Report of Investigations--KGS

Abstract

Complex spatial and temporal variables control the movement of water through colluvial soils in hillslopes. Some of the factors that influence soil-moisture fluctuation are soil type, thickness, porosity and permeability, and slope morphology. Landslide-characterization and field-monitoring techniques were part of a method to connect hydrologic and geotechnical data in order to monitor long-term hydrologic conditions in three active landslides in Kentucky, establish hydrologic relationships across the slope, and analyze specific soil-water relationships that can predict shear strength. Volumetric water content, water potential, and electrical conductivity were measured between October 2015 and February 2019. The duration and magnitude of drying and wetting within the soil varied for each slope location and soil depth, suggesting that differences in slope morphology, soil texture, and porosity influence the water-infiltration process, as well as shear strength and general landslide dynamics. The parameters measured and soil-water relationships were also compared to rainfall and slope movement at one of the landslides.

The method used to acquire hydrologic data was cost-effective, and the field techniques may be useful for subsequent projects, such as slope-stability assessments and landslide-susceptibility modeling. Hydrologic parameters, volumetric water content, and water potential are pertinent to investigating the stability of landslides, which are often triggered or reactivated by rainfall. These methods can be used to support landslide-hazard assessment and improve our understanding of the long-term influence of moisture conditions in hillslope soils.

Publication Date

2020

Series

Series XIII

Report Number

Report of Investigations 11

Digital Object Identifier (DOI)

https://doi.org/10.13023/kgs.ri11.13

Notes

Statement of Benefit to Kentucky

Hillslope soil moisture is one of many important factors that influence landslide occurrence. Field investigations that monitor soil moisture, rainfall, soil-water relationships, and landslide movement can contribute to a better understanding of conditions that lead to landslides. This report summarizes field techniques and research methodology to connect soil properties, soil mechanics, and geology, and serves as a sound scientific basis for broad landslide hazard characterization, as well as future slope-stability assessments.

© 2019 University of Kentucky

Funding Information

We would like to thank the Kentucky Geological Survey for financial and logistical support, especially Junfeng Zhu and Steve Webb of the KGS Water Resources Section. Terracon Consultants Inc. also provided financial support, as well as collaboration on geotechnical aspects of the project, through the Terracon Foundation. Many colleagues provided field and technical assistance: faculty, staff, and graduate students in the University of Kentucky Department of Earth and Environmental Sciences (special thanks to Peter Idstein, academic lab coordinator); Francis Ashland of the U.S. Geological Survey Landslide Hazards Program, whose advice about landslide monitoring and field instrumentation was invaluable and whose funding allowed for purchase of field instruments; and Glynn Beck and Junfeng Zhu of the KGS Water Resources Section, whose technical reviews improved the content and clarity of the report.

Related Content

Crawford, M.M., Bryson, L.S., 2021. Landslide soil hydrology data for three landslides in Kentucky: Kentucky Geological Survey Research Data, https://doi.org/10.13023/kgs.data.2021.03.

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