#Soil Mechanics
What is Seat of settlement?
Terzaghi recommended that vertical stress is considered of negligible magnitude when smaller than 20 % of the applied contact pressure and that about 80% of the total settlement takes place due to compression of soil within this pressure bulb and the region within the isobar is known as seat of settlement or active zone.
For an elastic isotropic, semi-infinite solid media, the depth of the 20% of the applied contact pressure is about 1.5B where B is the width of the loaded area of footing. Thus the wider the loaded area, deeper is its effect.
The depth within which soil compression contributes significantly to surface settlement is called as critical depth. For fine-grained soils the Critical depth extends to the point where the applied stress decrease to 10 % effective over burden pressure. For coarse grained soils, the critical depth extends to a point where the applied stress decreases to 20 % of the effective overburden pressure.
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What is Seat of settlement?
Terzaghi recommended that vertical stress is considered of negligible magnitude when smaller than 20 % of the applied contact pressure and that about 80% of the total settlement takes place due to compression of soil within this pressure bulb and the region within the isobar is known as seat of settlement or active zone.
For an elastic isotropic, semi-infinite solid media, the depth of the 20% of the applied contact pressure is about 1.5B where B is the width of the loaded area of footing. Thus the wider the loaded area, deeper is its effect.
The depth within which soil compression contributes significantly to surface settlement is called as critical depth. For fine-grained soils the Critical depth extends to the point where the applied stress decrease to 10 % effective over burden pressure. For coarse grained soils, the critical depth extends to a point where the applied stress decreases to 20 % of the effective overburden pressure.
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π1
Important tips for
#BMC
@MACEDHULE
1.As fast as possible cover entire technical syllabus(the one recommended)!!
2. Do not solve numericals
3. Ssc JE level technical MCQS are expected
4.Read as much matter as u can!!
5.Solve Gate previous 1 mks question, ESE theoretical questions, ssc previous years & MPSC previous years questions. Cover all these mcqs first.
When u are done with these questions(these are almost 12000+ questions) then only go for objective books like, PN khanna & VS murthy
6.There are around 8 most important reasoning topics as far as IBPS is concerned.
Solve 5 questions of Evry topic on daily basis, this will help u become fluent in reasoning thereby increasing your speed and accuracy!!
7.focus on
#Solid Mechanics
#Soil Mechanics
#Concrete technology
#Highway
#Survey
#Environment
#QSV
After covering these topics then only move to others.
β€SOMβ€Soilβ€Environmentβ€ Will make the difference!!!
8.Remember a proper balance between technical and nontechnical is keyword of getting through #BMC!!!!
9.Those already done with technical Study everything, don't leave anything from civil engineering.
Good luck All!!!
Join us @MACEDHULE
Regards,
Maharashtra Academy for Civil Engineers, Dhule
#BMC
@MACEDHULE
1.As fast as possible cover entire technical syllabus(the one recommended)!!
2. Do not solve numericals
3. Ssc JE level technical MCQS are expected
4.Read as much matter as u can!!
5.Solve Gate previous 1 mks question, ESE theoretical questions, ssc previous years & MPSC previous years questions. Cover all these mcqs first.
When u are done with these questions(these are almost 12000+ questions) then only go for objective books like, PN khanna & VS murthy
6.There are around 8 most important reasoning topics as far as IBPS is concerned.
Solve 5 questions of Evry topic on daily basis, this will help u become fluent in reasoning thereby increasing your speed and accuracy!!
7.focus on
#Solid Mechanics
#Soil Mechanics
#Concrete technology
#Highway
#Survey
#Environment
#QSV
After covering these topics then only move to others.
β€SOMβ€Soilβ€Environmentβ€ Will make the difference!!!
8.Remember a proper balance between technical and nontechnical is keyword of getting through #BMC!!!!
9.Those already done with technical Study everything, don't leave anything from civil engineering.
Good luck All!!!
Join us @MACEDHULE
Regards,
Maharashtra Academy for Civil Engineers, Dhule
Maharashtra Academy for Civil Engineers:
Maharashtra Academy for Civil Engineers
#BMC Free Mock tests
#Civil engg competitive exam
#Imp topics, notes, framed Objectives
#Soil Mechanics specialist
https://t.me/MACEDHULE
Imp one liners -
Offcourse GT che taknar adhiπ
Maximum void ratio is 0.91
Minimum void ratio is 0.35
#void ratio & watercontent has no upper limit.
#porosity can lie within 0 to 100% but not zero and not 100%
#degree of saturation can be zero(dry soil), can be 100%(fully saturated soil, or take intermediate value(moist or partialy saturated soil)
Water content can be found out most accurately by oven drying method, and in-situ by Radiation method
If specific gravity is know then it can be found out by pycnometer also.
