Success in geotechnical analysis, design, and construction invariably requires that we have proper knowledge and understanding of (1) the strength, (2) the fluid flow properties, and (3) the stress-deformation behavior of the earth materials. These important engineering properties are primarily determined by the components and structure of a soil, which also dictate the soil's responses in an electromagnetic field. As a nondestructive technique, the electromagnetic property measurement offers a promising approach to characterize earth materials and identify the effects of changes in environments. However, despite many investigations in the last several decades, the relationship between the frequency-dependent electromagnetic properties of soils and their components and structure are still not well understood. Hence, estimation of engineering properties of a soil in a quantitative way from electromagnetic measurements can be uncertain. In this research several tasks have been accomplished: (1) Development of a physically based model that provides a means of investigating the coupled effects of important polarization mechanisms on soil electromagnetic properties, and a means of relating the electromagnetic properties of a soil to its fines content, clay mineralogy, anisotropy, degree of flocculation and pore fluid chemistry; (2) Proposal of a practically applicable method to determine the volumetric water content, specific surface area and pore fluid salt concentration simultaneously from the dielectric spectrum; (3) Deduction of the wide-frequency electromagnetic properties of a soil by measuring its responses to a step pulse voltage using time domain reflectometry (TDR); (4) Establishment of the relationships between the specific surface area and compressibility, residual shear strength and hydraulic conductivity. This study establishes a framework for quantifying soil engineering properties from their electromagnetic properties. If properly determined and interpreted, the electromagnetic properties can also provide insights into the causes of soil property changes over time and can be very useful in studying the effects of biological factors in geotechnical engineering, a field that may offer great potential for future advances. / Ph. D.

Unlike other thermo-mechanical soil responses, the effects of temperature on residual shear strength of soils are not well understood. Previous studies on temperature effects on residual shear strength show some contradictory findings that might be attributed to the sample's mineralogical composition and the testing procedure. This thesis aims to contribute to the understanding of (1) the temperature effects on the liquid limit of cohesive soils, (2) the impact of testing procedure on temperature-dependent residual friction angle, and (3) temperature effects on residual friction angle of soils. The fall cone tests are used to determine temperature effects on the liquid limit, while a temperature-modified ring shear apparatus is used to evaluate the residual friction angle in this study. To assess the impact of the testing procedure, the temperature is changed to 50°C at three different instants: before consolidation, before preshearing, and after preshearing; the resulting residual friction angles are assessed and compared. The effects of temperature on residual friction angle of soils are also investigated by changing the temperature in the ring shear apparatus to 10°C, 20°C, 40°C, and 50°C before consolidation. The study found that the impacts of temperature on liquid limit is mineralogy dependent. Also, the instant at which temperature change occurs in ring shear tests was found to be insignificant in terms of the residual friction angle. Moreover, the findings of the ring shear experiments suggest that clay mineralogy is important in the study of temperature-dependent residual friction angle of cohesive soils. Antigorite-rich soils may experience up to 50% changes in their residual friction angle, while soils with other clay minerals may experience less than 20% variations over a temperature range from 10 to 50 °C. / Master of Science / The increase in the frequency of landslides was found to be attributed to seasonal variation in temperature and an increase in global temperature due to climate change. To anticipate, mitigate and adapt to this costly natural disaster, understanding soil response to temperature change is an essential step. The residual shear strength of a soil is a parameter used to analyze stability of landslides. The relationship between this residual shear strength and temperature is not well understood. Previous studies on temperature effects on residual shear strength show some contradictory findings that need to be better understood for a more robust assessment of the climate change impacts on the stability of natural and man-made slopes. This thesis represents a first step to fill the knowledge gap in identifying the temperature effects on the residual shear strength of soils so that the impact of climate change and seasonal variation in temperature on slopes can be assessed more rigorously. This study consists of three tasks. The first task is to assess the effects of temperature on liquid limit, a parameter widely used to estimate the residual shear strength. The second task is to investigate the impacts of the testing procedures on residual shear strength, representing three field conditions where temperature change takes place at three different instants: when the soils is consolidating under applied load, after the soil consolidated and before development of a failure plan, and after failure initiated. The last task is to assess the effects of temperature on residual shear strength of soils. From the study, it was found that the effects of temperature on liquid limits and residual shear strength are dependent on the soil's mineralogical composition. It was also found that the instant in which the temperature changes in the testing procedure does not substantially impact the residual friction angle of the soil.

