An appropriate stress–strain relationship of geomaterials subjected to blast loading is essential for the design of underground protective structures. Previous experimental and theoretical research efforts indicate that the constitutive behavior of geomaterials under blast loading depends upon strain rate, stress level, and interaction among the three phases (solid, liquid, and gases). In current state-of-the-art, various advanced constitutive models are available to model the stress–strain behavior of geomaterials under blast-loads. However, considering the cost of computation associated with such models, a functional form is discussed to model the loading and unloading branches of stress–strain curve of geomaterials subjected to blast load based on the three parameters: weight factor, initial modulus ratio, and strain recovery ratio. It is observed that the new functional form reasonably captures the mean trend of the experimentally obtained or simulated stress–strain data. This paper further investigates the applicability of this functional form and provides a catalog of the model parameters for direct use by practicing engineers. The dependence of function parameters on strain rate, lateral confinement, degree of saturation, initial compaction, and locking initiation stress is investigated, and some simple rules are proposed for reasonable estimation of the three parameters. The proposed functional form would be quite useful in practical design problems specially where cost of computation associated with advanced constitutive models is too high. In addition to this, the proposed simple parametrization of complex nonlinear stress–strain behavior also provides an opportunity to investigate the effect of uncertainties in soil parameters in a computationally efficient manner.