Core cutter method and sand replacement method are useful in finding in-situ unit weights of soil
Specific gravity can be found out by pycnometer and indirectly by shrinkage limit.
(NOTE-Degree of saturation at shrinkage limit is 1)
For organic soils specific gravity ranges in 1.2-1.4
And for inorganic soils it is,
2.65-2.80
Sedimentation analysis consist of pipette analysis and hydrometer method
There are "3" corrections in hydrometer method.
Well graded soils have a greater compaction property .
Poorly garaded or uniformly graded consist of same grain size hence voids are there.
A special case of poorly graded soil is the one in which particles are either in excess or deficient called as gap graded soils!
If D10=150 micron, it means 10% particles are finer than 150 micron. . .
Note that D10 is called effective particle size.
For well graded soils 1<Cc<3
For well graded gravels Cu>4
For Well Graded sands Cu>6
For poorly graded soils Cu=1
#Trick?????
G for gavaskar, S for sachin
Gavaskar four(ΰ€ΰ₯ΰ€ΰ€Ύ) Marto π
Sachin six martoπ
In casagrandes test to find liquid limit water content is found out corresponding to 25 no. Of blows
Plasticity index of sands is zero
Toughness index is (plasticity index/flow index). . .. (#MMRDA 2015)
Sensitivity is always greater than unity and is directly proportional to thixotrophy.
Soil activity was explained by skempton.
Out of various unit weights of soils, saturated unit weight is maximum while submerged unit weight is minimum
( #Gemeraly submerged unit weight is only 50% of saturated weight--------- this point is related to bearing capacity---when water table rises to ground surface unit weight of water falls to 50% hence bearing capacity under submergence condition is reduced by 50%)
Plasticity and activity of montmorilonite is maximum.
Bentoninte is purest form of clay which consist of 98% clay
As compared to normal soils expansive soils have
1. More liquid limit
2. Less plastic limit
3.less shrinkage limit
4.more volumetric shrinkage
5. More plasticity index( from pt. 1 & pt 2)
Clay is finer than 0.002 mm and is flacky in shape(#TRANSCO dec 2016)
Silt is finer than 0.075 mm and coarser than 0.002 mm
Boulders are greater than 300mm
Gravel size is greater than 4.75mm and smaller than 80mm
As per IS 1498:1970π classification coarse grained soils are classified into 8 groups while fine grained soils are classified into 10 groups
Thus there are total 18 groups
Eg.
GS would be sandy gravel
Gp - poorly graded gravel
GW- well graded gravel etc
Thats vimp about 1st
2 chapters.
πππ
Join us @MACEDHULE
Maharashtra Academy for Civil Engineers
#BMC Free Mock tests
#Civil engg competitive exam
#Imp topics, notes, framed Objectives
#Soil Mechanics specialist
https://t.me/MACEDHULE
Imp one liners -
Offcourse GT che taknar adhiπ
Maximum void ratio is 0.91
Minimum void ratio is 0.35
#void ratio & watercontent has no upper limit.
#porosity can lie within 0 to 100% but not zero and not 100%
#degree of saturation can be zero(dry soil), can be 100%(fully saturated soil, or take intermediate value(moist or partialy saturated soil)
Water content can be found out most accurately by oven drying method, and in-situ by Radiation method
If specific gravity is know then it can be found out by pycnometer also.
Core cutter method and sand replacement method are useful in finding in-situ unit weights of soil
Specific gravity can be found out by pycnometer and indirectly by shrinkage limit.
(NOTE-Degree of saturation at shrinkage limit is 1)
For organic soils specific gravity ranges in 1.2-1.4
And for inorganic soils it is,
2.65-2.80
Sedimentation analysis consist of pipette analysis and hydrometer method
There are "3" corrections in hydrometer method.
Well graded soils have a greater compaction property .
Poorly garaded or uniformly graded consist of same grain size hence voids are there.
A special case of poorly graded soil is the one in which particles are either in excess or deficient called as gap graded soils!
If D10=150 micron, it means 10% particles are finer than 150 micron. . .
Note that D10 is called effective particle size.
For well graded soils 1<Cc<3
For well graded gravels Cu>4
For Well Graded sands Cu>6
For poorly graded soils Cu=1
#Trick?????
G for gavaskar, S for sachin
Gavaskar four(ΰ€ΰ₯ΰ€ΰ€Ύ) Marto π
Sachin six martoπ
In casagrandes test to find liquid limit water content is found out corresponding to 25 no. Of blows
Plasticity index of sands is zero
Toughness index is (plasticity index/flow index). . .. (#MMRDA 2015)
Sensitivity is always greater than unity and is directly proportional to thixotrophy.
