Category Archives: Soil Mechanics

Analysis of Structure Building Materials Con Tech & RCC Design Soil Mechanics Solid & Liquid Waste Management Uncategorized

Collection of all IS codes used in Civil Engineering Field.

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The codes are arranged in ascending order of their number. Click the code number to open the PDF file.

SL NOIS CODE NODESCRIPTION
173Specification for paving Bitumen
2277Galvanised steel sheets (plain and corrugated)
3303Specification for Plywood for general purposes
4383Specification for Coarse and Fine aggregate for use in mass concrete
5432Specification for Mild steel and medium tensile bars and hard drawn steel wire.
6456Code of practice for plain and reinforced concrete
7457Code of practice for general construction of plain and reinforced concrete for dams and other massive structures.
8515Specification for natural and manufactured aggregate for use in mass concrete.
9516Methods of test for strength of concrete.
10650Specification for Standard sand for testing of Cement
11651Glazed stoneware pipes and fittings
12702Specification for industrial bitumen
13772Specific action for general requirements for enameled cast iron sanitary appliances.
14774Flushing cisterns for water closets and urinals (Other than plastic cistern)-Specifications.
151139Specification for hot rolled mild steel, medium tensile steel and high yield strength steel deformed bars for concrete reinforcement.
161199Methods of sampling and analysof concrete
171199Methods of sampling and analysof ConCrete
181300Phenolic moulding materials.- Specifications
191343Code of practice for prestressed concrete
201566Specification for plain hard drawn steel wire fabric for concrete reinforcement
211629Rules for grading of cut size of timber
221703Water fittings- Copper alloy float valves (horizontal plunger type) – Specification.
231729Cast iron Drain water pipes and fitting
241785Specification for plain hard drawn steel wire for prestressed concrete.
251786Specification for cold twisted steel high strength deformed bars for concrete reinforcement.
261791Specification for batch type concrete mixers
271795Specification for pillar taps for Water supply purposes.
282115Code of practice for flat roof finish: mudphuska
292204Code of practice for construction of reinforced concrete shell roof
302210Criteria for the design of R.C. shell structures and folded plates.
312267Polystyrene moulding and extrusion materials – Specifications
322326Specification for Automatic Flushing Cisterns for Urinals (Other than plastic cisterns)
332387Method of test for aggregates for concrete.
342438Specification for roller pan mixer
352502Code of practice for bending and fixing of bars for concrete reinforcement
362505Specification for concrete vibrators , immersion type
372506Specification for screed board concrete vibrator
382514Specification for concrete vibrating tables
392556Vitreous sanitary appliances (vitreous china) -Specifications
402571Code of practice for laying insitu cement concrete flooring
412633Method of testing uniformity of coating on zinc Coated articles
422645Specification for integral cement water proofing compounds
432645Specification for integral water proofing compounds for cement mortar & concrete
442722Specification for portable swing weigh batchers for concrete (single & double bucket type)
452750Specification for steel scaffoldings.
462751Code of practice for welding of mild steel structures are folded plates
472963Specification for Copper alloy waste fittings for Wash basins and Sinks.
483025Methods of sampling and test (physical and chemical) for water used in industry.
493076Specification for low density polyethylene pipes for potable water Supplies.
503087Particle boards of wood and other ignocellulogic materials (medium density) for general purposes – specifications
