Abstract
Abstract. Extensive land subsidence can occur due to subsurface dissolution of evaporites such as halite and gypsum. This paper explores techniques to simulate the salt dissolution forming an intrastratal karst, which is embedded in a sequence of carbonates, marls, anhydrite and gypsum. A numerical model is developed to simulate laminar flow in a subhorizontal void, which corresponds to an opening intrastratal karst. The numerical model is based on the laminar steady-state Stokes flow equation, and the advection dispersion transport equation coupled with the dissolution equation. The flow equation is solved using the nonconforming Crouzeix–Raviart (CR) finite element approximation for the Stokes equation. For the transport equation, a combination between discontinuous Galerkin method and multipoint flux approximation method is proposed. The numerical effect of the dissolution is considered by using a dynamic mesh variation that increases the size of the mesh based on the amount of dissolved salt. The numerical method is applied to a 2-D geological cross section representing a Horst and Graben structure in the Tabular Jura of northwestern Switzerland. The model simulates salt dissolution within the geological section and predicts the amount of vertical dissolution as an indicator of potential subsidence that could occur. Simulation results showed that the highest dissolution amount is observed near the normal fault zones, and, therefore, the highest subsidence rates are expected above normal fault zones.
Highlights
Salt deposits are common in continental regions (Kozary et al, 1968)
This paper explores techniques to simulate the salt dissolution forming an intrastratal karst, which is embedded in a sequence of carbonates, marls, anhydrite and gypsum
The numerical model is based on the laminar steady-state Stokes flow equation, and the advection dispersion transport equation coupled with the dissolution equation
Summary
Salt deposits (e.g. rock salt) are common in continental regions (Kozary et al, 1968). The authors found that the number of faults with increased permeability within the normal fault zone is the most important factor that affects the dissolution compared to the other investigated parameters of aquifer thickness above the salt layer, a dynamic hydraulic conductivity of the aquifer above the salt layer, and varying boundary conditions due to pumping activities. The continuous development of the intrastratal karst creates an opening of the void at the top of the salt layer To account for this phenomenon, a new formulation of the moving boundary condition is proposed to simulate the dissolution process with the laminar density-driven Stokes flow. The moving boundary condition is based on a Dynamic Mesh Method (DMM) that adapts the size of the mesh with respect to the amount of displacement at the moving boundary
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
