Mechanical Properties Of Saturated Sand Reinforced By Randomly Distributed Fibers

The structure of natural sand is loose,with the characteristics of easy erosion,easy erosion and easy liquefaction.It causes various engineering geological problems due to its instability.Sand structures are affected by earthquakes or man-made dynamic loads,which can cause a drop in bearing capacity,causing some embedded structures to float,ground settlement,embankment settlement,and lateral displacement of slopes and retaining walls.Therefore,most natural sands need to be strengthened to meet engineering requirements.sand reinforcement has always been an important subject in the field of engineering geological research.At present,the main research trends of sand reinforcement mainly focus on the use of geosynthetics or randomly distributed fibers to strengthen loose sand to improve shear strength and unconfined compressive strength and stiffness,or use different additives and cement lime Mix to improve the bearing capacity and stiffness of sand.However,there are few studies on medium-density sand after compaction of embankments and retaining walls,and more on the static characteristics of reinforced sand,and the dynamic characteristics(such as: residual deformation,dynamic Young's modulus))And other studies,especially the impact of cyclic stress amplitude on the dynamic properties of sand is relatively few.In view of the above phenomena,and taking the above problems as a source of innovation,this paper proposes to use sisal fiber to strengthen the dense marine sand and study its static and dynamic properties.This paper mainly uses saturated triaxial test equipment and GDS dynamic triaxial test system to test saturated marine sand reinforced with sisal fiber(hereinafter referred to as fiber reinforced sand),and the various mechanical indicators of fiber reinforced sand The main contents of the research are as follows: First,through the static triaxial compression test on sisal fiber reinforced sand,the quantitative analysis of the fiber content,fiber length,relative density,and confining pressure on the mechanical properties of fiber reinforced sand The influence of these variables on the stress-strain curve,elastic modulus and secant modulus of fiber-reinforced sand is mainly analyzed,and the mechanical mechanism and principle of action are analyzed.At the same time,the variation of the principal stress envelope under different confining pressures is also studied;second,the dynamic characteristics of the fiber-reinforced sand are studied based on the GDS dynamic triaxial test system,mainly the residual deformation of the fiber-reinforced sand And dynamic Young's modulus Ed is studied.Residual strain and dynamic elastic modulus Ed are two important attributes that define the dynamic properties of sand.The dynamic Young's modulus Ed of soil is an important parameter that reflects the dynamic characteristics of soil.An important indicator for evaluating the stiffness of sand.The residual deformation characteristics are analyzed by defining the residual axial permanent strain accumulation rate and the residual volume strain accumulation rate,and an attempt is made to determine the deformation mechanism of the residual strain under the two mechanisms of "plastic creep" and "plastic collapse".By studying the variation of specimen stiffness with the number of cyclic load cycles,the changes of stiffness under low-level cyclic stress amplitude and high-level cyclic stress amplitude are compared.This paper also deduces the empirical formula of residual axial strain and analyzes its influencing factors.This research on the mechanical properties and mechanical parameters of fiber-reinforced sand can provide theoretical basis for the design and construction of reinforced sand for high-speed embankments,dams,retaining walls,etc.Mechanical parameters such as the Modulus of Modulus can provide basic basis for the design and calculation of geotechnical buildings under dynamic loads such as traffic loads and earthquakes.The reasonable selection of parameters will directly affect the safety and economy of the building structure.