Soil exploration/Investigation method, purpose depth of exploration (Usefulsearch.org) (useful search)
- 2. 22 IndexIndex Purpose of Soil ExplorationPurpose of Soil Exploration Different methodsDifferent methods 1.1. Test trenches and PitsTest trenches and Pits 2.2. Auger and Wash BoringAuger and Wash Boring 3.3. Rotary DrillingRotary Drilling 4.4. Geophysical MethodsGeophysical Methods
- 3. How do weHow do we Explorate Soil...?Explorate Soil...? 33
- 4. 44 COMMON STAGES IN SITE INVESTIGATIONCOMMON STAGES IN SITE INVESTIGATION Desk StudyDesk Study Site ReconnaissanceSite Reconnaissance Field InvestigationsField Investigations a) Preliminary Ground Investigationa) Preliminary Ground Investigation b) Detailed Ground Investigationb) Detailed Ground Investigation Laboratory TestingLaboratory Testing Report WritingReport Writing Follow up Investigations during design &Follow up Investigations during design & constructionconstruction Appraisal of performanceAppraisal of performance
- 5. 55 SOIL INVESTIGATIONSOIL INVESTIGATION Determination of surface and subsurface soilDetermination of surface and subsurface soil conditions and features in an area of proposedconditions and features in an area of proposed construction that may influence the design andconstruction that may influence the design and construction and address expected postconstruction and address expected post construction problems.construction problems. SCOPE OF INVESTIGATION Simple visual examination of soil at the surface or from shallow test pits. Detailed study of soil and groundwater to a reasonable depth (influence zone) by sampling from bore holes, shafts and audits and in-situ and laboratory tests.
- 6. 66 PURPOSE OF SOIL INVESTIGATION:PURPOSE OF SOIL INVESTIGATION: The site investigation provides first hand information for; Selection & Design of foundations type. Planning construction techniques. Selection of appropriate construction equipment (especially for excavation and foundations). Estimating development cost for the site. Study of environmental impacts of the proposed construction.
- 7. 77 7 Need for any suitable soil improvements.Need for any suitable soil improvements. Requirement of any surface or subsurfaceRequirement of any surface or subsurface drainage.drainage. Selection of the most suitable and economicalSelection of the most suitable and economical route for highways with respect to soilroute for highways with respect to soil conditions.conditions. The design of extension works to existingThe design of extension works to existing structures.structures. the investigation of the cases where failure hasthe investigation of the cases where failure has occurred, to know the causes and design ofoccurred, to know the causes and design of PURPOSE OF SOIL INVESTIGATION(B):PURPOSE OF SOIL INVESTIGATION(B):
- 8. DEPTH OF EXPLORATIONDEPTH OF EXPLORATION Depth of exploration at particular site dependsDepth of exploration at particular site depends upon degree of variation of subsurface data inupon degree of variation of subsurface data in horizontal and vertical direction.horizontal and vertical direction. For square footing 1.5B=D.For square footing 1.5B=D. For strip footing 3B=D.For strip footing 3B=D. For pile foundation D=1.5 times the width of theFor pile foundation D=1.5 times the width of the pile group.pile group. In case of friction pile D=1.5 times the width ofIn case of friction pile D=1.5 times the width of the pile group measured from lower 3the pile group measured from lower 3rdrd point.point. 88
- 9. In case of multistory buildings D= C(S)In case of multistory buildings D= C(S).7.7 Here D= depth of exploration, C=constantHere D= depth of exploration, C=constant equal to 3 for light steel buildings & naarrowequal to 3 for light steel buildings & naarrow concrete buildings. It is equalto 6 for heavyconcrete buildings. It is equalto 6 for heavy steel buildings & wide concrete building,S=steel buildings & wide concrete building,S= number of stories.number of stories. In case of road fill mini Depth of boring=2mIn case of road fill mini Depth of boring=2m below ground surface or = to the height of thebelow ground surface or = to the height of the fill,whichever is more.fill,whichever is more. In case of gravity dam mini Depth of boring isIn case of gravity dam mini Depth of boring is twice the height of the dam.twice the height of the dam. 99
- 10. LATERAL EXTENT OF EXPLORATIONLATERAL EXTENT OF EXPLORATION Lateral extent of exploration and spacing of boreLateral extent of exploration and spacing of bore holes depends on horizontal variation of theholes depends on horizontal variation of the strata.strata. For small and less imp building one bore hole orFor small and less imp building one bore hole or a trial pit may sufficient. but for compacta trial pit may sufficient. but for compact buildungs covering an area about 0.4 hect,therebuildungs covering an area about 0.4 hect,there should be 5 bore holes one at centre & 4 nearshould be 5 bore holes one at centre & 4 near the corner,(Spacing of bore hole=10m-30m).the corner,(Spacing of bore hole=10m-30m). For highways exploration carried out along theFor highways exploration carried out along the centre line,(Spacing of bore hole=150m-centre line,(Spacing of bore hole=150m- 300m).if the substrata is erractic spacing may be300m).if the substrata is erractic spacing may be reduced upto =30m.reduced upto =30m. 1010
- 11. 1111 Boring Logs
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- 13. 1313 METHODS OF INVESTIGATIONMETHODS OF INVESTIGATION
- 14. 1414 METHODS OF INVESTIGATIONMETHODS OF INVESTIGATION The methods to determine the sequence, thickness andThe methods to determine the sequence, thickness and lateral extent of the soil strata and, where appropriatelateral extent of the soil strata and, where appropriate the level of bedrock.the level of bedrock. The common methods includeThe common methods include Test pitsTest pits Shafts and auditsShafts and audits Boring or drillingBoring or drilling
- 15. 1515 Test PitsTest Pits The excavation of test pits is a simple and reliableThe excavation of test pits is a simple and reliable method.method. The depth is limited to 4-5m only.The depth is limited to 4-5m only. The in-situ conditions are examined visuallyThe in-situ conditions are examined visually It is easy to obtain disturbed and undisturbed samplesIt is easy to obtain disturbed and undisturbed samples Block samples can be cut by hand tools and tubeBlock samples can be cut by hand tools and tube samples can be taken from the bottom of the pit.samples can be taken from the bottom of the pit.
- 16. 1616 16 1 2 3 4 Walls of the test pit indicate four layers (1) Clayey silt (2) Sandy silt (3) Clean sand (4) Sandy gravel
- 17. 1717 Boring or DrillingBoring or Drilling Boring refers to advancing a hole in the ground.Boring refers to advancing a hole in the ground. • Boring is required for the following:Boring is required for the following: • To obtain representative soil and rock samples for laboratory tests.To obtain representative soil and rock samples for laboratory tests. • To identify the groundwater conditions.To identify the groundwater conditions. • Performance of in-situ tests to assess appropriate soil characteristics.Performance of in-situ tests to assess appropriate soil characteristics. • Some of the common types of boring are as followsSome of the common types of boring are as follows •Auger boringAuger boring
- 18. 1818 18 Auger BoringAuger Boring Hand AugerHand Auger It is the simplest method of boring used for small projects in soft cohesive soils.It is the simplest method of boring used for small projects in soft cohesive soils. For hard soil and soil containing gravels boring with hand auger becomesFor hard soil and soil containing gravels boring with hand auger becomes difficult.difficult. Hand-augered holes can be made upto about 20m depth, although depthHand-augered holes can be made upto about 20m depth, although depth greater than about 8-10m is usually not practical.greater than about 8-10m is usually not practical. The length of the auger blade varies from 0.3-0.5m.The length of the auger blade varies from 0.3-0.5m. The auger is rotated until it is full of soil, then it is withdrawn to remove theThe auger is rotated until it is full of soil, then it is withdrawn to remove the soil and the soil type present at various depths is noted.soil and the soil type present at various depths is noted. Repeated with drawl of auger for soil removal makes boring difficult below 8-Repeated with drawl of auger for soil removal makes boring difficult below 8- 10m depth.10m depth. The soil samples collected in this manner are disturbed samples and can beThe soil samples collected in this manner are disturbed samples and can be used for classification test. Auger boring may not be possible in very soft clayused for classification test. Auger boring may not be possible in very soft clay or coarse sand because the hole tends to collapse when auger is removedor coarse sand because the hole tends to collapse when auger is removed Hand Auger Mechanical Auger
- 19. 1919 a.-Helical (worm types) Augera.-Helical (worm types) Auger b. Short flight Augerb. Short flight Auger c. Iwan (posthole) Augerc. Iwan (posthole) Auger a b c
- 20. 2020 Mechanical AugerMechanical Auger o Mechanical Auger means power operated augers. The power required toMechanical Auger means power operated augers. The power required to rotate the auger depends on the type and size of auger and the type of soil.rotate the auger depends on the type and size of auger and the type of soil. o Downwards pressure can be applied hydraulically, mechanically or by deadDownwards pressure can be applied hydraulically, mechanically or by dead weightweight a a b c d a. Continuous Flight Auger b. Hallow-stem auger plugged during advancing bore c. Plug removed and sampler inserted d. Truck mounted auger boring machine
