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The lateral swelling pressure (LSP) and vertical swelling of a highly expansive soil supported by a retaining wall was studied. Experimental work was conducted by designing a physical laboratory model with dimensions of 900 × 600 mm in plan and 950 mm in height. The finite element method was used to simulate the retaining wall supporting highly expansive soil in saturated and unsaturated conditions using GeoStudio 2007. Verification of the physical model showed that the LSP increased linearly with the depth of the wall up to the maximum value of about 165 kPa at a depth of 0.6 m. Predictions during saturation and loading stages showed that the quantitative predictions were within the measurement accuracy. Numerical predictions of the LSP and vertical swelling were compatible with the experimental results. The vertical swelling and percentage decrease in swelling decreased with the depth of the soil. The percentage decrease in vertical swelling was 95.0% at 34 days and a depth of 0.6 m. The rate of swelling decreased with an increase in soil depth and the time required to reach an equilibrium state of swelling decreased linearly with soil depth.

Purpose The estimation of bearing capacity for shallow foundations in swelling soil is an important and complex context. The complexity is due to the unsaturated swelling soil related to the drying and humidification environment. Hence, a serious study is needed to evaluate the effect of swelling potential soil on the foundation bearing capacity. The purpose of this paper is to analyze the bearing capacity of a rough square foundation founded on a homogeneous swelling soil mass, subjected to vertical loads. Design/methodology/approach A proposed numerical model based on the simulation of the swelling pressure in the initial state, followed by an elastoplastic behavior model may be used to calculate the foundation bearing capacity. The analyses were carried out using the finite-difference software (FLAC 3 D) with an elastic perfectly plastic Mohr–Coulomb constitutive model. Moreover, the numerical results obtained are compared with the analytical solutions proposed in the literature. Findings The numerical results were in good agreement with the analytical solutions proposed in the literature. Also, reasonable capacity and performance of the proposed numerical model. Originality/value The proposed numerical model is capable to predict the bearing capacity of the homogeneous swelling soil mass loaded by a shallow foundation. Also, it will be of great use for geotechnical engineers and researchers in the field.

Expansive soils like clays undergo swelling that can both be detrimental and acceptable in different applications. In the Northern part of India, especially Delhi region, natural soils containing clays & clayey sands support most of the buildings. Mechanically stabilized clays mixed with sand are used for local earthwork construction such as roads and landfills. Exact understanding of the swelling behaviour of such soils is a pre-requisite before the start of any construction projects. In this paper the swelling behaviour of clayey soil reinforced with geocell & Jute fibres has been presented. The laboratory investigations include one dimensional swelling tests using California Bearing Ratio (CBR) mould to study the swelling properties for different mix proportions. The maximum decrease in swelling potential of Geocell reinforced specimens was observed at fibre content of 0.80 percent and 40mm fibre length, beyond which increase in the swelling potential and swelling pressure has been observed. With this optimal reinforcement, a reduction of 71.24 percent in swelling and 41.10 percent in swelling pressure has been observed as compared to unreinforced soils. The study provides a solution towards the treatment of expansive soils before starting any construction activity over such soils and a step towards mitigating disasters related to infrastructure facilities grounded on expansive soils. Doi: 10.28991/cej-2021-03091728 Full Text: PDF

Slope failures and slope slides of expansive soils are usually characterized by shallow sliding along the surface crack. Soilbag is an effective method to prevent and control slope failures and slope slides of expansive soil. Currently, soilbag protection for expansive soil slopes has been commonly designed using empirical methods, which led to many failures of soilbag-protected slopes, or high-cost. In this paper, a new design method of the soilbag-protected slopes in expansive soils is proposed based on the balance between the soilbag friction and the active lateral earth pressure induced by the swelling pressure of expansive soils. Specifically, the friction between the soilbags is assumed to be in direct proportion to the soilbag heap-up height. The active lateral earth pressure acted on a layer of soilbag is calculated along with the total height of the slope. Moreover, the width of soilbag layers is calculated from the balance of the sum of soilbag friction and the total active lateral earth pressure along with the soilbag height and expressed by the height of slopes. For the convenience of soilbag construction, the heap-up unit of soilbags is proposed for different slope heights of expansive soils.

