Gte-i 5r425q

GUDLAVALLERU ENGINEERING COLLEGE (An Autonomous Institute with Permanent Affiliation to JNTUK, Kakinada) Seshadri Rao Knowledge Village, Gudlavalleru – 521 356.

Department of Civil Engineering

HANDOUT on

GEOTECNICAL ENGINEERING-I

GEOTECHNICAL ENGINEERING-I Class & Sem. : II B.Tech – II Semester

Year : 2017-18

Branch

Credits : 3

: CE

=================================================================== 1. Brief History and Scope of the Subject In our curriculum, the subject “Geo-Technical Engineering-I” is offered at II B.Tech II-Semester level. Soil engineering is an applied science dealing with the applications of principles of soil mechanics to practical problems. It has a much wider scope than soil mechanics, as it deals with all engineering problems related with soils. It includes site investigations, design and construction of foundations, earth-retaining structures and earth structures. Geotechnical engineering is a broader term which includes soil engineering, rock mechanics and geology. The Field of Soil Mechanics is very vast. The Civil Engineering has many diverse and important encounters with soil. Apart from testing and classification of various types of soils in order to know its physical properties, the knowledge of soil mechanics is particularly helpful in the design of foundations, rigid and flexible pavements, underground and earth retaining structures, embankments and excavations and earth dams. 2. Pre-Requisites  Engineering Geology and GIS Applications 3. Course Objectives:  To understand different classification of natural soils.  To learn Consolidation settlement and compaction control.  To study the shear strength parameters. 4. Course Outcomes: After completion of the course, the student will be able to  Classify the natural soils as per different standards.  Calculate consolidation settlement for cohesion soils.  Apply methods of compaction in field.  Determine shear strength parameters of soils.  Explain the seepage analysis of soils. 5. Mapping of Course Outcomes with Program Outcomes:

Pos Co1 Co2 Co3 Co4 Co5

1

2

L

M

3

4

5

H M

7

8

H M

H

6

L

L M

M H

9 10 11 12 PSOs 1 2 3 4 Co1 L H H Co2 L Co3 M L Co4 L H L Co5 L

6. Prescribed Text Books 1. Soil Mechanics and Foundation Engg.By K.R. Arora, Standard Publishers and Distributors, Delhi. 2. Geotechnical Engineering by Manoj Dutta & Gulati S.K – Tata Mc.Grawhill Publishers New Delhi. 3. Geotechnical Engineering Principles and practices of soil mechanics and foundation engineering by VNS Murthy – CRC Press 7. Reference Text Books 1. Geotechnical Engineering by C. Venkataramiah, ew age International Pvt .Ltd, ( 2002). 2. Soil Mechanics – T.W. Lambe and Whitman, Mc-Graw Hill Publishing Company, Newyork. 3. Basic and Applied Soil Mechanics by Gopal Ranjan& ASR Rao, New age International Pvt. Ltd, New Delhi BOOKS AVAILABLE IN LIBRARY: 1. Soil Mechanics and Foundation Engineering by K.R.Arora, Standard Publishers and Distributors, Delhi.Soil Mechanics and Foundation by B.C.Punmia, LAXMI Publications 2. Soil Mechanics and Foundation Engineering by P.N Modi, Standard book house Publications 3. Geotechnical Engineering (Soil Mechanics) by T.N Ramamurthy, S.CHAND Publications 4. Soil Mechanics and Foundation Engineering by V.N.S Murthy, CBS press 5. Soil Mechanics and Foundation Engineering by Kalita, Utsav Chandra, PHI Publications 6. Geotechnical Engineering by Manoj Dutta & Gulati.SK. Tata Mc-Grawhill Publications 7. Geotechnical Engineering Principles and practices of Soil Mechanics and Foundation Engineering V.N.S Murthy, CBS press 8. Geotechnical Engineering by Venkataramiah, New age International Pvt Ltd 9. Soil Mechanics by T.W Lambe and Whitman, Mc-Grawhill Publishing Company 10. Basic and Applied soil mechanics by Gopal Ranjan&ASR RAO, New age International Pvt Ltd 11. Foundation Analysis and Design by Bowles, Mc Grawhill Publishing Company 12. Craig's Soil Mechanics by Craig, R.F, Taylor & Francis Publications 13. Problem solving in soil mechanics by Aysen. A, Taylor & Francis Publications 14. Guide to Soil Mechanics by Bolton, Malcolm D. University Press 8. URLs for E-Learning Resources 1. http://nptel.ac.in/courses/105106142/ 2. http://nptel.ac.in/courses/105104137/ 3. http://nptel.ac.in/courses/105101083/

9. 1. 2. 3. 4.

