【摘要】 川滇两省某些泥石流拦沙坝基础遭泥石流掏蚀、侧蚀后,造成悬空,以至溃坝。因此拦沙坝基础埋深问题值得引起重视,这应考虑如下几点:1.泥石流冲刷坑深度;2.沟床纵坡的变动,含沟床纵坡的变缓和变陡;3.局部侵蚀基准面(主支沟汇合处)的下降,含汇合处改至主沟下游而呈现的相对下降和主沟下切而使汇合处下降。这些造成拦沙坝基础出露深度0.7—7.0米,基础埋深至少要考虑此值。更多还原

【Abstract】 Some Sediment dam foundations were surpended and even broken under scouring and lateral erosion from debris flows. During 1973-1976, 65% in sediment dams broken by debris flows in Sichuan Province suffered from hanging of foundation. So the burial depth of sediment dam foundation should be paid attention. The following aspects should be considered.1.The depth of debris flow scouring hole h1h1 is decided by dam height Z.unit discharge of debris flow q (Table 1) and the natures of debris flow deposits at dam foundation, etc. In Hunshui Ravine of Yingjiang County,Yunnan Province,there is 1# sediment dam,Z = 6. 0m,the burial depth of the foundation is only 2. 0m, the dam body is on old debris flow deposits. When the debris flow passes,q=12-16m3/(s·m), h1=3. 0-5. 0m,the dam body will be in denger. In the debris flow gullies at Heisha River of Liangshan,Sichuan Province,if Z-5. 0-10. Om,on old debris flow deposits hi would be 1/2 of Z,on new debris flow deposits h1 would be 2/3 of Z.2.The variation of the gully-bed gradient1)The gully-bed gradient at the lower reaches of sediment dam will get gentle while the grain size is fine. After the gradient getting gentle,the emerged depth of sediment dam foundation h2=/",(i0-i1),where L is the gully, length from local erosion basis (the junction of main and branch gullies) to dam sitej i0 is original gully-bed gradients i1 is the gully-bed gradient to be flatted (Fig. 1). During 1980-1984,more than 20 sediment dams had been built in the debris flow gully at Sanjiacun of Lianghe County,Yunnan Province. i0=15-20%,i1 = 5-7%. Among them,4 sediment dams.A2 = 0. 6-0. 7m. 2)After channel cutoff,the gully-bed gradient will be more steep. For example,in this caes,a sediment dam in Jiangjia Ravine of Dongchuan,Yunnan Province was broken while h2= 4. 0m.3.Lowering of the local erosion basis (the junction of main and branch gullies)1)The junction will get to lower relatively, if the debris flow channel on the accumulated fan was turned to the lower reaches of the main gully. The altitude of the old junction of Hunshui Ravine is at 968m; a large debris flow in 1974 turned the junction to the lower reaches of the main gully,the altitude of new junction is at 958m (Fig. 2). Headward erosion is up to 1# sediment dam, h2 = 6. 0-7. 0m. 2)The junction lowered because the main gully cut down. For example, at the junction of Hunshui Ravine, it lowered from 961m in 1978 to 953m in 1986 (Table 2). Headward erosion is to a flow-measuring flume,h2=6. 0m.For reason given,the discussed problems will help to correctly determine the burial depth of sediment dam foundation.更多还原