Geotechnical Fundamentals PDF

GEOTECHNICAL FUNDAMENTALS UNIT 3: Soil Classification 3.1.0 Introduction 3.2.0 Definitions of Key Terms 3.3.0 Index Properties and Soil Classification 3.3.1 Introduction 3.4.0 Index Properties and Related Classification T...

GEOTECHNICAL FUNDAMENTALS UNIT 3: Soil Classification 3.1.0 Introduction 3.2.0 Definitions of Key Terms 3.3.0 Index Properties and Soil Classification 3.3.1 Introduction 3.4.0 Index Properties and Related Classification Tests 3.4.1 Soil Grain Size 3.4.1.1 Sieve Analysis (Wash) 3.4.1.2 Hydrometer Analysis (Particle Size Distribution) 3.4.1.2.1 Types of Hydrometers 3.4.1.2.2 Hydrometer Test Corrections 3.4.2 Relative Density 3.4.3 Consistency Limits 3.4.4 Atterberg Limits 3.4.4.1 Soil, Water and Plasticity 3.4.5 Liquidity Index 3.4.6 Activity 3.5.0 Soil Classification 3.5.1 American Association of State Highway and Transportation Officials (AASHTO) Classification System 3.5.1.1 AASHTO Group Descriptions 3.5.2 Unified Soil Classification System (USC) 3.6.0 Questions and Practical Problems 3.7.0 Additional Soil Classification Questions 3.8.0 References Soil Classification 1 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS 3.1.0 Introduction The classification of soils into various categories provides a system to assess the engineering properties of soils. To classify a soil, a variety of laboratory tests are performed which identify the index properties of the soil. Some of the lab tests include particle size distribution, relative density, consistency limits, and Atterberg limits. The general laboratory testing methods will be identified. Once the index property values have been properly determined, the soil can be classified according to three classification systems: Unified Soil Classification System (USC), American Association of State Highway and Transportation Officials (AASHTO), and the United States Department of Agriculture (USDA). 3.2.0 Definition of Key Terms Aggregate Grading A specified range of particle sizes required for specific aggregates. Specification The process of producing aggregates to meet quality requirements Aggregate Production such as specified grading. Group of tests identifying the Liquid Limit, Plastic Limit and Plasticity Atterberg Limits Index of a fine-grained soil. Anything that causes cohesion in loosely assembled substances, Binder such as clay or cement. Series of tests that help to identify the grain-size and index properties Classification Tests for the classification of a material. The ratio of D30 2 / (D60 x D10) , where D10 , D30 , D60 are the Coefficient of Curvature, diameters corresponding to 10, 30 and 60% finer on the Cc cumulative grain-size distribution curve, respectively. The ratio of D60 / D10, where D60 and D10 are the particle diameters Coefficient of Uniformity, that correspond to 60% and 10% finer on the cumulative grain-size Cu distribution curve respectively. The net correction, when performing a hydrometer test, that consists Composite Correction of the temperature correction, dispersing agent correction, and the meniscus correction. Consistency refers to the texture and firmness of a soil and is often Consistency directly related to strength. Consistency is described as very soft, soft, medium firm or stiff, stiff or firm, or hard. Consistency Limits The relative ease with which a soil can be deformed. Density The mass per unit area. Dispersing Agent An agent that prevents fine soil particles in suspension from (Deflocculating Agent) coalescing to form flocs. Soil Classification 2 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS D10, particle diameter corresponding to 10% finer on the grain-size Effecitve Diameter (Size) distribution curve. Term used to reference information that has been obtained through Empirical experience versus calculated observations. Loose, open structured mass formed in a suspension by the Floc aggregation of minute particles. A non-uniform gradation that will contain either an excess or a Gap-graded shortage of various sizes of material. Gradation Specification A specified range of particle sizes required for a specific product. Grain-size Distribution The curve representing the particle (grain-size) gradation. Curve Within the AASHTO system, the group index (G.I.) is used to rate a soil within its group or subgroup. The group index is a number Group Index obtained from the percentage of the soil passing a 0.075mm sieve, its liquid limit, and its plasticity index. The process of determining the grain-size distribution for particles Hydrometer Analysis sizes smaller than 0.075 mm through a sedimentation process in conjunction with the use of a hydrometer. Impervious Soils’ ability to prevent the penetration and inflow of water. Soil properties determined by various tests, which indicate the soil Index Properties type and condition as related to its engineering properties. They are the basis for determining a soil’s classification. Applied to rock or soil when occurring in the situation in which it is In-situ naturally occurring. The water content corresponding to the arbitrary limit between the Liquid Limit liquid and plastic states of consistency of a soil. The ratio, expressed as a % of the natural water content of a soil Liquidity Index minus its plastic limit, to the plasticity index. The process of determining grain-size distribution for material larger Mechanical Analysis than 0.075 mm. Standardized apparatus made of brass or stainless steel containing Mechanical Sieves openings in a range of sizes for the determination of particle gradation. The curve in the upper surface of a liquid close to the surface of the Meniscus container or another object, caused by surface tension. It can be either convex or concave, depending on the liquid and the surface. Particle (Grain-size) The proportions by mass of a soil or fragmented rock distribution in Gradation specified particle-size ranges Soil Classification 3 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS The cumulative percentage of a grain-size passing a designated Percent Passing sieve. The percentage of a grain-size for a specific sieve relative to the total Percent Retained sample. The water content corresponding to an arbitrary limit between the Plastic Limit plastic and the semisolid states of consistency of a soil. The property of a soil or rock, which allows it to be deformed beyond Plasticity the point of recovery without cracking or appreciable volume change. Plasticity Index The numerical difference between the liquid and plastic limits. The systematic process of ensuring quality of products relative to the Quality Control specifications. The ratio of the difference between the void ratio of a cohesionless Relative Density soil in the loosest state and any given void ratio, to the difference between the void ratios in the loosest and in the densest state. Remolded Soil Soil that has had its natural structure modified by manipulation. Sensitivity The effect of remolding on the consistency of a cohesive soil. Sensitivity The effect of remolding on the consistency of a cohesive soil. Shear Strength The maximum resistance of a soil or rock to shearing stresses. Determination of the proportions of particles lying within certain size Sieve