513144Methods of test for mineral Wool thermal insulation materials
523201Criteria for design and construction of precast concrete trusses.
533344Specification for pan vibrators
543346Method of the determination of thermal conductivity of thermal insulation materials
553348Specification for fibre insulation boards
563370Code of practice for concrete (Part I to IV structures for storage of liquids
573384Specification for bitumen primer for water proofing and damp proofing
583414Code of practice for design and installation of joints in buildings
593558Code of practice for use of immersion vibrators for consolidating concrete
603935Code of practice for composite construction
614014Code of practice for steel tubular, scaffolding
624031Method of physical tests for hydraulic Cement
634656Specification for form vibrators
644671Expanded polystyrene for thermal insulation purposes
654990Specification for plywood for concrete shuttering work
665382Specification for rubber sealing rings for gas mains, water mains and sewers
675688Methods of test of performed block type and pipe covering type thermal insulations
6810192Specifications for synthetic resin bonded glass fibre (SRBGF) for electrical purposes.
6913592Unplasticised polyvinyl chloride (UPVC) pipes for soil and Waste discharge system for inside and outside building.
7014753Specifications for polymethyl Methacrylate (PMMA) (Arylic) sheets
7114871Specifications for products in fibre reinforced cement – Long corrugated
72 1254 : 1991Corrugated Aluminium Sheet – Specification.
73 8329 : 2000Centrifugally cast (span) ductile Iron pressure Pipes for water, gas and Sewage-Specification.
7410028 (Part II) 1981Selection, installation and maintenance of transformers (Installation)
7510042 – 1981Site Investigations for foundation in gravel – boulder deposit.
7610262 – 1982Recommended Guidelines for concrete mix design.
7710297 – 1982Design and Construction of Floors and Roofs using Precast Reinforced/ Prestressed Concrete Ribbed or Cored Slab units.
7810379 – 1982Field control of moisture and compaction of soils for embankment and subgrade
7910589 – 1983Specification for equipment for subsurface sounding of soils
801080 – 1985Shallow foundations in soils (other than Raft, Ring and Shell) – (2 copies)
811172 – 1993Basic requirements for water supply, drainage and sanitation
8211973-1986Treatment of rock foundations, core and abutment contacts with rock, for embankment dams
831200 (PTΧ)Method of measurements of building and civil engineering works: Ceiling & Lining
8412070 – 1987Design and construction of shallow foundations on rocks
851255 – 1983Installation and maintenance of power cables up to and including 33 kv
8612955 (Part-2) 1990IN-SITU Determination of rock mass deformability using a flexible dilatometer
8713072 ; 1991Sulphur Hexafluoride for Electrical purposes – Specification
8813365 (Part-2) 1992Quantitative classification systems of rock mass – guidelines
891367 (PT-13)Technical supply conditions for threaded steel fasteners pt. 13 hot dip galvanized coating on threaded fasteners
901391 (part 2) 1992Room Air Conditioners (Split Air Conditioners)
9114 862Fibre cement flat sheets – specifications
9214268 : 1995Uncoated stress relieved low relaxation seven-ply strand for prestressed concrete-specification.
9314687: 1999False work for Concrete Structures – Guidelines
941477 (Part-1) 1971Painting of Ferrous metals in buildings (Pretreatment)
951477 (Part-2) 1971Painting of Ferrous metals in buildings (Painting)
961489 (Part-2)1991Portland – Pozzolana cement – specification (calcined clay based)
9714900 – 2000Transparent float glass
9815284 (Part-1) 2003Design and construction for ground Improvement-guidelines-part 1 (stone columns)
991554 (Part 1) 1988PVC insulated (Heavy Duty) Electric Cables
