Swell-shrink Behavior Research Articles

Geotechnical characterization of the quaternary alluvial deposits in Tunis City (Tunisia)

Tunis City is always in perpetual extension. The urban extension takes place in areas covered by quaternary alluvium. To evaluate the spatial variability of geotechnical parameters, 190 boreholes and in situ tests, across the quaternary deposits, were selected with a series of physical properties and mechanical parameters. To accomplish this research, the adopted approach was divided into four steps: (1) data collection; (2) geotechnical data georeferencing; (3) interpolation methods and (4) establishment of maps showing the spatial variability of the geotechnical parameters. Results of this study show that the quaternary deposits provide high water infiltration capacity and form the main aquifer of the study area. The low topography in Tunis City emphasizes the problem of flooding. The presence of sensitive clay causes a swelling–shrinkage behavior of the soil if the clay is dry. The disorders and damages caused by the swelling clay are especially located in the Ksar-Said Bardo–Mannouba, in Bab Saadoun, in the eastern part of Sebket Essijoumi and in the southwestern side of Tunis lagoon. On the other hand, in situ tests show that quaternary deposits contain strong shallow foundation level and vary from 0 to 5m of thickness. These levels are made up by sand, tuff and hard clay. Muddy soils, in the Tunis City and its surrounding area, have a poor geotechnical characteristics and cause differential and absolute risk of settlement. The good bedrock in these locations is defined by muddy and sand levels and it exceed 60m of depth. The existence of a higher concentration of gypsum causes local disorders such as the Henchir El Yahoudia site.

Swelling behaviour of GPA-reinforced expansive clay beds subjected to swell-shrink cycles

Granular pile-anchor (GPA) technique has been found to be an innovative foundation technique for expansive clays posing the dual problem of swelling and shrinkage. Swelling occurs during absorption of water and shrinkage during evaporation of water. Generally, in field expansive clay beds, swelling takes place during rainy seasons and shrinkage during summers. GPA is a recent innovative foundation technique devised to ameliorate the dual swell-shrink problem of structures founded on expansive clay beds. The other innovative techniques are drilled piers, belled piers and under-reamed piles. Laboratory scale model studies and field scale experiments on GPAs yielded useful results and revealed that swelling of expansive clay beds was effectively controlled by GPA technique. Studies on swell-shrink behaviour of GPA-reinforced clay beds have not been performed so far. This paper presents results obtained from laboratory scale model studies on GPA-reinforced expansive clay beds subjected to alternate cycles of swelling and shrinkage. The data presented in this paper pertain to the swelling of test clay beds under the influence of three swell-shrink cycles (N) spanning a time period of 300 days. The test clay beds were reinforced with varying number of GPAs (n = 0, 1, 2 and 3). Heave (mm) in a given swell-shrink cycle decreased with increasing number of GPAs. Further, for a given number of GPAs (n), heave (mm) also decreased with increase in depth from the top of the clay bed. It was found that the resultant thickness of the clay bed (Hr) for swelling increased with increasing number of cycles. However, the percentage heave (ΔH/Hr) decreased as the number of swell-shrink cycles (N) increased.

Swell–shrink behaviour of lime precipitation treated soil

Previous investigation showed that sequential mixing of calcium chloride and sodium hydroxide solutions with an expansive soil resulted in lime precipitation in the soil mass, which controlled the swelling potentials and increased the unconfined compressive strength of treated specimens through strong modification and pozzolanic reactions. However, expansive soils in the field are subjected to cyclic wetting and drying due to environmental conditions, which affects the swell–shrink behaviour. Therefore, the present investigation examines the efficacy of the lime precipitation technique in controlling the swell–shrink potentials and strength characteristics of expansive soils subjected to cyclic wetting and drying. Expansive soil is mixed sequentially with different concentrations of calcium chloride and sodium hydroxide solutions to yield a range of lime precipitation contents, and cured for different time periods. The cured specimens were subjected to cyclic wetting and drying in modified odeometer cells, and the swell–shrink potentials were monitored. The unconfined compressive strength of cured specimens was also determined after different cycles of wetting and drying in a sand bath. The laboratory results showed that the second swell potential was the maximum for untreated and lime precipitation treated specimens, in comparison with other wetting cycles. The equilibrium state was reached after about four to five cycles of wetting and drying. The equilibrium bandwidth reduced as the percentage lime precipitation and curing period increased. The unconfined compressive strength reduced with wetting and drying cycles, which indicated the loss of cementation after one wetting and drying cycle.

Terrestrial laser scanning for detection of landfill gas: a pilot study

Methane built up in landlls as a result of breaking down of organic materials can be a renewable energy source if it is taken advantage of. The aim of research presented in this paper is to detect landll gas (that contains methane) by means of terrestrial laser scanning. The hypothesis is that where no surface leakage has been reported, the landll gas will expand or migrate. Therefore, it is possible to detect it through repeated scanning of the same area and comparison of Digital Terrain Models (DTMs) generated from the point clouds. Only the most signicant movements, i.e. vertical, are of interest in this case. During September–November 2011, a small area at Forsbacka landll in the vicinity of Gavle was scanned 10 times. Epoch-to-epoch comparisons of the resulting DTMs have shown two signicant changes (–27 and +19 mm) in elevation of the surface, and it is not impossible that they are caused by migrating landll gas. The method tested in this study is deemed to be rigorous and accurate for detecting small-scale swell-shrink behaviour of the ground surface (in our case a landll surface). However, both data processing and interpretation of the results have been considerably complicated by presence of low vegetation (weeds) on the study site, which was di-cult to lter away completely from the data. Based on our pilot study, we recommend that a larger area and a longer period of time are chosen to give basis for more grounded conclusions about presence of landll gas.

The relationship between shrink–swell occurrence and climate in south-east England

Climate change is one of the biggest environmental problems that the UK faces. Increased understanding of the impacts is vital to enable adaption to, and mitigation of, the consequences. This analysis and modelling of the relationship between climate and shrink–swell behaviour has been carried out to increase understanding of the potential consequences of changes in precipitation and temperature on ground movement in the south-east of England during the coming century.Analysis of historical climate data and comparison with subsidence claims data demonstrated the relatively close relationship of subsidence with two years’ previous precipitation. Boundaries are identified, with precipitation above 394mm for the previous two years, leading to a lower level subsidence claims, and below 350mm leading to a higher incidence. Combined with this inverse relationship, a direct relationship with temperature is identified, with a rise above 22.6°C in the mean maximum temperature for an accounting quarter leading to a peak in claims.To model a projection for susceptibility of south-east England to future climate change, UKCIP02 forecast climate data were used, and combined with the British Geological Survey national shrink–swell GeoSure geohazard dataset. Preliminary results demonstrate the most noticeable increases in subsidence susceptibility are within the areas underlain by the London Clay Formations, with other clay-rich formations also being identified, including glacial till.Despite this being a preliminary model, with large amounts of future work identified, these results are significant, providing an insight into areas of higher susceptibility and the potential for changes in ground movement for the coming century.

Treatment for Expansive Soil Channel Slope with Soilbags

AbstractExpansive soil is regarded as one of the trouble soils and is difficult to deal with in engineering because of its strong swelling–shrinkage behavior and well-developed fissures and overconsolidation. In this paper, a treatment method for an expansive soil channel slope with soilbags is proposed. The mechanism of the proposed treatment method is introduced. A number of the swell potential, swelling pressure, seepage, and interlayer friction tests were conducted on soilbags filled with expansive soils, which were taken from a construction site of the South-to-North Water Transfer Project in China. The test results indicate that soilbags can enhance the strength and restrict the swelling deformation of the expansive soil, and that the assembly of soilbags has a high permeability and interlayer friction coefficient. The stability of an expansive channel slope reinforced by soilbags is analyzed based on the limit-equilibrium theory.

