KR20030058412A - Large Cyclic Triaxial Testing Apparatus - Google Patents

Abstract

PURPOSE: A large triaxial vibration test apparatus is provided to secure the safety of various civil structures by using in the evaluation of the safety, the design and the construction of a new civil structure. CONSTITUTION: A triaxial chamber(100) has a test piece(S) therein. A restrictive pressure generator(200) gives the isotropic pressure to be changed from the pneumatic pressure to the water pressure into the test piece. A perpendicular stocking device gives the compressive pressure to the test piece vertically. A hydraulic pressure generator(400) operates the perpendicular stocking device. An electric measuring and controlling device(500) measures the perpendicular load, the perpendicular displacement, the restrictive pressure, the gap water pressure, the volume change of the test piece according to the operation of the perpendicular stocking device and controls the triaxial chamber and the perpendicular stocking device according to testing conditions. Thereby, an input parameter for a design, a construction and a movement analysis is checked exactly.

Description

Large Cyclic Triaxial Testing Apparatus

The present invention relates to a large-scale vibration triaxial tester, and in particular, the static strength and dynamic testing of specimens 300 mm in height and 620 mm in diameter allows shear strength and stress of building materials for construction of civil structures such as dams. Accurate grasp of strain characteristics, calculation of design parameters for the design of port facilities such as breakwaters and quay walls, identification of dynamic characteristics of railway ballast materials, shear strength characteristics of assembly materials for road construction, etc. It is possible to grasp the shear strength and stress-strain characteristics of sand, gravel and crushed stone, and to provide a large vibration triaxial tester capable of conducting large-scale vibration and static triaxial tests of other soil materials.

In general, the triaxial compression test of soil is a test in which the shear state is applied by applying compressive force in the vertical axis direction with the hydraulic pressure applied to the side to reproduce the stress state in the ground of the cylindrical specimen. It can be simulated easily, and it is widely used in soil strength analysis because it can measure pore water pressure by controlling drainage condition.

On the other hand, the assembly materials such as sand, gravel, and sandstone materials, which are used as the main materials for constructing civil structures such as dams, harbor structures, and road fills, show engineering characteristics different from those of general civil engineering materials. For example, reports are often reported in the society that the physical property values obtained in the general small triaxial compression test due to scale effect and penetration effect often overestimate the actual assembly material.

In the case of multi-purpose dams and water-only dams managed by the applicant's water resources corporation, the shear strength of dam materials used in the design and construction of the dams has been determined by using a large direct shear test apparatus. The shear test has a shorter time than the three-axis compression test, but the soil stress-strain relationship is not known, and the result is not suitable for predicting deformation.

In Korea, despite over 700 large dams prescribed by ICOLD (International Commission on Large Dams), large triaxial compression tester is essential for dam body, port structure and road embankment. There is nothing. For this reason, the economic and stable design of the dam section is insufficient due to the excessive or underestimation of the design strength in the construction of the dam, and there is a considerable difficulty in evaluating the stability in the dam to prepare for the earthquake countermeasure.

In addition, according to the related research results so far, knowing the actual shear strength of the construction material according to the stress level in the peel dam, it is possible not only to design the dam economically, but also to know the margin safety. In addition, the dynamic properties of the assembled materials obtained by large triaxial tests under cyclic loading conditions can be used for seismic analysis of dams and port facilities, and dynamic behavior analysis of road pavement.

The present invention has been made to solve the above-mentioned conventional problems, the object of the present invention is to increase the importance of securing the stability of various civil structures including dams, reliable shear strength properties and stress- It is to develop a large vibration triaxial tester that can grasp not only the strain characteristics but also the dynamic properties under cyclic loading conditions, so that it can be actively utilized for stability evaluation, such as earthquake resistance of civil structures according to facility standards, and design and construction of new civil structures.

In order to achieve the above object, the present invention includes a triaxial chamber in which a specimen prepared by compacting the collected sample is installed therein; A restraining pressure generating device for applying an isotropic pressure to the specimen installed in the triaxial chamber to reproduce the stress state in the ground; A vertical loading device that applies a compressive force perpendicular to the specimen installed in the triaxial chamber; A hydraulic generating device for operating the vertical loading device; A large vibration triaxial device comprising an electrical measurement and control device for measuring the volume change and the vertical displacement of the specimen installed in the triaxial chamber according to the operation of the vertical loading device and controlling the triaxial chamber and the vertical loading device according to test conditions Provide a tester.

The triaxial chamber comprises a pressure resistant cylinder, a bottom plate and an upper plate, and a triaxial support strut. The pressure resistant cylinder is made of stainless steel with an inner diameter of 600 mm, an inner diameter of 645 mm, and a height of 1,080 mm so that the triaxial thread itself deforms even under the constraint pressure and dynamic load. To avoid adverse effects on the test results, and to ensure that the pressure cylinder and the upper and lower half are sufficiently closed by O-rings, etc., so that no problems occur in the static and dynamic test results. It supports the strut, upper half, and specimen, and has a hole for ventilation, a pipe for measuring side pressure and pore water pressure, and the upper part has a bearing part at the center so that the loading axis of the vertical loading device can move up and down without friction. It is equipped with a hole for fixing the passage of the cell water supply tube, the pore water pressure, the vertical displacement, and the measuring device during the celebration. It is equipped with two pneumatic cylinders for correcting the load of the loading shaft and loading cap, and four pillars for the triaxial thread are installed inside the pressure resistant cylinder to support the load applied to the upper and lower half during side pressure action. In addition, the triaxial chamber is provided with an observation window having a pressure-resistant structure for detecting the deformation state of the specimen during the test.

