孔隙是岩土固体矿物颗粒间的空间。岩土中直径大于1毫米、重力水可于其中自由运动的孔隙，是大孔隙(macro-pore，large pore)。岩土中直径为0.01～1毫米、重力水和毛管水可存其中的孔隙，是小孔隙(small pore)。岩土中直径为0.1～10微米、无重力水但毛管现象明显的孔隙，是微孔隙(micropore)。岩土中直径为0.1微米～1毫米、具毛管特性的孔隙，称毛管孔隙(capillary pore)。粘性土中直径小于0.1微米、充满结合水的孔隙，是超微孔隙(ultramicropore)，又称超毛管孔隙(uhracapillarypore)。
If you’ve ever had to dig a hole and then fill it back in, you may have noticed a mysterious thing: there was always a little dirt left over. This can often be seen when construction crews(施工员) dig down to get at sewer pipes(污水管) or electric cables(电缆). But how can there be more dirt going in than there was coming out?
The answer is that the amount of soil itself remains the same; what has changed is the arrangement of the individual grains. To see how this happens, think of a sugar bowl. If every crystal of sugar is evenly spaced, the ratio of crystals to empty space will be 60 – 40. That’s true no matter how big the bowl: 40% of the inside will always be empty.
Now put a spoon in and smooth the surface of the sugar: all those evenly-spaced crystals will be packed down into an uneven arrangement, filling the empty spaces. The result is still a 60 – 40 ratio, only now we have a lower level of sugar, with the empty space (1)moved up top.
It’s the same with soil. Rainwater and passing feet press the soil down so that the grains lie closely together with little empty space, called “pore space(孔隙).” When the shovel pulls the soil up and scatters it in a big pile, the soil grains fall down into a pattern closer to the way they were before being packed down. Once the hole is refilled, all you have to do to make it level is get rid of that pore space — which can be easily done with the back of a shovel.
Notes:
(1)move up提升，上升;向前移动