När geotekniska laborationsanalyser utförs undersöks ofta kolvprover från olika djup som får representera marken vid det djupet provet är taget. I ett homogent lerskikt kan denna punkt antas vara representativ. I en icke-homogen lerjord, till exempel i varvig lera, skulle denna punkt kunna infalla i en icke-representativ variation. För att ta reda på om dessa strukturella variationer påverkar en leras mekaniska egenskaper har i denna studie lerprover från olika platser i Stockholms län analyserats. Genom laborationsundersökningar har lerornas vattenkvot, konflytgräns och lerhalt bestämts och jämförts med varandra. Konflytgränsen definieras som vattenkvoten då en lera går från plastisk konsistens till flytande konsistens och bestäms i denna studie med fallkonmetoden (Axelsson & Mattsson, 2016). Vattenkvoten anger förhållandet mellan jordens fasta massa och vattnets massa och bestäms genom vägning och torkning i ugn (Larsson, 2008). Lerhalten i ett jordprov bestäms genom en hydrometeranalys som anger mängden lera i förhållande till övriga kornstorlekar i provet. Proverna som har studerats i denna studie var av varierande kvalitet med avseende på varvighet och både glaciala och post-glaciala leror har undersökts. Resultatet visar att det är svårt att studera skillnader mellan ljusa och mörka variationer i leror som inte har en tydlig varvighet och att stora variationer förekommer i de undersökta parametrarna för mörka såväl som ljusa skikt. / When geotechnical laboratorial analyzes are executed, piston samples from different earth depths are commonly used. These samples will represent the soil at the given depth. The point at which the sample is taken could be seen as representative in a homogenous layer of clay but in an inhomogeneous layer, such as a varved glacial clay, this point could occur in a variation that is not representative for the whole layer. To find out if these structural variations will affect a clays mechanical properties clays from the Stockholm region have been analyzed. The clays water content, liquid limit and clay content has been determined through laboratorial analyzes and then compared with each other. The liquid limit is defined as the water content when a clay is transitioning from plastic to liquid consistency and is determined by the fall-cone method (Axelsson & Mattsson, 2016). The water content is determined through drying in a drying oven and gives the relationship between the soil’s solid mass and the mass of the water (Larsson, 2008). The clay content in a soil sample is determined through hydrometer analysis and gives a value on the amount of clay in relationship to other fractions. The samples which have been studied were of different quality with respect to how distinguishable the varves were and both glacial and post-glacial clays have been analyzed. The result show that it is difficult to analyze differences between light and dark variations and varvs in clays which does not have distinct layering and that vast variations occur in all of the analyzed parameters for both dark and light variations.

