The Study On The Experiment Of The Scoured Pits Of The Dam Buttress And The Runoff Of Root Rocks Of The Ningxia River Section Of The Yellow River

The Ningxia river section of the Yellow River, which is 379Km long, belongs to the upper section of lower reaches of the Yellow River. The plain watercourse to be harnessed emphatically, which is 266.7Km long, is divided into three sections. The river section from Xiaheyan to Rencundu is unstable and divergent, and the one from Rencundu to Toudaodun is cooked, and the one from Toudaodun to Shizhui Mountain is wandering. The quality of the riverbed in the upward Rencundu, which is made up of scree, is different from the one in the downward Rencundu, which is made up of sand. In order to explore harness scheme, layout, measurements and parameters concerned of the project, which are appropriate for the characteristic and the evolvement law of the watercourse of Ningxia section of the Yellow River, the study on the experiment of the scoured pit of the dam buttress and runoff of the root rock of Ningxia section of the Yellow River is of important theoretical meaning and practicable value.The cause of the formation of the scoured pits and the runoff of the root rocks are studied through the experiment of the scoured pits which are along the river section from Xiyaozipai in Qingtong city to Xiabaqing in Taole town. The formation of the scoured pits is related with such factors as the unstable flow velocity and the unstable flow state caused by the circumfluence in the cross direction, the upstream circumfluence and thecircle flow around the embankment. The runoff of the root rocks is connected with the stability of the rocks when they are submerged in water, the quality of the riverbed and the pit nearby the dam toe. In addition, the contrast analysis and calculation of the computational formulas commonly used in the scoured pit designs are conducted. It concludes that Makeweiyefu formula and Boerdakefu formula can be chosen for use besides Jianghuanzhang formula.Through theoretical computation and experimental observation, it is put forward that the maximal depth of the scoured pits of the embankment is from ten to thirteen meters, and for several pits whose top are rinsed by main flow continuously, their scoured depth have reached twenty meters. According to renovation scheme and connecting with practical river harness situation, netlike cover protection and quadruped concrete hose measurements, which are comparatively effective, are commended. The results will provide important reference value for the design and construction of the watercourse harness of the Ningxia river section of the Yellow River.