CN212459313U - Pressure plate instrument for measuring soil-water characteristic curve - Google Patents

Abstract

The utility model discloses a measure pressure plate appearance of soil water characteristic curve, including the industrial computer, the controller of being connected with the industrial computer, the regulator cubicle and the pressure consolidation host computer of being connected with the controller, the pressure consolidation host computer includes vertical loading frame and pressure chamber, the controller can be controlled vertical loading frame and pressure chamber, carries out axial loading through setting up the axial pressurized cylinder on the crossbeam of vertical loading frame to the sample in the pressure chamber. The device can obtain complete dehumidification and moisture absorption soil-water characteristic curves under different stress states, and a pressure plate of the instrument is provided with two pressure meters and regulators with different specifications, so that the test precision is improved in a low-pressure range; the design of the device can control the substrate suction force to reach 1500 kPa; the soil-water characteristic curve related to the stress measured by the device is more accurate than the traditional soil-water characteristic curve and is closer to the property of the soil on site.

Description

Pressure plate instrument for measuring soil-water characteristic curve

Technical Field

The utility model relates to a geotechnical engineering measuring device especially relates to a measure pressure plate appearance of native water characteristic curve.

Background

The research of the soil-water characteristic curve is an important content of unsaturated soil research, which mainly refers to a relation curve between matrix suction formed in unsaturated soil and water content or saturation in soil, and embodies the water holding capacity of a soil body under the action of the matrix suction. The shear strength, permeability, diffusion, bulk strain and the like of unsaturated soil can be effectively determined through the soil-water characteristic curve, so that the method plays an important role in unsaturated soil mechanics.

Research finds that many factors influence the unsaturated soil-water characteristic curve, besides the influence factors of the soil body (soil body type, mineral composition, pore structure, initial water content, initial pore ratio and the like), the influence factors also include the influence of external factors such as the stress state, consolidation pressure, temperature and the like of the soil body, and the influence of the factors is finally reflected in the aspects of the air inlet value, the dehumidification rate, the residual water content and the like of the soil-water characteristic curve of the unsaturated soil. However, the test research on the unsaturated soil-water characteristic curve usually adopts a soil-water characteristic curve pressure plate instrument, which is mainly used for researching the consolidation characteristic of unsaturated soil, and the soil-water characteristic curve and the hysteresis quality of soil body in the moisture absorption and dehumidification processes.

Therefore, in order to more accurately and effectively research the characteristics of unsaturated soil, the accuracy of each index of the soil-water characteristic curve pressure plate instrument is improved to a certain extent. Aiming at the effects of the stress state and consolidation pressure of the soil body, the method mainly embodies the loading method of the test instrument on the axial force of the sample and the stability of the axial force loading in the test process in the aspect of the test instrument.

At present, a conventional test method for determining the unsaturated soil-water characteristic curve is a pressure plate method, and can be suitable for measuring soil-water characteristic parameters of a soil sample with a substrate suction force of less than 1500 kPa. The principle is that a saturated argil plate with a high air intake value is utilized, the matrix suction force of a soil sample is controlled by adopting an axis translation technology, namely, certain air pressure is applied to control the pore water pressure, so that the pore water pressure is kept to be zero, and the air pressure is the currently applied matrix suction force value. The existing unsaturated soil testing instrument generally comprises a piston type sealed combined pressure chamber, a top cover, a base and a transparent sleeve of the pressure chamber can load or remove a soil sample through assembly and disassembly, each assembly part of the pressure chamber realizes the sealed assembly of the pressure chamber through a clamping groove, a sealing strip and a fastening member, the fastening member reinforces each angle of the pressure chamber, the top cover of the pressure chamber is provided with an air inlet hole communicated with the inside and the outside, the base of the pressure chamber is provided with an water inlet hole and a water outlet hole communicated with the outside, the head of a piston is an end bearing plate, and a loading end of the piston extending to the outside of the pressure chamber can bear external pressure, and a displacement sensor for measuring the vertical translational displacement of the piston in the pressure chamber is also arranged at the loading end, a porous argil plate is arranged at the bottom of the pressure chamber, and a soil sample is placed on the porous argil plate for measuring soil-water characteristic parameters. Under the action of the applied matrix suction, the soil sample absorbs or drains water so as to achieve the balance of the suction inside the soil sample, namely the balance between the matrix suction inside the soil sample and the applied matrix suction. When the water volume of the soil sample is not changed any more, the water content of the soil sample at the moment is calculated through the change of the water head in the variable volume pipe. The air pressure is then varied and the water content is calculated after the suction has equilibrated. Repeating the operation for a plurality of times to obtain a series of substrate suction forces and corresponding soil sample water contents, thereby obtaining a relation curve between the substrate suction forces and the water contents. Meanwhile, assuming that the sample does not deform in the circumferential direction in the test process, the saturation of the soil sample under a certain substrate suction force can be obtained through measuring the vertical deformation of the soil sample, and then the relation curve between the substrate suction force and the saturation can be obtained. But there is a precondition for measuring the relation between saturation suction, that is, the sample does not separate from the cutting ring or does not generate annular deformation, and the sample is supposed to be not contracted or expanded in annular volume, and then the volume change can be obtained only by the vertical displacement meter. For most unsaturated soils, the soil body generates elastic expansion in the process of wetting, namely moisture absorption, and the soil sample generates obvious plastic shrinkage in the process of drying, namely moisture removal. For example, bentonite is a highly expansive soil which undergoes significant volume expansion during moisture absorption. To obtain the relationship between saturation and suction, it is necessary to remove the suction, remove the sample, measure the mass and volume of the sample, and reload the sample when each stage of suction is balanced. In the process, a certain test error is generated in the unloading and reloading processes, so that an accurate relation curve between saturation and suction cannot be obtained in real time, and the application of the unsaturated soil test device is influenced by artificial errors generated due to high technical requirements in the measuring process. In fact, the existing unsaturated soil testing instrument has the disadvantages of complicated structure, high design and manufacturing cost and inconvenient operation.