Analysis ranges in a granular material, by separation on sieves of different sizes. The specific gravity of a substance is the density of the substance Specific Gravity related to the density of water. The ratio of the mass in air of a given volume of solids at a stated Specific Gravity of Solids temperature to the mass in air of an equal volume of distilled water at (G, Gs) a stated temperature. A precise statement of a set of requirements that are to be met by a material, product, system, or service and that indicates the Specification procedures for determining whether each of the requirements is satisfied. High and low range of acceptable values for the material relative to Specification Envelope the specification sieve sizes. The upper and lower grading limit on selected sizes expressed as Specification Envelope “Percent (%) Passing” which the grain size distribution for the material produced must fall within. Soil Classification 4 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Numerical coefficients used to define the density or consistency of SPT N-Index granular materials, expressed in No. of blows / 0.3m. A mathematical description of the force required to move a sphere Stoke’s Law through a quiescent, viscous fluid at specific velocity. A mathematical description of the force required to move a sphere Stoke’s Law through a quiescent, viscous fluid at specific velocity. The load per unit area at which an unconfined prismatic or cylindrical Unconfined Compressive specimen of material will fail in a simple compression test without Strength lateral support. Material that generally contains particles of one- size such as beach Uniformly-graded sand. Unit Weight Weight per unit volume. Viscosity A measure of a fluid’s resistance to flow. The ratio of the volume of void space, to the volume of solid particles Void Ratio in a given soil mass. Material (uniform gradation) containing a representative portion of all Well-graded sizes of material. Soil Classification 5 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS 3.3.0 INDEX PROPERTIES AND SOIL CLASSIFICATION 3.3.1 Introduction Engineering projects require site investigations to measure some of the soil properties such as permeability, compressibility, and strength, which can often be difficult, time-consuming, and expensive to obtain. Engineers and technologists are able to obtain valuable soils-related information on engineering projects where budget, site, and other constraints restrict full site investigations by using the index properties and soil classification information. The index properties and soil classifications provide the qualitative measurements of the soil properties. The index properties and soil classifications provide qualitative measurements of soil properties. The terminology related to index properties and soil classification is essentially a language used by those involved in the geotechnical area to communicate information in a brief and concise manner without entering into lengthy and detailed soil descriptions. For example, when we talk about clay, we can visualize that clay has a very small particle size and a very large surface area. The particle size is less than 0.002 mm in size, and could be cohesive. The development of systematic soil sorting is known as soil classification. Soil classification is based on certain soil physical properties and similar soil behaviors The classification systems are empirical in nature (i.e. experience-based). Most of the systems were developed to serve a specific type of engineering need. The systems used commonly by engineers are the Unified Soil Classification (USC) System and the American Association of State Highway and Transportation Officials (AASTHO) System. Soil classification is the placing of a soil into a group of soils, all of which exhibit similar behavior. Soil classification can be used to:  Solve simple soil problems  Which types of soil are good for filter layer?  Which type of soil is suitable for sub-base materials?  Guide of detailed test programs  Permeability test, Strength test  Guide for further site investigations  More drilling/more sampling  Convey information and knowledge Soil Classification 6 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Index properties refer to those soil properties that indicate the type and condition of a soil and are the basis for determining a soil’s classification. The tests necessary to determine index properties are known classification tests. They also provide a relationship to the structural properties of soils, such as the strength and compressibility or tendency for swelling and permeability. These index properties will have a bearing on items of engineering importance such as load- supporting ability, tendency to settle or expand, and the effect of water and freezing conditions. It is not necessary to determine all the index properties for every soil on a construction project. Engineering judgment must be exercised to determine the scope of testing, how much information is needed, and how much will be used. Index properties include:  the range of particle sizes and distribution of sizes,  shape of particle sizes,  presence of fine-grained particles,  in-place density and relative density,  consistency,  water content,  plasticity, and  the presence and type of clay. 3.4.0 INDEX PROPERTIES AND RELATED CLASSIFICATION TESTS 3.4.1 Grain Size Soil grain size can be determined by two test methods depending on the size of soil particles. The ranges of particles in coarse-grained soils are determined by a mechanical sieve analysis while the fine-grained soils are assessed using the hydrometer method. Two different test methods are required because the mechanical sieve analysis would not accurately assess the range of particle sizes smaller than 0.075mm. 3.4.1.1 Mechanical Sieve Analysis (Particle/grain Size Distribution) This classification test determines the range of particle sizes in the soil and the percentage of sizes between the maximum and minimum. In the sieve analysis, a series of screens, known as sieves, having different size openings are stacked with the largest opening at the top to the smallest opening at the bottom. The soil is dried with all clumps having been broken up, and the sample is passed through the series of sieves by shaking. The mechanical sieve analysis is carried out in conjunction with a wash-sieve analysis, which is outlined in section 3.4.1.1.1. The complete testing procedures are outlined in ASTM # C117 and C136. Soil Classification 7 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS The results of a grain-size analysis are typically presented in the form of a graph. The particle-size gradation of a soil is presented as a curve, referred to as a grain-size distribution curve. The information obtained from a grain-size curve is: 1. The total percentage of a grain size; 2. The total percentage larger or finer than a given size; and 3. The uniformity or the range in grain-size distribution. 