project class

Conducted by: Offered to :

Riyadh, Saudi Arabia, 2019-2020

Dr. Mohamed Ezzat Assistant professor of Civil Eng.

Department of Engineering Management

College of Engineering.

Prince Sultan University

Undergraduate Students –Senior Level.

Engineering Management Department.

College of Engineering.

Prince Sultan University

2nd semester- Year 2019-2020.

EM 306 : Soil Mechanics and Foundations

Construction Management Program (CMP)

Consolidation Rate

Topic No. 8.2

Topic (8)

 Page :1 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

TENTATIVE WEEKLY COURSE SCHEDULE WEEK UNIT/ TOPIC

Number of Contact

hours

1 Introduction 5

2 Soil Formation 5

3 Engineering Properties of Soil 5

4 Soil Exploration 5

5 Soil Compaction 5

6 Water in Soil 5

7 Stress in soils 5

8-9 Consolidation of soil 5

10-11 Shear Strength of soil 10

12-13 Bearing Capacity and Shallow Foundations 10

14 Deep Foundations 5

15 Lateral Earth Pressure & Retaining Structures As Scheduled

 Consolidation Rate Topic No. 8

CONSOLIDATION RATE

 Page :2 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

ONE-DIMENSIONAL CONSOLIDATION

Drainage and Deformations

occur in Vertical direction only.

(none laterally)

A reasonable simplification for

solving consolidation problems

 Page :3 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

TERZAGHI SPRING ANALOGY When water drains from the soil pores, the load is gradually shifted from water to soil particles. For

fully saturated soils, the load transfer is accompanied by a volume change equal to the volume of

drained water. This process is known as CONSOLIDATION.

 Page :4 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

 Page :5 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

• Magnitude of settlement → compression index (Cc)

• Rate of consolidation → co-efficient of consolidation (Cv)

CONSOLIDATION TEST

INTERPRETATION OF TEST RESULTS

1. Time ~ Deformation curve

i. Cv (Coefficient of consolidation)

2. Pressure ~ Deformation curves

i. Cc (Compression index)

ii. Cr (Recompression index)

iii. aV (Coefficient of compressibility)

iv. mV (Coefficient of volume change)

 Page :6 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

USEFUL DEFINITIONS

Degree of consolidation (U):

It's the ratio of the vertical settlement of the clay layer at time t to its final settlement.

FACTORS AFFECTING THE DEGREE OF CONSOLIDATION: 1- Time.

2- Drainage path.

3- Soil permeability.

4- Soil compressibility.

 Page :7 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

Coefficient of consolidation (Cv):

USEFUL DEFINITIONS

It's a coefficient that depends on soil compressibility and permeability

FACTORS AFFECTING COEFFICIENT OF CONSOLIDATION: 1- Soil permeability.

2- Soil compressibility.

Drainage path (HD):

It's the longest distance

that water will path

through to leave the clay

layer.

 Page :8 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

Time factor (Tv):

USEFUL DEFINITIONS

U 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Tv 0.008 0.031 0.071 0.126 0.197 0.287 0.403 0.567 0.848

For U = 50% Tv = 0.197

For U = 90% Tv = 0.848

 Page :9 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

DEFORMATION - TIME PLOT

Used to determine Cv (coefficient of

consolidation)

Rate of consolidation (U)

Consolidation Time (t)

Time-Deformation relationship

Methods of Determining Cv : 1. Casagrande’s log-time method (1938)

2. Taylor’s Square root of time method (1948)

 Page :10 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

Example 2 For the soil stratification shown in figure and considering the illustrated

loading condition, determine the following:

i. Final settlement under the footing.

ii. The settlement after 5 years.

iii. The time for 80% consolidation.

G.W.T

1.5 m

1150 kN

SAND

γd = 18.9 kN/m 3

3 * 4 m

CLAY

γsat = 20 kN/m 3 mv = 6.2 * 10

-4 m2/kN k = 8.9 * 10-9 cm/sec

 Consolidation Rate Topic No. 8

 Page :11 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

Solution:

i- Final settlement of the footing:

∆σ = 𝟏𝟏𝟓𝟎

𝟔∗𝟕 = 27.4 kN/2

∆H = mv . ∆σ . H

= 6.2 * 10-4 * 27.4 * 6 = 0.102 m

= 10.2 cm (Final settlement)

G.W.T

1.5 m

1150 kN

SAND

γd = 18.9 kN/m 3

3 * 4 m

CLAY

γsat = 20 kN/m 3 mv = 6.2 * 10

-4 m2/kN k = 8.9 * 10-9 cm/sec

 Consolidation Rate Topic No. 8

 Page :12 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

ii- The settlement after 5 years:

cv = 𝒌

𝒎𝒗 . γ𝒘 =

𝟖.𝟗 ∗ 𝟏𝟎−𝟏𝟏

𝟔.𝟐 ∗ 𝟏𝟎−𝟒 ∗𝟏𝟎 = 1.44 * 10-8 m2/sec

T = 𝒄𝒗.𝒕

(𝑯𝒅) 𝟐 =

𝟏.𝟒𝟒 ∗ 𝟏𝟎−𝟖 ∗𝟓 ∗𝟐𝟒 ∗𝟔𝟎 ∗𝟔𝟎 ∗𝟑𝟔𝟓

(𝟔)𝟐 = 0.063

A. Determine Consolidation Coefficient (cv):

b. Time Factor (T):

→ U = 0.28 from chart

∆H5 years = U * ∆Hf = 0.28 * 10.2 = 2.9 cm

c. Settlement after 5 years :

