Experimental Study On Mechanical And Engineering Properties Of Polypropylene Fibers For Improving Aeolian Sand

There exist abundant aeolian sand resources distributed in desert areas,however,the poor engineering characteristics of the sand make it impossible to be used reasonably,which results in waste of resources.Based on this,a series of researches on improving aeolian sand have been carried out at home and abroad,most of which adopt geogrid reinforcement and chemical curing agent.Although these measures can improve the mechanical properties of aeolian sand,their operation is complicated and it is easy to make the aeolian sand anisotropy.In order to solve the above problems,based on the actual engineering requirements,this paper adopts the method of blending polypropylene fiber into aeolian sand,so as to study the effect of fiber on the mechanical properties of aeolian sand.The main research contents are as follows:(1)The compaction characteristics of fiber-modified aeolian sand were studied through compaction tests.The test results were compared with plain aeolian sand,indicating that the addition of fiber do not change the original compaction law of aeolian sand,but can increase the maximum dry density by up to 0.106g/cm~3and reduce the optimal water content.The compaction mechanism of fiber-modified aeolian sand is described,and the mechanism of fiber's action in the compaction test is analyzed based on the assumed compaction conceptual model.(2)The unconsolidated undrained test was performed to study the shear strength mechanical properties of aeolian sand.The test results show that compared with aeolian sand without fiber,the cohesion of fiber-modified aeolian sand is significantly increased,with an increase of 65.8%?440%,while the increase in internal friction angle is smaller,indicating that the increase of shear strength mainly comes from the contribution of cohesion.The stress-strain relationship of aeolian sand was analyzed,and it was found that fiber can increase the failure strength and toughness of aeolian sand.The strain-softening model and hyperbolic function model were used to describe the stress-strain relationship reasonably.The strengthening mechanism of fiber on the shear strength of aeolian sand is described in terms of friction reinforcement,equivalent confining pressure,bending restraint and three-dimensional stress net formed by fiber interlace connection.Additionally,through the assumed single fiber action model,the shear strength increase formula due to fiber reinforcement is derived.(3)The water migration test was carried out to study water content distribution of aeolian sand columns under different fiber contents and vertically placing time.The results show that fiber can improve the water retention capacity of aeolian sand,the improvement effect is affected by fiber content and vertically placing time.Based on the experimental results,the action mechanism of the fiber is explained from the changes of the fiber to the matrix potential and the distribution of the fiber in the sand.