Predicting crack formation in clay layers in dykes

Based on experimental research, Deltares has developed a predictive indicator that enables early detection of crack formation using monitoring data — before damage becomes visible at the surface.

Our research shows that the history of suction measurements contains valuable information about the onset of cracking. This creates opportunities for timely detection and improved management of dykes and other infrastructure in which clay layers are applied.

Cihan Cengiz, senior geotechnical researcher

Increasing loads heighten the risk of cracking

Clay layers are increasingly exposed to complex loading conditions, including high water levels, upward pressure (uplift), settlement and drought. Under these conditions, they may deform and eventually crack. Once cracks occur, they act as preferential pathways for water flow, significantly reducing the barrier function of the clay layer.

Extreme weather events and rapidly changing hydrological conditions make it more challenging for dyke managers, water authorities and Rijkswaterstaat to assess cracking risks at an early stage. There is a clear need for better insight into when and how cracking occurs, as well as for measurable indicators to support assessment and monitoring.

From innovative experimental set-up to predictive model

To better understand the complex deformation and cracking behaviour of clay, Deltares developed an innovative experimental set-up in which clay plates are subjected to controlled bending.

During the experiments, various parameters were measured, including deformation, pore water pressure, suction and crack development. Three-dimensional surface scanning was used to accurately map curvature and crack patterns.

This approach enables the cracking mechanism to be isolated experimentally and linked to the internal hydraulic processes within the clay.

Images of the 44-mm-thick clay specimen during testing: (A) photograph showing the deformed and cracked shape of the specimen and (B) height map illustrating the deformation profile.

“This research provides a new physical framework in which suction history is used to explain and predict crack formation. It represents an important step towards developing predictive models based on measurable variables,” said Cengiz, the lead researcher and first author of the papers on the clay research.

Indicator enables early detection

The research shows that crack formation is not solely determined by the degree of bending. The history of suction related to pore water pressure in the clay also plays a significant role. A key finding is that crack formation can be predicted using monitoring data, even before cracks become visible at the surface.

Deltares has therefore developed a predictive indicator for crack formation based on suction history. This indicator can be used to describe and predict the initiation and development of cracks and explains more than 90% of the variation in cracking behaviour observed in the experiments.

From reactive inspection to early warning

The results enable a shift from reactive inspection to proactive monitoring and early warning. This allows asset managers to intervene earlier and manage risks more effectively, for example in dykes subjected to high water levels and uplift pressure. The findings are also relevant for landfills and other infrastructure, contributing to more reliable design and management.

Measurements within the clay layer, such as pore water pressure, provide valuable information on the risk of failure. This enables asset managers to take timely and well-informed decisions.

Cor Zwanenburg, expert geotechnics and soft soils

A clay deformation experiment in which we investigate how the clay layer on a dyke reacts under load in the Deltares’ Geo Model laboratory.

Next step: application in practice

The next step is to further refine the measurement methods and link laboratory results to field data. This will help determine how the developed indicator can be applied in practice, for example in monitoring programmes for dykes and other infrastructure involving clay layers. The results of this research have been published in: