Sub-surface soil pollution by various processes with high concentration of contaminants can significantly alter geotechnical properties of soils causing unexpected failures of structures founded on them. The changes can occur due to alteration in soil water interaction processes and/or by intense chemical interactions leading to mineralogical and microstructural changes. Behaviour of soil upon contamination with alkali pollutant is one of the major concerns faced by the geotechnical researchers in recent years. In the present study an attempt has been made to understand the role of mineralogical and morphological changes on the volume change (swelling and compressibility) behaviour of soils by prolonged interaction with caustic alkali pollutant. Based on the results it has been proposed to develop remedial measures to nullify and/or control the detrimental effects. A comprehensive experimental program has been planned to achieve these objectives. The experimental investigations carried out and results obtained are presented in eight chapters as follows. The broad outline of thesis is given in Chapter 1. A detailed review of literature on the type of phyllosilicate minerals present in various soils is presented in Chapter 2 with a view to select most common soils for the study. Various sources of contaminants and their effect on the properties of soils have been summarised. Present understanding on the mechanisms leading to changes in the soil properties has been elucidated. The occurrence of alkali contamination has been reviewed in this chapter which enabled to select the ranges of alkali concentration for the study. Based on the review of various methods employed to improve the soil behaviour, the use of salt solutions such as potassium chloride (KCl) and magnesium chloride (MgClB2B) and pozzolanic fly ash has been considered to counteract the alkali effects. Based on this detailed survey, the scope of the present investigation has been elaborated at the end of the chapter. Chapter 3 presents different materials used and various methods adapted in the current study. Three soils having different mineralogy have been used in this study to bring out the effect of alkali solutions on their volume change behaviour. While two soils were classified as CH, the third one was of CL. The CH soils used in this study are called Black Cotton Soils in India. One soil contained predominantly mixed layer illite-smectite mineral (BCS I) and the other contained predominantly montmorillonite mineral (BCS M). The locally available CL soil used is referred as red earth (RE) whose predominant mineral is kaolinite. Alkali solutions of concentration ranging from 1N to 4N are prepared using sodium hydroxide pellets (NaOH). Slat solutions viz. potassium chloride and magnesium chloride and pozzolanic fly ash obtained from Neyveli thermal power plant (NFA) are used as additives. Procedures to determine the geotechnical properties of the soils such as Atterberg limits, specific gravity, grain size distribution and compaction characteristics are given in this chapter. Procedures for identifying the mineral and microstructure of the soils such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) are also presented in this chapter. Standard oedometer tests with fixed ring apparatus were performed to study the volume change behaviour of soils under various conditions. Volume change behaviour of soils in the presence of alkali solutions is presented in Chapter 4. In order to assess the effect of alkali solution on the volume change behaviour of soils it is necessary to study their behaviour in water. Relatively very high swell was observed in BCS M, whereas the swell in RE and BCS I soil specimens was very low and moderate respectively. Adsorption of water to form diffuse double layer near the negative surface of clay mineral particles leads to swelling in soils. The thickness of the double layer depends on the cation exchange capacity of soil. Higher cation exchange capacity leads to development of higher thickness of double layer thereby inducing swell. The higher is the swell the higher would be the compression. The effect of different concentrations (1N, 2N and 4N) of alkali solutions on volume change behaviour of three types of soil is presented in this chapter. All the three soils studied, irrespective of their mineralogical composition, exhibited high swell when contaminated with alkali solution compared to water. However, the extent and nature of swell varied both with the type of mineral present in the soil and concentration of sodium hydroxide solution. The swell in BCS I increases with increase in the concentration of the alkali solution. In 1N alkali solution the high swell occurred is due to the breaking up of interstratified mineral into constituent minerals initiated by the leaching of potassium from soil due to high pH. In 2N and 4N alkali solutions, the observed high swell occurs in two stages: the first stage of swelling is due to breaking up of interstratified mineral into constituent minerals initiated by the leaching of potassium from soil due to high pH, and the second stage of swelling