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This document is a chapter from a geotechnical engineering textbook, covering the basics of geotechnical engineering, including definitions, discussions, questions and answers on soil properties, and soil classification.
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P a g e | 1‐1 Chapter 1 Geotechnical Engineering – From the Beginning 1. Select the incorrect statement. (a) Soil is defined as the cemented aggregate of mineral grains and decayed organic matter (solid particles...
P a g e | 1‐1 Chapter 1 Geotechnical Engineering – From the Beginning 1. Select the incorrect statement. (a) Soil is defined as the cemented aggregate of mineral grains and decayed organic matter (solid particles) with liquid and gas in the empty spaces between the solid particles. (b) Soil is used as a construction material in various civil engineering projects. (c) Soil mechanics is the branch of science that deals with the study of the physical properties of soil and the behaviour of soil masses subjected to various types of forces. (d) Geotechnical engineering deals with the application of the principles of soil mechanics and rock mechanics to the design of foundations, retaining structures and earth structures. 2. Which one of the following problems is related to the Leaning Tower of Pisa in Italy? (a) Slope instability (b) Weakness in foundation soil (c) Structural instability (d) all of the above 3. During Classical Soil Mechanics period (1776–1856), most of the geotechnical engineering developments came from engineers and scientists in (a) England. (b) Germany. (c) Italy. (d) France. 4. N/m3 is the SI unit of (a) weight. (b) unit weight. (c) density. (d) none of the above 5. The unit of water is (a) 9.8 kN/m3. (b) 13.4 kN/m3. (c) 16.0 kN/m3. (d) 18.9 kN/m3. 6. Who was the first to use the symbol φ for soil friction angle? (a) Charles Augustin Coulomb (1736–1806) (b) Jean Victor Poncelet (1788–1867) (c) William John Macquorn Rankine (1820–1872) (d) Karl Terzaghi (1883–1963) © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 1‐2 7. Who is known as the father of modern soil mechanics? (a) Charles Augustine Coulomb (1736–1806) (b) Jean Victor Poncelet (1788–1867) (c) William John Macquorn Rankine (1820–1872) (d) Karl Terzaghi (1883–1963) 8. In 1997, the International Society of Soil Mechanics and Foundation Engineering (ISSMFE) was renamed as (a) International Society of Soil Mechanics (ISSM). (b) International Society of Geotechnical Engineering (ISGE). (c) International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE). (d) International Society of Foundation Engineering and Geotechnical Engineering (ISFEGE). 9. Ancient Greek civilization used (a) isolated pad foundation. (b) strip foundation. (c) Raft foundation. (d) all of the above 10. Which one of the following topics is not a part of geotechnical engineering? (a) Earth slopes (b) Foundations (c) Retaining Walls (d) Roof slabs © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 1‐3 Answers, Hints and Discussion 1. (a) Discussion: The incorrect statement in (a) is corrected as: Soil is defined as the uncemented aggregate of mineral grains and decayed organic matter (solid particles) with liquid and gas in the empty spaces between the solid particles. 2. (b) 3. (d) 4. (b) Discussion: Unit weight is the weight of soil per unit volume. It is explained in detail in Chapter 3 of the textbook. Students should have an idea of its typical values for soils and rocks given on Page 5 of the textbook. 5. (a) 6. (b) 7. (d) 8. (c) 9. (d) Discussion: A detailed description of these foundations is given in Chapter 16. Raft foundation is also known as mat foundation. 10. (d) Discussion: Analysis and design of roof slabs are explained in structural engineering subjects such as Structural analysis, Concrete design, Steel design, etc. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 2‐1 Chapter 2 Soil Deposits – Origin, Grain-Size, and Shape 1. Physical properties of soil depend on (a) size of soil grains. (b) shape of soil grains. (c) chemical composition of soil grains. (d) all of the above 2. Granite, gabbro and basalt are some common types of (a) minerals. (b) igneous rocks. (c) sedimentary rocks. (d) metamorphic rocks. 