Lecture 2 - Geotechnical Engineering
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What should be worn when dealing with contaminated soil?
Personal protective equipment (PPE)
How is degree of contamination measured? What two tests can be done? Why are they done?
Mean as not uniform contamination Mean value test - identify 95% confidence levels of measured mean Maximum value test - tests whether max value in sample set is outlier
What is a common soil problem? What can be done?
Leactate Can be diluted to acceptable levels
How is the dilution factor calculated?
Dilution factor = Qc + (Qu/Qc) Where Qu = water flow in surface water receptor Qc = contaminated groundwater flow from site
Name two remediation methods?
Removal of soil to landfill Bioremediation
How are bearing capacities of soil calculated?
SPT Triaxial tests
What kind of foundations are usually used?
Shallow foundations or piles
What can happen during void collapse if mineral stability is poor?
Void can be filled by equal volume of overlying rock (Rare due to bulking) Usually void void migrates upward through strata until process no longer supported when collapse is absorbed
What is the minimum cover rule in terms of void collapse?
Rock cover above seam : 5-10 times seam thickness required
What can be done to assist mineral stability?
Grouting
How can potential slope failures be addressed?
Input of concrete
What are the three different types of shallow foundations?
Strip foundations, pile foundations or raft foundations
Describe strip shallow foundations?
Narrow (width >1m still) Concrete footing Typically support walls
Describe pad shallow foundations
Support columns , various types
Describe raft/slab shallow foundations, why are they used?
Reinforced steel grid, pumped concrete Spreads load, used for soft/loose soils
What characterise deep foundations?
Piling (different types and methods)
When would end bearing piles be used and when would friction piles be used?
End bearing - soft compressible soil on top of hard incompressible layer Friction - soft soil gradually stiffening with depth
Describe displacement piles
Soft displaced radially and vertically. Concrete, steel or combination Typically drive
How are driven piles made?
Drive steel tube into ground to form void Void filled with concrete as tube removed
How are non-displacement piles made?
Soil removed using massive rotary rig, Filled with concrete Pre-cast piles
When are non-displacement piles useful?
Boulder clay and made ground
What is meant by the term ‘bearing capacity’?
Capacity of soil to support loads applied to ground
What is the ultimate bearing capacity?
Theoretical max. pressure without failure
What is the allowable bearing capacity?
Maximum pressure which may be applied to soil Adequate FOS against shear failure is ensured Settlement should not cause damage to structure