Conference Paper New Techniques for Monitoring and Analyzing the Stability of Steep Cliffs against Rock Falls

Fujii, Yoshiaki  ,  Maeda, S  ,  Sugawara, T  ,  Kodama, N  ,  Miyashita, N

Mechanisms of joint opening leading to the formation of unstable rock blocks, such as thermal deformation, water-mineral reaction, pore pressure, freeze-thaw cycle, intrusion of wood roots etc. have been more or less clarified; however, the triggering mechanisms of rock falls remain to be elucidated. The problems which prevent the understanding of the mechanisms are (1) difficulty in installation of sensors to very unstable rock blocks, (2) thermoelastic deformation of sensors and attachments, (3) thermoelastic deformation of rock mass and (4) countermeasures to rock falls. Installation of a tiltmeter on the top of a very unstable rock block, correction of thermoelastic deformation of either sensors and attachments or rock mass, and long-term monitoring at a rock cliff along an abandoned road are shown as solutions to the problems. The solutions may not appear to be particularly novel, sophisticated or attractive, but the authors are convinced that they will contribute to breakthroughs in solving the listed problems. The techniques are inexpensive and worth trying.

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