# A Review of Evaporite Beds Potential for Storage Caverns: Uncovering New Opportunities
## 3 Properties and Geomechanics of Bedded Evaporites
### Mechanical Properties  
The mechanical properties of rocks play a pivotal role in geomechanical applications, including wellbore stability, cavern tightness, and subsidence. The primary mechanical properties of rocks include elastic modulus (Young's modulus), Poisson's ratio, and rock strength [162]. Two other mechanical properties, shear modulus and bulk modulus, are derived from Young's modulus and Poisson's ratio. The stability and safety of cavern storage are significantly impacted by the creep behavior of salt [44]. Young's modulus is defined as stress over strain [163]. Two main types of [PERSON]'s modulus measurement, including static and dynamic measurement, from both experiments and well logs are described in [164]. Since static Young's modulus is essential for geomechanical calculations, empirical relations converting dynamic Young's modulus to static [PERSON]'s modulus are also provided. An example of [PERSON]'s modulus calculation based on the uniaxial compression test is described in [165]. The experimental data are used to illustrate the stress-strain curve under a uniaxial test and show three different methods for calculating [PERSON]'s modulus, including tangent, average, and secant Young's modulus. Poisson's ratio is the ratio of lateral to axial strain resulting from uniform axial stress [166]. The uniaxial compression test was used in [167] to estimate [PERSON]'s ratio for various rocks. Similar to [PERSON]'s modulus determination, three methods for calculating [PERSON]'s ratio, tangent, average, and secant Poisson's ratio in intact rocks are suggested in [168]. Rock strength reflects a rock's ability to withstand stress without fracturing or reaching the yield (permanent deformation) point. Rock strength can also be determined in the laboratory via uniaxial or triaxial compressive strength tests. If only an estimate of compressive strength is required, other tests, such as point-load and Brazilian tests, may be used [169]. Figure 11 illustrates stress-strain curves of different rocks under the triaxial compression test, including (1) an incomplete post-peak curve, (2) a complete post-peak curve, (3) strain softening, and (4) a plastic yield curve [170]. Salt caverns are constructed in bedded salts deep underground, making it essential to understand the failure mechanisms of all overlying layers. Cyclic loading during gas storage in caverns may lead to failure in the surrounding rock. Various failure criteria have been developed to predict rock failure under different loading conditions, including but not limited to the Mohr-Coulomb, Hoek-Brown, Modified Lade, Modified Wiebols and Cook, Mogi, and Drucker-Prager criteria, which are compared in [171]. Additionally, ref. [172] discusses the von [PERSON], Griffith, and Mogi-Coulomb failure criteria to describe rock failure. A unique characteristic of rock salt is its self-healing property, controlled by its creep behavior. Creep behavior, defined as time-dependent deformation under constant stress, is crucial for the long-term stability of salt caverns. A review of creep constitutive models for various rocks is presented in [38]. Empirical models, which are described as models established based on creep test results and examples of utilized fitting functions such as the Power function, Norton Power Law, Bailey-Norton Law, etc., are reviewed. In addition, a review of component-combined creep models (e.g., [PERSON] model, [PERSON] model, and Burger model), as well as the common elements used in developing those models (e.g., [PERSON]'s body, [PERSON]'s dashpots, and St. Venant elements), is provided. A thorough review of mechanism-based creep constitutive models aiming to describe microscopic damages because of mechanical reactions is also given. More specifically, ref. [44] reviewed the creep properties and a constitutive model of salt rock in detail. Several researchers have investigated the mechanical properties of bedded rock salts. For experimental studies, refs.