is due to the formation of new minerals (Zeolite P in case of 2N NaOH and Sodalite in case of 4N NaOH). The nature of swell is influenced by the formation of minerals depending on the concentration of alkali solution. Thus the studies clearly indicate that the swelling is due to the release of potassium from soil at higher pH and due to mineralogical changes depending upon the concentration of alkali solution. Confirmative tests were conducted to support the release of potassium during first stage of swelling and mineralogical alteration after second stage of swelling. The high swell in BCS M becomes higher in 1N alkali solution. The increased swell in the soil with 1N alkali solution is due to increase in the ion exchange capacity of soil at higher pH. The swell which is very high with 1N alkali solution decreases with 2N alkali solution. With increase in concentration of alkali solution to 2N, the increase in the negative charges due to alkalinity becomes less and the swell decreases due to dominant influence of electrolyte effect. With increase in the concentration of alkali solution to 4N, both these influences become less and the amount of swell remains the same. Significant increase in the amount of swell is observed with alkali solution even in non-swelling red earth. The nature of swell as well as the formation of minerals is not altered by the change in the concentration of alkali solution. At any concentrations of alkali solution the observed swell is noticed in two stages – very small first stage of swell due to lower ion exchange capacity and considerable second stage of swell due to the formation of new mineral (Sodalite) with any concentration of alkali solution. It has been observed that the normal hyperbolic swell – compression relationship does not apply for the alkali contaminated soils. The higher swell does not result in higher compression, as the swollen soil remains fairly incompressible. Analysis of the results and detailed studies on micro-structure and mineralogy of soils bring out mechanism of alkali effects. Comparing the swell behaviour of soils with alkali solutions brings out the relative importance of various mechanisms proposed for induced heave. The effect of salt solutions used viz., potassium chloride and magnesium chloride to restrict the influence of alkali solution on the volume change behaviour of BCS I is presented in Chapter 5. These salts react with alkali solution to form partly soluble potassium hydroxide (KOH) and sparingly soluble magnesium hydroxide (Mg(OH)B2B) respectively. Presence of ionic potassium can bring out potassium linkages, by bridging potassium ion between the unit layers of expansive minerals reducing the swell. Magnesium ions can restrict swell, by replacing the monovalent exchangeable ions present in soil and/or by formation of magnesium hydroxide which is a weak cementing agent. The effect of potassium hydroxide on the volume change behaviour of soil has been studied and the results clearly indicate that fixation of potassium is facilitated by high pH of KOH solution. Addition of potassium chloride has partially controlled the alkali induced heave in soil. Of the two stages of swelling observed in soil in the presence of 4N alkali solution, only the first phase of swelling is reduced which may be due to electrolyte effect and/or due to fixation of potassium. The second phase of swelling that occurs in soil due to mineralogical changes can not be controlled with the use of potassium chloride. Addition of magnesium chloride salt solution also reduced the effect of alkali solution mostly due to suppression of thickness of diffuse double layer that develops near clay surface. The nature of reduction in the swell of alkali solution during the two stages by magnesium chloride is similar to that of potassium chloride. The partial reduction in swell of soil in the presence of salt solutions leads to reduction in the compressibility of soil. Detailed data and analysis, presented in this chapter, bring out the role of microstructure and mineralogy on soil behaviour. The abnormal volume changes due to mineralogical changes affected by high concentration of sodium hydroxide could not be controlled with salt solutions, attempts are made to utilize fly ash to control the alkali induced heave. The pozzolanic compounds produced by hydration of compounds presented and/or produced by lime silica reactions can bind the soil particles controlling the swelling. The results on the effectiveness of fly ash on BCS I soil are presented in Chapter 6. The physical and chemical properties of fly ash along with the mineralogical composition and the microstructure of the fly ash are also presented in this chapter. Before studying the effect of fly ash to control the volume change behaviour of soils in presence of alkali solutions, the effect of alkali solutions on the volume change behaviour of fly ash itself has been studied. The results showed no noticeable changes in swell and compressibility of fly ash, encouraging its use for controlling the alkali induced swell. The ability of different percentages (10%, 20% and 50%) of fly ash to control