Determination and Verification of Strength and Stiffness Properties of Grouted Soil-PPT Presentation

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The study investigates how to determine and predict the strength and stiffness of soil improved by permeation grouting. Such properties are difficult to assess because grout distribution and cement content vary in the ground, and extracting representative samples is challenging.<br /><br />Water–cement (w/c) ratio describes the grout mixture but does not account for sedimentation and filtration during injection. The researchers therefore propose cement content as a more useful parameter for predicting grouted-soil behavior. They developed a simple method to estimate cement content from mass loss during ignition, based on the chemically bound water in cement hydrates. Tests on hardened grout also showed that dry density can help predict grout strength.<br /><br />Laboratory testing used cement-grouted sand and gravel, with uniaxial compression and triaxial tests. Large-scale field tests were conducted in alluvial sandy gravel using sleeve pipes and instrumentation to monitor ground pressures and deformation. Specialized sampling equipment successfully produced numerous high-quality field samples.<br /><br />Laboratory and field results corresponded well. Cement content was the main factor governing strength, stiffness, and load–deformation behavior; soil type, grading, and cement type had comparatively minor effects. Confining pressure had only a limited influence on the stress–strain response, which differed substantially from that of untreated soil. Strength and stiffness were approximately linearly related.<br /><br />Overall, the study finds that cement content should be preferred over w/c ratio when characterizing grouted soils, and that the proposed cement-content determination method is simple and robust.

Keywords

permeation grouting

cement content

soil improvement

strength prediction

stiffness

water-cement ratio

grouted soil

mass loss on ignition

dry density

triaxial test