The Experimental Study On Dynamic Properties Of Fiber Reinforced Sands

Saturated sand can liquefy during an earthquake.It is usually to carry out reinforcement treatment by means of replacement and dynamic compaction to prevent the liquefaction of the sand foundation.Geotextiles,geogrids,etc.have been widely used in soil reinforcement projects.As a new kind of material,geo-fiber has been used in soil reinforcement projects in recent years.In this paper,a large number of experiments were carried out to focus on the dynamic properties of fiber reinforced sand under cyclic loading.The effects of fiber content,fiber length,cyclic stress ratio and relative density were discussed.Main work as following:?1?Under the condition of D_r=0.5,the influence of various parameters on the liquefaction resistance was studied in detail by varying the test parameters such as fiber content,fiber length and cyclic stress ratio.Through the comprehensive analysis of the test data,relationships between pore pressure ratio r_u and cycle number ratio N/N_L,between r_u and dissipated energy per unit volume ratio W/W_L,between r_u and cyclic stress ratio,between shear modulus ratio G/G₀ and N/N_L and between G/G₀ and W/W_L were given.Test results shown that liquefaction resistance of the sand increases significantly with the addition of a certain amount of fiber,and increases with the increase of fiber content and length.The cumulative pore pressure increases rapidly at first,then slow linearly increases and finally increases rapidly.The pore pressure growth model of fiber sand is significantly different from that of sand.G/G₀ slowly decreases as N/N_L increases.?2?To investigate the influence of relative density,the liquefaction laws of 6mm and12mm fibers at different stress ratios were studied with the sand of D_r=0.3,0.7.The test results shown that the sand of larger relative density has the stronger anti-liquefaction ability under the same condition.?3?Preliminary discussion on the mechanism of anti-liquefaction of fiber sand.It is considered that the additionof fiber lowers the void ratio of the sand sample,leading to a decrease in permeability of the sample and slowing downthe accumulation of pore pressure.At the same time,due to the distribution of fibers in the pores of the sand,the movement of the particles is restrictedduring the vibration process.