alkali induced volume changes in soil with varying concentrations of alkali solutions, viz., 1N, 2N and 4N has been studied. The results indicate that the addition of fly ash effectively reduces alkali induced swell in BCS I. The effectiveness of fly ash increases with increase in its content. The reduction in swelling of soil is partially due to replacement of soil with fly ash and mainly due to cementation of soil particles by pozzolanic compounds produced. More than 25% of fly ash is generally required to significantly reduce the swell in alkali solutions. The reduction in swell with addition of fly ash also leads to lower compressibility of soil. The role of microstructure and mineralogy in controlling the volume change behaviour are also presented in this chapter. The effectiveness of fly ash in controlling the volume changes in RE and BCS M due to alkali solutions are studied in Chapter 7. The addition of fly ash completely eliminates the swelling in both the soils. The reduction in swelling up on addition of fly ash is essentially due to efficient binding of particles by pozzolanic reaction compounds. Addition of even 10% of fly ash is sufficient in completely arresting the swelling of RE and BCS M by alkali solution. Detailed data and analysis of the results to bring out the role of microstructure and mineralogy on the behaviour of soils are presented. It is clear that relatively higher amounts of fly ash is required to control the alkali induced heave in BCS I than in other soils at higher concentrations of alkali solution. The major conclusions from the study are presented in Chapter 8. The thesis demonstrates that alkali contamination alters mineralogy and morphology of soils affecting the volume change behaviour significantly. The study also brings out that fly ash can control the undesirable swell that occurs in most types of soils by cementing the soil particles to resist swelling. Though the amount of fly ash required to control the alkali induced heave varies, 25% of fly ash is often sufficient.

Le traitement des sols est une technique connue qui a largement été utilisée dans les constructions ferroviaires et routières. Il améliore la maniabilité des sols en réduisant la teneur en eau et en améliorant les performances hydromécaniques par renforcement et lien des agrégats du sol. Cependant, la durabilité des sols traités reste une question ouverte, elle constitue l'objectif principal du projet ANR TerDOUEST (Terrassements Durables – Ouvrages en Sols Traités, 2008-2012).La présente étude fait partie des travaux réalisés dans le cadre du projet TerDOUEST, et traite de l'effet de la taille des agrégats sur l'évolution de la raideur (Gmax) des sols fins provenant d'Héricourt (70) et traités à la chaux et/ou au ciment, à l'aide de la technique piézo-électrique (bender element). Dans les conditions de laboratoire, quatre tailles d'agrégats ont été étudiées (Dmax = 0.4, 1, 2 et 5 mm). Afin d'obtenir des tailles d'agrégats souhaitées, les sols ont d'abord été séchés, broyés puis tamisés à une taille désirée. Les sols ont ensuite été ramenés à la teneur en eau souhaitée, mélangés au liant hydraulique (chaux et/ou ciment) puis compactés du côté sec et du côté humide de l'optimum du Proctor normal, tout en conservant la même densité sèche. Les mesures de Gmax des sols traités ont été réalisées pendant la cure et pendant l'application de cycles humidification/séchage. Dans les conditions du terrain, qui correspondent au remblai expérimental d'Héricourt, les tailles des agrégats sont nettement plus élevées : Dmax = 20 et 31.5 mm pour le limon et l'argile, respectivement. Les résultats montrent que le comportement hydromécanique des sols traités est fortement influencé par la taille des agrégats, que les sols soient argileux ou limoneux, préparés en laboratoire ou bien dans les conditions du terrain : plus la taille des agrégats est élevée, plus la raideur diminue avec le temps de cure et moins les sols résistent à la succession de cycles humidification/séchage. Une forte hétérogénéité des sols in-situ a aussi été identifiée clairement. Un modèle hyperbolique a été développé afin de permettre l'application des résultats obtenus en laboratoire à ceux obtenus dans des conditions de terrain, étant donné l'effet de la taille des agrégats. La comparaison entre le modèle de prédictions et les mesures expérimentales démontre la performance du modèle proposé, à condition d'utiliser les valeurs moyennes des données expérimentales afin de minimiser l'effet de l'hétérogénéité du sol / Soil treatment is a well known earthwork technique which has been widely used in constructions of railway and highway substructures. It can improve the workability of soils by lowering their water contents and improve the hydro-mechanical performance by reinforcing and binding the soil grains/aggregates. However, the durability of the treated soils is still an open question. It constitutes the main objective of the ANR project TerDOUEST (Terrassements Durables - Ouvrages en Sols Traités, 2008 - 2012).The present study is part of the works in TerDOUEST project, and deals with the aggregate size effect on