Device and method for measuring soil-water characteristic curve of cracked clay in full suction range

Abstract

The invention discloses a device and a method for measuring a soil-water characteristic curve of cracked clay in a full suction range, and relates to the technical field of unsaturated soil testing, the device comprises a test box body, a pressure control assembly and a moisture content measuring assembly, the test box body comprises a first test cavity and a water storage cavity, a soil sample is placed in the first test cavity, and the water storage cavity is communicated with the pressure control assembly; the water delivery cavity is arranged at the bottom end of the first test cavity and is communicated with the first test cavity; the pressure control assembly comprises a water pressure control mechanism and an air pressure control mechanism, the water pressure control mechanism comprises a horizontal pipe, the first end of the horizontal pipe is connected with the water storage cavity, the horizontal pipe can move up and down relative to the test box body, the air pressure control mechanism comprises an air compressor, and the air compressor is connected with the first test cavity; the moisture content measuring assembly comprises a dropper and a shooting piece, and the dropper is arranged on the horizontal pipe; wherein the preset low matrix suction range is 0.01-1 Kpa, and the preset high matrix suction range is larger than 1 Kpa; the soil-water characteristic curve of the soil sample in the full suction range can be obtained, and the accuracy is high.

Description

Technical Field

[0001] The invention relates to the technical field of unsaturated soil testing, and in particular to a device and method for measuring a soil-water characteristic curve of cracked clay in a full suction range. Background Art

[0002] In the natural environment, cracks are generated in clay due to the rainfall-evaporation cycle. These cracks are interconnected to form a crack network, which significantly affects the hydraulic properties of the soil. The cracks act as seepage channels to promote the infiltration of water, causing the pore water pressure of the unsaturated soil to increase suddenly in a short period of time. The increase in pore water pressure will cause the shear strength of the soil to decrease, forming a continuous sliding surface at the bottom of the cracks, leading to slope failure. There have been a lot of studies on slope failure, which focus on the occurrence, development and mechanical properties of cracked soils. There are very limited studies on the impact of cracks on the hydraulic properties of clay.

[0003] The soil-water characteristic curve is a curve that describes the relationship between suction and water content in unsaturated soil. Based on this curve, the permeability coefficient, strength, volume strain and pore water change law of the soil can be determined. It plays an important role in the seepage analysis of clay soil. In actual engineering, slope stability analysis and evaluation, dam leakage analysis and volume change research also need to use the theory of soil-water characteristic curve. Therefore, the measurement and research of soil-water characteristic curve is of great significance in the field of unsaturated soil research.

[0004] The existing soil-water characteristic curve measurement includes two methods: direct measurement by existing instruments and fitting based on empirical models. Among them, direct measurement by instruments is generally carried out using a pressure plate instrument based on axis translation technology. Usually, the pressure is applied from 1Kpa, and only the change curve of the transition zone and the unsaturated residual zone can be measured. In the boundary effect zone, a small change in matrix suction will cause a large change in water content, which is difficult to control accurately. Summary of the invention

[0005] The main purpose of the present invention is to provide a device and method for measuring the soil-water characteristic curve of cracked clay within the full suction range of the matrix suction.

[0006] To achieve the above object, the present invention proposes a device for measuring the soil-water characteristic curve of cracked clay in the full suction range, comprising:

[0007] The test box comprises a first test cavity and a water storage cavity, wherein the first test cavity is used to place the soil sample, and the water storage cavity is arranged at the bottom end of the first test cavity and communicated with the first test cavity so that water in the soil sample can flow into the water storage cavity;

[0008] A pressure control assembly, comprising a water pressure control mechanism and an air pressure control mechanism, wherein the water pressure control mechanism comprises a horizontal tube, wherein a first end of the horizontal tube is connected to the water storage cavity, and the horizontal tube can move in an up-and-down direction relative to the test box to control the matrix suction of the soil sample to change within a preset low matrix suction range, and the air pressure control mechanism comprises an air compressor, wherein the air compressor is connected to the first test cavity and is used to fill air into the first test cavity to control the matrix suction of the soil sample to change within a preset high matrix suction range; and

[0009] A moisture content measuring assembly, comprising a dropper and a photographing member, wherein the dropper is arranged on the horizontal tube and is used to measure the amount of water lost by the soil sample, and the photographing member is used to photograph the soil sample to obtain the volume of the soil sample;

[0010] The preset low matrix suction range is 0.01-1 KPa, and the preset high matrix suction range is greater than 1 KPa.

