<p>This paper explores the influence of uncertainty related to the rock mass properties on the stability of strip footing. The behavior of rock mass is evaluated by utilizing the generalized Hoek–Brown failure criterion and the associated strength parameters: (1) Geological strength index (<i>GSI</i>), (2) normalized uniaxial compressive strength of the intact rock, and (3) Hoek–Brown material parameter (<i>m</i>_<i>i</i>) are considered as spatial random parameters. The primary aim of this study is to examine the impact of the parameter <i>GSI</i>, conceptualized as a random block spatial field instead of a random variable. The concept of a random block spatial field involves partitioning the domain into a set of stochastically generated blocks of substantial volume, designed to effectively capture localized heterogeneity within the rock mass. The finite element analysis is conducted through the application of the lower bound limit theorem alongside power conic programming. The random rock mass domain is discretized using the Cholesky decomposition method, and the Monte Carlo simulation approach is utilized to derive the probabilistic response. The percentage change in failure probability of strip footing (<i>T</i>_<i>f</i>) is calculated by considering the <i>GSI</i> as a random variable, as well as a random block spatial field across different configurations of blocks. The results demonstrate a considerable variation in the magnitude of <i>T</i>_<i>f</i>, and the maximum percentage increase in <i>T</i>_<i>f</i> is observed as 4.5 to 6.75% for <i>µ</i>_<i>GSI</i> ranges between 20 and 80. The probabilistic results are presented by utilizing the cumulative distribution function and probability density function, taking into account various configurations of blocks and autocorrelation lengths. The required safety factors (<i>FOS</i>_<i>req</i>) are evaluated corresponding to target failure probability (<i>P</i>_<i>ft</i>) for a range of input rock parameters.</p>