Mechanical Parameters of Deep-Buried Coal Goaf Rock Mass Based on Optimized GSI Quantitative Analysis

Table 3

New rock mass structure classification by and distance between discontinuities.

Rock mass integrity	Rock mass integrity index	Average distance between discontinuities (m)	Number of structure sets	Structure of rock mass
Extremely intact rock	＞0.75	＞1.0	1–3	Intact or massive rock with few widely spaced discontinuities
Relatively intact rock	0.75～0.55	1.0–0.4	3-4	Blocky rock mass consisting of cubical blocks formed by 3-4 intersecting discontinuity sets
Relatively fractured rock	0.55～0.35	0.4–0.2	3-4	Very blocky-interlocked and partially disturbed mass with multifaceted angular blocks formed by 3-4 joint sets
Fractured rock	0.35～0.01	0.2–0.06	4	Block folded by 4 intersecting discontinuity sets
Extremely fractured rock	＜0.01	0.06–0.02	4 or more	Disintegrated, poorly interlocked, and heavily broken rock mass made up of mixture of angular and rounded rock pieces
Conglomeratic rock mass		＜0.02	4 or more	Laminated/sheared, with lack of blockiness due to close spacing of weak schistosity or shear planes