Faults/weakness zones with gouge containing swelling clay (smectite) have in several cases caused serious stability problems in tunnels. The first part of this paper describes briefly some recent cases of instability/cave-in where swelling clay has been a main cause of the incident, followed by brief reviews of structure and properties of smectite and relevant laboratory test procedures. Main focus is placed on swelling pressure, which is a key parameter for understanding the potential problems that may develop when crossing a major fault/weakness zone, and a key factor also for analysis of stability and rock support requirement. Laboratory test results presented in this paper illustrate that swelling pressure may vary considerably between different locations of the same zone, and that test results based on standard laboratory preparation do not correspond well with results based on testing of in situ undisturbed samples. Swelling pressure based on laboratory testing, therefore, should not be used directly in stability analysis and rock support design. Recommendations on proper use of laboratory test data are given at the end of the paper.

The effect of technological voids on the swelling pressure of compacted MX80 bentonite–Callovo-Oxfordian (COx) claystone mixture was investigated by simulating the technological voids with a pre-defined space between the compacted disks of the mixture. Both axial and radial swelling pressures were monitored. After the tests, the microstructure of samples at different positions was investigated using mercury intrusion porosimetry (MIP), together with the determination of dry density and water content. Results showed that two main processes, filling and homogenization, occurred during soil hydration. In the filling process, the initial technological voids were gradually filled and the axial swelling pressure tended to increase. In the homogenization process, the samples had a sealing zone and a swelling zone. The sealing zone was characterized by a lower dry density than the expected final dry density while the swelling zone was characterized by a larger one. From the MIP results, the sealing zone showed larger inaccessible-pore, medium-pore, and large-pore void ratios and a lower small-pore void ratio than the swelling zone. Over time, the medium and large pores in the sealing zone were compressed, while the small pores in the swelling zone decreased. The stabilized axial swelling pressure followed a unique relationship with the expected final dry density. Moreover, the swelling pressure anisotropy was found to decrease as the technological voids increased.

Structures constructed on expansive soils are experiencing higher upward pressure due to swelling- shrinkage nature of expansive soil. India has 15–20% expansive soil, which causes severe damage to the existing structure, including pavements, dams, multi-storey buildings, retaining walls. The aim of the study is to suitably reduce the distressed caused by the expansive soil on paved structures. The experimental result of expansive soil subgrade reinforced with and without coir geotextile mat has been presented in this paper. Lime and silica fume, treated and untreated coir geotextile mat with polypropylene fiber net has been used. A single and double layer of coir geotextile mat at various depths have been placed to evaluate the effect of reinforcement on expansive soil subgrade. The treatment was carried out to enhance the efficiency of coir geotextile for reducing the swelling pressure of the expansive soil subgrade. The chemical and microstructural components of expansive soil samples were investigated by using X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR). The constant volume swelling pressure, California Bearing Ratio (CBR) and large size direct shear (300 mm × 300 mm × 150 mm) tests have been carried out to evaluate the effect of treated and untreated coir geotextile on expansive soil subgrade. The experimental results analyzed indicates that the lime treated coir geotextile mat reduces the upward swelling pressure by 52.19% in single-layer and 81.89% in double-layer. The tangible improvement in the shear strength and bearing capacity of expansive soil subgrade was observed with the inclusion of lime treat coir geotextile. A lime treated coir geotextile in a single or double-layer can be used to stabilize the expansive soil subgrade. The improved property of reinforced expansive soil subgrade can reduce the thickness of the subbase and base course layer in paved structure.

This paper presents the effects of fine sand and fly ash on the swelling of an expansive clay. Fine sand and fly ash were used as additives at varying quantities. Free swell index (FSI), swell potential and swelling pressure were determined for the additive contents of 0%, 5%, 10%, 15%, 20% and 25%. FSI decreased by 29% and 50.32% respectively when fine sand content and fly ash content increased from 0 to 25%. Swell potential decreased by 80.4% and 32.7% respectively when fine sand content and fly ash content increased from 0 to 25%. While swelling pressure decreased by 84.6% when fine sand content increased from 0 to 25%, it did not show any trend with fly ash content.

