measurement of rock discontinuity

Question 1

discontinuity

Answer 1

• fracture or plane of wekaness in the rock mass

- common ones: bedding, joints, and fissures

Question 2

Discontinuity characteristics

Answer 2

• rock material: intact rock with no discontinuity
• discontinuities may be filled with different materials such as soils or contain nothing at all
• discontinuities are huge in engineering with geology

Question 3

describing discontinuities

Answer 3

location
type
orientation
spacing
persistence
roughness
aperture
infilling
seepage

Question 4

types of continuities with #’s and their causes

Answer 4

types: caused by:
1. bedding sedimentary
7. cleavage or cooling actions
- ————————————–
2. fault or fault zone mechanical
3. tension crack actions
4. joint after
5. fissure formation
- —————————————-
6. foliation metamorphic
8. schistosity actions

Question 5

orientation of discontinuities

Answer 5

page q08 - 3 - 10, fairly thorough and important

Question 6

spacing of discontinuities

Answer 6

• width of rock mass between 2 adjacent discontinuities
• widest category: >6 m
• closest category: <20 mm

Question 7

discontinuity persistence

Answer 7

• area (2D) over which a discontinuity persists
• very difficult to measure and often guesstimated by visible trace length and then categorized into different sets: persistent, sub-persistent, non-persistent.

Question 8

roughness of discontinuities

Answer 8

• although often treated as a plane, discontinuities can be rough/curved
• categorized into 2 descriptions:
  waviness: large scale roughness (10’s of m)
  uneveness: small scale roughness(1cm-1m)
• also called first order and second order roughness respectively
• look to page q08 - 6 - 10 for measurement details

Question 9

infilling

Answer 9

-material that separates adjacent rocks walls of a discontinuity
-4 aspects:
nature of infilling
consistency of infilling
widths
seepage

Question 10

Nature of infilling

Answer 10

categories with numbers:
0 clean
1 surface staining
2 decomposed/disintegrated rock
3 non-cohesive soil
4 cohesive soil
5 quartz
6 calcite
7 manganese
8 kaolin
9 other (must be specified)

Question 11

consistency of infilling

Answer 11

soil strength:
1-5 goes from very soft to hard
rock strength:
6-13 goes from extremely weak to extremely strong

Question 12

Widths of infilling

Answer 12

-must include:
max width
min width
and average width in mm

Question 13

seepage of infilling

Answer 13

• is the material dry, damp, wet? do they show permanent seepage? all of these create the actual reportable description on these infillings

Question 14

standard setup for recording discontinuities

Answer 14

Title:
gen info
record No
site
date
operator
data sheet # in the
then write all of the facts for discontinuity description

Question 15

objective survey

Answer 15

• use coordinate system to measure # of discontinuities on a surface
• takes long time, may require machine for analysis of data, not all important points may be found

Question 16

subjective survey

Answer 16

• pick out discontinuities that look important to project,

- quick, better for general analysiis