3.4.1.1.1 Sieve Analysis (Wash) A sieve analysis is a mechanical method of determining the grain-size distribution of a coarse- grained soil. A coarse-grained soil is one in which the majority of the particles are visible to the unaided eye. The "wash analysis" option of this test is used where there is a significant clay or silt content in the grain-size distribution. These materials will create clay balls or coat the coarse aggregate hindering the finer material from passing through the nest of sieves. Washing the sample through a 75-µm (#200) sieve removes the clay, silt and other deleterious materials from the coarse aggregate and softens the reducible sizes to help break them down. The wash analysis is usually used where the granular material being tested appears "dirty", Once the sample has been washed and dried, the mass is determined and the soil sample is then passed through a series of sieves of decreasing opening sizes, shaken with a mechanical shaker, as shown in Figure 3.1, and the material collected from each sieve is then weighed. These masses can then be used to determine the grain-size distribution, usually expressed in terms of “% Passing” (also called "% smaller than or % finer than"). 100% Passing 75 mm sieve 60% Passing 25 mm sieve 10% Passing 16 mm sieve The results of the sieve analysis test can be used for several purposes: 1. Classify a soil by one of the various classification systems (AASHTO, USCS, and USDA systems). 2. Use as a method of quality control for aggregate production where a supplier must provide an aggregate to meet gradation specifications provided by the purchaser of the aggregate. 3. Predict certain types of soil behavior such as permeability or frost susceptibility. Soil Classification 8 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Note: Sieving is not an effective method of determining grain-size distribution for fine- grained soils such as silts or clays. It is difficult to grind/break the soil down to individual grains and then pass them through a n extremely fine mesh required to categorize the grain size. Clay and silt soils are usually analyzed by the hydrometer analysis method in which a sedimentation process is used to determine the grain-size distribution. The sieves, made of brass or stainless steel as shown below in Figure 3.1, are made of woven wire called mesh with rectangular openings ranging in size from 101.6 mm (4 in.) to 38 µm (#400 sieve). For most soil work, the 75-µm mesh is the finest sieve used. This is a reasonable limit to the fineness of the analysis because most soil-classification systems use the 75 µm as the dividing point in the classification system. One of the most commonly used applications for the wash-sieve analysis is for quality control of produced aggregates for construction including base, concrete, and asphalt materials. The aggregate producer is provided with a copy of the gradation specifications for the desired product. In other words, a specified range of particle sizes required for a specific product. These requirements are expressed as an upper and lower limit of the “Percent (%) Passing” on selected sieve sizes and the grain- size distribution for the material produced must fall within the given limits. Figure 3.1 Mechanical Shaker An example of grading specifications from Manitoba Infrastructure’s (MI) Grading and Surfacing Specification, 900, is shown below. The specifications for high quality aggregates (Class A) have tighter limits on a larger number of sieves while lower quality aggregates have wider acceptable ranges and fewer numbers of sieves. Producing higher quality aggregates requires more work from the producer and usually results in correspondingly higher bid prices bid for supplying the product. Soil Classification 9 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS 900 3.2 Aggregate Requirements The requirements for each Class will be as follows: ASTM Metric Granular Base, % Passing by Weight Standard Class “A” Class “B” Class “C” Sieves, Gravel or mm Gravel Limestone Gravel Limestone Limestone 37.5 100 25.0 85 – 100 100% 19.0 100 100 100 16.0 80-100 4.75 40 - 70 35 – 70 30 – 75 25 – 80 25 – 80 2.00 25 – 55 25 – 65 0.425 15 – 30 10 – 30 15 – 35 15 – 40 0.075 8 – 15 8 – 17 8 – 18 8 – 18 8 – 20 Minimum Crush Count, % 35 100 25 15 100 Maximum a) Los Angeles Abrasion Loss, % 35 35 35 40 40 b) Shale Content, % 12 12 20 c) Clay Balls, % 10 10 For Class "A" gravel base course, the field tests taken during any crushing shift shall yield an average of 65% or lower passing the 4.75 mm sieve. For Quarried Limestone, a maximum of 7% clean fine sand or any quantity of limestone fines may be added to achieve the required gradation. On testing Class "A" and Class "B" granular base course, oversize retained on the upper sieve will be permitted to a maximum of 3% of the sample, but only if 100% of the oversize will pass a sieve having openings 3 mm larger than the upper sieve. Soil Classification 10 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS As indicated previously, the range of particle sizes, termed the grain-size distribution, can be plotted on a grain-size distribution chart. The shape of the curve can be used to describe the gradation of the material. (Note: % P = Percent Passing) 1. Well-graded material (uniform gradation) contains a representative portion of all sizes of material. This will produce a smooth, even curve. 2. Uniform size - one size material such as beach sand. This produces a very steep line. 3. Non-uniform gradation - will contain either an excess or a shortage of various sizes of material. Soil Classification 11 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS The material specifications, as detailed in MIT's Aggregate Grading Specification, can be shown on a grain-size chart by plotting the upper and lower limits and joining them to produce a specification envelope. The grain-size curve for the material being tested must fall entirely within the specification envelope. Highways Spec. 900.3.2. Aggregate Requirements states “the aggregate shall be well-graded and shall not vary from maximum to minimum of the specification ranges for consecutive test.” Figure 3.3 (Above) Specification Envelopes Soil Classification 12 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Once the grain-size distribution curve has been plotted, the uniformity or range in grain-size distribution can be determined by finding the percentage passing values related to specific particle sizes, specifically the D10, D30, and D60 values. D10 denotes the size such that 10% of the soil particles are smaller than that size. D30 denotes the size such that 30% of the soil particles are smaller than that size. D60 denotes the size such that 60% of the soil particles are smaller than that size. One indication of the gradation of a soil distribution is the Uniformity Coefficient, Cu, which indicates the degree to which the particles are of the same size. If particles are all of the same diameter, Cu may be any number greater than 1, the general rule being that increasing values represent an increasingly wider range of particle size differences; a larger number indicates better gradation. Cu = D60 / D10 The Coefficient of Curvature, Cc, also known as the Coefficient of Gradation, describes the smoothness and shape of the gradation curve. Very high or very low values indicate that the curve is irregular. Cc = (D30 2) / (D60 x D10) When the value of Cc falls between 1 and 