Research On The Characteristic Of Flow Field Around Straw Sand Barrier And Surface Processes

Equipment sand fixation become the main trend of sand control in the future.Straw matting is a kind of sand straw material used in mechanized operation.The structure form of straw matting is different from that of traditional straw barrier.In order to improve the sand fixing ability of straw sand barrier,in this paper,the mechanical stability of sand barrier,protection effect of sand barrier with different shape of grid,sediment accumulation characteristics of sand barrier and its surface process are studied.The results can provide theoretical support for equipment sand fixing.The research was supported by the " project of national science and technology supporting plan(2015BAD07B02)".The main reaserch work and conclusions are listed as the following.1.The change of force at embedded of sand fence with pore distribution and porosity were studied using numerical method,then the applicability of calculation method of wind pressure in building structure is studied which is calculated the wind pressure on sand fence.Results show that the force at embedded of sand fence with no pore is higher than that of pore fence.The maximum bending moment and shear force of the embedded end of sand fence decrease with the increase of porosity.The calculation method of wind pressure which used in building structure can be used to calculate the pressure on sand fence.The shape coefficient has a obvious influence on the calculation results,the coefficient of sand barrier with medium porosity should be higher.2.The protection effect of triangular grid,square grid and hexagon grid sand barrier are investigated base on field study.Results show that wind speed efficiency could be reduced by triangular sand barrier and hexagonal sand barrier significantly than square sand barrier.The reason is that the flow field structure of the triangular mesh and hexagonal grid sand barrier is more random,and the flow structure of the square grid sand barrier is relatively obvious.3.Sediment accumulation characteristics of sand barriers at different slope positions is studied by measuring sand surface in sand barrier.Results show that the sand barrier at the toe of windward slop has the most sediment accumulation.The concave surface of sand barrier at the middle of slope is smooth,and the sand grains are dominated by accumulation,without wind erosion.The sand barrier at first few rows deposited the most of sand grains.The sand collection quantity decrease exponentially along the direction of toe to top of windward slope.Sand accumulation is obvious on the top of slope,it deposit mostly at the side of upwind in straw checkerboard,and sand erosion and deposition coexist.4.A numerical model is proposed to calculate the sand surface process.The numerical results is verified by compared to experimental results.Then the sand surface process of sand barrier is analyzed,and the sediment transportrate,friction velocity and other physical variables are studied.