Swell Shrink Research Articles

Effect of Physico-Chemical Interactions and Cyclic Wet–Dry Process on Behaviour of Compacted Expansive Soils

Physico-chemical interactions and alternate wetting and drying process have marked influence on the swell–shrink and hydraulic behaviour of compacted expansive soils used in various engineering applications. The microstructural, shrinkage cracks pattern and hydraulic behaviour of compacted expansive soils get altered due to the interactions with leachates and cyclic wet–dry process. Therefore, the effect of concentration of leachates and cyclic wetting–drying process on the swell–shrink, shrinkage cracks, microstructural and hydraulic behaviour of compacted expansive soil is studied in this theme lecture paper. The shrinkage cracks developed in clay specimen during a drying cycle were quantified using the X-ray computed tomography images and vernier caliper height measurement. And the same method was used to quantify the cracks in desiccated specimens interacted with different concentrations of interacting fluid. Scanning electron microscope and mercury intrusion porosimeter studies were carried out to understand the microstructure of salt solution-interacted specimens. The influence of physico-chemical interactions and cyclic wet–dry process on the self-healing capacity of compacted expansive soil specimens was brought out by carrying out hydraulic conductivity tests.

Isolated Effect and Sensitivity of Agricultural and Industrial Waste Ca‐Based Stabilizer Materials (CSMs) in Evaluating Swell Shrink Nature of Palygorskite‐Rich Clays

This paper evaluates the suitability of sugarcane bagasse ash (SCBA) and waste marble dust (WMD) on the geotechnical properties of Palygorskite‐rich expansive clays located in northwest Pakistan. These problematic soils exhibit undesirable characteristics which greatly affect the pavements, boundary walls, slab‐on‐grade members, and other civil engineering infrastructures. A series of geotechnical tests were performed on soil specimens using prescribed percentages of the aforementioned Ca‐based stabilizer materials (CSMs). The investigation includes X‐Ray Diffraction (XRD) Analysis, Scanning Electron Microscopy (SEM), X‐Ray Fluorescence (XRF) tests, and physicomechanical properties such as moisture‐density relationship, Atterberg’s limits, swell pressure, and an ANN‐based sensitivity analyses of overall swell pressure development. The outcomes of these experimental investigations showed that the addition of CSMs into the expansive soils increased to 4% SCBA and 10% WMD, the plasticity index reduced by 30% and 49%, the volumetric swell decreased from approximately 49% to 86% and 63%, and the swelling pressure reduction was from 189 kPa to 120 kPa and 160 kPa (about 15% and 36%), respectively. It is interesting to note that replacement with specified CSM accelerated the strength of soil at extended curing periods and the optimum improvement in the strength behavior of the soil was also recorded. Moreover, with addition of the respective CSMs, the compactability and strength characteristics were ameliorated, while plasticity was significantly lowered. Given the amount of SCBA and WMD produced annually, their utilization for the stabilization of problematic soils, even in relatively low concentrations, could potentially have a substantial impact on the sustainable reuse of these waste materials.

Effect of Functional Group of the Inorganic Additives on Index and Microstructural Properties of Expansive Soil

Expansive soils exhibit volume-change behaviour on exposure to moisture changes due to the presence of the montmorillonite mineral. The swell–shrink behaviour of these soils could lead to instability of the structures found on them, specifically the light-weight structures and pavements. Chemical stabilisation of expansive soils has always proven to be more successful in mitigation of swelling, compared to other methods of removal, replacement, and structural alterations. The present study focuses on the behaviour of a representative expansive soil treated with a conventional inorganic additive (lime) and less explored additives like calcium chloride and magnesium hydroxide, with a view to understand the effect of functional group of the inorganic additives in curtailing the swelling behaviour of the soil. The phenomenon of stabilisation is compared in terms of index and engineering properties based on the quantity of additives and curing period adopted. The macrostructural properties are evaluated through the changes in the plasticity characteristics, stress–strain behaviour, swell and permeability properties. The microstructural aspects of the treated soils are determined in terms of specific surface area, pore size measurements and minerology. Microlevel and macrostructural parameters are correlated to understand the soil-additive interaction and to quantify the extent of stabilisation and permanence of the additive induced changes. The lime and Mg(OH)2-treated samples effectively alleviate plasticity characteristics of the soil. However, strength of the lime-amended soil gets significantly improved, contributing to nearly 180% increase in strength compared to 100% and 45% increase for CaCl2- and Mg(OH)2-amended soils. Further, the additives also completely nullify the swelling phenomenon. The microstructure properties, SSA and pore size of the treated soils are concomitant with the macrolevel properties, such as permeability, swell and strength characteristics of treated soils, which further confirm the particle orientation of the soil on additive amendment. These analyses give a clear understanding of the orientation of the soil fabric, which dominates the overall behaviour of the soil-additive composites.