the stiffness (Gmax) development of lime and/or cement treated fine-grained soils from Héricourt using bender element technique. In the laboratory conditions, four aggregates sizes were accounted for (Dmax = 0.4, 1, 2 and 5 mm). To prepare an aggregate size, the soils were first air-dried, crushed and sieved through a target sieve. The soils were then brought to a desired water content, mixed with additive (lime and/or cement) and compacted both dry and wet of optimum of normal Proctor by keeping the same dry density. The Gmax measurements were performed during curing and during application of wetting/drying cycles. In field conditions that refer to the experimental embankment in Héricourt, the aggregates size is significantly larger: Dmax = 20 mm and 31.5 mm for the silt and the clay, respectively. Cores samples were taken from the embankment at two different times and the Gmax measurements on core specimens were performed. The results show that the hydromechanical behaviour of the cementitious treated soils is strongly influenced by the aggregates size for the treated silt and clay prepared in both laboratory and field conditions: the larger the aggregates, the lower the Gmax and the resistance to wetting/drying cycles. The high heterogeneity of the in-situ soils was also clearly identified. A hyperbolic model was developed enabling up-scaling the results in laboratory conditions to those in field conditions by considering the effect of aggregate size. Comparison between the model predictions and experimental measurements shows the performance of the model proposed, provided that the mean values of experimental data are used to minimize the effect of soil heterogeneity

The objective of dissertation is to find the approaches for processing the data extracted from the reports that document the performing of acceptance tests of ground anchors. The purpose of this activity is to allow further utilization of this data for designing practice. 795 test records were collected. It is essential for the correctness of analysis, that the whole anchor bond must be placed in homogeneous material. The records for anchors that don’t fulfilled this condition were removed. The set of 379 records of anchors installed in six different soil types during construction work in Czech Republic remained. All those anchors were tested according the demands of european standard ČSN EN 1537:2001, valid until 2013. The methodics based on the mathematical statistics, regression analysis and probability methods were compiled during solving the task defined above. The major result of data processing that was performed via methodics based on combination of mathematical statistics and probability simulation methods is the set of bond shear stress parameter values elaborated for variety of soil types. The regression model for determination of the force-displacement curve and the model predicting the creep behavior of loaded ground anchor were constructed, where the creep value is dependent on the tendon bond length, tendon free length and on the level of prestressing force. The description of full-scale experiment, whose results were used for verification of assumptions incorporated in relevant methodics, is included. The example of determining the probability of failure of anchored structure using the stochastic simulation technique is mentioned also, where the previously obtained results are used as input values for this calculation. Moreover, the software application serving for automatization of processes associated to conducting of the tests of ground anchors and to creating the test report is introduced.

A series of static lateral load tests were conducted on a group of fifteen piles arranged in a 3x5 pattern. The piles were placed at a center-to-center spacing of 3.92 pile diameters. A single isolated pile was also tested for comparison to the group response. The subsurface profile consisted of cohesive layers of soft to medium consistency underlain by interbedded layers of sands and fine-grained soils. The piles were instrumented to measure pile-head deflection, rotation, and load, as well as strain versus pile depth.

This diploma thesis is focused on the properties of unsuitable and conditionally unsuitable fine-grained soils after a one-stage or two-stage treatment by using a binder. The theoretical part occupies with problematical properties of the fine grained soils in a subgrade and a possible technology of the change of these properties. The laboratory testing of treated soils is described and a practical technology of the one stage and two-stage stabilization. In the practical part the fine grained soils are treated by one-stage or two-stage stabilization. For the one stage stabilization the cement is used, for the two-stage stabilization the properties of the soil are improved by lime and then the soil is stabilized by cement. The treated soils are laboratory tested, the initial bearing index IBI, California bearing ratio CBR, unconfined compressive strength and frost susceptibility is tested. Based on the results of the laboratory tests the benefit of the two-stage stabilization is measured.