An analysis of soil composition and mechanical properties of riverbanks in a braided reach of the Lower Yellow River  

作　　者：XlA JunQiang WU BaoSheng WANG YanPing ZHAO ShouGang 

机构地区：[1]State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China [2]Yellow River Institute of Hydraulic Research, YRCC, Zhengzhou 450003, China

出　　处：《Chinese Science Bulletin》2008年第15期2400-2409,共10页

基　　金：the National Natural Science Foundation of China (Grant No. 50409002);the Ministry of Science and Technology of China under the frame of Program Strategic Scientific Alliances between China and the Netherlands (Grant No. 2004CB720402);the National Natural Science Foundation of China for Creative Research Groups (Grant No. 50221903)

摘　　要：The channel adjustment in a braided reach is very prominent in the fluvial processes of the Lower Yel-low River, in which the process of bank erosion plays an important role, especially during the period of clear water scouring. The process of bank erosion is closely related to soil composition and mechani-cal properties of the riverbanks. In this paper, the recent bank erosion process in a braided reach be-tween Huayuankou and Gaocun was firstly investigated after the water impoundment and sediment detention of the Xiaolangdi Reservoir, and then a field observation and indoor soil tests were con-ducted at 10 typical riverbanks in the braided reach. Through analyzing the experimental results, changes of riverbank-soil composition and mechanical properties were found, and the two real reasons causing serious bank erosion in the braided reach were identified. The following conclusions were drawn from this study: (i) the majority of riverbanks are made up of cohesive soil, and can be charac-terized by obvious vertical stratification structures of soil composition; (ii) these riverbanks are very erodible due to the lower clay-content and weak erosion-resistant strength in the bank soil, with its critical shear stress value (0.1―0.3 Pa) being much less than that of the average near-bank flow shear stress (2.0―3.0 Pa), which is one important reason causing serious bank erosion; (iii) frequent occur-rence of bank failure during flood seasons usually results from the fact that the values of shear strength parameters such as the cohesion and internal friction angle decrease with the increase of water content in riverbank soil, and the value of cohesion reduces drastically from 34 to 4 kPa with the increase of water content, which is another important reason causing serious bank erosion in the braided reach.The channel adjustment in a braided reach is very prominent in the fluvial processes of the Lower Yellow Rlver, In whlch the process of bank erosion plays an important role, especially durlng the perlod of clear water scourlng. The process of bank erosion is closely related to soil composition and mechanlcal properties of the riverbanks. In this paper, the recent bank erosion process in a bralded reach between Huayuankou and Gaocun was firstly investigated after the water impoundment and sediment detentlon of the Xlaolangdi Reservoir, and then a field observation and indoor soil testa were conducted at 10 typlcal riverbanks in the braided reach. Through analyzing the experlmental results, changes of t;brtnsml-soo; composition and mechanical properties were found, and the two real reasons causlng serlous bank erosion in the braided reach were identified. The following conclusions were drawn from thls study： （i） the majority of riverbanks are made up of cohesive soil, and can be characterlzed by obvlous vertlcal stratification structures of soil composition; （ii） these riverbanks are very erodlble due to the lower clay-content and weak erosion-resistant strength in the bank soil, wlth its crltlcal shear stress value （0.1-0.3 Pa） being much less than that of the average near-bank flow shear stress （2.0-3.0 Pa）, which is one important reason causing serious bank erosion; （iii） frequent occurrence of bank fallure during flood seasons usually results from the fact that the values of shear strength parameters such as the cohesion and internal friction angle decrease with the increase of water content In riverbank soil, and the value of cohesion reduces drastically from 34 to 4 kPa wlth the Increase of water content, which is another important reason causing serious bank erosion in the bralded reach.

关 键 词：黄海 土壤分析 河堤侵蚀 化学物质 

分 类 号：P942[天文地球—自然地理学]