CIVIL ENGINEERING
Investigating the significance of geology in the construction of: dams and reservoirs;
tunnels and cuttings; buildings; sea defences.
Civil engineering work needs to take account of geological factors to avoid.

Problems of ground instability associated with dip of strata, folding, faulting, rock
cleavage and joint patterns.

Interference with hydrological systems, surface and underground drainage patterns
(porosity and permeability, water table, aquifers).

Interference with the coastal system: coastal erosion and longshore drift.
SOME ENGINEERING RESPONSES TO GEOLOGICAL CONDITIONS
The first row in this table has been completed for you as an example.
Geology
Stone fall (most rock faces produce falls of
small rocks as a result of weathering)
Soft ground and settlement
Weak ground and potential failure
Unstable slopes and potential sliding
Severe river or coastal erosion
Potential earthquake hazard
Potential volcanic hazard
Rock required as a resource
Response
Rock trap ditches at foot of slope.
Gabion walls to trap loose rocks.
Wire or rope rock catch nets on steep slopes.
Rock fall shelters to protect roads below.
ROCK STRENGTH
UCS This is the unconfined (or uniaxial) compressive strength: load to cause failure of a
cube of the material confined between two flat plates with no lateral restraint. This is
measured in MPa (Mega Pascals).
UCS is firstly influenced by the nature of the rock, for example, granite is 4000 times
stronger than peat, but fracturing, bedding, settlement and weathering etc also influence
the strength of a rock.
Strong Rocks
UCS over 100 MPa
Little fracturing
Minimal weathering
Stable foundations
Stand in steep faces
Aggregate resource
Weak Rocks
UCS less than 100 MPa
Fractured and bedded
Deep weathering
Settlement problems
Fail on low slopes
Require engineering care
An approximate succession in order of strength (of intact/ unweathered rock) is: granite,
limestone, sandstone, shale, clay, soil.
SBP is the safe bearing pressure of a rock, i.e. the load that may safely be imposed upon
in the ground.