KR100486837B1 - Measuring device for properties of unsaturated soil - Google Patents

Abstract

Provided is an apparatus for measuring properties of unsaturated soil. The apparatus accurately measures water characteristic curves and calculates hydraulic conductivity equation. Additionally, The apparatus maintains earth and sand at the unsaturated state of a desired moisture content, and performs both of destructive test and shear strength test of the unsaturated soil. The apparatus for measuring properties of unsaturated soil comprises: a first volume-measuring device(10) which measures the amount of water to be absorbed into or released from the earth and sand in order to measure a change of volume moisture ratio of the earth and sand; a second volume-measuring device(20) which contains water, supplies water to the earth and sand to be tested, and measures the amount of water to be supplied; a load cell which contains water, receives water from the second volume measuring device and discharges water to the first volume-measuring device(10) through the earth and sand, and measures load given on the earth and soil in order to calculate shear strength of the earth and sand; a triaxial cell(30) installed with a vertical displacement meter for measuring the vertical displacement amount of the earth and sand; an air diffusion-measuring device(60) which measures the amount of diffused air deviated from the water formed under a second perforated plate; a control portion(40) which has a plurality of control valves(42, 43) for controlling the air pressure of the first and second volume-measuring devices(10, 20), triaxial cell(30) and air diffusion-measuring device(60), and a plurality of pressure gauges(41) which individually display the air pressure to be controlled; and a computer(80) which calculates and outputs the results by using data obtained from the first and second volume-measuring devices(10, 20), triaxial cell(30) and load cell through a predetermined equation.

Description

Unsaturated soil property measuring device {MEASURING DEVICE FOR PROPERTIES OF UNSATURATED SOIL}

The present invention relates to an apparatus for measuring soil properties, and more particularly, to an apparatus for measuring the saturation permeability coefficient of soil, the water characteristic curve of unsaturated soil, and the shear strength of unsaturated soil.

Soil is generally unsaturated, ie unsaturated soils containing soil particles, air and water. And saturated soil composed of soil particles and water is only one extreme situation of the above unsaturated soils. Usually, in the case of slopes that are easily encountered in nature, they usually exist in an unsaturated state. In order to analyze these slopes accurately, the soils of the slope should be viewed as unsaturated rather than saturated.

One of the important input factors in water flow and slope stability analysis of unsaturated soils is the function characteristic curve. In the unsaturated soil, the permeability coefficient is not constant and changes as the water content of the soil is changed. Therefore, the accurate determination of the unsaturated soil equation reflecting the change of permeability coefficient in the unsaturated soil is also an important factor.

Although the unsaturated conditions in the slope penetration analysis or slope stability analysis are considered at present, due to the difficulty in measuring the unsaturated soil water characteristic curve, most of them use values provided in the literature, rather than actual measurements, or use simple measurement equipment. The function characteristic curve is used but its reliability is not high. However, the water quality curve and the permeability coefficient of unsaturated soils are very different depending on the type of soil, so the penetration analysis and the slope stability analysis of unsaturated soils have many problems in accuracy.

Therefore, in order to perform reliable unsaturated soil analysis, the determination of the exact characteristic curve and permeability coefficient of unsaturated soil is an important factor to be preceded.

It is an object of the present invention to provide an apparatus for measuring the properties of unsaturated soils, which is capable of measuring the relationship between the water-containing characteristic curve of unsaturated soils, that is, the volumetric water content of soil soils and the maternal absorption pipe.

In addition, the unsaturated soil property measuring apparatus of the present invention is to test the saturation permeability coefficient of the soil and the shear strength test of the unsaturated soil that can measure the soil fracture state by applying a load after adjusting the water content of the soil to the desired state There is another purpose.