Digital Learning Materials: http://nptel.ac.in/courses/105105039/ http://nptel.ac.in/courses/105101084/50 http://nptel.ac.in/courses/105101084/55 http://nptel.ac.in/courses/105107120/

10. Lecture Schedule / Lesson Plan No. of Periods Theory Tutorial CLT Soil Formation, Soil Structure 2 1 Clay Mineralogy, Adsorbed Water 1 Mass-Volume relationships 2 1 Relative Density, Grain Size Analysis 1 2 Consistency Limits 1 SoilClassification 1 UNIT-II PERMEABILITY AND SEEPAGE THROUGH SOILS Capillary Rise, Flow of water through soils 1 1 Darcy’s Law, Factors affecting Permeability 1 laboratory determination of coefficient of permeability 2 1 Total, Neutral and effective stress 2 1 Quick Sand Condition 1 1 Seepage through soils 1 UNIT-III STRESS DISTRIBUTION IN SOILS Geostatic stresses 1 1 Boussinesq’s and Westergaard’s theories for point load 2 Boussinesq’s and Westergaard’s theories for line load 1 Boussinesq’s and Westergaard’s theories for circular load 1 1 1 Boussinesq’s and Westergaard’s theories for rectangular load 1 Newmark’s Influence chart 1 UNIT –IV COMPACTION Mechanism of compaction 1 1 Factors affecting Compaction 2 1 Effects of compaction on soil properties 2 1 Methods of compaction used in field 2 UNIT –V CONSOLIDATION Spring Analogy mechanism 1 1 Terzaghi’s theory of one dimensional consolidation 1 1 Over consolidated and normally consolidated clay 1 1 Determination of void ratio at various load increments 2 Determination of coefficient of consolidation 1 1 Pre consolidation pressure 1 UNIT –VI SHEAR STRENGTH OF SOILS Basic mechanism of shear strength 1 1 1 Mohr Coulomb Failure theories 2 Liquefaction 2 1 Shear strength determination under various drainage conditions 2 Total No.of Periods: 45 15 6 UNIT-I INTRODUCTION

UNIT-I Assignment-Cum-Tutorial Questions A. Questions testing the ing / understanding level of students I) Objective Questions 1. Soil deposits by wind are known as _______________deposits. 2. When clay particle settles in water, deposits formed have a __________ structure. 3. Formula to calculate terminal velocity of sinking particles is _________ 4. The apparatus to calculate liquid limit of soils is known as _________ 5. Deposits made in lakes are called as __________ deposits. 6. Honeycomb structure usually develops when the particle is from _____mm to

_____mm. 7. A tetrahedral unit consists ______ no. of oxygen atoms 8. The soil containing large amount of montmorillonite exhibits _______ and

___________. 9. Hydrometer works based on _______law. 10. The unified soil classification system classifies the soil into ______ types.

II) Descriptive Questions 1. Define plastic limit and explain the test procedure for liquid limit and plastic limt. 2. Define plasticity index. 3. What do you mean by flow index? 4. What are the types of corrections in hydrometer? 5. What is coefficient of uniformity and coefficient of curvature? 6. What do you mean by shrinkage limit? 7. What is absorbed water? 8. What is thixotropy? 9. What is the formula to determine relative density of soil?

B. Question testing the ability of students in applying the concepts. I) Multiple Choice Questions: 1. Talus is the soil transported by a) gravitational force

b) water

[ ] c) glacier

d)wind

2. In a liquid limit test, the moisture content at 10 blows was 70% and that at 100 blows was 20%. The liquid limit of the soil is a) 35%

b) 50%

c) 65%

d) None of the above

3. A compacted soil sample using 10% moisture content has a weight of 200 g and mass unit weight of 2.0 g/cm3. If the specific gravity of soil particles and water are 2.7 and 1.0, the degree of saturation of the soil is a) 11.1%

b) 55.6%

c) 66%

d) none of the above

4. Degree of saturation of a natural soil deposit having water content 15%, specific gravity 2.50 and void ratio 0.5 is a) 50%

b) 60%

c) 75%

d) 80%

5. Stokes’ law states that the velocity at which a grain settles out of suspension, the other factors remaining constant, is dependent upon a) Shape of grain

b) weight of grain

c) size of grain

d) all the above

6. If the specific gravity of a soil particle of 0.05 cm diameter is 2.67, its terminal velocity while settling in distilled water of viscosity, 0.01 poise, is a) 0.2200 cm/sec b) 0.2225 cm/sec c) 0.2250 cm/sec d) 0.2275 cm/sec e) 0.2300 cm/sec 7. If dry density, water density and specific gravity of solids of a given soil sample are 1.6 g/cc, 1.84 g/cc and 2.56 respectively, the porosity of the soil sample, is a) 0.375

b) 0.370

c) 0.380

d)0.390

II) Descriptive & Problems: 1. The mass of chunk of moist soil is 20kg and its volume is 0.011m3. after drying in an oven, the mass reduces to 16.5kg. Determine the water content, the density of moist soil, the dry density, void ratio, porosity, and the degree of saturation. Take G=2.70 2. A soil specimen has a water content of 10% and a wet unit weight of 20kN/m3. If the specific gravity of solids is 2.70, determine the dry unit weight, void ratio, and the degree of saturation. Take 𝛾𝑤 = 10𝑘𝑁/𝑚3 3. A moist soil sample weighs 3.52N. After drying in an oven, its weight is reduced to 2.9N. The specific gravity of solids and the mass specific gravity are respectively 2.65 and 1.85. Determine the water content, void ratio, porosity, and the degree of saturation. Take 𝛾𝑤 = 10𝑘𝑁/𝑚3 4. A sample of saturated soil has a water content of 25 percent and a bulk unit weight of 20 kN/m3. Determine dry density, void ratio, and specific gravity of solid particles.

