Dynamic Triaxial Experiment And Theoretical Model Of Cement Stabilized Coastal Aeolian Sand

Coastal Aeolian Sand is difficult to be in compaction due to poor grading. It isalways in the saturated or half saturated condition, which makes it be liquefied easily.Hence the sand consolidation problems become one of the important researchtopicsof the society of engineering and academia, especially in the field of highwayengineering. This paper first analyzed the physical and mechanical properties ofCoastal Aeolian Sand; Secondly, using GDS dynamic and static triaxial test system,made research on the solidification function of cement to Coastal Aeolian Sand, andanalyzed the influence of effective confining pressure, cement dosage, curing age tothe law of development of sand stress-strain curve and pore pressure curve in thecondition of high water content; Thirdly, adopted the strain loading of differentamplitude of constant amplitude cyclic to Coastal Aeolian Sand and cement solidifiedsand under the different datum strain, analyzedthe development regularity of porewater pressure of the sample; lastly, through a microscope to observe the microscopicstructure of the cement solidified sand, revealed the action mechanism of cementreinforcing theCoastal Aeolian Sand.The results show that the peak deviatoric stress of the sand sample increased nearlylinearly with the increase of confining pressure. In the drained tests, the peakdeviatoric stress of cement sample obviously increased with the increase of cementdosage, but the peak under low cement dosage (2%) was lower than that of the sandsample; In undrained tests, the strength of the cement sample was slightly lower thanthat of the sand sample, because that the cement hindered the dissipation of porepressure.Compared with7days, the curing ageof28days did little contribution to thestrength. The axial strain of the sample happened, and then the development rule ofpore pressure can be used "S" type curve descriptionsubjected to constant amplitudecyclic strain.The liquefaction resistance of close-grainedsand increases with thegrowing of the datum strain and the decrease of the amplitude of thecyclic strain; theliquefaction resistance of mediate-dense sandaffected by datum strain was small. With the decreasing of cyclic strain amplitude and the increasing of the datum strainand the cement dosage, the stronger the liquefaction resistance of the cement samplebecame.Compared with7days, the curing age of28days contributed little to theliquefaction strength of the sample.Based on test data, the test logarithm model ofdynamic pore pressure and the logarithm model of dynamic shear modulus were setup. The parameter ψof the sand sample pore pressure model increased along with thegrowing of datumstrain and relative density; the model parameters ψ of the cementsample pore pressure was generally smaller than that of the sand sample,andincreased along with the increasing of datum strain and cement dosage, which wasaffected little by the age. The model parameters、 of the dynamic shearmodulus increased with the increase of cyclic strain amplitude, and decreased alongwith the increasing of the datum strain, relative density, cement dosage and theage.After mixed with cement, the hydration products transformed from fibrous to gridwith the increase of the dosage of cement, and changed the pore structure of the sandsample, and also reduced the porosity, in which the grid skeleton connected the sandparticles into an organic wholeenhancing the connection strength and structurestrength. With compressing sample to datum strain, the shear failure was postponedwith the cementation strength enhancement, the decreasing of confining pressure andporosity. When the cement dosage increased, the sample damage developed relativelyslower, the porosity became relatedly lower, and the pore pressure was not easy todissipate but rapidly rose under the effect of the dynamic load. However, the cementenhancedthe connection strength of the sample, making the pore pressure grew slowlyin the late period; When the datum strain grew, the greater the sample damage was,and the porosityincreased, and the pore pressure was easy to dissipate and with slowgrowthunder the effect of the dynamic load.