The vertical loading device is a device that applies a static load or a dynamic load (repetitive load) in the axial direction to the specimen, and is composed of an actuator, a piston, a load cell and a reload shaft, and the actuator is a swivel head, a high precision displacement gauge, an eccentric prevention compression plate, It is composed of servo valve and high precision load cell. The control and measurement of the actuator is controlled by the control program of the control device described below, and the load cell is a high precision load measuring device for accurately measuring the magnitude of the load applied to the actuator, and is installed between the actuator piston and the loading shaft. In the present invention, a compression and tensile test was adopted.

The electrical measurement and control device is composed of a computer with a built-in control program capable of controlling various sensors, amplifiers and test conditions, and storing and analyzing test result data. The sensors are strain gauge or inductance type in one triaxial chamber. A total of nine sensors are installed, including five types for vertical load measurement, vertical displacement measurement, restraint pressure measurement, pore water pressure measurement, and volume change measurement.

The vertical load measurement sensor is a method installed in the interior and exterior of the triaxial chamber, the sensor installed inside is a type that can withstand the water pressure acting in the triaxial chamber, the vertical displacement sensor is ± 100mm large and Each small size of ± 25mm is installed, and the sensor for volume change is used separately for external and internal measurements.

In addition, the amplifier consists of nine channels required for basic testing, but a total of 16 channels are available in case of increasing microdisplacement or dynamic measurements.

The present invention also installs a movable rail on the bottom plate of the vertical loading device so as to easily move and set the triaxial chamber in which the specimen is installed for the test, and raises the movable trolley on the movable rail. In the middle of the rail is installed a turntable for changing the direction of the moving cart.

The mobile cart can be moved by rolling motion because the wheel is lowered on the rail when moving, and the wheel is lifted when setting on the loading target, and the bottom of the mobile cart is grounded on the bottom plate of the vertical loading device so that stable setting and testing can be performed. It is supposed to be.

On the rear side of the turn table, a stopper for position setting is installed to enable accurate position setting of the moving trolley transferred onto the turn table for setting of the triaxial chamber.

In the present invention, a large specimen with a diameter of 300 mm and a height of 620 mm is tested, so that a boom-type crane is installed at one side of the vertical loading device for setting of the triaxial chamber, and the loading table can support a large force because a lot of force is applied downward. Four props were used, and the height of the actuator was adjustable by giving pitch to the prop.

1 is a schematic diagram showing the overall configuration of a large vibration triaxial tester according to the present invention,

2 is an external view of a large vibration triaxial tester according to the present invention,

3 to 5 are a perspective view, a side cross-sectional view and a planar cross-sectional view showing a triaxial chamber structure of the tester according to the present invention, respectively;

6 is a front view of the loading table;

7 is a plan view of the loading table,

8 is a turn table structure diagram of the loading table;

9 is a front view of the operation panel,

10 is a monitor main screen of a control program

11 is a specimen evaluation screen of the control program,

12 shows a device setting screen of the control program;

13 is a coefficient measurement screen of the control program,

14 is a recording environment setting screen of the control program.

15 shows an adjustment screen of the control program;

16 is a recording data review screen of a control program;

17 shows a channel setting screen of the control program;

18 is a flow chart showing a process of a large triaxial compression test according to the present invention,

19 is a cross-sectional view showing a state in which the specimen is positioned on the bottom pedestal of the triaxial chamber;

20 is a graph showing the relationship between the sequential stress and the restraint pressure in Test Example 1;

21 is a graph showing the relationship between the sequential stress and the restraint pressure in Test Example 2;

22 is a stress strain relationship graph in Test Example 2,

23 to 25 are graphs of the repeated loading triaxial test results for calculating the attenuation constants in Test Example 2.

* Explanation of symbols for main parts of the drawings

100: triaxial chamber 110: pressure resistant cylinder

120: bottom 130: upper half

140: prop 150: base pedestal (pedestal)

160: pneumatic cylinder 170: observation window

200: restraining pressure generating device 210: compressor

300: vertical loading device 310: actuator

320: piston 330: reload shaft

340: loading stage 350: prop

360: cradle 370: bottom plate

380: moving cart 390: turntable

400: hydraulic generator 410: servo valve

500: measurement and control device 501,502: vertical load detection sensor (load cell)

503: vertical displacement sensor

504: internal differential pressure sensor 505: external differential pressure sensor

506: side pressure sensor 507: pore water pressure sensor

508: back pressure sensor V1 ~ V14: valve

Hereinafter, the configuration of a large vibration triaxial tester according to the present invention and a method for testing a specimen using the same will be described in detail with the accompanying drawings.

