黄河下游重塑黏性土抗冲特性试验

黄河下游河床存在典型的分层结构,不同部位对水流抗冲性不同,抗冲性极强的"胶泥层"对河势演变具有重大影响。通过对黄河下游花园口附近黏性土进行取样,开展了黄河下游河岸黏性土起动冲刷的水槽试验。分析了起动切应力随干密度的变化情况,建立了干密度、含水率与淤积历时的关系,拟合了黏性土侵蚀系数与起动切应力的关系式,结果表明:黏性土起动切应力随干密度的增大而增大,两者呈幂函数关系;当淤积历时较短时,黏性土干密度(含水率)随淤积历时的增大而增大(减小),两者呈对数函数(指数函数)关系;黏性土侵蚀系数随起动切应力的增大而减小,两者呈幂函数关系;同时研究发现,黏性土起动切应力与黏粒含量相关,相同干密度条件下,黏粒含量越高起动切应力越大;黏性土侵蚀系数与该土体的黏粒含量、土体结构相关,黏粒含量越高侵蚀系数越小,相应的其抗冲性越强。

Experimental study on the anti2scourability of remolded cohesive soil in the lower reaches of the Yellow River

There is a t ypical str atified st ructur e in the lower r eaches of the Yellow Riv er. Different pa rts of the riv er have differ2 ent anti2scourability. The "clay layer" w ith strong ant i2sco ur ability has a signif icant impact on the riv er r eg ime. A flume test of sta rting erosio n o f clay was carried out based on the cohesiv e so il near H uayuanko u in the lower reaches o f the Yellow Riv er. The v ariat ion o f starting shea r st ress w ith dr y density w as analy zed, and the r elationship betw een dry densit y, w ater content and deposition durat ion was established. The relationship betw een starting shear str ess and ero sion coefficient of cohesive so il w as also fitted. The results showed that the starting shear str ess o f co hesive soil increased w ith the increase of dry density, and the relat ionship betw een them was pow er functio n. When the siltatio n duratio n w as sho rt, the dry density ( wat er content) of cohe2 siv e so il increased ( decreased) w ith the increase o f t he silt ation duration, and the relatio nship betw een them w as log arit hmic function ( exponent ial function) . The ero sion coefficient of cohesive soil decr eased w ith the incr ease o f starting shear stress, and the r elationship between them was pow er function. Simultaneously , it w as found that the starting shear stress of cohesive so il relat ed to t he cohesive co ntent, and under the same dry density conditio n, the higher the cohesive co nt ent was the gr eater the sta rting shear str ess. The erosion co efficient of cohesiv e so il w as related to the cohesiv e content and str ucture of the so il. T he higher the cohesive content, the smaller the ero sion coefficient, and the str onger the anti- sco ur abilit y.