New Permeable Structure for Controlling Debris Flows in the Wenjiagou Gully

Aimed to control debris flows more effectively, we attempt to develop a new structure called a sloping roof grill dam, which consists of guidance walls, separation grills and lateral deposit areas. A series of flume tests were performed to verify the function of this new structure, focusing on the trapping efficiency (), deceleration efficiency () and coarse-fine sediment separation extents () under different conditions of structure and debris flows. Experimental results show that both the trapping and deceleration efficiency increase with a decrease in permeability, whereas the separation extent shown the opposite effect. Multiple regression analysis indicates that and are linearly dependent on the permeability, deceleration efficiency and magnitudes of debris flow. In addition, an increase in beam gap can lead to an increase in the impact area downstream for the debris flow after the control of the structure. Finally, a two-level installation of the structure is tested to determine whether there is an enhancement of the debris control, which indicated that although the trapping effect of the two-level structure is considerably greater than that of a single-level structure (2.11 times at maximum), the separation extent of the two-level structure is not distinct and may be even lower.