[0011] Optionally, the water pressure control mechanism further includes:

[0012] A liftable table comprises a table and a lifting and lowering adjustment structure, wherein the lifting and lowering adjustment structure is arranged at the lower side of the table and is used to drive the table to move relative to the test box along the up and down direction, and the horizontal tube is arranged on the table; and

[0013] A micrometer is arranged on the table and is used to measure the moving height of the horizontal tube.

[0014] Optionally, the lifting and lowering adjustment structure includes:

[0015] At least one support column extending along the up-down direction;

[0016] At least one screw rod is extended along the up-down direction, the screw rod is sleeved in a corresponding one of the support columns, and is threadedly connected to the support column and connected to the table;

[0017] At least one worm gear is disposed at the upper end of a corresponding support column, sleeved on the outer circumference of the screw rod, and threadedly connected to the screw rod; and

[0018] At least one worm, disposed on one side of the support column in the first direction and extending in the second direction, the worm being adapted to mesh with at least one worm wheel to drive the worm wheel to rotate when rotating around its axis, so that the worm wheel drives the screw to move relative to the support column in the up-down direction;

[0019] The first direction, the second direction and the up-down direction are arranged perpendicular to each other in pairs.

[0020] Optionally, the water pressure control mechanism further includes a connecting hose, one end of which is connected to the first end of the horizontal tube, and the other end of which is connected to the water storage cavity.

[0021] Optionally, the air pressure control mechanism also includes an air intake pipe, a pressure gauge and an air intake valve, one end of the air intake pipe is connected to the air compressor, and the other end is connected to the first test chamber, and the pressure gauge and the air intake valve are both arranged on the air intake pipe.

[0022] Optionally, the device for measuring the soil-water characteristic curve of cracked clay in the full suction range further comprises:

[0023] a water storage and flushing component connected to the water storage cavity and used for flushing bubbles into the water storage cavity; and

[0024] The bubble volume measuring component is used to measure the bubble volume.

[0025] Optionally, the water pressure control mechanism further comprises a first switch, and the first switch is arranged between the horizontal pipe and the water storage cavity;

[0026] The water storage and flushing component comprises:

[0027] a water tank connected to the water storage cavity through a first connecting pipe, and used to fill water into the water storage cavity to flush out bubbles, wherein the first connecting pipe is provided with a second switch; and

[0028] a water storage bottle connected to the water storage cavity through a second connecting pipe, and used to receive water for flushing bubbles flowing out of the water storage cavity, wherein a third switch is provided on the second connecting pipe;

[0029] The bubble volume measuring assembly comprises a volume measuring tube, which is arranged on the second connecting tube and located between the water storage bottle and the water storage cavity, and is used to measure the volume of bubbles. The second connecting tube is also provided with a fourth switch, which is located between the volume measuring tube and the water storage cavity.

[0030] The third switch is located between the water storage bottle and the volume measuring tube.

[0031] Optionally, the test box further includes a second test cavity, which is spaced and sleeved on the outer periphery of the first test cavity and the water storage cavity, is communicated with the first test cavity, and is sealed;

[0032] The air compressor is connected to the second test cavity;

[0033] The photographing element is arranged on the inner wall of the second test cavity.

[0034] Optionally, the first test chamber includes:

[0035] The cavity body is cylindrical; and

[0036] The permeable stone is arranged at the bottom end of the cavity body, and is used for carrying the soil sample and allowing the water in the soil sample to flow into the water storage cavity.

[0037] The present invention also provides a method for measuring the soil-water characteristic curve of cracked clay in the full suction range, which is applicable to a device for measuring the soil-water characteristic curve of cracked clay in the full suction range. The method for measuring the soil-water characteristic curve of cracked clay in the full suction range comprises the following steps:

[0038] Step S1, preparing a soil sample, and placing the soil sample in a first test cavity;

[0039] Step S2, connecting the test box, the pressure control component and the moisture content measurement component;

[0040] Step S3, controlling the height of the horizontal pipe of the water pressure control mechanism in the pressure control assembly in the up-down direction to control the matrix suction of the soil sample within a preset low matrix suction range, measuring the amount of water lost by the soil sample through the dropper in the moisture content measurement assembly, and obtaining the volume of the soil sample through the camera in the moisture content measurement assembly, and calculating the volume moisture content of the soil sample at different matrix suctions within the preset low matrix suction range according to the measured amount of water lost by the soil sample and the corresponding soil sample volume;

[0041] Step S4, controlling the matrix suction of the soil sample within a preset high matrix suction range through the air compressor of the air pressure control mechanism in the pressure control assembly, measuring the amount of water lost by the soil sample through the dropper, and obtaining the volume of the soil sample through the photographing element, and calculating the volume moisture content of the soil sample at different matrix suctions within the preset high matrix suction range according to the measured amount of water lost by the soil sample and the corresponding volume of the soil sample;

[0042] Step S5, obtaining a soil-water characteristic curve of the soil sample according to the volumetric water content of the soil sample at different matrix suctions within the preset low matrix suction range and the preset high matrix suction range.