 Consolidation Rate Topic No. 8

 Page :13 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

Solution:

iii- Time for 80% settlement:

For 80% cons. T 0.567 (from table)

→ 0.567 = 𝟏.𝟒𝟒 ∗ 𝟏𝟎−𝟖 ∗ 𝒕𝟖𝟎%

(𝟔)𝟐

→ t80% = 1.42 * 10 9 sec = 45 years

U 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Tv 0.008 0.031 0.071 0.126 0.197 0.287 0.403 0.567 0.848

 Consolidation Rate Topic No. 8

 Page :14 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Secondary compression settlement can be computed from

SETTLEMENT OF LOADS ON CLAY DUE TO SECONDARY COMPRESSION

Ss = Cα H log 𝒕𝒔

𝒕𝒑 eqn 7.25

Ss = secondary compression settlement

Cα = coefficient of secondary compression

H = initial thickness of clay layer

ts = life of the structure (or time for which

settlement is required)

tp = time to completion of primary consolidation

 Page :15 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

A foundation is built on a sand deposit underlain by a highly compressible

clay layer 5.0 m thick. The clay layer’s natural water content is 80%. Primary

consolidation is estimated to be complete in 10 years. Determine the

secondary compression settlement expected to occur from 10 to 50 years

after construction of the foundation

Example 7

 Page :16 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

From eqn 7.25,

Ss = Cα H log 𝒕𝒔

𝒕𝒑

From Fig 7.22, with w = 80%

Cα = 0.015

H = 5.0 m

ts = 50 years

tp = 10 years

Ss = (0.015) (5.0 m) (log 𝟓𝟎 𝒚𝒆𝒂𝒓𝒔

𝟏𝟎 𝒚𝒆𝒂𝒓𝒔 )

Ss = 0.052 m

Solution:

 Page :17 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

 Consolidation Rate Topic No. 8

RECIPE FOR SUCCESS,

As long as you live, Just Keep

L e a r n i n g …

References

 Page :18 Dr. Eng. Mohamed Ezzat EM306: Soil Mechanics and Foundations

• Das, B., M. (2014), “ Principles of geotechnical Engineering ” Eighth Edition, CENGAGE Learning, ISBN-

13: 978-1-133-10867-2.

• Knappett, J. A. and Craig R. F. (2012), “ Craig’s Soil Mechanics” Eighth Edition, Spon Press, ISBN: 978-0-

415-56125-9.

• Orabi, A. (2015),Soil Mechanics, “Introduction &Properties of Soil lecture notes”, International university of

sciences and technology.

• Terzaghi, K. (1936) "Stress Distribution in Dry and in Saturated Sand Above a Yielding Trap-Door",

Proceedings. First International Conference on Soil Mechanics and Foundation Engineering, Cambridge,

Massachusetts, pp. 307-311.

• Terzaghi, K. (1943). “Theoretical Soil Mechanics”. John Wiley & Sons, New York.

• Meyerhof, G. G. (1951). “The Bearing Capacity of Foundations”. In Géotechnique, vol. 2, no. 4, pp. 301-

332.

• Radwan, A. (2013), “fundamentals of Soil Mechanics”. Helwan university, Faculty of engineering. Civil

Department library.

• El-Kadi, F. (2002), “Principles of Soil Mechanics”. Ain shams university, Faculty of engineering. Civil

Department library.

• Vesic, A. S. (1975). Principle of pile foundation design. Soil Mechanics Series No 38, School of

Engineering, Duke University.

• Joseph E. Bowels, (1999), "Physical and Geotechnical Properties of Soils"; McGraw Hill Book.

 Consolidation Rate Topic No. 8

• Presentation of the theories and principles of soil mechanics

and foundation engineering.

• Explore the equipment's and instrumentations used for in-situ

and laboratory testing of soil.

• Outline the design standards of different types of foundation,

soil support systems according to several international codes.

• Provide sufficient field case studies and solved examples so that

students can make judgements as to the credibility of results

that they may obtain, or review, in the future.

Soil is a complex multiphase material. A sound understanding of

the fundamental principles and design applications of soil

mechanics is needed to predict the behavior and performance of

soil as a construction material or as a supporting medium for

engineering structures.

The main objective of this course is to provide the undergraduate

student with an insight into the theories and principles of soil

mechanics and foundation engineering, and its applications in

practical problems. The methodology that will be followed in this

course to achieve its objectives are directed towards the following

points:

Preface

Course Instructor

Dr. Mohamed Ezzat Al-Atroush

Dr. Mohamed Ezzat obtained his Ph.D. Degree from Ain Shams University, Egypt, in 2018. He joined the Prince Sultan University (PSU) in 2019 as an Assistant Professor in the area of Civil Engineering. He has broad experience in the field of geotechnical engineering on academic and professional works. Also, he has published many international journal and conference publications in the area of Geotechnical Engineering. He is a member of several international technical committees, such as the American society ofcivil engineers (ASCE).

On the other hand, Dr. Ezzat participated in many consultancy projects involving site investigations, problematic soils, evaluation of stability of slopes and escarpments, construction and permanent dewatering, design of deep excavation support, traditional and specialized lab testing, field monitoring, geophysical studies, foundation and bridge design, effect of tunnel induced ground deformations on adjacent surface and underground structures. His main research interests are in the Large Diameter bored piles, tunneling and deep excavations, Dynamic soil-structure interaction, Ground Improvement, and Energy and Sustainable Geotechnics.

Prince Sultan University, Riyadh, Saudi Arabia, 2019-2020