A simplified reliability and risk analysis method of foundation bearing capacity based on combined coefficients of variation of random variables is proposed using first order second moment technique. The laboratory results and historical published ones of coefficients of variation are taken into consideration as the combined coefficients of variation

which are adopted as the calculated coefficients of variation. The most likely values and their possible ranges of degrees of reliability

probabilities of failure and average expected losses can be obtained using suitable coefficients of variation besides the conventional deterministic analysis. This enables to make optimal design scheme and engineering decision. It has shown that the degrees of reliability of foundation bearing capacity are more sensitive to the internal friction angle compared with the unit weight and the cohesion. The width or area of foundation can be decided upon in terms of the required factor of safety

degree of reliability and probability of failure. Moreover

the combined coefficients of variation of random variables will gradually decrease with the weights increasing of coefficients of variation based on the in-situ investigation results; the corresponding degrees of reliability will increase and the probabilities of failure decrease due to that decrease of combined coefficients of variation.