Abstract: Vague information widely exits in parameters used for analyzing geotechnical engineering. After the distribution of eigenvalue of samples had been studied, it was indicated that the vague factors in parameters could not be ignored. According to the membership function of parameters, the equations of fuzzy eigenvalue of sample parameters was deduced. Its reasonability was also proved. The case study indicates that the fuzzy method is better than the classical stochastic method because its variance is less than the results obtained by stochastic method in any case. The results also indicate that the fuzzy statistic method is worth of being generalized in engineering application.

Key words: membership functions, fuzzy mean, fuzzy variance, statistic eigenvalues