| As one of the most common geological disasters of Loess Plateau,loess landslides bring huge threaten to the safety of life and property of local people due to its destructiveness,suddenness and wide influencing area.In addition,research on the prediction methods of loess landslides is a hot and difficult topic in the research of loess landslides because of large distribution area of loess,immature prediction methods,the difficulty of monitoring systems in wide application and high cost of landslide treatment.In fact,most of loess landslides are triggered by water,and the essence of the occurrence of landslide is the process from strength reduction and deformation to failure of slip zone soils due to water infiltration.Therefore,Zhengcheng landslide is taken as the research subject,a series of CU experiments were conducted on remolded slip zone soils samples under different water contents and the data results were processed and analyzed in order to further study prediction methods of loess landslides and provide a basis on the occurrence of landslides,the conclusions are as follows:(1)According to the field investigation,Zhengcheng landslide is caused by shear strength reduction and deformation failure of slip zone soils due to water infiltration from snow melting along cracks of slope into potential slip surface.CU experiments were conducted on remolded slip zone soils samples under the different water contents of 15.28%、17.95%、20.25%、22.56%、25.32%、27.55% and 30.24% to study the effect of water on slip zone soils based on analyzing development process and formation mechanism of landslides,and deviatoric stress-strain curves of different water contents can be obtained.It is concluded that deviatoric stress when the slip zone soils samples failed decrease with the increase of water content,and deviatoric stress will increase with the increase of confining pressure under the same water content.Furthermore,the relationship between shear strength parameters and water content are obtained,and c and φ will decrease when water content increase,and c reduce more rapidly due to its sensitive to water.Besides that,there is a obvious decrease of cohesion around the plastic limit.(2)Critical state lines of slip zone soils under different water contents are obtained by CU tests data and results.It is obvious that critical state line of sample with higher water content is above the lower water content compared with critical state lines of samples with the water content of 20.25% and 30.24%,which can demonstrate slip zone soils will easier to reach critical state with high water contents.The quantitative relationship between critical state line and water content can be established combined the relation between destruction stress(q)and effective mean normal stress(p’)and shear strength parameters based on Mohr-Coulomb strength criterion and the relationship between water contents and shear strength parameters.And it can be confirmed that it can provide guidance for the failure determination of slip zone soils and prediction of landslides through the comparison of critical state line under a water content and actual stress state by the example of landslide of Bei-Hei Freeway expansion engineering K177+500 section road area.(3)It is generally accepted that plastic limit is the “starting water content” of loess landslides,and it is necessary to determine critical proportion of points of slip surface more than plastic limit to predict the occurrence of loess landslides.So,infiltration process of simplified Zhengcheng landslide was firstly conducted by MIDAS software,and then starting shear strength parameters were obtained through back-calculation method,and it is concluded that 62.5% of points on the slip surface over plastic limit when the loess landslides occurred through MATLAB calculation procedure,so it can provide guidance for the prediction methods through combining the water content of points of slip surface through monitoring system with calculation results. |
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