Laboratory investigation of multiple grout injections into clay

Abstract

Compensation grouting is a multiple injection process in which large numbers of grout injections are carried out in a designated grouting zone. Each injection alters the in-situ stress state at the site of neighbouring injections, influencing the grout behaviour as well as the deformation of the surrounding soil. In this study, multiple grout injection tests were performed in the laboratory on clay specimens prepared at different overconsolidation ratios ranging from 1 to 10. Two types of grouting mode for compensation grouting were examined: (a) facture grouting by injecting epoxy resin, and (b) compaction grouting by expanding a latex balloon placed inside the soil specimen. The sequence of multiple injections was also varied by injecting either simultaneously or sequentially with different waiting periods. For highly overconsolidated clay the grout efficiency, defined as the ratio of the volume of heave achieved to the injected grout volume, was close to 1 irrespective of grout spacing and injection sequence. For normally consolidated and lightly overconsolidated clays the grout efficiency increased when the separation in space and time between the injections was reduced. A better grout efficiency was obtained in compaction grouting than in fracture grouting. The results from finite element analyses of the laboratory tests show that the magnitude and extent of excess pore pressure reduce when many closely spaced simultaneous injections are performed. A few non-simultaneous injections create large stress concentrations around the injection points, leading to larger soil consolidation.

Coupled discrete element modeling of fluid injection into dense granular media

“…[10] Laboratory experiments of fluid injection under triaxial conditions have been conducted in sand and in mixtures of sand and silica flour [Khodaverdian and McElfresh, 2000;Chang, 2004;Bohloli and de Pater, 2006;Bezuijen et al, 2006;Dong and de Pater, 2008;Zhou et al, 2010;Golovin et al, 2010Golovin et al, , 2011Germanovich et al, 2012;Hurt and Germanovich, 2012;Ispas et al, 2012] and in clay [Murdoch, 1993b[Murdoch, , 1993cBolton et al, 1994;Au et al, 2003;Soga et al, 2004]. While the experiments in clay have mostly produced opening mode tensile fractures, the phenomena in sand are much more complex due to the coupling of fluid infiltration and grain displacements.…”

Pressure-controlled cavity expansion in clay

“…1. Only a brief description of the apparatus and experimental procedure are given here, and readers interested in the details of the apparatus should refer to Au (2001), Soga et al (2004), and Au et al (2006).…”

Experimental study on grouting in underconsolidated soil to control excessive settlement

“…The tip of the needle had four uniformly distributed 2-mm-diameter holes covered by an expandable latex balloon. Water was injected into the latex balloon to simulate an ideal compaction grouting (Au et al 2003;Soga et al 2005;Wang et al 2009Wang et al , 2013 where no bleeding or solid penetration could occur.…”

“…Wang et al (2013Wang et al ( , 2013) designed a new laboratory apparatus and conducted scaled laboratory experiments to study the effect of dynamic compaction frequency on compaction efficiency. Au et al (2003) and Soga et al (2005) used modified consolidometers to investigate grouting efficiency under various overconsolidation ratios, grout materials or injection methods.…”