Estimating hydraulic parameters of a heterogeneous aquitard using long-term multi-extensometer and groundwater level data

摘要: The classical aquitard-drainage model COMPAC has been modified to simulate the compaction process of a heterogeneous aquitard consisting multiple sub-units (Multi-COMPAC). By coupling Multi-COMPAC with parameter estimation code PEST++, vertical hydraulic conductivity (Kv) and elastic (Sske) inelastic (Sskp) skeletal specific-storage values each sub-unit can be estimated using observed long-term multi-extensometer groundwater level data. approach was first tested through synthetic case known parameters. Results revealed that it possible accurately estimate three parameters for sub-unit. Next, methodology applied field site located in Changzhou city, China. Based on detailed stratigraphic information extensometer data, interest subdivided into sub-units. Parameters Kv, Sske Sskp were simultaneously then compared laboratory results bulk geologic data from previous studies, demonstrating reliability estimates. Estimated ranged within magnitude 10−4 m−1, while Kv over 10−10–10−8 m/s, suggesting moderately high heterogeneity aquitard. However, deformation third sub-unit, soft plastic silty clay, is masked by delayed drainage, inverse procedure leads large uncertainty this