Prediction as a tool in engineering has been used in taking right judgement in many of the professional activities. This being the fact, the role and significance of prediction in geotechnical practice needs no emphasis. Bulk of all man made structures are either made of soil or are resting on natural soil, involving large quantities of soil. Thus, it is often necessary for the geotechnical engineer to quickly characterize the soil and determine their engineering properties, so as to assess the suitability of the soil for any specific purpose. Obtaining these properties requires undisturbed samples, which involves time and money, and also elaborate laboratory procedures. Thus, it is desirable to find simpler and quicker methods of testing, using the data of which the engineering properties can be predicted satisfactorily especially so, for preliminary design purposes. Most often this can be achieved from simple tests known as inferential tests, and the engineering properties namely, compressibility, swell/collapse, hydraulic conductivity, strength and compaction characteristics can be obtained from empirical/semi-empirical correlations. The index tests namely the Atterberg limits form the most important inferential soil tests with very wide universal acceptance. These tests are relatively simple to perform and have provided a basis for explaining most engineering properties of soils in geotechnical practice. In this direction, this investigation has been carried out to correlate the engineering properties with the simple index properties and their indices, namely, the liquid limit, plastic limit, shrinkage limit, plasticity index and shrinkage index (liquid limit - shrinkage limit). Any good correlation in the prediction of engineering properties with the index properties will enhance the use of simple test for prediction purposes. This thesis is an attempt towards this direction. It is often necessary to identify the basic mechanisms controlling the engineering properties from a micro-mechanistic point of view and correlate with the index properties, thereby facilitating prediction of engineering properties better. Though attempts have been made in the past to predict the engineering properties of soils from the index properties/indic­es, they are not quite satisfactory. This thesis is an attempt to predict the engineering properties of fine-grained soils from the index properties taking into consideration the mechanisms controlling them. Since, the index properties are used for prediction of engineering properties, the existing methods of determining the same have been examined carefully and critically. It's satisfactory determination is found important because other indices namely plasticity index, Ip and shrinkage index, Is = (wL - ws), are determined based on it. Also the liquid limit is one of the important and widely used parameter in various existing correlations. In this direction, two new methods of determining the liquid limit have been developed, namely (i) absorption water content and liquid limit of soils and (ii) liquid limit from equilibrium water content under Ko-stress. In the absorption water content method, the water absorbed by an oven dried soil pat at equilibrium gives a good correlation with the liquid limit of soils. Here, the water holding capacity at equilibrium goes well with the mechanism of liquid limit, which is also the water holding capacity of a soil at a particular small but measurable shear strength. A good relationship is found to exit between the absorption water content, wA and the liquid limit, wL, and it is given as : WA = 0.92 wL (i) In the second method, namely, the liquid limit from equilibrium water content under K0-stress, which is the equilibrium water content under a Ko stress of 0.9 kPa is found to be equal to the liquid limit obtained from the cone penetration method of determining the liquid limit It is found that this method of determining the liquid limit overcomes the limitations of the conventional methods of determining the liquid limit, also easy to determine with a simple apparatus and has good repeatability. Determination of plastic limit of the soils by the rolling thread method often poses a problem especially when the soil is less plastic. Hence, to overcome this problem, a new method has been proposed to predict the plasticity index in terms of the flow index. The relationship between the plasticity index and the flow index by the cone penetration cup method is found to be better than by the percussion cup method. Since, the cone penetration method of the liquid limit determination is more popular than the percussion cup method, the flow index from the cone method is recommended to determine the plasticity index from the correlation as given below: (/p)c = 0.74 Ifc (ii) Thus, the plastic limit can be determined with the plasticity index, thereby dispensing with the determination of plastic limit by the thread method. The determination of consolidation characteristics form an important aspect in the design of foundations and other earth retaining structures. The determination of consolidation characteristics namely the compression index, the coefficient of consolidation and the coefficient of secondary compression is time consuming. So, researchers have resorted to correlating the compressibility behaviour with simple index properties. While attempts have been made in the past to correlate the compressibility behaviour with various index properties individually, all the important properties affecting the compressibility behaviour has not been considered together in any single study to examine which of the index property/properties of the soils correlates better with the compressibility behaviour, especially with the same set of test results. Number of existing correlations with the liquid limit alone as a primary index property correlating with the compression index have limitations in that they do not consider the plasticity characteristics of the soils fully. The index parameter, shrinkage index, Is has a better correlation with the compression index, Cc and also the coefficient of volume change, mv than plasticity index. Coefficient of consolidation, Cv has also shown to correlate well with shrinkage index than the plasticity index. Even the coefficient of secondary compression, Cαε has shown to have a better correlation with shrinkage index than the plasticity index. However, liquid limit has a poor correlation with all the compressibility characteristics. The correlation of Cc and Cv with shrinkage index, Is is as given below: Cc = 0.007 (Is + 18) (iii) Cv = 3x10-2 (Is)-3.54 (in m2/sec) Further, to reduce the testing time of conventional consolidation test in order to obtain the compressibility characteristics, a new method known as rapid method of consolidation