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Some Thoughts About Rock Mechanics Aspects of Mars Courtesy of NASA - - PowerPoint PPT Presentation
Some Thoughts About Rock Mechanics Aspects of Mars Courtesy of NASA - - PowerPoint PPT Presentation
3 rd Off Earth Mining Forum - 2017OEMF Some Thoughts About Rock Mechanics Aspects of Mars Courtesy of NASA Opportunity Curiosity Spirit mer Aydan University of the Ryukyus, Department of Civil Engineering Nishihara, Okinawa, Japan
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1) Motivation Mankind is now exploring the ways to find out the characteristics of
- ther planets and possibility of
exploiting their mineral resources.. One of most impressive images from the Apollo Program of NASA to me is the man standing next to a fractured lunar rock mass. The images from recent Mars exploration rovers showed the striking similarities between rocks on Earth and those of Mars, which motivated me to bring together some of my thoughts about the aspects of rock mechanics and rock engineering in Mars and to compare them with those of the earth. In this presentation, I will specifically consider the stress state, the characteristics of rocks and their weathering, discontinuity formations, slope and cliff stability problems and natural caves.
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Teaching Rock Mechanics and Rock Engineering in Space in my Rock Mechanics Classes in Tokai University since 2010 and University of the Ryukyus since 2014 (Rock Mechanics in Other Planets) (Contents)
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2) General Characteristics of Mars Gravitational acceleration is 0.377g of the Earth Radius is 3389 km Mean density is 3.933 g/cm3
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3-1) SURFACE TOPOGRAPHY From NASA
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3-2) SURFACE GEOLOGY OF MARS
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c) TEMPERATURE VARIATIONS Temperature difference is more than 80 degrees Subjected to Harsh Freezing and Thawing Environment provided rock is saturated From NASA Earth is 20-40 degrees
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d) INTERIOR CHARACTERISTICS From Sohl and Spohn (1997)
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4) Tectonics and Mars-quakes
From NASA
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from USGS(?)
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LARGE SCALE RIFTING TYPE MOTIONS AND ASSOCIATED FRACTURE ZONES
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LARGE SCALE SHEARING, FAULTING, FOLDING AND ASSOCIATED METAMORPHISM FAULTING SHEARING & FAULTING FAULTING, FOLDING & METAMORPHISM
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Sedimentation and Tilting Sedimentation and Discordance Volcanic Activity & Columnar Jointing Folding and metamorphism
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Seismicity - Mars-quakes
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Mars-quakes (?) No Doubt that Mars-quakes should exist as it happens in Moon
Possible Causes of Quakes a) Impacts by Meteorites b) Thermal Contraction & Expansion c) Volcanic Activity d) Large Scale Mass Movements e) Plate-tectonic Type Movements f) Daily Rotation and Annual Solar Motion InSighter Module No Instrumentation yet
100 200 300 29 30 31 5.6 5.8 6.0 6.2 TIME (DAYS) VELOCITY (km/s) ACCELERATION (mm/s 2)
VELOCITY AND ACCELERATION OF EARTH Acceleration Velocity
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5) Stress State of Earth & Mars
s1 =s3 + S¥ -(S¥ -sc)e-b
1s3
é ë ù ûe-b2T
Case 1: Hydrostatic-fluid Case 2: Mantle-crust are elastic & solid; core fluid Case 4: Same condition as above, thermo-plasticity
- Tan. Stress Max, All Compressive:
6.3 GPa at surface.
Basalt UCS is 0.6 GPa
Upper Mantle is in plastic
- state. This was the main
cause of tectonics in Earth
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- Overcoring Method
- Stress Relief & Restoration Method (Flat jack Method)
- Hydraulic Fracturing Method
- Sleeve Fracturing Method
- Acoustic Emission Method (AEM)
Compiled by Aydan and Kawamoto, 1998
Direct Techniques InDirect Techniques
- Borehole-breakout Method
- Fault-Striation Method
- Focal Mechanism Solution Method
- Blasthole Damage Method
Stress State of Mars Constitutive Law and
Thermo-plastic yielding characteristics are needed
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Proper evaluation of stress state of Mars will enable us to explain Why mountains are high and Why tectonism is less pronounced in Mars Earth Mars
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6) Rocks a) Igneous Rocks b) Sedimentary Rocks c) Metamorphic Rocks
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a) Igneous Rocks
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b) Sedimentary Rocks
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c) Metamorphic Rocks
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7) Discontinuities i) Tension discontinuities due to
- Cooling
- Drying
- Freezing
- Bending
- Flexural slip
- Uplifting
- Faulting, and
- Stress relaxation due to erosion or glacier retreation
- r man-made excavation
ii) Shear discontinuities due to
- Folding, and
- Faulting
iii) Discontinuities due to periodic sedimentation, and iv) Discontinuities due to metamorphism.
