Department of Civil and Environmental Engineering- Rock lab
CE-Rock lab

Clear images and colors  | Post date: 2020/01/11 | 
Rock Mechanics Laboratory
Head: Prof. Ahmad Fahimifar

Technician: Dr. Davood Akbarimehr

Telephone: +98(21)64543082
Address: Rock Mechanics Laboratory, Negative Second Floor, Building No. 2, Department of Civil and Environmental Engineering, Amirkabir University of Technology, Hafez Ave., Tehran, Iran


Department of Civil & Environmental Engineering Amirabir University of Technology Rock Mechanics Laboratory, with its laboratory facilities, is prioritizing research and training programs. In this regard, Graduate studies in this unit have been defined and carried out to enable the study of new theories in rock mechanics.
This report describes the facilities and equipment are provided and built in the lab, and finally points to the activities and prospects ahead.
Laboratory equipment

Servo Control Device  
The Dartec-9600 Servo control device is used to perform a variety of static and dynamic compressive and tensile tests. The device is one of a number of servo control devices that allow control of the loading during the test by the computer so that data can be automatically recorded during the tests. This data can be captured by the settings available on the device at the desired intervals.
This device's data are force and displacement and are measured by upper movable maxillary sensors (fixed mandibular). This machine consists of the following parts:
  1. Hydraulic power supply unit for tests
  2. Device Loading frame
  3. Computer-related parts and device transducers
Hydraulic power supply unit
This part must be activated to apply the force to the specimen during the tests to provide the required hydraulic force. The hydraulic power supply unit has a very strong pump motor which has the following specifications:
Motor weight: 120 kg
Engine speed: 1740 rpm
Motor power: 21.3 kW
Generally, the hydraulic power supply unit includes the following components:

A. Thermostatic water valve
If the temperature of the machine's hydraulic oil exceeds the allowable limit during the test, the valve will open automatically and keep the water flowing in the system, thereby cooling the oil and continuing the test.
To prevent excessive water consumption, a spring is installed next to the device where the water flowing into the system is pumped into the system and the same water is re-entered to cool the oil.
B. Pump
The performance of the pump is such that it provides the force needed to circulate the hydraulic oil in the system. This engine has a maximum engine capacity of 100 liters per minute of hydraulic oil in the system.

C. Pressure Supply Unit Required to Start Examine
 This section has a valve which operates to reach the desired level of oil for the start of the test.

D. Automatic valve to provide the required hydraulic force during the test
The valve functions in such a way that it provides the hydraulic force required during the test, meaning it automatically opens the valve to provide more hydraulic force to allow the test to continue.

E. Thermostat
That is used to detect the temperature of the rotating oil during the test. If we set the thermostat to a certain temperature, if the circulating oil temperature exceeds this value, the servo control system will open the thermostatic valve further to open the oil temperature, thereby giving more water to the system. Flows through and provides cooling of the hydraulic oil.

F. The cooler system of the pump motor of the machine
That used for cooling the hydraulic oil is of type IPH4 / 32, capable of circulating 50 liters per minute of water in the system. The pump's power is about 3 horsepower.

G. Hydraulic oil of the machine
Shell Tellus 37 oil, which is compatible with the function of the device filters, is used to provide hydraulic power.

H. The filter of the hydraulic power supply unit
The pre-valve device has a series of filters, which are used to determine the oil pollution index in the system. These filters can be replaced. If the oil acidity exceeds 0.5 mg Ko H / g, the hydraulic oil used in the system must be replaced. To determine the acidity of the oil, the oil should be tested every 6 months by acidic acid tests.

Device Loading frame
The device has two rigid beams, one at the top of the device loading frame that can move up and down, and thus the load can be tensed or compressed into the specimen. The beam contains sensors that transmit test information that are force and displacement to the device transducer. The other transverse beam is located at the bottom of the loading frame and plays a major role as a support for the test specimens.
The loading frame is capable of compressive load up to 100 tonnes and tensile load up to 120 tonnes, and the load can be applied at a rate of 0.001 mm / s to the specimen. The required hydraulic force to move the transverse beam at the top of the loading frame to upside or downside to supply force to the rock specimens is provided by a series of hoses attached to the back of the frame. One of the features of this device is the ability to replace jaws. This feature enables the device to perform various tests. Different jaws should be used for different types of pressure, tension or bending tests. The following is a description of the jaws required for various tests.

A. Three-point bending test jaws
Cylindrical jaws can be used for this test. Through the upper jaw the required pressure is applied to the rock samples and the two lower cylinders play the support.
B. Four-point bending test jaws
This test can also be used for cylindrical jaws similar to the three-point bending test jaws. Because there is only one cylindrical jaw in the device, double cylindrical jaws are designed and applied in the laboratory for compressive load.

C. Uniaxial, triaxial and Brazilian pressure test jaws
For tests such as uniaxial, triaxial, and Brazilian, which are essentially compressive tests, the device should use compression jaws. These jaws consist of two discs with a diameter of 30 cm and a thickness of 4 cm that lie on two rectangular plates with a length of 75 cm and a width of 30 cm and a thickness of 6 cm. These rectangular plates are also attached to the upper and lower transverse beams of the device.
D. Direct Tensile Test Jaws
Since direct tensile testing has been performed in a limited number of countries, the device has no tensile loading jaws. As a result, jaws were designed and manufactured for direct traction testing in the lab.
These jaws have two rectangular steel straps that have two holes 14 mm in diameter at their ends. Through two screws these two straps are connected to circular plates, which are attached to the beams of the device. These straps are attached to the conical plates at the other end. Cylindrical rock samples are adhered to the circular warheads on both sides with the help of adhesive, and the warheads are attached to the above and below the device by means of screws on the above-mentioned conical plates.