Effect of Swell–Shrink Cycles on Volumetric Behavior of Compacted Expansive Clay Stabilized Using Lime

Abstract In practice, it is quite common for soils to be mixed and compacted at moisture contents lower than the optimum moisture content (OMC) or lime content less than the optimum lime content (O...

Determination of volumetric changes in cracked expansive clays

The main objective of this research was to determine volumetric changes in cracked expansive clays. The presence of soil discontinuities was captured by using appropriate soil property functions, namely: a bimodal water retention curve and a sigmoidal swell–shrink curve. Field measurements were used in empirical equations to predict volume changes, and the results were validated using published data (laboratory testing, numerical modeling, or site monitoring). The results indicated that the average swell potential and swell pressure of the expansive Regina clay are 18 ± 2% and 155 ± 15 kPa, respectively. Likewise, heave was found to be 20–30 mm at surface and gradually diminished at 1.75 m depth. The predicted results closely matched the ranges and trends as validated using published data of laboratory testing, numerical modeling, or site monitoring. It is concluded that for natural and compacted expansive soils, the bimodal water retention curve differentiates between flow through the cracks and through the soil matrix. Likewise, the proposed sigmoidal equation accurately describes the swell–shrink curve with most of the deformations between the shrinkage limit and the crack limit.

Physical Indicators and Mechanism of Vertisolization: A Case Study of the Cis-Caucasian Vertic Chernozem

Vertisolization —the development of vertic properties and vertic horizons—is a widespread process leading to adverse physical and technological properties of chernozems.. There is still no generally accepted theory of the genesis of this phenomenon, although it is a priori clear that the physicochemical mechanisms of the interaction between fine particles and soil water in swell–shrink cycles are the underlying factors. Patterns of the dynamics of the main categories of soil porosity in dependence on the soil water content have been studied at a quantitative level in the genetic horizons of a Cis-Caucasian vertic leached chernozem (Luvic Chernozem (Epiloamic, Katoclayic, Aric, Novic, Bathyvertic)) in comparison with a chernozem without vertic properties. The physical state of vertic soils is represented by structural diagrams of porosity as a function of the specific volumes of various pore categories depending on the volumetric water content. The diagrams are constructed using the experimental data on the textural porosity of aggregates obtained by saturating individual aggregates with a nonpolar liquid (toluene) and humidification with hot water vapor and a fundamental ionic electrostatic model of the disjoining pressure. Vertisolization is characterized by a significant reduction in the textural porosity and a predominance of specific volumes of the external pore space (cracks and interaggregate voids) in the overall structure of the porous dispersed system. The most likely cause of vertisolization is a sharp (twofold) decrease in the effective width of the electrical double layer in the dispersed system with an increase in the particle interaction through stable layers of liquid phase (compaction effect). In turn, this brings about adverse technological properties of the vertic chernozems and lumpy fragmentation upon drying with the formation of large cracks, which complicates their tillage and agricultural activities in general.

Effect of zinc on uptake of macronutrients by soybean (Glycine max. L.) in swell shrink soil

A pot culture experiment was conducted during kharif season of 2013 - 14 at Nagarjun Medicinal Plant Garden, Dr. P.D.K.V - Akola, to assess the effect of zinc on uptake of macronutrients on soybean in swell shrink soil. The experiment was laid out completely randomised design (CRD) with five treatments and two replications. The treatments comprised of varied level of soil application of zinc at 0.0, 1.5, 3.0, 4.5 and 6.0 kg ha-1 in different soil samples. The results of pot culture study revealed that application of zinc @ 4.5 kg ha-1 had significantly influenced and improve the dry matter yield and uptake of nitrogen, phosphorus and potassium by soybean.

