Porous Media Storage: Specific Storage in Aquifers, Exercises of Groundwater Flow and Contaminant Transport

Download Porous Media Storage: Specific Storage in Aquifers and more Exercises Groundwater Flow and Contaminant Transport in PDF only on Docsity! 1 Storage Properties of Porous Media 1. Specific Storage and Storativity Recall Eq 4.8 = Let = (Eq 4.10), where Ss is the specific storage [L!1], defined as Ss = A related term, storativity or storage coefficient, is defined as S = So, S = Ss×m, where m is the thickness of aquifer 2. Ss for Confined Aquifer (A) Fluid expansion/contraction (Lecture 5 notes) Y Y (1) ‡ ˆ ˆ (2) Substituting Eq 2 into Eq 1 gives (4.20) Eq 4.20 states that fluid density decreases with decreasing pressure (H2O expands) and increases with increasing pressure (H2O contracts). 2 From Eq 4.10 Assuming incompressible matrix and substituting Eq 4.20 into the above equation gives (4.22) is the Ss value resulting exclusively from expansion or contraction of water when pressure head changes. = 4.8×10!10 m2 N!1 (B) Matrix expansion/compression Following the treatment of fluid, assume (4.25) - bulk compressibility [L2 F!1] - bulk modulus of compression [F L!2] - bulk volume [L3] - effective stress [F L!2] (see Lecture 4 notes) - pore volume [L3] - vertical compressibility [L2 F!1] - modulus of vertical compression [F L!2] Constraints: incompressible grains, 1-D vertical compression, mass conservation for fluids and solids (4.23) When pumping from a confined aquifer, does not change, so Y Replacing partial derivatives with ordinary derivatives in Eq 4.25 and rearranging leads to Substituting into Eq 4.25 yields (4.26)