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Small strain stiffness key to understanding climate impact on slope


Long-term monitoring of pore water pressure and barometric pressures could provide greater understanding of climatic impact on slope conditions, according to recent research.

“Changes in stiffness are a key a parameter in control of deformation of a slope,” said Amey geotechnical engineer Ruth Kelly during a webinar event organised by ICE Northern Ireland.

During the Management and Resilience of Infrastructure Cuttings event, Kelly presented recent research she undertook at Queen’s University Belfast and research under the Infrastructure slopes

Sustainable Management and Resilience Assessment (Ismart) project led by Newcastle University.

Kelly used an example of the Loughbrickland cutting on the A1 in Northern Ireland, that failed under construction due to groundwater under artesian pressure, to outline new techniques to offer alternative measures of small strain stiffness.

“Due to predicted climatic scenarios, the variation and magnitude of pore water pressure cycles are likely to be more severe, which places cuttings at greater risk of failure,” she said.

Kelly used multi analysis of surface waves (MASW) to study the small strain stiffness and barometric loading effects on pore pressure to quantify the compressibility at depth to deduce small strain stiffness.

According to Kelly, both methods provide new insight without call for expensive and time consuming laboratory testing.

“These techniques, as well as seismic surveys could help provide another indicator of long-term slope conditions and provide a tool for monitoring of asset condition for other aging geotechnical structures,” she said.

Kelly added that use of vertical drains at Loughbrickland was key to a reduction in the magnitude of pore water pressure cycling in the cutting. “This is of great importance for the resilience of this asset and slows the rate of degradation,” she said.

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