3. Which of the following minerals is the most resistant to weathering? (a) Olivine (b) Feldspar (c) Orthoclase (d) Quartz 4. The clay minerals are a product of chemical weathering of (a) feldspars. (b) ferromagnesians. (c) micas. (d) all of the above 5. Which of the following is not a clay mineral? (a) Biotite (b) Kaolinite (c) Illite (d) Montmorillonite 6. The soils transported and deposited by wind are called (a) alluvial soils. (b) aeolian soils. (c) lacustrine soils. (d) glacial soils. 7. At a construction site, the subsurface investigation indicates the presence of a residual soil deposit. The grain size of the soil at this site will generally (a) not vary with depth. (b) decrease with depth. (c) increase with depth. (d) increase up to some depth and then decrease. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 2‐2 8. Limestone is a (a) mineral. (b) sedimentary rock. (c) igneous rock. (d) metamorphic rock. 9. Which of the following is not a metamorphic rock? (a) Marble (b) Gneiss (c) Dolomite (d) Quartzite 10. Which of following statements does not describe the characteristics of the soil deposits formed from braided streams? (a) The grain sizes usually range from gravel to silt. (b) Clay-sized particles are generally not found. (c) The soil in a given pocket lens is generally non-uniform. (d) At any given depth, the void ratio and unit weight may vary over a wide range within a lateral distance of only a few meters. 11. The soil deposit laid down by glaciers consists of sand, silt, clay, gravel and boulders, and is usually called (a) Drift. (b) Moraines. (c) Dunes. (d) Loess. 12. Select the incorrect statement (a) Organic soils are usually found in low-lying areas where the water table is near or above the ground surface. (b) Organic soils are highly compressible. (c) The moisture content of organic soils may range from 200 to 300%. (d) Organic soil deposits are usually encountered in desert areas. 13. The particles smaller than 0.075 mm are referred to as (a) clay. (b) silt. (c) sand. (d) fines. 14. The surface area of the montmorillonite particles per unit mass is about (a) 15 m2/g. (b) 80 m2/g. (c) 800 m2/g. (d) none of the above © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 2‐3 15. Which of the following carries a net negative charge on its surfaces? (a) clay (b) silt (c) sand (d) gravel 16. When water is added to the clay, the innermost layer of double-layer water, which is held very strongly by clay, is called (a) free water. (b) adsorbed water. (c) absorbed water. (d) double-layer water. 17. For clayey and silty soils, the specific gravity of particles may vary from (a) 1.6 to 1.9. (b) 2.6 to 2.9. (c) 3.6 to 3.9. (d) none of the above 18. Hydrometer analysis for particle-size distribution curve is based on (a) Stokes’ law (b) Bernoulli’s principle. (c) Archimedes’ principle. (d) Terzaghi’s effective stress principle. 19. Particle size distribution curve is used for (a) determining the percentages of different particle-size fractions in a soil. (b) comparing different soils. (c) classifying soils. (d) all of the above 20. Effective size of soil particles denoted by (a) D10. (b) D30. (c) D60. (d) D10. 21. For a granular soil, effective size (D10) = 0.09 mm, and coefficient of uniformity (Cu) = 4.56. What will be the diameter corresponding to 60% finer? (a) 0.02 mm (b) 0.41 mm (c) 50.67 mm (d) none of the above 22. Calculation of the coefficient of gradation (Cc) of soil requires (a) D10. (b) D30. (c) D60. (d) all of the above © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 2‐4 23. A soil in which the particle sizes are distributed over a wide range is termed (a) poorly graded soil. (b) well graded soil. (c) gap graded soil. (d) granular soil. 24. Small sand particles located close to their origin are generally (a) angular. (b) subangular. (c) subrounded. (d) rounded. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 2‐5 Answers, Hints and Discussion 1. (d) 2. (b) 3. (d) 4. (d) 5. (a) 6. (b) 7. (c) 8. (b) 9. (c) 10. (c) 11. (a) 12. (d) 13. (d) Hint: See Table 2.3. 14. (c) Discussion: (a) is correct for kaolinite, and (b) for illite. 15. (a) Discussion: The negative charge on the clay particle surfaces results from both isomorphous substitution and a break in continuity of the particle structure. 16. (b) 17. (b) 18. (a) 19. (d) 20. (a) 21. (b) Discussion: Eq. (2.7): 4.56 0.09 0.41 mm © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 2‐6 22. (d) Hint: See Eq. (2.8). 