1. BUILDINGS

2. Shallow Foundations rafts pads strips Raft Pads

3. Deep Foundations piles What type of foundations to build depends on: depth to rockhead depth to water table geological structures rock properties

4. Buildings So – the factors geologists assess before constructing a large structure should include: Jointing Dip of bedding Faults Cleavage Depth to water table Depth to rockhead Weathering Rock properties Radon gas concentrations

5. A B C Leaning Tower of Pisa Foundations Variable, soft, silty deposits - unconsolidated Very soft clays - consolidated Dense, consolidated sandstones Water table 10m 40m Clay deposits are prone to settlement under load Saturated sediments compress & subside under load Load causes water to be squeezed out Very weak sediment. Buildings need high foundation strength Depth to water table affects the stability of the foundation material by affecting the pore water pressure

6. soil bedrock rockhead Seismic Survey - Depth to rockhead ? Unconsolidated, porous & compressible Consolidated, rigid & less compressible Seismic waves speed = slow Seismic waves speed = fast

7. drift bedrock rockhead Seismic Survey - Depth to rockhead ? Seismic source Seismic recording stations

8. drift bedrock rockhead Seismic Survey - Depth to rockhead direct seismic wave refracted seismic wave ?

9. drift bedrock rockhead time distance form seismic source Arrival time of direct waves Arrival time of refracted waves Seismic Survey - Depth to rockhead

10. drift bedrock rockhead time distance form seismic source Arrival time of direct waves Arrival time of refracted waves Seismic Survey - Depth to rockhead Point of transformation 5km V2 = 5km/s V1 = 3km/s

11. Electrical Resistivity Survey - Depth to water table Transmitting electrodes Receiving electrodes Wenner array of 4 electrodes Speed of electrical transmission increases with increasing water content. Higher water table means reduced electrical resistivity.

12. Radon Gas Colourless Odourless Tasteless Radioactive gas GRANITE Radon Produced by radioactive decay of 238 Uranium in granite If concentrations build up it can cause lung cancer 10 – 15,000 deaths in USA & Canada every year

13. Radon Gas pathways HOUSE BASEMENT Joints & cracks in rocks Pore spaces in rocks & soils Pipes & other services Concentrations build up in unventilated rooms & spaces

14. Radon Gas RADON GAS