Spatial variability in swelling of aggregated expansive clays

Bulletin of Engineering Geology and the Environment, 2013

The main objective of this paper was to study the swelling properties of Regina clay. The deposit comprises a topsoil (surface to 0.3 m depth), an expansive clay (0.3-8 m), and a bottom till (8-9 m). High liquid limit (70 ± 15 %) and plastic limit (33 ± 4 %) indicated high water retention and adsorption capacity for the clay. Irrespective of the cover type (vegetation and cracked road), the field water content in summer closely matched the plastic limit. The clay was characterized by medium-tohigh swelling that was best predicted by SP = 0.16 (I p) 1.188. The soil had 51 % clay minerals including smectite (32 %), illite (7 %), kaolinite (5 %), and chlorite (3 %). With a CEC of 40 cmol(?)/kg, Ca 2? and Mg 2? were found to be the main exchangeable cations: the specific surface area was 50 m 2 /g. The SP and P s for a 1.2 m deep sample measured 12 % and 260 kPa, respectively, and the estimated surface heave of 180 mm gradually diminished to 3.6 m depth. These values matched well with consistency-based correlations. Keywords Expansive soils Á Geotechnical properties Á Swelling potential Á Heave prediction Á Clay mineralogy Résumé L'objectif principal de cet article était l'étude des propriétés de gonflement de l'argile de Regina. La formation géologique comprend un niveau supérieur (de la surface à 0,3 m de profondeur), l'argile gonflante (de 0,3 m à 8 m de profondeur) et un niveau inférieur morainique (entre 8 m et 9 m de profondeur). Les fortes limites de liquidité (70 ± 15 %) et limites de plasticité (33 ± 4 %) indiquaient une forte capacité de rétention d'eau et une forte capacité d'adsorption du sol argileux. Indépendamment du type de couverture (végétation ou route fissurée), la teneur en eau in situ, en été, correspondait à la limite de plasticité. Le sol argileux présentait un potentiel de gonflement moyen à élevé qui était bien prévu par la relation SP = 0,16 (Ip) 1,188. Le sol argileux contenait 51 % de minéraux argileux dont des smectites (32 %), de l'illite (7 %), de la kaolinite (5 %) et de la chlorite (3 %). Avec une CEC de 40 cmol(?)/kg, les ions Ca 2? et Mg 2? se sont révélés être les principaux cations échangeables. La surface spécifique était de 50 m 2 /g. Le potentiel de gonflement et la pression de gonflement pour un échantillon prélevé à 1,2 m de profondeur donnaient respectivement 12 % et 260 kPa. Le soulèvement de surface était estimé à 180 mm pour diminuer progressivement à 3,6 m de profondeur. Ces valeurs correspondaient bien aux relations établies. Mots clés Sols gonflants Á Propriétés géotechniques Á Potentiel de gonflement Á Prévision de soulèvement Á Minéraux argileux

Applied Clay Science, 1996

The swell-shrinkage behavior of expansive clays was investigated in four soils of different plasticity cyclic swelling. To simulate drying temperatures typical of site conditions, two shrinkage schemes were adopted, partial and full shrinkage. After each cycle, the expansive characteristics of the soils were assessed. Furthermore, the physical and microstructural changes due to cyclic swelling were also studied, respectively, through an ultra-sonic investigation and scanning electron microscope observations. The results showed that cyclic swelling and shrinkage has a marked influence on the expansive behavior of clays. Generally speaking, a decrease in the swelling ability of the clays, corresponding to a reduced water absorption capability, was observed when the soils were alternately wetted and partially shrunk. On the other hand, an increase in the swelling potential was noted when the soils were fully shrunk. In either case, equilibrium can be attained after several cycles. As the number of cycles increase, further destruction of large aggregates and disorientation of structural elements takes place. Approximately after the fifth cycle, the fabric becomes almost disoriented, consequently further changes in expansibility disappear. The scanning electron microscope analysis showed that for partial shrinkage the structural elements exist mainly as edge to face contacts with a tendency to form a turbulent flocculated system while a horizontal clay particle orientation was observed when the specimens were cyclicly wetted the fully shrunk. In parallel, the ultrasonic wave transmission velocity

Abstraet-The limitations of existing methods for the prediction of swelling behavior of compacted softs are examined. Both the purely theoretical approach and the purely empirical approach are found to be inadequate. The present study is based on a semi-empirical approach in which a model of swelling behavior is developed leading to equations relating swelling potential or swelling pressure of a compacted soil to its plasticity index, clay content and initial molding water content. The model is based on the concepts of the diffuse double layer, modified by introducing empirical constants to account for elastic swelling effects and other limitations involved in the direct application of double layer theory to real soils. The empirical constants are evaluated from the results of experimental investigations carried out on a large number of soil samples representing a wide variation of clay content as well as consistency limits.

MATEC Web of Conferences, 2018

The shrinking and swelling is a very common phenomenon in the world, mainly in arid and semiarid areas. The construction on these soils often requires a study of the risk of swelling, in advance. The emergence of this phenomenon in soils is caused primarily by the presence of swelling clays and water. The risk is most significant when the rate of the expansive minerals, such as bentonite, is important. Several researchers have studied the relationship between the percentages of swelling minerals and soil swelling potential. The researchers have shown the difficulty of characterization, because of the complexity of the phenomenon under natural conditions, where several other phenomena occur, and which are not considered in laboratory experimentation. This article addresses the characterization of several soils, with different swelling rates from the physical, chemical and mechanical tests. It shows the relationship between the quantity of swelling minerals and some site conditions, such as water content and consolidation stress, on the ability of soil to swell. This work aims to establish empirical relationships between the percentage of swelling minerals and soil swelling potential.