23. (b) 24. (a) © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 3‐1 Chapter 3 Weight-Volume Relationships and Plasticity 1. A fully saturated soil is a (a) one-phase system consisting of soil solids. (b) two-phase system consisting of soil solids and air. (c) two-phase system consisting of soil solids and water. (d) three-phase system consisting of soil solids, water and air. 2. Which of the following is not a volume relationship? (a) void ratio (b) porosity (c) degree of saturation (d) water content 3. Porosity of a soil is defined as (a) the ratio of volume of voids to the volume of solids. (b) the ratio of volume of voids to the total volume. (c) the volume of water to the volume of voids. (d) The weight of water to the weight of solids. 4. Which of the following is not represented as a percentage? (a) void ratio (b) porosity (c) degree of saturation (d) water content 5. Select the incorrect statement. (a) Void ratio can be greater than unity. (b) Porosity lies between 0 and 100%. (c) Degree of saturation lies between 0 and 100%. (d) Water content is always less than 100%. 6. If void ratio of a soil is 0.2, then its porosity will be (a) 16.7 %. (b) 20.0 %. (c) 25.0 %. (d) none of the above 7. If the specific gravity of soil solids is 2.67, and water content is 32% for a given soil, its void ratio will be (a) 0.12. (b) 0.85. (c) 1.00. (d) none of the above © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 3‐2 8. Dense uniform sand can have a void ratio of (a) 0.1. (b) 0.5. (c) 1.0. (d) 1.2. 9. A representative soil specimen collected from the field weighs 1.9 kN and has a volume of 0.12 m3. The water content as determined in the laboratory is 13.5%. What will be the dry unit weight of the soil? (a) 13.9 kN/m3. (b) 15.8 kN/m3. (c) 17.9 kN/m3. (d) none of the above 10. The relative density of dense granular soils ranges from (a) 15 to 50%. (b) 50 to 70%. (c) 70 to 85%. (d) 85 to 100%. 11. For clean sand samples, emax and emin are related as (a) emax ≈ 0.5 emin. (b) emax ≈ emin. (c) emax ≈ 1.6 emin. (d) emax ≈ 2 emin. 12. The water content of soil at the point of transition from semisolid to plastic state is (a) shrinkage limit. (b) plastic limit. (c) liquid limit. (d) Atterberg limit. 13. If liquid limit = 36%, and plasticity index = 12%, then plastic limit will be (a) 3% (b) 24%. (c) 48%. (d) none of the above 14. As per the liquid limit test (ASTM D-4318), the relation between water content and log N is approximated as (a) straight line. (b) circular curve. (c) hyperbolic curve. (d) parabolic curve. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 3‐3 15. Activity, defined as the slope of line correlating plasticity index and percent finer than 2μ, is used as an index for (a) classifying clay soils. (b) defining Atterberg limits of clay soils. (c) identifying the swelling potential of clay soils. (d) none of the above 16. Which one of the following soils can have in situ moisture content greater than its liquid limit? (a) silty soils. (b) clayey soils. (c) sensitive clayey soils. (d) none of the above 17. Soil deposits that are heavily overconsolidated may have a natural moisture content less than the plastic limit. In that case, the liquidity index, (a) LI < 1. (b) LI = 1. (c) LI > 1. (d) LI ≥ 1. 18. The A-line in the plasticity chart separates (a) clays from the sands. (b) clays from the silts. (c) organic clays from the inorganic silts. (d) inorganic clays from the inorganic silts. 19. The A-line in the plasticity chart is represented by the equation (a) 0.73 8. (b) 0.73 20. (c) 0.9 8. (d) 0.9 20. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 3‐4 Answers, Hints and Discussion 1. (c) Discussion: (b) is correct for dry soil, and (d) for partially saturated soil. A soil does not exist practically as a one-phase system consisting of soil solids only. 2. (d) Discussion and Hint: Water content is a weight relationship; see Eq. (3.8). 3. (b) Discussion: (a), (c) and (d) are correct for void ratio, degree of saturation and water content, respectively. See Eqs. (3.3), (3.5) and (3.8). 4. (a) 5. (d) 6. (a). Discussion: Eq. (3.7): 0.167 or 16.7%.. 7. (b) Discussion: S = 100% for saturated soils. Eq. (3.19): 0.32 2.67 0.85. 8. (b) Hint: See Table 3.1. 9. (a).. Discussion: Eq. (3.9): 15.8 kN/m ; Eq. (3.12): 13.9 /.. 10. (c) Hint: See Table 3.2. 