title: Monitoring and behavior of unsaturated volcanic pyroclastic in the Metropolitan Area of San Salvador, El Salvador.
abstract: Field monitoring and laboratory results are presented for an unsaturated volcanic pyroclastic. The pyroclastic belongs to the latest plinian eruption of the Ilopango Caldera in the Metropolitan Area of San Salvador, and is constantly affected by intense erosion, collapse, slab failure, sand/silt/debris flowslide and debris avalanche during the rainy season or earthquakes. Being the flowslides more common but with smaller volume. During the research, preliminary results of rain threshold were obtained of flowslides, this was recorded with the TMS3 (a moisture sensor device using time domain transmission) installed in some slopes. TMS3 has been used before in biology, ecology and soil sciences, and for the first time was used for engineering geology in this research. This device uses electromagnetic waves to obtain moisture content of the soil and a calibration curve is necessary. With the behavior observed during this project is possible to conclude that not only climatic factors as rain quantity, temperature and evaporation are important into landslide susceptibility but also information of suction-moisture content, seepage, topography, weathering, ground deformation, vibrations, cracks, vegetation/roots and the presence of crust covering the surface are necessary to research in each site. Results of the field monitoring indicates that the presence of biological soil crusts a complex mosaic of soil, green algae, lichens, mosses, micro-fungi, cyanobacteria and other bacteria covering the slopes surface can protect somehow the steep slopes reducing the runoff process and mass wasting processes. The results obtained during the assessment will help explaining the mass wasting problems occurring in some pyroclastic soils and its possible use in mitigation works and early warning system.
authors.affiliation: Department of Geotechnics, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague 6, Czech Republic ; Oficina de Planificación del Área Metropolitana de San Salvador (OPAMSS), Diagonal San Carlos 15, Avenida Norte y 25 Calle Poniente Col. Layco, San Salvador, El Salvador.
authors.forename: José Alexander
authors.initials: JA
authors.lastname: Chávez
authors.affiliation: Departamento de Geotecnia, Facultad de Ingeniería y Arquitectura, Universidad de El Salvador, Ciudad Universitaria, Final Av. Héroes y Mártires del 30 de Julio, San Salvador, El Salvador.
authors.forename: José
authors.initials: J
authors.lastname: Landaverde
authors.affiliation: Facultad de Ciencias Agronómicas, Universidad de El Salvador, Ciudad Universitaria, Final Av. Héroes y Mártires del 30 de Julio, San Salvador, El Salvador.
authors.forename: Reynaldo López
authors.initials: RL
authors.lastname: Landaverde
authors.affiliation: Department of Soil Science and Soil Protection, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6, Czech Republic.
authors.forename: Václav
authors.initials: V
authors.lastname: Tejnecký
keywords: Flowslide; Landslide; Pyroclastic; Soil moisture sensor; Suction; Tierra Blanca Joven; Unsaturated