基于测线法而统计的一维空间的节理密度，对测线的方位较敏感，且难以全面反映节理在三维空间内的发育情况，通常难以达到足够的精确度。岩体体积节理数J^_v是对节理密度的三维统计，能较好地反映节理密度。目前国内外比较流行的几种围岩分级方法中，其评价指标都与岩体体积节理数J^_v有着重要的关联。准确获得岩体体积节理数J^_v对于围岩分级有着非常重要的作用。介绍了各种岩体的岩体体积节理数的统计方法及其在 RMR 法、 Q 法、 GSI 及 BQ 法围岩分级系统中的应用，并结合工程实践对其进行运用。

On the basis of statistics of joints of the one-dimensional space, the method of scan line to density of joint rock mass is sensitive to the line direction and could not entirely reflect the joint developmental condition on the three  dimensional space. Usually, this approach could not ensure enough accuracy. While, the volumetric joint count J^_v which is based on the three-dimensional space of a rock mass, could reflect the joint density well. Nowadays, in the main surrounding rock classification methods at home and abroad, their evaluation indexes have a significant connection with the volumetric joint count J^_v. So it is very important to acquire the accurately volumetric joint count J^_v value. This paper introduces the calculation methods of volumetric joint count for different kinds of rock masses and its application in RMR, Q, GSI and BQ surrounding rock classification methods, and applies these methods in connection with the practical engineering.