Experimental Study On Sand Soil Reinforcement By Carbon Nanotubes Reinforced Nano-silica Sol Infiltration

Sand liquefaction has always been one of the hot topics in the field of soil dynamics and geotechnical seismic engineering.It is easy to cause engineering disasters related to sand liquefaction,such as land subsidence,building subsidence and inclination,landslide,underground pipeline and tunnel floating.In view of the large number of micro cracks in silica gel,which leads to the decrease of strength of solidified sand,nano silica sol doped with carbon nanotubes is infiltrated into sand,and then the solidified silica gel sand complex is formed..In this paper,through static triaxial test,cyclic dynamic triaxial test,triaxial damage test and scanning electron microscopy,the macro and micro mechanism of liquefiable sand reinforced by nano-silica sol system doped with carbon nanotubes is explored.(1)Consolidated undrained shear triaxial tests were carried out on liquefiable sand reinforced by carbon nanotubes with 10%,20%,30% and40% silica sol doped 0,0.01%,0.02%,0.03%,0.04% and 0.05%respectively.The failure stress of solidified sand increases with the increase of silica sol concentration,and the failure strain decreases with the increase of silica sol concentration.At the same silica sol concentration,the peak deviational stress first increases and then decreases with the increase of carbon nanotube concentration,and reaches the maximum at 0.02% and0.03%.(2)The liquefiable sand was strengthened with 20% silica sol doped with 0,0.01% and 0.05% carbon nanotubes,curing for 3,7,28 and 56 days.The peak deviational stress of pure silica sol strengthened specimens tends to decrease with the increase of time,while the peak deviational stress of carbon nanotubes strengthened specimens tends to increase with the increase of time.(3)Carbon nanotubes were doped with 5%,10%,20%,30% and 40%silica sol respectively.After 3 days of curing,cyclic dynamic triaxial tests were carried out under different dynamic stress ratios and effective confining pressures.With the increase of the concentration of silica sol,the liquefaction resistance of the specimens increases;when the concentration of silica sol is 5%,the liquefaction of the two specimens occurs;when the concentration of silica sol is 10%,the pore water pressure of the specimens rises but does not meet the liquefaction standard;and there is no significant difference between the reinforcement effect of 20%,30% and 40%.(4)0.02% carbon nanotubes were doped with 10%,20%,30% and40% silica sol respectively.Consolidated undrained triaxial tests were conducted on liquefiable sand after 200 cycles of cyclic vibration.When the concentration of silica sol is 10%,the strength of the sample decreases,but when the concentration of silica sol is higher,the strength of the sample does not decrease significantly.With the increase of the concentration of silica sol,the attenuation degree of strength decreases.(5)By scanning the specimen and the internal structure of the gel,the cracks in the gel decreased obviously after the carbon nanotubes were doped.The microscopic mechanism of carbon nanotube reinforced silica gel sand composite strength is that the carbon nanotubes are intertwined into a rope and interspersed between the silicon gel cracks,thus inhibiting the crack propagation and increasing the strength of the sample.