Cyclic swell–shrink behaviour of an expansive soil treated with a sulfonated oil

The effects of a sulfonated oil (SO) stabiliser on the swell–shrink properties of an expansive soil were investigated through cyclic wetting–drying tests. The cyclic wetting–drying action led to the reconstruction of the soil microstructure by inducing clay particle aggregation. Accordingly, the greater the number of applied cycles, the lower the swell–shrink potential up to the fourth cycle, beyond which the swelling and shrinkage strains attained elastic equilibrium. At any given cycle, the tendency for swell–shrink reduction was in favour of the SO concentration up to 0·75%, beyond which the excess SO molecules self-associated in the form of aggregates, thereby acting as a ‘lubricant’ rather than a clay-stabilising agent. As a result of SO treatment, the accumulated axial strain progressively transitioned towards a desirable, ‘neutral’ state, with 0·75% SO exhibiting the highest resistance against cyclic wetting–drying. For any given SO concentration, the equalised void ratio–moisture content curves for wetting and drying followed the same S-shaped path, further corroborating that the swelling and shrinkage processes, on achieving elastic equilibrium, become reversible. The shrinkage and liquid limits indicated a progressive transition towards a desirable, aggregated fabric, with 0·75% SO identified as the optimum concentration.

Estimating coefficient of linear extensibility using Vis–NIR reflectance spectral data: Comparison of model validation approaches

AbstractThe coefficient of linear extensibility (COLE) is used to classify soils according to their swell–shrink potential, and its estimation is crucial for engineering and agronomic applications. The aims of the study were (a) to develop a visible–near‐infrared spectroscopy (Vis–NIRS, 400–2,500 nm) calibration model to estimate COLE, (b) to compare two model validation approaches (mixed data and country‐wise), and (c) to test if a variable selection method improves the estimation accuracy of the calibration models. For this purpose, partial least square regression (PLSR) was used on the spectra of 53 soil samples from Slovakia and 24 samples from the United States. First, a calibration model based on 70% of the entire dataset (including samples from both locations) was developed and validated with the remaining 30% (mixed data approach). Second, a calibration model based on the Slovakian samples was validated with the U.S. samples (country‐wise approach). Higher predictability for COLE with standardized root mean square error (SMRSE) of 0.099 was obtained for the mixed data approach than for the country‐wise validation with SRMSE of 0.279. Furthermore, using interval PLSR (iPLSR) as a variable selection method did not improve the estimation accuracy of the mixed data approach (SRMSE of 0.099), and rather resulted in a twofold increase in SRMSE (0.560) for the country‐wise validation approach. Overall, the good estimation of COLE from Vis–NIRS was attributed to the high correlation of COLE with clay content and spectrally active clay minerals.

Soil sodicity originating from marginal groundwater

AbstractSoil salinity and sodicity are among the oldest soil and groundwater pollution problems and are widespread across the globe. Where salinity affects crop water uptake and yield, sodicity may additionally cause poorly reversible soil structure degradation and a severely reduced hydraulic conductivity. We use the model HYDRUS‐1D to simulate sodicity development in soils with shallow, Na‐rich groundwater under a normal weather regime with distinct dry seasons. Attention is given to the impact of a sudden fresh water input on the formation of a sodic layer. The complex interplay between soil chemistry, soil physics, soil mechanics (as far as swell–shrink behavior is concerned), and fluctuating atmospheric conditions results in a remarkably regular relation between depth, location, and severity of a sodic layer that forms within the soil as a function of rainfall intensity. A threshold behavior is observed: sodic layer formation is absent at rainfall intensities below this threshold, whereas sodic layer thickness and hydraulic conductivity reduction increase rapidly with intensities exceeding this threshold. This is the case even for different soil types and groundwater depths. Field observations agree with our simulations: the properties of the layer with sodicity‐induced structure degradation are more strongly developed, as this layer is situated at a shallower depth. The implementation of hydraulic conductivity reduction as a function of exchangeable Na percentage and ionic strength in HYDRUS‐1D can be improved towards a smooth reduction function, changing soil physical parameters due to swelling and dispersion of clay and reconsideration of the reversibility of sodicity development.

