Damage Process Micro-Discrimination And Damage Parameter Determination Of Road Foundation Compacted Soil

The triaxial compression tests and creep tests of subgrade soil samples with different lateral pressures are conducted with a new set of modified triaxial compression apparatus which made the soil samples can be scanned with CT at the same time during compression process. With the test results, the different damage processes of soil samples are described for the first time from both of the CT numbers and CT images. A new method and two quantitative indexes are also presented to analyze the change of soil fabric during the damage process on the basis of CT images and stereological technique. The production mechanisms of micro-crack in the soil samples during the damage process are analyzed and the failure modes are concluded from the point of view of fracture mechanics. With the theory of generalized twin shear stress strength, we also presented the formula of limiting inner pressures for ring with different strength in tension and compression. On the basis of those formulas, a new set of test apparatus is developed and the tension strength as well as fracture toughness of compacted bess is determined. A set of software (FREAME) is developed for the automatic search of the most unstable sliding surface and calculation of the lowest safety index. With this software, a concise graph for the stability of subgrade slope with simplified Bishop's method is obtained by systematic calculation. The samples on stability of subgrade slope are calculated.