Conventional equipments for rock fall monitoring require a repair of the system after detection of rock fall events since falling rocks give them damage. To overcome such shortcoming, a new system using photoelectric sensors was developed in this study. This technique allows the system to be functioned without any repair since the sensors can detect a rock fall without any contact with rock. Reliability of this system was checked out through various tests both in a laboratory and in a field. The test results showed that the system was effectively applicable to detecting rock fall events and useful for gathering and analyzing various technical data. It is also capable for roughly estimating the size or moving direction of rocks through comparing digital images captured by a camera.


A large number of slopes have been constructed in roadways or railways in Korea. Slope failures or rock falls due to a heavy rain, typhoon or earthquake have frequently occurred, resulting in a loss of humans or properties. In fact, 121 slopes at national roads were damaged in form of sliding or local failure by the typhoon, Rusa in 2002 (Bae et al., 2008). Even though such slope failures may be recognized as a natural disaster, resulting damages could be mitigated by appropriate measures. A slope management system combined by IT technologies is an example. In fact, such equipments have been recently installed at several slopes in express ways or railroads. Most of them employ wire sensors or tilt meters to detect a tension change or a break of protection net when a rock falls on it (Huh et al., 2003). Therefore, they can be exclusively used in slopes where a protection net is installed, and should be repaired in order to be reused after rock fall or slope failure occurred.

To overcome such defects of the conventional monitoring equipments, a new system that does not need a protection net and repairing works was developed in this study. The system employs photoelectric sensors to detect falling rocks without any contact, as well as a camera to capture images at the moment of rock fall. Its reliability was checked out through various tests both in a laboratory and a field. The new system may be usefully applied in a semi-permanent way to rock slopes where it is difficult to be accessed, since it does not need to be repaired.

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