What if there is an earthquake in Bengaluru? While we may not be sure of the resultant damage, scientists at the Indian Institute of Science (IISc), Bangalore have found how a waste landfill may react to it. A group of scientists from the Department of Civil Engineering and Center for Sustainable Technologies have studied the response of Municipal Solid Waste (MSW) landfills to seismic activities. This study is a first of its kind to be conducted on Indian soil.
India generates about 1,88,500 tonnes of MSW per day. This waste is collected and buried in large landfills in the outskirts of cities. A study on the effect of earthquakes on these landfills is important to lower seismic activity related hazards and prevent potential health problems in and around these areas. Difficulty in data collection and associated health risks has prohibited any such study in the Indian context, in the past.
The team chose the infamous Mavallipura landfill site located on the outskirts of Bengaluru, for the study. The landfill here is spread over 30 acres, is around 10 meters in height and is covered with 10–20 centimeters of natural soil. As a first level of treatment, recoverable and recyclable waste is hand sorted. The remaining waste is then subjected to aerobic composting for a period of two months. A test sample of the landfill waste consisted of clothes, plastics, glass, leather, coconut, stones, rubber, wood and organic matter.
During the study, the team performed seismic field tests and also collected samples of the landfill for laboratory testing. In the field test, surface vibrations were created and recorded to determine the subsurface information and dynamic properties of the landfill. Laboratory tests included stress and strain tests to measure shear properties of the waste in the landfill. "Seismic design of the landfills requires an understanding of the dynamic properties of municipal solid waste (MSW)", says Dr. P. Anbazhagan, one of the team members.Computer based simulations were carried out to simulate ground motion using historical earthquake data in the region and the response of the landfill were recorded. "Our work describes the seismic analysis and the dynamic response of the municipal solid waste landfills",adds P Lakshmikanthan.
Factors like the height of the fill, its stiffness, dynamic properties of refuse present and the presence of clay liners affects a landfill's response to earthquake. The response of the landifill surface situated above various combinations of soil and bedrock at the bottom of the waste column were studied. A better understanding of the dynamics of the materials constituting the landfill will provide valuable guidance to engineers for designing stable landfills that can withstand earthquakes and cause minimum damage to the surroundings.
This study shows that the landfill is shallow, having less shear stiffness and may be prone to amplification if there is any earthquake, which need to be accounted in the seismic design of MSW landfills. "
About the authors:
GL Sivakumar Babu is a Professor and P Anbazhagan is an Assistant Professor at the department of Civil Engineering, IISc, Bangalore. P Lakshmikanthan is a Senior Research Associate at the Centre for Sustainable Technologies, IISc, Bangalore, KS Vivek Anand is a Research Assistant at the department of Civil Engineering, IISc, Bangalore.
Contact: Prof G L Shivakumar Babu Phone:+91 80 2293 3124