Construction of a new cavern modifies the state of stresses and movements in a zone around the existing cavern, as some degree of interaction between these two caverns takes place. Extensive plane strain finite difference analyses were carried out to examine the deformations induced by excavation of underground twin caverns. Based on the numerical results, a fairly simple nonparametric regression algorithm known as multivariate adaptive regression splines (MARS) model has been used to relate the percent strain to various parameters including the rock quality, the cavern geometries and the in situ stress ratio. Probabilistic assessments on serviceability limit state of twin caverns can be performed using Monte Carlo simulation (MCS) and First-order reliability method (FORM) for comparison. These two reliability approaches give similar and consistent results.