板下脱空
cavity beneath slab
come to nothing below the plank
板下地温
soil temperature under the plate
下压油缸
pushing down oil cylinder
低温大压下工艺
low temperature high reduction
板下脱空形态
Cavity form beneath road slabs
后侧围板下延伸部
Quarter panel lower extension
水下超压干式焊
excessive-pressure welding