Evaluation of stiffness of crushed rock by a falling weight method

Resilient modulus ( ) Mr is one of the important parameters used in the design and analysis of pavement materials. In general, Mr is usually evaluated by laboratory repeated load triaxial (RLT) test, which is complicated and timeconsumed. To solve these problems, many researches have been studied to find out other methods for determining Mr in a simple manner. In this paper, an application of impact load method by a dynamic hammer (DH) on a crushed rock sample compacted in CBR mould was attempted for evaluating the soil stiffness ( ) k , and a method for analysing constrained modulus ( ) MDH for various stress levels was proposed. Then, the MDH was compared with the constrained modulus 1 ( ) M D for various stress levels obtained performing onedimensional compression test. The material used in this study was a well-graded crushed rock. The followings are found from the results of this study. Firstly, in a series of DH tests with the same falling height, the k value gradually increases with the number of drops ( ) n , approaching a stable value when n approaches infinity. The k value corresponding to n equal to infinity ( ) n k  can be determined by a hyperbolic method. Secondly, the constrained modulus by DH test ( ) MDH can be determined by the true k values determined for different stress levels ( )  depending on different falling heights used in DH test. Lastly, the MDH  relationship agrees with the M1D  relationship, however the former exhibited large data scattering.