Explicit Integration Algorithm of the Bounding Surface Model Based on Swell–Shrink Rules for Cyclic Behaviors of Clay

Integration algorithm is a key to ensure the better application of the dynamic constitutive model. As for the bounding surface model based on swell–shrink rules in this paper, an explicit integration algorithm based on sub-stepping and error control scheme has be described in detail. For being adaptable to the constitutive model, several modifications have been made. The modified explicit algorithm includes two procedures: the first procedure is the second-order forward modified Euler scheme with sub-stepping and error control; the second procedure is the stress correction. However, due to the shrink rule of the bounding surface, the second procedure is not needed at the unloading phase. Finally, several numerical simulations have been conducted for assessing the performance of the explicit algorithm, which demonstrates that the corresponding algorithm is stable and accurate, and can simulate the mechanical characteristics of the clay pretty well.

Engineering Reactive Clay Systems by Ground Rubber Replacement and Polyacrylamide Treatment.

This study investigates the combined performance of ground rubber (GR), the additive, and polyacrylamide (PAM), the binder, as a sustainable solution towards ameliorating the inferior geotechnical attributes of an expansive clay. The first phase of the experimental program examined the effects of PAM concentration on the soil’s mechanical properties—consistency, sediment volume attributes, compactability, unconfined compressive strength (UCS), reactivity and microstructure features. The second phase investigated the effects of GR content, with and without the optimum PAM concentration. An increase in PAM beyond 0.2 g/L, the identified optimum concentration, caused the excess PAM to act as a lubricant rather than a flocculant. This feature facilitated reduced overall resistance to sliding of soil particles relative to each other, thereby adversely influencing the improvement in stress–strain–strength response achieved for ≤0.2 g/L PAM. This transitional mechanism was further verified by the consistency limits and sediment volume properties, both of which exhibited only minor variations beyond 0.2 g/L PAM. The greater the GR content, the higher the mobilized UCS up to 10% GR, beyond which the dominant GR-to-GR interaction (i.e., rubber-clustering) adversely influenced the stress–strain–strength response. Reduction in the soil’s swell–shrink capacity, however, was consistently in favor of higher GR contents. Addition of PAM to the GR-blended samples amended the soil aggregate–GR connection interface, thereby achieving further improvements in the soil’s UCS and volume change behaviors. A maximum GR content of 20%, paired with 0.2 g/L PAM, managed to satisfy a major decrease in the swell–shrink capacity while improving the strength-related features, and thus was deemed as the optimum choice.

Durability of Commercial Waste Bagasse Ash And Ground Granulated Blast Furnace Slag Stabilized High Plastic Clay

In the current work, a problematic expansive high plastic clayey (CH) soil of Surat, Gujarat, India has been treated with commercial waste bagasse ash (BA) and ground granulated blast furnace slag (GGBS) for sustainable development. Swell shrink behavior, California bearing ratio, unconfined compressive strength for different curing period have been studied. As expansive soil is very sensitive to seasonal variation, cyclic drying and wetting study has been carried out on both treated and untreated samples. The optimum blend is observed to be in the proportion of 82.5%CH + 10%BA + 7.5%GGBS. The unconfined compressive test results indicate that strength of 28 days cured samples of optimum mix increases about three times and eight times when compared to untreated sample and uncured sample respectively. The soaked California bearing ratio (CBR) indicate the increase in strength with increasing curing periods from 7 to 28 days. Optimum mix shows the decrease in swelling pressure and an increase in shrinkage limit as compared to untreated soil. The experimental results show good improvement in swell-shrink behavior, unconfined compressive strength, and soaked California bearing ratio when combined with bagasse ash and slag. The findings of this study revealed that bagasse ash in combination with ground granulated blast furnace slag is suitable as a pozzolanic material in stabilization of high plastic clay to reach the target strength for structures with improved swell-shrink behavior.

