Lecture 2 - Factual and Interpretive Reporting
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What does BS5930: 1999 indicate?
Basic principles of how rocks should be described Particular order
What three decisions must be made for soil descriptions? (NOTE: Opposite from order or words)
Principal soil type Secondary and minor fractions Other features
How do you distinguish silt from clay using the dry strength technique?
Roll a moistened sample into a thread/ribbon Air dry Crumble SILT will crumble easily, CLAY will not
How do you distinguish silt from clay using the dilatancy technique?
Place sample in one hand, palm up Add water to form a putty With empty hand, pat sample hand for 5-10 secs If water rises to surface = SILT
what two types of laboratory tests are undertaken and what do they test for?
Geotechnical - classification, shear/compressive strength Environmental - sulphate, pH, metals
How is moisture content worked out? What happens to sample before test?
Sample dried in oven p=(W-D)/D p = fraction of total evaporable moisture content of sample, W = mass of original sample, D = mass of dried sample
How is particle size distribution carried out?
Sieve analysis
What are Atterberg limits?
Depending on water content, soil is solid, semi-solid, plastic or liquid
What is meant by plastic and liquid limit?
Plastic limit = where soil becomes plastic Liquid Limit = where soil becomes liquid
What is the plasticity index? How is it worked out?
Measure of plasticity Its difference between Liquid limit and Plastic limit
Give an example of a chemical classification?
pH
How is the California bearing ratio calculated? What does it measure?
Measures compaction Pressure to penetrate soil sample with standard plunger, divided by pressure to penetrate a standard crushed rock
How is shear strength calculated?
Unconfined compressive strength
How does uniaxial shearing occur? What does it measure?
Soil sample cylinder compressed between two plates Measures maximum load at failure
How is shear strength of soil tested under controlled drainage conditions?
Triaxial test
During a triaxial test what is the specimen subjected to?
Confining fluid/air pressure Loaded axially to failure
Why is it called triaxial test?
3 principal stresses known and controlled
What is major principal stress (o1) the sum of?
Applied axial stress (^o = P/A) + chamber (confining) pressure (o3)
What is the intermediate and minor principal stresses? How are they similar?
o2 and o3 They have identical values
How are soil, groundwater and soil leachate collected for chemical testing?
Soil - disturbed samples Groundwater - directly collected Soil leachate - subject to leaching in lab