为解决深厚回填体上部注浆固结的问题，在理论分析的基础上进行上部回填体注浆加固设计，通过数值模拟分析注浆效果，分析表明注浆体一方面通过填充回填洞砟孔隙增加了上部荷载，起到了堆载压密效果，另一方面有效隔离了列车动载向下传递，防止回填体工后扰动沉降。在注浆工程实践中重点考察注浆质量控制，解决因周边止浆墙成型差导致的注浆缺陷问题，实现封闭范围内密实注浆固结，并采用开挖检测测试方法对注浆效果进行检测评定。在上部注浆施工完成后对回填体表层沉降进行监测，监测结果表明采用“洞砟回填+上部注浆”加固方式处理溶洞技术可行，沉降可控。

The grouting consolidation of deep and thick backfill of giant karst of railway tunnel is of great significance. Hence, the grouting reinforcement design of the upper backfill is carried out on the basis of theoretical analysis, and the grouting effect is analyzed through numerical simulation. The analytical results show that the grouting fills the pores of muck backfill to increase the upper load of karst, which plays the effect of compaction and isolates the train′s dynamic load from passing down to prevent the backfill from disturbing settlement after construction. In the practice of grouting engineering, attentions are paid on the grouting quality control to solve the problem of grouting defects caused by the poor forming of the surrounding grouting wall, and realize the dense grouting consolidation in the enclosed area. The grouting effect is tested and evaluated. After the completion of upper grouting construction, the surface settlement of the backfill is monitored, and the monitoring results indicate the feasibility of the karst cave treatment method of muck backfill + upper grouting reinforcement in terms of settlement control.