[0043] In the technical solution of the present invention, the height of the horizontal tube of the water pressure control mechanism can be controlled to control the matrix suction of the soil sample to change within the preset low matrix suction range, that is, 0.01 to 1 Kpa, to meet the needs of measuring the boundary effect zone of the soil-water characteristic curve. The amount of air filled into the first test cavity by the air compressor can be controlled to control the matrix suction of the soil sample to change within the preset high matrix suction range, that is, greater than 1 Kpa, to meet the needs of measuring the transition zone and unsaturated residual zone of the soil-water characteristic curve. Combined with the amount of water lost by the soil sample measured by the dropper and the volume of the soil sample obtained by the shooting element, the volume moisture content of the soil sample at different matrix suctions can be calculated. In this way, the soil-water characteristic curve of the soil sample in the full suction range can be obtained with high accuracy, providing accurate soil moisture characteristic data for understanding the water transmission and storage characteristics of the soil under different suction conditions. At the same time, the device for measuring the soil-water characteristic curve of cracked clay in the full suction range provided by the present invention is simple to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0045] Figure 1 A schematic diagram of the structure of an embodiment of a device for measuring soil-water characteristic curve of cracked clay in the full suction range provided by the present invention;

[0046] Figure 2 for Figure 1 Schematic diagram of the structure of the device for measuring the soil-water characteristic curve of cracked clay in the full suction range;

[0047] Figure 3 for Figure 1 Schematic diagram of a part of the structure of a device for measuring soil-water characteristic curve of cracked clay in the full suction range;

[0048] Figure 4 for Figure 1 Schematic diagram of a part of the structure of a device for measuring soil-water characteristic curve of cracked clay in the full suction range;

[0049] Figure 5 for Figure 1 A perspective view of the test box of the device for measuring the soil-water characteristic curve of cracked clay in the full suction range;

[0050] Figure 6A flow chart of the method for measuring the soil-water characteristic curve of cracked clay in the full suction range provided by the present invention.

[0051] Description of Figure Numbers:

[0052]

[0053]

[0054] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0057] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0058] The existing soil-water characteristic curve measurement includes two methods: direct measurement by existing instruments and fitting based on empirical models. Among them, direct measurement by instruments is generally carried out using a pressure plate instrument based on axis translation technology. Usually, the pressure is applied from 1Kpa, and only the change curve of the transition zone and the unsaturated residual zone can be measured. In the boundary effect zone, a small change in matrix suction will cause a large change in water content, which is difficult to control accurately.

[0059] In view of this, the present invention provides a device 100 for measuring soil-water characteristic curve of cracked clay in the full suction range. Figures 1 to 5 An embodiment of a device 100 for measuring soil-water characteristic curve of cracked clay in a full suction range provided by the present invention.

[0060] See also Figures 1 to 5 The device 100 for measuring the soil-water characteristic curve of cracked clay in the full suction range includes a test box 1, a pressure control component 2 and a moisture content measurement component 3. The test box 1 includes a first test cavity 11 and a water storage cavity 12. The first test cavity 11 is used to place a soil sample. The water delivery cavity is arranged at the bottom of the first test cavity 11 and is connected to the first test cavity 11 so that the water in the soil sample can flow into the water storage cavity 12. The pressure control component 2 includes a water pressure control mechanism 21 and an air pressure control mechanism 22. The water pressure control mechanism 21 includes a horizontal pipe 211. The first end of the horizontal pipe 211 is connected to the water storage cavity 12. The horizontal pipe 211 can be relative to the test box 1. The air pressure control mechanism 22 includes an air compressor connected to the first test cavity 11 and used to fill air into the first test cavity 11 to control the matrix suction of the soil sample to change within a preset high matrix suction range; the moisture content measuring component 3 includes a dropper 31 and a shooting component 32, the dropper 31 is provided on the horizontal tube 211, and is used to measure the amount of water lost by the soil sample, and the shooting component 32 is used to shoot the soil sample to obtain the volume of the soil sample; wherein, the preset low matrix suction range is 0.01-1Kpa, and the preset high matrix suction range is greater than 1Kpa.