Morphological and Physico-Chemical Characteristics and Classification of Vertisol Developed on Deltaic Plain

The name of Vertisol is derived from Latin “vertere” meaning to invert. This case restricts development of soil horizons in profile. These soils have the capacity to swell and shrink, inducing cracks in the upper parts of the soil and distinctive soil structure throughout the soil. The formation of these specific features are caused by a heavy texture, a dominance of swelling clay in the fine fraction and marked changes in moisture content. The swell-shrink behavior is attributed to the wetting and drying of the soil mass. In this study, morphology, physico-chemical characteristics and classification of vertisols that were formed on alluvial delta plains, were investigated. Those soils formed on the Bafra Plain found in the K?z?l?rmak Delta and located in the central Black Sea region of Turkey. All studied Vertisols are characterised by a dark colour in surface soil, a heavy clayey texture, hardpan formation under top soil (high bulk density a high compaction) and very high COLE values. In addition, they have deep wide-opened desiccation cracks at the surface, slickensides at the middle part of the profiles and a poor differentiation of their horizons. Physico-chemically, the studied soils are slightly basic to very basic, non-saline and poor in organic matter, which is slightly higher in the surface horizon. In addition, cation exchange capacity, sum of exchangeable bases and base saturation of soils are very high. On the basis of morphological and physicochemical analysis, soil profiles were classified as Sodic Haplustert, Typic Calciaquert, Sodic Calciustert according to Soil Taxonomy (Soil Survey Staff, 1975 and 1999) and as Sodic Vertisol and Calcic Vertisol according to FAO/ISRIC (2006) classification systems.

Swell Potential, Collapse Potential, Wetting and Drying Cycles, Cracks, Number of Segment

Many of the soils undergo volumetric changes due to the change in the water content. Swell-shrink and collapse behavior of those soils affects the stress state in soil and the interacted structures. Shrinkage in the soil produce cracks of different patterns, and affects the swelling potential in next wetting cycle. This study covers swelling and collapsing properties of four different soils from Mosul city. The changes in swelling and collapsing properties with respect to number of wetting and drying cycles have been investigated. Also, A shrinkage cracks have been studied with aid of digital image after each drying cycle. Number of segments and area of cracks calculated with aid of AutoCAD package. Results indicated that, the collapse potential is influenced by soil type (soil composition) and applied loads. As the applied loads increase the collapse potential increases. For sandy soil the collapse potential decreased with increasing wetting and drying cycles, and for the clayey soils, swell potential decreased while collapse potential increased with these cycles. It has been shown that the cracks increase with wetting-drying cycles. Larger values of percent crack area to the initial sample area has been observed in the soil that contain more clay content than other types of soils.

Study on Swelling-Shrinkage Behavior of Vertisols along Fujian Coast

The climatic zone is characterized by alternate wet and dry seasons along Fujian coast. The vertisols experience periodic swelling-shrinkage during alternate wet and dry seasons. 16 soil samples from different profiles (0~20cm depth, 20~40cm depth)were collected from different regions in the research area. The paper shows the swelling-shrinkage behavior along Fujian coast in terms of morphology, particle content and physical properties of vertisols, The structure of the soil profile varies with depth, while the profile horizonation is weak. Crack network is usually observed on the surface. In addition, this paper investigated the effect of wetting and drying on the expansive chatacteristics of the soil. The test results show that after each cycle, the height of the soil samples increased. This indicates that the swell-shrink behavior of vertisols is not completely reversible. The swelling-shrinkage characteristics of soils become greater with stickier texture. Compared to undisturbed soils, the swelling-shrinkage behavior of disturbed soils are greater.

Petrological, Physico-Chemical and Mechanical Characterization of the Topomorphic Vertisols from the Sudano-Sahelian Region of North Cameroon

In Cameroon, topomorphic vertisols are widespread in the Sudano-sahelian zone above latitude 9oN. With a depth of about 2 to 2.5 m above the water table, these soils show four main horizons from bottom to top: a dark grey horizon with hydromorphic patches (B3g), dark grey horizon (B21), dark grey horizon with slickensides (B1) and a surficial grey humiferous horizon (A1) with desiccation cracks. Also, they show a heavy clayey texture, very massive structure, high bulk density, very low porosity and a high compacity. The microfabric of the soils is marked by abundant plasmas, isotic at the surface but birefringent at depth, with numerous stress cutans. The microscopic analysis of heavy minerals reveals the presence of magmatic and metamorphic minerals from the upper part of the watershed. Quartz grains are mainly angular to sub-angular revealing short fluvial transport distance. The vertisols are thus formed from recent alluvial deposits from weathering, erosion and deposition of rocks from upper parts of the watershed. Physico-chemically, the studied soils are characterized by high cation exchange capacity (26-42 meq/100g), high sum of bases (74.30-94.23 meq/100g), high base saturation, low organic carbon and a very high C/N ratio. Geochemically, Si and Al are the dominant elements, characterised by a Si/Al ratio range of 2.27 and 2.94. According to this rate, 2/1 clay minerals, namely smectite, are predominant and their presence confirms the shrink-swell behaviour of the soils. Total base concentrations are high and could be related to the contrasted climate and the low landscape position. Mechanical analyses revealed very high liquid limits (36-46%), low plastic limits (10-17%), high plasticity indices and high shrinkage limits that permit to classify those soils as medium to high plasticity inorganic clays. Those soils could be potentially useful in many domains like the chemical industry, pharmaceutics, petroleum industry, agronomy or environmental protection.

