| The Shuanglan crude oil&product oil pipeline is one of the important projects in western China and has a very important economic strategic position.Due to the large regions of pipeline crossing,various geological disasters occur frequently,especially during the annual summer flood season,the pipeline has been destroyed by natural disasters,which put a serious threat to the safely operation of pipelines.Therefore,it is necessary to analyze the causes of waterlogging and do the optimize design and suitability analysis for the pipeline hydraulic protection structure.In order to achieve this goal,the following work is mainly done:(1)Taking a field investigation on the shuanglan pipeline waterlogging situation in 2016,the results showed that 11 points of 15 waterlogging belong to county road waterlogging,whilel belongs to slope waterlogging and 3 belongs fields waterlogging.Make the river channel waterlogging,which accounts for the most of the waterlogging,be the main object of exploration,and select one of the representative big cross section,Dashahe river,as a key exploration.Through the exploration,the information about the design parameters of submerged wall-which is the hydraulic protection structure in local pipe section,can be got.And as the same time,the basin hydrological data Dashahe river are also be collected.Calculate the cross section of flood peak discharge and water level through the hydrological data,and according to the damage of hydraulic structure protection,the preliminary analysis of the reasons are made.(2)Build the model of straight top submerged wall under the condition when waterlogging occurs,and using the VOF model in Fluent to calculate the flow field around the submerged wall.The results show that due to the shape of wall is not match well with the water flow structure,there are some situations that streamline separation happen on the three surface of wall,and this is the main cause of local scour.(3)Aiming at the cause of waterlogging,the design of curve top submerged wall be put.It has the characteristics of normal distribution curve.Through Matlab and solidworks,two kinds of different thickness of straight top wall and curve top wall geometry models are established.By using the method of numerical simulation,analysis the the four walls' velocity field,pressure field and turbulent kinetic energy and the bed surface shear force.The curve top wall,because of its unique streamline design,can improve the flow structure well.And the study found when the straight top wall get thicker,the latitude of the main flow will be increase,which causes the bed surface velocity and shear force to rise by the gravity,and thus the bed surface was more easily eroded.However,the thickened curved top wall's perform is much more different.Owing to the curve design,the wal can be more suitable for the natural flow pattern,which almost eliminates the lifting effect of the turning point on the water flow,and the maximum return speed of the bed surface is only 68%of the original design.The maximum shear force is decreased by 33%,and the area of the larger shear force is decreased by 77.5%,which proves that the curve design can effectively reduce the local scour and prolong the service life of the submerged wall.(4)Design the shape of stone cage,which is another hydrotechnological protection structure used in Shuanglan pipeline.Analyze the ati-scour performance of square,triangle and semicircle shape stone cage submerged in the flow field.Through the analysis about velocity,pressure,turbulence kinetic energy,bed surface shear force and the resistance force calculation,A discovery is found that semicircle design stone cage can effectively reduce the flow drag force,and prevent itself overturn or break under the impact of the water.And at the same time,semicircle design also has good performance at the role of protection bed surface from scouring by water.(5)Summarize the main reasons of the shuanglan pipeline hydraulic protection structure destruction are natural factors and human factors.Combined with the simulation results and analyzed of the previous chapters and waterlogging reason,the optimization suggestions about the submerged wall are put forward,main about steel wire gabion wall and slope(bank)protection and draw the design drawings.At the same time,the application conditions of the above optimized content and other commonly used hydraulic protection structures are summarized. |
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