1 is a system diagram showing the overall configuration of a large vibration triaxial tester according to the present invention, Figure 2 is an external view of a large vibration triaxial tester according to the present invention.

1 and 2, the large vibration triaxial tester of the present invention includes a triaxial chamber 100 in which a specimen S prepared by compacting the collected sample is installed therein; A restraining pressure generating device 200 for applying an isotropic pressure to the specimen S installed in the triaxial chamber 100; Vertical loading device 300 for applying a compressive force perpendicular to the specimen (S) installed in the triaxial chamber (100); A hydraulic generating device 400 for operating the vertical loading device 300; According to the operation of the vertical loading device 300, the vertical load and vertical displacement, the restraint pressure, the pore water pressure and the volume change applied to the specimen S installed in the triaxial chamber 100 are measured, and the triaxial chamber 100 and the vertical It comprises a; electrical measurement and control device 500 for controlling the loading device 300 according to the test conditions.

In the schematic diagram of FIG. 1, the solid line is a vacuum pressure line, the dotted line is a pneumatic line, the dashed line is a line for signal transmission from various sensors to an amplifier, the amplifier to a computer, and the dashed line is a control line for feedback control.

In the schematic diagram of FIG. 1, reference numerals 501 and 502 denote 75 to 50 ton load cells, respectively, and a 75 ton load cell 501 is installed between the piston 320 of the actuator 310 and the loading shaft 330, and the 50 ton load cell 502. Silver is installed between the lower end of the loading shaft 330 extending into the triaxial chamber 100 and the specimen (S) between the bearing portion 132 and the loading shaft 330 formed in the upper half 130 of the triaxial chamber 100. The measurement error of the vertical load due to friction can be corrected.

Reference numeral 503 denotes a vertical displacement measurement sensor, 504 and 505 denote internal differential pressure sensors and external differential pressure sensors, respectively, and reference numerals 506, 507 and 508 denote side pressure sensors, pore pressure sensors and back pressure sensors, respectively. On the other hand, 510 and 511 are double pipe burettes, 512 and 513 are tanks, and 514 are degassing tanks.

On the other hand, reference numeral 520 is an amplifier, and 530 is an A / D and D / A converter installed between the amplifier 520 and the computer 540.

3 to 5 are a perspective view, a side cross-sectional view, and a planar cross-sectional view showing the structure of the triaxial chamber 100 of the tester according to the present invention, respectively, wherein the triaxial chamber 100 according to the present invention is a pressure-resistant cylinder 110 and a bottom plate 120. ) And the upper half 130, and comprises a triaxial support pillar (140).

The pressure resistant cylinder 110 is made of stainless steel with an inner diameter of 600 mm, an inner diameter of 645 mm, and a height of 1,080 mm so that the triaxial chamber 100 itself does not deform even under the restraint pressure and dynamic load. The gap between (120 and 130) is sufficiently closed by O-rings, etc. so as to prevent problems in static and dynamic test results.

The bottom plate 120 supports the pressure-resistant cylinder 110 and the triaxial chamber support 140, the upper half 130 and the specimen (S) on the bottom pedestal 150, and measures the hole, side pressure and pore pressure measurement for the ventilation. The hole for the pipe is formed, the upper half 130 is the bearing portion 132 is mounted in the center so that the loading axis 330 of the vertical loading device 300 can move up and down without friction, the cell (Cell) A hole for fixing the passage of the water supply tube, the pore water pressure, the vertical displacement, and the axial measurement device is formed, and two pneumatic cylinders 160 for correcting the load of the loading shaft 330 and the loading cap 332 are provided. It is mounted between the upper half 130 and the horizontal plate 162 for the counter balance.

In addition, four triaxial support pillars 140 are installed inside the pressure-resistant cylinder 110 to support the load applied to the bottom 120 and the upper half 130 during the side pressure action, in addition to the triaxial chamber ( In the test 100, the observation window 170 of the pressure-resistant structure for detecting the deformation state of the specimen S is installed.

The triaxial chamber 100 is filled with water during the test, the present invention uses a method of changing the restraining pressure applied to the side of the specimen (S) from pneumatic to hydraulic pressure. Here, the adjustment of the hydraulic pressure applied is kept constant by using the regulators (R), the restraint pressure may act up to 20kgf / ㎠. In addition, since the high-pressure air pressure generated by the compressor 210 contains water, the air filter F first removes water and then supplies water.

6 is a front view of a loading table forming a basic skeleton of the vertical loading device, Figure 7 is a plan view of the loading table, Figure 8 is a turntable structure diagram of the loading table.

The vertical loading device 300 is a device that applies a static load or a dynamic load (repetitive load) in the axial direction to the specimen is composed of an actuator 310, a piston 320, a loading shaft 330 and a load cell 501, etc. The actuator 310 has a swivel head, a high precision displacement gauge, an anti-eccentric compression plate, a servo valve, and a high precision load cell. The control and measurement of the actuator 310 is controlled by the electrical measurement and control program of the control device 500, the load cell 501 is a high-precision load measurement for precisely measuring the magnitude of the load applied to the actuator 310 As described above, the device is installed between the piston 320 and the loading shaft 330 of the actuator 310, and the present invention adopts a compression and tensile test.

