A New Overflow Number for Analyzing and Designing Dual Rigid Barriers with Basal Clearance

Multiple barriers with basal clearance are usually adopted in engineering practice to mitigate large volumes of debris flows. This approach allows for sufficient discharge and minimizes the need for cleaning and maintenance over the service life of the barriers. Despite the effectiveness, the design of basal clearance is still based on empirical methods, which can lead to uncertainty in safety. In this study, a new dimensionless overflow number Nof is proposed for designing dual rigid barriers with basal clearance and validated with physical and numerical results. The physical tests were conducted using a 28 m long flume model. A finite element model calibrated using the physical test results is utilized for numerical parametric study to investigate the effects of basal clearance on debris flow impact force against dual barriers. Physical and numerical results reveal that Nof can serve to determine whether the impact force on the second barrier is governed by basal discharge or overflow from the first barrier. A threshold value of Nof=1 can be used to design dual barriers with basal clearance to achieve the lowest impact force on the second barrier. The proposed Nof also enables engineers to predict the impact force on the second barrier by only considering the impact force from basal discharge.