SUMMERY OF THE UTILITY MODEL

To the problem that exists, the utility model provides a measure pressure plate appearance of soil water characteristic curve, the steerable matrix suction of the device is up to 1500kPa, except can measuring soil sample volume change under different matrix suction, can also exert one-dimensional load (KO state promptly) for soil sample to the total volume change that can the accurate measurement soil body.

The utility model adopts the technical proposal that:

the pressure plate instrument for measuring the soil-water characteristic curve comprises an industrial personal computer, a controller connected with the industrial personal computer, a pressure regulating cabinet connected with the controller and a pressure consolidation host, wherein the pressure consolidation host comprises a vertical loading frame and a pressure chamber, the pressure chamber is positioned on a bottom plate of the vertical loading frame, the controller can control the vertical loading frame and the pressure chamber, and a sample in the pressure chamber is axially loaded through an axial pressurizing cylinder arranged on a cross beam of the vertical loading frame;

the pressure chamber comprises a test die base, an argil plate base, a protective cylinder and a test die upper cover, wherein the argil plate base and the protective cylinder are arranged on a bottom plate and are arranged in a cavity formed by fixing the test die base and the test die upper cover through a pull rod, a boss is arranged in the middle of the upper part of the test die upper cover, a bidirectional movement loading cylinder is arranged on the boss, a lower piston rod at the bottom of the bidirectional movement loading cylinder penetrates through a first mounting hole in the test die upper cover and enters an inner cavity of the protective cylinder, a lower pressure head is arranged at the lower end of a lower piston rod, and an upper pressure head is arranged at the upper end of an upper piston rod at the top of the bidirectional movement loading cylinder;

the test mold base is provided with a first step-shaped mounting groove for mounting and fixing the argil plate base, a first groove along the circumferential direction of the argil plate base is arranged in the middle of the first step-shaped mounting groove, and a first sealing washer is arranged in the first groove; the test mould is characterized in that an argil plate is embedded in the upper portion of the argil plate base, a second step-shaped mounting groove is formed in the outer side of the argil plate, a second groove along the circumferential direction of the bottom of the pile casing is formed in the middle of the second step-shaped mounting groove, a second sealing washer is arranged in the second groove, the upper end of the pile casing is embedded in a containing groove in the bottom of the test mould upper cover, a third sealing washer is arranged at the position, in contact with the bottom of the test mould upper cover, of the pile casing, and a soil sample is filled in the pile casing.

Preferably, the pressure chamber further comprises a compactor, and the soil sample is compacted in the pile casing layer by layer through the compactor.

Preferably, the water inlet hole formed in the clay plate base is in close butt joint communication with a water inlet hole formed in the pressure regulating cabinet base, the water inlet hole is connected with a water outlet at the bottom of the pressure regulating cabinet through a water inlet pipe, the clay plate base is further provided with a water outlet hole, the water inlet hole is communicated with the water outlet hole, the water outlet hole is in close communication with a first water outlet hole and a second water outlet hole formed in the mold testing base, the first water outlet hole is formed in the side wall of the mold testing base, the second water outlet hole is formed in the bottom of the mold testing base, the first water outlet hole and the second water outlet hole are respectively connected with a first branch pipeline and a second branch pipeline, the tail ends of the first branch pipeline and the second branch pipeline are communicated with a water outlet pipe through a first four-way connector, the tail end of the water outlet pipe is connected with a water return port at the bottom of, the tail end of the third branch pipeline is connected with a pore pressure sensor which is electrically connected with the controller, and the water outlet pipe, the first branch pipeline, the second branch pipeline and the third branch pipeline are respectively provided with a control valve; an air inlet hole which is opened towards the pressure chamber is formed in the upper cover of the test mold, and the air inlet hole is connected with a pressure regulating port on the pressure regulating cabinet through a negative pressure pipe.

Preferably, the vertical loading frame further comprises four columns for fixing the bottom plate and the cross beam, wherein a fixing frame is arranged on one column, a displacement sensor is fixed on the fixing frame, the lower end of the displacement sensor abuts against the displacement measuring plate, the displacement measuring plate is fixed on an upper piston rod of the bidirectional movement loading cylinder and is electrically connected with the controller, and a first air inlet and a first air return port are further formed in the bidirectional movement loading cylinder.

Preferably, the axial supercharging cylinder is fixed on the cross beam, a cylinder extension rod arranged at the bottom of the axial supercharging cylinder penetrates through a second mounting hole in the middle of the cross beam, a cylinder axial pressure head is arranged at the bottom of the cylinder extension rod, an axial pressure sensor is arranged on the cylinder axial pressure head, and the axial pressure sensor is electrically connected with the controller; a second air inlet, a third air inlet and a second air return port are respectively arranged on the same side of the axial supercharging cylinder, and a third air return port is arranged on the other side surface of the axial supercharging cylinder; first air inlet, second air inlet and third air inlet pass through the second four-way connection head and advance the pressure union coupling, the end of the pressure pipe is connected with the gas outlet on the regulator cabinet lateral wall, first return air mouth, second return air mouth and third return air mouth pass through the third four-way connection head and are connected with the back pressure union coupling, the end of back pressure pipe is connected with the mouth that loses heart on the regulator cabinet lateral wall.