Soil activity was explained by skempton.
Out of various unit weights of soils, saturated unit weight is maximum while submerged unit weight is minimum
( #Gemeraly submerged unit weight is only 50% of saturated weight--------- this point is related to bearing capacity---when water table rises to ground surface unit weight of water falls to 50% hence bearing capacity under submergence condition is reduced by 50%)
Plasticity and activity of montmorilonite is maximum.
Bentoninte is purest form of clay which consist of 98% clay
As compared to normal soils expansive soils have
1. More liquid limit
2. Less plastic limit
3.less shrinkage limit
4.more volumetric shrinkage
5. More plasticity index( from pt. 1 & pt 2)
Clay is finer than 0.002 mm and is flacky in shape(#TRANSCO dec 2016)
Silt is finer than 0.075 mm and coarser than 0.002 mm
Boulders are greater than 300mm
Gravel size is greater than 4.75mm and smaller than 80mm
As per IS 1498:1970π classification coarse grained soils are classified into 8 groups while fine grained soils are classified into 10 groups
Thus there are total 18 groups
Eg.
GS would be sandy gravel
Gp - poorly graded gravel
GW- well graded gravel etc
Thats vimp about 1st
2 chapters.
πππ
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π₯ SPECIAL BATCH for STRUCTURAL SUBJECTS
of MPSC MAINS (Paper 1)
πBatch Starting:-
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π₯Only Structural Subjects Fees:-
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of MPSC MAINS (Paper 1)
πBatch Starting:-
01 July 2019
π₯Only Structural Subjects Fees:-
Rs.12000/- only
π₯Special Features:-
1)Fees:-Rs.12000/-(Paper 1)
2)Hostel Facilities available at Reasonable Rate..
3)Proper Study Notes.
4)Practise MCQ's
5)IES/MES/GATE Qualified & Well Experienced Faculties...
π₯Register Fast...Limited Seats only...
πFor Registration Contact:-
8459254533/
8459467941
πNOTE:-Friends,this Batch will definatey Help those aspirants who are very weak in Structural subjects & wish to take Coaching for The Subjects u really want...Grab this Golden opportunity of MPSC this year..
We are here to help u all..
Thanks,
Regards,
t.me/MACEDHULE
Telegram
MACE Academy
Civil Engineering Competitive Exam Guidance
π² MACE Academy Application link:
https://play.google.com/store/apps/details?id=co.lynde.zhjfq
PYQ series VIDEO Link:
https://youtube.com/playlist?list=PLDpz3kV5eQuM&si=Dto5XNPHpIcd9um1
π² MACE Academy Application link:
https://play.google.com/store/apps/details?id=co.lynde.zhjfq
PYQ series VIDEO Link:
https://youtube.com/playlist?list=PLDpz3kV5eQuM&si=Dto5XNPHpIcd9um1
π₯Transco/Genco:
β¨Standard penetration test (SPT) important aspects:
π¦Test Process as per IS 2131
π¦Split-spoon sampler is used
π¦Sampler length= 650mm
π¦Hammer weight= 65 kg
π¦Free fall height= 75 cm
π¦Total penetration = 450mm
π¦Penetration for Blow Count= Later 300mm
π¦Seating Drive= Initial 150mm
π¦Corrections :
Two corrections are applied sequentially.
1.overburden correction.
2.Dilatancy/Submergence correction.
#soil
@macedhule
β¨Standard penetration test (SPT) important aspects:
π¦Test Process as per IS 2131
π¦Split-spoon sampler is used
π¦Sampler length= 650mm
π¦Hammer weight= 65 kg
π¦Free fall height= 75 cm
π¦Total penetration = 450mm
π¦Penetration for Blow Count= Later 300mm
π¦Seating Drive= Initial 150mm
π¦Corrections :
Two corrections are applied sequentially.
1.overburden correction.
2.Dilatancy/Submergence correction.
