Quantifying the strength of debris flow and analyzing the vulnerability of a novel grille dam for debris flow

Check dams are often damaged by boulder impacts. Thus, this paper proposes a novel ground-anchored string beam debris flow grille dam. Finite element software analyses showed that the novel structure outperformed the conventional grizzly dam. Reliability-based vulnerability analyses can evaluate the load-carrying capacity of check dams. The physical vulnerability of check dams to debris flows is defined as the potential damage to dams for a given debris flow intensity. Consequently, four damage states of novel structures are defined, namely, slight, moderate, heavy, and complete damage. The boulder radius (R) and flow velocity (V) were found to have the greatest effect on the failure probability using the random forest regression method. R or V single strength indicator is not sufficient to indicate novel structural damage failure probability. The impact forces V^1.2R² and V²R³ both well quantify the impact strength of the boulders. However, when considering the depth of the debris flow (H), the impact force HV^1.2R² is more appropriate to quantify the impact strength of the boulders. The fragility curve of the novel structure was obtained using the modified elastic impact force model. The novel structural failure mechanism is dominated by bending damage. The flow depth (H) affects the exceeding probability of complete damage significantly. The optimization of the novel structure is given based on the vulnerability analysis. The damage mechanisms of novel and conventional structures were analyzed. The results indicated that conventional structures exhibited the highest probability of overturning. This is the most unfavorable situation. It is further indicated that the incorporation of string beams and prestressed anchors into the novel structure can markedly enhance its performance.