Shear strength of repacked remoulded samples of a calcareous soil as affected by long-term incorporation of three organic manures in central Iran

摘要: Improvement of soil organic matter content and its effect on mechanical properties is a key goal for sustainable agriculture. This study examines the effects seven-year incorporation manures (municipal solid waste compost; air-dry sewage sludge; cattle farmyard manure) shear strength parameters (cohesion, c; internal friction angle, φ ) silty clay loam soil. Disturbed samples collected from topsoil experimental plots to which had been added at three rates (25, 50 100 t ha −1 were remoulded two gravimetric water contents (WC) 17.1 20.9%. Three intact removed large specimen tests conducted using direct box. To WC soils with different bulk densities (BD) arising manure management, an index consistency (IC) was introduced, defined as ratio plastic limit (PL). By increasing 20.9%, c almost doubled, whereas significantly decreased, but only by 13%. The changes in due explainable effective stress theory. relationships IC linearly decreasing below limit, respectively, some evidence plateau or non-linearity above this level. results showed that having (or BD), change could be unified explained concept.