chapter 4 rock mass (1)
DESCRIPTION
ROCKTRANSCRIPT
![Page 1: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/1.jpg)
Section 3: Field Description of Rock Mass in Engineering
Practice.
Practical 4: Systematic Description of Rocks and Rock Discontinuity.
![Page 2: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/2.jpg)
Introduction
• Rock Mass should be described first as a rock material, and its includes: – Colour.– Texture + grain size.– Structure (fabric).– Weathering state.– Rock group name and specific geological name.– Engineering properties + strength.
![Page 3: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/3.jpg)
![Page 4: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/4.jpg)
• The shear strength of a rock mass and its deformability are very much influence by discontinuity pattern, it geometry and how it is developed.
• Important factor in rock stability:– Number of set of discontinuities which intersect.– Number of set also effect the degree of overbreak.
Introduction (cont…)
![Page 5: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/5.jpg)
• The description of jointed rock masses base on:– Incidence of discontinuity.– Geometry of discontinuity.– Surface of discontinuity.– Flow of water in discontinuity.
Introduction (cont….)
![Page 6: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/6.jpg)
Discontinuities
• Discontinuities are fracture and plane of weakness in the rock mass.
• Tensile strength reaches minimum value across discontinuities.
• Joint frequently appear as parallel sets of joint planes (called joint set).
• Single faults may be encountered in a rock mass, but seldom more than one.
![Page 7: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/7.jpg)
![Page 8: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/8.jpg)
• The data needs for each discontinuity:– Continuous or not.– Spacing (Table 4.1 pg 83)– Nature of discontinuity.– Attitude of discontinuity (horizontal, vertical,
inclined).
Discontinuities (cont…)
![Page 9: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/9.jpg)
Discontinuities (cont…)
![Page 10: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/10.jpg)
Discontinuities (cont…)
![Page 11: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/11.jpg)
• Terminology: – Type of discontinuity:• Fault, vein, joint, fracture, cleavages, bedding plane,
etc.
– Number of discontinuity set. – Location and orientation – scan line + strike & dip.– Spacing between adjacent discontinuities.– Aperture of discontinuity surfaces (Table 4.2 pg
84)– Infilling – clay, quartz, etc.
Discontinuities (cont…)
![Page 12: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/12.jpg)
![Page 13: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/13.jpg)
• Terminology (cont…):– Persistence or the extent – continuous or not.– Nature of discontinuity surface – Table 4.3 pg 84.– Discontinuity spacing in 3-D – Table 4.4 pg 85 and
Figure 4.4 pg 86.• Blocky• Tabular• Columnar
– Weathered and alteration conditions – Table 4.5 pg 86.• Weathering grade I, II, III, IV, V or VI.
Discontinuities (cont…)
![Page 14: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/14.jpg)
Discontinuities (cont…)
![Page 15: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/15.jpg)
Discontinuity Survey
Direct Discontinuity Survey Using Scan Line
2 types of Discontinuity Survey: Direct and Drill holes.
![Page 16: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/16.jpg)
Streographic Representation
![Page 17: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/17.jpg)
Pic: University of Maryland, Department of Geology
![Page 18: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/18.jpg)
One of Kajang Housing Development area: Ehsan from SEADPRI UKM
![Page 19: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/19.jpg)
![Page 20: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/20.jpg)
![Page 21: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/21.jpg)
• Plane failure: 1 plane failure occur at the discontinuity line of______
outside the slope face in the direction of _____N
• Wedge failure: 1 wedge failure occur at the intersection of 2 discontinuity
line of line _______and line _______ outside the slope face in the direction of ________N.
• Toppling failure: 1 toppling failure occur at the discontinuity line of _________
inside the slope face in the direction of _______N.
Failure:
![Page 22: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/22.jpg)
• Draw the streonet: (Try exercise 4.2 pg 105)1. Draw the circle.2. Indicate the north pole.3. Draw the slope face: given 358o/45o.4. Mark the strike / facing direction = 358o.5. Rotate the tracing paper:
If direction ≥ 180o, rotate it to west position (270o). If direction ≤ 180o, rotate it to east position (90o).
6. Count from outside into inside: for angle 45o.7. Draw the line from 0o to 180o along that side, using solid
line.8. Rotate the tracing paper back to datum: North.
Streographic Representation (cont..)
![Page 23: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/23.jpg)
9. Draw the discontinuity data set: given 87o/80o.10. Mark the strike / dip direction = 87o.11. Rotate the tracing paper:
If direction ≥ 180o, rotate it to west position (270o). If direction ≤ 180o, rotate it to east position (90o).
12. Count from outside into inside: for angle 80o.13. Draw the line from 0o to 180o along that side, using
discontinuous line.14. Rotate the tracing paper back to datum: North.15. Repeat procedure 9 to 14 for the rest.
Streographic Representation (cont..)
![Page 24: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/24.jpg)
Points to remember:• Never write on the projection itself; always
write on the tracing paper.• Use pencil, not pen.• Make notes on the tracing paper as you go.• When rotating, always use the normal to
plane.
Streographic Representation (cont..)
![Page 25: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/25.jpg)
Exercise 1: Slope Stability• Slope Face = 162/68. Please identify the possible
failure.• Discontinuity readings are:
162/58 68/86 322/69 123/57 300/56
98/76 106/80 126/54 93/72 183/74
216/48 16/62 100/57 64/70 78/56
93/56 165/65 81/56 284/28 108/58
144/72 182/74 162/60 337/87 154/88
176/84 264/82 178/68 274/32 128/38
![Page 26: Chapter 4 Rock Mass (1)](https://reader035.vdocuments.us/reader035/viewer/2022062304/563dbbb5550346aa9aaf948e/html5/thumbnails/26.jpg)
THANK YOU