Engineering Rock Mechanics

178 Testing techniques

Aperture

Filling

line of least resistance, rising towards the lower stressed region in the
drill core. Thus, the major principal stress, CTH, acts E-W and the minor
principal stress, q,, acts N-S. The ratio of disc thickness to diameter
indicates (according to the diagram included above from Haimson, 1997)
that the local OH could be about 120 MPa.

Feeler gauge

Visual

Qt 1.2 With reference to fracture property measurements made dur-
ing a site investigation

• on borehole rock core,


• on the borehole walls, and


• on rock exposures.
  Complete the table below indicating your opinion of how well you
  think that the listed fracture properties can be measured or es-
  timated. The first column of the table represents the ten fracture
  measurements recommended by the ISRM, as in Fig. 7.7. Use the
  letters 0 for Good, M for Medium, and P for Poor.

Seepage

Number of sets

Block size

I Wall strenath I Schmidt hammer I I I I

Timed observations

Stereographic projection

3-D fracture frequency

~~

I Orientation I Compass-clinometer I M I G G

At 1.2 The completed table follows. These measurements cover a wide

range of attributes - rock mass geometry, intact rock strength and

I Characteristic I Measurementmethod I Core I BkIwall I Exposure I

Spacing

Persistence

Roughness

Measuring tape G G G

Measuring tape P P G/M

Against reference chart M P G

Wall strength

Aperture

Filling

Seepage

Number of sets

Block size

Schmidt hammer M P G

Feeler gauge P M G

Timed observations P PIM G

Stereographic projection M G G

3-D fracture frequency P P G

Visual P P G