In the last 15 years, a series of catastrophic flowslides involving pyroclastic unsaturated soils has caused severe damage and a number of fatalities in the Campania region (southern Italy), where flowslides occur within the pyroclastic cover resting on the limestone massif. Rainwater infiltration is considered to be the triggering mechanism that leads to slope failure by reducing matric suction in unsaturated soils, hence reducing its shear strength. Therefore, knowledge of the groundwater regime is an important factor for slope stability evaluation as well as for predicting slope conditions prone to landslides triggered by water infiltration. The quality of prediction can be greatly improved if observations from in situ monitoring are available. This paper describes the results of an ongoing experimental research project on flowslides based on monitoring a test site in a typical geological environment in western Campania. The site was selected to carry out extensive laboratory and in situ testing. The test programme consisted of field monitoring of climatic conditions, matric suction and volumetric water content. The instrumentation and measuring techniques used in this research are systematically described to provide an example of good practice for use at other sites with similar features. With the use of the collected data, the seasonal fluctuations of the hydraulic regime in the subsoil may be observed and the critical periods for flowslide triggering identified. Measurements of matric suction from the test site are interpreted and directions of groundwater flow vectors in the subsoil are shown. Moreover, once the current state of the subsoil is known, slope stability conditions can be calculated using a simple infinite slope model that would provide continuously updated information on the current slope safety level

In this paper, we show some recent experimental applications of Brillouin optical time-domain analysis (BOTDA) based sensors for geotechnical monitoring. In particular, how these sensors can be applied to detecting early movements of soil slopes by the direct embedding of suitable fiber cables in the ground is presented. Furthermore, the same technology can be used to realize innovative inclinometers, as well as smart foundation anchors

Rainwater infiltration is the mechanism that leads or predisposes unsaturated pyroclastic slopes to failure by reducing matric suction and hence reducing the shear strength. Therefore, groundwater flow analysis is an important tool to investigate slope stability as well as predict conditions caused by heavy rainfall. Analysis and prediction quality can be greatly improved by in situ monitoring. In this framework, this paper describes the results of an ongoing experimental research project on mudflows, based on monitoring of a test site in a typical geological environment in western Campania. The site was selected to carry out extensive laboratory and in situ experimentation, consisting of field monitoring of climatic conditions, matric suction and water content. The suction data span about 4 years, while water content data cover about 2 years. Considered together, these data allow clear identification of seasonal fluctuations of the hydraulic properties in the subsoil, while giving interesting information on the hysteretic hydraulic behaviour of pyroclastic soils. Suction measurements were elaborated to obtain groundwater heads in the subsoil and then equipotential lines and flow vectors.

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The experimental technique proposed in the paper was designed to rapidly and reliably determine both the water retention curve and the permeability function of undisturbed natural pyroclastic soil samples. The technique was developed in the framework of an experimental research project on mudflows in pyroclastic soils in the southern Italian region of Campania (Italy). Grain-size distribution and void ratio of the particular pyroclastic soils suggested investigation of the hydraulic behavior for matric suction values in the range between 0 and 100 kPa. Our experimental technique consisted of a sequence of testing phases to be conducted on a single undisturbed soil sample: A constant head permeation test, a forced evaporation test, and finally a drying test in a pressure plate apparatus. Interpretation of the experimental data was based on inverse modelling and allowed both water retention curves and permeability functions to be determined. The six parameters of the Mualem–van Genuchten model were adopted to describe the hydraulic behavior of the tested soils. Each testing phase supplied experimental data to be used in the interpretation procedure: The permeation phase provided a matching data point for the permeability function near saturation; the forced evaporation test was related to the hydraulic behavior for matric suction values ranging from a few kPa to less than 80–90 kPa (i.e., mini-tensiometer functioning range); and the drying steps in the pressure plate apparatus provided information about the retention properties for matric suction values up to 1 MPa. The results shown in the paper clearly confirm the goodness of the experimental design and the interpretation procedure.