- 21. 2121 21 The diameter of the flight auger usually is between 75 toThe diameter of the flight auger usually is between 75 to 300mm, although diameters up to 1m and bucket augers up300mm, although diameters up to 1m and bucket augers up to2m are available.to2m are available. Borehole depths up to 50m are possible with continuous-flightBorehole depths up to 50m are possible with continuous-flight augers.augers. Continuous flight augers can be solid stem or hollow stemContinuous flight augers can be solid stem or hollow stem with internal diameter of 75-150mm.with internal diameter of 75-150mm. Hollow stem augers are used when undisturbed samples areHollow stem augers are used when undisturbed samples are required.required. As the auger acts as a casing it can be used in sand belowAs the auger acts as a casing it can be used in sand below water table. The possibility of rising sand in to the stem bywater table. The possibility of rising sand in to the stem by hydrostatic pressure can be avoided by filling the stem withhydrostatic pressure can be avoided by filling the stem with water up to the water table.water up to the water table.
- 22. 2222 The soil rises to the surface along the helical blades, obviatingThe soil rises to the surface along the helical blades, obviating the necessity of withdrawal.the necessity of withdrawal. They are not suitable for soil bore that require casing, whichThey are not suitable for soil bore that require casing, which demand removal of auger for driving the casing.demand removal of auger for driving the casing. The presence of cobbles and boulders create problems withThe presence of cobbles and boulders create problems with small-sized augers.small-sized augers. There is a possibility that different soil types may becomeThere is a possibility that different soil types may become mixed as they rise to the surface and it may be difficult tomixed as they rise to the surface and it may be difficult to determine the depths of changes of strata. Experienced drillerdetermine the depths of changes of strata. Experienced driller can however detect the change of strata by the change of speedcan however detect the change of strata by the change of speed and the sound of drilling.and the sound of drilling.
- 23. 2323 23 Wash boringWash boring Water with high pressure pumped through hallow boring rods isWater with high pressure pumped through hallow boring rods is released from narrow holes in a chisel attach to the lower end ofreleased from narrow holes in a chisel attach to the lower end of the rods.the rods. The soil is loosened and broken by the water jet and the up-The soil is loosened and broken by the water jet and the up- down moment of the chisel.down moment of the chisel. The soil particles are carried in suspension to the surfaceThe soil particles are carried in suspension to the surface between the rock and the borehole sites.between the rock and the borehole sites. The rods are raised and drop for chopping action of the chiselThe rods are raised and drop for chopping action of the chisel by means of winch.by means of winch. Wash boring can be used in most type of soil but the progress isWash boring can be used in most type of soil but the progress is slow in coarse gravel strata.slow in coarse gravel strata.
- 24. 2424 The accurate identification of soil strata is difficult due toThe accurate identification of soil strata is difficult due to mixing of the material has they are carried to the surface.mixing of the material has they are carried to the surface. The method is unacceptable for obtaining soil samples.The method is unacceptable for obtaining soil samples. It is only used for advancing the borehole to enable tubeIt is only used for advancing the borehole to enable tube sample to be taken or field test to be carried at the holesample to be taken or field test to be carried at the hole bottom.bottom. The advantage is that the soil immediately below the holeThe advantage is that the soil immediately below the hole remains relatively un-disturbedremains relatively un-disturbed
- 26. 2626 ROTARY DRILLINGROTARY DRILLING The rig consists of a derrick, power unit, winch, pump and a drillThe rig consists of a derrick, power unit, winch, pump and a drill head to apply high-speed rotary drive and downward thrust to thehead to apply high-speed rotary drive and downward thrust to the drilling rods.drilling rods. Primarily intended for investigation in rock, but also used in soils.Primarily intended for investigation in rock, but also used in soils. The drilling tool, (cutting bit or a coring bit) is attached to the lowerThe drilling tool, (cutting bit or a coring bit) is attached to the lower end of hollow drilling rodsend of hollow drilling rods The coring bit is fixed to the lower end of a coreThe coring bit is fixed to the lower end of a core Water or drilling fluid is pumped down the hollow rods and passesWater or drilling fluid is pumped down the hollow rods and passes under pressure through narrow holes in the bit or barrelunder pressure through narrow holes in the bit or barrel The drilling fluid cools and lubricates the drilling tool and carries theThe drilling fluid cools and lubricates the drilling tool and carries the loose debris to the surface between the rods and the side of the hole.loose debris to the surface between the rods and the side of the hole.