5. A Sample of clay was coated with paraffin wax and its mass, including the mass of wax, was found to be 697.5 gm. The sample was immersed in water and the volume of the water displaced was found to be 355ml. The mass of the sample without wax was 690.0 gm, the water content of the representative specimen was 18%. Determine the bulk density, dry density, void ratio and the degree of saturation. The specific gravity of the soilds was 2.70 and that of the was 0.89. 6. In a compaction test on a soil, the mass of the wet soil when compared in the mould was 1.855kg. The water content of the soil was 16%. If the volume of the mould was 0.945 litres, determine the dry density, void ratio, degree of saturation, and percentage air voids. Take G=2.68 7. There are two borrow areas A and B which have soils with void ratios of 0.80 and 0.70 respectively. The inplace water content is 20% and 15% respectively. The fill at the end of the construction will have a total volume of 10000m3, bulk density of 2Mg/m3 and a placement water content of 22%. Determine the volume of the soil required to be excavated from both areas. G=2.65. If the cost of excavation of soil and transportation is Rs.200/- per 100m3 for area A and Rs. 220/- per 100m3 for area B, which of the borrow area is more economical? 8. Classify the soils A and B, with the properties as shown below, according to USC system Soil

WL, %

I P, %

A

45

29

No.4 ing 4.75mm 100

B

55

15

100

Sieve No.200 ing 75microns 59 85

9. Classify the soil with the following properties according to ISC system WL, %

WP, %

40

10

% ing % ing 4.75mm 75microns 60 45

UNIT-II Assignment-Cum-Tutorial Questions A. Questions testing the ing / understanding level of students I) Objective Questions 1. With the rise of temperature, the permeability a) Increases

b) decreases

c) remains constant

d)None

%

2. For large Engineering projects, the permeability is determined accurately by a) Constant head test

b) Variable head test c) Pumping in d) Pumping out test

3. In a Darcian flow, the flow velocity is a) Actual velocity b) Seepage velocity c) Discharge Velocity d) Boundary velocity 4. In granular soil, K varies….. with the specific surface. Choose the correct statement. a) Directly

b) Inversely

c) Logarithmically

d) Not in order

5. Effective stress is the stress a) Transmitted by flowing water b) Transmitted from particle to particle through points of c) That can be measured

d) None of the above

6. The pressure that affects shear strength and permeability of soil is a) Total pressure

b) Neutral Pressure

c) Effective pressure d) None of above

7. The relation between total pressure’𝜎’ and effective pressure’𝜎′’ and pore pressure ‘u’ is a) 𝜎 ′ = 𝜎 + 𝑢

b) 𝜎 ′ = 𝜎 − 𝑢

c) 𝜎 = 𝜎 ′ − 𝑢

d) None of above

8. Space between two adjacent flow lines is called a) Flow potential

b) flow path

c) Flow field

d) Flow length

9. Quantity of seepage in each flow channel of a flow net is a) Dependent of size of field

b) Dependent of potential drop

c) Same

d) Dependent on the number of flow channels

10. Identify the incorrect flow net property a) Flow lines and equipotential lines intersect or meet orthogonally b) Quantity of water flowing through each channel is the same c) Potential drop between any two successive equipotential lines is different d) Flow lines and equipotential lines are smooth curves

II) Descriptive Questions 1. What are the different categories of the soil water? Describe in brief. 2. Discuss the phenomenon of capillary rise in soils. What are the factors that effect the height of capillary zone? 3. What is Darcy’s Law? What are the limitations? 4. What are the different methods for determination of coefficient of permeability in laboratory? Discuss their limitations. 5. How would you determine the average permeability of a soil deposit consisting of a number of layers incase of parallel and perpendicular flow?

6. What is flow net? Describe its properties and applications and also explain the uses also. 7. Define total stress, neutral and effective stress. What is the importance of the effective stress? 8. What is quick sand? How would you calculate the hydraulic gradient required to create quick sand conditions in a sample of sand? 9. Prove that effective stress for a saturated soil can be expressed as 𝜎 ′ = 𝜎 − 𝑢