Unsaturated soil physical property measuring apparatus of the present invention for achieving the above object as a device for measuring the moisture characteristic curve of the unsaturated soil, the three-axis cell in which the soil to be measured is installed, and the change in the water content of the soil installed in the triaxial cell In the soil table with a first volume measuring system, a second volume measuring system for measuring the amount of water supplied to the soil during the saturation permeability test, driving means for applying the load to the soil in the triaxial cell, When the water is discharged, the air diffused in the discharged water escapes, forms air bubbles with the water, and is formed in the space existing on the lower side of the second porous plate, and measured by the first volume measuring system. The amount of water includes the volume of the diffused air, so that the volume of the diffused air must be subtracted. The diffused air measuring system for measuring the volume of the diffused air, and each of the first A control unit provided with a plurality of control valves for controlling the air pressure inside the two-volume measuring system, the triaxial cell, and the diffused air measuring system, and a plurality of pressure gauges indicating the respective controlled air pressures, and the first and second volume measuring systems. The air pressure data value of, the air pressure data value of the triaxial cell, and the magnitude of the load applied to the soil by the driving means of the loading table are measured by the load cell, and the measured value of the load cell and the vertical displacement of the soil And a computer for storing, calculating, and outputting the measured values of the vertical displacement gauge.

In addition, the unsaturated earth property measuring apparatus of the present invention is the third pressure conversion for measuring the air pressure inside the first and second pressure transducers and the triaxial cells, respectively, between the three axis cells connected to each of the first and second volumetric meters. A system is installed, and the computer receives the value of the pressure transducer and converts it into a display signal.

In addition, in the unsaturated earth property measuring apparatus of the present invention, a valve for blocking the flow of air and water is further provided at a connection portion between each of the first and second volume measuring systems, the triaxial cell, and the air pressure control means. It features.

In the unsaturated earth property measuring apparatus of the present invention, the computer includes amplifying means for amplifying and outputting the measured value of the load cell, the measured value of the vertical displacement meter, and the measured values of the three pressure transducers, and the analog of the amplifying means. It further comprises an analog / digital converter for converting the output value to digital output.

In addition, in the unsaturated earth property measuring apparatus of the present invention, the triaxial cell further includes a hollow cylindrical tube for accommodating soil therein, and the tube includes a first porous plate having a plurality of through holes formed in the upper side of the soil. A second porous plate having a plurality of fine through-holes of a material that passes through the soil, but does not allow air to pass through is installed on the lower side of the soil, and the bottom plate of the lower portion of the soil Characterized in that the groove is so as to collect the diffused air released from the water.

Hereinafter will be described with reference to the accompanying drawings 1 to 5 unsaturated earth property measuring apparatus 100 according to an embodiment of the present invention.

1 is a front view of an unsaturated earth property measuring apparatus according to an embodiment of the present invention, Figure 2 is a schematic diagram for explaining the operation of the unsaturated earth property measuring apparatus according to an embodiment of the present invention, Figure 3 Figure 3 is a view showing a triaxial cell of the unsaturated earth property measuring apparatus according to an embodiment of, Figure 4 is a measured value control system diagram of the unsaturated earth property measuring apparatus according to an embodiment of the present invention, Figure 5 is an embodiment of the present invention The drawing shows the grooved bottom plate according to the example.

Unsaturated soil physical property measuring device 100 of the present embodiment is the first and second support rods 51, which are installed on the upper stage 50 is provided with a driving means (not shown) for applying a load to the soil (70) 52 are spaced apart at regular intervals in the vertical direction, and the two support bars 51 and 52 are connected to each other by a support bar (not shown). The first support rod (51) has a first volume measuring system (10) capable of measuring the amount of water discharged or absorbed by the air pressure change in order to accommodate the water therein to measure the water content change of the measured soil (70) The second support rod (52) is provided to accommodate water therein, so that the second volume capable of measuring the amount of water supplied to the soil (70) during the saturation permeability test of the measured soil (70) The measuring system 20 is provided.

Between the first support rod 51 and the second support rod 52 is housed in the soil 70 to be measured therein, receiving the water discharged from the second volume measuring system 20 receives the soil sand 70 A discharge rod (not shown) for discharging to the first volume measuring system 10 side, and for transmitting a load from the upper side to the soil sand 70 side to measure the shear strength of the soil sand 70 on the upper side, A load cell 32 for measuring the magnitude of the load loaded on the earth and sand 70 side is installed in the transfer rod, and a vertical displacement gauge 31 for measuring the vertical displacement amount of the earth and sand 70 connected to the transfer rod is installed. Triaxial cell 30 is installed. A diffusion air measurement system 60 is installed at a lower portion of the first volume measurement system 10 installed at the first supporting rod 51 to measure the volume of the diffused air released from the water in the lower portion of the second porous plate 35. do. The measurement of the separated diffused air volume passes water from the first volume measuring system 10 to the diffused air measuring system 60 through the lower portion of the second porous plate 35, and at this time, the water and the diffused diffused air are discharged together. The collected air is collected in a burette (not shown) inside the air measuring system 60 and the collected air amount is measured.

