Jet grouting and deep soil mixing are sophisticated ground improvement and soil stabilisation techniques. While offering a nuanced comparative assessment of both methods this integrates theory, practice, and cutting-edge innovation, to present a comprehensive analysis of current technologies, design methodologies, quality assurance protocols, and benchmarking case studies. It introduces data acquisition and advanced modeling, as well as laboratory and in-situ testing, sensor integration, and modern control systems, alongside detailed coverage of analytical, empirical, data-driven, and numerical modeling strategies. With a team of specialist contributors, real-world case studies give profiles of innovative projects. It is primarily for practising engineers, and also useful as an up-to-date guide for graduate students about to embark on a career in design or construction.