A testing procedure was proposed to study water movement in compacted bentonite and the development of swelling pressure (ps) when compacted bentonite specimens were wetted. In this procedure, a multi-ring mold was introduced for ps measurements, after which the specimen was sliced for X-ray diffraction to find movement of water in the interlayer space of montmorillonite. Results revealed a relation between four phases of ps development and evolution of four states of interlayer water molecule arrangement of montmorillonite (L): when ps reached its first peak in phase I, L moved from 1 row water arrangement (1w) to at least 2w; when ps decreased and re-increased in phases II or III, L moved from 2w to at least 3w; and when ps reached a steady state in phase IV, L = 3w. The w distribution in the compacted bentonite was also measured as water absorption time increased. Based on those results, the global water movement was estimated in terms of diffusivity (D) following a method employing Boltzmann transform. Results of comparisons implied that D calculated using this method matched experimental data well and the method was rather easily handled.

The effect of waste engine oil (WEO) contamination on the geotechnical properties of cohesive soils was investigated. Three cohesive soils were collected from three locations in Sulaimani City. Geotechnical laboratory tests were carried out included consistency properties, unconfined compression strength, swelling pressure, and compressibility properties for both of intact and contaminated soil samples. Various percentages (0%, 1%, 2%, 4% and 6%) of WEO were mixed with the selected cohesive soil as a simulation of the field contamination issue. The results showed that the liquid limit (LL), plastic limit (PL), plasticity index (PI) increased as the content of WEO increased, however, experienced a decrease at 1% WEO content, thereafter an increase commenced again. The values of linear shrinkage limit, unconfined compressive strength (UCS), swelling pressure (SP) and Recompression index (Cr) decreased as the content of the WEO increased. The values of compression index (Cc) also increased at 0%, 1% and 2% WEO content, after that a little increase commenced again. WEO contaminated soil requires stabilization before using it as a construction material and/or for construction projects foundations.

Compacted bentonite as an artificial barrier/backfill material is susceptible to heat when combined with the hyperalkaline conditions of deep geological repositories. In order to investigate the st...

Unsaturated expansive soils annually cause major economic losses and structural damages to foundations and earthen structures, primarily due to exhibiting large amounts of swelling and shri...

Structures constructed on expansive soils experience higher upward pressure due to their swelling characteristics. Various conventional treatment methods developed to counteract swell–shrin...

Expansive soils have been well recognised as problematic that can pose threats to the stability of the Earth's structures due to the soils’ significant volumetric change when subject to moisture variation. In this study, a modified oedometer set-up was used to investigate the one-dimensional swelling pressure of compacted soils when subject to wetting under the constant volume constraint. Four expansive residual soils found in Auckland, New Zealand were tested. Based on the findings of two soils, a prediction formula of the swelling pressure was proposed. The formula considers not only the initial condition of the soil but also implicitly the amount of swelling minerals through the material's free swell index. The formula was validated using swelling data obtained from the other two expansive soils tested in this study and from data reported in the literature. The predicted swelling pressure was found to be reasonably close to the measured pressure, considering the range of soil expansivity in this study.

Swelling pressure of expansive soils can impose significant threat to the infrastructure built on them. Placing of compressible inclusion material, such as expanded polystyrene (EPS) geofoam, in expansive soils can effectively reduce the swelling pressure acting on the structure. This paper describes the experimental design, results of the tests used to investigate the use of compressible EPS in the form of geofoam layer (GL), geofoam column (GC) inclusion to reduce the swell potential, and swelling pressure of expansive soils. The tests were carried out on large one-dimensional consolidation equipment which can accommodate the California bearing ratio mold. Two different EPS geofoam densities were tested on two types of soil with varying swell potential under swell–compression test. The results of the tests are compared for the soil samples with and without GL and GC inclusion. The test results demonstrate that the percentage reduction in swell and swelling pressure is increased with increasing the thickness and cross-sectional area of GL and GC inclusion in expansive soils. In addition, the optimal EPS density was determined with respect to the maximum reduction in swelling.

