A simple monitoring method for observing slope movement and deformation can be performed with tilt sensors.A more efficient monitoring method, using a type of wireless communication called LPWA (Low Power Wide Area) network technology, has also recently become available. In the present study, a monitoring system was developed that combines tilt sensors and LPWA network technology for measuring the movement of slopes and sending the information through wireless communication. Firstly, radio wave propagation experiments were conducted to find the proper location for the gateway device of the monitoring system. Then, in March 2018, the developed system that consists of tilt and water-level sensors and the wireless communication of LPWA was installed at an observation site. Since the installation, the data from the tilt sensors have been successfully collected through LPWA, and a slope failure was unexpectedly observed at the observation site during the Heavy Rain Event of July 2018, which caused severe disasters, particularly from western Japan to the Tokai region. Using the data from the tilt sensors, the rainfall data, and the groundwater level, the slope failure was analysed. A site investigation was conducted, and the shear strength parameter was examined using back analysis method. In conclusion, the developed system using sensors and LPWA has continued to efficiently monitor the movement of the targeted slope, but the collection of additional data will be required to increase the reliability of the system.

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In this study, FDEM (ECZM), which is the combined finite-discrete element method (FDEM) based on an extrinsic cohesive zone model (ECZM), was improved by incorporating a novel algorithm that makes it easier to insert the cohesive elements than the conventional adaptive remeshing and a scheme to avoid the generation of dormant cohesive element, which is generated as a result of inserting a single cohesive element within the FDEM mesh. The improved FDEM (ECZM) was implemented in a self-developed 2-dimentional code, and it was first validated against a numerical experiment assuming a virtual rock. Subsequently, the proposed FDEM was applied to model the uniaxial compression and the Brazilian tests of siliceous mudstones under quasi-static loading. The results of the proposed FDEM simulations reasonably captured the trends of fracturing and stress-strain curves observed in the experiments well. The proposed scheme can also be extended to parallel computation based on general-purpose-graphic-unit (GPGPU) and 3-dimentional FDEM (ECZM) with minimal efforts.

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