Response of dry sand under lateral impact loading

• Main Author: Chua, Shengjie.
• Other Authors: Budi Wibawa
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering; DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/15868
• Institution: Nanyang Technological University

Singapore’s land area is 20% made up of reclaimed land and the figure is likely to rise in the near future. Even though there is no earthquake threat in the history of Singapore, tremors can still be felt when a strong earthquake occurs in Indonesia. As the reclaimed land is prone to liquefaction due to earthquake, it is necessary to study whether the reclaimed land is strong enough to withstand the shocks. The experiment conducted is meant to determine the effect of lateral impact loading on a model of dry sand as an initial study. Soil classification will first be conducted to see whether the sand is suitable for the project. The actual experiment involves swinging a pendulum with weights of 0.321kg, 0.476kg and 0.673kg from angles of 10 degrees, 15 degrees and 20 degrees from the vertical axis. The pendulum will hit a knob which acts as an impact loading on the sand model. Accelerometers attached to an oscilloscope are used to capture the data once the vibration starts. The accelerometers are at 63mm(Channel 1), 158mm(Channel 2) and 263mm(Channel 3) from the bottom of the sand model. The data are then stored and further analyzed using a computer. The data will be processed into acceleration with respect to time. Velocity and displacement can be obtained by integrating the acceleration using trapezoidal method. After looking at the profiles, it has been deduced that the acceleration, velocity and displacement are highest at 263mm elevation, since this elevation is the furthest from the level of loadings. The second highest values are at 158mm elevation, followed by 63mm elevation. Also, the readings are the highest for tests done when the pendulum was swung from 20 degrees, and also when the impact energy used is 0.132Nm. For acceleration, velocity and displacement at all elevations, the peaks of the waves decrease with time due to damping. Damping was found out to be constant at all elevations. The sand model behaved as an under-damped system. With a damping ratio of 0.752, the method of logarithmic decrement is less accurate for this experiment.