1001566 – 1967Hard – Drawn steel wire Fabric for concrete reinforcement
1011566 – 1982Specification for Hard-Drawn steel wire fabric for concrete reinforcement
1021641 – 1988Fire safety of building (General)
1031888-1992Method of Load Test on Soils
1041893 – 1984Criteria for earthquake resistant design of structures – 2 copies
1051893 (Part – 1) 2002Criteria for Earthquake resistant design of structures – 2 copies
1061893 (Part –1) 2002Criteria for earthquake resistant design of structures
1071893 (Part-1)Explanatory Examples on Indian Seismic
1081904 – 1986Design and construction of foundations in soils
1091904 – 1986Design and Construction of foundations in soils
1102026 (Part – 5) 1994Power Transformers
1112026 (Part I) 1977Specification for power Transformers (General) – 2 Copies
1122026 (Part II) 1977Power Transformers, Part-II Temperature – Rise
1132026 (Part III) 1981Specification for power transformers (Insulation, Levels, Dielectric tests)
1142062-1992Steel for General Structural purposes – specification
1152064 : 1993Selection, Installation and maintenance of sanitary appliances
1162095 (PT-1)Gypsum plaster boards (Pt.1) plain Gypsum plaster boards
1172132-1986Thin welded tube sampling of soils
1182190 : 1992Selection, Installation and maintenance of first-aid fire extinguishers
1192386 (Part-I-V) 1963Test for Aggregates for concrete
1202440:1975Daylighting of Buildings
1212470 (part-1) 1985Installation of Septic Tanks (Part-1) Design criteria and construction
1222502 – 1963Bending and fixing of bars for concrete reinforcement.
1232505 : 1992Concrete vibrators – Immersion Type-General Requirements
1242548 (Part-1Plastic Seats and Covers for Water closets Part 1: Thermo Set Seats and covers – Specifications
1252548 (Part-2)Plastic seats and covers for water closets Part 2: Thermoplastic seats and covers.- Specifications
1262556 (Part -14)Specific requirements of integrated squatting pans.
1272556 (Part -15)Specific requirements of universal water closets.
1282556 (Part-1) Part-1General requirements.
1292556 (Part-2)Specific requirements of Wash-down water closets.
1302556 (Part-3)Specific squatting pans.
1312556 (Part-4)Specific requirements of Washbasins.
1322556 (Part-5)Specific requirements of laboratory sinkS.
1332556 (Part-6) Part-6Specific requirements of Urinals & Partition plates
1342556 (Part-7)Specific requirements of accessories for sanitary appliances
1352571 – 1970Laying IN – SITU cement concrete flooring.
1362571-1970Laying IN-SITU cement concrete flooring
137269 : 1989Ordinary Portland Cement, 33 grade- specification.
1382720 (Part 5) 1985Methods of test for soils
1392720 (Part 8) 1983Methods of test for soils
1402792-1964Design and construction of stone slab over joist floor
141280 – 1978Mild Steel wire for general engineering purposes.
1422911 (Part – III) 1980Design and construction of pile foundations (Under-Reamed piles)
1432911 (Part-4) 1985Design and construction of Pile foundations (Load Test on Piles)
1442950(Part 1) 1981Design and construction of raft foundations (Design)
1452974 (Part I) 1982Design and construction of machine foundations
1463007 (PT.1)Code of practice for laying of asbestos cement sheets: part- 1 corrugated sheets
1473043 – 1987Code of practice for earthing – 2 copies
1483103 – 1975Industrial Ventilation
1493419 – 1989Fittings for rigid non- metallic conduits
1503443 – 1980Specification for Crane rail sections
1513770 (P-1) 1965Concrete structure for the storage of liquids (Part – 1,2)
1523812 – 1981Specification for Fly ash for use as pozzolara and Admixture.
153383 – 1970Coarse and fine aggregates from natural sources for concrete.
1544014 (Part-1) 1967Steel Tubular Scaffolding (Definitions and materials )
1554082-1996Stacking and storage of construction materials and components at site-recommendations. – 2 copies