Preferably, the pressure regulating cabinet is further provided with two water inlets, a cylinder pressure regulating valve and a low pressure gauge for axially pressurizing the pressure chamber, a cylinder lifting button, a high pressure regulating valve and a high pressure gauge for applying pressure to the inside of the pressure chamber, and a negative pressure display, a first regulating switch and a water injection pipe are arranged above the water outlet, a second regulating switch and a water drain pipe are arranged above the water return port, an exhaust pipe is arranged at a position close to the water drain pipe, the bottom of the exhaust pipe is connected with a hose, and the tail end of the hose is connected to the water outlet pipe; the side wall of the pressure regulating cabinet is also provided with an air transmission port, and the air transmission port is connected with an air pump through an air transmission pipeline.

Compared with the prior art, the beneficial effects of the utility model are that:

1. for any soil, the device can obtain complete dehumidification and moisture absorption soil-water characteristic curves under different stress states, and a pressure plate of the instrument is provided with two pressure meters and regulators with different specifications, so that the test precision is improved in a low-pressure range; the design of the device can control the substrate suction force to reach 1500 kPa; compared with the traditional soil-water characteristic curve pressure plate instrument, the device can not only measure the volume change of the soil sample under different substrate suction forces, but also apply one-dimensional load (namely KO state) to the soil sample, and can accurately measure the total volume change of the soil body; the soil-water characteristic curve related to the stress measured by the device is more accurate than the traditional soil-water characteristic curve and is closer to the property of the soil on site.

2. The utility model discloses well sample drainage/water absorption and displacement are measurationed and are adopted two sets of independent systems to carry out sample drainage/water absorption and adopt horizontal accommodate device, and the displacement is measurationed and is adopted perpendicular buret device, can avoid measuring the influence that the flood peak of pipe was automatic drainage/water absorption to the sample like this.

3. The digital axial displacement sensor is adopted in the application, the axial pressure sensor and the pore air pressure sensor carry out automatic data reading, and meanwhile, a mechanical reading meter adopted by the traditional like products is also reserved. The automatic digital sensor can improve the test control precision, and more importantly, can objectively avoid subjective errors when a mechanical reading device judges the manual reading.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a schematic structural diagram of a pressure plate instrument for measuring a soil-water characteristic curve according to an embodiment of the present invention;

FIG. 2 is a schematic structural view of a pressure consolidation host

FIG. 3 is a cross-sectional view of FIG. 2;

FIG. 4 is a rear view of the base of the trial mold of FIG. 3;

FIG. 5 is a top view of the base of the trial mold of FIG. 3;

FIG. 6 is a front view of the clay plate base of FIG. 3;

FIG. 7 is a top view of the clay plate base of FIG. 3;

FIG. 8 is a block diagram of the drawbar of FIG. 3;

FIG. 9 is a view showing the structure of the upper cover of the test mold in FIG. 3;

FIG. 10 is a block diagram of the bi-directional motion loading cylinder of FIG. 3;

FIG. 11 is a block diagram of the cylinder extension rod of FIG. 3;

fig. 12 is a schematic structural view of a sample saturator in a pressure plate instrument for measuring a soil-water characteristic curve according to an embodiment of the present invention;

fig. 13 is a stress-related soil-water characteristic graph.

Wherein, 1-a controller; 2-a voltage regulating cabinet; 201-a water filling port; 202-low pressure gauge, 203-cylinder regulating valve; 204-a water injection pipe; 205-high pressure gauge; 206-high pressure regulating valve; 207-negative pressure display; 208-cylinder regulating valve; 209-negative pressure meter; 210-a first regulating switch; 211-water outlet; 212-pressure regulating port; 213-a water return port; 214-a second regulating switch; 215-a drain pipe; 216-an exhaust pipe;

3-vertical loading frame; 301-a cross beam; 302-a second mounting hole; 303-column; 304-a backplane; 4-axial supercharging cylinder; 401 — a second air inlet; 402-a third air inlet; 403-a second return air port; 404-cylinder extension bar; 405-cylinder axial ram; 406-axial pressure sensor; 5-bidirectional movement loading cylinder; 501-an upper piston rod; 502-upper ram; 503-lower piston rod; 504-lower ram; 505-a first air inlet; 506-a first return air port;

6-a pressure chamber; 601-testing the upper cover of the mold; 602-an air inlet; 603-a first mounting hole; 604-a receiving groove; 605-boss; 606-air intake; 607-a drawbar; 608-trial mold base; 609-a first water outlet; 610-water inlet hole; 611-a second water outlet; 612-a first step-like mounting groove; 613-first groove; 614-casing; 615-a clay plate base; 616-water inlet hole; 617-a second step-shaped installation groove; 618-second groove; 619-clay plates;

7-a displacement sensor; 8, fixing a frame; 9-a pressure inlet pipe; 10-back pressure pipe; 11-a negative pressure tube; 12-a water inlet pipe; 13-water outlet pipe; 14-a first branch conduit; 15-a second branch conduit; 16-a third branch conduit; 17-pore pressure sensor; 18-a first four-way connection; 19-a second four-way connection; 20-a third four-way connection; 21-a ring cutter saturator; 2101-baffle; 2102-fixing the rod; 2103-cutting ring.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

As shown in fig. 1, the utility model discloses a measure pressure plate appearance of soil water characteristic curve for measure positive pressure dehumidification and negative pressure moisture absorption, including the industrial computer, the controller 1 of being connected with the industrial computer, the regulator cubicle 2 and the pressure consolidation host computer of being connected with controller 1, a serial communication port, the pressure consolidation host computer includes vertical loading frame 3 and pressure chamber 6, pressure chamber 6 is located vertical loading frame 3's bottom plate, controller 1 can control vertical loading frame 3 and pressure chamber 6, carries out axial loading through setting up the axial supercharge cylinder on vertical loading frame 3's crossbeam 301 to the sample in the pressure chamber 6.