[0061] In the technical solution of the present invention, the height of the horizontal tube 211 of the water pressure control mechanism 21 can be controlled to control the matrix suction of the soil sample to change within the preset low matrix suction range, that is, 0.01 to 1 Kpa, to meet the needs of measuring the boundary effect zone of the soil-water characteristic curve. The amount of air filled into the first test cavity 11 by the air compressor can be controlled to control the matrix suction of the soil sample to change within the preset high matrix suction range, that is, greater than 1 Kpa, to meet the needs of measuring the transition zone and unsaturated residual zone of the soil-water characteristic curve. Combined with the amount of water lost by the soil sample measured by the dropper 31 and the volume of the soil sample obtained by the shooting element 32, the volume moisture content of the soil sample at different matrix suctions can be calculated. In this way, the soil-water characteristic curve of the soil sample in the full suction range can be obtained with high accuracy, providing accurate soil moisture characteristic data for understanding the water transmission and storage characteristics of the soil under different suction conditions. At the same time, the device 100 for measuring the soil-water characteristic curve of cracked clay in the full suction range provided by the present invention is simple to operate.

[0062] Furthermore, compared with the existing soil-water characteristic curve measuring devices, the device for measuring the soil-water characteristic curve of cracked clay within the full suction range provided by the present invention is larger in size and can meet the representative basic volume requirements of broken soil samples, provide space for the development of cracks, and realize the study of the relationship between crack development and the soil-water characteristic curve.

[0063] In addition, the soil-water characteristic curve measured by the device 100 for measuring the soil-water characteristic curve of cracked clay in the full suction range provided by the present invention can also be used to verify and calibrate soil mechanics models, which is of great significance for applications in agriculture, civil engineering, environmental science and other fields. For example, in civil engineering and construction engineering, it can help engineers optimize the design and reduce problems caused by soil cracking or wetting. In the fields of agriculture and environmental management, it can help optimize irrigation strategies and water resource management.

[0064] It should be noted that, generally, the preset high matrix suction range is specifically 1 to 300 KPa.

[0065] It should also be noted that, in the present invention, the shooting range of the shooting element 32 can fully cover the soil sample, and a certain time interval is set to regularly shoot photos of the soil sample to achieve full observation of the crack development process in the soil sample, and then obtain the volume of the soil sample at different matrix suctions based on the taken photos.

[0066] It should also be noted that the amount of water flowing out of the soil sample under the suction of the matrix, that is, the amount of water lost by the soil sample, flows into the horizontal tube 211 through the water storage cavity 12. In order to avoid evaporation of water and affect the accuracy of the measurement result of the dropper 31, the second end of the horizontal tube 211 is in a closed state.

[0067] For further information, see Figures 1 to 3 The water pressure control mechanism 21 also includes a liftable table 212 and a micrometer 213. The liftable table 212 includes a table 2121 and at least one lifting adjustment structure 2122. The lifting adjustment structure 2122 is arranged on the lower side of the table 2121, and is used to drive the table 2121 to move relative to the test box 1 along the up and down directions. The horizontal tube 211 is arranged on the table 2121; the micrometer 213 is arranged on the table 2121, and is used to measure the moving height of the horizontal tube 211; in this way, the change in the matrix suction of the soil sample can be obtained according to the movement of the horizontal tube 211, and the matrix suction of the soil sample can be controlled with high precision.

[0068] It should be noted that, in the present invention, the height change of the horizontal tube 211 and the change of the matrix suction of the soil sample satisfy the relationship that when the height of the horizontal tube 211 is reduced by 0.5 mm, the matrix suction of the soil sample increases by 0.005 Kpa, so that within the preset low matrix suction range, the change accuracy of the matrix suction of the soil sample is controlled within 0.005 Kpa. More specifically, before the measurement test begins, the height of the horizontal tube 211 is adjusted so that the horizontal tube 211 and the first test cavity 11 are in a balanced state.

[0069] Furthermore, the lifting and lowering adjustment structure 2122 includes at least one support column 21221, at least one screw 21222, at least one worm gear 21223 and at least one worm gear 21224. The support column 21221 is extended along the up-down direction, and the screw 21222 is extended along the up-down direction; the screw 21222 is sleeved in the corresponding support column 21221, and is threadedly connected to the support column 21221, and is connected to the table 2121; the worm gear 21223 is arranged at the upper end of the corresponding support column 21221, and is sleeved The worm 21224 is disposed on the outer periphery of the screw 21222 and is threadedly connected with the screw 21222; the worm 21224 is disposed on one side of the support column 21221 in the first direction and is extended along the second direction; the worm 21224 is adapted to mesh with at least one worm wheel 21223 to drive the worm wheel 21223 to rotate when rotating around its axis, so that the worm wheel 21223 drives the screw 21222 to move relative to the support column 21221 along the up-down direction; wherein the first direction, the second direction and the up-down direction are arranged perpendicular to each other in pairs. In this way, the screw 21222 is driven to move up and down by the rotation of the worm wheel 21223 and the worm 21224, thereby driving the table 2121 to move up and down, thereby realizing the height control of the horizontal tube 211.

