高寒地区尾砂胶结充填体固结特性试验研究

Experimental study on consolidation characteristics of tailings cemented backfill in alpine regions

将充填技术引入高寒地区可有效减少采矿对环境的破坏。针对低温下尾砂胶结充填体力学性能和固结机理研究的不足,开展5℃养护下充填体试块的单轴抗压、XRD分析、热分析和SEM观测试验研究,根据定性和定量分析结果探讨低温下尾砂胶结充填体的强度演化规律与固结机制。结果表明:低温对尾砂胶结充填体早期强度影响较大,其中各主要因素的影响程度由大到小依次为灰砂比、养护龄期、质量浓度;低温下的水泥净浆的AFt、C-S-H主特征峰均低于常温下的水泥净浆,7 d龄期无外加剂的水泥净浆未出现AFt衍射特征主峰,而7 d龄期掺外加剂的水泥净浆出现了AFt衍射特征主峰,有利于早期充填体强度的提高;无论低温下的水泥净浆是否掺外加剂,两者的TG-DSC、DTG曲线类似,存在5个吸热峰和4个失重峰;7 d龄期掺外加剂的水泥净浆的TG曲线位于无外加剂水泥净浆的TG曲线下方,其失重峰也高于无外加剂水泥净浆,有利于早期充填体生成更多水化产物;低温环境下,添加Na_(2)CO_(3)、NaOH可明显提高充填体早期强度,但不利于中后期强度增长。

The introduction of filling technology into alpine regions can effectively reduce mining damage to the environment. Aiming at the lack of research on the mechanical properties and consolidation mechanism of the tailings cemented backfill at low temperature, the experiments of uniaxial compression, XRD analysis, thermal analysis and SEM observation were carried out to study the filling body specimens under curing at 5 ℃, the strength evolution law and consolidation mechanism of cemented filling body in low temperature environment were analyzed and discussed from characterization and quantification. The results show that low temperature has a greater impact on the early strength of tailings cemented filling body, among which the main factors are in descending order: cement-tailings ratio, curing age, mass concentration. The main diffraction characteristic peaks of AFt and CSH of cement paste at low temperature are lower than those at room temperature. There is no main diffraction characteristic peak of AFt for cement paste without admixtures at 7 d age, the diffraction characteristic main peak of AFt for cement paste with admixtures at 7 d age appears, which is conducive to the improvement of the early strength of the filling body. At low temperature, the TG-DSC and DTG curves of cement paste with or without admixtures are similar, with 5 endothermic peaks and 4 weight loss peaks. At 7 d age, the TG curve of cement paste with admixtures is below the TG curve of cement paste without admixtures. The weight loss peaks of cement paste with admixtures are also greater than those of the cement paste without admixtures, which is conducive to the early generation of more hydration products in the filling body. In a low temperature environment, the additions of Na_(2)CO_(3) and NaOH can significantly increase the early strength of the filling body,but it is not conducive to the mid-to-late strength growth.