B. Questions testing the ability of students in applying the concepts. I) Multiple Choice Questions: 1. The shape factor of a flow net is given as a) Nd/Nf

b) (Nd-1)/Nf

c) Nf/Nd

d) (Nf-1)/Nd

2. In a flow net there are 4 flow channels and 15 equipotential drops, estimate the quantity of seepage if the head loss is 3m and k=2 x 10-5 m/sec a) 3.8 x 10-4 m3/sec

b) 1.6 x 10-5m3/sec

c) 22.5 x 10-5m3/sec d) 4.8 x 10-5m3/sec

3. The coefficient of permeability of a soil is 4 x 10-5 cm/sec for a certain pore fluid. If the viscosity of the pore fluid is reduced to half, then the coefficient of permeability will be a) 8 x 10-5 cm/sec

b) 2 x 10-5 cm/sec

c) 16 x 10-5 cm/sec

d) 4 x 10-5 cm/sec

4. The depth of water in a swimming pool is 6m. The effective and total pressure at a depth of 3m below top surface of water in kN/m2 are a) 0 and 0

b) 30 and 0

c) 0 and 30

d) 0 and 3

5. The approximate depth at which effective vertical pressure is equal to 100kN/m2 in a typical deposit of submerged soil of saturated unit weight of 20kN/m3 is a) 5m

II)

b) 10m

c) 15m

d) 20m

Descriptive Questions:

1. In a constant head permeameter test, the following observations were taken. Distance between piezometer tappings = 100mm Difference of water levels in piezometers = 60mm Diameter of the test sample = 100mm Quantity of water collected = 350ml Duration of the test = 270 sec Determine the coefficient of permeability of the soil. 2. The falling head permeability test was conducted on a soil sample of 4 cm diameter and 18cm length. The head fell from 1.0m to 0.40m in 20 minutes. If the cross sectional area of the stand pipe was 1cm2, determine the coefficient of permeability.

3. Figure 1 shows an aquifer inclined at 100 to the horizontal. The difference of water levels in new observations wells at the horizontal distance of 60m is 5m. Determine the discharge through the aquifer per unit width if k=0.7mm/sec. The depth of aquifer normal to the direction of flow is 2.951m

4. A sand deposit is 10m thick and overlies a bed of soft clay. The ground water table is 3m below the ground surface. If the sand above the ground water table has a degree of saturation of 45%, plot the diagram showing the variation of the total stress, pore Water pressure and the effective stress. The void ratio of the sand is 0.70. take G=2.65. 5. A soil profile consists of a surface layer of clay 4m thick (𝛾=19.5 kN/m3) and a sand layer 2m thick (𝛾=18.5kN/m3) over lying an impermeable rock. The water table is at the ground surface. If the water level in a standpipe driven into the sand layer rises 2m above the ground surface. Draw the plot showing the variation of total stress, pore Water pressure and the effective stress and determine the increase in effective stress at the top of rock when the artesian head in the sand is reduced by 1m. 6. A soil profile consists of a surface layer of sand 3.5m thick (𝜌=1.65Mg/m3), an intermediate layer of clay 3m thick (𝜌=1.95Mg/m3) and the bottom layer of gravel 3,5m thick (𝜌=1.925Mg/m3). The water table is at the upper surface of the clay layer. Determine the effective pressure at various levels immediately after placement of a surcharge load of 58.86kN/m2 to the ground surface. 7. A sand deposit consists of two layers. The top layer is 2.5m thick (𝜌 =1709.67kg/m3) and the bottom layer is 3.5m thick (𝜌𝑠𝑎𝑡 =2064.52 kg/m3). The water table is at a depth of 3.5m from the surface and the zone of the capillary saturation is 1m above the water table. Draw the diagrams showing the variation of total stress, neutral stress and effective stress.

GATE/ Competitive oriented bits

1. A stratum of soil consists of three layers of equal thickness. The permeabilities of top and bottom layers are 1 x 10-4 cm/sec and that of middle layer is 1 x 10-3 cm/sec. Determine the value of the horizontal coefficient of permeability for the entire soil layer. 2. In a falling head permeability test on a sample 12.2cm high and 44.41cm 2 in cross sectional area, the water level in a standpipe of 6.25mm internal diameter dropped from a height of 75cm to 24.7cm in 15 min. find the coefficient of permeability. 3. Determine the effective stress at depth of 10m below ground level, when the water level is 3m below ground level, saturated density is 20kN/m3 and bulk density is 18kN/m3. 4. A soil profile consists of a surface layer of sand between plane AA and BB of 4m thick (𝛾=1.6t/m3), an intermediate layer of clay between BB and CC of 3.5m thick (𝛾=1.9t/m3) and the bottom layer of gravel below CC of 4m thick (𝛾=1.925t/m3). The water table is at the upper surface of the clay layer. Determine the effective stress at plane CC and Effective stress at the plane DD. 5. A soil profile consists of a surface layer of clay 4m thick (𝛾=19.5 kN/m3) and a sand layer 2m thick (𝛾=18.5kN/m3) over lying an impermeable rock. The water table is at the ground surface. If the water level in a standpipe driven into the sand layer rises 2m above the ground surface. Determine the effective stress at a depth of 6m and also the increase in effective stress at the top of rock when the artesian head in the sand is reduced by 1m.

