the present disclosure controls the pore water pressure by taking the same principle of changing the pore water pressure by adjusting the pressure water head in the middle of the soil sample as the liquid surface elevation head of the acrylic sealed bucket, according to the following formula:

u _w =P ₀

Among them, P ₀ is the liquid surface pressure, which is controlled by a vacuum machine.

The soil testing device provided by the present disclosure can be used for, but not limited to, the following experimental studies:

(1) Confined compression consolidation test of unsaturated soil under the control of low matrix suction, to explore the compression characteristics of soil under different matrix suction conditions;

(2) Water holding characteristics of unsaturated soil under different stress states, and then explore parameters such as permeability, shear strength and water holding coefficient of unsaturated soil;

(3) Deformation test of unsaturated soil under different stress states, to explore the deformation characteristics of soil under the condition of increasing water content, especially the collapsibility and expansion characteristics under humidification to saturation state.

Specifically, in the confinement compression consolidation test of unsaturated soil under controlled matrix suction, the specific operation method of the soil testing device provided by the present disclosure is as follows:

After the soil sample is prepared, the soil sample is placed in the sample container. According to the principle of controlling the suction force of the matrix in the present disclosure: the pore air pressure is kept constant, and the pore water pressure of the soil sample is changed by controlling different negative pressures by a vacuum machine, and then applying Set the matrix suction, and at the same time, use an electronic displacement meter to monitor the change in soil sample volume. After the soil sample is stable in water absorption and drainage, vertical stress is applied in stages. According to the readings of the precision electronic balance scale and electronic displacement meter, the volume change of the soil sample after it is stabilized under different vertical stress states is determined, and the Porosity ratio (e)-vertical load (p) curve of saturated soil samples under controlled matrix suction state.

Specifically, in the experimental research on collapsibility deformation of unsaturated soil under the controlled matrix suction state, the specific operation method of the soil testing device provided by the present disclosure is as follows:

After the soil sample is prepared, the soil sample is placed in the sample container. According to the principle of controlling the suction force of the matrix in the present disclosure: the pore air pressure is kept constant, and the pore water pressure of the soil sample is changed by controlling different negative pressures through a vacuum machine, and then applying Set the matrix suction, and at the same time, use an electronic displacement meter to monitor the change in soil sample volume. When using the single-line method, apply vertical stress to 200kPa in stages and after the sinking and deformation are stable, turn off the vacuum machine and restore the air pressure in the acrylic sealed barrel to the outside atmospheric pressure, so that the difference between the liquid level in the middle of the soil sample and the right acrylic sealed barrel in water head is Saturated under the condition of 0, according to the readings of the precision electronic balance scale and the electronic displacement meter, the collapsibility deformation of the saturated soil sample after being stabilized under the state of vertical stress of 200 kPa was determined, and the unsaturated soil sample shown in Fig. Porosity ratio (e)-vertical load (p) curve in the control matrix suction state.

Specifically, in the experimental research on the water-holding characteristics of unsaturated soil under different stress states, the specific operation method of the soil testing device provided by the present disclosure is as follows:

After the soil sample is prepared, place the soil sample in the sample container, apply vertical stress, open the valve, make the non-steam water in the acrylic sealed barrel communicate with the saturated clay plate, and make the middle of the soil sample and the liquid level of the right acrylic sealed barrel communicate with each other. Saturate under the condition of 0 head difference, and at the same time, use an electronic displacement meter to monitor the change of soil sample volume. After the soil sample is saturated, the pore air pressure remains constant, and the vacuum machine controls different negative pressures to change the pore water pressure of the soil sample, thereby changing the matrix suction. water content. During the whole test process, the bottom of the clay plate was washed with a bubble washing system every 24 hours to avoid the influence of bubbles on the test results, and the void ratio of the unsaturated soil sample shown in Figure 9 under the control of the matrix suction state was determined ( e) - vertical load (p) curve.

