Ch. 4 - Clay Minerals, Rock Classification Page 1 Learning Objectives
Ch. 4 - Clay Minerals, Rock Classification Page 2 Symbols
Ch. 4 - Clay Minerals, Rock Classification Page 3 Clay Minerals and Structure
Ch. 4 - Clay Minerals, Rock Classification Page 4 Silica Sheets - Hexagonal Network of Silicon Tetrahedral
Ch. 4 - Clay Minerals, Rock Classification Page 5 Alumina Sheets - Octrahedral Network of Aluminum Octahedron
Ch. 4 - Clay Minerals, Rock Classification Page 6 Gibbsite and Brucite Sheets and Isomorphous Substitution
Ch. 4 - Clay Minerals, Rock Classification Page 7 Building Clay Minerals for Tetrahedral and Octahedral Sheets Primary valence bonding between tetrahedral and octahedral sheet Van der Waals bonds between gibsite sheets in pyrophyllite Hydrogen bonding between O and OH in Kaolinite Interlayer cation bonding in Illite and Chlorite Interlayer bonding by polar molecules in Smectite and Vermiculite
Ch. 4 - Clay Minerals, Rock Classification Page 8
Ch. 4 - Clay Minerals, Rock Classification Page 9 Phyllosilicates
Ch. 4 - Clay Minerals, Rock Classification Page 10 Intersheet Bonding
Ch. 4 - Clay Minerals, Rock Classification Page 11 Bonding (cont.) and Cation Exchange Capacity (see diffused double layer)
Ch. 4 - Clay Minerals, Rock Classification Page 12 Cation Exchange Capacity (cont.) Friday, January 04, 2013 11:43 AM Standard values Kaolinite 3-15 Halloysite 2H 2 O 5-10 Halloysite 4H 2 O 40-50 Montmorillonite-group 70-100 Illite 10-40 Vermiculite 100-150 Chlorite 10-40 Glauconite 11-20+ Palygorskite-group 20-30 Allophane ~70 These are the values reported by Carroll (1959) [5] for the cation-exchange capacity of minerals in meq./100g at ph of 7. Pasted from <http://en.wikipedia.org/wiki/cationexchange_capacity> The equivalent (symbol: eq or Eq), sometimes termed the molar equivalent, is a unit of amount of substance used in chemistry and the biological sciences. A historical definition, used especially for the chemical elements, describes an equivalent as the amount of a substance that will react with one gram of hydrogen, or with eight grams of oxygen, or with 35.5 grams (1.25 oz) of chlorine, or displaces any of the three. [3] In practice, the amount of a substance in equivalents often has a very small magnitude, so it is frequently described in terms of milliequivalents (meq or meq), the prefix milli denoting that the measure is divided by 1000. Very often, the measure is used in terms of milliequivalents of solute per litre of solvent (or millinormal, where meq/l = mn). This is especially common for measurement of compounds in biological fluids; for instance, the healthy level of potassium in the blood of a human is defined between 3.5 and 5.0 meq/l. Pasted from <http://en.wikipedia.org/wiki/equivalent_(chemistry)> Steven F. Bartlett, 2013
Ch. 4 - Clay Minerals, Rock Classification Page 13 Kaolinite and Halloysite
Ch. 4 - Clay Minerals, Rock Classification Page 14 Pyrophyllite and Smectite
Ch. 4 - Clay Minerals, Rock Classification Page 15 Montmorillonite and Vermiculite
Ch. 4 - Clay Minerals, Rock Classification Page 16 Illite and Chlorite See next page
Ch. 4 - Clay Minerals, Rock Classification Page 17 Illite and Chlorite Illite Chlorite
Ch. 4 - Clay Minerals, Rock Classification Page 18 Simple Way to Identify Type of Clay Mineral Grouping of soils by Atterberg limits on A-line chart
Ch. 4 - Clay Minerals, Rock Classification Page 19 Specific Surface
Ch. 4 - Clay Minerals, Rock Classification Page 20 Activity
Ch. 4 - Clay Minerals, Rock Classification Page 21 Absorbed Water inner outer layer Polar water molecules and cations are strong bound to the clay surface in the inner layer and the absorbed water in the inner layer cannot be removed by drying because of this bond
Ch. 4 - Clay Minerals, Rock Classification Page 22 Absorbed Water (cont.)