156432 (Part-I) 1982Mild Steel and medium tensile steel bars and hard – drawn steel wire for concrete reinforcement
157432-1982Mild Steel and medium Tensile Steel Bars and hard-Drawn Steel wire for concrete Reinforcement (part-1) Mild Steel and medium Tensile steel Bars
1584326-1993Earthquake Resistant Design and Construction of Buildings
159459-1992Corrugated and Semi-corrugated Asbestas Cement sheets specification.
1604631 – 1986Laying of Epoxy resin floor toppings
1614885 – 1988Specification for Sewer Bricks
1624926 : 2003Ready Mixed concrete
1634971 – 1968Selection of Industrial floor finishes
1644984 – 1995High Density Polyethylene pipes for water supply – specification
1654985 : 2000Unplasticized PVC Pipes for Potable water supplies – specification
1665491 – 1969Laying in Situ granolithic concrete floor topping
1676006-1983Uncoated Stress relived Strand for Prestressed concrete
1686313 (Part-II) 1981Anti-Termite measures in buildings
1696313 (Part-III) 1981Anti-Terminate measures in buildings Part-III Treatment for existing buildings
1706403 – 1981Determination of bearing capacity of shallow foundations
171650 : 1991Standard Sand for Testing Cement – Specificaiton
172694 – 1990PVC Insulated cables for working voltages up to and in including 1100 volts
1737098 (Part 1) 1988Cross linked polyethylene insulated theermoplastic Sheathed cables
1747098 (Part 2) 1985Cross linked polyethylene insulated PVC Sheeted Cables
1757098 (Part-I) 1988Cross linked polyethylene insulated PVC sheathed cables.
1767272 (Part – 1) 1974Labour output constants for building work (north zone)
1777317-1993Uniaxial Jacking Test for modules of Deformation of rock.
178732 – 1989Electrical Wiring installations
179771 (Pt.1)Specification for glazed fire clay sanitary appliances: Part 1: General requirements.
180771 (Pt.-2)Specification for glazed fire clay sanitary appliances: Part 2: Specific requirements of kitchen and laboratory sink.
181783 – 1985Laying of Concrete Pipes
1827861 (Part-II) 1981Extreme weather concreting (Part – II) recommended Practice for cold weather concreting.
183800 : 2007General construction in steel
1848009 – 1976Calculation of Settlement of foundations
1858009 (Part-I) – 1976Calculation of settlements of foundations.
186801-1975Use of cold-formed light Gauge steel structural members in general building construction.
187811 – 1987Cold formed light gauge structural steel sections
1888142 – 1976Determining setting time of concrete by penetration resistance
1898142-1976Determining setting time of concrete by penetration resistance.
190822 – 1970Inspection of welds
1918519 – 1977Guide for selection of industrial safety equipment for body protection
1928520 – 1977Guide for selection of industrial safety equipment for eye, face and ear protection.
193875 (part-4) 1987Design loads (other than earthquake ) for buildings and structures (part-4) snow loads.
1949013 – 1978Method of making, Curing and determining compressive strength of accelerated-cured concrete test specimens.
195908 – 1975Fire Hydrant, Stand Post Type
1969103 – 1999Concrete Admixtures – Specification.
1979143 – 1979Determination of unconfined compressive strength of rock materials
1989537 (Part I) 1980Conduits for Electrical Installations ( General Requirements )
1999595 : 1996Metal – Arc welding of carbon and carbon manganese steels – recommendation.
200IS:2720 (part-17) 1986Methods of test for soils (part-17) Laboratory Determination of Permeability.
201IS:2911 (Part–I) Sec I)-1979Design and construction of Pile foundations (part – 1) concrete piles section : Driven Cost in situ concrete piles.
202IS:875 (Part-1) – 1987Dead loads – Unit weights of building materials and stored materials.
203SP-7: 1983 (Part-IV)National Building code of India – 1983
Soil Mechanics

