Experimental Study On Deformation And Strength Of Cemented Soil Under Cyclic Shear Loading

Soft foundation with the characteristics of low strength,strong compressibility,high water content and poor engineering properties,which are prone to large deformation or even damage under cyclic loading such as earthquakes.Cement-reinforced soft foundation can significantly improve the poor dynamic characteristics of soft soil and reduce the uneven settlement of foundation.In recent years,it has been widely used in the construction of major infrastructure such as roads,railways and airports.According to the characteristics of seismic loading,a series of tests were carried out on cement soil by cyclic simple shear apparatus.The main contents and conclusions are as follows:(1)The effect of the age,consolidation stress and cement content on shear strength,cohesive strength and internal friction angle were studied by static test.It is indicated that the development of stress-strain curve of cement soil is greatly affected by cement incorporation ratio and age,and is less affected by consolidation stress.The cement incorporation ratio determines the development mode of the stress-strain curve of the cement soil.The shear strength,cohesion and internal friction angle of cemented soil increase with the increase of cement mixing ratio and age.(2)The effect of cyclic stress ratio on dynamic strain,dynamic strength and softening index of cemented soil were studied under unidirectional cyclic loading.It was shown that the critical cyclic stress ratios were 0.302 0.365 and 0.405 for the cement-soil with cement ratio of 4%,8% and 12%,respectively.Using the failure criteria of turning strain,the cyclic stress ratio of the cement soil and the failure number are in a linear relationship.2% single-strain standard and transition strain standard have less influence on dynamic strength.Through the regression analysis of the test data,the relationship between softening index and cycle number and cyclic stress ratio is established.(3)The effect of phase difference on dynamic strain,dynamic strength and softening index of cemented soil were researched under bidirectional cyclic loading.The test results show that the phase difference determines the coupling mode of bidirectional shear stress.When turning strain is used as failure criterion of cement-soil,with the increase of phase difference,the turning strain of cement-soil decreases gradually and the softening rate accelerates.