Saturday Night Shake Down: Earthquakes and Soil Stability

Overview

Objectives/Goals The objective of my project was to find what soil (cat litter, dirt, sand) protected Lego towers the best against earthquakes on a shake table with varying voltage, building size and shape, and soils. Methods/Materials I built a shake table in which I placed three different soils (cat litter, dirt, and sand) and connected the shake table to a motor that spun a counterweight to simulate an earthquake. Cat litter was used as a substitute for unconsolidated gravel. I placed Lego towers with base to height ratios that ranged from 1.6 to 20 on the shake table, three at a time. Then I ran the shake table at 1.5 V and 3 V for 20 seconds and recorded the movement of the Lego towers and the time to fall of each tower. I repeated each experiment 4 times for a total of 120 trials. Results The cat litter was definitely the least stable. However dirt and sand had mixed results. The average time to fall for a 1.5 V earthquake was 19.3 seconds for cat litter, 25.5 seconds for dirt and 26.9 seconds for sand. The average time to fall for a 3 V earthquake was 9.9 seconds for cat litter, 15.1 seconds for dirt and 19.5 seconds for sand. Sand kept the Lego towers from falling the most but when the shake table shook the Lego towers would sink into the sand instead of falling over. Also the dirt was in the middle of the cat litter and sand in the protection factor. On all three soils, when the base to height ratio increased the Lego towers became more stable. Lego towers with a base to height ratio of over ten very rarely fell down. This occurred only twice over 120 trials. Conclusions/Discussion My results did not clearly support my hypothesis, which was that dirt would protect the Lego towers the best against the 1.5 V and 3 V earthquakes. I can conclude that cat litter was the least stable. Although sand kept the Lego towers from falling better than dirt it is on such a small scale and I could not measure the damage done to the Lego towers. So I can conclude that sand kept the Lego towers the best from falling but I could not measure damage so I would further this project by making a bigger scale and use real building codes to make it more realistic. The base to height ratio played a big part in my project, and a base to height ratio of ten marked a threshold for not falling down.

Awards (1)

• Fourth Place

Competition history

• CSEF 2011 Earth & Planetary Sciences · Entry J0810

Resources

• CSEF project summary ↗

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