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MODULE 1: ORIGIN OF SOIL AND GRAIN SIZE ENGAGE Soil is a natural substance formed by different processes underwent by rocks. Due to these c...

MODULE 1: ORIGIN OF SOIL AND GRAIN SIZE ENGAGE Soil is a natural substance formed by different processes underwent by rocks. Due to these changes, the physical properties of soil are dictated by the size, shape, and chemical composition of grains In your own discernment answer the following questions by writing your answers in the space provided. 1. In your own opinion, as future civil engineers why do we need to study the concept/s involving soil? 2. What is/are the importance of learning the concepts of soil in your chosen profession? This module includes an overview of the different historical era and personalities who made significant studies and researches in the field of soil mechanics and geotechnical engineering. It aims also to give you an overview of the Origin of Soil and Grain Size. This module includes the Soil-Particle Size and the Mechanical Analysis of Soil. EXPLORE Read: Geotechnical Engineering – A Historical Perspective (pp. 1-13) And Origin of Soil and Grain Size (pp. 15-62) Das B.M., and Sobhan, K. (2014) Principles of Geotechnical Engineering, 8th ed. United States: Cengage Learning Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  UNIT 1: HISTORY OF GEOTECHNICAL ENGINEERING EXPLAIN Geotechnical Engineering Prior to the 18th Century Based on the emphasis and the nature of study in the area of geotechnical engineering, the time span extending from 1700 to 1927 can be divided into four major periods: 1. Preclassical Period of Soil Mechanics (1700–1776) - This period concentrated on studies relating to natural slope and unit weights of various types of soils, as well as the semiempirical earth pressure theories  1717 - French royal engineer, Henri Gautier (1660–1737), studied the natural slopes of soils when tipped in a heap for formulating the design procedures of retaining walls. o According to this study, the natural slope of clean dry sand and ordinary earth were 31° and 45°, respectively. o Also, the unit weight of clean dry sand and ordinary earth were recommended to be 18.1 kN/m3 and 13.4 kN/m3 (85 lb/ft3), respectively.  1729 - Bernard Forest de Belidor (1671–1761) published a textbook for military and civil engineers in France. In the book, he proposed a theory for lateral earth pressure on retaining walls that was a followup to Gautier’s (1717) original study.  1746 - The first laboratory model test results on a 76-mm-high retaining wall built with sand backfill were reported a French engineer, Francois Gadroy (1705–1759), who observed the existence of slip planes in the soil at failure.  1769 – the French engineer Jean Rodolphe Perronet (1708–1794) studied slope stability around and distinguished between intact ground and fills. 2. Classical Soil Mechanics—Phase I (1776–1856) - During this period, most of the developments in the area of geotechnical engineering came from engineers and scientists in France.  1776 – a French scientist Charles Augustin Coulomb (1736–1806) used the principles of calculus for maxima and minima to determine the true position of the sliding surface in soil behind a retaining wall.  1790 - the distinguished French civil engineer, Gaspard Clair Marie Riche de Prony (1755–1839) included Coulomb’s theory in his leading textbook, Nouvelle Architecture Hydraulique (Vol. 1).  1820 - special cases of Coulomb’s work were studied by French engineer Jacques Frederic Francais (1775–1833) and by French applied mechanics professor Claude Louis Marie Henri Navier (1785–1836). These Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  special cases related to inclined backfills and backfills supporting surcharge.  1840 - Jean Victor Poncelet (1788–1867), an army engineer and professor of mechanics, extended Coulomb’s theory by providing a graphical method for determining the magnitude of lateral earth pressure on vertical and inclined retaining walls with arbitrarily broken polygonal ground surfaces. o Poncelet was also the first to use the symbol f for soil friction angle. o He also provided the first ultimate bearing-capacity theory for shallow foundations.  