As shown in FIG. 7, the actuator 310 is installed on a cradle 360 installed on the support 350 of the loading table 340. The hydraulic force generated in the external hydraulic generator 400 is controlled by the servo valve 410 so that the force applied downward from the actuator 310 is controlled by the load cell 501 outside the triaxial chamber 100 and the load cell inside the triaxial chamber 100. It is measured as 502. The control of the actuator 300 is all controlled on the computer 540, and the load and the amount of change of the actuator with time are recorded in real time by the programmed data acquisition system.

The present invention is also the base plate (340) of the base plate 340 to facilitate the setting to move the triaxial chamber 100, the specimen (S) is installed for the test toward the loading stage 340, the vertical loading device 300 is installed ( A moving rail 372 is installed on the moving rail 372, and a movable trolley 380 that is movable on the movable rail 372 is provided, and a turntable for changing the direction of the moving trolley is placed in the middle of the movable rail 372. 390 was installed.

The moving cart 380 is movable by the wheel 382 is pushed down on the rail 372 at the time of movement, and the wheel 382 is set on the bottom plate 370 of the loading stage 340. Since the bottom of the mobile truck 380 is grounded to the bottom plate 370 of the base 340, the stable setting and accurate test can be made.

This part will be described in detail. As shown in FIG. 8, wheels 382 are provided at the lower four corners of the mobile truck 380, and the wheels 382 are attached to one side of the mobile truck 380. When the drive motor 384 rotates in one direction by manipulating the switch box 383, the drive is installed in parallel with the rotational force on both sides of the upper portion of the moving cart 380 via the reducer 385 and the chain 386. The shaft 387 is rotated, and the drive shaft 387 is geared at right angles to the support shaft 388 of each wheel 382 by the worm and worm wheel methods, thereby lifting the wheel 382 and moving the bogie. The bottom surface of the 380 is grounded to the bottom plate 370 of the mounting table 340, and if the switch box 383 is operated in the opposite manner to the above, the lifted wheels 382 are lowered to ride on the rail 372. While the bottom of the moving cart 380 is from the bottom plate 370 of the loading stage 340 Is raised is such that the move is available.

In addition, on the rear side of the turn table 390, the position setting stopper 392 is transferred to the turn table 390 for setting of the triaxial chamber 100 so as to allow accurate position setting of the moving cart 380 in which the direction is changed. ) Is installed at the tip of the piston of the pneumatic cylinder (394), another switch box when moving to set the moving cart 380 with the specimen (S) and the triaxial chamber (100) to the vertical loading device (300) To operate the piston of the pneumatic cylinder 394 so that the stopper 392 protrudes toward the turntable 390 and pushes the moving cart 380 so that the rear end of the moving cart 380 touches the stopper 392. If it is no longer pushed, in this state by operating the switch box in the reverse of the above to retreat the stopper 392 and turn the turntable 390 90 ° to move the moving cart 380 under the vertical loading device 300 Let's do it.

On the other hand, the turn table 390 is operated by the drive motor (391), reducer (393) and the chain not shown in the forward and reverse rotation to 90 ° to facilitate the direction of the moving cart 380 with the stopper (392) It can be switched to the correct position, which saves the labor of the investigator and the time required for the test.

In the present invention, since the large specimen (S) is to be tested, the boom type crane 600 is installed at one side of the loading stand 340 for setting of the triaxial chamber 100, and the loading stand 340 has a lot of force downward. Since it is applied to the four pillars that can support a large force was used, the strut 350 is to be able to adjust the height of the actuator 310 installed in the holder 360 by placing a pitch 352.

In addition, the generation of air pressure is generated by the compressor 210, the compressed air generated in the compressor 210 is constantly regulated by the regulator (R) and then pressurized in the triaxial chamber 100 to the triaxial chamber 100 The air pressure is converted to hydraulic pressure by being applied to the filled water. The degassing of the degassing tank 514 and the negative pressure used for the specimen initial setting and the specimen saturation are generated by the vacuum pressure generator associated with the restraint pressure generator 200 and can act up to 10 kgf / cm ² .

The electrical measurement and control device 500 includes a plurality of sensors 501 to 508, an amplifier 520, an A / DD / A converter 530, and a computer 540, and the sensors 501 to 508 are strained. Gauge type or inductance type, two load cells for vertical load measurement (501,502) in one triaxial chamber, three LVDTs for vertical displacement measurement (503), one for restraint pressure measurement (506), one for pore water pressure measurement ( 507), two (504, 505) for volume change measurement, and a total of nine sensors of five kinds are installed.

The vertical load measuring sensor 502 is installed on the inside and outside of the triaxial chamber 100, and is capable of withstanding the water pressure acting in the triaxial chamber 100. The vertical displacement measuring sensor 503 is ± 100 mm. Equipped with a large size and a small size of ± 25mm, the external volumetric sensor 504 and the internal volumetric sensor 505 were used separately for the volume change measurement sensor (504, 505).

In addition, the amplifier 520 is composed of nine channels necessary for the basic test, but in order to increase the microdisplacement measurement or dynamic measurement items, a total of 16 channels can be used.

