The revival of multiple pore pressure measurements in the cone penetration test

In common practice the most usual positioning of the filter location for the piezocone (CPTU) is at the cone shoulder (u₂) which is recommended by ISO 19901-8:2014 and ISO 22476-1:2012. However, these ISO standards allow additionally for pore pressure measurements to be taken at the cone face (u₁) or behind the friction sleeve (u₃). The triple element piezocone (CPTU3) offers a solution whereby measurements of pore pressure can be taken simultaneously at all three locations. By taking these three pore pressure measurements the soil behaviour classification may be enhanced by interpretation in terms of c_h from u₁, u₂ and u₃ and by correlations to overconsolidation ratio (OCR) and lateral stress ratio (K₀). In this paper the correlations to OCR are explored by establishing a database from historical data as presented in international geotechnical literature.