1846 - Alexandre Collin (1808–1890), an engineer, provided the details for deep slips in clay slopes, cutting, and embankments. Collin theorized that in all cases the failure takes place when the mobilized cohesion exceeds the existing cohesion of the soil.  1857 - the first publication by William John Macquorn Rankine (1820– 1872), a professor of civil engineering at the University of Glasgow. This study provided a notable theory on earth pressure and equilibrium of earth masses. Rankine’s theory is a simplification of Coulomb’s theory. 3. Classical Soil Mechanics—Phase II (1856–1910) - Several experimental results from laboratory tests on sand appeared in the literature in this phase.  1856 - French engineer Henri Philibert Gaspard Darcy (1803–1858) published a study on the permeability of sand filters. Based on those tests, Darcy defined the term coefficient of permeability (or hydraulic conductivity) of soil, a very useful parameter in geotechnical engineering to this day.  Sir George Howard Darwin (1845–1912), a professor of astronomy, conducted laboratory tests to determine the overturning moment on a hinged wall retaining sand in loose and dense states of compaction.  1885 - Joseph Valentin Boussinesq (1842–1929) published the development of the theory of stress distribution under loaded bearing areas in a homogeneous, semi-infinite, elastic, and isotropic medium.  1887 - Osborne Reynolds (1842–1912) demonstrated the phenomenon of dilatancy in sand.  Other notable studies during this period are those by John Clibborn (1847–1938) and John Stuart Beresford (1845–1925) relating to the flow of water through sand bed and uplift pressure. 4. Modern Soil Mechanics (1910–1927) - In this period, results of research conducted on clays were published in which the fundamental properties and parameters of clay were established.  Around 1908, Albert Mauritz Atterberg (1846–1916), a Swedish chemist and soil scientist, defined clay-size fractions as the percentage by weight of particles smaller than 2 microns in size. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.   1911, he explained the consistency of cohesive soils by defining liquid, plastic, and shrinkage limits. He also defined the plasticity index as the difference between liquid limit and plastic limit.  1909, the 17-m-high earth dam at Charmes, France, failed. It was built between 1902 and 1906. A French engineer, Jean Fontard (1884–1962), carried out investigations to determine the cause of failure. In that context, he conducted undrained double-shear tests on clay specimens (0.77 m2 in area and 200 mm thick) under constant vertical stress to determine their shear strength parameters (see Frontard, 1914).  Arthur Langley Bell (1874–1956), a civil engineer from England, worked on the design and construction of the outer seawall at Rosyth Dockyard. Based on his work, he developed relationships for lateral pressure and resistance in clay as well as bearing capacity of shallow foundations in clay (see Bell, 1915). He also used shear-box tests to measure the undrained shear strength of undisturbed clay specimens.  Wolmar Fellenius (1876–1957), an engineer from Sweden, developed the stability analysis of saturated clay slopes with the assumption that the critical surface of sliding is the arc of a circle.  Karl Terzaghi (1883–1963) of Austria developed the theory of consolidation for clays as we know today. The theory was developed when Terzaghi was teaching at the American Robert College in Istanbul, Turkey. Geotechnical Engineering after 1927 -The publication of Erdbaumechanik auf Bodenphysikalisher Grundlage by Karl Terzaghi in 1925 gave birth to a new era in the development of soil mechanics. Karl Terzaghi is known as the father of modern soil mechanics.  Publication of the book Theoretical Soil Mechanics by Karl Terzaghi in 1943 (Wiley, New York)  Publication of the book Soil Mechanics in Engineering Practice by Karl Terzaghi and Ralph Peck in 1948 (Wiley, New York)  Publication of the book Fundamentals of Soil Mechanics by Donald W. Taylor in 1948 (Wiley, New York)  Start of the publication of Geotechnique, the international journal of soil mechanics in 1948 in England Two other important milestones between 1948 and 1960 are  Publication of A.W. Skempton’s paper on A and B pore pressure parameters, which made effective stress calculations more practical for various engineering works  Publication of the book entitled The Measurement of Soil Properties in the Triaxial Text by A. W. Bishop and B. J. Henkel (Arnold, London) in 1957. 