Seepage of soil and Flownet.

Published by:

Voids in a soil mass give rise to permeability and when a soil is permeable, water can seep through. This phenomenon of water flowing through the soil is called seepage.

 

  • Seepage pressure

Water exerts a pressure on the soil through which it percolates. This pressure is known as seepage pressure. It is produced due to the resistance or frictional drag of water flowing through the soil and it acts in the direction of flow.

If ‘h’ is the hydraulic head or head lost which causes the water to flow through a soil mass of thickness ‘L’, then seepage pressure (ps) developed is given by –

ps = 𝛾wh   [𝛾w = Sp.weight of water]

ps = 𝛾w.(h/L).L

ps = 𝛾w.i.L   [i = hydraulic gradient]

ps = iL 𝛾w

.. Total seepage force (Fs) = ps.A   [X-sec area of soil over which seepage pressure acts]

= iL𝛾wA

The above force is uniformly distributed throughout the volume of the soil mass.

.. Seepage force pr unit volume =  = i𝛾w

Depending upon the direction of flow, the seepage may increase or decrease the vertical effective pressure of soil.

If flow occurs in the downward direction, the effective pressure is increased and if it occurs upwards, the effective pressure is decreased.

.. effective pressure (σ’) in a soil mass subjected to seepage pressure is given by –    σ’ = 𝛾sub.L±ps   [𝛾sub = Submerged unit wt. of soil mass]

 

[+ve sign for seepage in downward direction & -ve for seepage in upward direction]

 

  • Importance of seepage Analysis

The seepage pressure is responsible for the phenomenon known as quick sand and is of vital importance in the stability analysis of earth pressure subjected to the action of seepage.

 

  • Assumption in seepage flow analysis
  1. The soil is fully saturated.
  2. The soil particles and water are incompressible.
  • The flow is laminar and Darcy’s law is valid.
  1. The soil layer is pervious.
  2. The quantity of water entering into the soil element is same as the quantity of leaving water.

 

  • Quick sand condition

When water flows in an upward direction through the soil, effective pressure = = 𝛾sub.L- ps

If ‘ps’ equals the pressure due to submerged weight of soil, the effective pressure reduces to zero. In such a case cohesion less soil loses all its shear strength and bearing capacity and the soil particles tend to be lifted up along with the flowing water. This phenomenon is termed as quick sand condition or quick condition or boiling condition or quick sand.

It may be noted that quick sand is not a type of sand but a flow condition occurring within cohesion less soil when its effective pressure is reduced to zero due to upward seepage pressure.

Thus during quick condition –

Ps = 𝛾sub.L

Or, i.L.𝛾w = 𝛾sub.L

Or, i = ic = 𝛾sub/𝛾w = (G-1)/(1+e)

 

The hydraulic gradient at which quick sand occurs is called the critical hydraulic gradient.

 

  • Flow net

The network framed by the two sets of curves like flow lines and equipotential line is called flow net.

The path which a particle of water follows in its course of seepage through a saturated soil mass is called flow line.

Every strip between two neighboring flow lines is called flow channel.

 

Along each flow line, there will be different head of water. A line connecting all points of equal head is called equi-potential line.

Every section of a flow channel between two successive equipotential lines is called field.

 

  • Properties of flow net
  1. Flow lines and equipotential lines meet at right angles.
  2. Flow lines never cross each other.
  • Equipotential lines never cross each other.
  1. The fields are almost square.
  2. Same quantity of water flows through each channel.
  3. Same potential drop occurs between the successive equip-potential lines.
  • Smaller is the field, greater will be the hydraulic gradient.
  • Flow lines and equi-potential lines are smooth curves.

 

  • Application of flow net

Flow net can be utilized for the following purposes –

  1. Determination of seepage.
  2. Determination of hydraulic pressure.
  • Determination of seepage pressure.
  1. Determination of exit gradient.

 

 

Soil Mechanics

Permeability of Soil and Darcys Law.

Published by:

Permeability of soil

  • Permeability

It is defined as the property of a porous material which permits the passage or seepage of water (or other fluid) through its interconnecting voids.

 

A material having continuous void is called permeable.

 

Gravels are highly permeable, while stiff clay is least permeable but for practical purposes clay is considered as impermeable.

 

  • Darcy’s law

The percolation of water through soil was first studied by “Darcy” in (1856), who demonstrated experimentally that for flow missing condition in a saturated soil, the rate of flow i.e. discharge is proportional to hydraulic gradient.

i.e. q = KiA

or, v = q/A = Ki  ——-(i)

[Where, q = Rate of flow

A = Cross Sec. Area of soil mass, perpendicular to the direction of flow

i = Hydraulic gradient

v = Avg. discharge velocity

K = Darcy coefficient of permeability]

From equation (i)

If i = 1 then v = K

Thus coefficient of permeability may be defined as the average velocity of flow that will occur through the total cross sec. Area of soil under unit hydraulic gradient.

Unit of K is cm/sec or m/sec.

 

  • Note

“v” is called superficial velocity (apparent). Actual velocity of water flowing in the voids is called seepage velocity (vs).

vs = v/n

  • Validity of Darcy’s law

Flow of water may be laminar or turbulent depending upon the mode of travel of water particles. If all water particle follow definite path which never intersect one another, the flow is termed as laminar.