[0070] For more details, see Figure 2 and Figure 3 In one embodiment of the present invention, the lifting and lowering adjustment structure 2122 includes two support columns 21221, two screw rods 21222, two worm wheels 21223 and one worm rod 21224. The two support columns 21221 are spaced apart along the second direction. A screw rod 21222 is sleeved in each support column 21221, and a worm wheel 21223 is provided at the upper end of each support column 21221. Both worm wheels 21223 are adapted to mesh with the worm rod 21224. Thus, the two worm wheels 21223 are driven to rotate simultaneously by one worm rod 21224, thereby driving the two screw rods 21222 to move up and down simultaneously, thereby driving the table 2121 to move up and down at the same time.

[0071] Furthermore, in one embodiment of the present invention, the lifting and lowering adjustment structure 2122 further includes a rotating handle, which is disposed at the end of the screw 21222, so that the tester can rotate the rotating handle to drive the worm 21224 to rotate. Of course, in another embodiment of the present invention, the lifting and lowering adjustment structure 2122 further includes a driving motor, and the driving shaft of the driving motor is drivingly connected to the worm 21224 to drive the worm 21224 to rotate.

[0072] Specifically, the liftable table 212 also includes at least one table leg and a connecting column, the table leg is arranged on the lower side of the table 2121, the table leg includes a fixed column extending along the up-down direction and a movable column sleeved in the fixed column, the movable column is fixedly connected to the table 2121, the lifting and lowering adjustment mechanism is arranged on one side of the table leg in the first direction or the second direction, and the screw 21222 is connected to the movable column through the connecting column; in this way, when the screw 21222 moves in the up-down direction, it drives the movable column to move, thereby driving the table 2121 to move, and by arranging the table legs to support the table 2121, the movement stability of the table 2121 is improved.

[0073] Specifically, in one embodiment of the present invention, a mounting seat is provided on the table 2121 , the micrometer 213 is fixedly mounted on the side of the mounting seat by a fixing fixture, and the probe of the micrometer 213 is in contact with the upper surface of the table 2121 .

[0074] For details, please refer to Figures 1 to 3 The water pressure control mechanism 21 also includes a connecting hose 214 , one end of which is connected to the first end of the horizontal tube 211 , and the other end of which is connected to the water storage cavity 12 .

[0075] For details, please refer to Figure 1 and Figure 2 The air pressure control mechanism 22 further includes an air inlet pipe 221, a pressure gauge 222 and an air inlet valve 223. One end of the air inlet pipe 221 is connected to the air compressor, and the other end is connected to the first test cavity 11. The pressure gauge 222 and the air inlet valve 223 are both arranged on the air inlet pipe 221. In this way, the inflation state of the first test cavity 11 is controlled by the air inlet valve 223, and the air pressure is obtained by the pressure gauge 222, so as to control the matrix suction of the soil sample with high precision.

[0076] It should be noted that, in the present invention, the variation accuracy of the matrix suction of the soil sample within the preset high matrix suction range is 0.1 KPa.

[0077] For details, please refer to Figures 1 to 4 The device 100 for measuring the soil-water characteristic curve of cracked clay in the full suction range also includes a water storage flushing component 4 and a bubble volume measuring component 5. The water storage flushing component 4 is connected to the water storage cavity 12 and is used to flush bubbles by passing water into the water storage cavity 12; the bubble volume measuring component 5 is used to measure the volume of bubbles. In this way, when the water in the soil sample flows into the water storage cavity 12, the gas in the soil sample gradually precipitates, and bubbles are gradually generated in the water storage cavity 12, water can be passed into the water storage cavity 12 through the water storage flushing component 4 to flush the bubbles; at the same time, the bubble volume is measured by the bubble volume measuring component 5 to correct the test measurement data, reduce the influence of bubbles on the test measurement data, and improve the accuracy of the test results.

[0078] For further information, see Figures 1 to 3 The water pressure control mechanism 21 also includes a first switch 215 , which is disposed between the horizontal tube 211 and the water storage cavity 12 .

