This document discusses rock mechanics and provides information on key concepts such as the classification of rocks, stress, strain, factors affecting rock behavior like temperature and pressure, different rock textures, brittle behavior, shear failure, rock strength, challenges in rock mechanics like spalling and wedge failure, and causes of such challenges like insufficient knowledge. It covers topics like sedimentary, metamorphic and igneous rocks, definitions of stress and strain, relationships between pressure, depth and temperature, and how internal and external conditions influence rock properties.

1. ROCK
MECHANICS
:
GROUP
MEMBERS:
USMAN IRFAN :
SAIF RIAZ KHAN:
WAJAHAT ALI
SHAH:
MALIK BEHZAD :
HASSAN ALI:

2. What is rock
– Aggregates of mineral grains that are connected by strong
and permanent forces

3. Classification of rocks:
– Three main classifications
– Sedimentary
– Metamorphic
– Igneous

4. Rock mechanics
Theoretical and applied science of the mechanical behavior
of rock and rock masses; compared to geology, it is that
branch of mechanics concerned with the response
of rock and rock masses to the force fields of their physical
environment

5. ROCK MECHANICS
– The study of rock behavior in the solid state under
varying environmental and internal conditions
– Main focus is how rocks respond to applied stresses,
especially those that naturally occur due to:
– Gravity
– Mantle Convection
– Plate Tectonics
– Diapiric Movements: magma, salt diapirs

6. Challenges and
opportunities
– New ideas to solve the challenges provide opportunities for
economic benefits

7. Stress
– Same as Pressure
– = Force/Area
– Units in Earth Sciences are MPa = 106
Pa = 10 bars =10 atm

8. STRAIN
– Response to or result of applied stress
– Linear strain is defined as (L1 – L0)/L0
– Volumetric strain = (V1-V0)/V0
– Areal Strain = (A1-A0)/A0
– Strain is usually expressed as a percent change

9. ENVIRONMENTAL
CONDITIONS
affecting rock behavior
Stress Factors:
– Applied Stress
– Stress History
– Duration
– How stress applied over time
– Temperature
– Pore Fluids and Pressure

10. Lithospheric Pressure
Rocks which are generally associated in field
belongs to lithosphere(crust and upper
mantle)
By increasing depth over burden increases
that results in changing rock properties such
as density, rigidity etc.

11. Pressure vs. Depth in Earth

12. Geothermal Gradient
– T increases in the Lithosphere at 250
C/km
– T continues to increase all the way to the core, but at a
lower rate
– The melting T of Quartz is 573-870 0
C
– The melting T of Feldspar >1100
– The melting T of calcite is 910

13. Temperature vs. Depth in
the Earth

15. INTERNAL CONDITIONS
affecting rock behavior
– Composition (silicates and oxides most resistant to
strain)
– Texture/Fabric (phaneritic most resistant)
– Pores, cracks, flaws
– Degree of Weathering (minerals that weather from
oxides and silicates to other compounds are
weakened)
– Presence of fluids in pores or cracks

16. Rock Texture/Fabric
– Grain size
– Interlocking or grains in cement?
– Sorting
– Foliation/ non-foliated
– Sedimentary layering

17. Textures
Note: Most Strain is not due to breaking bonds,
but is due to slip of grains against each other,
or between grains and cement

18. Porosity vs. Depth

19. Rigid and Brittle Behaviors
– Rigid:
– No strain, no response
– Most rocks show rigid behavior at room T and no Pc, and at stresses
below Pa
– Brittle:
– No strain before failure
– In ideal brittle behavior, if stress is removed before rock fails, there
will be no internal signs of strain

20. Important terms
– Brittle failure
– Shear failure
– Standup time
– Rock strength
– Spalling
– Wedge failure
– Squeezing

21. Brittle Behavior: Shear Failure:
A material is brittle if, when subjected A shear load is a force that tends to produce a
to stress, it breaks without significant sliding failure on material along a plane that is
deformation (strain). Parallel to the direction of force.

22. Rock strength
– The compressive strength o f rock is a function of the
confining pressure. • As the confining pressure increases so
does the strength.( Goodman, Intro to Rock Mechanics.)

23. Spalling:
– Spall are flakes of a material that are broken off a larger
solid body and can be produced by a variety of
mechanisms, including as a result
of weathering, cavitation. Spalling and spallation both
describe the process of surface failure in which spall is
shed.

25. Wedge failure
– Wedge failure of rock slope results when rock mass slides
along two intersecting discontinuities forming a wedge-
shaped block.

27. Squeezing
Generally compression
Forces acts in opposite direction
Results in decrease in length, volume, area.

28. Challenges
–Spalling
–Standup time of rock
–Maximum cost risks
–Challenges in infrastructure
–Support challenges during deep excavation
–Wedge failure
–Brittle Rock challenges

29. Cause of Challenges
– Not sufficient Knowledge about behaviour of rock
– Ignorance
– Neglecting small observations
– Not sufficient Familiarity with Rock mechanics

30. Conclusion

31. END