The control program of the computer 540 allows the output of the test conditions and test results of the large-scale compression tester to be performed by a computer operation. The control program is composed of static test and dynamic test, and the test conditions are set and tested. Control and measurement, storage of test data, summary analysis and output of test data.

FIG. 10 is a main screen of a control program according to the present invention, and it is possible to check real-time measurement status, measurement progress time, environment setting, and current status of each channel. FIG. 11 is a specimen evaluation screen. It is possible to calculate the wet unit volume weight, average height, volume, and cross-sectional area. Fig. 12 is a device setting screen, Fig. 13 is a B-coefficient measurement screen, Fig. 14 is a recording environment setting screen, Fig. 15 is an adjustment screen, Fig. 16 is a recording data review screen and Fig. 17 is a channel setting screen.

The control program of the present invention can set the storage time as a square value on the monitor and store the measured value for each channel, and check the saturation through real-time Skempton B coefficient measurement (saturation time, pore water pressure, side pressure reduction amount real time check), record data per channel It is possible to analyze the change trend by checking and graphing by time, and to check the adjustment of various sensors, offset value adjustment, and instrument status.

Hereinafter will be described the process and method for testing the characteristics of the specimen using a large triaxial tester of the present invention.

18 is a flowchart illustrating a process of a large triaxial compression test according to the present invention.

Large triaxial test specimens can be divided into Buddhism eggs and disturbance samples. Buddhism eggs of the assembled material can be tested after freezing by melting them in the laboratory.In case of disturbance samples, a separate compaction device is used. It is manufactured by compacting it to the required density by impact or vibration compaction. Hereinafter, the case of testing the disturbance sample in the tester of the present invention will be described.

[Setting of specimen]

After collecting the collected sample in the compaction mold (M) and transported the specimen (S) to the triaxial chamber (100) using a lift (Lift) as a transporting tool, and then the base of the triaxial chamber ( Position the specimen S using the position tracking pin 152 protruded to 150. (See FIG. 19).

A negative pressure large enough to allow the specimen S to stand on itself is applied to the specimen S using a vacuum pressure generator, and the compaction mold M is removed.

[Setting of sensor]

An actuator control program is executed on the computer 540, and a data logger program is executed.

The pore water pressure sensor 507 assembles the triaxial chamber 100, fills it with degassed water, removes the air present in the drainage pipe, and then operates the regulator R to change the magnitude of the changed pressure using a precision pressure gauge. According to the change of the detected voltage to the PC according to the adjustment of the pore water pressure sensor 507.

The differential pressure sensors 504 and 505 for measuring the volume change supply degassed water to the double tube burettes 510 and 511, and then drain the water in the internal burettes of the double tube burettes 510 and 511, thereby internally and externally. The differential pressure sensors 504 and 505 are adjusted by recording and inputting the voltage change detected by the computer according to the difference in the volume change of the controller.

The vertical displacement measuring sensor 503 is installed at the stage of consolidation, and records and inputs the change in voltage detected by the computer 540 according to the difference of displacement using a tool capable of precisely adjusting displacement. The adjustment at 503 is executed.

Load cells 501 and 502 for vertical load measurement execute an actuator control program, place dummy elements in the triaxial chamber 100, and place elastic plates under the load cells 501 and 502 to correct the output values detected by the load cells 501 and 502 according to control signals. To perform the adjustment.

[Installation of various sensors]

The pore water pressure sensor 507 is provided below the operation panel of the moving trolley 380. The pore water pressure sensor 507 can calculate the side pressure, the pore water pressure at the bottom of the specimen, and the pore water pressure at the top of the specimen, respectively.

The differential pressure sensors 504 and 505 for measuring the volume change are installed under the double tube burettes 510 and 511, and the pipes coming from the inside and the outside of the double tube burettes 510 and 511 are connected to the differential pressure sensors 504 and 505 for volume change measurement, respectively. Record the water level change (or volume change) in 510,511.

The vertical displacement measuring sensor 503 is assembled by using the triaxial chamber 100, and then using the connecting device installed in the upper shaft 130 of the lower shaft 330 and the triaxial chamber 100.

The external load cell 501 is directly connected to the loading shaft 330 of the actuator 310, and the internal load cell 502 is connected to the loading cap 332 inside the triaxial chamber 100.

[Assembly of triaxial thread]

1. Combine the four pillars 140 in the triaxial chamber 100, using the boom crane 600 to lift the upper half 130 and fasten.

2. Insert the loading shaft 330 into the triaxial chamber 100 and fix it using the loading shaft stopper.

3. Combine the inner load cell 502 or the loading cap connecting device under the loading shaft 330.

4. Inject air pressure into the counter balance and engage the balance plate.

5. Loosen the loading shaft stopper and gently lower the loading shaft (330) by hand, then combine the loading cap and loading cap connection device.

6. Secure the loading shaft stopper, relieve counter balance air pressure, and remove the balance plate and loading shaft coupling.

7. Reintroduce air pressure to the count balance, engage the balance plate and loading shaft connector, and loosen the loading shaft stopper.