3, the soil is well-graded. For a Cc value much less than 1 or larger than 3, the soil is assumed to be poorly graded To recap, the appearance of the plot depends on the range and amount of particles in the soil sample. Well-graded soils are defined as a distribution of particles over a large range of sizes producing a long straight curve while a uniform soil is defined as a distribution of particles over a small range of sizes and produces a nearly vertical plot. A gap-graded soil defined as having an absence of intermediate sizes produce a "bumpy" plot. 3.4.1.2 Hydrometer Analysis (Particle Size Distribution) The Hydrometer analysis is used to determine the grading of fine-grained soils, silts and clays and is based on the principle of sedimentation of soil grains in water. When a soil is dispersed in water, the particles settle at different velocities, depending on their shape, size, mass, and the viscosity of the fluid. For simplicity, it is assumed that all soil particles are spheres and Stoke’s Law can express the velocity of soil particles. Soil Classification 13 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS In 1851, Stokes equated gravitational force to viscous drag on a small spherical particle in suspension and predicted a constant, stable, sedimentation velocity. Solving the Stokes equation for particle diameter, the following equation is obtained: 30𝑛𝑛 𝐿𝐿 D = × (𝐺𝐺𝐺𝐺 − 𝐺𝐺1) × 980𝐺𝐺 𝑇𝑇 Where “D” is the particle diameter in millimeters, “ n ” is the viscosity in 0.01 x poise, “Gs” is the specific gravity of the soils particles, “G 1 ” is the unit weight of the suspending medium, “ L” is the distance of fall, in millimeters, and “T” is the particle traveling time in minutes. Note: The specific gravity of a substance is the density of the substance related to the density of water In a hydrometer test, a soil sample is mixed with water and a dispersing agent to create a suspension. With time, the soil particles will settle out of the suspension; the particles with larger diameters will settle out first. As settling occurs during the test, the average specific gravity of the solution decreases and the hydrometer will sink deeper into the suspension, as shown in Figure 3.4. Readings of the specific gravity at different time intervals provide an indication of the mass of soil remaining in solution and the particle sizes that have settled out of solution. The procedure is described in ASTM D-422. Time increasing from start of test; particles will settle out of suspension. Larger particles will settle first. Elapsed Time Figure 3.4 Settlements of Soil Particles and Decrease of Specific Gravity Soil Classification 14 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS 3.4.1.2.1 Types of Hydrometers There are two types of hydrometers available for soil testing. They are ASTM 151H and 152H. The 151H hydrometer reads the specific gravity of the soil-water suspension directly. However, for these hydrometers care must be exercised to limit the amount of the soil particles to not more than 60 g to produce a 1000 ml soil-water suspension. The 152H hydrometer is calibrated to read from 0 to 60 grams of soil particles in a 1000 ml of soil-water suspension with the specific gravity of the soil solids (Gs) = 2.65. The calibration temperature is 20°C. The 152H will be used in our soil testing. 3.4.1.2.2 Hydrometer Test Corrections In the hydrometer test data analysis, three types of corrections are involved in the calculations. Dispersing Agent Correction In hydrometer tests, a dispersing agent, known as Sodium Hexametaphosphate, is used to neutralize the soil-particle charges. The exact amount and concentration of dispersing agent to be used depends on the soil type and can be established either from experience or by trial. The equations used in the hydrometer analysis are based on the use of distilled or de- mineralized water. Therefore, a correction will be needed to account for the soil suspension with a higher specific gravity due to the presence of dispersing agent or other materials. Temperature Correction Temperature corrections are required in the analysis of the hydrometer readings since the manufacturer calibrates the Hydrometers at 20°C (68°F). Variations in the test temperature will lead to inaccurate hydrometer readings. Meniscus Correction Hydrometers are graduated by the manufacturer to be read at the bottom meniscus, refer to Figure 3.4 Meniscus Formations, formed by the liquid on the stem of the hydrometer. During the hydrometer tests, with the soil particles in suspension in the solution, it is impossible to obtain the bottom meniscus readings, therefore, the top meniscus is used and a correction called the “meniscus correction” is used. Figure 3.4 Meniscus Formations Soil Classification 15 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Composite Correction ASTM designates the net amount of these corrections combined together as a composite correction; refer to the Hydrometer Composite Correction Graph below. The composite corrections can be determined experimentally. According to clauses 7.2 & 7.3 of ASTM D422, the composite corrections for hydrometers with a specific amount of dispersing agent being used in the test, are determined as follows: "7.2 For convenience, a graph or table of composite corrections for a series of 1°- temperature differences for the range of expected test temperatures may be prepared and used as needed. Measurement of the composite corrections may be made at two temperatures spanning the range of expected test temperatures, and corrections for the intermediate temperatures calculated assuming a straight-line relationship between the two observed values. 7.3 Prepare 1000 mL of liquid composed of distilled or demineralized water and dispersing agent in the same proportion as will prevail in the sedimentation (hydrometer) test. Place the liquid in a sedimentation cylinder and the cylinder in the constant-temperature water bath, set for one of the two temperatures to be used. When the temperature of the liquid becomes constant, insert the hydrometer, and, after a short interval to permit the hydrometer to come to the temperature of the liquid, read the hydrometer at the top of the meniscusformed on the stem. For hydrometer 151H the composite correction is the difference between this reading and one; for hydrometer 152H it is the difference between the reading and zero. Bring the liquid and the hydrometer to the other temperature to be used, and secure the composite correction as before." Fig. 3.5: Composite Correction Graph Soil Classification 16 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS 3.4.2 Relative Density Two important characteristics of soils are shear strength and resistance to compression, which are both related to the density of a soil. Dense or compacted soils have higher shear strength and are more resistance to compression than loose soils. In a dense condition, the void ratio is low; in a loose condition, the void ratio is high. Determining a relative density value provides information that helps to assess the engineering properties of the soil. To evaluate the relative condition of a granular soil, the in-place density can be determined and compared to the void ratio when