As shown in fig. 2 to 10, in the present embodiment, the pressure chamber 6 includes a mold base 608, a clay plate base 615, a protective cylinder 614 and a mold upper cover 601, which are mounted on a bottom plate, the clay plate base 615 and the protective cylinder 614 are mounted in a cavity formed by fixing the mold base 608 and the mold upper cover 601 through a pull rod 607, a boss 605 is disposed in the middle of the upper portion of the mold upper cover 601, a bidirectional movement loading cylinder 5 is disposed on the boss 605, a lower piston rod 503 at the bottom of the bidirectional movement loading cylinder 5 passes through a first mounting hole 603 on the mold upper cover 601 and enters an inner cavity of the protective cylinder 614, a lower ram 504 is disposed at the lower end of the lower piston rod 503, and an upper ram 502 is disposed at the upper end of an upper piston rod 501 at the top of the bidirectional movement loading cylinder 5.

The mold trial base 608 is provided with a first step-shaped mounting groove 612 for mounting and fixing the ceramic plate base 615, a first groove 613 along the circumferential direction of the ceramic plate base 615 is arranged in the middle of the first step-shaped mounting groove 612, and a first sealing gasket is arranged in the first groove 613; the upper portion of the ceramic plate base 615 is embedded with a ceramic plate 619, a second step-shaped mounting groove 617 is formed in the outer side of the ceramic plate 619, a second groove 618 along the circumferential direction of the bottom of the pile casing 614 is formed in the middle of the second step-shaped mounting groove 617, a second sealing washer is arranged in the second groove 618, the upper end of the pile casing 614 is embedded in the containing groove 604 in the bottom of the test mold upper cover 601, a third sealing washer is arranged at the position where the pile casing 614 contacts with the bottom of the test mold upper cover 601, a test soil sample is arranged in the pile casing 614, and when the test soil sample is arranged, the test soil sample can be compacted in a layered mode through a compactor.

Preferably, a water inlet hole 616 formed in the clay plate base 615 is in close butt joint communication with a water inlet hole 610 formed in the pressure regulating cabinet 2, the water inlet hole 610 is connected with a water outlet 211 at the bottom of the pressure regulating cabinet 2 through a water inlet pipe 12, a water outlet hole is further formed in the clay plate base 615, the water inlet hole 616 is arranged in a penetrating manner with the water outlet hole, the water outlet hole is in close communication with a first water outlet hole 609 and a second water outlet hole 911 formed in the mold testing base 608, the first water outlet hole 609 is formed in the side wall of the mold testing base 608, the second water outlet hole 611 is formed in the bottom of the mold testing base 608, the first water outlet hole 609 and the second water outlet hole 611 are respectively connected with a first branch pipeline 14 and a second branch pipeline 15, the tail ends of the first branch pipeline 14 and the second branch pipeline 15 are communicated with a water outlet pipe 13 through a first four-way connector 18, the tail end of the water outlet, the first four-way connector 18 is further connected with a third branch pipeline 16, the tail end of the third branch pipeline 16 is connected with a pore pressure sensor 17, the pore pressure sensor 17 is electrically connected with the controller 1, and the water outlet pipe 13, the first branch pipeline 14, the second branch pipeline 15 and the third branch pipeline 16 are respectively provided with a control valve; an air inlet hole 602 which is opened in the pressure chamber is formed in the test mold upper cover 601, and the air inlet hole 602 is connected with the pressure regulating port 212 on the pressure regulating cabinet 2 through the negative pressure pipe 11.

The pore pressure sensor 17 described above has the following two functions: 1. the pore pressure in the test soil sample can be measured, the control valves on the water outlet pipe and the second branch pipeline are closed, and the control valves on the first branch pipeline and the third branch pipeline are opened; 2. the water pressure at the bottom of the argil plate can be monitored, the control valves on the water outlet pipe and the first branch pipeline are closed, and the control valves on the second branch pipeline and the third branch pipeline are opened; in the two measurement processes, the control valve on the water outlet pipe is in an open state.

Preferably, the axial supercharging cylinder 4 is fixed on the cross beam 301, a cylinder extension rod 404 arranged at the bottom of the axial supercharging cylinder 301 penetrates through the second mounting hole 302 in the middle of the cross beam, a cylinder axial pressure head 405 is arranged at the bottom of the cylinder extension rod 404, an axial pressure sensor 406 is arranged on the cylinder axial pressure head 405, the axial pressure sensor 406 is electrically connected with the controller 1, and a first air inlet and a first air return port are further arranged on the bidirectional movement loading cylinder; a second air inlet 401, a third air inlet 402 and a second air return opening 403 are respectively arranged on the same side of the axial supercharging cylinder 4, and a third air return opening is arranged on the other side surface of the axial supercharging cylinder 4; first air inlet 401, second air inlet 402 and third air inlet 403 are connected with pressure pipe 9 through second four-way connection head 19, the terminal of pressure pipe 9 is connected with the pressurized port on the 2 lateral walls of regulator cubicle, first return air port, second return air port and third return air port are connected with return pressure pipe 10 through third four-way connection head 20, the terminal of return pressure pipe 10 is connected with the mouth that loses heart on the 2 lateral walls of regulator cubicle.