Modelling Volume Change Potential in the London Clay

Abstract The London Clay Formation is particularly susceptible to shrink–swell behaviour that has resulted in a long history of foundation damage owing to ground movement across the outcrop. Damage has cost up to £500 million in a single year. Underlying most of the Greater London area, the London Clay Formation is of major engineering importance as it is on and within this formation that the majority of the city9s infrastructure, buildings and underground services are constructed. The Volume Change Potential (VCP) of a soil is the relative change in volume to be expected with changes in soil moisture content, and the subsequent shrinkage or swelling can cause major damage to structures above or below ground. Detailed statistical and spatial analyses of data across the London Clay outcrop have revealed a significant geographical trend in the VCP of this deposit, confirming an overall increase from west to east, but also showing subtle trends with depth. This paper describes how this analysis was carried out and shows how such assessments can yield valuable information about shrink–swell behaviour not only of the London Clay but also of similar shrink–swell-prone argillaceous formations elsewhere.

Shrinking Behaviour of Badland Soil Under Different Soil Covers

Indicators used to estimate the soil structure stability facing erosion are the basis of major indicators of soil quality, and their behaviour is affected by permanent soil properties, vegetation and management. The relation between the pore-volume fraction occupied by water and the pore size distribution in clay soils is studied by the shrinkage curve describing clay soil porosity dynamics as a function of soil moisture. The aim of this work is to study the shrinking behaviour of the surface soil in a badland site through the shrinkage curve and to assess its relations with vegetation. Six treatments with different soil vegetation cover and aspect were selected on a badland site in Pisticci (Southern Italy). Shrinkage curves were built from natural aggregates collected in the 0-10 cm soil depth. Soil stability under shaking in water was also determined, with pre-treatments in water, alcohol and benzene for the determination of the SSI (Soil Stability Index). Soil organic matter, electrical conductivity, ESP were determined in order to investigate the relations between soil cover, chemical properties, SSI and shrink-swell behaviour. Vegetation was associated with lower soil salinity and ESP, and higher soil organic matter content. Vegetated sites showed a higher SSI and a lower overall swelling. The shrinkage curves for samples from vegetated areas lack of the structural phase of shrinkage, likely due to the combined effect of lower ESP and the mechanical effect of plant roots. All soil properties and indicators point to a higher stability of soils under grass in the south aspect and under shrub in the north one.

Analysis of the behaviour of a natural expansive soil under cyclic drying and wetting

Analysis of the behaviour of a natural expansive soil under cyclic drying and wetting

Cyclic Swell–Shrink Behaviour of a Compacted Expansive Soil

Laboratory cyclic swell–shrink tests were carried out on compacted expansive soil specimens to study in detail the effect of changes in shrinkage pattern on the swell–shrink behaviour of compacted expansive soils. Compacted soil specimens were allowed to swell and either shrank fully or partially shrank to several predetermined heights in each cycle. The tests were carried out at a surcharge pressure of 50 kPa. The test results revealed that shrinkage of compacted saturated soil specimens to predetermined height in each shrinkage cycle provides similar conditions as that of the controlled suction tests with an increasing number of swell–shrink cycles. The water content of soil specimens and hence soil suction was found to remain nearly constant for each pattern of shrinkage. For soil specimens equilibrated to a given swell–shrink pattern, suction at the end of shrinkage cycles was changed from a higher suction to a lower suction, and also from a lower to a higher suction. The experimental results showed that there may be an immediate equilibrium state attained by the soil in terms of swell–shrink potential if suction at the shrinkage cycles was less than the past suction; otherwise, the equilibrium state was accompanied by fatigue of swelling. The volumetric deformation of the soil specimen subjected greater shrinkage was found to be much larger than the corresponding vertical deformation. The compressibility index of microstructure, κm, was determined for several shrinkage patterns. It is shown that κm is heavily influenced by suction at the end of shrinkage cycles.

