This paper describes the changes in in situ index properties following installation of rammed aggregate piers in a loose sand deposit in New Madrid, Missouri, with a particular focus on the time-dependent strength gain, commonly called sand ageing, as indicated by increased cone penetration test (CPT) tip resistance and dilatometer test (DMT) indices. The method of disturbing the soil and the magnitude of disturbance significantly influence the magnitude of sand-ageing effects. This paper provides the first data on sand ageing following the installation of displacement rammed aggregate piers. In this study, CPT and DMT were performed both immediately before and after the installation of piers. Additionally, CPTs were performed 1 month following the installation of piers. The DMT horizontal stress index increased roughly 100% and the dilatometer modulus increased 200% in a loose clean sand layer immediately following the installation of the piers. The CPT tip resistance increased roughly 100% in this layer immediately following the pier installation and a further 33% in the month following the installation.
|Original language||English (US)|
|Number of pages||11|
|Journal||Proceedings of the Institution of Civil Engineers: Ground Improvement|
|State||Published - May 1 2018|
Bibliographical noteFunding Information:
Support for the research presented herein came in part from the NSF grants CMMI 0530378, CMMI 0900105, CMMI 1300010 and CMMI 1435494. The Geopier Foundation Company coordinated access to the project site and provided the CPT data from 1 month after installation. Pioneer Seeds donated the use of its land and the expertise of its employees. ConeTec Investigations Ltd and the ConeTec Education Foundation are acknowledged for their support to the Geotechnical Engineering Laboratories at the University of Michigan. Mr Jan Pantolin and Dr Yongsub Jung provided valuable assistance conducting in situ testing. This support and assistance are gratefully acknowledged.
- Geotechnical engineering
- Granular materials
- Site investigation