UNIT-III Assignment-Cum-Tutorial Questions A. Questions testing the ing / understanding level of students I)

Objective Questions

1. An isobar is a curve which s all the points of a) s point of equal horizontal stress b) s point of equal vertical stress c) s point of zero horizontal stress d) s point of Maximum horizontal stress 2. Newmark’s influence chart can be used for the determination of vertical stress under a) Circular load area only

b) Rectangular loaded area only

c) Strip load only

d) any shape of loaded area

3) The Westergaard’s analysis is used for a) Homogenous soil

b) Cohesive soils

c) Sandy soils

d) Stratified soils

4) The stresses due to self weight of soil are known as a) Geostatic stresses

b) Effective stresses

c) Pore water stresses

d) Neutral stresses

5) Which of the following is an assumption for Boussinesq’s theory? a) Soil is isotropic

b) Soil is homogenous

c) Soil is elastic

d) All the above

6) The vertical cross section of an isobar is

II)

a) Parabolic

b) Circular

c) Lemniscates

d) None

Descriptive Questions

1. Define Geostatic stresses? 2. Derive an expression for the vertical stress at a point due to a point load using Boussinesq’s theory. 3. Derive an expression for vertical stress at a point due to a line load. 4. Derive an expression for vertical stress at a point due to a rectangular load. 5. What is Newmark’s influence chart? 6. Derive Westergaard’s equation for the determination of vertical stress at a point. B. Question testing the ability of students in applying the concepts. I) Multiple Choice Questions: 1. A load of 2000kN is uniformly distributed over an area of 3mx2m. The average vertical stress at a depth of 2m using 2:1 distribution is a) 160kN/m2

b) 100 kN/m2

c) 48kN/m2

d) 37 kN/m2

2. A concentrated load of 1000kN vertically at a point on the soil surface. According to the Boussinesq’s equation the ratio of vertical stresses at depths of 3m and 5m is a) 0.35

b) 0.7

c) 1.75

d) 2.78

3. A Newmark's chart has an influence coefficient of 0.005. a rectangular footing area covers 6 sectors when centrally, loaded on Newmark's chart. If the footing is 40t/m2 . The stress at the center of the footing is a) 0.30 t/m2

b) 0.20 t/m2

c) 1.2 t/m2

d) 1 t/m2

4. The intensity of radial shear stress at a point 4m directly below a 2tonne point load is a) 0.16 t/m2

b) 0.125 t/m2

c) 0

d) 1 t/m2

5. In the construction of Newmark’s influence chart, if the number of annual areas selected is 10 and each annular area is divided into 10 sectors. The influence value of the chart is a) 0.005

b) 0.05

c) 0.01

d) 0.001

6. On a circular loaded area of 2m diameter, the load intensity be 100kN/m2 . the vertical stress in soil at a depth of 1m below the center of the loaded area will be a) 45.6kN/m2

b) 50 kN/m2

c) 64.65kN/m2

d) 7.07kN/m2

II)

Problems:

1.

A concentrated load of 200kN is applied at the ground surface. Determine the vertical stress at a point P which is 6m directly below the load. Also calculate the vertical stress at point r which is at a depth of 6m but at a horizontal distance of 5m form axis of load.

2.

There is a line load of 120kN/m acting on the ground surface along y-axis. Determine the vertical stress at a point P which has x and z coordinates as 2m and 3.5m respectively.

3.

Determine the vertical stress at appoint P which is 3m below and at a radial distance of 3m from the vertical load of 100kN. Use Westergaard’s solution.

4.

Calculate the vertical stress at a point P at a depth of 2.5m directly under the center of the circular area of radius 2m and subjected to a load 100kN/m2.

5.

A rectangular loaded area 2mx 2.5m carries a load of 80kN/m2. Determine the vertical stress at point P located outside the loaded area at a depth of 2.5m.

6.

A rectangular foundation 3mx2.1m perfectly flexible and carries the load of 400kN/m2.Determine the vertical pressure at a depth of below a point P.

UNIT-IV Assignment-Cum-Tutorial Questions A. Questions testing the ing / understanding level of students I) Objective Questions 1. For a standard proctor test, the mass of hammer and the drop of hammer are ___________. 2. The line of optimum generally corresponds to _____________ percentage air voids. 3. Pneumatic tired rollers are useful for compacting _________________ soils. 4. Vibratory rollers are best suited for compacting ________________ soils. 5. Compaction of a soil is measured in of __________________. 6. Pre-compression method is useful for compacting _________________ soils. 7. OMC is the moisture content at which _________________________. 8. To avoid large swelling pressure under pavements and floors, the soils is compacted at _______________ of optimum.

II) Descriptive Questions 1. Differentiate between consolidation and compaction. 2. Describe standard penetration test and the modified proctor test. How would you decide the type of the test to be conducted in the laboratory? 3. What is the compaction curve? Give its salient features. What is a zero air voids line? 4. What are the factors affecting compaction? Discuss in brief. 5. What is the effect of compaction on engineering properties of soil? 6. What are the different methods of compaction adopted in field?