Journal of Performance of Constructed Facilities, 2011

Field measurements of foundation movements in central Mississippi have revealed design issues involving expansive soils. At one building, field measurements of the first floor slab at 14 locations show that heaving occurred at a steady rate during part of an extensive drought. The steady rate was maintained throughout the final 21.5 months of a 23.5-month study period following a record drought that occurred at the beginning of the study. The average change in the movement rate was 2.9 mm ͑0.11 in.͒ per year over the last 21.5 months. Median movement rates for all the pins varied from 25 mm ͑0.98 in.͒ per year to 1.8 mm ͑0.07 in.͒ per year excluding the measurements made during the first part of the drought. Elevation surveys at another facility show how the rate of heave is influenced by geologic variations. These surveys also show how the depth of clay ͑from the surface͒ influenced heave and how differential movements of a structure are produced from these variations in geology. Design procedures for kind of movement are discussed.

Engineering Geology, 2004

Soil swelling is a term generally applied to the ability of a soil to undergo large changes in volume due to increased moisture content. Several commonly used swelling potential indices, namely Atterberg limits, coefficient of linear extensibility (COLE), cation exchange capacity (CEC) tests and saturated moisture content test (SP) were used to estimate the swelling potential of a group of soil samples representing the whole range of swelling potential. Correlations between the various indices and the potential volume change were obtained and used to determine the potential of each to be included in the establishment of an expansive soil index (ESI), a summation of the indices. The outcome is a set of reliable soil-swelling indices for different levels of risk.

UNIVESITARIA SIMPRO 2021 May 27-28, 2021, Petrosani, Romania., 2021

Swelling and shrinking properties refers to significant positive or negative variations of volumes due to absorbtion or dessication of water in fine soils under natural or anthropic regime of moisture. These physical phenomena are worldwide spread and had important engineering consequences with associates cost of damages of several billion annually in all climate areas. In spite of the fact that these geotechnical properties are studied for more than eight decades, the particularities of these peculiar relations between water, mineral composition and geomechanical behavior are still unrevealed entirely. In Romania, swell/shrink soils are reported in all regions at different depths, but rarely related to geotechnical engineering accidents such as slope slides or road failures. This work presents some obvious relations between the hydrogeological structure, the presence of "large swell/shrink soils", their mineralogical composition and geomechanical properties and the ubiquitous landslides on Peri Carpathians Hills. Large infrastructure projects offer the opportunities to put into evidence the swelling properties of Upper Pliocene-Lower Pleistocene deposits, which supports the Holocene alluvial deposits of Argeş River. Analyzed samples allow us to define some basic correlations between plasticity index, colloidal fraction, dry density, swelling pressures or free swelling and mineralogical composition.

Volumetric changes (usually swell) of expansive soils in presence of water are undesirable from stability reasons. Swell and Swelling pressure of an expansive soil is primarily dependent on the initial dry unit weight or void ratio and also on the moisture content. In this study, attempts have been made to study the effect of introducing varying number of vertical drains into the compacted soil at varying initial dry densities on the swell and swelling pressure behavior. Both percent swell and the swelling pressure are significantly influenced by the presence of vertical drains (facility of water availability). The percent swell versus time relationship could be identified as a rectangular hyperbola, facilitating the prediction of ultimate percent swell. This is advantageous to predict the swell from the data obtained from the initial stages of the swell test and the experiment could be terminated without continuing till equilibrium conditions are reached. This concept was also extended to predict swelling pressure determined by constant volume method. Irrespective of the presence or absence of drains, the density effect on rate of secondary swelling and consolidation behavior of swollen sample was found to be almost the same for all testing conditions used in this study

Determination of swelling potential is quite important in design of foundations on expansive soils. In this paper an attempt has been made to develop a correlation for Swelling Potential, Sq accounting both soil state and soil type representative parameters. The soil state is reflected by placement conditions fac-tors namely Moisture Content, Dry Density, Void Ratio and Surcharge Pressure whereas the soil type is re-flected by the compositional parameters namely Plasticity Index and Clay Content. The Swelling Potential was measured for compacted samples prepared at different water contents and dry densities. Specimens were allowed to swell under various surcharge loads. Analysis of the experimental results demonstrates very clearly a strong linear relationship of Sq with the Factor of initial soil state, Fi, combination of water content, dry den-sity and void ratio. The coefficients of this linear relationship (i.e. constant and slope) were found to depend on clay content, plasticity index and surcharge pressure. It is shown that predicted values of Swelling Potential using the developed equation agree closely with the experimental results of this study and those reported in the literature. KEYWORDS: Swelling Potential, Placement Conditions, Initial State Factor

2015

Expansive soils are problematic due to the extensive damages they may cause to structures and infrastructure. This paper presents results from a case study conducted in an area (Irbid, Jordan) that is characterized by a surficial formation of highly expansive soil. A school building suffering from damages that are attributed to the shrinkage of the soil layer under the foundation was investigated. The interaction between the expansive clay soil layer and the structure was studied through diagnostic investigation of the existing cracks, the properties of the foundation ground, and the climatic and other relevant stratigraphical factors. The results of this study indicated that the structural damages in building members (columns, beams and footings) were mainly due to the swelling gradient. Remedial measures were proposed to rehabilitate and strengthen the structure and prevent further damages.