In addition, a space for accommodating a certain amount of air and water is formed therein to control the internal air pressure of the first and second volume measuring systems 10 and 20 and the triaxial cell 30, thereby allowing the first and second volumes to be measured. The water of the measuring system (10, 20) and the air of the triaxial cell is supplied, or the water and air to the first, second volume measuring system (10, 20) and the triaxial cell (30), the supply or supply of the air and water Pneumatic pressure control means (P) for controlling the amount is provided, and a plurality of control valves (42,43) for operating by controlling the air pressure of the air pressure control means (P), and each of the controlled air pressure The control unit 40 provided with a plurality of pressure gauges 41 for displaying individually, the air pressure and water data values of the first and second volume measuring systems 10 and 20, and the air pressure of the triaxial cell 30 And a quantity data value of water, a measured value of the load cell 32, and a measured value of the vertical displacement gauge 31. Lee includes a computer 80 which outputs the calculated result by the set expression.

Between the first and second volumetric measuring system (10,20) and the triaxial cell (30) connected to each of the first and second pressure transducers (90a, 90b) and the third for measuring the pressure in the triaxial cell (30) Three pressure transducers 90c are further installed, and the computer 80 receives the values of the pressure transducers 90a, 90b, and 90c, and converts them into display signals on the screen of the computer 80.

Valves 11 and 21 for controlling the flow of water are further installed at the connection portions of the respective water tanks W, the first and second volume measuring systems 10 and 20 and the triaxial cell 30. .

The computer 80 includes amplifying means 83 for amplifying and outputting the measured value of the load cell 32, the measured value of the vertical displacement meter 31, and the measured value of the pressure transducers 90a, 90b, and 90c. And an analog / digital converter 82 for converting and outputting the analog output value of the amplifying means 83 to digital.

The triaxial cell 30 further includes a hollow cylindrical tube 33 for accommodating the earth and sand 70 therein, and the tube 33 has a plurality of through holes formed in an upper side of the earth and sand 70. The first porous plate 34 is installed, and the second porous plate 35 having a plurality of fine through-holes through which water flowing through the soil 70 passes through the lower side of the earth and sand 70 but does not allow air to pass therethrough. Is installed, the bottom plate 36 in the lower portion of the second porous plate 35, the diffusion air escaped from the water is collected, and serves as a passage when discharging the escaped diffused air to the diffusion air measurement system (60) There is a groove 36a.

The operation will be described below.

In general, the volume water content ratio of the soil sand 70, that is, the volume water content ratio, varies depending on the capillary absorption force (difference between the air gap and the air gap) that the soil includes. That is, the volume function ratio decreases as the maternal absorption increases, whereas the volume function ratio increases when the maternal absorption increases.

First, the earth and sand to be measured should be prepared. Water is added to the optimum water content using a soil sample having a known water content (water content). The soil water content becomes constant, and the soil is sealed to stabilize it for more than one day in order to remove external change factors. Thereafter, after one day, the earth and sand 70 in a separate mold (not shown) is chopped into one layer at a height of 4 to 6 cm. At this time, in order to protect the surface of the second porous plate 35, oil paper (not shown) is installed, and the earth and sand 70 is preferably chopped.

Then, the second porous plate 35 is saturated with water, and after filling the tube 33 of the triaxial cell 30 with water, the water is maintained at 600 kpa for about one hour while the water is passed through the second porous plate 35. Let it flow At this time, the water of the bottom plate 36 is circulated once every 10 minutes, and the circulated water and the diffused air droplets are released to the diffusion air measuring system 60 connected to the bottom plate 36. The second porous plate 35 is not exposed to the air in order to maintain the saturation after the second porous plate 35 is saturated with water until the earth and sand is installed.