11. (c) Hint: See Eq. (3.36). 12. (b) 13. (b) Discussion: Eq. (3.38): 36% 12% 24%. 14. (a) 15. (c) 16. (c) 17. (a) © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 3‐5 18. (d) Hint: See Fig. 3.19. 19. (b) Hint: See Fig. 3.19. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 4‐1 Chapter 4 Soil Classification 1. Soil classification systems provide a common language to express concisely (a) strength characteristics of soils. (b) permeability characteristics of soils. (c) compressibility characteristics of soils. (d) general characteristics of soils. 2. The soil classification systems are mainly based on (a) grain-size distribution and plasticity of soils. (b) grain-size distribution and strength characteristics of soils. (c) plasticity of soils and strength characteristics of soils. (d) permeability, compressibility and strength characteristics of soil. 3. According to the American Association of State Highway Officials (AASHTO) classification system, soil is classified into _____ major groups. (a) 3 (b) 5 (c) 7 (d) 9 4. According to the AASHTO soil classification system, granular materials have (a) 35% or less passing through 75 μm sieve. (b) 50% or less passing through 75 μm sieve. (c) more than 35% passing through 75 μm sieve. (d) more than 50% passing through 75 μm sieve. 5. According to the AASHTO soil classification, the general subgrade rating for soils of group A-4, A-5, A-6 and A-7 is (a) fair to excellent. (b) fair to poor. (c) excellent to good. (d) excellent to poor. 6. According to the AASHTO soil classification, the term silty is applied when the fine fractions of soil have a plasticity index of (a) 10. (b) 10 or less. (c) 11. (d) 11 or more. 7. Group index (GI) is defined in terms of (a) percent passing 75 μm. (b) liquid limit. (c) plasticity index. (d) all of the above © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 4‐2 8. If the calculated value of GI is negative, it is taken as (a) 0. (b) 0.5. (c) 1.0. (d) none of the above 9. If the calculated value of GI is 3.5, it is taken as (a) 3. (b) 3.5. (c) 4.0. (d) none of the above 10. The group index of soils belonging to group A-3 is always (a) 0. (b) 0.5. (c) 1.0. (d) none of the above 11. In general, the quality of performance of a soil as a subgrade material (a) is directly proportional to the group index. (b) is inversely proportional to the group index. (c) is inversely proportional to square of the group index. (d) does not depend on the group index. 12. The original form of Unified Soil Classification System was proposed by (a) Terzaghi in 1925. (b) Taylor in 1948. (c) Casagrande in 1948. (d) none of the above 13. According to the Unified Soil Classification System (USCS), the fine-grained soils have (a) 50% passing through 75μm sieve. (b) 50% or more passing through 75μm sieve. (c) less than 50% passing through 75μm sieve. (d) none of the above 14. The symbol for silt is (a) C. (b) M. (c) S. (d) none of the above 15. The symbol O is used for (a) organic silts and clays. (b) organic soils. (c) peat. (d) none of the above © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 4‐3 16. Dual symbols are required for (a) Sands with 5 to 12% fines. (b) Gravels with 5 to 12% fines. (c) Both (a) and (b) (d) none of the above 17. The group symbol for silty sand is (a) SS (b) SM (c) MS. (d) none of the above 18. The group symbol SC stands for (a) silty clay. (b) clayey silt. (c) sandy clay. (d) clayey sand. 19. For soils of group MH, (a) LL < 50. (b) LL ≤ 50. (c) LL > 50. (d) LL ≥ 50. 20. For soils of group GW, (a) Cu ≥ 4 and 1 ≤ Cc ≤ 3. (b) Cu ≥ 6 and 1 ≤ Cc ≤ 3. (c) Cu < 4 and 1 > Cc > 3. (d) Cu < 6 and 1 > Cc > 3. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. P a g e | 4‐4 Answers, Hints and Discussion 1. (d) 2. (a) 3. (c) 4. (a) Discussion: (c) is correct for silt-clay materials. 5. (b) Discussion: (c) is correct for granular materials. 6. (b) Discussion: (d) is correct for the term clayey. 7. (d) 8. (a) 9. (c) 10. (a) 11. (b) 12. (c) 13. (b) Discussion: (c) is correct for coarse-grained soils. 14. (b) Discussion: (a) is correct for clay, and (c) for sand. 15. (a) Discussion: The symbol for peat, muck, and other highly organic soils is Pt. 16. (c) 17. (b) 18. (d) 19. (d) 20. (a) Discussion: (b), (c) and (d) are correct for SW, GP and SP, respectively. © 2013 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.