颗粒流底部摩擦模型在高速远程滑坡模拟中的运用

Application of granular friction rheology to simulation of rapid landslides with long travel distance

在运用连续理论模拟高速远程滑坡时,滑坡体底面与滑面之间的摩擦模型对模拟结果有很重要的影响,但是目前该问题仍存在争议,尚无定论。现广泛采用的理论是Voellmy底部摩擦模型,但是该模型却存在一定的不足:不能很好描述滑坡体尾部的运动;在小型滑坡的实例运用中失效;表达式缺乏具体的理论依据;参数的取得多依赖反演计算等。而颗粒流摩擦模型是一个能够反映颗粒流的摩擦机理,且已被实验室试验所验证的摩擦理论。本文引入颗粒流底部摩擦模型,并采用圣维南方程模拟高速远程滑坡。此外,通过对比Voellmy模型和颗粒流模型,发现当滑坡的深度较浅且滑速较快时,用Voellmy模型计算会出现摩擦系数无限大的情况,而用颗粒流模型计算的摩擦系数则是一有限值。我们进一步将这两种摩擦模型运用到文家沟滑坡的模拟中,发现用颗粒流模型的计算结果能更好地反映实测的滑坡体最终堆积情况。

When we use continuum theory to simulate large-scale rapid landside, the mechanism of the basal friction is still unclear. The Voellmy model is widely adopted in simulation at present, but it has some defects： 1） It can not well predict the flow process of the landslide tail. 2） It is verified that the model is not suitable to simulate small-scale landslides. 3） The model is empirical and lacks theoretical verification. 4） Some parameters in the model can only be obtained by back analysis. On the other hand, the frictional theology of granular flow can well depict the mechanism of granular flow, and it has been verified by experimental results. In this paper, we introduced the granular frictional law into the simulation of rapid large-scale landsides, and then compared the granular frictional model with the Voellmy model. Computation results show that the frictional coefficient by Voellmy model is infinite with small flow depth, but that by granular friction model has the boundary. In the end, we computed a real landslide case by adopting the two basal friction models, and found that the computed results by the granular frictional model can depict the final deposition depth of the landside better than the Voellmy model.