Experimental results of the impact pressure of debris flows in loess regions

Debris flow hazards can occur easily in loess regions, due to the particular characteristics of loessic material. Some of them have historically caused considerable damage to both the natural and the human environment. Little research has been conducted into the impact pressures caused by debris flows varying with densities and weights in loess regions. Flume experiments were conducted to estimate the impact pressures of debris flows, and the maximum impact pressure was measured. Moreover, hydrodynamic and hydrostatic models were improved by using these experimental results. Finally, after combining these results with a dimensionless analysis and Buckingham’s π theorem, the Froude number and the Reynolds number were able to be introduced in order to construct a comprehensive dimensionless equation for debris flows. The results showed that the velocity ranged from 1.23 to 3.62 m/s when the debris flow density increased from 1100 to 2300 kg/m3 and the mixture weight rose from 100 to 500 kg. The debris flow depth was between 2.7 and 13.4 cm, and the maximum impact pressure ranged from 1.23 to 28.41 kPa. In addition, the empirical parameters of hydrodynamic and hydrostatic models were modified and valued at 5.08 and 9.48, respectively, which were significantly different from the empirical parameters for earth-rock areas. Specifically, the modified hydrodynamic model and modified hydrostatic model were observed to perform very well for debris flows with comparatively high Froude debris flow numbers. The maximum dimensionless impact pressure was expressed as a power function of both the Froude number and the Reynolds number. A comprehensive maximum dimensionless impact pressure formula for debris flows was coupled with the Froude number and the Reynolds number and expressed as a power function. Results indicated that the modified model and the comprehensive approach can both be applied to the loess regions of China and can provide a better understanding of loess debris flow mechanisms, as well as feed into engineering design work and risk assessments in loess regions affected by debris flows.