The aim of this research is to investigate experimentally the relationship between free swell, plasticity index of expansive soil found in greater Cairo City Suburbs, Egypt with swelling pressure of mentioned soil. Predicting Swelling Pressure of any soil is a time consuming and expensive test in comparison to determining plasticity index and free swell which are simple, fast and economic tests. In present research six samples of expansive soil were collected from different locations of study area. The method uses single variable and multiple variable regression analysis using Microsoft excel software.

The present paper aims to reduce and detect the environmental impact of radioelement concentrations and waste marble powder (WMP) in the surrounding environment and additionally, improve the characteristics of the expansive soil and investigate the effect of stabilizers on the swelling soil to use a foundation layer. Different geotechnical laboratory tests have been performed on representative clay samples to define the physical and mechanical characteristics. The results indicate that the swelling pressure and swelling potential are reduced from (805.7 to 576 kN/m2) and (15.78 to 7.11%), respectively. The plasticity index decreased from 35.9% (high plasticity) to 19.4% (low plasticity), and the free swell index becomes zero by adding waste marble powder. Geospatial techniques have also been used to produce the distributions layers of different geotechnical characteristics and radioelements’ concentrations. These layers were integrated to produce a geospatial model. This model showed a noticeable improvement in the properties of clayey soils after the use of waste marble powder, which ranged from low expansion to high expansion. The radioelement concentrations of all samples are below an acceptable limit, except that the concentration of 40K is greater than the acceptable limit. This study recommends a 40% replacement of WMP. This amount is suitable and economical for this kind of treatment because of its positive solutions to protect the environment from pollution and reduce the cost of construction.

Lateral swelling pressure (LSP) develops when expansive soil volume increment associated with water infiltration is restrained in a confined domain, for example, due to construction of civil infrastructure. In this paper, initially a flowchart is developed to highlight various key factors that influence the LSP mobilization according to lab and field studies collected from previous literature studies. Then extending unsaturated soil mechanics, a theoretical framework is proposed for illustrating the LSP mobilization in the field against retaining structures and pile foundations under different boundary conditions, respectively. An example problem for a basement wall and a pile foundation constructed in a typical expansive soil from Regina, Canada, is presented to illustrate the proposed theoretical framework. The framework and corresponding analysis presented in this paper can facilitate to provide rational designs of geotechnical infrastructures in expansive soils.

Constructing over expansive soils often severely damage the structure due to high swell-shrinkage behaviour and loss of strength owing to fluctuating water content. Due to the above reasons construction on or using expansive soils is considered to be unsafe. The technique of such soil, improvement by installation of granular piles (also known as stone columns) is popular to marshy lands, marine clays, loose sand, silty or clayey sand, and compressible soils. Granular piles improve swelling properties of expansive soil. In the present study six expansive soils were used. The one of them was the naturally available black cotton soil and others were derived from it by mixing bentonite in different proportions. Test beds of these soils were prepared at different initial moisture contents and the granular pile of sand was installed in these beds by the method of removal. Besides initial moisture content, properties of expansive soils, the spacing between the piles (expressed by s/d ratio; s = spacing between the piles and d = diameter of a pile) and the relative density of granular pile forming material were the variables of the study. Multiple linear regression analysis on the test data has been performed and equations for predicting swelling pressure of soil bed without pile and inclusion with granular pile have been developed.

International audience; There are several methods for the determination of soil swelling pressure. In this study, such common methods were assessed using intact Callovo-Oxfordian (COx) claystone samples extracted in the direction perpendicular to the bedding plane, in the French Underground Research Laboratory in Bure. Higher swelling pressure was found with the swell-consolidation method, the swelling pressures determined by other methods being comparable. The swelling line that defined the swelling limit was lower than the consolidation curve, confirming the limitation of the swell-consolidation method in determining soil swelling pressure. Moreover, the swelling pressure corresponding to the in situ void ratio was expected to be 12 MPa–14 MPa, while the value corresponding to the sample void ratio after sampling was estimated between 0.3 and 1.9 MPa, much lower than the expected one. This large difference might be attributed to the claystone rebound due to unloading and claystone damage due to sampling. It could be also due to the natural material variability in terms of mineralogy and dry density. Further studies are, thus, needed for clarifying this point.

