都(江堰)汶(川)公路泥石流危险性评价及活动趋势

Hazard Assessment of Debris Flows and their Developing Trend along Dujiangyan-Wenchuan Highway

泥石流危险性评价是合理制定泥石流防治方案和进行泥石流防治工程设计的必要前提。板子沟、桃关沟、登基沟和彻底关沟是岷江两岸的大型泥石流沟,严重威胁着沟口公路桥梁的安全。危险性评价结果表明,登基沟、桃关沟和板子沟均为具有高度危险的泥石流沟,危险度分别为0.74、0.69和0.68,高度危险的泥石流沟可造成重大灾难和严重危害。彻底关沟泥石流危险度为0.50,属中度危险。板子沟、桃关沟和彻底关沟均为低频率泥石流或高含沙洪水,平均20～50年发生一次;登基沟泥石流(包括高含沙洪水)发生频率稍高,平均5～10年发生一次。研究表明,如果板子沟和桃关沟内人工采石的强度能得到有效控制,没有明显迹象表明上述4条沟的泥石流活动会有增强的趋势。

Hazard assessment of debris flow is the necessary prerequisite for the control schemes and project designs of debris flows. The four large-scale debris flow gullies of Banzi, Taoguan, Dengji and Chediguan distributed along Minjiang river greatly threaten the safety of the highway bridges cross the gullies. The debris flow hazard assessment results show that Dengji, Banzi and Taoguan gullies are of high hazardousness with hazard values of 0.74, 0.69 and 0.68 respectively, which may cause large disasters and huge damages. Chediguan gully has hazard value of 0.50, belonging to moderate hazardousness. The debris flow gullies of Banzi, Taoguan and Chediguan generate low frequency and low viscous debris flows or hyper-concentrated flows with an average interval of 20～50 years. Dengji gully has a high frequency of occurrence of debris flows or hyper-concentrated flows with an average interval of 5～10 years. Once the quarries in Banzi and Taoguan gullies have been stopped, there are no evidences indicating that there might be an increasing trend of debris flow activities in these gullies.