Abstract: Cementation plays an important role in the stress-strain and strength behavior of cemented sand. The calcium oxide cemented sand samples prepares artificially in twice mixing water method. In order to speed up the carbonation reaction, samples are then placed in a humid room filled full of dry ice. Until samples curing are finished, consolidated drained triaxial tests and CaCO3 quantitative chemical tests are conducted on artificially cemented sand which have different cement ratios. The influence of cement ratio on the physico-mechanical characteristics of cemented sand is analyzed. Defined the product of CaCO3 content and Ca(OH)2 content as the chemical index to estimate the degree of cementation, an modification is given on Mohor-Coulomb strength theory using the chemical index . The test results show that twice mixing water method can effectively control the initial moisture content of artificially cemented sand; the formation of carbonate cements have a great influence on physico-mechanical properties of artificially cemented sand. At different confining pressures, samples show stress softening. With the increasing of cement ratio, stress softening are enhanced, cohesion and increment of frictional angle increase. Cemented sand has property of pressure sensitivity. Confining pressure and cement ratio can effectively control dilatancy. With the increasing of , cohesion and increment of frictional angle increase. The quantitative relations of cohesion, increment of frictional angle vs. are obtained. Combined with the test results, the relationship of shear strength parameter and is established to modify Mohr-Coulomb strength theory. This modified model can reflect the influence of carbonate cements on strength of cemented sand.

Key words: cemented sand, shear strength, chemical index, Mohr-Coulomb strength theory