Drawdown of urban drain trenches triggering 2-D transient seepage in soil massifs subject to managed aquifer discharge: sandbox experiments, analytical and HYDRUS2D modeling

Shahad Al-Yaqoubi*, Ali Al-Maktoumi, Yurii Obnosov, Anvar Kacimov

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Managed Aquifer Discharge (MAD) through trenches lowers the water table of ‘shallow perched aquifers’ in urban areas (Muscat-Oman). Drawdown of the water table in periodic trenches or a single trench is experimentally studied in a sandbox, and modelled numerically (by HYDRUS2D) and analytically. Evaluation of transient flow fields of pore pressure and hydraulic gradients is necessary for assessing the stability of trench slopes to seepage-induced erosion. A controlled emptying of trench’s water level is examined. An analytical solution is obtained for an unconfined seepage at an early stage of drainage. Numerical simulations are conducted for early and late stages of seepage towards a partially filled trench in soils with capillarity. For a steady-state Darcian flow limit, comparisons of HYDRUS results with the Charny analytical formula for capillarity-free soils are done. The flow rates, isobars, isotachs and streamlines are determined, with assessment of zones of high hydraulic gradients susceptible to seepage erosion.

Original languageEnglish
JournalUrban Water Journal
DOIs
Publication statusAccepted/In press - 2022
Externally publishedYes

Keywords

  • boundary-value problem and the keldysh-sedov formula
  • complex potential-conformal mappings
  • HYDRUS2D simulations
  • isobars-isohumes-isotachs-streamlines
  • sandbox drawdown experiments
  • Urban drainage by trenches

ASJC Scopus subject areas

  • Geography, Planning and Development
  • Water Science and Technology

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