An Investigation Into Ground Improvement Using Geogrid Encased Stone Columns

Download or read book An Investigation Into Ground Improvement Using Geogrid Encased Stone Columns written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional stone columns are commonly used as a form of ground improvement in soft soils, for the support of lightly and moderately loaded structures such as embankments. However, their use in very soft and extremely soft soils is limited by the low stiffness and minimal confinement provided by the soft soil. To extend their use to such soft soils, a method of geotextile encasement has recently been developed, providing additional circumferential confinement. The technique has been used on numerous projects throughout Europe and more recently in South America. Although geotextile encasement provides a practical form of ground improvement, its use can be limited in some cases by excessive settlements, resulting from the adopted materials and installation practices. To investigate the potential benefits of using a stiffer encasement than geotextile (and to broaden the appeal of geosynthetics in ground improvement), the use of geogrid encasement is investigated. The research presented in this thesis was used to investigate practical aspects of geogrid encasement including developing effective and efficient methods of encasement construction and assessment of encased column performance. The research was undertaken using a four-stage approach comprising small-scale laboratory testing, numerical simulation of small-scale tests, medium-scale laboratory testing and scaled-up numerical modelling of full-scale columns. Small-scale testing was undertaken on isolated and simulated group columns to investigate whether the full-length of the column needed to be encased, the impact of geogrid stiffness and methods of constructing the encasement. Numerical modelling was undertaken using the PLAXIS software package and was initially used to reproduce the small-scale test results. Following this, the models were scaled up to investigate the impact of different parameters on full-scale encased column behaviour. Medium-scale testing of unconfined columns was used to investigate metho.