the soil is in its densest condition and when it is in its loosest condition. The comparison is termed the Relative Density, DR %. emax - eO DR % = x 100% emax - emin Where emax = void ratio of the soil in its loosest state; highest void ratio emin = void ratio of the soil in its densest state; smallest void ratio e0 = void ratio of the soil in the natural condition or condition in question The relative density can also be determined in terms of dry density and dry unit weight: 3.4.3 Consistency Limits Consistency refers to the texture and firmness of a soil and is often directly related to strength. Consistency is described as very soft, soft, medium firm, firm, stiff, or hard. The consistency of a fine-grained soil varies with the amount of water present in the soil. The greater the amount of water, the lesser the interaction exists between the soil particles and the soil becomes more fluid (softer). The strength of clay is related to its structure. If the original clay is altered because of a change in particle arrangement or chemical changes, the strength of the altered clay is less than the original. Soil Classification 17 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS The determination of the texture or firmness of a soil is subjective; therefore, a more reliable means of assessing the strength of a soil is to determine the unconfined compressive strength in the soil’s original state to that once the soil has been remolded. Sensitivity is the term that provides an indication of remolded strength related to the original strength. When remolded, the strength of the clay is affected by the water content, therefore, sensitivity should be based on the comparison of remolded to undisturbed soil strength at identical water contents. 𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆ℎ, 𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈 Sensitivity, S = 𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆ℎ, 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 For most clays, Sensitivity ranges between 2 and 4. Clays considered sensitive have values between 4 and 8. Extra sensitive clays have values between 8 and 16. Quick clays are those with sensitivity values greater than 16. Normally clays with a high degree of sensitivity possess a very flocculent structure in the undisturbed condition. Since unconfined compressive strength testing is time intensive and expensive, civil technologists and engineers commonly use the liquid limit, plastic limit and shrinkage limit, known as the Atterberg Limits, as a way of assessing the strength characteristics of fine- grained soils. The engineering behaviours of cohesive soils (clays) are largely influenced by the presence of water in the soil. Clay particles are essentially plate shaped particles with a very large surface area and the water is bonded to the surface by atomic forces. As the moisture content of clay increases, the consistency of the soil changes due to the lubricating effect of the water between the particles. 3.4.4 Atterberg Limits The Atterberg Limits are index property values that relate the behavior of fine-grained soils relative to the presence of water. The Atterberg Limits where named after a Swedish soil scientist, Atterberg, who developed a method of describing quantitatively the effect of soil moisture on the consistency of fine-grained soils. The limits he proposed are arbitrarily defined. The five "limits" proposed by Atterberg are the Cohesion limit, Sticky limit, Liquid limit, Plastic limit and Shrinkage limit. The liquid limit and the plastic limit are the two most commonly used index properties for engineering purposes. Atterberg arbitrarily defined soil consistency by dividing soil into four basic categories or states: Liquid Soil would flow to take the shape of the container, no shear strength. Plastic Soil will deform without cracking when subjected to external forces. Semi-Solid Soil would deform with cracking when subjected to external forces. Solid Soil will have constant volume. Soil Classification 18 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Atterberg defined the limits as the moisture contents at which the soil would pass from one state of consistency to another. Every cohesive soil has its own unique set of Atterberg Limit values used to classify soils. Liquid Limit (L.L.) The moisture content above which the soil is in the Liquid State. Plastic Limit (P.L.) The moisture content above which the soil is in the Plastic State. Shrinkage Limit The moisture content below which the soil is in the Solid State. The liquid limit is the water content at which the soil "flows". The plastic limit is the water content at which the soil can be rolled into a 3-mm (1/8”) diameter thread before crumbling. When performing the Atterberg Limits laboratory tests, the ASTM and AASHTO standards specifically define how the liquid limit and plastic limit are determined, as highlighted below from ASTM D-4318. Liquid Limit Test (Casagrande method): Soil at different moisture contents is placed in a liquid limit cup. A groove is cut through the soil and the liquid limit is defined as the moisture content at which it takes exactly 25 blows (one blow consists of dropping the cup through a height of 1 cm) to close the groove a distance of 12.7 mm (0.5 inch). Plastic Limit: The plastic limit is the moisture content of a soil at which the soil begins to crumble when it is rolled into a thread of 3 mm (1/8 inch) in diameter. Note: The soil must be roll to diameter of 3 mm (1/8 inch) at least once. If the soil crumbles the first time it reaches 3 mm in diameter, then the moisture content at that point is the plastic limit. If the soil does not crumble, re-mold the soil in your palm to get rid of some of the moisture. The plastic limit is the moisture content of the soil when it crumbles at or before 3 mm diameter. 3.4.4.1 Soil, Water and Plasticity Silt and clay are difficult to distinguish based on particle size alone since surface activity has an important controlling effect on the behavior of fine-grained soils. The practical distinction between silt and clay is made, not on the basis of an arbitrary size distinction, but on the basis of material behavior in the presence of water. Soil Classification 19 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS The consistency of fine-grained soil varies according to the amount of water present as shown in Figure 3.6, States of Fine Soil Consistencies. Completely dry, the soil may be hard (solid) while at high water contents, it may become slurry-like (liquid). Intermediate states of consistency are semi-solid and plastic states. A plastic material is one that deforms readily without cracking or rupture. Solid Semi-solid Plastic Liquid PI SL PL LL Increasing Water Content Figure 3.6 State of Fine Soil Consistencies We define the boundaries of these states of consistency in terms of soil water content. The water content at the plastic-liquid boundary is the liquid limit (LL) while that at the plastic-semi- solid boundary is the plastic limit (PL). The difference between the liquid and plastic limits is the range of water contents over which a soil is plastic; designated as the plasticity index (PI). Different soils may be