Abstract: Laboratory tests are conducted to investigate geotechnical properties of sewage sludge in a sludge reservoir of a landfill, including organic content, water content, limit content, grain-size distribution, permeability coefficient, shear strength and consolidation coefficient. Test results show that the sewage sludge in the reservoir has much higher organic content and water content than the muddy soil. The average value of organic content is 45% and water content is 520%, respectively. As a result of biodegradation with a period of two years, both organic content and water content of the sewage sludge in the sludge reservoir show a decreasing trend with the depth. The sewage sludge had a very high compressibility, and the value of a100-200 is 7 MPa-1. The consolidation of the sewage sludge shows a nonlinear large deformation behavior; and the coefficient of consolidation is of the order 10-5-10-6 cm2/s, showing a significant decreasing trend with an increase of normal stress. The shear strength parameters are low with a cohesion of 0 kPa and an internal friction angle of 14.7°. The high organic content is the essential reason for the high values in water content, plasticity index and compressibility as well as the low values in permeability, consolidation coefficient and shear strength. The experimental results provide necessary parameters for the disposal of sludge reservoir and analysis of stability.

Key words: sewage sludge, sludge reservoir, organic content, water content, consolidation coefficient, shear strength