Reliability Assessment of Geotechnical Structures on Soils improved by Deep Mixing Method I: Data Collection and Problem Setting

Construction of geotechnical structures on marine soils improved by deep mixing method (DMM) is recent trend in Korea. Since there are many uncertainties involved in the design of structures on DMM foundation, introducing reliability methods to deal with uncertainties of DMM foundation has been discussed in the engineering society. This two-paper set addresses the reliability assessment applied to the design of the structures on DMM improved soil. In the first paper, the compressive strength data collected from the sites of DMM improved soil were analyzed and their Coefficient of Variation (COV) and probability distribution were decided. COV of compressive strength data obtained from the sites of DMM improved soil was 0.34, which was relatively smaller than the values obtained from other countries, because domestic use of the types of mixing equipment and material are not diversified. The probability distribution of the compressive strength data fit both to normal and lognormal distributions. Six limit state functions were formulated corresponding to both the external and internal stabilities of the structures on DMM improved soil. The companion paper addressed the implementation of the reliability analyses and proposed the target reliability index for the geotechnical structures on DMM improved soil.