EXPLORATION GEOLOGY (ROCK MECHANICS) Flashcards
Three aspects of Geotechnical Investigations during exploration?
1) Soil (Overburden)
2) Rocks
3) Subsurface Water
Uncemented material at or near the surface and can include weathered or broken rock
Soil
Solid material which is excavated during mining to reach and extract the ore
Rock
Part of the soil and the rock and is found in the pores, and in joint, fractures and fissures
Subsurface water
2 types of Geotech data
1) Subjective Data - Core loging and sides of excavation
2) Quantitative Data - measurements such as rock and joint stress, virgin rock stress
What type of Geological Data is extremely important in mine Planning?
Strutctural Information
(Joints, Cleavage, Cleats, Beddnig Fissures, faults)
(Fracture spacing, attitude and infill)
The subjective description of the core wherein pieces of core greater than 10 cm are measured and their length summed then divided by the total length of the core run and expressed as percentage
Rock Quality Designation (RQD)
(Low% Poor Rock Quality
High % High Rock Quality)
what are the subjective tests included in the determination of Rock Mass Rating (RMR)?
1) Strength of Intact Rock
2) RQD
3) Joint Spacing
4) Conditions of Joints
5) Ground Warer Conditions
Use of RMR?
Can use to calculate stand up time of an underground unsupported excavation
Rock Material Strength
Unconfined strength
Extremely Strong
> 250 Mpa
Very Strong
100-250 Mpa
Strong
50-100 Mpa
Medium
25-50 Mpa
Weak
5-25 Mpa
Very Weak
1-5 Mpa
Sound RQD
> 100%
Fissured RQD
90-100%
Jointed RQD
50-90%
Fractured RQD
1-50%
Shattered RQD
<1%
Excellent
> 90
Good
75-90
Fair
50-75
Poor
25-50
Very Poor
<25
Main properties of Rock used for quantitative Assessment?
1) Porosity and Permability - Assessment of subsurface water
2) SG (Bulk Density) - Mass of the Rock
3) Durability and Slakability - reveals the effects of alternate wetting and drying of the rock
4) Sonic Velocity - indication of fracture intensity of a rock
5) Rock Strength- Most important property
When forces are directed towards each other but not necesarrily in line
Shear Stress
Response of the material to stress by producing deformation
Strain
The linear relationship between stress and strain
Hooke’s Law
The constant connecting stress and strain and gives the measure of stiffness
Young’s modulus/ Modulus of Elasticity
How much is the tensile (pulling strength) of a rock?
Generally, <1/10 compressive strength
a point above which the strain is not anymore recoverable
Yield Point
What type of Material is Granite
Perfectly Elastic
What type of Material is Clay?
Plastic
What type of Material is Marble?
Elastoplastic
What type of material is shale?
Ductile
What is important to take note in exploration programs in reference to hydrogeology?
Note where the water table is encuntered in a borehole
(Water pressure, and volume of water)
A borehole or wireline survey used to obtain a quantitative estimate of the contribution a partibular bed or joing may make to the water inflow at a site
Packer Test
Descrbies how much water is stored or a rock can hold in the voids in between grains, and joints
Porosity
Measure of how easily such stored water can flow through and out the rock
Permeability
Relative Ease of Flow
Hydraulic Conductivity
The rate at which the head water change laterally with distance
Hydraulic Gradient
Darcy’s law which is the emirpical description of flow of water is expressed by
v = Ki
v-Spcecific discharge or the velocity or laminar flow of water through a porous medium
K- Hydraulic conductivty
i- Hydraulic gradient
a tube which is used to measure the level to which the water rises (Head of Water) when a borehole is drilled
Piezometer
Rocks which are permable and allow water to flow freely through joints, fractures and pores
Aquifers
rocks which have a low peremability and are impervious and do not allow water to flow through them
Aquicludes
