Geophysical and in situ testing applied to site characterisation for nonengineered structures in developing regions

Abstract

Residential dwellings have been estimated to represent more than three quarters of the building stock around the globe, most of which are not believed to have been properly engineered (that is, designed by architects or engineers and constructed by skilful workers with adequate materials). Narrowing the scope to developing countries, over a 90 percent of the population is deemed to be living, working or studying in nonengineered buildings. In earthquake-prone regions, these weak structures can become deathtraps for their occupants, forlornly adding to the casualty lists of recent and past seismic events. Thus, improving seismic resilience for vernacular housing has increasingly become a main theme for researchers. Also, other geotechnical issues, such as subsidences, slope instabilities, excessive settlement on soft soils, groundwater, inadequate designs, etc., are responsible for substantial risk of structural damages, ranging from small structural pathologies to major disasters. One of the keys to develop new safe and efficient foundation designs, or to retrofit existing ones, is to make available portable and low-budget ground probing techniques. This document will describe some of the most feasible in situ devices available, as well as discuss how seismic and electric methods can be used as portable and powerful tools to characterise both the strength and the stiffness of soils thanks to recent developments in stablishing the relationship between geophysical results and traditional geotechnical parameters (such as the SPT, the angle of internal friction, shear strength, etc.), with the help of statistical methods and dimensional analysis techniques.