Point Load Testing Device
This device includes the loading system, jaws, the load measuring device and the displacement measuring device between the two jaws, which describe each of the following:
A. The loading system
The system includes a loading jack with adjustable jaws that allow for testing on rock samples of various dimensions. This range is between 30 and 80 mm and therefore the jaws are adjustable for small and large specimens. These two jaws have a conical angle of 60 degrees and a curvature radius of 5 mm. These jaws are made of hard steel so they will not be damaged during testing. The upper jaw is fixed and the lower jaw is movable.

B. Load measurement system
Includes a pressure gauge to measure the load at the moment of fracture. Since breakdowns often occur suddenly there is a maximum load gauge required to record the load at this time.

C. Displacement Measurement System:
The device is equipped with a ruler to measure the distance between the jaws.
Direct Shear Testing Device
This device includes
A. Cutting Box: The sample is inserted into it.
B. Vertical load device: Applying the load uniformly to the test plane so that it is completely perpendicular to the center of the surface and above it.
C. Shear Load Apparatus: Apply the shear load uniformly to one half of the specimen.
D. Vertical and shear forces independent measurement equipment- Vertical and shear displacements independent measurement equipment
Creep Testing Machine
This device includes the following parts:

A. Loading device: which the required test load into the sample within 20 seconds and keeps it constant during the test.

B. Triaxial chamber: A chamber in which the sample is subjected to lateral pressure and axial load. The chamber is equipped with safety valves, an inlet for filling the chamber, rubber tubes, gages and other valves.

C. Flexible membrane: This membrane includes a sample of rock and metal plates in above and below it to prevent penetration of the confining fluid into the sample.

D. Apply and fix lateral pressure: This system is capable of producing the lateral pressure required by the test and keeping it constant during the test.

E. Confining fluid

F. Steel Plates: Two disc-shaped steel plates located above and below the specimen to apply axial load to the specimen.

G. Strain gauge: for measuring strain or axial deformation
Durability Testing Device
This device includes the following parts:

A. A reticulated cylindrical container made of 2mm wire mesh. The cylinder length is 100 mm and its diameter is 140 mm.
B. Water pan that way includes a cylindrical container attached to a rotating horizontal axis. When the pan is filled with water, the distance between the surface of the water and the axis of the cylindrical container is 20 mm. The depth of the pan is about 40 mm from the bottom of the cylindrical container.
C. A moving motor that rotates a lattice cylinder at a speed of 20 rpm.
Its main body is made of steel and furnace color and its inner body is made of aluminum trays. It has a capacity of 250 liters and is capable of producing and maintaining a temperature of 200 degrees Celsius and is equipped with a circulation fan.
Digital scales
Includes two digital scales, one with an accuracy of 0.1 g and a capacity of 6 kg and the other with an accuracy of 5 g to a maximum weight of 15 kg and an accuracy of 10 g to a weight of between 15 and 30 kg.

Strain gauges are used to measure axial and lateral deformations or strains of two strain gauges. The accuracy of these strain gauges is 0.0025 mm.
In addition to the aforementioned devices, other equipment is available in the laboratory including stone cutting machine, coring machine, lateral compressor, triaxial cells of 110 * 54 and 75 * 150 mm.
Stone cutting machine
Core machine for making rock samples
Lateral compressor

Outlook of Leading Activities

A. Dynamic testing with the servo-control device
The servo-control unit also has dynamic loading capability. In order to set up the device and apply this capability in studying the dynamic behavior of rocks, dynamic experiments on rock samples are on the agenda.

 B. Providing the necessary tools for the outline of the stone
Microscopic study of rocks is very important in rock engineering. The texture and the way minerals are placed together, the percentage of specific minerals in the rock, the dimensions of the minerals, the degree of weathering or alteration, and the distribution of fine-grained minerals are parameters that control the engineering behavior of the rocks, thus equipping the laboratory with stone anatomical devices. The agenda is here.

 C. Providing LVDT and Data Log Sensors
In order to increase the accuracy of measurement as well as to accurately record lateral and axial strains or deformations, instead of using handheld gauges and readout notes, it is advisable to use a data logger by capable of preserving all input information to the system from LVDT sensors.

D. Supply of ultrasonic device
Since the use of dynamic methods for accurate and rapid estimation of elastic constants in rock engineering is widely accepted today, and due to the non-destructive nature of these experiments, the development of ultrasonic apparatus for measuring sound speed and dynamic elastic constants is considered.

E. Provision of equipment for field tests
Despite the high importance of laboratory tests and their necessity in engineering operations, the results of these tests are not suitable values ​​due to the fundamental difference between the rock mass and pristine rock mass and cannot be used to accurately explain rock mass behavior and its performance analysis, therefore Field tests or rock masses have a special place in rock engineering. Therefore, the equipment necessary for field rock tests to achieve a comprehensive analysis of rock behavior has been included in the programs of the Rock Mechanics Laboratory.
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