distinguished by their plasticity characteristics because these characteristics vary with surface activity of the constituent particles. The more active soils (clay-like) are more plastic than the inter-active soils (silts). This phenomenon may be explained by examining the nature of the water near the surface of a clay particle. Figure 3.7 is a conceptual view of a clay particle surrounded by water. Fig. 3.7: Conceptual view of clay particle surrounded by water Soil Classification 20 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Since water is dipolar in molecular structure, the water near the clay particle is effectively immobilized by the surface charge. It is adsorbed and may be considered essentially solid. As the distance from the soil particle’s surface increases, the orientation of water is reduced in degree until, at the boundary of the particle’s influence (limit of diffuse double layer), the viscosity is that of free water and the mixture would be fluid. As the amount of water decreases, the particles are separated by increasingly stiffer water. The mixture becomes as a solid. The soil-water system’s phase (soil type or fluid) causes a change in the plasticity range. This permits us to distinguish among soils of their plasticity. Although the liquid limit and plastic limit are important, the difference between them, known as the Plasticity Index, is another qualitative value used to define fine-grained soil behavior as well as helping to distinguish or classify fine-grained soils. The plasticity and clay fraction of a soil are frequently used to identify the swelling potential of expansive soils. The Plasticity Index (P.I.) of a soil is the numerical difference between the Liquid Limit (L.L.) and the Plastic Limit (P.L.) and represents the range of moisture content for which the soil exists in the plastic state. P.I. = L.L. - P.L. The plasticity index values are determined according to ASTM D4318 standard test procedures. Plasticity Index: This is one of the very important properties of a soil relating to the consistency of a soil-water mixture. The plasticity index is the numerical difference between the liquid limit and the plastic limit of a soil. It represents the range within which a soil exhibits the properties of a plastic. It is also a measure of the cohesive properties of a soil and indicates the bonding properties of a fine clay and colloidal fraction of the material. For example, the plasticity index is an empirical indicator of the suitability of the clay fraction of a binder material in a stabilized soil mixture. Experience has indicated that a granular-clay mixture with a very high plasticity index tends to soften in wet weather. The soil develops ruts under traffic and also develops a washboard surface that becomes slippery in wet weather If the plasticity index of the soil is too low or non-plastic, the soil will become friable in dry weather, ravel at the edges, and abrade severely under traffic. Therefore, the roadways become dusty in service and much of the binder material may gradually be blown or eroded away. As property indices, high plasticity index values or high liquid limits are characteristic of clay soils. The P.I. describes the plasticity of the soil as its ability to resist plastic deformation. It can also be used to approximate other soil characteristics such as volume change, dry strength, and stickiness. Soil Classification 21 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS According to the ASTM D 4318, both the liquid limit (L.L.) and the plastic limit (PL) are reported as whole numbers. If either the L.L. or P.L. could not be determined or if the P.L. is equal to or greater than the L.L., the soil is classified as non-plastic, N.P. Figure 3.8, Unified Soil Classification (USC) Plasticity Chart, shows how the liquid limit and plasticity index, (index properties), are used in soil classification. Also, Figure 3.9, a Plasticity Chart, highlights the relationship between the plasticity index and the consistency of fine- grained soil. Figure 3.8 Unified Soil Classification (USC) Plasticity Chart Figure 3.9 Plasticity Chart Figure 3.10 and 3.11 are charts which highlight the relationship between the plasticity index value, liquid limit value, and the tendency for a clay soil to swell, allowing the swelling potential to be estimated. Soil Classification 22 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Swelling Potential (After Sowers and Kennedy 1967) Probably Low Volume Change PI < 25 Probably Moderate Volume Change PI 25 to 40 Probably High Volume Change PI > 40 Figure 3.10 Swelling Potential Based on PI Swelling Potential (After LDOT 1973) Liquid Limit Plasticity Index Swell Potential 20 - 49 15 - 24 Low to medium 50 – 70 25 – 46 High > 70 > 46 Very high to severe Figure 3.11 Training handout of the Louisiana Department of Transportation (Table 6-1) 3.4.5 Liquidity Index Liquidity Index is the comparison of the natural moisture content of a soil with its plasticity index which can provide an indication of the soil's consistency and/or sensitivity potential. w % - PL w % - PL where w = natural water content of soil LI = = LL% - PL% PI A value less than one indicates the natural water content is less than the liquid limit; a value near zero indicates a water content near the plastic limit, where experience has shown that the sensitivity will be low and the strength relatively high. As the water content approaches or exceeds the liquid limit, the sensitivity increases. Negative values indicate a dried or desiccated hard soil. 3.4.6 Activity Plasticity is the ability of a soil to undergo deformation at a constant volume. The range of water contents a soil will behave plastically is related to the amount of clay minerals and ratio of particle sizes to their surface areas. Soils with high clay mineral contents will need more water to behave plastically. Research has indicated that the liquid limit increases as the average size of the soil particles decreases. Identifying the type and amount of clay mineral may be necessary to predict the soil's behavior. The identification of clay mineral requires special and expensive techniques Soil Classification 23 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS that include X-ray diffraction, differential thermal analysis, infrared absorption and others tests beyond the scope of this course. An indirect method of obtaining information on the type and effect of clay mineral in the soil is to relate the plasticity of the soil to the quantity of clay-sized particles within the soil. Activity, is one relationship, defined as: Plastic Index Activity = Percentage of Clay Sizes Below 0.002mm A relative activity classification is shown below: Activity Classification < 0.75 Inactive Clays 0.75 - 1.25 Normal Clays > 1.25 Active Clays Figure 3.12 Activity Classification Fig. 3.13 Classification according to activity (V.N.S. Murthy; Geotechnical Engineering, Principles and Practices of Soil Mechanics and Foundation Engineering) Soil Classification 24 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS 3.5.0 SOIL CLASSIFICATION The purpose of performing the various classification tests is to identify the soil index properties to classify the soil for use in engineering applications. The results of the index properties can be used in conjunction with three established soil sorting or soil classification systems: AASHTO - American Association of State Highway and Transportation Officials System. ASTM M145, D2487, D3282. USC - Unified Soil Classification System USDA - United States Department of Agriculture Textural Classification, The three classification systems have many of the same grain-size ranges; however; care must be taken to ensure that the correct sieve-size designations are used as they do have variations. 