Abstract: The construction waste generated by underground excavation in coastal cities has the characteristics of high fine content, high water content and looseness. Landfilling is the most common method for disposal of such construction waste. As the waste production exceeds the capacity of disposal, many of the construction waste dumps have the problems of fast filling, lack of drainage facilities, overload of landfill capacity and over height, which are likely to cause safety accidents such as landslide. These irregulated operations reflect the poor understanding of the strength growth law of the high saturation degree waste during rapid landfilling. In this paper, completely decomposed granite (CDG) waste is taken from the site of Shenzhen Hong’ao landslide, and a series of triaxial tests with the drain and exhaust valves closed is performed on the samples with different initial saturations. The experimental results reveal that the undrained shear strength of CDG nonlinearly increases with the increase of confining pressure, and the growth rate is closely related to the initial saturation of the sample. The growth rate of the undrained shear strength significantly decreases as the saturation exceeds 0.7. Inspired by the principle of undrained strength analysis, an estimation method for undrained shear strength is proposed, in which Hilf’s equation and the modified Cam-clay model are employed. The proposed method is verified to be capable for predicting the undrained shear strength for CDG with an initial saturation exceeding 0.6 by comparing the estimation results with the measured values in the triaxial tests. The undrained shear strength cu and normal stress determined by the estimation method can be used in the stability analysis of waste dump with high filling rate.

Key words: construction waste, waste dump, undrained shear strength, pore pressure analysis, estimation method of shear strength