A model for determining the cyclic swell–shrink behavior of argillaceous rock

The swelling potential of rocks including clay minerals in arid and semi-arid regions, where the rocks experience completely dry to fully saturated conditions, is a complex problem. A method is lacking for determining the swell–shrink behavior of such rocks under variable water contents and boundary conditions prevailing in underground excavations. This paper suggests a method, which finally leads to a model, for determining the swell–shrink behavior of mudrock at the Masjed–Soleiman underground hydroelectric power plant (UHEPP). The recorded nonlinear behavior of the mudrock is modeled using an artificial neural network (ANN). The ANN model utilizes the information from the previous swell–shrink cycles to learn and model the dynamics of swell–shrink behavior. Using this method facilitates prediction of swelling pressure of argillaceous rocks with different swelling potentials and site conditions.

Porosity and available water of temporarily waterlogged soils in a Quercus robur (L.) declining stand

Pedunculate oak (Quercus robur L.) is particularly sensitive to decline in clayey soils presenting a high-perched temporary water table. These soils induce two successive constraints in one-year cycle: water excess (and hypoxy) in winter and early spring, and water shortage in summer (water stress being more restrictive to oak). We determined the porosity and water properties of temporarily waterlogged clayey soils supporting forest stands of declining Quercus robur trees in a 101 yr-old oak stand in Belgium (50 degrees 06'N 4 degrees 16'E). Roots unevenly colonized the soil down to 1.6 in: fine roots (diameter < 5 mm) were mostly distributed on the surface horizons (0-0.3 in) and around 1.3 in deep, despite dense clayey horizons appearing at 0.35 in depth. Clay content below this depth reached 46-51%. Illite and vermiculite were the dominant clay minerals. The clayey horizons exhibited marked shrink-swell properties: bulk density at 30 kPa increased from 1.41 to 1.88 g cm(-3) from the surface to 2 m depth. There was also evidence of hypoxic conditions caused by water saturation of pore space in the rooting zone from October to mid-April. Extractable water (EW), calculated between moisture tensions of 5 and 1600 kPa was 152.8 mm. The level of perched temporary water table strongly depended on the seasonal rhythm of water uptake by trees and on the shrink-swell behaviour of soil.

Influence of interlayer cations on the water sorption and swelling–shrinkage of MX80 bentonite

The potential of water sorption and swelling–shrinkage in the expansive clays is practically defined by the nature of interlayer cations. The purpose of this paper is to estimate the effects of the cation saturation (Mg +, Ca +, Li +, Na +, and K +) on the swelling–shrinkage behaviour of the MX80 bentonite. The MX80 bentonite (a “commercial clay”) was treated with concentrated solutions (1 N) of sodium, calcium, magnesium, potassium, and lithium chlorides. This treatment was made three times with constant agitation for 1 h. Then, the clay was washed three times with distilled water. The scanning transmission electron microscopy (STEM) and inductively coupled plasma atomic emission microscopy (ICP-AES) analyses were used to verify the efficiency of the cation saturation. Finally, two techniques were employed to estimate the effect of the cation saturation on the swelling–shrinkage behaviour of the bentonite: the first one uses an isothermal system of water adsorption, where the water activity is controlled by a supersaturated salt solution. In the second, environmental scanning electron microscopy (ESEM), coupled with a digital image analysis (DIA) program, was used to estimate the swelling–shrinkage potential at different water activities. The swelling–shrinkage isotherms were always estimated on isolated aggregates. The isotherms of water adsorption and swelling–shrinkage of the bentonite MX80 show that the amount of adsorbed water and the swelling–shrinkage potential depend directly on the interlayer cation. For example, the sodium bentonite presents an excellent capacity to swell while the lithium bentonite does not swell significantly at the aggregate scale. In addition, other textural properties may be modified by the cation saturation, such as the specific surface, the particle size, porosity, etc.