The soil testing device provided by the present disclosure can be used for experimental research on hydro-mechanical properties of unsaturated soil under low matrix suction and testing of engineering design parameters in geotechnical engineering. It is mainly composed of five parts: stress loading component, sample container, bubble flushing component, suction control component and water measuring component. The test device can be used to test the confining compression and consolidation characteristics of unsaturated soil under controlled low matrix suction state, the water holding characteristics of unsaturated soil in the process of increasing/dehumidifying under different stress states, and the unsaturated soil under different stress states. Addition/dehumidification deformation properties. The test device has clear principle, complete functions, simple structure, convenient operation and low cost, and can be a powerful tool for unsaturated soil related experimental research and engineering design parameter testing.

Other embodiments of the present disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or techniques in the technical field not disclosed by the present disclosure . The specification and examples are to be regarded as exemplary only, with the true scope and spirit of the disclosure being indicated by the following claims.

It is to be understood that the present disclosure is not limited to the precise structures described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

A soil testing device, comprising:

a sample container, which is formed with an accommodation cavity and a flow channel at the bottom of the accommodation cavity, the flow passage communicates with the accommodation cavity, and the accommodation cavity is configured to accommodate soil samples;

a stress loading component, disposed corresponding to the sample container, and configured to load a preset stress along a preset direction on the soil sample in the sample container;

a displacement measuring component, disposed corresponding to the sample container, configured to measure the thickness change of the soil sample in the sample container along the preset direction;

a suction control assembly, in communication with the flow channel, configured to apply a preset matrix suction to the soil sample in the sample container;

A water measurement assembly, connected to the suction control assembly, is configured to measure the quality of water in the suction control assembly.
The soil testing device according to claim 1, wherein the soil testing device further comprises:

A bubble flushing assembly, in communication with the flow channel, is configured to flush bubbles in the flow channel.
The soil testing device according to claim 2, wherein the air-bubble flushing assembly comprises:

a syringe, communicated with the inlet of the flow channel, for injecting flushing agent into the flow channel;

The exhauster, communicated with the outlet of the flow channel, is used for accommodating the liquid flushed out of the flow channel, and the flushed air bubbles can be discharged through the exhaust hole.
The soil testing device of claim 1, wherein the sample container comprises:

bottom plate;

a fixing ring, which is arranged on the bottom plate, and cooperates with the bottom plate to form the accommodating cavity with an open end;

Wherein, the flow channel is formed at the corresponding position of the bottom plate and the accommodating cavity, and the inlet and the outlet of the flow channel are drawn out through the bottom plate.
The soil testing device according to claim 4, wherein the sample container further comprises:

an air intake layer, arranged on the bottom plate;

The filter layer is arranged on the side of the air inlet layer away from the bottom plate, and the soil sample is arranged between the air inlet layer and the filter layer;

a water-permeable layer, located on the side of the filter layer away from the bottom plate;

The top cover is arranged on the side of the water permeable layer away from the bottom plate.
The soil testing device according to claim 4, wherein the soil testing device further comprises:

A bracket assembly, the bracket assembly is arranged on the bottom plate, and the stress loading component is arranged on the bracket assembly.
The soil testing device of claim 1, wherein the stress loading assembly comprises:

Drive mechanism;

a positioning rod, connected with the driving end of the driving mechanism, and the driving mechanism can drive the positioning rod to move along the preset direction, so as to measure the soil sample in the sample container along the preset direction Load preset stress.
The soil testing device of claim 7, wherein the displacement measurement assembly comprises:

The displacement gauge is arranged on the positioning rod and moves synchronously with the positioning rod to measure the thickness change of the soil sample in the sample container along the preset direction.
The soil testing device of claim 1, wherein the suction control assembly comprises:

a sealed container, communicated with the flow channel, and a pressure relief port is provided on the sealed container;

A vacuum machine is connected to the airtight container for adjusting the degree of vacuum in the airtight container.
The soil testing device according to claim 9, wherein the water measurement component comprises:

Weight measuring equipment, the sealed container is arranged on the weight measuring equipment.