本文選題：基巖暴露　切入點(diǎn)：沙卵石覆蓋　出處：《工程科學(xué)與技術(shù)》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(diào)查發(fā)現(xiàn),至少在青藏高原與四川盆地過(guò)渡帶,不少河流出現(xiàn)坡度大而沙卵石覆蓋多,坡度小而基巖暴露多的現(xiàn)象。為了研究該反常規(guī)律,以岷江二級(jí)支流隴西河為例,進(jìn)行多次野外觀(guān)測(cè)與數(shù)據(jù)采集,通過(guò)提取流域地形數(shù)據(jù),得到并分析其干流沿程剖面,并結(jié)合已有的室內(nèi)水槽試驗(yàn)研究結(jié)果,進(jìn)一步說(shuō)明床面沙卵石的運(yùn)動(dòng)情況與分布特性,得到以下結(jié)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(xiàn)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(chǎn)生這種現(xiàn)象的原因:一是較陡段泥沙顆粒通過(guò)兩側(cè)山體崩塌滑坡側(cè)向補(bǔ)給,床面大尺寸漂石與周?chē)妮^細(xì)顆粒會(huì)逐漸形成相對(duì)穩(wěn)定且水流阻力大的自鎖結(jié)構(gòu),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(dǎo)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(xiàn)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(jìn)一步影響相關(guān)流域地貌的演化,如增加河流襲奪的機(jī)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(xué)水力學(xué)與山區(qū)河流開(kāi)發(fā)保護(hù)國(guó)家重點(diǎn)實(shí)驗(yàn)室水利水電學(xué)院;
【基金】：國(guó)家自然科學(xué)基金資助項(xiàng)目(51509172;51539007;51609160) 國(guó)家重點(diǎn)研發(fā)計(jì)劃資助項(xiàng)目(2016YFC0402302) 國(guó)家“十二五”科技計(jì)劃資助項(xiàng)目(2012BAB05B02) 四川大學(xué)青年啟動(dòng)基金資助項(xiàng)目(2015SCU11046)
【分類(lèi)號(hào)】：TV143
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本文編號(hào)：1661658