充填砾石与地层砂粒度中值比
median pack-to-formaton grainsize ratio
渠床砂砾石料垫层
grit and gravel in the channel bed
一步法转换充填砾石工具
one-trip crossover packing system
卵石填料
filling material of cobble stones for sub-grade
生物沸石填料
biological zeolite filling
biological zeolite packing