8. Cover the chamber with the crane.

9. Fasten the chamber stopper.

[Consolidation process]

1. Assemble the triaxial chamber 100 and inject water.

2. Check and adjust the origin of the vertical displacement sensor 503 and the differential pressure sensor 504,505.

3. Set valve V1 on the operation panel of FIG. 9 to the side pressure and keep valve V2 downward. The valve V5 is set at the specimen setting and the valves V6 to V14 are set to closed. The negative pressure inside the specimen S is reduced by applying a cell pressure equal to the negative pressure applied to free the specimen S.

4. After increasing the isotropic pressure to the predetermined consolidation pressure by one of the following methods, the valve V5 is changed to closed. If the saturation process is necessary, the saturation of the specimen S is performed and the consolidation step is performed according to the following procedure. Change.

-Increase the pressure as a standard with a speed of 0.5 kg / cm 2 / min. Volume change and axial compression amount are measured at intervals of 0.5 kg / cm 2 or less of pressure increase.

-It is standard that the stress of the next stage is set to be twice the stress of the current stage, and the volumetric compression and axial compression are measured at intervals within 1 minute until the consolidation of each stage is increased.

After the side pressure is kept at a predetermined value, the valve V6 is operated internally, the valve V7 is operated simultaneously with a differential pressure gauge, the valve V8 is operated externally and the valve V9 is operated simultaneously with a differential pressure gauge.

5. After the completion of consolidation, calculate the volume and volume compression from the time of specimen preparation to the end of consolidation.

[Shear process]

1. Check and adjust the origin of the vertical load sensors 501 and 502, the vertical displacement sensor 503 and the internal and external differential pressure sensors 504 and 505.

2. Compress the specimen (S) continuously so that the cell pressure is constant and the strain rate is constant.

3. When compressing, measure the axial compression force, axial compression amount and volume change.

4. Continue compressing until the reading of the vertical load sensor decreases from about two thirds of its maximum. However, if the axial strain reaches 15%, the compression is terminated.

5. Observe and record the deformation and destruction of specimen (S).

Hereinafter, the process and the results of the actual test of several assembly materials in a static or dynamic test state using the tester of the present invention will be described.

[Test Example 1]

Test sample; Sambo, Buil, and Heungnam are the basalt sandstones of Jeju Island. Maximum particle diameter of the sample = 50.8 mm, uniformity factor U _C = 1.6 to 1.9, dry unit weight 1.383 t / m 3 to 1.485 t / m 3.

Test plan; Nine cylindrical specimens (300 mm in diameter and 620 mm in height) are subjected to the drainage shear test (CD) at speeds of 3 mm / min under three restraint pressures of 1.0, 2.0 and 3.0 kg / cm2.

Molding and setting method of specimen; In this sample, the specimen was molded in the following way to reproduce the conditions similar to the construction of breakwater by dumping the building material in seawater.

Molding of specimens

1) The test sample was immersed in seawater for about 72 hours before the specimen was manufactured to meet the field conditions.

2) Insert two latex membranes (1mm or 2mm thick) into the pedestal (bottom pedestal), which is the bottom of the mold, and then connect by connecting the steel band.

3) The two-part mold was assembled, the membrane was lifted up and folded out of the mold, and vacuum pressure was applied through the air hole so that the membrane adhered to the inner surface of the mold.

4) Put an acrylic plate on top of the pedestal which is the bottom of the mold and put the filter paper.

5) After inserting the sample by hand, accurately measure and record the weight of the inserted sample.

6) Measure and record the water content of the remaining sample.

7) Fill the sample to the top of the mold, put the filter paper and put the acrylic plate.

8) Put the upper cap on the acrylic plate, release the membrane over the mold, put the upper cap on it and connect it using the steel band.

Setting of specimen

1) Transfer the completed mold to the stacker and place it on the trolley.

2) Connect the drain pipe to the upper cap.

3) After connecting the vacuum tube to the valve panel in front of the moving cart, apply a vacuum pressure of about 0.2kg / ㎠ to the specimen so that the specimen can stand on itself when dismantling the mold.

4) After dismantling the mold, measure the circumferential length of the specimen by dividing the height of the specimen into four equal parts and measuring the height of the specimen at four points in the diagonal direction.

5) Assemble the cover plate of the pillar and the triaxial thread and put the triaxial thread.

6) Supply tap water until the upper cap of the specimen is locked inside the triaxial chamber and seal the triaxial chamber completely (at this time, the space between the upper cap and the bottom of the cover plate is filled with air).

7) A side pressure of 0.2kg / cm 2 is applied to prevent inadequate deformation of the sample before removing the vacuum inside the sample.

Saturation of specimens

In order to reproduce the conditions similar to the construction of breakwater by dumping the building material into seawater, the sample was completely saturated by passing water from the lower part of the specimen to the upper part using natural water head for 24 hours after completion of the specimen setting.

Triaxial compression test;

Consolidation drainage shear test (CD) was carried out on nine saturated cylindrical specimens with varying restraint pressures of 1.0, 2.0 and 3.0 kg / cm 2 for each sample.

