Development of Landslide Warning System

Abstract

Landslides cause approximately 25 to 50 deaths and US$1 - 2 billion worth of damage in the United States annually. They can be triggered by humans or by nature. It has been widely recognized that rainfall is one of the major causes of slope instability and failure. Slope remediation and stabilization efforts can be costly. An early warning system is a suitable alternative and can save human lives. In this project, an early warning system was developed for a 40-foot-high cut slope on the island of Hawaii. To achieve the objective, subsurface investigations were performed and undisturbed samples were collected. For the purpose of unsaturated soil testing, new testing apparatuses were developed by modifying the conventional oedometer and direct shear cells. The unsaturated soil was characterized using two separate approaches and, later, the results were discussed and compared. The slope site was instrumented for the measurement of suction, water content, displacement, and precipitation. The collected climatic data along with the calibrated hydraulic parameters were used to build an infiltration-evapotranspiration numerical model. The model estimations were compared with the field measurements and showed good agreement. The verified model was used to determine the pore-water pressure distribution during and after a 500-years return storm. Later, the pore-water pressure distribution was transferred to a slope stability software and used to study the slope stability during and after the storm. Based on a 2D slope stability analysis, the slope can survive the 500-year storm with a factor of safety of 1.20. Instrument threshold values were established for water content sensors and tensiometers using a traffic-light-based trigger criterion.