本文選題：基巖暴露　切入點：沙卵石覆蓋　出處：《工程科學與技術》2017年S1期

【摘要】：山區(qū)河流不同河段的河床形態(tài)常處于基巖暴露與沙卵石覆蓋的相間變化中。野外調查發(fā)現,至少在青藏高原與四川盆地過渡帶,不少河流出現坡度大而沙卵石覆蓋多,坡度小而基巖暴露多的現象。為了研究該反常規(guī)律,以岷江二級支流隴西河為例,進行多次野外觀測與數據采集,通過提取流域地形數據,得到并分析其干流沿程剖面,并結合已有的室內水槽試驗研究結果,進一步說明床面沙卵石的運動情況與分布特性,得到以下結論:隴西河流域巖性以砂巖為主,干流從上游向下游依次出現陡、緩、陡、緩交替的4段,平均坡度依次為8.1%、0.2%、6.2%和1.2%;較陡的兩段全部沙卵石覆蓋,較緩的兩段全部基巖暴露。產生這種現象的原因:一是較陡段泥沙顆粒通過兩側山體崩塌滑坡側向補給,床面大尺寸漂石與周圍的較細顆粒會逐漸形成相對穩(wěn)定且水流阻力大的自鎖結構,且床面粗糙,有助于提高床面抗沖刷性,抑制基巖的暴露,因此導致輸送到下游較緩段的輸沙率很低;二是砂巖顆粒巖性較軟,少量被輸移到下游的顆粒容易破碎成更小的顆粒,更容易被輸移,使得較緩段基巖暴露現象突出。較陡段被沙卵石覆蓋,將有效抑制窄深處基巖河床的侵蝕下切速率,從而進一步影響相關流域地貌的演化,如增加河流襲奪的機率。
[Abstract]:The river bed morphology of different reaches of mountain rivers is often in the interphase change of bedrock exposure and sand pebble coverage. Field investigation shows that at least in the transitional zone between the Qinghai-Tibet Plateau and Sichuan Basin, many rivers have a large slope and more sand and pebble cover. In order to study this anomalous law, taking Longxi River, a secondary tributary of Minjiang River, as an example, many field observations and data collection were carried out, and the main stream profile along the river was obtained and analyzed by extracting the topographic data of the basin. Combined with the experimental results of indoor flume, the movement and distribution characteristics of bed sand pebbles are further explained, and the following conclusions are obtained: the lithology of Longxi River basin is dominated by sandstone, and the main stream is followed by steep, gentle and steep from upstream to downstream. The average slope of the four sections alternated slowly is 8.2% and 1.2% respectively; the two steeper sections are covered with all sand and pebbles, and all the bedrock in the slower two sections are exposed. The causes of this phenomenon are as follows: first, the sediment particles in the steeper section are recharged laterally through the two sides of the landslide, The self-locking structure with relatively stable flow resistance and rough bed surface will be gradually formed between the large-size drift stone and the surrounding fine particles, which will help to improve the scour resistance of bed surface and restrain the exposure of bedrock. As a result, the transport rate of sand to the slower section of the lower reaches is very low. Second, the sandstone grain lithology is softer, and a small number of particles transported downstream are easily broken into smaller particles and transported more easily. The relatively steep section is covered with sandy pebbles, which will effectively restrain the erosion rate of the bedrock bed in the narrow depth, thus further affect the geomorphological evolution of the relevant watershed, such as increasing the probability of river capture.
【作者單位】： 四川大學水力學與山區(qū)河流開發(fā)保護國家重點實驗室水利水電學院;
【基金】：國家自然科學基金資助項目(51509172;51539007;51609160) 國家重點研發(fā)計劃資助項目(2016YFC0402302) 國家“十二五”科技計劃資助項目(2012BAB05B02) 四川大學青年啟動基金資助項目(2015SCU11046)
【分類號】：TV143
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本文編號：1661658