[0079] The water storage and flushing component 4 includes a water tank 41 and a water storage bottle 43. The water tank 41 is connected to the water storage cavity 12 through a first connecting pipe 42, and is used to fill water into the water storage cavity 12 to flush bubbles. The first connecting pipe 42 is provided with a second switch 45; the water storage bottle 43 is connected to the water storage cavity 12 through a second connecting pipe 44, and is used to receive water flowing out of the water storage cavity 12 to flush bubbles. The second connecting pipe 44 is provided with a third switch 46; in this way, the first switch 215 is closed, and the second switch 45 and the third switch 46 are opened, so that the water tank 41 continuously supplies water to the water storage cavity 12 until there are no bubbles in the water storage cavity 12, and the flushing is completed, and the water for flushing the bubbles flows into the water storage bottle 43 through the second connecting pipe 44, and the second switch 45 and the third switch 46 are closed.

[0080] It should be noted that, in one embodiment of the present invention, the height of the water tank 41 is greater than the height of the test box 1, so that the water in the water tank 41 can flow into the water storage cavity 12 by gravity. More specifically, a support frame is provided at the lower side of the water tank 41 for support, and the support frame makes the height of the water tank 41 greater than the height of the test box 1.

[0081] For further information, see Figure 1 , Figure 2 and Figure 4 The bubble volume measuring component 5 includes a volume measuring tube 51, which is arranged on the second connecting tube 44 and located between the water storage bottle 43 and the water storage cavity 12, and is used to measure the bubble volume. The second connecting tube 44 is also provided with a fourth switch 52, and the fourth switch 52 is located between the volume measuring tube 51 and the water storage cavity 12; the third switch 46 is located between the water storage bottle 43 and the volume measuring tube 51. In this way, before flushing the bubbles, the second switch 45, the third switch 46 and the fourth switch 52 are turned on, so that the second connecting tube 44 is filled with water and saturated, and the water level in the volume measuring tube 51 is the same as the water level in the second connecting tube 44; when flushing, the water level in the volume measuring tube 51 is recorded, and the water flow for flushing the bubbles is controlled to be a steady-state flow. The bubbles in the water storage cavity 12 are flushed out and enter the volume measuring tube 51 through the second connecting tube 44. The bubbles slowly rise in the volume measuring tube 51, and the rising bubbles occupy the position where the water in the volume measuring tube 51 is located. The water at the original position flows out, causing the water level in the volume measuring tube 51 to drop, and the water level drop height is calculated and converted into the mass of water, so as to correct the test measurement data.

[0082] Furthermore, in one embodiment of the present invention, the diameter of the volume measuring tube 51 is greater than the diameter of the second connecting tube 44 , so that the bubbles can enter the volume measuring tube 51 when flowing through the bottom of the volume measuring tube 51 .

[0083] For further information, see Figure 5 The test box 1 further includes a second test cavity 13, which is spaced and sleeved on the outer periphery of the first test cavity 11 and the water storage cavity 12, is connected to the first test cavity 11, and is sealed; the air compressor is connected to the second test cavity 13; and the camera 32 is arranged on the inner wall of the second test cavity 13. In this way, the overall sealing of the test box 1 is improved, thereby improving the accuracy of the test measurement results.

[0084] For further information, see Figure 5The first test cavity 11 includes a cavity body 111 and a permeable stone 112. The cavity body 111 is cylindrical. The permeable stone 112 is arranged at the bottom of the cavity body 111 for carrying the soil sample and allowing the water in the soil sample to flow into the water storage cavity 12.

[0085] More specifically, in one embodiment of the present invention, the permeable stone 112 is snap-fitted to the inner wall of the cavity body 111 .

[0086] Of course, in another embodiment of the present invention, the first test cavity 11 includes a cavity body 111 and a ceramic disk. The cavity body 111 is cylindrical. The ceramic disk is arranged at the bottom end of the cavity body 111 for carrying the soil sample and is provided with at least one through hole for the water in the soil sample to flow into the water storage cavity 12.

[0087] The present invention also provides a method for measuring the soil-water characteristic curve of cracked clay in the full suction range, which is applicable to the device for measuring the soil-water characteristic curve of cracked clay in the full suction range as described above, please refer to Figure 6 , the measuring method comprises the following steps:

[0088] Step S1, preparing a soil sample, and placing the soil sample in a first test cavity.

[0089] Specifically, in this step, a cylindrical soil sample with a diameter of 280 mm and a height of 200 mm is prepared according to the designed dry density, and is placed in a vacuum saturation box for saturation to obtain the soil sample, and then the soil sample is placed in the first test cavity.

[0090] Step S2, connecting the test box, the pressure control component and the moisture content measurement component.

