The fact that particle breakage alters the critical state line (CSL) in void ratio-mean stress space is now well-known and no longer debated. Thus, modeling the stress-strain behavior of crushable sands at high pressures, considering the effects of evolution in particle size distribution (PSD) on CSL, and concurrently prognosticating the extent of breakage has become a significant challenge. Recently, the framework of continuum breakage mechanics (CBM) was introduced to address these requirements. However, CBM-based models assume that soils transition from elasticity to elastoplasticity only when fragmentation initiates. On the other hand, indeed, the elastoplastic behavior of soils begins well before crushing. As a consequence, similar to elastoplasticity, CBM-based models (i) may also show sudden changes in stress rate versus strain rate relation and breakage state variable; (ii) may unrealistically overestimate peak stress during undrained conditions. To overcome such issues, this study aims to integrate the concept of subloading surface (SLS) into a simple CBM-based model suitable for high pressures. The sensitivity analysis carried out in this work shows that the devised model delivers more realistic outcomes than those simulated via the classical base model.