Abstract
Abstract. Creep and secondary consolidation are important phenomena in settlement caused by surface loads, but not commonly considered in land subsidence driven by groundwater extraction. To explore the role of creep in such settings, a new MODFLOW-2005 land subsidence package was developed that incorporates a creep formulation gleaned from geotechnical software. This formulation, which is based on the isotache concept, is an extension of, and incorporates the classical elastoplastic compression model of Terzaghi as a limiting case. The package is introduced, and results are presented of an application to a site in northern Jakarta. It is shown that the isotache model requires considerably higher overconsolidation levels of clays than the Terzaghi model, and that creep contributes to subsidence long after drawdown in pumped aquifers has stabilized, a phenomenon that is traditionally attributed to “hydrodynamic lag”.
Highlights
Volume loss by creep of “soft sediments” is a well-known and crucial part of the settlement caused by surface loads such as earth embankments or surcharge that is applied for construction of roads and residential areas in areas underlain by clay or peat
To be able to explore the implications of creep in aquifer system compaction and land subsidence due to groundwater exploitation, a MODFLOW-2005 land subsidence package SUB-CR was developed that incorporates an isotachebased, viscoelastic compression model that is used in certified geotechnical software for settlement modelling in The Netherlands and other countries (Kooi et al, 2018)
In the limit Cα → 0 the isotaches are compressed on the reference isotache with infinitely high creep rates above and zero creep rates below, which is the equivalent of the Terzaghi’s elastoplastic compression model (TM)
Summary
Volume loss by creep of “soft sediments” (clay, silt, peat) is a well-known and crucial part of the settlement caused by surface loads such as earth embankments or surcharge that is applied for construction of roads and residential areas in areas underlain by clay or peat. To be able to explore the implications of creep in aquifer system compaction and land subsidence due to groundwater exploitation, a MODFLOW-2005 land subsidence package SUB-CR was developed that incorporates an isotachebased, viscoelastic compression model that is used in certified geotechnical software for settlement modelling in The Netherlands and other countries (Kooi et al, 2018). This manuscript introduces the SUB-CR package and discusses how SUB-CR yields slightly modified perspectives on land subsidence due to groundwater use and its modelling than the existing packages (SUB, SUB-WT) that employ Terzaghi’s classical elastoplastic compression model
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