The loading range of the axial supercharging cylinder 4 is 10KN, and the constant pressure can be set randomly; the moving range of the cylinder extension bar 14 is 50 mm. The axial pressure sensor 16 has a range of 1mpa and a constant output of 0.5 mV/V. Adopt the utility model discloses a when the consolidation test is done to the pressure consolidation apparatus (giving the certain vertical pressure of pressure chamber), through the admission pipe to injecting the air in the two-way motion loading cylinder, because the influence of backpressure, can push up piston rod rebound, nevertheless because also got into the air in the axial pressure boost cylinder, atmospheric pressure axial pressure head can move down, under the effort of atmospheric pressure axial pressure head, avoids axial pressure not to receive the influence of backpressure, and is stable when guaranteeing the axial pressure who gets into the pressure chamber. Therefore, the axial supercharging cylinder and the upper pressure head are matched to be used as an axial pressure compensator, the main function is to compensate the counter pressure, and the axial pressure applied to the pressure chamber is stable and is the same as the set value.

In order to further improve the measuring accuracy of the device, a double-precision pressure gauge and a regulator are arranged on the regulating cabinet 2, and the double-precision pressure gauge and the regulator specifically comprise the following components: the pressure regulating cabinet 2 is further provided with two water inlets 201, a cylinder pressure regulating valve 203 and a low pressure gauge 202 for axially pressurizing the pressure chamber 6, a cylinder lifting button 208, a high pressure regulating valve 206 and a high pressure gauge 205 for applying pressure to the interior of the pressure chamber 6 and a negative pressure display 207, a first regulating switch 210 and a water injection pipe 201 are arranged above a water outlet 211, a second regulating switch 214 and a water drain pipe 215 are arranged above a water return port 213, an exhaust pipe 216 is arranged at a position close to the water drain pipe 215, the bottom of the exhaust pipe 216 is connected with a hose, and the tail end of the hose is connected to the water outlet pipe 13; the side wall of the pressure regulating cabinet 2 is also provided with a gas transmission port which is connected with a gas pump through a gas transmission pipeline

The pressure plate instrument for measuring the soil-water characteristic curve of the utility model is applied to measuring the volume weight of sandy soil, gravel materials, mixed gravel, cement stabilized soil and lime stabilized soil, and the particle size of the sandy soil, the gravel materials, the mixed gravel, the cement stabilized soil and the lime stabilized soil is less than or equal to 25 mm; measuring the thickness of the constant-weight layer to be less than or equal to 150 mm.

The utility model discloses a further step of improvement lies in, argil plate is the independent research and development of this unit preparation, and wherein, argil plate includes the component of following part by weight: 8-12% of quartz sand, 2-4% of high clay, 0.5-1.5% of high-temperature curing agent, 14-18% of water and the balance of argil. However, in order to improve the quality and the practicability of the argil plate, the components of the argil plate are limited, and the argil plate comprises the following components in parts by weight: 10% of quartz sand, 3% of high clay, 1% of high-temperature curing agent, 16% of water and the balance of argil. Wherein, the high-temperature curing agent can be high-temperature resistant viscosity agent, the particle size of quartz sand is 0.075mm, and the particle size of pottery clay is 0.045 mm.

The specific preparation method of the argil plate comprises the following steps:

step S1: respectively weighing 48.0g of quartz sand, 14.4g of high clay, 4.8g of high-temperature curing agent, 76.8ml of water and the balance of argil according to 480g of wet weight of argil plate;

step S2: pouring the components weighed in the step S1 into a paste stirrer to stir for 15-20 min, taking out the components after stirring is finished, putting the components into a clay plate mould, and standing for 30-45 min;

step S3: placing the clay plate mould on a hydraulic oil cylinder pressurizing device (jack) for fixing, applying a constant pressure of 600kN along the vertical direction of the mould, and extruding for 3-5 min;

step S4: taking off the clay plate mould, and demoulding to obtain a clay plate initial sample;

step S5: placing the pottery clay plate initial sample in a drying chamber to dry for 4 hours, wherein the temperature in the drying chamber is 20-28 ℃.

Step S6: testing the water content of the primary sample of the clay plate, monitoring the wet density of the clay plate, and if the water content of the primary sample of the clay plate is more than 0.5g, continuing drying the clay plate until the water content of the primary sample of the clay plate is less than or equal to 0.5 g;

step S7: transferring the argil plate initial sample meeting the water content requirement into a high-temperature chamber for high-temperature treatment, wherein the temperature is 1180-1200 ℃, and firing for 4 hours; weighing the high-temperature treated ceramic plate sample, monitoring the dry density of the ceramic plate sample, and ensuring that the water content of the sample of the ceramic plate is less than 0.2g to obtain the ceramic plate with the diameter of 90mm and the thickness of 10 mm;

step S8: and testing the prepared clay plate (which can be placed on a pressure plate instrument for testing), soaking the clay plate in vacuum for 12 hours, then placing the soaked clay plate into a calibration device, adding 100ml of water, applying 300-500 kpa, observing the rising water quantity of a drain pipe on the calibration device, and checking the rising height of liquid in the drain pipe, wherein if the rising of the liquid in the drain pipe indicates that the clay plate is over-aerated, the prepared clay plate is not qualified, and if the height of the liquid in the drain pipe is unchanged, the prepared clay plate is qualified.

In this embodiment, the above-mentioned clay plates currently have two kinds of clay plates with a gas resistance value of 500kpa and a gas resistance value of 1500kpa, and the clay plates are already adhered to the clay plate base when leaving the factory, which is convenient for customers to use.