#soil
@macedhule
π8
π₯Transco/Genco Very IMP:
π¦Indian Standard proctor test:
β‘οΈ
β‘οΈ
β‘οΈ
β‘οΈ
β‘οΈ
π¦Modified Proctor Test:
β‘οΈ
β‘οΈ
β‘οΈ
β‘οΈ
β‘οΈ
#soil
@macedhule
π¦Indian Standard proctor test:
β‘οΈ
Weight of hammer=2.6KGβ‘οΈ
Height of free fall=310mmβ‘οΈ
Number of layers=03β‘οΈ
Number of blows=25β‘οΈ
Volume of mould= 1000cmΒ³π¦Modified Proctor Test:
β‘οΈ
Weight of hammer=4.9 KGβ‘οΈ
Height of free fall=450mmβ‘οΈ
Number of layers=05β‘οΈ
Number of blows=25β‘οΈ
Volume of mould= 1000cmΒ³#soil
@macedhule
π16β€2
Geotech π§
πΊπΏ Sensitivity of soil -
β Most clay loses some of its strength and stiffness when remoulded or disturbed.
β Sensitivity is determined in the laboratory as the quotient(Ratio) of the undisturbed strength to the remoulded strength.
β Sensitivity = qu (undisturbed sample) / qu (remolded sample)
π Sensitivity Classification -
Sensitivity Classification
<2 Insensitive
2-4 Moderate
4-8 Sensitive
8-16 Very sensitive
16-32 Quick
#Soilπ€
Join @macedhule β
β Most clay loses some of its strength and stiffness when remoulded or disturbed.
β Sensitivity is determined in the laboratory as the quotient(Ratio) of the undisturbed strength to the remoulded strength.
β Sensitivity = qu (undisturbed sample) / qu (remolded sample)
Sensitivity Classification
<2 Insensitive
2-4 Moderate
4-8 Sensitive
8-16 Very sensitive
16-32 Quick
#Soil
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π10β‘1π1π€©1π1
1. Constant head permeability test
k= qL/Ah
2. Variable head permeability test
k = 2.303 aL/At [log (h1 / h2)]
1. Pumping out tests
2. Pumping in tests
1. Computation from the particle size or its specific surface
2. computation from the consolidation test data
1. Particle size
2. Structure of soil mass
3. Shape of particles
4. Void ratio
5. Properties of water
6. Degree of saturation
7. Adsorbed water
8. Impurities in water
#soil
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π₯ Geotech:
STABILITY OF SLOPES -
β FORCES CAUSING FAILURE OF SLOPES -
1. Gravitational force
2. Seepage force
3. Earthquake force
4. Construction equipment loads
β TYPES OF SLOPE FAILURES -
1. Translational failure
2. Rotational failure
3. Wedge failure
4. Compound failure
β TYPES OF SLOPES -
β Infinite slopes - natural slope
- translational failure
- e.g mountain
β Finite slopes- artificial slope
- rotational failure
- e.g embankment of
road
#soil
Join @macedhule
STABILITY OF SLOPES -
β FORCES CAUSING FAILURE OF SLOPES -
1. Gravitational force
2. Seepage force
3. Earthquake force
4. Construction equipment loads
β TYPES OF SLOPE FAILURES -
1. Translational failure
2. Rotational failure
3. Wedge failure
4. Compound failure
β TYPES OF SLOPES -
β Infinite slopes - natural slope
- translational failure
- e.g mountain
β Finite slopes- artificial slope
- rotational failure
- e.g embankment of
road
#soil
Join @macedhule
π8β‘2π2
1. The Ο = 0 method of slope analysis -
β’ For undrained saturated Clay's
β’ FOS =
sum of moments of maximum resisting forces/sum of moments of moving forces
β’Above is also given as
FOS = (C x R x arc length) / (W x d)
2. Method of Slices
β’ Used for all soils
β’ FOS =
(Ξ£ maximum resisting forces around the arc) / (Ξ£ moving forces around the arc)
3. Fellenious Method -
β’ identifies critical slip circle.
β’ For C-Ο soils centre of critical slip circle lies on fellenious line
β’ For pure clays, centre of critical circle is centre of circle
4. Bishop's method -
β’ Trial and error method
β’ Forces acting on sides of circle are considered
5. Friction Circle Method -
β’ Trial and error method
β’ FOS = C / Cm
Where C = cohesion
Cm= mobilized cohesion
6. Taylor's Stability Number Method -
β’ FOS = C / (SΞ³H)
#soil
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π9
Difference between General Shear Failure (GSF) and Local Shear Failure (LSF) -
GSF LSF
Angle of > 36Β° < 28Β°
Internal friction
Failure strain < 5% 10-20%
Density Index > 70% < 20%
Void Ratio < 0.55 > 0.75
#soil
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π7β€βπ₯4π±2π1
π₯ Geotech
STANDARD PENETRATION TEST -
β SPT value means no of blows required for 30 cm penetration.