B. Questions testing the ability of students in applying the concepts.

I) Multiple Choice Questions: 1. Identify the factor which is same for both Standard and Modified Proctor compaction tests. a) Height of the hammer drop

b) Number of drops per layer

c) Number of layers

d) Weight of hammer

2. Identify the term which is common for both consolidation and compaction. a) Removal of air

b) Long term process

c) Densification of soils

d) Applicability of saturated soils

3. Zero air voids line is the line ing dry densities corresponding to a) Zero Air content

b) Zero degree of saturation

c) Zero porosity

d) Zero void ratio

4. Identify the wrong statement a) During compaction soil always remains partially saturated b) Increase in Compactive effort results in an increase in MDD and decrease in OMC c) Relative compaction and relative density are one and the same d) The permeability of soil compacted on the dry side of optimum is more than that compacted on wet side of optimum. 5. In a compaction test, with increase in compactive effort a) Maximum dry density increases but OMC decreases b) The compaction curve is shifted to the left and higher c) Both the above d) Both MDD and OMC increases 6. The following soil has higher OMC a) Gravel

b) Sand

c) Silt

d) Clay

7. Clay particles on the wet side of optimum moisture content exhibit a) Single grained Structure

b) Disperse Structure

c) Honeycomb Structure

d) Flocculent Structure

8. The range of OMC for the standard proctor test for clayey soils is a) 6 to 10%

II)

b) 8 to 12%

c) 12 to 15%

d) 14 to 20%

Descriptive Questions: 1. A sample of soil was prepared by mixing a quantity of dry soil with 10% by mass of water. Find the mass of wet mixture required to produce a cylindrical, compacted

specimen of 15cm diameter and 12.5cm deep and having 6% air content. Find also the void ratio and the dry density of the specimen if G=2.68. 2. The following results were obtained from a standard compaction test on a sample of soil. Water Content

0.12

0.14

0.16

0.18

0.20

0.22

Mass of soil (kg)

1.68

1.85

1.91

1.87

1.87

1.85

The volume of mould used was 950ml. Make necessary calculations and plot the compaction curve and obtain the MDD and OMC. Also calculate the void ratio, the degree of saturation and the theoretical MDD (G=2.70) 3. The maximum dry density of a sample by the light compaction test is 1.78g/ml at an optimum water content of 15%. Find the air voids and the degree of saturation. G=2.67 What would be the corresponding value of dry density on the zero air void line at OMC? 4. A cylindrical specimen of a cohesive soil of 10cm diameter and 20cm length was prepared by compaction in a mould. If the wet mass of specimen was 3.25kg and its water content was 15%, determine the dry density and the void ratio. If the specific gravity of particles was 2.70, find degree of saturation. 5. The following are the results of a standard compaction test performed on a sample of soil Water Content (%)

7.7

11.5

14.6

17.5

19.7

21.2

Mass of soil (kg)

1.7

1.89

2.03

1.99

1.96

1.92

If the volume of mould used was 950cc and the specific gravity of soil grains was 2.65, make necessary calculations and plot the water content-dry density curve and obtain the OMC and MDD.

C. GATE/ Competitive oriented bits 1. For a compacted soil with specific gravity of solids of 2.7, water content of 15%, the dry density achieved is equal to 88% of the dry density corresponding to zero air voids line. Determine the dry density of compacted soil. If the maximum dry density

of same soil in the laboratory compaction test is 1.812g/cc, find the relative compaction. 2. A cohesive soil yields a max dry density of 18g/cc at OMC of 16% during a standard proctor test. If the value of G is 2.65, what is degree of saturation, void ratio, air content, % air voids? What is the max dry density it can be further compacted to at the above OMC? 3. In a standard proctor test, 1.8kg of moist soil was filling in the mould

(Volume=944cc) after compaction. A soil sample weighing 23g was taken from the mould and oven dried for 24hr at a temperature of 1100C. Weight of dry sample was found to be 20g. Specific gravity of soil solids is G=2.7. Determine the theoretical maximum value of the dry unit weight of soil at that water content.

UNIT-V Assignment-Cum-Tutorial Questions A. Questions testing the ing / understanding level of students I) Objective Questions 1. Consolidation of a soil is due to a load which is _______________ 2. Time is an important parameter in the consolidation of ________ type of soils. 3. Primary consolidation is mainly due to expulsion of _______________ 4. If a soil has ever been subjected to a pressure in excess of its present over burden, the soil is said to be _______________________ 5. Coefficient of consolidation depends upon _______________________________. 6. The units of coefficient of consolidation are _______________. 7. The ratio of settlement at any time to the final settlement is known as ______________. 8. In consolidation testing, a curve fitting method is used to determine ______________.

II) Descriptive Questions 10. Define coefficient of compressibility, coefficient of volume change, Recompression index, compression index, Expansion index. 11. Differentiate between primary consolidation and secondary consolidation 12. Discuss the spring analogy for primary consolidation. What are its uses? 13. Differentiate between normally consolidated and the over consolidated soils. How would you determine over consolidation pressure? 14. Discuss terzaghis theory of consolidation, stating the various assumptions and their validity 15. What is the time factor? How it is related to average degree of consolidation?