Secondly, in the embodiment, the protective cylinder has two specifications, wherein the diameter of one protective cylinder is 100 mm; the diameter of another pile casing is 150 mm.

The first embodiment is as follows:

the device comprises the structure, and the pressure chamber also comprises a compaction device which is used for compacting the soil sample in the pile casing in a layered mode so as to reach the preset water content.

The test steps comprise:

1. measuring the dry density and water content of the test soil sample before testing;

2. saturated clay plate: before the pottery clay plate is arranged on the pottery clay plate base, the pottery clay plate is saturated in vacuum immersion water, then the pottery clay plate is arranged on the pottery clay plate base, a pressure chamber is arranged, and then the saturated pottery clay plate is repeatedly washed to discharge air in the pottery clay plate.

3. Preparing a soil sample: utilizing a compaction device to compact the soil sample in a sample bearing cylinder in a layering manner;

4. connecting a sample device: after the sample is installed, the bottom of the argil plate base is installed into a first step-shaped installation groove of the test mold base, the top of the protective cylinder is installed in an accommodating groove in the bottom of the test mold upper cover, the test mold base and the test mold upper cover are fixed through a pull rod, and then the pressure chamber is fixed and sealed;

type of test

1. A positive pressure dehumidifying sample;

preparation work: before dehumidification, the clay plate and the test soil sample are saturated, wherein the saturation sample: the second adjusting switch is turned to a drainage position, the control valves on the first branch pipeline and the third branch pipeline are opened, the tail end of the negative pressure pipe is connected with a vacuum pump interface, the first adjusting switch is turned to a water inlet position, the water outlet of the water inlet pipe is connected with the water inlet hole of the argil plate base of the chamber, the pressure of the vacuum pump is set to pump the inside of the protective cylinder, water is filled from the bottom of the argil plate until the water level of the left side drain pipe rises stably, and the saturation of the whole sample is described.

(1) Only dehumidifying treatment is carried out: the tail end of the negative pressure pipe is connected to a pressure regulating port on the pressure regulating cabinet, the second regulating switch is turned to a water inlet position, a switch on the hose is opened, the water level change of the drain pipe is observed until the water level does not rise any more, the water quantity is recorded, and the whole dehumidification is completed.

(2) Firstly, solidifying a sample, and then dehumidifying;

and (3) solidifying the sample: connect the pressure inlet of pressure chamber with the gas transmission mouth of controller, open the air pump, through the pressure inlet pipe to the air of injecting in the two-way motion loading cylinder, because the influence of backpressure, can push up the upward movement of last piston rod, at this moment, the air has also been injected into in the axial pressure boost cylinder, atmospheric pressure axial pressure head moves down, support the pressure head, the backpressure of going up the pressure head has been offset, avoid axial pressure not to receive the influence of backpressure, it is unanimous with the pressure value that the pressure head actually gives the test soil sample down to guarantee to set for the pressure value, axial pressure boost cylinder and last pressure head here cooperate as the axial pressure compensator, the main function is compensation backpressure, it is stable when guaranteeing the axial pressure of applying to the pressure chamber.

Dehumidifying the sample: the tail end of the negative pressure pipe is connected to a pressure regulating port on the pressure regulating cabinet, the second regulating switch is turned to a water inlet position, a switch on the hose is opened, a control valve on the first branch pipeline is opened, the water level change of the drain pipe is observed until the water level does not rise any more, the water quantity is recorded, and the whole dehumidification is completed.

(3) Dehumidifying while solidifying the sample (solidifying the sample under the same pressure and time, checking the time and quality corresponding to the water yield of the sample, and repeatedly dehydrating): the tail end of the negative pressure pipe is connected to a pressure regulating port on the pressure regulating cabinet, the second regulating switch is turned to a water inlet position, a switch on the hose is opened, a control valve on the first branch pipeline is opened, meanwhile, a pressurizing port of the pressure chamber is connected with a gas transmission port of the controller, the air pump is opened, the same axial pressure is given to the sample soil sample, the water level change of the water discharge pipe is observed until the water level does not rise any more, the water quantity is recorded, and the whole dehumidification is completed.

2. Negative pressure moisture absorption sample;

preparation work: preparing a test soil sample, putting the test soil sample into a pile casing, and compacting layer by using a compactor; the end of the negative pressure tube was then connected to a vacuum pump.

(1) Only moisture absorption treatment is carried out: turning the first regulating switch to a drainage position, wherein the tail end of the water inlet pipe is connected to a water inlet hole of the argil plate base (namely a water inlet hole on the test mould base); and then opening a second regulating switch to turn to a water inlet position, connecting the tail end of a water outlet pipe to a water outlet hole (namely a first water outlet hole on a test mould base) on the argil plate base, opening a control valve on a first branch pipeline, setting a negative pressure value through an industrial personal computer, displaying the negative pressure value in a pressure chamber through a negative pressure display, adjusting a vacuum pump valve in a grading manner, sucking water from the bottom of the argil plate by different negative pressures until the water level of a main water pipe drops to a certain water level, recording time, and finishing moisture absorption of the whole sample.

