Landslide Case Histories Research Articles

Phased Reconnaissance Approach to Documenting Landslides following the 2016 Central Italy Earthquakes

The 2016 Central Italy earthquake sequence caused numerous landslides over a large area in the Central Apennines. As a result, the Geotechnical Extreme Events Reconnaissance Association (GEER) organized post-earthquake reconnaissance missions to collect perishable data. Given the challenging conditions following the earthquakes, the GEER team implemented a phased reconnaissance approach. This paper illustrates this approach and how it was used to document the largest and most impactful seismically induced landslides. This phased approach relied upon satellite-based interferometric damage proxy maps, preliminary published reports of observed landslides, digital imaging from small unmanned aerial vehicles (UAVs), traditional manual observations, and terrestrial laser scanning. Data collected from the reconnoitered sites were used to develop orthophotos and meshed three-dimensional digital surface models. These products can provide valuable information such as accurate measurements of landslide ground movements in complex topographic geometries or boulder runout distances from rock falls. The paper describes three significant landslide case histories developed and documented with the phased approach: Nera Valley, Village of Pescara del Tronto, and near the villages of Crognaleto and Cervaro.

Back-analysis of geophysical flows using three-dimensional runout model

Predicting the mobility and delineating the extent of geophysical flows remains a challenge for engineers. The accuracy of predictions hinges on the reliability of input parameters of runout models. Currently, limited field data for landslide case histories are available for benchmarking the performance of runout models. Key rheological parameters, such as the equivalent internal friction angle, cannot be measured directly using laboratory experiments and must instead be determined through back-analyses. A series of dynamic back-analyses was carried out for notable landslide case histories in Hong Kong, accounting for the effects of pore-water pressure on the equivalent internal friction angle, using a three-dimensional finite-element mobility model. The recorded and simulated run-out distances, as well as lateral spreading, were compared. Results reveal that the back-analysed equivalent internal friction angles resulting from open-hillslope failures and from channelized geophysical flows range from 25° to 30° and 15° to 20°, respectively. This is attributed to incised geophysical flow channels having an elevated water head and higher degree of saturation compared to open-hillside slope surfaces, wherein the induced elevated pore-water pressure profoundly lowers the equivalent internal friction angle. The back-calculated values may be useful for finite-element-based design of mitigation measures.

A Critical-Line-Based Predictive Model for Landslides

This paper developed a critical-line-based method for predicting the occurrence of landslides using two rainfall indices, the rainfall intensity and the accumulated rainfall, based on four landslide case histories recorded in a county. Specifically, the rainfall records of the four cases were used to compute the 60-minute rainfall intensity and accumulated rainfall prior to the occurrence of landslides. Although the meteorological and geological conditions as well as other crucial factors are not considered in the development of the intended model, the analysis results indicated that the developed critical-line-based predictive model can reasonably identify the boundary between occurred and non-occurred zones. The developed model has the potential to be a useful tool for predicting the occurrence of landslides according to the rainfall conditions.

Sheeting Joints: Characterisation, Shear Strength and Engineering

Sheeting joints are extensive fractures that typically develop parallel to natural slopes. Embryonic sheeting joints initially constitute channels for water flow and then become the focus for weathering and sediment infill accompanied by progressive deterioration and dilation. Slabs of rock fail along them periodically because of their adverse orientation and long persistence. They are however rough and wavy and these characteristics contribute highly to their shear strength and improve their stability. This paper reviews several landslide case histories and on the basis of these provides guidelines for characterising sheeting joints and determining their shear strength. Engineering options for stabilising sheeting joints in natural and cut slope configurations are then examined with reference to case examples.

Case history of landslide in Osaka soft rock group - Geological conditions and failure mechanism -

Case history of landslide in Osaka soft rock group - Geological conditions and failure mechanism -