Rock Mass Classification Urban Underground Space Engineering Hebei University of Engineering rockbolt steel sets civil engineering RQD heading / face NATM wire mesh shot crete parameter stress field span spall slab rock brust RMR blast bench ① [During the feasibility and preliminary design stages of a project, when very little detailed information on the rock mass and its stress and hydrologic characteristics is available], the use of a rock mass classification scheme can be of considerable benefit. ② At its simplest, this may involve using the classification scheme as a check-list to ensure that all relevant information has been considered. ③ At the other end of the spectrum, one or more rock mass classification scheme can be used to build up a picture of the composition and characteristics of a rock mass to provide initial estimates of support requirements, and to provide estimates of strength and deformation properties of the rock mass. ① It is important to understand that the use of a rock mass classification scheme does not ( and can not ) replace some of the more elaborate design procedures. However，② the use of these design procedures requires access to relatively detailed information on in situ stress， rock mass properties and planned excavation sequence， none of which may be available at an early stage in the project. ③ As this information becomes available， the use of the rock mass classification schemes should be updated and used in conjunction with site specific analyses. LET’S GO 。。。以下略