- 27. 2727 The fluid (bentonite slurry) also provides some support to theThe fluid (bentonite slurry) also provides some support to the sides of the hole if no casing is usedsides of the hole if no casing is used .. There are two forms of rotary drilling, open-hole drilling andThere are two forms of rotary drilling, open-hole drilling and core drilling.core drilling. Open- hole drilling, which is generally used in soils and weakOpen- hole drilling, which is generally used in soils and weak rock, just for advancing the holerock, just for advancing the hole The drilling rods can then be removed to allow tube samples toThe drilling rods can then be removed to allow tube samples to be taken orbe taken or in-situin-situ tests to be carried out.tests to be carried out. In core drilling, which is used in rocks and hard clays, theIn core drilling, which is used in rocks and hard clays, the diamond or tungsten carbide bit cuts an annular hole in thediamond or tungsten carbide bit cuts an annular hole in the material and an intact core enters the barrel, to be removed as amaterial and an intact core enters the barrel, to be removed as a sample. Typical core diameters are 41, 54 and 76mm, but cansample. Typical core diameters are 41, 54 and 76mm, but can range up to 165 mm.range up to 165 mm.
- 28. 2828 AdvantagesAdvantages The advantage of rotary drilling in soils is that progress isThe advantage of rotary drilling in soils is that progress is much faster than with other investigation methods andmuch faster than with other investigation methods and disturbance of the soil below the borehole is slightdisturbance of the soil below the borehole is slight.. LimitationsLimitations The method is not suitable if the soil contains a highThe method is not suitable if the soil contains a high percentage of gravel/cobbles, as they tend to rotate beneath thepercentage of gravel/cobbles, as they tend to rotate beneath the bit and are not broken up.bit and are not broken up. The natural water content of the material is liable to beThe natural water content of the material is liable to be increased due to contact with the drilling fluidincreased due to contact with the drilling fluid
- 30. 3030 GEOPHYSICAL METHODGEOPHYSICAL METHOD Although boring and test pits provide definite results but they are timeAlthough boring and test pits provide definite results but they are time consuming and expensive.consuming and expensive. Subsurface conditions are known only at the bore or test pit location.Subsurface conditions are known only at the bore or test pit location. Geophysical methods are more quick and cheaper.Geophysical methods are more quick and cheaper. They provide thorough coverage of the entire area.They provide thorough coverage of the entire area. The results of Geophysical testing require subjective interpretation.The results of Geophysical testing require subjective interpretation. Therefore both methods are important. In case geophysical testing in majorTherefore both methods are important. In case geophysical testing in major in scope, few borings and sampling will be required for accuratein scope, few borings and sampling will be required for accurate determination of soil properties.determination of soil properties. If boring is major in scope then few geophysical lines will be required to knowIf boring is major in scope then few geophysical lines will be required to know the conditions in-between the borings.the conditions in-between the borings.
- 31. 3131 31 Site Evaluation Direct MethodsSite Evaluation Direct Methods Boreholes/ProbesBoreholes/Probes TestTest Pits/TrenchesPits/Trenches CoresCores
- 32. 3232 Geophysical Techniques IndirectGeophysical Techniques Indirect MethodsMethods o Ground Penetrating Radar (GPR)Ground Penetrating Radar (GPR) o Electromagnetic (EM)Electromagnetic (EM) o MagneticMagnetic o Utility LocatingUtility Locating o SeismicSeismic o Electrical ResistivityElectrical Resistivity o GravityGravity o Very Low Frequency (VLF)Very Low Frequency (VLF)
- 33. 3333 33 Geophysical Techniques Indirect MethodsGeophysical Techniques Indirect Methods AdvantagesAdvantages Non-DestructiveNon-Destructive Cost EffectiveCost Effective ProvidesProvides Preliminary orPreliminary or SupplementalSupplemental InformationInformation