As rainwater infiltrates through a soil slope, water pressure builds up in the soil pores. When this soil pore-water pressure exceeds a critical limit, a landslide occurs. There are several theoretical models, such as the Iverson model (Iverson 2000), that predict the water pressures which build up in response to rainfall of a given intensity and duration. However, many of these theoretical models have not been experimentally verified. And none of them have been validated for the geo-morphological conditions prevalent in the landslide prone Western Ghats of India.
The landslide team at Amrita Vishwa Vidyapeetham is in a unique position to examine the validity of these models for the Western Ghats. We have collected vast amounts of geophysical sensor data from a landslide prone site in the Western Ghats. We have rain gauges that have been recording rain data every 30 seconds for the past five years, and 48 piezometers that have been recording the corresponding changes in the soil pore-water pressure, also every 30 seconds for the past five years. The piezometers are installed at different depths, ranging from approximately 3m to 21m. We have also performed several laboratory tests to determine the geotechnical properties of the soil.
In this Ph.D., the student is expected to develop a theoretical model of rainwater infiltration that is validated by the existing Amrita Vishwa Vidyapeetham field data. The model should predict the soil pore-water pressures that build up in response to rainfall of a given intensity and duration. Since the soil, climatic and vegetation conditions at the current deployment site are representative of the conditions at many other regions of the Western Ghats, the model developed by the Ph.D. student can be applied to all such regions, and rainfall thresholds can be developed for these regions. These rainfall thresholds can then be used to provide early warnings of impending landslides.
In the course of his/her study, the student might also discover that by building proper drainage systems or by advising the residents on the proper disposal of waste-water, the pore-pressure that builds up in the hill slope may be controlled and future landslides may be averted.