John Hislam, director, Applied Geotechnical Engineering. This paper was first published in GE’s September 2010 issue.
Chemical grout injection is a popular method for improving the stability and reducing the permeability of alluvial soils, but it is not always clear if the methodology adopted in a particular application of the practice represents the most efficient or cost-effective option.
It is possible, however, to use simple formulae to aid in the selection of injection parameters and to understand their inter-relationship, as well as to optimise injection spacings and times with respect to injection source dimensions and insitu permeability. A better understanding of these parameters can help when it comes to calculating the real cost of an injection programme and how to modify a scheme in progress to gain the best result.
In recent years “tube á manchette” injection systems have been adopted for grouting in alluvial soils, but a better understanding of the factors involved in grout injection can make simpler - and less expensive - driven rod injection methods equally appropriate in many situations.
The grout injection schemes considered in this paper are applicable to alluvial soils where a two-stage cement/chemical injection programme is usually used.