Abstract: When backfilled to abandoned salt caverns full of brine, alkali waste particles will settle freely and form a sediment layer at the bottom of salt caverns. This layer may consolidate further under its own weight. In order to understand the sedimentation and consolidation behaviors of alkali waste backfill in salt caverns, settling column tests together with oedometer tests are conducted on alkali waste from Huai'an in Jiangsu province. Test results show that: (1) The settling process of alkali waste in brine can be divided into three stages: flocculation stage, settling stage and consolidation stage. The settling curve and settling rate are significantly affected by the initial concentration. (2) The particle size distributions, density, water content and void ratio of alkali waste all show layered characteristics. The particle size and density increase with depth, the water content and void ratio decrease with depth. (3) The alkali waste has a very high compressibility; and the value of a1-2 is 3.36 MPa-1. The consolidation coefficient of alkali waste decreases significantly with an increase of consolidation pressure in stress range of less than 100 kPa. The test results are important for the study of sedimentation and consolidation behaviors of alkali waste backfill in salt caverns, and they can used to guide the backfill construction technology and reinforcement processing of alkali waste.

Key words: salt cavern, alkali waste backfill, sedimentation, consolidation, settling column test