Pore ​​number

The number of pores , also called the number of pores or, rarely, the relative pore space , is a parameter for characterizing a porous substance. It is a measure of how much space the actual solid fills due to its grain size or fissures within a certain volume or which cavities it leaves behind in it. The pores are usually filled with air and / or water.

definition

The pore number is defined as the ratio of the void volume to the solid volume . So it applies ${\displaystyle e}$ ${\displaystyle V_{\text{Hohl}}}$ ${\displaystyle V_{s}}$

${\displaystyle e={\frac {V_{\text{Hohl}}}{V_{s}}}}$

The void volume is the total volume of all fissures, pores and other voids in the solid, so the following applies ${\displaystyle V_{\text{Hohl}}}$

${\displaystyle V_{\text{Hohl}}+V_{s}=V_{\text{ges}}}$.

${\displaystyle V_{\text{ges}}}$denotes the total volume here. The index for the solid volume stands for solid . This results in an alternative definition ${\displaystyle s}$ ${\displaystyle V_{s}}$

${\displaystyle e={\frac {V_{\text{ges}}-V_{s}}{V_{s}}}}$.

In addition to the notation as, there is also the as . ${\displaystyle e}$ ${\displaystyle \varepsilon }$

Relationship to porosity

The number of pores is closely related to the porosity and can also be expressed by this. So it applies directly to the definition of porosity ${\displaystyle \Phi }$

${\displaystyle e={\frac {\Phi }{1-\Phi }}}$

Conversely, the porosity can also be represented using the number of pores and then results

${\displaystyle \Phi ={\frac {e}{1+e}}}$.

Range of values

In contrast to porosity, which has values ​​between zero and one, the pore number can have values ​​between zero and infinity. A pore number of zero corresponds to a solid solid without pores. The porosity is also zero here. If the pore number is infinite, the solid consists only of pores and has a porosity of one. This case is only of theoretical interest, since then, more precisely, it is no longer a solid.

Individual evidence

1. ^ ^{A b} Horst-Robert Langguth, Rudolf Voigt: Hydrogeological methods . 2nd Edition. Springer-Verlag, Berlin / Heidelberg 2004, ISBN 3-540-21126-8 , pp. 144 .
2. ^ Bernward Hölting, Wilhelm Georg Coldewey: Hydrogeology . Introduction to General and Applied Hydrogeology. 8th edition. Springer-Verlag, Berlin / Heidelberg 2013, ISBN 978-3-8274-2353-5 , pp. 15 , doi : 10.1007 / 978-3-8274-2354-2 .

swell

• Dieter D. Genske: engineering geology . Basics and application. 2nd, revised and updated edition. Springer-Verlag, Berlin / Heidelberg 2014, ISBN 978-3-642-55386-8 , p. 195 , doi : 10.1007 / 978-3-642-55387-5 .