Effects of jet grouting under sheet piles on seepage failure stability of soil

In the design of excavations of soil with a high ground water level, sheet piles are often used as soil and water retaining structures. Consider a case where deeper penetration of sheet piles is required during construction due to changes in in-situ conditions. Ground improvement such as jet grouting under the pre-constructed sheet piles is one of the supplementary methods for lengthening the cut off wall. Here the supplementary injection of jet grouting under sheet piles is investigated as a prevention method for seepage failure of soil. For the jet grouting method, the following topics are discussed: "How low should the permeability of grouting be? How thick should the grouting be?"