3.5.1 (AASHTO) American Association of State Highway and Transportation Officials Classification System AASHTO, the oldest soil classification system, was developed in 1928 by Terzaghi and Hogentogler for the U.S. Bureau of Public Roads. The classification was revised, modified, and adopted by the American Association of State Highway Officials (A.A.S.H.O.). The classification is now designated as the AASTHO system (AASTHO Method M145, ASTM Designation D3282). In the AASTHO soil classification system (Table 8), soils are sorted into eight groups: A-1, A-2, A-3, A-4, A-5, A-6, A-7 and A-8. A-1, A-2, and A-3 are the coarse-grained soils, such as gravel, sand and sand-gravel mixture. A-4 and A-5 are silty soils. A-6 and A-7 are clayey soils. A-8,is peat soils. In addition to the basic group classification, soils are sub-divided further into sub-groups within each group. The group designations are numerical indicators of the quality of soils from an engineering standpoint. Generally, the lower the number, the better is the soil for engineering uses. Soils are poorer for use in road construction as one moves from left to right in the chart, for example, an A-6 soil is less satisfactory than an A-5 soil. Soil Classification 25 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS The quality of a soil is also rated within the group and is identified by a group index number shown as (#). Soils are poorer for road construction as the group index increases for a particular sub-group; for example an A-6 (3) soil is less satisfactory than an A-6 (1) soil. The AASTHO classification system uses the following index properties and classification tests to classify the soil. 1. The mechanical sieve analysis, 2. The liquid limit. 3. The plasticity index. The classification procedures are as follows: 1. The users start from the left-hand column on the chart and determine if all the known properties of the given soil comply with the limiting values of the soil properties specified in the column. 2. If the properties do not comply with the first column, the next column to the right is checked, and the process continues across the chart until the proper column is reached. 3. The first column where the properties of the given soil comply with the specified values in the column indicates the group or sub-group to which the soil belongs. (Note: Group A-3 follows A-1to allow for proper classification. This arrangement does not mean that A-3 soil is "better" than A-2 soils.) Soil Classification 26 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Figure 3.14 Table 8 – AASHTO Classification Fig. 3.15: The ranges of the LL and PI for groups A-2, A-4, A-5, A-6 and A-7: Soil Classification 27 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS 3.5.1.1 AASHTO Group Descriptions Group A-1 Well graded gravel or sand; may include some fines. Sub-group A-1-a Includes predominantly stone fragments or gravel, either with or without a well- graded fine binder. Sub-group A-1-b Includes gravely sand, coarse sand either with or without a well-graded fine binder. Group A-3 Typical A-3 soils are fine beach or wind-deposited sands without silty or clayey fines or with a very small quantity of non-plastic silt. A-3 soils also include water-deposited mixtures or poorly-graded fine sand and limited quantities of coarse sand and gravel. Group A-2 Consists of a wide variety of granular materials. It consists of the coarse-grained materials that do not fall into groups A-1 and A-3. That is, sands and gravels with excessive fines. Subgroup A-2-4 and A-2-5 Includes gravel and coarse sand with silts or plasticity index in excess of the limitations of Group A-1 and fine sand with non-plastic silt in excess of the limitations of Group A-3. The characteristics of the minus No. 40 portion of the group have the similar characteristics of the A-4 (low compressibility silts) and A-5 (high-compressibility silts,micaceous silts) groups. Subgroups A-2-6 and A-2-7 Consist of granular materials similar to the materials under subgroups A-2-4 and A-2-5 except that the fine portion of the subgroups is plastic clay having the characteristic similar to the A-6 (low-to-medium-compressibility clays) and A-7 is made up of high compressibility clay groups. Group A-4 Low compressibility silts. The typical material of this group consists of non-plastic or moderately plastic silty material with 75% or more of the material passing the 0.075mm sieve. The group includes also mixtures of fine silty soil and up to 64% of sand and gravel retained on the 0.075mm. Soil Classification 28 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Group A-5 High compressibility silts. The typical material of this group consists of soils similar to Group A-4 but the soils are highly elastic, indicated by the high liquid limit. Group A-6 Low-to-medium compressibility clays. The typical materials consist of plastic clay with 75% or more materials finer than 0.075mm. It also includes a mixture of clayey soil with up to 64% of sand and gravel. Materials of this group have high volume change between wet and dry states. Group A-7 High compressibility clays. It consists of fine-grained soils similar to the materials under Group A-6. Group A- 7 soils have higher liquid limit and are more elastic. They may have very high volume change behavior. Subgroup A-7-5 High compressibility silty clays. The group includes those fine materials with moderate plasticity indexes in relation to liquid limit, and may be highly elastic as well as may have considerable volume change. Subgroup A-7-6 High compressibility, high-volume change clays. The group includes those materials that have high plasticity indexes in relation to liquid limit; the soils under this group are subject to extremely high volume change. Group A-8 Consists of peat or muck, with low density, high compressibility, high water contents, and high organic matter. They are typically found in unstable, swampy areas. 3.5.1.2 Group Index The group index (G.I.) is used to rate a soil within its group or subgroup. The group index is a number obtained from the percentage of the soil passing a 0.075mm (#200) sieve, its liquid limit, and its plasticity index. The index is obtained from the following empirical formula: Soil Classification 29 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Group Index = (F - 35) [0.2 + 0.005 (LL - 40)] + 0.01 (F - 15) (PI-10), where F is the percent of soil passing a 0.075mm (No. 200 sieve), expressed as a whole number. Note: If F 50. Suffix Subgroup (Secondary Letter) Well graded, with little or no fines W Well graded, with plastic clay binder C Poorly graded, with little or no fines P Poorly graded, with non-plastic fines M Low plasticity (LL < 50) L High plasticity (LL > 50) H Soil Classification 30 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS A visual description usually accompanies the USC soil classification. The description is based on: 1. Consistency or density – a. For cohesive soil, the descriptions usually are very soft, soft, firm, stiff, very stiff, or dry. b. For non-cohesive, soil the descriptions are loose, medium dense, or dense. 