Fast door-opening method for quick release of rock boulder or debris in large-scale physical model

Abstract

Study on the mitigation of debris flows and rockfalls is a very challenging topic due to complex moving and impacting mechanisms. A large-scale physical model is preferred by researchers in the study of debris flow and rockfall, because large-scale tests can duplicate major phenomena of natural geohazard events. In the design of a large-scale physical model, how to initiate or release a certain volume of debris material or a giant rock boulder is the key technical issue. In current large-scale models for debris flow research, debris material is normally released from a reservoir with a trap door located at the upper end of the flowing path. It has been found that the door-opening methods utilized in models can interfere with the motions of the generated debris flows. In this paper, a new fast door-opening method is introduced in detail. This method has been implemented in a large-scale physical model built in Hong Kong to study the impacts of rockfalls and debris flows on a flexible barrier. With the utilization of this novel door-opening method, the impact tests of rock boulders, dry granular flows, and debris flows were successfully performed. From the observations of the impact tests, the unbalanced resisting forces and the disturbance from the door were avoided. The successes of large-scale tests using different testing materials demonstrated that the new fast door-opening method can be further utilized in a physical modeling study of geohazards.