The isotropic consolidation pressure is applied to the specimen by applying a predetermined pneumatic pressure to the space above the triaxial chamber, and the consolidation pressure is measured by a high precision pore water pressure sensor. The volume change of the sample is measured by a double tube burette for internal volume measurement and a differential pressure sensor. At this time, the consolidation time was averaged about 20 minutes for each load stage. The axle is controlled by hydraulic servo system and applied at a speed of 3mm / min.

Test result;

The internal friction angle can be obtained by constructing the Mohr circle for three restraint pressures and the least square method in the graph of the relationship between the sequential stress and the restraint pressure during breakdown (Fig. 20). Almost the same value.

The internal friction angle and adhesive force by the least square method were calculated using the following equation.

The internal friction angle when the adhesive force component was zero was calculated using the following formula.

The following table summarizes the test results in this test example.

The internal friction angle was 33.1 ~ 35.3˚ for the large triaxial test on the sandstone material (Jeju Basalt Sambo, Buil and Heungnam samples) used in this test example. Adhesion was 0.46 ~ 0.94 kg / ㎠. The compaction properties showed a minimum dry unit weight of 1.27t / ㎥ and a maximum dry unit weight of 1.76t / ㎥, and the relative density values of 29.3 ~ 52.0% for specimens prepared under non-compacting conditions. The volume change for isotropic consolidation gradually increased as the restraint pressure increased, and the volume decreased to about 3.01 ~ 3.22% of the total volume before consolidation at the restraint pressure 3.0kg / ㎠. In addition, in the stress-strain relationship, most of the samples except for some of the samples showed the peak strength was not clear and exhibited plastic behavior. As the restraint pressure increased, the volume strain increased. In the case of the modulus of elasticity, E ₅₀ was found to be 222 ~ 244kg / ㎠ (Sambo sample), 146 ~ 169kg / ㎠ (supplemental sample) and 141 ~ 210kg / ㎠ (Hungnam sample), the E ₅₀ is different for each material It can be seen that due to the material properties.

[Test Example 2]

Test sample; Seoul Metropolitan Subway Section 912

Test plan; Estimation of Shear Strength Constant (Internal Friction Angle and Adhesion) of Test Sample and Dynamic Strain Characteristics (Relationship between Shear Modulus, Shear Strain and Damping Constant) by Mohr Source and Repeated Loading Test

Fabrication of specimens;

A specimen of diameter 304mm and height 620mm was fabricated using a large automatic compactor weighing 16kg in drop and 50cm in diameter.

Triaxial compression test;

The test was conducted under consolidation drainage conditions and sheared at a rate of 3 mm / min until the maximum axial strain was 20%. Restraint stresses were tested varying between 1.0, 3.0 and 5.0 kg / cm 2.

Test result ;

Internal friction angle and cohesion; The results of the large triaxial test for the three restraint pressure conditions are shown in the table below, and the internal friction angle and the cohesion were calculated using the sequential stress-resistance stress at break and Mohr original drawing method.

In the relationship graph between the sequential stress and the restraint pressure at break (FIG. 21), the internal friction angle and the adhesive force were determined using the same formula as in Test Example 1.

Internal friction angle = 21.3˚ and adhesive force = 0.31kg / ㎠ in both the method using the sequential stress-restraint relationship and the method using the Mohr original drawing method.

Stress-strain relationship; The stress-strain relationship of this sample is shown in FIG. The peak strengths do not appear clearly for the restraint pressures 1.0, 3.0 and 5.0 kg / cm 2, because the material is relatively loose and contains a lot of fine grains.

Vibration triaxial test (repeated triaxial test; dynamic test)

The repeat load test process is as follows.

(1) Prepare specimens in the same way as in the static test and complete the assembly of specimens and triaxial chambers on the loading stage of large vibration triaxial tester.

(2) Saturate and consolidate the specimens under a predetermined constraint pressure. (This sample did not carry out a separate saturation process because the groundwater level of the original ground was lower than the sampling depth. )

(3) a consolidated loading of 1 times under a certain confining pressure was repeated Half amplitude of rotor stress calculated by the following equation: _d б to the sinusoidal 0.2Hz repeated for the complete sample.

In this test, the uniaxial amplitude of cyclic sequential stress was divided into five stages for one restraint pressure, and the magnitude of cyclic axial load was measured by using a high precision load gauge (load cell).

(4) Single amplitude amplitude strain ε _SA (%) is calculated by the following equation.

(5) Equivalent modulus of elasticity E _eq and equivalent shear modulus of elasticity G _eq are obtained by the following equation.

(6) Shear strain is to be obtained from the following formula.

(7) The hysteresis damping constant h (%) is obtained by the following equation. In this test, the 10th of 11 hysteresis curves were selected and used to calculate the attenuation constants (see Figs. 23, 24 and 25).

As a result of repeated loading test under the restraint pressure 1.0, 3.0 and 5.0kg / cm2, the shear modulus of elasticity G is 600 ~ 1,380kg / cm2, and the damping constant h is 0.02 ~ 0.16 in the range of shear strain r = 10 ^-4 ~ 10 ^-3 . As the restraint pressure increases, the shear modulus increases.

