Field miniature prototype development and pilot project design of subsurface compacted Rubble Raft (SCRR)

Abstract

Subsurface Compacted Rubble Raft (SCRR) is a patented wide-area ground improvement solution that focuses on solving severe liquefaction hazards. SCRR technique directly targets the liquefaction layers by constructing a manmade geological stratum in subsurface, generally at a varying depth from 3 to 10 m, it works as one continuous densified aggregate mass compacted with high-level power under a land section or a block of land. The formed SCRR raft works as a solid CRUST on top to eliminate and bridge the manifestation of liquefaction in soils underlain. Comparing with other traditional solutions, SCRR can save 30% to 40% costs in upgrading land with severe liquefaction risks, such as the Red Zoned land and Technical Category 3 (TC3) sections to a TC1 or TC2 criteria. This paper aims to report the miniature prototype development of the SCRR solution; present the preliminary SCRR structural elements; reveal its basic mechanism; discuss the soil improvement outcome; finally, scrutinise the installation parameters for the pilot project scheduled in Jan 2023, which is a R&D project partially sponsored by the Callaghan Innovation. On 4 Oct 2022, New Zealand GNS Science released the revised National Seismic Hazard Model (NSHM). Subsequently, it can be anticipated that more sites and land sections will be categorised into the criteria of High Liquefaction Vulnerability that need specific geotechnical design and wide ground improvement, as such, the SCRR solution provides one more flexible and affordable option to the industries to free up tens of thousands of land sections at High Liquefaction Vulnerability.