Study On Characteristics And Scour Depth In Middle And Lower Reaches Of Liaohe River

Long-distance pipe laying is bound to intersect with rivers,and usually in the form of typical crossing.Pipeline crossing the river is inextricably linked with the evolution of the riverbed where it passes through.The variation range of riverbed scour directly affect the laying and safety of crossing pipelines.Analyzing the regularity of river bed scouring and judging the natural scour depth,which is the key point to rationally determine the cross buried depth and the main basis of pipeline crossing.Due to the fact that the pipeline is buried in our country belongs to an emerging industry,the current research on the depth prediction of pipe-crossingng pipeline is not yet ripe,in order to avoid the flood damage of the river pipeline,it is necessary to further explore the problem.In this paper,taking the Liaohe River as an example,I have selected river bed section data,hydrological data,and sediment data in 1985-2013 years of 7 hydrologic stations in the middle and lower reaches of Liaohe River,including Fudedian,Tongjiangkou,Tieling,Mahushan,Ping'anpu,Liaozhong,and Liu jianfang.Based on statistical analysis as the main method,the characteristics of water and sediment in the main stream of the Liaohe River were analyzed.Based on the comparison and analysis,the paper compares and analyses the size of dominant flow,bankfull flow and effective flow in the Liaohe main stream section.With the method of stepwise regression analysis,using DPS data processing software to select the Water shape index which has obvious influence on the natural scour depth,the optimal regression equation of natural scour depth is established,which can provide reference for the buried depth design of pipeline crossing engineering in Liaohe River basin.The main conclusions are as follows:(1)The distribution of sediment in the middle and lower reaches of Liaohe River is more concentrated than the runoff,and the distribution of runoff and sediment is more homogeneous during the year;Basic synchronization of interannual variation of water and sediment in the middle and lower reaches of Liaohe River.(2)In Liaohe River,the ratio drop is less than 0.3 and the winding degree is more than 1.5,it belongs to the high winding rivers with slow slope.Before 2007,the suspended particle gradation showed a decreasing trend,the median particle size from 0.0334 mm to 0.0256mm;the trend is increasing after 2007 years,the median grain size from 0.0215 mm to 0.0367 mm.(3)The improved method solves the problem that the dominant flow can not be calculated because of the lack of the surface slope data,and it is proved that the method is feasible to calculate the dominant flow.(4)By comparing the dominant flow,bankfull flow and effective flow,it is shown that the flow capacity of the main channel in the last 30 years is greater than the capacity of flow to shape the riverbed and the ability of long-distance sediment transport.(5)After stepwise regression analysis,the optimal regression equation of scour depth wasestablished by selecting the factors with significant influence on scour depth,the fitting degree was good,and the linear regression relationship was statistically significant.