Characterization of rock mass depends upon, intact rocks, discontinuities, weathering state etc.
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Discontinuities
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Filling of Discontinuities
Healing of discontinuities
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SURFACE MORPHOLOGY OF DISCONTINUITIES
Shear strength of discontinuities are greatly affected by their surface morphology parameters
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INDUCED CRACKING OR RE-CRACKING Bending Failure Torsion-induced Failure Re-opening of healed cracks
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8) Rock weathering (Chemical or Physical)
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9) Slope Stability Problems
From Aydan 1989
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a) Large Scale Slope Failures
Partly from Bigot-Cormier & Montgomery, 2007
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Some examples of Rock Slope Stabilities on Earth (compiled from various publications by Aydan)
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b) Slope Failures in Layered Rock Mass
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b) Slope Failures in Jointed Rock Mass
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c) Actual or Potential Slope Failures in Discontinuous Rock Mass
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EARTH MARS
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d) Steep or Overhanging Cliffs in Layered Rock Mass
Coogee
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e) Failures of Overhanging Cliffs in Discontinuous Rock Mass
Coogee
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f) Stability of Precarious Rock Blocks
Açıksaray-Cappadocia
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g) Impact & Vibration Induced Mass Movements
Before Drilling After Drilling
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Rover’s Vibration Induced Mass Movements
Some wrongly interpreted as the motion was caused by fluid flow, liquefaction etc.
Before After
Motion of dry granular deposits before and after shaking
From Aydan & Ulusay (unpublished 2000)
10 20 30 40 50 10 20
- 1000
1000 TIME (sec)
SETTLEMENT (mm) CUMULATIVE AE COUNT (x 10)
BASE ACCELERATION (gal)
Sand4- dry1
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Travel length: 675 cm Inclination: 23.5 degrees Maximum Acceleration: 42.13 cm/s2 Maximum Velocity: 238.5 cm/s Basalt friction angle: >30 degrees
) tan(
m
g a
Maximum Acceleration
) tan( 2
max
m
g v
Maximum Velocity
SOME INFERENCES FROM SLIDING OF BLOCKS
10 20 30
- 0.1
0.1 0.2 0.3 0.4 0.5 0.6 0.7
TIME(sec) FRICTION COEFFICIENT(S/N) NORMALIZED ACCELERATION(a/g)
S/N Upper Block Acceleration
Mt.Fuji Basalt Saw-cut Surface
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10) Sinkholes (Impact, Solution or Rifting Induced)
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11) Properties of Rocks, Discontinuities and Rock Masses
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12) Conclusions The rock mechanics aspects of Mars are quite similar to those of the Earth. The differences result from gravitational acceleration, climatic conditions (temperature, humidity, winds), thickness of atmosphere and non or limited amount of ground water. The knowledge on the behaviour of rocks, discontinuities and rock masses acquired on the Earth can be easily used in Mars with the consideration of the differences resulting from gravitation acceleration, climatic conditions and fluid in rock masses.
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- The author heart-fully thanks the organizing committee and
the invitation to join the 2017 Off-Earth Mining Forum and to have chance to address you on my thoughts.
- The author gratefully acknowledges NASA and the people
involved in the development and operation of Mars exploration programs, Mars rovers, namely, Opportunity, Sprit and Curiosity, and processing and releasing their images on related web-sites.
- The author is solely responsible for the content, statements
and opinions made in this presentation ACKNOWLEDGEMENTS Thoughts of the author are based on Images of Mars Rovers and mostly obtained from the following web-site: https://mars.nasa.gov/mer/gallery/images.html
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