[0091] Specifically, in this step, the first switch is turned on to connect the horizontal tube, the dropper and the water storage cavity, and the air inlet valve is opened to connect the air compressor and the test box.

[0092] Step S3, by controlling the height of the horizontal pipe of the water pressure control mechanism in the pressure control assembly in the up and down directions, the matrix suction of the soil sample within the preset low matrix suction range is controlled, and the amount of water lost by the soil sample is measured by the dropper in the moisture content measurement assembly, and the volume of the soil sample is obtained by the shooting element in the moisture content measurement assembly, and the volume moisture content of the soil sample at different matrix suctions within the preset low matrix suction range is calculated according to the measured amount of water lost by the soil sample and the corresponding soil sample volume.

[0093] Step S4, controlling the matrix suction of the soil sample within a preset high matrix suction range through the air compressor of the air pressure control mechanism in the pressure control assembly, measuring the amount of water lost by the soil sample through the dropper, and obtaining the volume of the soil sample through the photographing element, and calculating the volume moisture content of the soil sample at different matrix suctions within the preset high matrix suction range based on the measured amount of water lost by the soil sample and the corresponding soil sample volume.

[0094] Specifically, in the above steps S3 and S4, after the matrix suction of the soil sample is controlled to be a matrix suction within the preset low matrix suction range or within the preset high matrix suction range, when the soil sample reaches de-equilibrium, the reading of the dropper remains stable, and the change in the reading of the dropper at this time is the amount of water lost by the soil sample; the mass of water in the soil sample in a saturated state minus the amount of water lost is the mass of water in the soil sample under the current matrix suction, and the volume of water in the soil sample can be calculated using the density formula, and the soil sample photos taken by the camera are processed and calculated to obtain the volume of the soil sample when it is stable under the current matrix suction, and then the calculated volume of water in the soil sample is divided by the volume of the soil sample to obtain the volume moisture content of the soil sample under the current matrix suction.

[0095] Step S5, obtaining a soil-water characteristic curve of the soil sample according to the volumetric water content of the soil sample at different matrix suctions within the preset low matrix suction range and the preset high matrix suction range.

[0096] Furthermore, during the test measurement process, if bubbles are generated in the water storage cavity, the bubbles are flushed through the water storage flushing component, and the bubble volume is measured through the bubble volume measuring component to correct the measurement data and improve the accuracy of the final result.

[0097] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A device for measuring soil-water characteristic curve of cracked clay in full suction range, characterized in that: The device for measuring the soil-water characteristic curve of cracked clay in the full suction range comprises: The test box comprises a first test cavity and a water storage cavity, wherein the first test cavity is used to place the soil sample, and the water storage cavity is arranged at the bottom end of the first test cavity and communicated with the first test cavity so that water in the soil sample can flow into the water storage cavity; A pressure control assembly, comprising a water pressure control mechanism and an air pressure control mechanism, wherein the water pressure control mechanism comprises a horizontal tube, wherein a first end of the horizontal tube is connected to the water storage cavity, and the horizontal tube can move in an up-and-down direction relative to the test box to control the matrix suction of the soil sample to change within a preset low matrix suction range, and the air pressure control mechanism comprises an air compressor, wherein the air compressor is connected to the first test cavity and is used to fill air into the first test cavity to control the matrix suction of the soil sample to change within a preset high matrix suction range; and A moisture content measuring assembly, comprising a dropper and a photographing member, wherein the dropper is arranged on the horizontal tube and is used to measure the amount of water lost by the soil sample, and the photographing member is used to photograph the soil sample to obtain the volume of the soil sample; The preset low matrix suction range is 0.01-1 KPa, and the preset high matrix suction range is greater than 1 KPa.

2. The device for measuring soil-water characteristic curve of cracked clay in full suction range as claimed in claim 1, characterized in that: The water pressure control mechanism also includes: A liftable table comprises a table and a lifting and lowering adjustment structure, wherein the lifting and lowering adjustment structure is arranged at the lower side of the table and is used to drive the table to move relative to the test box along the up and down direction, and the horizontal tube is arranged on the table; and A micrometer is arranged on the table and is used to measure the moving height of the horizontal tube.

3. The device for measuring soil-water characteristic curve of cracked clay in full suction range as claimed in claim 2, characterized in that: The lifting and lowering adjustment structure comprises: At least one support column extending along the up-down direction; At least one screw rod is extended along the up-down direction, the screw rod is sleeved in a corresponding one of the support columns, and is threadedly connected to the support column and connected to the table; At least one worm gear is disposed at the upper end of a corresponding support column, sleeved on the outer circumference of the screw rod, and threadedly connected to the screw rod; and At least one worm, disposed on one side of the support column in the first direction and extending in the second direction, the worm being adapted to mesh with at least one worm wheel to drive the worm wheel to rotate when rotating around its axis, so that the worm wheel drives the screw to move relative to the support column in the up-down direction; The first direction, the second direction and the up-down direction are arranged perpendicular to each other in pairs.