(2) Firstly, solidifying a sample, and then performing moisture absorption treatment;

and (3) solidifying the sample: the pressurizing port of the pressure chamber is connected with the gas transmission port of the controller, the gas pump is opened, air is injected into the bidirectional movement loading cylinder through the pressure inlet pipe, the air pushes the upper piston rod to move upwards under the influence of counter pressure, at the moment, air is also injected into the axial pressurizing cylinder, the air pressure axial pressure head moves downwards to abut against the upper pressure head, the counter pressure of the upper pressure head is counteracted, the axial pressure is prevented from being influenced by the counter pressure, the set pressure value is ensured to be consistent with the pressure value actually applied to the test soil sample by the lower pressure head, the axial pressurizing cylinder and the upper pressure head are matched to be used as an axial pressure compensator which mainly has the function of compensating the counter pressure, and the axial pressure applied to the pressure chamber is ensured to be stable;

moisture absorption treatment: turning the first regulating switch to a drainage position, wherein the tail end of the water inlet pipe is connected to a water inlet hole of the argil plate base (namely a water inlet hole on the test mould base); and opening a second regulating switch to turn to a water inlet position, connecting the tail end of a water outlet pipe to a water outlet hole (namely a first water outlet hole on a test mould base) on the argil plate base, opening a control valve on a first branch pipeline, setting a negative pressure value through a computer, displaying the negative pressure value in a pressure chamber through a negative pressure display, adjusting a vacuum pump valve in a grading manner, sucking water from the bottom of the argil plate by different negative pressures until the water level of a main water pipe drops to a certain water level, recording time, and finishing moisture absorption of the whole sample.

(3) And (3) carrying out moisture absorption treatment while solidifying the sample: turning the first regulating switch to a drainage position, wherein the tail end of the water inlet pipe is connected to a water inlet hole of the argil plate base (namely a water inlet hole on the test mould base); and opening a second regulating switch to rotate to a water inlet position, connecting the tail end of a water outlet pipe to a water outlet hole (namely a first water outlet hole on a test mould base) on the argil plate base, opening a control valve on a first branch pipeline, setting a negative pressure value through a computer, displaying the negative pressure value through a negative pressure display, connecting a pressurizing port of a pressure chamber with a pressurizing port of a controller, opening an air pump, applying certain axial pressure to the test soil sample through a lower pressure head on a bidirectional motion loading air cylinder, simultaneously, adjusting a vacuum pump valve in a grading manner, sucking water from the bottom of the argil plate by different negative pressures until the water level of a main water pipe drops to a certain water level, recording time, and finishing moisture absorption of the whole sample.

Example two

The difference from the first embodiment is that when preparing the soil sample, a plurality of ring cutter soil samples can be loaded in a ring cutter saturator (the ring cutter saturator is shown in fig. 11), the ring cutter saturator comprises at least three partition plates, the partition plates are connected through fixing rods and fixed through locking nuts, a ring cutter is placed between the two partition plates, a test soil sample is loaded in the ring cutter, and the diameter of the ring cutter saturator is small, so that the test soil sample which can be loaded is limited, and the ring cutter saturator can only be used for unsaturated soil consolidation test and dehumidifying test when being placed in a protective cylinder.

In the test process, if the coarse-grained soil selected by the test sample is larger than or equal to 25mm, the diameter of the pile casing is selected to be 150 mm. When absorbing moisture and dehumidifying the sample, the corresponding air pressure resistance value should be selected to obtain the pottery clay plate, and if not replaced, the result value should be corrected.

In the test process, the industrial personal computer has the functions of collecting, monitoring and recording force values and displacement deformation in real time and drawing curve graphs, in addition, the multichannel collection of displacement and test data can be realized, the test data can be exported and edited, the test time can be randomly preset, the data collection is automatically stopped when the time is reached, the sampling storage time period can be randomly set, and the minimum time is 100ms and the maximum time is 60000 ms.

In the test, any vertical load can be applied to a soil sample, the vertical pressure is applied and controlled through a high-low pressure gauge and a corresponding pressure regulator by utilizing a load pressure frame with an axial pressurizing cylinder and a bidirectional movement loading cylinder, and the vertical pressure change is accurately monitored by utilizing a high-precision pressure sensor.

The water inlet and the water outlet in the test soil sample can continuously and accurately measure the water volume change at any moment through the water volume measuring system. Because the soil sample is in the ko state, the change of the total volume of the soil sample can be monitored by a method of measuring the change of the height of the soil sample by a displacement sensor of a linear variable differential transformer.

The utility model discloses a theory of operation: the method comprises the steps of applying a certain vertical pressure to a test soil sample by matching an axial pressurizing cylinder and a bidirectional movement loading cylinder, and controlling the substrate suction force of the soil sample by utilizing a saturated argil plate with a high air intake value and adopting an axis translation technology. The pressure of the pore water is kept to be zero, a certain air pressure is applied to the container filled with the soil sample through high-pressure compressed air, the pressure of the pore water is controlled through a high-pressure gauge and a low-pressure gauge and a regulator, and the value of the compressed air read by the pressure gauge is also the currently applied substrate suction value. Under the action of the external matrix suction, the soil sample absorbs or drains water so as to achieve the suction balance inside the soil sample. When the water volume of the soil sample no longer changes, it indicates that the matrix suction inside the soil sample is in equilibrium with the applied matrix suction. The pressure value of compressed air measured by the pressure gauge is the current soil sample matrix suction value, and meanwhile, the water content of the soil sample at the moment can be calculated according to the change of the water volume. The air pressure is then changed and the water content is calculated after the suction has been equalized. Repeating the operation for multiple times can obtain a series of substrate suction values and corresponding soil sample water content values, and drawing the data can obtain a soil-water characteristic curve related to stress (as shown in figure 12)