16. Discuss the limitations of terzaghi’s theory of consolidation. What is theory used despite its limitations?

B. Questions testing the ability of students in applying the concepts. I) Multiple Choice Questions: 1. Secondary consolidation is mainly due to the expulsion of a) Highly Viscous Water c) Both a and b

b) Plastic Readjustment of solid particles d) None of the above

2. Time factor is a) A non dimensional parameter

b) a function of degree of

consolidation c) Directly proportional to permeability of soil d) all the above 3. Two identically clay samples of the same size designated as A and B are subjected to consolidation tests under identical conditions. Drainage takes place through one face in sample A and through both the faces in sample B. 50% consolidation of sample A occurs in 10 minutes. The time required for 50% consolidation to occur in sample B in minutes will be a) 40

b) 10

c) 5

d) 2.5

4. If coefficient of permeability is doubled and coefficient of volume compressibility is halved, the coefficient of consolidation is a) Increases by 2 times

b) decreases by 2 times

c) Decreases by 4 times

d) increases by 4 times

5. The time for 50% consolidation of a sample of d cm thick with double drainage is t hours. The time for 50% consolidation of another sample of similar soil with 3d cm thick and single drainage is a) 6t

b) t/6

c) 36t

d) 9t

6. Secondary consolidation is a) Caused by hydrodynamic lag

b) Caused by creep

c) Large for pressure below preconsolidation pressure d) small for highly plastic clays 7. A fully saturated clay specimen is subjected to a pressure of 200 kN/m2 in an consolidation test. After a period of time when the average pore pressure is 60kN/m2, the degree of consolidation is a) 60

b) 70

c) 30

d) 50

8. Which of the following is not an assumption in Terzaghi’s theory of one dimensional consolidation a) Soil mass is homogenous and isotropic b) Soil is fully saturated c) Darcy’s law is valid d) Drainage of water occurs both in vertical and horizontal directions. II)

Descriptive Questions:

1. An area is underlain by a stratum of clay layer 6m thick. The layer is doubly drained and has the coefficient of consolidation of 0.3m2/month. i) How long would it take for a surcharge load to cause a settlement of 40cm if the same load causes a final settlement of 60cm? ii) If the sand drains(S=3m and ɣw=0.30) are used, determine the time required for 90% consolidation. Take Cvr=2.0m2/month. Assume the triangular layout of drains. Neglect vertical consolidation in this case. 2. The laboratory consolidation data for an undisturbed clay sample are as follows.e1=1.00,σ1=85kN/m2,e2=0.80,σ2=465kN/m2. Determine the void ratio for a pressure σ3 of 600kN/m2 3. A consolidation test was conducted on a sample of a normally consolidated clay, with an initial void ratio of 1.55,and the following results were obtained σ (kN/m2)

80

160

320

640

1280

E

1.35

1.28

1.14

0.96

0.78

a) Plot e-log σ curve. If the initial overburden pressure is kN/m2,darw the field consolidation line and hence determine the coefficient of compression b) If the thickness of the clay layer in the field is 4m and the increase in the pressure due to loading is 50 kN/m2, compute the settlement. 4. A 3m thick layer beneath a building is overlain by is permeable stratum and is underlain by an impervious rock. The coefficient of consolidation of the clay was found to be 0.025cm2/minute. The final expected settlement for the layer is 8cm. a) How much time will take for 80% of the total settlement to take place? b) Determine the time required for a settlement of 2.5cm to occur c) Compute the settlement that would occur in one year.

GATE/ Competitive oriented bits

1. A saturated clay layer of 5cm thickness takes 1.5 years for 50% primary consolidation, when drained on both sides. Its coefficient of volume change is 1.5x10-3 m2/kN. The coefficient of permeability of soil will be a) 2.56 m/year

b) 1.53 m/year

c) 0.012m/year

d) 1.25m/year

2. During a pressure increment, a test specimen 20mm thick under double drainage attained 50% primary consolidation in 45minutes, how long will it take a 10m thick layer of same soil to reach the same degree of consolidation if the clay layer was drained on both surfaces a) 21.4 years

b) 85.6 years

c) 12.6 years d) 48.5 years

3. For question 2, if the clay is drained on the top surface only, then time required to reach the same degree of consolidation will be a) 34.35 years

b) 85.6 years

c) 62.6 years

d) none

In a laboratory test on a clay sample of thickness 25mm, drained at top only, 50% consolidation occurred in 11 minutes. Assume T50=0.197, T70=0.405 4. Find the time required for the corresponding clay layer in the field of 3m thick and drained at top and bottom to undergo 50% consolidation a) 123 days

b) 27.5 days

c) 56.5 days

d) 12 days

5. Find the time required to undergo 70% consolidation a) 153 days

b) 27.5 days

c) 56.5 days

d) 145 days

UNTI-VI Assignment-Cum-Tutorial Questions A. Questions testing the ing / understanding level of students I) Objective Questions 1. For the stability analysis of an earth dam for steady seepage case, the most appropriate test would be the ________________. 2. An undrained triaxial compression test is carried out on a saturated clay sample under a cell pressure of 100kN/m2. The sample failed at a deviator stress of 200kN/m2. The cohesion of the given sample of clay is _________________. 3. For a highly fissured clay the best method to find the shear strength is _______________. 4. The phenomenon when the sand losses its shear strength due to the oscillatory motion in saturated condition is known as ____________________.

