Research On Theory And Application Of Alkali Wastes Backfilling That Improved The Stability Of Underground Salt Cavern

In China, more than90%of salt resources are explored with the method of solutionmining, leaving a large number of underground salt caverns. If these salt caverns are notabandoned appropriately, they will induce various geological hazards, mainly large-areasubsidence and pollution of underground water because of brine ooze out. At the sametime, alkali wastes generated from soda ash production are mostly accumulated aboveground, which not only occupy the land, but also deteriorate the surroundingenvironment. However, the project that alkali wastes are backfilled to undergroundcaverns and replace brine, is able to avoid the geological hazards which may be inducedby abandoned salt caverns, and eliminate the pollution by ground accumulation of alkaliwastes. According to the properties of the alkali wastes-brine mixed slurry, systematicsettling and mechanical tests have been conducted for backfilling alkali wastes intounderground salt caverns in Jiangsu. Considering the strength change of alkaliwastes sediments in underground salt caverns, a numerical model has been built basedon the deformation behavior of sediments. The stability of underground salt caverns hasbeen researched by numerical simulation method. The main contents and conclusionsare as follows:1. Considering the temperature and brine in underground salt caverns, settling testsof alkali wastes-brine mixed slurry with different initial concentration were carried outto study the settling and diffusion properties. The settling process and type of alkaliwastes were compared to investigate the influence of initial concentration on the settlingand diffusion properties.2. The sediments of alkali wastes-brine mixtures were investigated andlow-pressure and high-pressure consolidation tests were carried out to study thedeformation behavior of alkali wastes and the consolidation curve ranging from0.1kPato3.2MPa. The physical parameters of backfilled alkali wastes were predicted.3. Fly ash was used as adulterant to treat the alkali wastes sediments. Mineralcomponents, mechanics and microscopic tests were conducted to reveal the mechanicalproperties of compound alkali wastes sediments. The amelioration mechanism wasanalyzed.4. By analysis of the salt caverns volume shrinkage, the mechanism of enhancingthe short-term and long-term stability by alkali wastes backfilling was studied and the main influence factors were presented.5. Considering the volume shrinkage of underground salt caverns, a numericalmodel which represents strength properties of alkali wastes was built based onconsolidation tests. Based on the long-term creep of underground salt caverns, theinfluence of alkali wastes backfilling on the stability of salt caverns was studied.6. On the basis of backfilling alkali wastes into underground salt caverns in Jiangsu,the stability of underground salt cavern and the surface subsidence was predicted bynumerical simulation analysis.