best notes for geology students

1. ENGINEERING GEOLOGY
CE-226
Lecture 05: Discontinuities & its Types

3. Discontinuity is a collective term used here to include the following
1. Fractures (joints)
2. Faults
3. Bedding plane

5. • Orientation of discontinuities is the attitude of the discontinuities.
Depending upon the slope of the discontinuity rock has different strength
at different direction.
• Spacing is the perpendicular distance between the two adjacent
discontinuities of the same set
• In rough discontinuity surfaces due to low friction shear strength is high
• Aperture is the open spacing present in the rock due to discontinuity
present in it
• Fillings are the materials filled in the open apertures of discontinuities
• Seepage is the flow of water under gravitational forces in a permeable
medium

6. 1. FRACTURES & JOINTS
• Planar discontinuities involving no relative displacement of the
adjacent rock blocks.
• Joints are the result of expansion and contraction due to cooling and
warming of the Rocks.
• “Fracture zones” are zones of closely-spaced and highly
interconnected discrete fractures
• Joints allow groundwater and other liquids to move through rocks.

8. 2. FAULTS
• Faults are fractures (cracks) in rocks along which movement has
occurred
• Faults also create environmental effects such as the movement
of groundwater, and can cause hazards such as rock slides and
earthquake.
• Faults are classified according to which direction the rocks moved
along the fault
a) Normal Faults,
b) Reverse Faults,
c) Thrust Faults,
d) Strike-slip Faults

9. • In the left diagram, the rock block is un-faulted, but contains a weakness. The
right diagram shows the block after faulting.
• The fault plane is the plane on which movement occurs

13. 3. BEDDING PLANES
• Beds are enclosed or bounded by sharply defined upper and
lower surfaces or bedding planes.
• These surfaces are probably the easiest physical features of
sedimentary rocks to identify in outcrop.
• They are used to subdivide successions of sedimentary rock into
their beds and are traditionally used to determine the relative order
and timing of the accumulation of the sediments forming the beds

16. 4. FOLDS
• At depths, Joints and faults are inhibited to confining pressure as well
as increasing temperature which Rocks the ability to flow rather than
break.
• Rock formation are bended and buckled into a series of antiform and
synform

19. Quiz 2
• What is a “Sinkhole”? How it is formed? Where on earth this
phenomenon occurs most frequently?