2. Particle shape - round, sub-angular, angular 3. Colour - white, grey, brown, light brown (tan), red-brown, etc. Consistency or density of coarse-grained soils standard penetration tests (SPT): Consistency SPT N-Index (Blows per 0.3 m) Very loose 0-4 Loose 4-10 Compact 10-30 Dense 30-50 Very dense Over 50 Firmness of in-situ soil from field-testing: Soil Type Term Field Test Sands, Excavated with a spade; 50 mm wooden peg can be Loose gravel easily driven. Requires a pick for excavation; 50 mm wooden peg is Dense hard to drive. Slightly Visual examination; pick removes soil in lumps which cemented can be abraded. Soft or loose Easily molded or crushed in the fingers. Silts Firm or dense Molded or crushed by strong pressure in the fingers. Exudes between the fingers when squeezed in the Very soft hand. Soft Moulded by light finger pressure. Clays Firm Can be moulded by strong finger pressure. Cannot be moulded by the fingers: can be indented Stiff by the thumb. Very stiff Can be indented by the thumbnail. Organic Firm Fibres already compressed together. Peats Spongy Very compressible and open structure. Soil Classification 31 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS The USC Classification Procedures are as follows: 1. The user starts from the left-hand column on the chart and determines which criteria the soil satisfies, for example based on the No. 200 sieve, is the soil determined to be coarse-grained or fine-grained. The answer will determine the next column and the resulting soil criteria to be assessed. 2. The soil must satisfy some criteria within each column, which will also provide the direction for continued movement through the classification process. 3. The final column in which the properties of the given soil are satisfied indicates the classification of the soil. Depending on the soil properties the chart may indicate a dual classification in where the soil satisfies two classification criteria and is termed dual classification. Note: The USC chart is used in combination with a LL and PI Chart. EXAMPLES Percent Passing by Mass Sieve Size, mm A B C 9.5 100 100 100 4.75 42 72 95 2.00 33 55 90 0.425 20 48 83 0.150 18 42 71 0.075 14 38 55 LL 35 39 55 PL 22 27 24 Pl 13 12 31 Dark tan, very Grey-brown, Blue-grey, traces Visual Observation gravelly some color of gravel Classify each of the above soil samples using: 1. The Unified Soil Classification System 2. The AASHTO Soil Classification System Soil Classification 32 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Dual Classification Example Using the Unified System to classify the soil based on the following given information. Sieve Size, mm 19 9.5 4.75 2.00 0.425 0.150 0.075 % Passing 70 56 43 32 20 18 10 From the hydrometer test, the clay content of the soil is 6%. Liquid Limit = 40 Plastic Limit = 20 Visual description: grey colour with some organic materials. 3.6.0 Question and Practical Problems Lesson 1 Questions 1) Discuss why classification systems are necessary. 2) Identify the meaning of the following abbreviations: AASHTO, USC and USDA. 3) Define what is meant by “index properties” and provide an example of an index property. 4) Discuss the relationship between soil classification tests and the structural properties of soil. Lesson 2 Questions 1) Explain the basic purposed for performing the mechanical sieve analysis and the hydrometer analysis. 2) Which test standards outline the proper procedures for performing the two tests identified in question #3. 3) Define the following: a. Coarse fractions of soils b. Fine fraction of soils 4) Describe how the results of a sieve analysis test could be utilized. 5) The sieve analysis results are typically represented graphically through a gradation curve. List the information that can be determined/obtained from reviewing the gradation curve. Soil Classification 33 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS Lesson 3 Questions 1) Describe the relationship between relative density, compaction and the strength of soil. 2) Relate the presence of water to the consistency of clay soil at the plastic and liquid limits. Explain the meaning of the plasticity index. 3) List the factors affecting the accuracy of the Atterberg test results. 4) Discuss how clay and water interact to produce a cohesive material. Lesson 4 Questions 1) Describe the three components of a visual description for soils classification. 2) Compare and contrast the AASHTO and USC classification systems. 3) Identify a critical component to classifying a soil containing granular material according to the USDA system. 4) Explain meaning of the group symbol letters in the Unified Classification system. 5) What observations could be made about a soil sample that classified as A-2-6 (35). 3.7.0 Additional Soil Classification Questions Show all work and include all related graphs etc. 1 Classify the soil, tested in a laboratory with the indicated results, according to the AASHTO system. Sieve Size, mm % Passing 4.75 100 2.00 85 0.425 72 0.075 58 Liquid Limit 46 Plastic Limit 22 2 Classify the soil, tested in a laboratory with the indicated results, according to the USC system. Sieve Size, mm % Passing 9.5 100 4.75 76.5 2.00 60.0 0.425 39.7 0.075 15.2 Liquid Limit 30 Plastic Limit 12 Soil Classification 34 Revised: 2020-09-29  GEOTECHNICAL FUNDAMENTALS 3 Classify the soil, tested in a laboratory with the indicated results, according to the USC and ASSHTO systems. Sieve Size, mm % Passing 25.0 100 19.0 85 12.5 70 9.5 60 4.75 48 2.00 30 0.425 16 0.150 10 0.075 2 Liquid Limit NP Plastic Limit NP 4 Classify the soil, tested in a laboratory with the indicated results, according to the USC system. Sieve Plastic Liquid 9.5 4.75 2.00 0.850 0.425 0.150 0.075 Size, mm Limit Limit % Passing 100 90 62 50 34 9 6 50 40 3.8.0 REFERENCES Annual Book of ASTM Standards, Section 4-Construction, Volume 04.08 Soil and Rock; Dimension stone; Geosynthetics. American Society for Testing and Materials, ASTM Philadelphia, PA. Basic Soils Engineering, B.K. Hough, Second Edition. The Ronald Press Company, 1969, United States of America. Essentials of Soil Mechanics and Foundations. Basic Geotechnics, Sixth Edition. McCarthy, David F. Prentice Hall, 2002, Upper Saddle River, New Jersey. Introductory Soil Mechanics and Foundations: Geotechnical Engineering, Fourth Edition. Sowers, George F. MacMillan Publishing Company, New York, Collier MacMillon Publishers, London, 1979. United States of America. Physical and Geotechnical Properties of Soils, Joseph E. Bowles. McGraw-Hill Book Company, 1979. United States of America Soils Manual for Design of Asphalt Pavement Structures. The Asphalt Institute, Second Edition, April 1963. Third Printing, February 1969. Manual Series No. 10(MS-10). Soil Classification 35 Revised: 2020-09-29