Experimental Study on the Influence of Polypropylene Fiber on the Swelling Pressure Expansion Attributes of Silica Fume Stabilized Clayey Soil

Expansive soil shows dual swell–shrink which is not suitable for construction. Several mitigating techniques exist to counteract the problem promulgated by expansive clayey soils. This paper explored the potential mecho-chemical reinforcement of expansive clayey soil to mitigate the effect of upward swelling pressure and heave. The polypropylene fiber is randomly distributed in the soil for mechanical stabilization, and the industrial residual silica fume is used as a chemical stabilizer. The experimental analysis was made in three phases which involved tests on mechanically-reinforced expansive soil, using randomly distributed polypropylene fibers with different percentages (0.25%, 0.50%, and 1.00%), and which were 12 mm length. The second phase of experiments was carried out on chemical stabilized expansive soil with different percentages (2%, 4%, and 8%) of silica, and the next phase of the experiment focused on the combination of mecho-chemical stabilization of the expansive soil with different combinations of silica (i.e., 2%, 4%, and 8%) and polypropylene fibers (i.e., 0.25%, 0.50%, and 1.00%). Maximum dry density (MDD), optimum moisture content (OMC), liquid limit (LL), plastic limit (PL), plastic index (PI), grain size, and constant volume swelling pressure tests were performed on unreinforced and reinforced expansive soil, to investigate the effects of polypropylene fiber and silica fume on the engineering properties of expansive clayey soil. The experimental results illustrate that the inclusion of polypropylene fiber has a significant effect on the upward swelling pressure and expansion property of expansive soil. The reduction in the upward swelling pressure and expansion is a function of fiber content. These results also indicated that the use of silica fume caused a reduction in upward swelling potential, and its effect was considerably more than the influence of fiber.

Influence of wetting–drying cycles on swell–shrink behaviour of GPA-reinforced expansive clay beds

ABSTRACT Granular pile-anchor (GPA) technique is an innovative tension-resistant foundation technique which can effectively ward off the dual swell–shrink problem posed by expansive clays. The other tension-resistant foundation techniques are drilled piers, belled piers and under-reamed piles. Laboratory scale model studies and field scale experiments on GPAs revealed that swelling of expansive clay beds could be effectively controlled by GPA technique. This paper presents results obtained from laboratory scale model studies on GPA-reinforced expansive clay beds subjected to alternate cycles of wetting and drying. Swelling and shrinkage of the clay beds were monitored for three wetting–drying cycles (N) spanning a time period of 300 days. The clay beds were reinforced with varying number of GPAs (n = 0, 1, 2 and 3). Swelling (mm) and shrinkage (mm) of the clay beds in a given wetting–drying cycle decreased with increasing number of GPAs. Further, swelling (mm) and shrinkage (mm) significantly decreased with increasing number of wetting–drying cycles (N) also. For a given number of GPAs (n), swelling and shrinkage decreased with increase in depth from the top of the clay bed too.

Small-scale laboratory test on expansive soil stabilized by CCR-Fly ash columns

Volumetric changes in expansive soils due to seasonal moisture changes can seriously damage foundations. In the small-scale laboratory study reported in this paper, the effect of inserting columns made from calcium carbide residue (CCR) and fly ash (FA) to reduce the swelling potential of expansive soil was examined. An attempt was made to determine the mineralogical changes in the soil and to identify newly generated reaction products by X-ray diffraction (XRD). The strength gain of the stabilised soil was investigated using unconfined compressive strength tests. It was found that the heave of the soil with columns of CCR and FA installed by in situ mixing and compaction reduced by up to 88% and 57%, respectively. The compressive strength of samples increased up to two-fold, and around the same level, for both installation methods after 90 d of curing. This increase in strength was an outcome of soil modification and stabilisation. The XRD results indicated the change in soil mineralogy. Further studies are required to study the cyclic swell–shrink behaviour of the stabilised expansive soil.

