Characterization and stabilization of disposal sediment from Sengguruh Reservoir: physical and mechanical properties approach

Sengguruh Reservoir, located in Malang Regency, has experienced severe sedimentation since its operation began in 1988, resulting in a significant reduction in its storage capacity. The dredged sediment placed in the spoilbank has the potential as a construction material; however, its physical, mechanical, and geotechnical stability characteristics must be evaluated first. This study aims to assess changes in the properties of disposal sediments before and after stabilization with 10% and 15% lime additives using a quantitative, laboratory-based approach. The types of samples tested were natural soil, natural soil stabilized with 10% lime, and natural soil stabilized with 15% lime. The tests included parameters of specific gravity, grain distribution, atterberg limits, soil classification, standard proctor, and direct shear. The results showed that adding lime to natural soil decreased the plasticity index and increased the specific gravity. The sample with 10% lime addition achieved the highest cohesion value of 22.022 kPa, along with an internal friction angle of 36.40°. Based on the combination of physical and mechanical properties, a mixture of natural soil and 10% lime was selected as the optimum material for slope stability analysis. Slope stability modelling showed a factor of safety of 1.569 at an embankment height of 7 m, which meets the stability criteria and maximum storage capacity. These results confirm the potential use of stabilized disposal sediments, particularly with 10% lime addition, as a sustainable alternative to embankment construction materials.