1960, Bishop, Alpan, Blight, and Donald provided early guidelines and experimental results for the factors controlling the strength of partially saturated cohesive soils. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  UNIT 2: ROCK CYCLE EXPLAIN Three Basic Types of Rocks: Figure 1.1. Rock Cycle 1. Igneous Rocks - are formed by the solidification of molten magma ejected from deep within the earth’s mantle. After ejection by either fissure eruption or volcanic eruption, some of the molten magma cools on the surface of the earth. (e.g. granite) 2. Sedimentary Rock - can be formed by chemical processes. (e.g. limestone) 3. Metamorphic Rock - are formed by process of metamorphism. It is the process of changing the composition and texture of rocks (without melting) by heat and pressure. (e.g. marble) Weathering - it is the process of breaking down rocks by mechanical and chemical processes into smaller pieces Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  UNIT 3: THE ORIGIN OF SOIL EXPLAIN Soil - 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. Soil mechanics - the branch of science that deals with the study of the physical properties of soil and the behavior of soil masses subjected to various types of forces. Soils engineering - the application of the principles of soil mechanics to practical problems. Geotechnical engineering - the subdiscipline of civil engineering that involves natural materials found close to the surface of the earth. Types of Soils According to mode of Transportation and Deposition: 1. Glacial soils—formed by transportation and deposition of glaciers 2. Alluvial soils—transported by running water and deposited along streams 3. Lacustrine soils—formed by deposition in quiet lakes 4. Marine soils—formed by deposition in the seas 5. Aeolian soils—transported and deposited by wind 6. Colluvial soils—formed by movement of soil from its original place by gravity, such as during landslides UNIT 4: SOIL PARTICLE SIZE EXPLAIN Soil Classification According to Particle-Size: 1. Gravels - are pieces of rocks with occasional particles of quartz, feldspar, and other minerals. 2. Sand - are made of mostly quartz and feldspar. 3. Silts - are the microscopic soil fractions that consist of very fine quartz grains and some flake-shaped particles that are fragments of micaceous minerals. 4. Clays - are mostly flake-shaped microscopic and submicroscopic particles of mica, clay minerals, and other minerals. Table 1.1 and Figure 1.2 shows the particle-size classifications developed by different organizations based on the nature of use. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Table 1.1. Particle-Size Classifications Figure 1.2. Soil-separate-size limits by various systems UNIT 5: MECHANICAL ANALYSIS OF SOIL EXPLAIN Mechanical analysis - Determination of the size range of the soil particles - expressed as percentage (%) with respect to the total mass (weight) Two methods generally are used to find the particle-size distribution of soil: 1. Sieve analysis - for particle sizes larger than 0.075 mm in diameter 2. Hydrometer analysis - for particle sizes smaller than 0.075 mm in diameter Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Notes:  Sieve analysis is used to identify percentage of gravel and sand  Hydrometer analysis is used to identify size ranges for fines (sand and silts) – retained in pan in sieve analysis  Sieve analysis and hydrometer analysis are connected but separate tests. Sieve Analysis: - done by shaking (either manual or using mechanical shaker) a mass of soil inside the stack of sieves (a) (b) Figure 1.3. (a) Sieve analysis using mechanical shaker; (b) Sieve arrangement Note:  Sieves are arranged according to the mesh openings - progressively smaller openings - It serves as filter of sizes Table 1.2 shows U.S. standard sieve numbers and the sizes of openings. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Table 1.2. U.S. Standard Sieve Sizes Procedure: - done after the shaking process and careful dismantling of sieves - make sure that the sieves must be arranged properly 1. Determine the mass retained in each sieve including the pan mass retained = (mass of sieve with soil) − (mass of clean sieve) (1.1) 2. Determine the total mass if not available total mass = Σ(mass retained) (1.2) 3. Solve the percent retained in each sieve mass retained (from item 1) %Retained = × 100% (1.3) total mass 4. Determine the accumulated percent retained Accumulated % Ret = (%Retained)n + (%Retained)n+1 (1.4) 5. Solve for the percent passing (%P) or percent finer than (%F) % P or % F = 100% − (Accumulated % Ret) (1.5) 6. Accomplish the particle – size distribution curve (e.g. Figure 1.4) - Plot the points (Particle size vs. %P) - For graph: o Abscissa: (Log-scale) diameter size o Ordinate: (arithmetic-scale) %Passing Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Figure 1.4. Particle-size distribution curve Sample Problem: 2.3 The following are the results of a sieve analysis: ] 63 Determine the percent finer than each sieve. Solution: Note:  Better to present solution in table form Mass of soil % Retained Accumulated % Passing U.S. sieve no. retained, g (Eq. 1.3) % Ret. (Eq. 1.4) (Eq. 1.5) 4 28 4.538 4.538 95.462 10 42 6.807 11.345 88.655 20 48 7.78 19.125 80.875 40 128 20.746 39.871 60.129 60 221 35.818 75.689 24.311 100 86 13.938 89.627 10.373 200 40 6.483 96.11 3.89 Pan 24 3.89 100 0 Total mass (Eq. 1.2) = 617 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Hydrometer Analysis: - is based on the principle of sedimentation of soil grains in water. When a soil specimen is dispersed in water, the particles settle at different velocities, depending on their shape, size, weight, and the viscosity of the water. L (cm. ) D (mm) = K√ (1.6) t (min. ) where: D = particle size, mm. t = time of sedimentation, min. K = function of Gs (Specific gravity of soil solids) and T (temperature of the solution, oC) using Table 1.3 L = bulb depth, cm. as shown in Figure 1.5 Figure 1.5. Definition of L in hydrometer test Table 1.3. Values of K Sample Problem: 2.11 A hydrometer test has the following result: Gs = 2.7, temperature of water = 24°C, ] 65 and L = 9.2 cm at 60 minutes after the start of sedimentation (see Figure 1.5). What is the diameter D of the smallest-size particles that have settled beyond the zone of measurement at that time (that is, t = 60 min)? Given: Gs = 2.7 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  T = 24°C L = 9.2 cm t = 60 minutes Required: diameter D of the particle at t = 60 min. Solution: Using Table 1.3: Gs = 2.7 T = 24°C Therefore, K = 0.01282 Using Eq. 1.6: L (cm. ) 9.2 cm D (mm) = K√ = 0.01282√ ≈ 0.005 mm. t (min. ) 60 minutes Particle Size Distribution Curve: Figure 1.6. Different types of particle-size distribution curves Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Particle - Size Distribution Curve Parameters: 1. Effective size, D10: This parameter is the diameter in the particle-size distribution curve corresponding to 10% finer. The effective size of a granular soil is a good measure to estimate the hydraulic conductivity and drainage through soil. 2. Uniformity coefficient, Cu: This parameter is defined as D60 Cu = (1.7) D10 3. Coefficient of gradation (Coefficient of Curvature), Cc: This parameter is defined as D230 Cc = (1.8) D60 × D10 4. Sorting coefficient, So: This parameter is another measure of uniformity and is generally encountered in geologic works and expressed a D75 So = √ (1.9) D25 The sorting coefficient is not frequently used as a parameter by geotechnical engineers. where: D25, D30, D60, and D75 = diameter corresponding to 25%, 30%, 60%, and 75% finer, respectively All the values of D10, D30, D60, etc. are taken from the particle distribution curve as shown: Figure 1.7. Definition of D75, D60, D30, D25, and D10 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Sample Problems: 2.4 The following are the results of a sieve analysis: ] 63 a. Determine the percent finer than each sieve and plot a grain-size distribution curve. b. Determine D10, D30, and D60 from the grain-size distribution curve. c. Calculate the uniformity coefficient, Cu. d. Calculate the coefficient of gradation, Cc. Solution: a. Determine the percent finer than each sieve and plot a grain-size distribution curve. Note:  Better to present solution in table form Mass of Accumulated U.S. sieve Sieve Opening soil % Retained % Passing % Ret. (Eq. no. (Table 1.2) retained, (Eq. 1.3) (Eq. 1.5) 1.4) g 4 4.75 0 0 0 100 6 3.35 30 6 6 94 10 2 48.7 9.74 15.74 84.26 20 0.85 127.3 25.46 41.2 58.8 40 0.425 96.8 19.36 60.56 39.44 60 0.25 76.6 15.32 75.88 24.12 100 0.15 55.2 11.04 86.92 13.08 200 0.075 43.4 8.68 95.6 4.4 Pan Pan 22 4.4 100 0 Total mass (Eq. 1.2) = 500 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.   