has been proposed, which is very effective in enormously reducing the time of consolidation without sacrificing the accuracy of the end results. The time required in the rapid method of consolidation testing could be as low as 4 to 5 hours to complete the whole test as compared to 1 to 2 weeks as the case may be by the conventional consolidation test. Using any curve fitting procedure the degree of consolidation, U for any pressure increment can be found out. Thus, the effective pressure at that stage can be calculated and further the pressure incremented without further delay. This procedure is repeated for every pressure increment with a load increment ratio of unity till the desired pressure level is reached. Even for a highly compressible soil like BC soil with a liquid limit of 73.5 %, the consolidation test could be completed within 5 hours by the rapid method, without any sacrifice of the accuracy of the results as compared to 7 days by the conventional method to reach a pressure of 800 kPa. Hydraulic conductivity is one of the basic engineering properties of soils. Of late hydraulic conductivity of fine-grained soils has assumed greater importance in waste disposal facilities. From the present investigation it is found that hydraulic conductivity with water for each pair of soils having nearly the same liquid limit but different plasticity properties is found to be vastly different, but found to correlate well with shrinkage index. A method to predict the hydraulic conductivity of fine -grained soils as a function of void ratio is proposed with the use of shrinkage index as given below: k = C [ ] (in m/sec) (v) 1 + e C = 2.5 x 10-4 (/s)-5.89 and n = 4 (vi) It has also been brought out that as the dielectric constant of the pore fluid decreases; there is a drastic increase in the intrinsic permeability of soil. These changes are attributed to the significant reduction in the thickness of diffuse double layer, which in turn is mainly dependent on the dielectric constant of the pore fluid. The quantification of the change in the hydraulic conductivity with the change in the pore fluids of extreme dielectric constant, i.e., from water to carbon tetrachloride could be expressed in terms of the volume of water held in the diffuse double layer and the same has a good correlation with shrinkage index. With the advancement in the knowledge of the engineering behaviour of fine-grained soils, there is an increasing trend toward larger involvement of fine-grained soils in earth structures and foundations. Though extensive work has been done in the past to understand the swelling behaviour of expansive soils and the mechanisms involved therein, it is yet not satisfactory. From the literature it can be seen that lot of work has been done to correlate the swell potential with various physical properties. The simple means of identifying the swelling type of soils is by means of free swell tests with the ratio of free swell with carbon tetrachloride to the free swell of water. The same has found to correlate well with the percent swell/collapse of the ten soils used in the present investigation. However, it was found that shrinkage index has a better correlation with the swell/collapse behaviour of fine-grained soils, compared to the liquid limit or the plasticity index. In this study, it is also shown that neither the liquid limit nor the plasticity index can qualitatively describe the swell/collapse behaviour of fine-grained soils. This has been attributed primarily to two different mechanisms governing montmorillonitic and kaolinitic soils separately. Even swelling pressure has shown to have a good correlation with shrinkage index. It is found that the compression index of the samples consolidated from the swollen condition correlates well with the shrinkage index. Laboratory determination of the compaction characteristics are very much important for use in earth work constructions. It is found that only the plastic limit bears a good correlation with the compaction characteristics namely optimum moisture content and maximum dry unit weight. This conclusion is also supported by the data from the literature. The correlations are given as: OMC = 0.92 wp (in percent) (viii) and ydmax = 0.23 (93.3 - wp) (inkN/m3) (ix) Liquid limit, plasticity index and shrinkage index do not bear any correlation with the compaction characteristics. It is quite possible that, the plastic limit, which is the optimum water content of a saturated soil at which it behaves as a plastic material, and thus can be moulded to any shape, thereby the soil can be compacted or moulded to the densest possible state at that water content. Hence, possibly the good correlation. A simple method to predict the compaction curve is proposed based on the plastic limit of the soils. Of all the important engineering properties, both volume change (compressibility and swelling) and hydraulic conductivity have good correlation with the shrinkage index. However, the compaction characteristics correlate well with the plastic limit. Herein, an hypothesis is proposed to possibly explain why shrinkage index has shown to be a better parameter to correlate with most of the engineering properties with the exception of the compaction characteristics. The liquid limit is a parameter which takes part of the plasticity characteristics of a soil. Recently it has been well brought out that shrinkage limit is primarily a function of how the varying grain sizes are distributed in a soil. Thus, shrinkage limit takes care of the gradation of the soil fractions in it. Thus, by considering the shrinkage index, which is the difference of the liquid limit water content on one end and shrinkage limit water content on the other end, the primary physical properties of the soils namely the plasticity and the grain size distribution are considered. This possibly explains the good correlation of shrinkage index with the engineering properties of fine-grained soils. However, compaction being a moulding of the soils into a compact state, it has a good correlation with the plastic limit, which is the optimum water content of a saturated soil at which it behaves as a plastic material, and thus can be moulded to any shape, thereby the soil can be compacted or moulded to the densest possible state at that water content. Hence, the good correlation. As the present investigation gives the correlative equations to predict the engineering properties of fine-grained soils from the appropriate index properties, which are obtained from simple and quick laboratory tests, it is hoped that this will go a long way in being a handy tool for a practicing geotechnical engineer in the preliminary assessment of fine-grained soils and thereby take appropriate judgement in various aspects of geotechnical constructions with it.