However, using the Hardin-Drenevich's model, the maximum shear modulus of elasticity G _max and the maximum value of attenuation constant h _max are obtained from the test results. For this sample, G _max = 770 ~ 1,660kg / ㎠, h _max = It is estimated to be 25-56%.

As described above, the large triaxial compression tester according to the present invention is capable of dynamic testing of specimens having a diameter of 300 mm and a height of 620 mm under static test conditions as well as cyclic loads, so that the shear strength and stress-strain characteristics of the assembly material for dam construction It is possible to estimate the design parameters for the design of port facilities such as breakwaters and quay walls, to grasp the dynamic characteristics of railway ballast materials, or to measure the shear strength of the assembly materials for road construction. It is possible to understand the shear strength and stress-strain characteristics of the assembly materials for civil engineering structures such as stone and crushed stone, and to conduct large vibration triaxial tests and static triaxial tests of other soil materials. In particular, the input parameters required for the design, construction, and behavior analysis of the dam under the applicant's jurisdiction can be accurately obtained, and the seismic analysis of the dam body can be easily performed using the input properties obtained through dynamic tests. It has the effect of obtaining data that enables stability assessment and economic dam section design.

Claims (12)

Triaxial chamber 100 is installed specimen (S) therein; A restraining pressure generating device 200 for applying an isotropic pressure converted from pneumatic to hydraulic pressure to the specimen S installed in the triaxial chamber 100; Vertical loading device 300 for applying a compressive force perpendicular to the specimen (S) installed in the triaxial chamber (100); A hydraulic generating device 400 for operating the vertical loading device 300; According to the operation of the vertical loading device 300, the vertical load and the vertical displacement, the restraint pressure, the pore water pressure and the volume change applied to the specimen S installed in the triaxial chamber 100 are measured, and the triaxial chamber 100 and the vertical An electrical measurement and control device 500 for controlling the loading device 300 according to the test conditions; large vibration triaxial tester comprising a. The method according to claim 1, Two load cells 501 and 502 are used as a means for measuring the vertical load on the specimen, each of which is between the piston 320 and the loading shaft 330 of the actuator 310 constituting the vertical loading device 300, and Large vibration triaxial tester, characterized in that installed between the lower end of the loading axis 330 extending into the triaxial chamber 100 and the specimen (S). The method according to claim 1, The triaxial chamber 100 includes a pressure-resistant cylinder 110 and the bottom plate 120 and the upper half 130, the triaxial chamber support 140, between the pressure-resistant cylinder 110 and the low, upper half (120, 130) -It is closed by the ring, the upper half 130 is a large vibration, characterized in that the bearing portion 132 is mounted in the center so that the loading axis 330 of the vertical loading device 300 can move up and down without friction Triaxial testing machine. The method according to claim 3, The triaxial chamber support 140 is a large vibration triaxial tester, characterized in that four are installed in the inner pressure cylinder 110 to support the load applied to the bottom plate 120 and the upper half 130 during the side pressure action The method according to claim 3, The triaxial chamber 100 is a large vibration triaxial tester, characterized in that the observation window 170 of the internal pressure structure for determining the deformation state of the specimen (S) during the test is installed. The method according to claim 1, The vertical loading device 300 is characterized in that it has an actuator 310 controlled by the servo valve 410 to selectively apply the static load and the dynamic load (repetitive load) in the axial direction to the specimen (S) Vibration Triaxial Tester. The method according to claim 1, The vertical loading device 300 has a moving rail 372 is installed on the bottom plate 370 of the loading table 340, the moving cart 380 is installed on the moving rail 372, the moving rail ( 372) a large vibration triaxial tester, characterized in that the turntable 390 for changing the direction of the moving cart 380 is installed. The method according to claim 7, The moving cart 380 is movable when the wheel 382 is lowered on the rail 372 when moving, and when the wheel 382 is set on the bottom plate 370 of the loading stand 340. Large vibration triaxial tester, characterized in that the bottom of the 380 is grounded to the bottom plate 370 of the loading table (340). The method according to claim 8, The wheels 382 installed at the lower four corners of the mobile trolley 380 have the rotational force generated by the driving motor 384 horizontally on both sides of the upper side of the mobile trolley 380 via the reducer 385 and the chain 386. A large vibration triaxial tester, characterized in that for raising and lowering the support shaft 388 of each wheel 382 by rotating the drive shaft (387) installed in parallel. The method according to claim 7, On the rear side of the turn table 380, a position setting stopper 392 is provided to enable accurate position setting of the moving cart 380 which is transferred to the turn table 390 to change the direction for setting of the triaxial chamber 100. Large vibration triaxial tester, characterized in that installed in the piston tip of the pneumatic cylinder (394). The method according to claim 7, Large scale vibration triaxial tester, characterized in that the crane 600 for setting of the triaxial chamber 100 is installed on one side of the loading stage 340. The method according to claim 7, The loading stage 340 is formed of four props, each support 350 is formed with a pitch 352 to form a screw-coupled state with the cradle 360, the lifting operation of the cradle 360 Large vibration triaxial tester, characterized in that by the height adjustment of the actuator 310 is enabled.