Ch. 4 - Clay Minerals, Rock Classification Page 23 Fabric of Fine-grained Soil
Ch. 4 - Clay Minerals, Rock Classification Page 24 Flocculated and Dispersed Fabric Marine Clay Flocculated Fresh water Clay Dispersed
Ch. 4 - Clay Minerals, Rock Classification Page 25 Fabric of Granular Soils
Ch. 4 - Clay Minerals, Rock Classification Page 26 Particle Assemblages Schematic representations of particle assemblages: (a), (b), and (c) connectors; (d) irregular aggregations linked by connector assemblages; (e) irregular aggregations forming a honeycomb arrangement; (f) regular aggregations interacting with silt or sand grains; (g) regular aggregation interacting with particle matrix; (h) interweaving bunches of clay; (i) interweaving bunches of clay with silt inclusions; (j) clay particle matrix; (k) granular particle matrix (after Collins and McGown, 1974).
Ch. 4 - Clay Minerals, Rock Classification Page 27 Description of Structure of Fine-grained Soils/Rock Homogeneous - Same color and appearance throughout Stratified - Alternating layers of varying materials or color layers > 6 mm Laminated - Alternating layers of varying material or color with layers < 6 mm Banded - Layers of same material but with different colors
Ch. 4 - Clay Minerals, Rock Classification Page 28 Description of Structure of Fine-grained Soils/Rock (cont.) Fissured - Breaks along definite planes of fracture with little resistance to fracturing Slickensided - Fracture planes appear polished or glossy, sometimes striated Blocky - Cohesive soil than can be broke down into small angular lumps that resist further breakdown Lensed or seamed - Inclusion of small pockets of different soils
Ch. 4 - Clay Minerals, Rock Classification Page 29 Description of Structure of Fine-grained Soils/Rock (cont.) Mottled - Contains color blotches Honeycombed - Porous or vesicular Root holes - Presence of holes made by roots
Ch. 4 - Clay Minerals, Rock Classification Page 30 Rock Types 1 Igneous 2 Sedimentary 3 Metamorphic Pasted from <http://en.wikipedia.org/wiki/list_of_rock_types> Igneous rocks Extrusive or Volcanic Intrusive or Plutonic Sedimentary rocks Precipitates Clastic Biological Metamorphic rocks Nonfoliated Foliated
Ch. 4 - Clay Minerals, Rock Classification Page 31 Rock Structure Joints Fault Fissure
Ch. 4 - Clay Minerals, Rock Classification Page 32 Rock Structure (cont.) Fold
Ch. 4 - Clay Minerals, Rock Classification Page 33 Residual Soil and Weathered Rock
Ch. 4 - Clay Minerals, Rock Classification Page 34 Description and Classification of Rock Masses 1. 2. 3. 4. 5. Rock material a. Type b. Compressive Strength c. Degree of Weathering Discontinuities a. Type (fault, joint, bedding, foliation, cleavage, schistosity) b. Orientation (dip angle and direction) c. Roughness (e.g., smooth, slickensided, stepped, undulating, etc.) d. Aperture width Nature of infilling (type/width) a. Mineralogy, particle size, water content, hydraulic conductivity, fracturing, etc.) Rock mass description (e.g., massive, blocky, tabular, columnar, crushed, etc.) a. Joint spacing (close, moderate, wide, etc.) i. Extremely wide (> 6 m) ii. Very wide (2-6 m) iii. Wide (0.6-2 m) iv. Moderate (0.2-0.6 m) v. Close (0.06-0.2 m) vi. Very close (0.02-0.06 m) vii. Extremely close (<0.02 m) b. Persistence (areal extent or size within a plane area) c. Number of joint sets d. Block size and shape (small to large) Groundwater (seepage of water from joints or rock mass)
Ch. 4 - Clay Minerals, Rock Classification Page 35 Strength of Rock
Ch. 4 - Clay Minerals, Rock Classification Page 36 Rock Quality The rock quality designation (RQD): Quantifies the degree of fracturing and alteration in the original rock mass Obtained from rock coring Expressed as a percentage Developed by Deere (1963) ASTM (2010) D 6032 Care should be taken to distinguish between natural discontinuities and those cause by the drilling process. Rock core box from Cumberland, Rhode Island showing degree of weathering and fracturing. Double Core Barrel Sampler
Ch. 4 - Clay Minerals, Rock Classification Page 37 Rock Quality (cont.) RQD (%) Rock Quality 90-100 Excellent 75-90 Good 50-75 Fair 25-50 Poor 0-25 Very Poor
Ch. 4 - Clay Minerals, Rock Classification Page 38 Blank Friday, January 04, 2013 11:43 AM Steven F. Bartlett, 2013