Previous thread rolling methods for the plastic limit are shown to be inadequate and inaccurate. Alternative methods for the plastic limit are shown to be imprecise and unreliable. The strength-based concept and use of the fall-cone test to determine the plastic limit are shown to be flawed. An apparatus that replicates Atterberg’s rolling technique, devised and developed by the author, is described, referred to as the Barnes Apparatus. A thread of soil is rolled between two plates configured to permit extrusion and reduction of diameter with much less operator interference than with the standard test and judgement of the crumbling condition is eliminated. Using a loading device nominal stresses are derived and from dial gauge readings diametral strains are determined for each rolling traverse of the soil thread. Toughness has previously only been studied in an empirical or qualitative manner. From plots of nominal stress vs. strain the workability or toughness of the plastic soil is determined as the work/unit volume. The apparatus and test are appropriate to a wide range of soils. Threads are tested over a range of water contents from near the sticky limit to the brittle state. Good correlations between toughness and water content display an abrupt ductile-brittle transition and give an accurate definition of the plastic limit. From the correlations useful properties are obtained such as the maximum toughness at the plastic limit, the toughness limit, the water content at zero toughness, the stiffness transition, the toughness coefficients, the toughness index and the workability index. An investigation into the significance of the soil thread diameter of 3 mm in the standard plastic limit test has found that as the water content of a soil reduces it undergoes a transition from fully plastic, to cracked, to brittle, largely regardless of the diameter of the thread. It is recommended that the 3 mm diameter requirement is withdrawn from the standard test procedure as unnecessary and emphasis placed on observing the behaviour of the soil thread as it is rolled by hand. A review of the relationship between the clay matrix and the granular particles in a soil has found that the linear law of mixtures and activity index are appropriate only at high clay contents. The terms granular spacing ratio and matrix porosity are introduced to explain the effect of the granular particles on the toughness and plastic limit. An analysis confirms that with small diameter soil threads large granular particles affect the results disproportionately. An aggregation ratio term is introduced to explain the change in toughness in the clay matrix as its water content reduces towards the plastic limit. To assess the effect of granular particles in a clay matrix on the toughness and plastic limit the results of tests conducted on mixtures of a high plasticity clay and silt, and sand particles of two different sizes are discussed. Smaller particle sizes are found to have a greater effect on reducing the toughness and the plastic limit of the clay. In the ceramics industry mixing different clays together to obtain suitable properties is common. The toughness and plastic limits of two pairs of mixed clays do not follow the linear law of mixtures but are dependent on the total clay content and the content of a dominant clay mineral.

This diploma thesis deals with the issue of the determination of the frost susceptibility of soils in the subgrades of road structures. The theoretical part compares the ways of testing the frost susceptibility in the Czech Republic and other selected countries of the European Union. Furthermore, it also deals with the development of the frost susceptibility index in the Czech Republic. The empirical part focuses on the laboratory testing of the frost susceptibility of the given sample of soil by the direct frost heave method. Moreover, it also deals with the simulation of penetration of frost by the subgrade and the possibility of shortening the length of the freezing during the direct testing the frost susceptibility.