Numerical investigation of the tensile strength of loess using discrete element method

The tensile strength of loess is important for the tension-related crack and failure in the Loess regions. While the previous work on the tensile strength of loess mainly focuses on the test method and its variation with different internal and external factors, the micro-mechanical characteristics of the tensile experiments are seldom studied. Taking the unconfined penetrated test (UP test) as example, the tensile strengths and internal stress distributions of undisturbed loess samples under the loading plate-sample ratios (d/D) ranging from 0.05 to 0.95 are numerically investigated using discrete element method. The internal stress distribution, failure pattern of sample and variation of internal crack are clearly reflected by the discrete element modelling. The DEM simulation results also show that: 1) the d/D in the range of 0.15 to 0.35 is recommended for measuring the tensile strength of undisturbed loess; 2) the tensile strength of undisturbed loess increases with d/D recommended above ;3) the failure of sample is mainly controlled by the tensile stress when the d/D is equal or lower than a critical d/D 0.50, while that is mainly controlled by the compressive stress when the d/D is larger than a critical d/D 0.50. This study shows the capability of discrete element method to simulate the UP test, thereby providing us a relatively reliable way to investigate the tensile strength of loess numerically and to explore the internal stress and crack distribution of soil sample.