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SURVEY/INVESTIGATION/SOIL EXPLORATION FOR BUILDING WORKS,DPR FOR LARGE AND HIGH RISE BUILDINGS

Soil Exploration_By Er. P.K. Gouda

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Page 1: Soil Exploration_By Er. P.K. Gouda

SURVEY/INVESTIGATION/SOIL EXPLORATION FOR BUILDING

WORKS,DPR FOR LARGE AND HIGH RISE BUILDINGS

Page 2: Soil Exploration_By Er. P.K. Gouda

Detailed Project Report:Detailed project report is a complete document for investment decision-making, approval, planning whereas feasibility study report is a base document for investment decision-making. Detailed project report is base document for planning the project and implementing the project. Preparation of detailed project report is a step in firming up the proposal. When an investment proposal has been approved on the basis of functional report and the proposal is a major proposal, it would be necessary for detailed project report to firm up the proposal for the capital cost as well as the various facilities. It includes:– Examination of technological parameters.– Description of the technology to be used.– Broad technical specification.– Evaluation of the existing resources.– Schedule plan.– General layout.– Volume of work.

Page 3: Soil Exploration_By Er. P.K. Gouda

Detailed Project Report: (contd…) Detailed project report is prepared only for the investment decision-making approval, but also execution of the project and also preparation of the plan. Detailed project report additionally includes contents of Feasibility study reports:– Project description.– Planning and implementation of the project.– Specifications.– Layouts and flow diagrams.

Page 4: Soil Exploration_By Er. P.K. Gouda

Building Project Management:-

a. Project identification and preparation of feasibility studies.b. Statutory clearance (Administrative approval of the project, technical

sanction to the estimates, Site selection etc.) and tying up of project finance.

c. Engineering, procurement and construction including planning, organizing, monitoring and control.

d. Start-up and commissioning.

Page 5: Soil Exploration_By Er. P.K. Gouda

Carrying out of building (National building code of India-2005):-

Key plan:-Key plan drawn to a scale not less than 1:10000 showing the boundary rotations of the site with respect to neighborhood land marks.

Site plan:-Site plan shall be drawn to a scale not less than 1:500 for a site up to 1 hector and not less than 1:1000 for a site more than 1 hector. And shall show:Boundaries of the site Position of site in relation to the neighboring street Name of the street All existing buildings standing on Position of the building The direction of north point Any physical feature etc.

Building plan:-The plan of the buildings and elevations and sections drawn to a scale of 1:100

Page 6: Soil Exploration_By Er. P.K. Gouda

SITE INVESTIGATION1. First stage of site investigation:-

Aerial Photography. Topographical maps. Existing site investigation reports (for near by sites).

2. Site reconnaissance (Preliminary Survey):- Site Access. Topography. Site Geology. Condition of adjacent structure.

3. The field and lab investigations required to obtain necessary data for the soils for proper design and successful construction of any structure at the site are collectively called as soil exploration.

4. The choice of the foundation and its depth, the bearing capacity, settlement analysis depends very much upon the various engineering properties of the foundation soil.

Page 7: Soil Exploration_By Er. P.K. Gouda

Foundation:-

All engineered construction resting on the earth must be carried by a foundation. The foundation is the part of an engineered system which transmits to, and into, the underlying soil or rock the load supported by the foundation and its self weight. The resulting soil stresses except at the ground surface are in addition to those presently existing in the earth mass from the material self weight and geological history.

Superstructure:- System bringing load to the foundation on sub-structure.

• Interfacing the load carrying components to the ground.

Page 8: Soil Exploration_By Er. P.K. Gouda

Foundation (Contd.)

The supporting capacity of the soil either from strength and deformation consideration is seldom over 1000kPa. but more often on the order of 200KPa to 250KPa.But the load carrying columns exhibit the compressive stresses on the order of 10+Mpa.This means the foundation is interfacing two materials with a strength ratio on the order of several hundreds.

As a consequence the loads must be spread to the soil in a manner such that its limiting strength is not exceeded and resulting deformations are tolerable.

Page 9: Soil Exploration_By Er. P.K. Gouda

Primary objectives of soil exploration

• Determination of the nature of the deposit of the soil.• Determination of the depth and thickness of the various soil

strata and their extent in the horizontal direction.• The location of the G.W.T.• Obtaining soil and rock sample from various strata.• Determination of engineering properties of soil and rock strata

that affect the performance of the structure.• Determination of the in-situ property by performing field tests.

Page 10: Soil Exploration_By Er. P.K. Gouda

• Soil profile-Layer thickness of soil identification.