β Insitu test
β Only for cohesioless soils
β Hammer weight = 65 kg
β Height of fall = 75 cm
Recorded value is corrected for overburden correction and dilatancy correction
β Denseness based on no of blows (N)
N Denseness
0-4 very loose
4-10 loose
10-30 medium dense
30-50 dense
>50 very dense
#soil
Join @macedhule β
STANDARD PENETRATION TEST -
β SPT value means no of blows required for 30 cm penetration.
β Insitu test
β Only for cohesioless soils
β Hammer weight = 65 kg
β Height of fall = 75 cm
Recorded value is corrected for overburden correction and dilatancy correction
β Denseness based on no of blows (N)
N Denseness
0-4 very loose
4-10 loose
10-30 medium dense
30-50 dense
>50 very dense
#soil
Join @macedhule β
π12β€2π1
Terzaghiβs bearing Capacity Theoryβ
β Terzaghi (1943) was the first to propose a comprehensive theory for evaluating the safe bearing capacity of shallow foundation with rough base.
β Assumptions -
1. Soil is homogeneous and Isotropic.
2. The shear strength of soil is represented by Mohr Coulombs Criteria.
3. The footing is of strip footing type with rough base.
It is essentially a two dimensional plane strain problem.
4. Elastic zone has straight boundaries inclined at an angle equal to Ξ¦ to the horizontal.
5. Failure zone is not extended above, beyond the base of the footing.
It means, Shear resistance of soil above the base of footing is neglected.
6. Method of superposition is valid.
7. Footing carries concentric and vertical loads.
8. Footing and ground are horizontal.
β Limitations -
1. The theory is applicable to shallow foundations
2. As the soil compresses, Ξ¦ increases which is not considered. Hence fully plastic zone may not develop at the assumed Ξ¦.
#soil
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π9β€1π₯1π±1
Classification of Pile
β Classification of pile with respect to load transmission and functional behaviour-
β’ End bearing piles (point bearing piles)
β’ Friction piles (cohesion piles )
β’ Combination of friction and cohesion piles
β Classification of pile with respect to type of material -
β’ Timber
β’ Concrete
β’ Steel
β’ Composite piles
β Classification with respect to function of pile -
β’ Bearing piles
β’ Friction piles
β’ Friction-cum-bearing piles
β’ Batter piles
β’ Fender piles
β’ Anchor file
β Classification of piles based on displacement of soil -
β’ Displacement type
β’ Non displacement type
#soil
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π7β€3π¨βπ»1
π’What is Hydraulic Gradient In Soils?
Suppose flow length =2m
& Head loss over given flow length=1.0m
Then hydraulic Gradient(i)=1/2=0.5
It means over a flow length of 1m,what is the magnitude of Head lost?π€
Ans is Hydraulic Gradient.π
Ex. For a Hydraulic Gradient of 1.5 find the head lost over a flow length of 4m.π
Solution:
Loss over 1m= Hydraulic Gradientπ€©
Loss over 4m=Xπ€©
Cross multiplication will give ,
1ΓX=4Γi
So X=4Γ1.5=6.0mπ
#soil
@macedhule
Suppose flow length =2m
& Head loss over given flow length=1.0m
Then hydraulic Gradient(i)=1/2=0.5
It means over a flow length of 1m,what is the magnitude of Head lost?π€
Ans is Hydraulic Gradient.π
Ex. For a Hydraulic Gradient of 1.5 find the head lost over a flow length of 4m.π
Solution:
Loss over 1m= Hydraulic Gradientπ€©
Loss over 4m=Xπ€©
Cross multiplication will give ,
1ΓX=4Γi
So X=4Γ1.5=6.0mπ
#soil
@macedhule
π12π₯1
π₯ Geotech:
STABILITY OF SLOPES -
β FORCES CAUSING FAILURE OF SLOPES -
1. Gravitational force
2. Seepage force
3. Earthquake force
4. Construction equipment loads
β TYPES OF SLOPE FAILURES -
1. Translational failure
2. Rotational failure
3. Wedge failure
4. Compound failure
β TYPES OF SLOPES -
β Infinite slopes - natural slope
- translational failure
- e.g mountain
β Finite slopes- artificial slope
- rotational failure
- e.g embankment of
road
#soil
Join @macedhule
STABILITY OF SLOPES -
β FORCES CAUSING FAILURE OF SLOPES -
1. Gravitational force
2. Seepage force
3. Earthquake force
4. Construction equipment loads
β TYPES OF SLOPE FAILURES -
1. Translational failure
2. Rotational failure
3. Wedge failure
4. Compound failure
β TYPES OF SLOPES -
β Infinite slopes - natural slope
- translational failure
- e.g mountain
β Finite slopes- artificial slope
- rotational failure
- e.g embankment of
road
#soil
Join @macedhule
β€11