Effect of Aging on Swelling and Swell-Shrink Behavior of a Compacted Expansive Soil

Abstract Effect of aging on swelling and swell-shrink behavior of a compacted expansive soil is investigated in this paper. An expansive soil having a liquid limit of 100% is used for this purpose. Compacted specimens were prepared and aged for a predetermined number of days (7, 15, 30, and 90 days) to study their swelling and swell-shrink behavior. It has been shown that aging improves the resistance to compression of compacted specimens. The swelling potentials of specimens also decreased with aging. The dominant factors that influence the aging effects are the water content and degree of saturation at the beginning of the aging process. The changed behavior of aged specimens is attributed to particle rear-rangements and formation of bonds, which affect the surface area absorbing water during swelling. The cyclic swell-shrink tests on aged specimens indicated that the differences in vertical displacement during the first swelling were eliminated in the subsequent cycles when specimens were shrunk more, but the aging effect was found to persist with cycles for specimens subjected to lower shrinkage magnitudes.

Water content - void ratio swell-shrink paths of compacted expansive soils

This paper addresses the behaviour of compacted expansive soils under swell–shrink cycles. Laboratory cyclic swell–shrink tests were conducted on compacted specimens of two expansive soils at surcharge pressures of 6.25, 50.00, and 100.00 kPa. The void ratio and water content of the specimens at several intermediate stages during swelling until the end of swelling and during shrinkage until the end of shrinkage were determined to trace the water content versus void ratio paths with an increasing number of swell–shrink cycles. The test results showed that the swell–shrink path was reversible once the soil reached an equilibrium stage where the vertical deformations during swelling and shrinkage were the same. This usually occurred after about four swell–shrink cycles. The swelling and shrinkage path of each specimen subjected to full swelling – full shrinkage cycles showed an S-shaped curve (two curvilinear portions and a linear portion). However, the swelling and shrinkage path occurred as a part of the S-shaped curve, when the specimen was subjected to full swelling – partial shrinkage cycles. More than 80% of the total volumetric change and more than 50% of the total vertical deformation occurred in the central linear portion of the S-shaped curve. The volumetric change was essentially parallel to the saturation line within a degree of saturation range of 50–80% for the equilibrium cycle. The primary value of the swell–shrink path is to provide information regarding the void ratio change that would occur for a given change in water content for any possible swell–shrink pattern. It is suggested that these swell–shrink paths can be established with a limited number of tests in the laboratory.Key words: expansive soils, oedometer tests, swell–shrink behaviour, shrinkage tests.

Effect of cyclic wetting and drying on the index properties of a lime-stabilised expansive soil

Lime stabilisation of expansive soils in arid and semi-arid regions exposes them to cycles of wetting and drying due to seasonal climatic changes. Cyclic wetting and drying is known to alter the microstructure and swell–shrink behaviour of expansive soils. This paper uses the Atterberg limit tests to examine changes in the microstructure of limetreated expansive soils due to cyclic wetting and drying. Experimental results showed that lime-treated black cotton soil specimens experienced an increase in clay content and liquid limit and a reduction in plastic limit and shrinkage limit upon cyclic wetting and drying. These changes apparently occur due to a partial to near complete breakdown of particle aggregation/flocculation and cementation and an increase in diffuse ion layer thickness on cyclic wetting and drying of the lime-stabilised expansive soil specimens. La stabilisation à la chaux des sols expansifs dans les régions arides et semi arides les expose à des cycles d'humidification et de séchage dus aux changements climatiques saisonniers. On sait que les alternances d'humidification et de séchage changent la microstructure et le comportement dilatationcontraction des sols expansifs. Cet exposé utilise les essais de limite de Atterberg pour examiner les changements qui affectent la microstructure des sols expansifs traités à la chaux en raison des cycles humidification/séchage. Les résultats des expériences montrent que dans les échantillons de sol de coton noir traité à la chaux, il se produit une augmentation du contenu en argile et de la limite liquide ainsi qu'une baisse de la limite plastique et de la limite de contraction lors des cycles humidification/séchage. Ces changements se produisent apparemment en raison d'une défaillance partielle ou presque compleète de l'agrégation/floculation et cimentation des particules et aussi en raison d'une augmentation de l'épaisseur de la couche d'ions diffus lors des cycles humidification/séchage des échantillons de sol expansif stabilisé à la chaux.