Groutability enhancement effect of oscillatory injection in cement-based permeation grouting

Cement-based permeation grouting is utilized in foundations and tunneling projects for waterproofing or ground improvement. The drawback of this method is that, because of the clogging phenomenon, the grout penetration depth is limited in most soil types. In order to overcome this drawback, an oscillatory injection method and equipment were proposed. Laboratory-scale oscillatory grout injection tests were performed with variation of the injection pressure, oscillation frequency, and water-cement (w/c) ratio. The enhancement effect of the groutability was theoretically studied using clogging theory and was assessed according to the Groutability Criterion. The results showed that the grout injection volume and penetration depth were increased by more than 30 % and up to 250 %, respectively, when utilizing the proposed oscillatory injection system. In particular, it was found that the enhancement of the permeation grouting that is due to the oscillatory injection is more dominant with lower injection pressure, oscillation frequency ranges of 5-10 Hz, higher vibration amplitude, and lower w/c ratio.