Plot the points (Particle Size vs. %P) 100 90 80 70 % Passing 60 50 40 30 20 10 0 10 1 0.1 0.01 Particle Size (mm.) D60 D30 D10 Figure 1.8 b. Determine D10, D30, and D60 from the grain-size distribution curve. D10 ≈ 0.13 mm. D30 ≈ 0.31 mm. D60 ≈ 0.90 mm. c. Calculate the uniformity coefficient, Cu. Using Eq. 1.7: D60 0.90 mm. Cu = = = 6.92 D10 0.13 mm. d. Calculate the coefficient of gradation, Cc. using Eq. 1.8: Note:  Values of Cu and Cc will be used for soil classifications Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  D230 (0.31 mm. )2 Cc = = = 0.82 D60 × D10 0.90 mm.× 0.13 mm. 2.7 The following are the results of a sieve and hydrometer analysis: ] 64 a. Draw the grain-size distribution curve. b. Determine the percentages of gravel, sand, silt, and clay according to the MIT system. c. Determine the percentages of gravel, sand, silt, and clay according to the USDA system. d. Determine the percentages of gravel, sand, silt, and clay according to the AASHTO system. Solution: a. Draw the grain-size distribution curve. - Assign size openings for the sieves Particle-size Percent Analysis Grain Size, finer Sieve no. mm than (Table 1.2) 40 0.425 100 80 0.18 96 Sieve 170 0.09 85 200 0.075 80 0.04 59 0.02 39 Hydrometer 0.01 26 0.005 15 0.0015 8 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.   Plot the points (Particle Size vs. %P) Notes:  Opening greater than 0.425 mm. (for this problem) will consider 100% passing  For particle size/diameter not available in table, use the particle size distribution curve to determine the corresponding percent passing/percent finer than ≈ 72%100 ≈ 66% 90 80 70 % Passing 60 50 40 ≈ 9.5% 30 0.05 mm. 20 0.06 mm. 0.002 mm. 10 0 1 0.1 0.01 0.001 Particle Size (mm.) Figure 1.9 b. Determine the percentages of gravel, sand, silt, and clay according to the MIT system. (limits from Table 1.1, get the difference of percent passing) (≈∞)> (greater 100% Gravel (G) than 0.425 0% G mm. with 2 mm 100% 100% P) Sand (S) 28% S 0.06 mm (use the 72% particle-size Silt (M) 62.5% M distribution 0.002 curve) 9.5% Clay (C) 9.5% C 0 0 c. Determine the percentages of gravel, sand, silt, and clay according to the USDA system. (limits from Table 1.1, get the difference of percent passing) Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  (≈∞)> (greater 100% Gravel (G) than 0.425 0% G 2 mm mm. with 100% 100% P) Sand (S) 34% S 0.05 mm (use the 66% particle-size Silt (M) 56.5% M distribution 0.002 curve) 9.5% Clay (C) 9.5% C 0 0 d. Determine the percentages of gravel, sand, silt, and clay according to the AASHTO system. (limits from Table 1.1, get the difference of percent passing) 76.2 mm (greater 100% Gravel (G) than 0.425 0% G 2 mm mm. with 100% 100% P) Sand (S) 20% S (available in 0.075 mm 80% the table) Silt (M) 70.5% M (use the particle-size 0.002 9.5% distribution Clay (C) curve) 9.5% C 0 0 Additional: Determine the percentages of gravel, sand, silt, and clay according to the USCS system. (limits from Table 1.1, get the difference of percent passing) 76.2 mm (greater 100% Gravel than 0.425 0% G 4.75 mm mm. with 100% Sand 100% P) 20% S (available in 0.075 mm the table) 80% Fines 80% Fines 0 0 Note:  The sum or total of soil classification according to size (Gravel, Sand, Silt and Clay) must be 100% ELABORATE Try solving the following problems: 2.6 The following are the results of a sieve analysis: ] 64 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  a. Determine the percent finer than each sieve and plot a grain-size distribution curve. b. Determine D10, D30, and D60 from the grain-size distribution curve. c. Calculate the uniformity coefficient, Cu. d. Calculate the coefficient of gradation, Cc. 2.8 The following are the results of a sieve and hydrometer analysis: ] 64 a. Draw the grain-size distribution curve. b. Determine the percentages of gravel, sand, silt, and clay according to the MIT system. c. Determine the percentages of gravel, sand, silt, and clay according to the USDA system. d. Determine the percentages of gravel, sand, silt, and clay according to the AASHTO system. 2.12 A hydrometer test has the following result: Gs = 2.75, temperature of water = 23°C, ] 65 and L = 12.8 cm at 100 minutes after the start of sedimentation (see Figure 1.5). What is the diameter D of the smallest-size particles that have settled beyond the zone of measurement at that time (that is, t = 100 min)? Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  EVALUATE As future civil engineers, why do we need to study the size components of soil? Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.