Author: Christopher Temple

CONGRATULATIONS GLORIA!!

Congratulations to Gloria Castro! Gloria successfully her PhD thesis, Corrosion of Buried Metals: Soil Texture and Pore Fluid Saturation on December 6. Her committee members were Dr. Shehab Ahmed, Dr. Husam AlShareef and Dr. Susan Burns (Georgia Tech, USA). Gloria was supervised by Dr. Santamarina.

Abstract

The corrosion of buried metals affects geosystems that range from pipelines and nuclear waste disposal to reinforced concrete and archeology. Associated costs exceed 1 trillion dollars per year worldwide, yet current classification
methods for soil corrosivity have limited predictive capacity. This study-triggered by the recent development of the Revised Soil Classification System RSCS- seeks to identify the critical soil and environment properties that can
improve the prediction of buried metal corrosion.

The experimental studies conducted as part of this research recognize the inherently electro-chemo-transport coupled nature of buried metal corrosion and places emphasis on phenomena that have been inadequately captured in previous
studies, such as the effect of soil texture and fines plasticity, partial saturation, moisture cycles, and conditions in Sabkha environments. The comprehensive experimental program involves detailed protocols for specimen preparation, advanced visualization (X-ray micro-CT), corrosion residual characterization (XRD), and detailed image analyses of extracted coupons. Experiments include both laboratory mixtures and a wide range of field specimens gathered throughout Saudi Arabia; furthermore, field observations expand soil assessment to native environmental conditions. Theoretical analyses based on mass conservation and electrochemical phenomena complement the
experimental study.

Experimental and analytical results lead to new soil corrosivity assessment guidelines. Results show the relevance of the sediment pore fluid saturation, sediment texture, air and water connectivity, active corroding areas, the effect of environmental cycles on buried metal corrosion and evolving backfill contamination.

COP26 regional report and Carlos Santamarina

COP26 has highlighted the critical role of the Arabian Peninsula in addressing climate change towards a net-zero future. Professor Carlos Santamarina together with Samuel Short and Emily Shuckburgh (University of Cambridge), and Annalisa Molini and Luiz Friedrich (Khalifa University of Science and Technology) contributed to the development of the regional profile for the region ahead of the conference. Read the full report here.

Congratulations Clara!

Congratulations to Clara Modenesi who successfully her PhD thesis Hot and Cold Seeps in the Red Sea: Surface and Subsurface Manifestations on September 16. Her committee members were Dr. Abdulkader Afifi, Dr. Volker Vahrenkamp, Dr. Daniele Daffonchio and Dr. Joe Cartwright (University of Oxford, UK). Clara was supervised by Dr. Santamarina.

Abstract

Cold and hot seeps signal active subsurface processes. This thesis documents the study of geological phenomena and features observed in the Red Sea in association to (1) hot hydrothermal and (2) cold hydrocarbon seeps. Hydrothermal activity promotes the formation of hot and stratified brine pools within deeps along the central trough of the Red Sea. Conductivity, temperature and time-lapse photography help identify the unique processes that emerge within these pools. Hydrothermal sediments nucleate and grow within stratified brines. Their sedimentation -together with Red Sea background-pelagic grains- detects density contrasts at layer interfaces, is affected by salinity gradients (diffusiophoresis), favors aggregation as grains fall into higher salinity fluids, and grains/aggregates are transported by convective currents within the double-diffusive convective system. Stratified layers will be affected by tailings disposal from deep-sea mining operations. Hydrothermal metalliferous sediments accumulate within deeps along the central trough of the Red Sea, such as in the Atlantis II and neighboring deeps. The sediment column records distinct combinations between background-pelagic and hydrothermal sedimentation. A comprehensive laboratory characterization study shows that these metalliferous sediments exhibit exceptional properties when compared to sediments worldwide: from high specific surface area and specific gravity to very open fabrics and high compressibility. These unique properties affect acoustic characterization and sampling operations, laboratory testing, and mining engineering, from separation and enrichment processes to environmental analyses and tailings disposal operations. Cold hydrocarbon seeps are evident at multiple locations across the Red Sea and manifest through hard crusts, oil and gas flares in the water column, oil slicks at the surface and oil impregnations within the sediment. This study explores in detail the emergence of two unique features associated to active hydrocarbon seeps: authigenic precipitates within seafloor sediments and carbonate chimneys that rise above the seafloor. The research approach includes imaging (X-Ray μ-CT, SEM), compositional characterization (XRD, EDS, thin sections, ICP-OES) and sediment characterization. Results show that hydrocarbon escape through shallow sediment layers opens discontinuities where grain-displacive, hollow sulfur nodules form, while the host sediment becomes depleted of carbonates. Chimneys result from bio-chemo-hydraulically coupled processes and exhibit a characteristic layered structure that tends to preserve internal flow channels during active fluid escape and growth.