Swell–Shrink Behavior of Rubberized Expansive Clays during Alternate Wetting and Drying

The present study examines rubber’s capacity of improving the swell–shrink potential of expansive clays. Two rubber types of fine and coarse categories with different geometrical features were considered. The test program consisted of standard Proctor compaction and cyclic wetting–drying tests. Scanning electron microscopy (SEM) analysis was also performed to identify the soil–rubber amending mechanisms, and to observe the evolution of fabric in response to alternate wetting and drying. Cyclic wetting–drying led to the reconstruction of the soil/soil–rubber microstructure by way of inducing aggregation and cementation of the soil grains. The greater the number of applied cycles, the lower the swell–shrink features, following a monotonically decreasing trend, with the rubberized blends holding a notable advantage over the virgin soil. The tendency for reduction, however, was in favor of a larger rubber size, and more importantly the rubber’s elongated form factor; thus, predicating a rubber size/shape-dependent amending mechanism. The soil–rubber amending mechanisms were discussed in three aspects—increase in non-expansive content, frictional resistance generated as a result of soil–rubber contact, and mechanical interlocking of rubber particles and soil grains. The swell–shrink patterns/paths indicated an expansive accumulated deformation for the virgin soil, whereas the rubberized blends manifested a relatively neutral deformational state, thereby corroborating the rubber’s capacity to counteract the heave and/or settlement incurred by alternate wetting and drying.

Stabilization of Expansive Soils Using Polypropylene Fiber

Current research main aim is to study the effect of adding polypropylene fiber (PPF) on the behavior of expansive soil to reduce the swelling as percentage (0.5, 1 and 2%) of the weight of dry soil. Expansive soil used in this research was prepared artificially by mixing Ca-based bentonite from geological survey and mining company with sandy soil brought from Karbala city as percentage 80% bentonite to 20% sand of dry weight. Multiple laboratory tests have been carried are (Unconfined Compression Test, One-Dimensional Consolidation Test, Swelling Test, Sieve Analysis and Cycle Swell Shrink Test). A conventional odometer cell was modified to allow the study of swell- shrink cycle test to be carried out under controlled temperatures and surcharge pressure. The results showed that the increase in percentage of (PPF) led to decrease the swelling and to increase the unconfined compression strength. The wetting and drying results of (PPF) showed that with continuous cycles the effect of (PPF) keeps on reducing the swelling and the 2% of (PPF) produces less ratio of swell - shrink, which has obtained higher than 57 % in the improvement factor of swell and shrink.

Influence of fibres on volume change attributes of expansive soil blended with lime

Expansive soils are considered to be highly problematic due to their dual swell–shrink behaviour. In recent years, polymeric fibres are used to control the volume change behaviour of expansive soils. In this study, different proportions of lime and fibres were used to study the swelling and shrinkage behaviour of expansive soils. The test results showed that swelling tended to decrease slightly with an increase in the fibre content, whereas shrinkage decreased significantly with the addition of fibres. The optimum fibre content was found to be 2%. Both swelling and shrinkage tended to decrease significantly with increasing the lime content. It was also found that the optimum lime content is different for controlling swelling and shrinkage. Therefore, expansive soil specimens blended with 2% fibre and with varying lime contents were tested. The addition of 2% fibre helped to reduce the content of lime required for controlling shrinkage. It was found that blending 2% fibres and 5% lime together in expansive soils is effective for controlling both swelling and shrinkage behaviour.

Swell–Shrink–Consolidation Behavior of Rubber–Reinforced Expansive Soils

Abstract This study examines the effects of two types of recycled tire rubber of fine and coarse categories on the swell–shrink–consolidation behavior of a highly expansive soil mixture. Each of the two rubber choices were incorporated into the soil at four different content levels (i.e., rubber to dry soil mass ratio) of 5, 10, 20, and 30 %. The experimental program consisted of consistency limits, compaction, swell–consolidation, swell–shrink, and unconfined compression tests. Improvement in the swell–shrink–consolidation capacity was in favor of higher rubber contents; however, when excessively included, it raised strength concerns. The swell–shrink–consolidation properties were also rubber size-dependent, meaning that the rubber of coarser sizes often outperformed finer rubber. In terms of strength, however, the two rubber types promoted similar results with marginal differences. The results of the unconfined compression tests were cross checked with the swell–shrink–consolidation properties to arrive at the optimum stabilization scenarios. A maximum rubber inclusion of 10 %, preferably the rubber of coarser category, proved to satisfy the stabilization objectives (i.e., decrease in the swell–shrink–consolidation capacity as well as maintain or improve the strength) and thus was deemed as the optimum choice. Where context changes and the strength and stiffness are not a primary concern, higher rubber inclusions of up to 20 % may also be considered acceptable.