Determination and Verification of Strength and Stiffness Properties of Grouted Soil-Paper

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The paper investigates how to determine and verify the strength and stiffness of granular soils improved by permeation grouting. Because grouted soil behaves differently from both untreated soil and concrete, conventional assessment methods and water–cement ratio alone are insufficient.<br /><br />Researchers conducted laboratory tests on artificially grouted sand and gravel specimens, varying soil type and cement content, and performed uniaxial compression and drained triaxial tests. They also carried out three large-scale field grouting tests using alpine sandy gravels, recovering 94 specimens for testing.<br /><br />A key contribution is a method for estimating cement content from ignition-related mass loss and the amount of chemically bound water in hardened cement. This measure better reflects the material responsible for strength development than the initial water–cement ratio. Results showed that increasing cement content substantially increases strength and stiffness. Strength has a nonlinear relationship with cement content, while Young’s modulus increases approximately linearly. For specimens with high cement content, confining pressure had little effect on the stress–strain curve; its influence was greater at lower cement contents.<br /><br />The authors combine laboratory and field results to propose correlations for predicting strength from cement content, accounting for differences in soil density. These correlations can support grouting design and quality assessment. Cement content can also be measured in core fragments and used to estimate strength when intact samples cannot be obtained. The method offers a practical basis for more reliable verification of grouting works.

Keywords

permeation grouting

granular soils

cement content

strength and stiffness

uniaxial compression

drained triaxial tests

Young's modulus

alpine sandy gravel

field grouting tests

quality assessment