Vertical cutoff wall has been employed for decades to control groundwater flow and subsurface contaminant transport. The barrier performance of cutoff wall material may significantly deteriorate under dry-wet cycles due to precipitation, drought, and groundwater fluctuation. This study adopted active magnesium oxide (MgO) particles to enhance the durability of geopolymer cutoff wall backfill (GCWB) under dry-wet cycles. The influence of particle size and proportion of MgO on the unconfined compressive strength (UCS), hydraulic conductivity, self-healing capacity and durability of GCWB were comprehensively examined. The results indicate that the incorporation of active MgO particles hindered the geopolymerization process of GCWB to a certain extent, leading to an increase in hydraulic conductivity and a decrease in UCS. But the overall performance of GCWB was still favorable. The hydraulic conductivity of samples with MgO gradually increased to more than 1 × 10⁻⁸ m/s after at least two dry-wet cycles. In the subsequent cycles, the samples with MgO exhibited a pattern of first gradually declining then ascending in hydraulic conductivity. This is due to hydration and carbonization of the remained MgO in matrix during the dry-wet cycles, which converts into oxygen-rich carbonates, forming well-ramified networks and reducing the proportion of macropores. Thus, the durability of GCWB with MgO is significantly more favorable than that devoid of MgO. In particular, large particle size MgO can exert more persistent self-healing effect, endowing the samples with superior durability under the prolonged dry-wet cycles.

几十年来，垂直截水墙一直被用来控制地下水流和地下污染物输送。由于降水、干旱和地下水波动，干湿循环下防渗墙材料的阻隔性能可能会显着恶化。本研究采用活性氧化镁（MgO）颗粒来增强地质聚合物防渗墙回填（GCWB）在干湿循环下的耐久性。综合考察了MgO的粒径和比例对GCWB无侧限抗压强度（UCS）、导水率、自修复能力和耐久性的影响。结果表明，活性MgO颗粒的掺入在一定程度上阻碍了GCWB的地质聚合过程，导致导水率增加，UCS降低。但GCWB的整体表现仍然良好。 经过至少两次干湿循环后，^{含有MgO的样品的水力传导率逐渐增加至1×10 -8 m/s}以上。在随后的循环中，含有MgO的样品的导水率表现出先逐渐下降然后上升的模式。这是由于基质中残留的MgO在干湿循环过程中发生水合作用和碳化，转化为富氧碳酸盐，形成良好的分枝网络并减少了大孔的比例。因此，含有 MgO 的 GCWB 的耐久性明显优于不含 MgO 的 GCWB。特别是，大粒径的MgO可以发挥更持久的自修复作用，使样品在长时间的干湿循环下具有优异的耐久性。