Site Investigations Flashcards
Topography
The surface features of an area
Greenfield
Sites which have not previously been built on
Brownfield
Sites which have been previously built on and may now be disused or derelict
Subsidence
The downward movement of the ground on the site that is not related to the weight of the building
Settlement
Consolidation or decrease in the volume of the soil due to the weight of the building
Conservation area
An area designated by the local planning authority as historical or for architectural interest
Greenbelts
Non-built areas around towns and cities to protect the environment and prevent urban sprawl
Sites of Special Scientific Interest (SSSI)
Sites protected by law to conserve wildlife or geology
Borehole report
Provides information on the soil types and depths within various strata underneath the surface of the site
External envelope
The walls and roof of forming the external surfaces of a building, including features such as the windows and external doors
Ground conditions
soil type, composition, contamination, level of compaction, water table level, level of saturation
Ground water table
The depth below ground level of water contained in the ground
Sub-soil
Soil below the topsoil
Bearing pressure
Pressure on soil caused by load
Bearing capacity
The amount of load the ground can carry
What is the difference between ground investigation and site investigation?
GI is concerned with the properties of the ground, whereas site investigation is to do with all aspects of the location
What is the significance of site investigation? Why? (2)
- To highlight unfavourable ground conditions or hazards (EG soft ground, contamination. 2. To obtain data that enables design team to build structures
What is the purpose behind completing a site investigation? (4)
- Saves money - gives u info to figure out if soil treatment necessary. 2. Provides background - to improve safety of project. 3. Reduces damages - buildings on bad soil’s foundations can be damaged in the future. 4. Assist in determining construction materials - identifies which materials should be used in construction
What are the risks of a potential site? (7)
- Nature and condition of the soil is unknown. 2. Bad SI could cause geotechnical and structural problems. 3. Brownfield sites may need to be sealed and ground decontaminated. 4. Site may be in a flood plain. 5. Potential earthquake or tremor region. 6. Ground water levels. 7. Misunderstandings, delays, and extra cost
Information required from a site investigation (7)
- Ground properties, 2. Topography of site, 3. Location of services, 4. Chemical constituents of soil, 5. evidence of contamination, 6. position of groundwater, 7. Position of any tree roots
Walk-Over Survey
Walking the site on foot, making notes on relevant things for the project. This allows experienced surveyors to get a feel of the ground condition.
sub-soil investigation, why?
To figure out soil type, consistency, structure, moisture conditions, presence of roots. From these we can find bearing capacity, seasonal changes and possible ground movements.
Window sampling (sub-soil investigation)
Boring (sticking a hollow tube through) shallow soft soils to investigate the substrata in order to gain a profile of the ground conditions and to facilitate soil sampling for chemical and geotechnical analysis
Trial pits
dug to 3-4m, sides of excavations inspected, soil samples tested, do sides collapse? does trench fill with water?
Bore Holes
Drilled down and sealed, can go 30m in depth, through soil, sand/gravel, water bearing strata
Pressure bulb
the area to which applied load can move soil through pressing down. If the downward pressure is too great compared to the bearing pressure of the soil, then settlement occurs.
What aspects of soil would you wanted tested in a lab? (6)
- Soil classification (consistency, particle size etc), 2. Shear strength (resistance to erosion, cohesiveness), 3. Internal friction (sand/large, clay/small) 4. Compressibility (squeezing out air/water) 5. Permeability (water travelling through voids) 6. Contamination (previous use/chemical makeup)
Solid Rock (soil type) (3)
Levelling difficulty, cavities would require filling, can be problematic to combine
Gravels (soil type) (3)
High bearing capacity, less risk of long term settlement, can be undermined by water flow/table
Sands (soil type) (4)
Smaller angular particles, good bearing capacity, classified into compact or loose, can be affected by water and frost
Silts (soil type) (4)
Fine particles, low bearing capacity, prone to shrinkage/swelling by water content, weak to frost
Clays (soil type) (4)
Microscopically small particles, stiff firm and soft, can change in volume massively from moisture content, can suffer very slow settlement
Peats (soil type) (1)
vegetable matter with no bearing capacity, formed from partially decomposed material under water saturated conditions.
Dead load
These are loads that are stationary and permanent
Live load
Temporary or movable loads that act on the structure as its being used (people, furniture)
Environmental loads
wind/snow/ground/vibration.
Cohesive soils
Clay, silt, peat - microscropic size of particles makes water cling to them. Can suffer very slow settlement. Contain large volumes of water, shrinkage and swelling, stable and good texture, generally stable at 1m depth
Non-cohesive soils
Gravel and sands. Much larger size and when loaded, shape makes them lock together, water drains out of them, high bearing capacity, frost can have a problem 600-750mm depth
Constraints to design/construction (5)
Planning constraints, statutory constraints (EG building regulations, CDM), environmental constraints (air,noise,water pollution), Social Constraints (Neighbours rights, community objections), budget constraints (local prices, life cycle costs