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. The pressure plate instrument for measuring the soil-water characteristic curve comprises an industrial personal computer, a controller connected with the industrial personal computer, a pressure regulating cabinet connected with the controller and a pressure consolidation host, and is characterized in that the pressure consolidation host comprises a vertical loading frame and a pressure chamber, the pressure chamber is positioned on a bottom plate of the vertical loading frame, the controller can control the vertical loading frame and the pressure chamber, and a sample in the pressure chamber is axially loaded through an axial pressurizing cylinder arranged on a cross beam of the vertical loading frame;

the pressure chamber comprises a test die base, an argil plate base, a protective cylinder and a test die upper cover, wherein the argil plate base and the protective cylinder are arranged on a bottom plate and are arranged in a cavity formed by fixing the test die base and the test die upper cover through a pull rod, a boss is arranged in the middle of the upper part of the test die upper cover, a bidirectional movement loading cylinder is arranged on the boss, a lower piston rod at the bottom of the bidirectional movement loading cylinder penetrates through a first mounting hole in the test die upper cover and enters an inner cavity of the protective cylinder, a lower pressure head is arranged at the lower end of a lower piston rod, and an upper pressure head is arranged at the upper end of an upper piston rod at the top of the bidirectional movement loading cylinder;

the test mold base is provided with a first step-shaped mounting groove for mounting and fixing the argil plate base, a first groove along the circumferential direction of the argil plate base is arranged in the middle of the first step-shaped mounting groove, and a first sealing washer is arranged in the first groove; the test mould is characterized in that an argil plate is embedded in the upper portion of the argil plate base, a second step-shaped mounting groove is formed in the outer side of the argil plate, a second groove along the circumferential direction of the bottom of the pile casing is formed in the middle of the second step-shaped mounting groove, a second sealing washer is arranged in the second groove, the upper end of the pile casing is embedded in a containing groove in the bottom of the test mould upper cover, a third sealing washer is arranged at the position, in contact with the bottom of the test mould upper cover, of the pile casing, and a soil sample is filled in the pile casing.

2. The pressure plate instrument for measuring soil and water characteristics according to claim 1, wherein the pressure chamber further comprises a compactor through which the soil sample is compacted in layers in the casing.

3. The pressure plate instrument for measuring soil-water characteristic curve according to claim 2, wherein the clay plate base is provided with a water inlet hole in close butt joint communication with a water inlet hole on the test mold base, the water inlet hole is connected with a water outlet at the bottom of the pressure regulating cabinet through a water inlet pipe, the clay plate base is further provided with a water outlet hole, the water inlet hole and the water outlet hole are arranged in a through manner, the water outlet hole is in close communication with a first water outlet hole and a second water outlet hole on the test mold base, the first water outlet hole is located on the side wall of the test mold base, the second water outlet hole is located at the bottom of the test mold base, the first water outlet hole and the second water outlet hole are respectively connected with a first branch pipeline and a second branch pipeline, the ends of the first branch pipeline and the second branch pipeline are communicated with a water outlet pipe through a first four-way connector, and the end of the water outlet pipe, the first four-way connector is also connected with a third branch pipeline, the tail end of the third branch pipeline is connected with a pore pressure sensor, the pore pressure sensor is electrically connected with the controller, and the water outlet pipe, the first branch pipeline, the second branch pipeline and the third branch pipeline are respectively provided with a control valve; an air inlet hole which is opened towards the pressure chamber is formed in the upper cover of the test mold, and the air inlet hole is connected with a pressure regulating port on the pressure regulating cabinet through a negative pressure pipe.

4. The pressure plate instrument for measuring soil-water characteristic curve according to claim 2, wherein the vertical loading frame further comprises four columns for fixing the bottom plate and the beam, wherein one column is provided with a fixing frame, a displacement sensor is fixed on the fixing frame, the lower end of the displacement sensor is abutted against the displacement measuring plate, the displacement measuring plate is fixed on the upper piston rod of the bidirectional movement loading cylinder and is electrically connected with the controller, and the bidirectional movement loading cylinder is further provided with a first air inlet and a first air return port.

5. The pressure plate instrument for measuring soil-water characteristic curve according to claim 4, wherein the axial pressurizing cylinder is fixed on the cross beam, the cylinder extension rod arranged at the bottom of the axial pressurizing cylinder passes through the second mounting hole in the middle of the cross beam, the cylinder axial pressure head is arranged at the bottom of the cylinder extension rod, and the axial pressure sensor is arranged on the cylinder axial pressure head and is electrically connected with the controller; a second air inlet, a third air inlet and a second air return port are respectively arranged on the same side of the axial supercharging cylinder, and a third air return port is arranged on the other side surface of the axial supercharging cylinder; first air inlet, second air inlet and third air inlet pass through the second four-way connection head and advance the pressure union coupling, the end of the pressure pipe is connected with the pressure port on the regulator cabinet lateral wall, first return air mouth, second return air mouth and third return air mouth pass through the third four-way connection head and are connected with the back pressure union coupling, the end of back pressure pipe is connected with the mouth that loses heart on the regulator cabinet lateral wall.

6. The pressure plate instrument for measuring soil-water characteristic curve according to claim 5, wherein the pressure regulating cabinet is further provided with two water inlets, a cylinder pressure regulating valve and a low pressure gauge for axially pressurizing the pressure chamber, a cylinder lifting button, a high pressure regulating valve and a high pressure gauge for applying pressure to the inside of the pressure chamber and a negative pressure display, a first regulating switch and a water injection pipe are arranged above the water outlet, a second regulating switch and a water drain pipe are arranged above the water return port, an exhaust pipe is arranged at a position close to the water drain pipe, the bottom of the exhaust pipe is connected with a hose, and the tail end of the hose is connected to the water outlet pipe; the side wall of the pressure regulating cabinet is also provided with an air transmission port, and the air transmission port is connected with an air pump through an air transmission pipeline.

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