It indicates the pore space within the rock structure.
Ideally, the total pore space should be 50% of the soil volume.
Sometimes, under the right conditions, some of the pore space in the rock is occupied by other liquids or gases.
Many of the rocks in Taiwan have low pore space and have little ground water.
The environment in which each of the cements is found depends on the pore space available.
Above a capillary fringe, pore spaces have air in them too.
The more pore space in a soil the lower the value for bulk density.
Porosity is a measure of the total pore space in the soil.
Both quantities are given as a fraction of the total pore space.
These pore space is filled with bounded water by definition.