WP2.2: Understanding long term viscous and short term elastic soft soil deformation leading to land subsidence

Introduction
Land subsidence is one of the largest risks that many deltas around the world are facing. Two categories can be distinguished within land subsidence: Deep and shallow subsidence. Here deep concerns the consolidated part of the subsurface consisting of various types of rocks and shallow concerns the unconsolidated sediments like sand and clay (Figure 1). Since shallow land subsidence is most prominent in the soft sediments of the subsurface, like clay and peat, this PhD project focusses on these sediments with peat as the main focus.

Subsidence

Figure 1: Drivers of subsidence and the depth at which these drivers act (Minderhoud et al., 2015).

The compaction of soils, which comprises the mainly physical components of subsidence, can be separated into three time components after an additional load is added on the soil (Figure 2):

Components

Figure 2: Conceptual semilogarithmic time-strain diagram, divided into three phases of compaction (van Elderen, in preparation).

This PhD project tries to unravel the driving processes leading to the creep phenomenon. Creep deformation has been studied in the past and as a result, the phenomenon can be modelled using several geotechnical parameters. However, why this phenomenon is occurring is still up for debate. Especially for peat and other organic deposits, very little is known about the driving processes. Acquiring more knowledge on these processes can help us to better model and predict the subsidence in the future.

Research topics

For the identification of the driving processes, first an overview will be created of the present knowledge on creep, followed by an analysis of creep behaviour of peats separated by varying peat determination parameters. After the identification phase, several subjects will be investigated for their influence on the creep phenomenon:

Staff

This PhD project started on the 13th of January, 2021 and is carried out by Pepijn van Elderen MSc. and is supervised by Dr. Esther Stouthamer, Dr. Gilles Erkens and Prof. Dr. Hans Middelkoop.
For questions or requests related to this project, please contact Pepijn van Elderen MSc. at p.vanelderen@uu.nl.

Reference for figure 1: Minderhoud, P. S. J., Erkens, G., Pham, V. H., Vuong, B. T., & Stouthamer, E. (2015). Assessing the potential of the multi-aquifer subsurface of the Mekong Delta (Vietnam) for land subsidence due to groundwater extraction. Proceedings of the International Association of Hydrological Sciences, 372, 73-76.