• Strength parametersStress-Strain modulus, Shear modulus, Poisson’s

ratio, Angle of internal friction, Soil cohesion• Compression index• Gravimetric-volumetric data

Unit weight, Specific gravity, Void ratio, Porosity, Water content.• Permeability

Soil data required:-

Page 11: Soil Exploration_By Er. P.K. Gouda

Major Factors Affecting Engineering Properties of Soil

1. Natural cementation and aging2. Consolidation3. Mode of deposit formation4. Quality of clay5. Soil water

Page 12: Soil Exploration_By Er. P.K. Gouda

Method for soil exploration:-• Direct method - test pit (IS 4453:2009), trial pits or trenches.• Semi direct method – boring (IS 1892-1979).• Indirect method – Sounding, penetration test (IS 2131-1981).

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Laboratory Problems

1. Recovery of good samples2. Necessity of extrapolating the results3. Ability and motivation of laboratory personnel

Page 14: Soil Exploration_By Er. P.K. Gouda

Direct Method:-• Test pits or trenches are open type or accessible exploratory method.• Soils can be inspected in their natural condition.• Necessary soil samples may be obtained by sampling techniques and

used for finding strength and other engineering properties by appropriate laboratory tests.

• Test pits are considered suitable for small depths up to 3.0M., the cost increases rapidly with depth.

• For greater depth, lateral support or bracing of the excavation will be necessary.

• Type of material neither in the class of soil nor rocks but in the form of gravel boulder(IS-10042-1981):-open trial pits of size 5×5 mtr but not less than 2×2 mtr. Depth of exploration 4 to 6mtr.

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Semi direct method:-• Boring, making or drilling boreholes in to the ground with a view to

obtain soil or rock sample specified or known depth is called boring.• Methods of advancing bore holes

Page 16: Soil Exploration_By Er. P.K. Gouda

Auger Boring:-• Soil auger is a device that is used for advancing a bore hole in to the

ground.• Auger may be hand operated or power driven, the former is used for

relatively small depth (less than 6mtr Depth) while the latter is used for greater depth up to 60 /70 mtr in case of continuous flight auger.

• Soil auger is advanced by rotating it while pressing it into the soil.• As soon as auger gets filled with soil, it is taken out and the soil is

collected.• Soil obtained from this type of borings are highly disturbed.• Augur boring is convenient in case of partially saturated sand silts and

medium to stiff cohesive soil.

Page 17: Soil Exploration_By Er. P.K. Gouda

Shell and auger boring:-

A Hand Rig used for vertical boring up to 200mm in dia and 25meter in depth and in Alluvial deposits the depth of bore hole may be extended up to 50 m with a mechanized rig.– Used widely.– Shell (called a sand bailer) is a heavy duty pipe with a cutting edge.– Shell is raised and let fall in a hole, soil is cut, enters the tube which is

emptied when full.– Shell is used when augur boring is difficult.

Page 18: Soil Exploration_By Er. P.K. Gouda

Wash Boring:-(Used for exploration below G.W.T for which auger boring is unsuitable.)

• Can be used in all kinds of soils except those mixed with gravel boulder.

• A casing pipe is pushed in and driven with a drop weight.• A hollow drill bit is screwed to a hollow drill and connected to a rope

passing over a pulley and supported by a tripod.• Water jet under pressure is forced through the rod and the bit in to

the hole. This loosens the soil at the lower end and forces the soil water suspension up ward along with annular surfaces between the rod and the side of the hole.

• This suspension is led to a settling tank where the soil particle settle down while the water over flows into a sump. The water collected by the sump is circulated again.

Page 19: Soil Exploration_By Er. P.K. Gouda
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Rotary boring:-• Primarily intended for investigation in rock,

but also used in soils.• The drilling tool, (cutting bit or a coring bit) is

attached to the lower end of hollow drilling rods

• The coring bit is fixed to the lower end of a core

• Water or drilling fluid is pumped down the hollow rods and passes under pressure through narrow holes in the bit or barrel

• The 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.

• The fluid (bentonite slurry) also provides some support to the sides of the hole if no casing is used.

• There are two forms of rotary drilling, open-hole drilling and core drilling.

Page 21: Soil Exploration_By Er. P.K. Gouda

• Open- hole drilling: which is generally used in soils and weak rock, just for advancing the hole

The drilling rods can then be removed to allow tube samples to be taken or in-situ tests to be carried out.

• In core drilling: which is used in rocks and hard clays, the diamond or tungsten carbide bit cuts an annular hole in the material and an intact core enters the barrel, to be removed as a sample. Typical core diameters are 41, 54 and 76mm, but can range up to 165 mm.