If the particle paths are haphazard and irregular, it is turbulent flow.

Darcy’s law is valid only for laminar flow. Again the soil must be saturated.

 

  • Factors affecting Permeability

From Poiseuille Equation,    Q = cde2xxiA

Comparing the equation with Darcy’s law –    K = cde2x

Thus the following factors affecting permeability –

 

(i) Grain size

(ii) Properties of pore fluid

(iii) Void ratio of soil

(iv) Structural arrangement of soil particles and stratification

(v) Entrapped air and foreign matter

(vi) Adsorbed water

 

  • Grain size

Permeability varies approximately as the square of the grain size.

As per Allen Hazen formula, for clean sand with particle size between 0.1 mm and 3 mm,

K = CD102

[CD10 = Effective grain size in cm

K = Coefficient of permeability in cm/sec

C = Constant ≈ 100

 

  • Properties of pore fluid

The permeability is directly proportional to the unit weight of percolating water and inversely proportional to its viscosity

i.e. K ∞ 𝛾w/𝜂

[𝛾w = Unit weight of water

𝜂 = Viscosity of water]

 

  • Void ratio of soil

The variation of permeability with void ratio (e) has been empirically established from laboratory investigations and the equations are –

K ∞ e3/(1+e)

Sometimes it may be – K ∞ e2

[Where, e = void ratio of soil]

 

  • Structural arrangement of soil particles and stratification

For the same soil at the same void ratio, the permeability may vary with different methods of placement or compaction resulting in different arrangement and shape of voids.

It is much pronounced in fine grained soils because their natural structure when once disturbed can never be reconstructed.

Stratified soil masses have marked variation in their permeability in the direction parallel and perpendicular to stratification, the permeability parallel to stratification being always greater.

 

  • Entrapped air and foreign matter

Permeability is greatly reduced if air entrapped in the voids thus reducing its degree of saturation as we know the theory of permeability where relations have been experimentally established on soils with 100% degree of saturation.

It will also be affected if organic impurities are present in the pores of a soil.

[Thickness = 10 to 15 Ao where 1 Ao = 10-10 m

 

  • Adsorbed water

The adsorbed water surrounding the fine soil particles is not free to move and hence it causes an obstruction to the flow of free water by reducing the effective pore space, thus affecting permeability.

[ As per Casagrande 0.1 may be taken as void ratio occupied by adsorbed water and accordingly

K ∞ (e – 0.1)2 ]

 

  • Determination of permeability in the laboratory by constant head method

 

  • Object

To determine the coefficient permeability of coarse grained soil.

 

  • Apparatus

Constant head permeameter with all accessories, Stop watch, Graduated measuring jar etc.

  • Materials

Coarse grained soil, water.

  • Theory

As per Darcy’s law –

q = KiA

Or,

Or, K =     —–(i)

[ Where, Φ = Volume of water collected in the measuring jar in time ‘t’.

h = Constant head of water.

L = Length of soil sample.

A = Cross sectional area of soil sample perpendicular to the flow of water.

q = Discharge.

i = Hydraulic gradient.

K = Coefficient of permeability of soil ]

  • Procedure

(i) The soil sample is placed in the vertical cylinder between two porous plates, as shown in fig. and the bottom tank is filled with water missing

(ii) The outlet tube of the constant head tank is connected to the inlet of the permeameter after removing the air.

(iii) The hydraulic head will be adjusted such that ‘h’ will be constant during the test.

(iv) The test will be started now and stop watch will be ‘on’. Test will be continued for some convenient time during which water collected in the measuring jar. The time is recorded.

 

The test should be repeated at least twice more under the same head and for the same time interval.

From this, we will get average value of ‘Φ’

Knowing Φ, L, h, A and t, the coefficient of permeability of soil sample can be obtained from equation(i)

 

  • Conclusion

To avoid large error, it is necessary that quantity of water collected should be large. Hence this method is suitable for pervious soil or coarse grained soil.

