Research On Mechanical Sand Barrier In Highway Sand Protection In Northern Hebei Province

Highway sand disaster has a significant impact on the environment and safety of China and other countries in the world.The invasion of sand damage not only damages the soil,but also spreads rapidly under the action of strong wind,becoming an important source of sand and dust in the windy sand area.When the sand laden airflow is blocked by the subgrade,it will lead to the accumulation of wind sand and cover the highway,which is very easy to cause traffic accidents.Therefore,how to protect the safe operation of the traffic trunk line in sandstorm disaster area has become an urgent problem.The traditional sand fixation technology(mechanical sand fixation,chemical sand fixation and biological sand fixation)has some defects,such as high cost,inconvenient transportation of raw materials,short service life,destruction of ecological landform,low consolidation strength and environmental pollution.Therefore,the effect of single sand fixation method is not ideal.However,the comprehensive sand fixation technology combines the advantages of several traditional sand fixation technologies to improve the sand fixation effect.In this study,the mechanical chemical sand fixation method is adopted.Aiming at the problem that the highway trunk line in northern Hebei is suffering from wind and sand invasion,a new type of open hole sand fixation brick is made by using the local waste salt bearing iron tailings as raw material,cement and fine soil as composite curing agent.Referring to the mechanical sand fixation form,the bricks are laid in grid shape on both sides of the highway to reduce the sand velocity and realize the disaster control by waste.Taking the unconfined compressive strength as the index,the main influencing factors of the strength were analyzed by orthogonal test,and the variation rules of the durability of the cured specimens under the conditions of dry wet cycle,freeze-thaw cycle,wind erosion resistance and ultraviolet erosion were studied emphatically.The sand fixing brick is made with the optimal ratio obtained from orthogonal test,and the design parameters of sand fixing brick are optimized by fluent finite element software.The conclusions are as follows:(1)The results of orthogonal test show that the order of factors affecting the strength of solidified specimens of chloride bearing iron tailings is A(salt content)>B(cement content)> C(fine-grained soil content)> D(water content);after the durability test of single factor(cement content),the unconfined compressive strength and quality of the specimens are lost,and the specimens with 8% cement content undergo nine dry wet cycles and nine freeze-thaw cycles After one month of natural wind erosion,the strength of the sample is far greater than the international requirement of 1MPa,which can fully meet the engineering requirements.(2)The micro internal pore analysis shows that after durability test,the total pore volume increases,the proportion of medium pore volume decreases,and the proportion of large pore increases,but the strength of the sample does not decrease significantly when there are no connected large pores.(3)According to the optimal proportion obtained by orthogonal test,the water content is adjusted on the basis of the second,and the open hole sand fixing brick is made with salt content of 1%,cement content of 11%,fine soil content of 10% and water content of 12%.(4)The simulation results of FLUENT software show that when the design height of sand fixing brick is 40 cm and the laying spacing is 1 m × 1 m,the vortex is fully developed in the sand fixing grid,and the pressure difference generated by the vortex is used to reduce the wind speed,and the engineering effect is remarkable.