Upload
dissasekara
View
238
Download
1
Embed Size (px)
Citation preview
8/13/2019 Soil & Site Investigation
1/21
constructionsite
Soil & Site Investigation
Ron Gatepain
8/13/2019 Soil & Site Investigation
2/21
constructionsite
Objectives of a Site Investigation
According to BS 5930, a site investigation iscarried out to:
Assess the general suitability of the site forthe proposed works
Enable an adequate and economic design
to be prepared
8/13/2019 Soil & Site Investigation
3/21
constructionsite
Foresee and provide against difficulties thatmay arise during construction due to groundand other local conditions
Predict any adverse effect of the proposedconstruction on neighbouring structures.
8/13/2019 Soil & Site Investigation
4/21
constructionsite
Preliminary Site Investigation
Mining authorities - existing and future factorseffecting ground movement.
Ordinance Survey - land contours, rights ofway, rivers, existing buildings. (Look at oldmaps - pond in wrong place)
Geological Central Record.
8/13/2019 Soil & Site Investigation
5/21
constructionsite
Met Office - frost hollows, prevailing windsand severity, rain fall.
Water Authorities - water tables, flood planes. Planning and Building Control. (tree
preservation orders) Utilities - gas, water, electricity, British
Telecom, sewage. Listed and historical buildings.
8/13/2019 Soil & Site Investigation
6/21
constructionsite
Information obtained from the LocalAuthority
The likely site conditions. Possible subsidence due to ground movement
or underground workings. Previous land use and buildings on the site. Problems likely to be encountered with regard
to water tables and flooding.
8/13/2019 Soil & Site Investigation
7/21
constructionsite
Site Exploration
The aim is to provide a survey of the subsoil inorder to find out the nature and disposition of
the soil below ground level, and to obtainsamples of the soil for testing in thelaboratory
The exploration should be done at the sametime as the preliminary design of the building;this prevents obtaining insufficient or
unwanted data.
8/13/2019 Soil & Site Investigation
8/21
constructionsite
The extent of the exploration will depend onthe size and type of structure, the nature of
the site, and the availability of local geologicalinformation. The exploration should be taken deep enough
to include all strata likely to be significantlyaffected by the loading of the building. Thisdepth will depend on the weight, size andshape of the loaded areas.
8/13/2019 Soil & Site Investigation
9/21
constructionsite
Methods of Sub Surface Investigations
Trial Pits Plate Bearing Test
Borings Headings Penetration Test Sounding Test Vane Test
8/13/2019 Soil & Site Investigation
10/21
constructionsite
Plate Bearing Test
Stress = Load use a safetyArea factor of 2
Plate is loaded and themovement measured
8/13/2019 Soil & Site Investigation
11/21
constructionsite
Borings
Hand Boring - depths up to 6 to 9m auger isusually 100 - 150mm in diameter
Mechanical Boring Borehole Log
8/13/2019 Soil & Site Investigation
12/21
constructionsite
Soil Samples
Disturbed brings out the soil particles butdoes not keep them in their original position
Undisturbed brings out the core of soil as itis in the ground
8/13/2019 Soil & Site Investigation
13/21
8/13/2019 Soil & Site Investigation
14/21
constructionsite
Sounding Test
The devise is driveninto the ground andthe pressure recorded
8/13/2019 Soil & Site Investigation
15/21
constructionsite
Vane Test
The vane is twisted
in the ground andthe torquemeasured whichcauses the groundto shear
8/13/2019 Soil & Site Investigation
16/21
constructionsite
Classification by Grain Size
(BS 1377:1967) Clay : particles smaller than 0.002mm Silt : particles between 0.002 - 0.06mm Sand : particles between 0.06 - 2mm Gravel: particles between 2 - 60mm Boulders: particles above 60mm
8/13/2019 Soil & Site Investigation
17/21
constructionsite
Basic Subsoil Classifications
Rock - a very wide strength range. Cohesive Soil - clay and silt . Non-cohesive Soil - sand and gravel. Made up Ground - unsuitable until
consolidated. Peat - unsuitable because it is organic and will
therefore decompose.
8/13/2019 Soil & Site Investigation
18/21
constructionsite
The objectives of a ground investigation To assess the general suitability of the site for
the proposed works. To enable an adequate and economic design to
be prepared. To foresee and provide against difficulties that
may arise during construction due to ground
conditions. To investigate the occurrences or causes of allnatural or created changes of conditions andtheir results.
8/13/2019 Soil & Site Investigation
19/21
constructionsite
Laboratory Tests
Soil Classification. Consolidation Tests. These enable time/settlement
graphs to be drawn so that the rate of settlement andits total final amount can be forecast.
Shear Strength Tests. An important group of tests asthey indicate the load carrying capabilities of the soils.
They are particularly significant in the case of plasticclays as, in these, shear strength is constant at a givenmoisture content: thus, if shear strength is exceeded,failure is likely.
8/13/2019 Soil & Site Investigation
20/21
constructionsite
Chemical Analysis. This will indicate the presence ofharmful compounds in the subsoil/ground water: thesecompounds will usually be sulphates or acids. If
present they will affect the choice of materials and/ormethods; e.g. sulphate resisting or blast furnacecement in foundation concrete; use of separatingmembrane; use of non-metallic pipes in acid soils.
Moisture Content Tests. Done as part of theclassification test, but also needed to forecast likelyvolume changes when building on shrinkable/swellingclays.
8/13/2019 Soil & Site Investigation
21/21
constructionsite
Other Tests
Atterburg Limits Mohr's Circles
Bulbs of Pressure