4. The device for measuring soil-water characteristic curve of cracked clay in full suction range as claimed in claim 1, characterized in that: The water pressure control mechanism also includes a connecting hose, one end of which is connected to the first end of the horizontal pipe, and the other end of which is connected to the water storage cavity.

5. The device for measuring soil-water characteristic curve of cracked clay in full suction range as claimed in claim 1, characterized in that: The air pressure control mechanism also includes an air intake pipe, a pressure gauge and an air intake valve. One end of the air intake pipe is connected to the air compressor, and the other end is connected to the first test cavity. The pressure gauge and the air intake valve are both arranged on the air intake pipe.

6. The device for measuring soil-water characteristic curve of cracked clay in full suction range as claimed in claim 1, characterized in that: The device for measuring the soil-water characteristic curve of cracked clay in the full suction range also includes: a water storage and flushing component connected to the water storage cavity and used for flushing bubbles into the water storage cavity; and The bubble volume measuring component is used to measure the bubble volume.

7. The device for measuring soil-water characteristic curve of cracked clay in full suction range as claimed in claim 6, characterized in that: The water pressure control mechanism further includes a first switch, which is disposed between the horizontal pipe and the water storage cavity; The water storage flushing component comprises: a water tank connected to the water storage cavity through a first connecting pipe, and used to fill water into the water storage cavity to flush out bubbles, wherein the first connecting pipe is provided with a second switch; and a water storage bottle connected to the water storage cavity through a second connecting pipe, and used to receive water for flushing bubbles flowing out of the water storage cavity, wherein a third switch is provided on the second connecting pipe; The bubble volume measuring assembly comprises a volume measuring tube, which is arranged on the second connecting tube and located between the water storage bottle and the water storage cavity, and is used to measure the volume of bubbles. The second connecting tube is also provided with a fourth switch, which is located between the volume measuring tube and the water storage cavity. The third switch is located between the water storage bottle and the volume measuring tube.

8. The device for measuring soil-water characteristic curve of cracked clay in full suction range as claimed in claim 7, characterized in that: The test box also includes a second test cavity, which is sleeved on the outer periphery of the first test cavity and the water storage cavity, is communicated with the first test cavity, and is sealed; The air compressor is connected to the second test cavity; The photographing element is arranged on the inner wall of the second test cavity.

9. The device for measuring soil-water characteristic curve of cracked clay in full suction range as claimed in claim 8, characterized in that: The first test chamber comprises: The cavity body is cylindrical; and The permeable stone is arranged at the bottom end of the cavity body, and is used for carrying the soil sample and allowing the water in the soil sample to flow into the water storage cavity.

10. A method for measuring the soil-water characteristic curve of cracked clay in the full suction range, applicable to the device for measuring the soil-water characteristic curve of cracked clay in the full suction range as claimed in any one of claims 1 to 9, characterized in that: The method for measuring the soil-water characteristic curve of cracked clay in the full suction range comprises the following steps: Step S1, preparing a soil sample, and placing the soil sample in a first test cavity; Step S2, connecting the test box, the pressure control component and the moisture content measurement component; Step S3, controlling the height of the horizontal pipe of the water pressure control mechanism in the pressure control assembly in the up-down direction to control the matrix suction of the soil sample within a preset low matrix suction range, measuring the amount of water lost by the soil sample through the dropper in the moisture content measurement assembly, and obtaining the volume of the soil sample through the camera in the moisture content measurement assembly, and calculating the volume moisture content of the soil sample at different matrix suctions within the preset low matrix suction range according to the measured amount of water lost by the soil sample and the corresponding soil sample volume; Step S4, controlling the matrix suction of the soil sample within a preset high matrix suction range through the air compressor of the air pressure control mechanism in the pressure control assembly, measuring the amount of water lost by the soil sample through the dropper, and obtaining the volume of the soil sample through the photographing element, and calculating the volume moisture content of the soil sample at different matrix suctions within the preset high matrix suction range according to the measured amount of water lost by the soil sample and the corresponding volume of the soil sample; Step S5, obtaining a soil-water characteristic curve of the soil sample according to the volumetric water content of the soil sample at different matrix suctions within the preset low matrix suction range and the preset high matrix suction range.

Images