Cubical Triaxial Cell

Recently, a new addition of triaxial test apparatus was made by fabricating two cubical triaxial cell to conduct various triaxial cell. These apparatus were fabricated by the technical staff of UTAR machine shop, and the details are given as follows;

FYP Students Completing Their Experiments

Three teams of FYP students are working hard to complete their experiments before start writing final FYP reports. Three teams, namely Standard Triaxial Team, Shaking Table Team and Cyclic Triaxial Test Teams, are nearly completing their experiments as shown below. They have a common task of finding out the deformation and strength properties of residual soil. Although they have taken undisturbed samples from field, due to the time constrain only the tests on compacted soil with the same densities in the field are to be completed.

1) Standard Triaxial Team; Examining the effective stress paths during undrained shear

2) Shaking Table Test Team; Examining the shear modulus through shaking table test

3) Cyclic Triaxial Test Team; Examining the small strain behavior of compacted residual soil

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Field In-Situ Density Test versus Lab Compaction Test

This week, five FYP students with their supervisor have carried out field in-situ density test at the same site (Site A & B) as previously reported. This was to examine the field dry density of residual soil, while the laboratory compaction tests on these two soils have been carried out at UTAR Civil Eng. laboratory. A water filled balloon (plastic bag) was used to measure the volume of soil that was dugout from the ground, and the soil dugout from a hole (approximately 12cm dia x 10-15cm deep) was carefully collected for weight and water content measurements at laboratory as shown in photos.

A comparison between field dry densities and laboratory proctor compaction test results are shown in the figure. Based on these results, the field dry densities at Site A and Site B can be defined as approximately 1.6 tf/m3 and 1.5 tf/m3 respectively. The rain fall in the previous day of site investigation has made the ground fairy wet, so that the water contents were high at these site, ranging from 18 to 22%. One of field data (first trial test of in-situ density tests) from Site B shows a value above the zero air void curve and therefore this should be disregarded.

FYP students will carry out a series of triaxial test to study the deformation properties of residual soil in small strain range by using both undisturbed and compacted samples. Also shaking table test and hollow cylinder test are planned to study the deformation properties of residual soil in small strain range by using compacted sample.

For further information on FYP studies, please contact us at utar.earthquake@gmail.com.

Comparison of field density test data with laboratory compaction curves

Shaking Table Started to Operate

This week, the operation of shaking table has started successfully. The shaking table is operated by sending a digital command to the controller of mega-torque motor. Both regular and irregular shaking is possible by using a program on laptop computer written in Visual Basic. This program is written by Dr. Lohani of GEO. institute of Japan. Because some response limitation of the mega-torque motor, the shaking is possible within a limit that is combination of frequency and shaking displacement.

The next task of FYP team is to find out these limits and calibrate the shaking intensities that can be applied by this apparatus. As these apparatus have been assembled entirely by the technical staff of UTA (FES/Civil), the maintenance and further developments of such apparatus would be possible.

If there is any interest on this apparatus, please write to utar.earthquake@gmail.com

Undisturbed Soil Sampling on Residual Soil

FYP students worked together with their supervisor to take undisturbed sample of residual soil (so called Kenny Hill formation) at a site near Shah Alam, west of Kuala Lumpur. There was a slight difference in the texture of residual soil at the site only few meters away. One site (A) was very silty without any trace of coarse particles, while the other site (B) shows a slight inclusion of fragmented weathered coarse particles.

Undisturbed samples of 15cm x 15cm x 25cm were successfully taken by using a sort of soil nailing technique for this sampling. A wooden plate 15cm x 15cm was placed at the surface of residual soil ground, and 12 steel bars of 6mm diameter were nailed into the ground at the perimeter of the plate. Then the soil surrounding was excavated by hand shoveling. After the soil block was removed from the ground, the block was reversed in vertical position while attaching the wooden plate and then a thin layer of plaster was applied to secure the soil block from falling apart and drying during the transportation.

In addition to undisturbed samples, disturbed residual soils were taken to carry out further laboratory test, including physical property tests and triaxial strength test on compacted specimen.

The pictures below show the undisturbed sampling at the site.

 excavating undisturbed sample that surrounded by soil nails

 plastering sample for Site B

Views of Site A

Triaxial Test Apparatus Nearly Ready for Standard CD & CU Tests

Pressure supply & control system for triaxial test apparatus has been completed and also calibrations for load cell, LVDT for deformation measurement, and pressure sensor for pore water pressure measurement are completed. Thus FYP students are ready to perform standard triaxial tests on compacted residual soil, although final checking of pressure tube fittings and measurement system needs to be carried out by actually pressurizing and consolidating a soil specimen in the triaxial cell.

At the moment, a data logger which is not connected to computer is used to take all measurements. However, a system of computer controlled measurements and pressure changes using D/P air regulator needs to be introduced to perform more sophisticated triaxial tests such as a cyclic undrained triaxial test.

The picture below shows a control system and loading frame for standard triaxial test that was built solely by FYP student and technical staff of FES laboratory.

Should you be interested in these apparatus, please send your mail to utar.earthquake@gmail.com

Shaking Table Assembly Near Complete

Assembly of the Shaking table is nearly completed by attaching the driving megatorque motor next to the shaking table concrete base. The motor provides horizontal thrusts on shaking table. A new concrete base for the motor was built by FYP students, and the motor was placed on this new base to an exact height, in order to connect the motor driving shaft to the end of shaking table. As the shaking table is air-lifted, the horizontal thrust from the motor will provide ample energy to shake any objects horizontally on the table.

The power of shaking thrust will be examined next by first controlling the megatorque motor rotation, and a digital control system for the motor needs to be thoroughly checked. Also actual acceleration and frequency that can be achieved by the shaking table need to be measured by placing accelerometers on the table.

When the set-up of shaking table test apparatus is completed, the apparatus will be used to first determine the dynamic properties of residual soil. This apparatus has been used successfully to examine various dynamic responses of model ground at RCUSS, Kobe University, Japan and especially of examining the liquefaction problems as shown below.

If you are interested in these facilities, please contact us at utar.earthquake@gmail.com.