Abstract：Abstract：Based on the medium-sized triaxial test and the large-scale field direct shear test，the strength properties of coal wastes from Xuzhou in China，are systematically studied. The results show that the strength of coal wastes can be described by Coulomb¢s equation or De Mello equation for shear strength. The parameters for these formula are presented. When the coarse grain(D＞5.0 mm) proportion in samples changes from 30% to 60%，the shear strength is seen with obvious changes differently with the pure coarse or fine samples. The influential factors on the coarse crush are also compared，in which the confining pressure and the coarse grain content are the primary factors. In the end of the paper，it is indicated that the cohesion of coal waste from the field shear test is smaller than that from laboratory test；while the friction angle from the field test is larger than that from the laboratory test. The mechanism for above results is achieved.