Thereafter, the chopped soil 70 is mounted inside the pipe 33. Before mounting the soil 70, rubber rings (not shown) are installed on the first and second porous plates 34 and 35, respectively. Apply grease or the like to increase the sealing effect. When the earth and sand 70 is mounted, the upper surface of the soil sand 70 is in close contact with the first porous plate 34, and the lower surface is in close contact with the second porous plate 35. At this time, in order to protect the surface of the second porous plate 35, it is preferable to install oil paper (not shown) separately. When the mounting of the earth and sand 70 is completed as described above, the triaxial cell 30 is filled with water, and the load cell 32 and the displacement meter 31 are installed on the upper side. At this time, the surrounding point should be installed so that each load cell 32 and the displacement meter 31 does not move due to the characteristics of the measurement object, and is fixed accurately.

Thereafter, the earth and sand 70 is saturated with water, and the air pressure control means P is controlled so that air pressure is applied to the water tank W so that the water in the water tank W forms the lowest level in the first volume measurement system 10. The second volume measurement system 20 supplies the water level to be formed high. In order to remove air existing in the through hole (not shown) of the first porous plate 34, water of the second volume measuring system 20 is supplied to be present in the through hole of the first porous plate 34. To let the air out. When the preparation for saturation of the earth and sand 70 is completed as described above, pressure is applied to the second volume measuring system 20 so that the water of the second volume measuring system 20 flows downward through the earth and sand 70. At this time, if the amount of water reduction of the second volume measuring system 20 is equal to the amount of water flowing into the first volume measuring system 10 through the soil sand 70, the soil sand 70 is saturated with water.

As described above, when the soil 70 is saturated, the saturation permeability coefficient is measured. A pressure of 100 kpa is applied to the second volume measuring system 20 using an air pressure control means P, and the amount of water changed over time is measured. Increase the air pressure in order of 200, 300, 400 kpa and measure the amount of water. The measured values are stored separately in real time in the computer 80.

After the saturation permeability coefficient is measured as described above, while the soil sand 70 is dried, the moisture characteristic curve is measured. First, in order to remove the water in the through hole of the first porous plate 34, the air pressure control means P is applied to apply air pressure, and the valve 21 of the second volume measuring system 20 is opened to completely remove the water. To be removed. At this time, when the air, that is, bubbles are discharged from the second volumetric meter 20, it is determined that the water is completely removed, the valve 21 is closed, and the air pressure control means P is controlled so that no further air pressure is applied. .

Thereafter, the diffusion air measurement system 60 is completely filled with water, and the air pressure is applied to the upper portion of the earth and sand 70 in the triaxial cell 30 using the air pressure control means P. At this time, the valve 11 of the first volume measuring system 10 is opened to measure the amount of water discharged from the earth and sand 70, and the removal and measurement of the escaped diffused air at the bottom of the second porous plate 35 is performed. Do it periodically. Upon removal of the escaped diffused air, first, the valve of the first volume measuring system 10 is closed, the valve connected to the diffuse air measuring system 60 and the second porous plate 35 is opened, and the first volume measuring system 10 is closed. Open the valve 11 to circulate the water to remove air. After the air is completely removed, the valve of the first volume measuring system 10 is closed and the connection valve of the diffusion air measuring system 60 and the second porous plate 35 is closed. Then, the valve of the first volume measuring system 10 is opened again, the amount of water is measured, and at the same time, the change in the water level of the burette in the diffused air measuring system 60 is measured and recorded. At this time, if the amount change value of the water of the first volume measuring system 10 is close to zero, the test is performed by increasing the air pressure in the soil 70 with the triaxial cell 30. The curve obtained by increasing the air pressure is the drying function characteristic curve.

Thereafter, the wet function characteristic curve is measured by reducing the pressure of air in the triaxial cell 30 and the earth and sand 32 as opposed to the above process. That is, each process is the same as the drying process except that the water of the first volume measuring system 10 is supplied to the earth and sand 70 due to the decrease in the air pressure in the earth and sand 70.

When the wetting function curve test is completed as described above, the weight and height of the soil layer 70 are measured, and the saturation permeability coefficient and the water characteristic curve during drying and wetting by a predetermined equation using the measured values in the respective processes. Calculate or show Then, the permeability coefficient of the unsaturated soil is calculated by using a separate formula using the water content curve and the saturation permeability coefficient.

