碱渣回填地下废弃盐腔室内一维沉降试验研究

盐矿水溶开采产出卤水的同时会在地下形成大量的废弃溶腔,而盐化工企业利用采出的卤水制碱时会产生大量的固体废渣（即碱渣）,将碱渣与饱和卤水混合制成浆体注填到废弃盐腔的过程称为碱渣回填废弃盐腔。碱渣在充满卤水的溶腔内的沉降特性对回填效果会产生重要影响,作为初步研究,对两种不同类型碱渣与饱和卤水混合而成的碱渣浆进行了室内一维沉降试验研究。试验发现：黏粒含量少的碱渣浆絮团发育程度低,絮团小而相互独立,沉降类型为絮凝均匀沉降,黏粒含量多的碱渣浆絮团发育程度高,絮团大而联结成网,发生絮网沉降；碱渣浆沉降过程可以分为4个阶段：絮凝阶段、沉降阶段、主固结阶段和次固结阶段；对比两种碱渣的沉降过程发现,发生絮网沉降的碱渣浆在前3个阶段用时均较长；沉降基本结束后,形成的沉积体孔隙比较大,沉积体内仍含有大量的自由水。本研究揭示了两种不同类型碱渣的一维沉降规律,为进一步探索碱渣沉降固结机理及现场碱渣回填废弃盐腔工程提供一定参考。

Experimental study on one-dimensional settlement of alkali wastes backfilled to abandoned salt caverns

The method of solution mining to explore halite will generate large quantities of abandoned caverns, while soda ash production whose raw materials are the brine produced by solution mining will generate abundant alkali wastes. The process that alkali wastes are mixed with the brines into slurry and pumped back into the abandoned caverns is defined as in-situ backfill. The settling behavior of the slurry is very important to the backfill effect. As a preliminary study to investigate the behavior of waste particles in brine-filled caverns, laboratory one-dimensional settlement experiments on two types of alkali wastes collected from different soda ash production techniques are conducted. The main results are: (1) the settlement of alkali wastes with a small amount of clay particles, whose flocs are small and independent, can be classified as uniform settling of flocculation, and that with a large amount of clay particles, whose flocs are large and connected, is net settling of flocculation; (2) the settling process of waste particles can be divided into four phases: flocculation phase, settling phase, primary consolidation phase and secondary consolidation phase; (3) by comparing the settling processes, durations of the first three phases are longer for the slurry with net settling of flocculation; (4) the void ratios of the two sediments are both very large when the primary consolidation is completed, indicating that there is a large amount of free water in the sediments. The settling behavior of the two types of alkali wastes is revealed, and the relevant factors are analyzed. This research may provide certain reference value for the study of the settling mechanism and site backfill.