合法周边参与
legitimate peripheral participation
井周钻孔补砾
filling gravel for boreholes around well
圆周钻孔圆头螺母
round nut with drilled holes in side
精密深孔钻孔工具
precision deep hole drilling tool
大孔钻孔
big-diameter hole drilling
洞室加钻孔爆破
chamber blasting plus drilling