Advantages

The advantage of rotary drilling in soils is that progress is much faster than with other investigation methods and disturbance of the soil below the borehole is slight.

Page 22: Soil Exploration_By Er. P.K. Gouda

Percussion boring:-

• This is suitable for drilling boreholes in boulderous and gravely strata.

• The formation is broken up by repeated blows from a bit or chisels.

• Water is added to the hole at the time of boring and the debris baled out at intervals.

• A sampler can be driven into the bore, core may be obtained at intervals.

• In soils , the material may get disturbed compared to the sample obtained from the shell and auger method.

Page 23: Soil Exploration_By Er. P.K. Gouda

Depth of Exploration ( I.S. 1892-1979)• Depth of bore hole depends on the type of proposed structure, height,

size, shape and disposition of loaded area, soil profile and the physical properties of soil.

• Normally it should be one and half times the width of the footing below the foundation level.

• In weak soil, depth is considered at which the loads can be carried by the stratum in question without undesirable settlement and shear failure.

No of Boreholes, Spacing & Depth( I.S. 1892-1979)• To reveal any major change in thickness, depth or property of strata• Compact building site covering an area of 0.4ha, one borehole in each

corner and one in the centre.• For smaller and less important building one borehole will be sufficient.• Geological textures are considered in deciding number of bore holes.

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Types of soil sampling:-

Soils classified of following two types• Disturbed• Undisturbed• A disturbed sample is that in which this natural structure of the soil

gets modified partly or wholly during sampling.• An undisturbed sample is that in which the natural structure and their

physical properties remain present.

Page 26: Soil Exploration_By Er. P.K. Gouda

Nature of ground

Type of sample Method of sampling

Soil Disturbed Hand samplesAuger samples (for example, in clays)Shell samples (for example, in sands)

Undisturbed Chunk samplesTube samples

Rock Disturbed Wash samples from percussion or rotary drilling

Undisturbed Cores

Page 27: Soil Exploration_By Er. P.K. Gouda

Disturbed but representative samples can generally be used for-• Grain size analysis• Determination of Atterberg’s limits• Specific gravity of soil• Water content• Soil classification

Undisturbed samples must be used to • Consolidation test• Shear strength test

Page 28: Soil Exploration_By Er. P.K. Gouda

Types of samplers(IS:2131-1981)Soil samplers are classified as • Thick wall samplers (split spoon samplers)• Thin wall samplers (open tube)• Piston sampler

Sampling tools:-• Cutting edge• Non-return valve

Area ratio:-The value should be preferred of 10% for sensitive case to obtain undisturbed sample. Higher the area ratio, greater the disturbance.

Page 29: Soil Exploration_By Er. P.K. Gouda

Importance of Ground Water Table (GWT) :-

• A correct indication of G.W.T. is found by allowing the ratio in the boring to reach an equilibrium level.

• In sandy soil, the level gets stabilized very quickly with in few hours at most.

• In clayey soil, it will take several days. Stand pipe or piezometers are used to detect the location of Ground Water Tables.

Page 30: Soil Exploration_By Er. P.K. Gouda

INDIRECT METHOD:-

Standard penetration Test (SPT)• The SPT is widely used to determine the parameters of the soil in-situ. The

test consists of driving a split spoon sampler into the soil through a bore hole at the desired depth.

• The split spoon sampler is driven into the soil a distance of 450mm at the bottom of the boring.

• A hammer of 63.5kg weight with a free fall of 750mm is used to drive the sampler.

• Number of blows for a penetration of last 300mm is designated as the “Standard penetration value” or “number N”.

• The test is usually performed in three stages. Blow count is followed to every 150mm penetration.

• The blows for the first 150mm is ignored and this has been treated as seating drive.

Page 31: Soil Exploration_By Er. P.K. Gouda

Standard penetration Test (SPT) (Contd.)The refusal of the test when :• 50 blows are required for any 150mm increment.• 100 blows are obtained for required 300mm penetration.• 10 successive blows produce no advance.Corrections:-• Due to overburden • Due to DilatancyCo-relations:-• The angle of internal friction Ø and N may be rent from the chart (IS:6403-

1981). The SBC of the soil can be derived adopting method described in IS:6403-1981.

• The allowable bearing capacity can also be obtained from the settlement considerations using N value (IS 8009-1976 ).The net soil pressure that can be imposed on the base without the settlement specified not exceeding the limits specified in IS-1904-1986 .

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THANKS