IMPROVING THE DYNAMIC PERFORMANCE OF PRELOADED AND PRESTRESSED MECHANICALLY REINFORCED BACKFILL BY USING A RATCHET CONNECTION

Based on a series of cyclic cavity expansion tests carried out on a thick hollow cylinder apparatus (HCC) and on minipressuremeter tests performed in a calibration chamber, a method is proposed to establish a reliable correlation between the result of a "reference" cyclic expansion test carried out in a sand, in terms of cavity volume accumulation after a certain number of cycles, and the elementary behaviour of the same sand as observed upon undrained cyclic triaxial tests, in terms of number of cycles necessary to reach cyclic mobility or true liquefaction. The strong similarities observed between drained cyclic expansion test (non homogeneous test) and undrained triaxial test (homogeneous test) allow valuable correlations to be obtained between the results of both types of tests. A first validation of the method proposed is performed by comparing the liquefaction properties of two different sands with same initial conditions, and shows a good discriminating power of the method. Finally, the necessity of further validation of the method, in particular, a validation based on the performance of real in situ pressuremeter tests on sandy sites is mentioned.