 

  • Determination of permeability in the laboratory by falling head test

 

  • Object

To determine the coefficient of permeability of fine grained soil.

 

  • Apparatus

Falling head permeameter with all accessories, stop watch etc.

 

  • Materials

Fine grained soil, water

 

  • Theory

In falling head test, a stand pipe is fitted on the top of the permeameter and the change in hydraulic head with time is recorded.

Let ‘h’ be the head of water at any intermediate time ‘t’, from where head drops by ‘dh’ in time ‘dt’

Now, discharge in time dt,

q =

[ -ve sign is used as head decreases when time increases]

Again as per Darcy’s law –

q = KiA

  • Procedure

(i) The soil sample is placed in vertical cylinder between two porous plates. The inside area of the cylinder is measured which gives cross sectional area of soil sample (A) and length of the soil sample (L) is measured between the porous plates.

(ii) The permeameter mould assembly is placed in the bottom tank and the bottom tank is filled with water.

(iii) The permeameter is connected to the stand pipe having cross sectional area ‘a’, water is permitted to flow for some reasonable time.

(iv) With the help of stop watch, the time interval (T) required for the water level in the stand pipe to fall from some convenient initial head (h1) to final head (h2) is noted.

(v) Knowing the values of A, L, a, T, h1 and h2, coefficient of permeability (k) will be obtained from the above equation.

 

  • Conclusion

In this test, quantity of water collected is small and hence this method is suitable exclusively for fine grained soil.

 

 

 

 

 

 

 

 

 

 

 

 

Soil Mechanics

Consistency or Atterberg Limits of Soil

Published by:

  • Introduction

Consistency is a term used to describe the degree of firmness of soil in a qualitative manner by using descriptions such as soft, medium, stiff or hard. It indicates the relative ease with which a soil can be deformed.

 

  • This term is associated only with fine grained soils, especially clays.

 

  • Atterberg Limits

The physical properties of clays are considerably influenced by the amount of water present in them.

 

Depending upon the water content, the following four stages or states of consistency are used to describe the consistency of clayey soil –

  1. Liquid State.
  2. Plastic State.
  • Semisolid State.
  1. Solid State.

 

The boundary water contents at which the soil undergoes a change from one state to another are called consistency limits.

In 1911, Mr. Atterberg (A Swedish soil scientist) first demonstrated the significance of these limits, hence these limits are termed as Atterberg limits. These limits are liquid limit, plastic limit and shrinkage limit.

They are of great significance in understanding the behaviour of clays.

  • Liquid Limit (wL)

The boundary water content between liquid state and plastic states of consistency of soil is called liquid limit (As shown in above figure.)

It can also be defined as minimum water content at which soil flows by gravity with a little or no shearing resistance.

 

  • As per laboratory concern, w.r.t. standard liquid limit device, it is defined as the minimum water content at which a part of soil cut by a groove of standard dimension will flow together for a distance of 12mm (0.5’’) under an impact of 25 blows in the device.

 

  • Plastic Limit (wp)

The boundary water content between plastic state and semisolid state of consistency of soil is called plastic limit. (As shown in the fig.)

It can also be defined as minimum water content at which a soil will just begin to crumble when rolled into a thread of about 3mm in diameter.

 

  • In the plastic state, the soil can be moulded to different shapes without rupturing it.

 

  • Shrinkage Limit (ws)

The boundary water content between semisolid state and solid state of consistency of soil is called shrinkage limit (As shown in fig.)

It can be defined as the maximum water content at which a reduction in water content will not cause a decrease in the volume of soil mass. It is also the lowest water content at which a soil can still be completely  saturated.

 

  • In the semisolid state, the soil does not have plasticity and it will be brittle.

 

  • Shrinkage Ratio (SR)

It is defined as the ratio of a given volume expressed as a percentage of dry volume, to the corresponding change in water content above shrinkage limit.

i.e. SR =

Where, V1 = vol. of soil mass at water content w1 %

V2 = vol. of soil mass at water content w2 %

Vd = vol. of dry soil mass.