According to the physical property measuring device of the unsaturated soil of the present invention, it is possible to reliably measure the functional characteristic curve of the unsaturated soil, there is an advantage that can calculate the permeability coefficient equation of the unsaturated soil.

In addition, the apparatus for measuring unsaturated soil properties of the present invention maintains soil in an unsaturated state with a desired water content, and has a failure test to apply a load to the soil and a vertical displacement gauge to measure the amount of vertical displacement of the soil. It has the advantage that it can be widely used in unsaturated soil research.

In addition, it is possible to measure up to the capillary absorption of a much larger range than the measurement range of the capillary absorption of the conventional apparatus (difference between the pore air pressure and the pore water pressure of the soil), it is possible to measure a variety of unsaturated soils, thereby improving the compatibility.

An embodiment of the present invention described above and illustrated in the drawings should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can change and change the technical idea of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention, as will be apparent to those skilled in the art.

1 is a front view of an unsaturated earth property measuring apparatus according to an embodiment of the present invention

Figure 2 is a schematic diagram for explaining the operation of the unsaturated earth property measuring apparatus according to an embodiment of the present invention

3 is a view showing a triaxial cell of the unsaturated earth property measuring apparatus according to an embodiment of the present invention

4 is a measured value control system diagram of an apparatus for measuring unsaturated soil properties according to an embodiment of the present invention.

5 is a view showing a bottom plate of the lower portion of the second porous plate according to an embodiment of the present invention.

<Short description of drawing symbols>

10 First volumetric meter 20 Second volumetric meter

30 triaxial cell 40 control unit

50 Loading Stage 60 Diffusion Air Measuring System

70 Tosa 80 Computer

P air pressure control unit W water tank

Claims (5)

Apparatus for measuring the moisture characteristic curve of unsaturated soil, A first volume measuring system capable of measuring the amount of water absorbed or discharged to the soil by the change in air pressure, in order to measure the change in the volumetric water content of the soil measured by receiving water therein; A second volumetric meter which is adapted to receive water inside, which supplies water to the measured soil during the saturation permeability test and measures the amount of water supplied; Accepting the soil to be measured inside, receiving the water discharged from the second volumetric meter and discharged to the first volumetric meter through the soil, and measuring the load applied to the soil to obtain the shear strength of the soil A triaxial cell provided with a load cell, a vertical displacement gauge for measuring the vertical displacement of the earth and sand; A diffused air measurement system capable of measuring an amount of diffused air escaped from water generated under the second porous plate; A control unit provided with a plurality of control switches for controlling the air pressure in each of the first and second volume measuring systems, the triaxial cell, and the diffused air measuring system, and a plurality of pressure gauges for displaying each of the controlled air pressures separately; , A computer which receives the data of the quantity of water of the first and second volume measuring system, the data of the quantity of air and water of the triaxial cell, the measured value of the load cell and the measured value of the displacement meter and calculates and outputs the result by a preset equation. Physical property measuring apparatus of unsaturated soil, comprising a. The method of claim 1, The first and second pressure transducers and the third pressure transducers for measuring the pressure of the triaxial cells, respectively, are installed between the first and second volumetric meters connected to the triaxial cells. The computer further includes the pressure transducers. Device for measuring properties of unsaturated soil, characterized in that for receiving the value of the computer screen and converting the output signal. The method according to claim 1 or 2, The first and the second volume measuring system and the connection portion between the triaxial cell and the water tank is characterized in that the valve for controlling the flow of each water is further characterized in that the property measuring apparatus of unsaturated soil. The method of claim 3, The computer includes amplifying means for amplifying and outputting the measured value of the load cell, the measured value of the displacement meter, and the measured value of the pressure transducer; And an analog / digital converter for converting and outputting the analog output value of the amplifying means to digital. The method of claim 4, wherein In the triaxial cell, Further comprising a hollow cylindrical tube for receiving the soil therein, The pipe is provided with a first porous plate having a plurality of through holes formed on the upper side of the soil, and water flowing through the soil is passed on the lower side of the soil, but a plurality of fine through holes are formed that cannot pass air. 2 perforated plate is installed, The apparatus for measuring physical properties of unsaturated soil is characterized in that the bottom plate having a groove that serves as a passage for collecting the diffused air from the water generated in the lower surface of the second porous plate and the diffused air is removed.