Reliability Based Predictive Model for Estimating the Field Hydraulic Conductivity of Compacted Cement Kiln Dust Treated Black Cotton Soil

A predictive model of field hydraulic conductivity of compacted cement kiln dust treated black cotton soil as landfill liners was under taken using FORTRAN-based First-Order Reliability Method (FORM). Reliability estimates of hydraulic conductivity was developed from data obtained from laboratory results for specimens compacted at the energy levels of British standard light (BSL) and West African standard (WAS) British standard heavy (BSH). Statistical analyses were carried out on data using Mini-tab R15 statistical software. Statistical Results obtained were incorporated into a FORM program and safety index values obtained. Generally, only BSH compactive effort produced satisfactory safety index value of 1.0 as specified for serviceability limit state design for hydraulic conductivity. Compositional factor such as water content relative to optimum failed to produced acceptable safety index value of 1.0 at the energy levels of BSL, WAS and BSH compactive efforts for coefficient of variation (COV) ranges of 10-100%. Observed trends indicate that the degree of saturation, plasticity Index, cement kiln dust content and percentage fines are greatly influenced by the COV and therefore must be strictly controlled in cement kiln dust-black cotton soil mixtures for use in covers and liners in waste containment facilities. Stochastically, only BSH compactive efforts can be used to model the hydraulic conductivity behavior of cement kiln dust treated black cotton soil for landfill liners at the variable ranges of 0-80% COV. Finally, care must be taken in ensuring that the compactive efforts required to produce successful safety index are carefully monitored during the construction of liners and covers in waste containment facilities.