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The use of soil mixing for providing stabilization of soft or loose soils is considered a fairly new technology in the United States. Soil mixing has been successfully applied for liquifaction mitigation, steel reinforced retaining walls, groundwater cutoff walls, and stabilization of contaminated soils. Applications of this technology have recently been further expanded. Such applications have included settlement control of soils, slope stabilization and the formation of composite gravity structures. To design for these applications, the unconfined compressive strength, elastic modulus and shear strength of the soil and soil-cement columns must be determined or estimated. Settlement control of soft or loose soils under service loads can be sufficiently controlled with treatment ratios in the 20% to 35% range. On a recent project in Honolulu, Hawaii, loose soils were sufficiently stabilized with a 23% treatment ratio, and at a site in Lakeland, Florida, a very soft and compressible clay layer was sufficiently stabilized with only a 12% treatment ratio. In slope stability applications, soil mixing improves the overall shear strength of the soil formation to adequately increase the factor of safety, and also the soil-cement columns can force the potential failure surface deeper. Lastly, soil mixing has been applied to construct in-situ gravity structures where its composite action design assumption was confirmed with an instrumented test wall, and used in two recent commercial applications.

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In anchor pullout design, conservative soil and rock shear strength parameters are usually adopted. Presumptive values of soil/grout and rock/grout bond strength are available in different design manuals. In this study, in-situ pullout test data for anchors in soil and rock type worldwide were collected from published sources and information provided by specialty wall contractors. The measured pullout test data were compared to estimated pullout resistance using the Post-Tensioning Institute (PTI) presumptive bond strength values. Statistical analysis was performed to determine the probability of success and the corresponding reliability indices using the minimum, average and maximum PTI ground/anchor bond strength values for cohesive soils, cohesionless soils and different rock types. A minimum safety factor of 2 recommended by the PTI to the ground/grout bond strength was found not conservative where the maximum presumptive bond strength values were used in clays and sands, and the average and the maximum presumptive bond strength values were used in rocks. Based on the results of this study, an average minimum factor of safety was recommended for ground/grout bond strength.