The riser's inner hollowcore (a pipe within a pipe) is reserved for the drill string.
立管内部核心是空心的(管中管)，留给钻柱使用。
2
Simple and enormous intersecting walls give a balanced symmetry but are also the means by which the structure stands at the height of a 14-storey building, with an entirely hollowcore.
简单而巨大的相交墙赋予了平衡的对称性，但也意味着结构具有14层高建筑物的高度，具有完全空心的核心。
3
Doors of hollowcore, even when locked, are vulnerable to break-ins.