5. With usual notations, the coulomb’s equation for shear strength under drained condition is _________________. 6. If a pure cohesive soil specimen is subjected to a vertical compressive load only, the inclination of crack to the horizontal is _______________________. 7. If the cohesion of a pure clay found in an unconfined compressive strength test 1kg/cm2 the unconfined compressive strength in kg/cm2 is __________________________. 8. The shear strength of the plastic undrained clay depends upon ____________________. 9. In an undrained triaxial compression test, the sample failed at a deviator stress of 200kN/m2

when

cell

pressure

was

100kN/m2.

The

cohesion

intercept

is

_______________.

II) Descriptive Questions 1. What are the factors that affect the shear strength parameters of soil? 2. What are the advantages of tri axial compression test? 3. What are the three standard tri axial shear tests with respect to drainage conditions? 4. What is Mohr’s strength theory for soils? Sketch typical strength envelops for clean sand. 5. Describe direct shear test? What are its merits and demerits? 6. Describe the triaxial shear test. What are the advantages of triaxial shear test over the direct shear test? 7. What is unconfined compression test? Sketch the apparatus used. What is its advantage over a Triaxial test? 8. Define slow, quick and consolidated quick Triaxial shear test, illustrating their use by at least one field example.

9. Write revised Mohr-coulomb equation. How does it differ from the original equation B. Questions testing the ability of students in applying the concepts. I) Multiple Choice Questions: 1. The strength envelope of a pure cohesive soils is a) Vertical

b) Inclined

c) Horizontal

d) Curvilinear

2. The direct shear test is ideally suited for conducting drained tests on a) Cohesive soils

b) cohesionless soils c) Any soil

d) Clayey soils

3. The failure plane in direct shear test is a) Vertical

b) Inclined

c) Horizontal

d) None

4. Unconfined compression test is generally performed on a) Sandy soils

b) Silty sand

c) Intact saturated clay

d) Fissured clay

5. The shear test that is more suitable in the field is a) Direct test

b) Triaxial shear

c) Unconfined compression d) Vane shear

6. The shear strength of a soil is a function of a) Cohesion only b) Angle of internal friction only

c) Normal stress only d) None

7. The angle of inclination of the coulomb’s failure envelope with the horizontal is called a) Angle of repose b) Angle of friction c) Angle of internal friction d) Frictional resistance 8. For a normally consolidated clay tested in a CD test, the cohesion of the clay will be a) II)

Zero

b) Maximum

c) Minimum

d) Cannot be said

Descriptive Questions:

1. A series of direct shear test was conducted on a soil, each test was carried out till the sample failed. The following results were obtained Sample No.

Normal stress(kN/m2)

Shear stress(kN/m2)

1

15

18

2

30

25

3

45

32

Determine the cohesion intercept and the angle of shearing resistance. 2. The following results were obtained from a series of consolidated undrained tests on a soil, in which the pore water pressure was not determined. Determine the cohesion intercept and the angle of shearing resistance. Sample No. 1 2 3

Confining presuure(kN/m2) 100 200 300

Deviator stress at faiure(kN/m2) 600 750 870

3. A series of consolidated-undrained (CU) Triaxial tests was conducted on overconsolidated clay and the following results were obtained. Sl No.

Cell pressure(kN/m2)

Deviator stress(kN/m2)

Pore water pressure(kN/m2)

1

125

510

-70

2

250

620

-10

3

500

850

+120

Plot the strength envelops in of total stress and effective stress, and hence determine the strength parameters. 4. The following results were obtained from a consolidated un-drained (CU) test on consolidated clay. Plot the strength envelop in of total stresses and effective stresses and determine the strength parameters

Sl No. 1 2 3

Cell pressure(kN/m2) 250 500 750

Deviator stress(kN/m2) 152 600 455

Pore water pressure(kN/m2) 120 250 350

5. The results of a CU test on a compacted soil are given below Sample No. 1 2

σ3 (kN/m2) 70 350

(σ1-σ3) (kN/m2) 230 550

U (kN/m2) -20 +90

Determine the cohesion intercept and the angle of shearing resistance in of a) total stress b) effective stresses

C. GATE/ Competitive oriented bits 1. What is the shear strength in of effective stress on a plane within a saturated soil mass at a point where the total normal stress is 295 kPa and the pore water pressure 120kPa? The effective stress shear strength parameters are C’=12kPa and ф’=300. 2. The following results were obtained in a shear box test. Determine C and ф parameters Normal stress (kg/cm2) 1.0

2.0

Shear stress (kg/cm2)

1.85

1.3

An unconfined compression test was conducted on an undisturbed sample of clay. The sample had a diameter of 37.5mm and was 80mm long. The load at failure measured by the proving ring was 28N and the axial deformation of the sample at failure was 13mm. The unconfined compressive strength is ____________________.