Lateral swelling pressures of expansive soils impose significant threats to the stability and safety of retaining structures. Placing a layer of compressible material, such as cohesive non-swelling soil (CNS), expanded polystyrene (EPS) geofoam or cohesionless soil (such as sand), between the retaining structure and the expansive soil can effectively reduce the lateral swelling pressure acting on the retaining structure. The work presented in this paper compares the efficiency of CNS, EPS and sand inclusions in reducing the lateral swelling pressure of a natural expansive clay. A special consolidometer was used to measure the lateral swelling pressure of expansive soil samples with and without inclusions under constant-volume condition, upon saturation. An analytical approach was used to interpret the efficiency of CNS, EPS and sand inclusions in reducing the lateral swelling pressure. It is found that (i) the efficiency of EPS inclusions is much higher than that of CNS and sand inclusions and (ii) sand is more effective than CNS in reducing the lateral swelling pressure at the same degree of compaction. It is suggested that EPS is preferred, the efficiency of sand is limited, and highly compacted CNS is unfavorable in reducing lateral swelling pressures.

The swelling pressure induced by expansive soils is considered a valuable parameter for the design of structures resting on these soils. It must be estimated in order to prevent damage to these structures and to design safe shallow foundations. In the recent research studies, the swelling pressure of expansive soil was predicted using the soil water characteristics curve SWCC. The present work investigates the interplay of the SWCC with the swelling pressure of expansive soil. The ABAQUS software was implemented in order to perform a coupled analysis of the expansive soil behavior. Published properties of the Regina expansive soil was used in order to validate the present numerical model. The validated numerical model showed good agreement with the published data of the Regina clay. The effect of the SWCC shape on the swelling pressure was thoroughly studied. The present results show a significant effect of the SWCC shape on the swelling pressure of the expansive soils.

This paper proposes a hydro-mechanical model of GMZ bentonite, based on the considerable amount of experimental research that has been developed recently. The model uses a double porosity approach based on the framework provided by the Barcelona Expansive Model to describe the deformability of the bentonite. A state surface was used to define its microstructural behaviour, based on the high-suction range data from water retention curves. The intra-aggregate (microstructural) and inter-aggregate (macrostructural) water contents were differentiated. The proposal was satisfactorily applied to simulate several constant stress swelling tests and swelling pressure tests, improving the confidence in the model. The use of this model has allowed not only reproduction of the experimental data but also improvement of our knowledge of GMZ bentonite behaviour.

The efficiency of a commercially manufactured sulphonated oil (SO) agent in treating a highly expansive soil was investigated through an extensive experimental program. A total of six SO to water m...

To deal with the destructive effects of swelling soils, different methods have been proposed by researchers. Chemical stabilization of expansive soils is one of the effective methods that are low-cost and efficient economically and technically. Recently, with the improvements of nano science in nanomaterials production and application, using this type of materials has been considered in different sciences especially geotechnical engineering. In this research, the effect of adding different amounts of nanoclay on swelling behavior modification of two types of clayey soils with low plasticity and high plasticity has been studied. For this purpose, first, identification tests were implemented on two types of clayey soils and nanoclay. Then, swelling potential tests were conducted on samples of soils with different amounts of nanoclay including (0, 0.25, 0.5, 1 and 2 weight percent) considering curing ages of 3 and 10 days. The results showed that the effect of adding nanoclay to the high plastic soils swelling potential is more than adding it to that of low plastic soils. So, adding 0.25 to 0.5 weight percent of nanoclay reduces the swelling potential of high plastic soils about 67 percent, and that of low plastic solis about 3 percent. Furtheremore, the maximum reduction in swelling potential increases by adding up to 0.5 percent nanoclay; and decreases for adding amounts more than 0.5 percent.

To investigate the effect of the changes in the soil suction on volume changes, expansion index, swelling pressure, shear strength and the coefficient of permeability, small-scale experiments were conducted on pure bentonite and bentonite mixed with sand with proportions of 30, 40 and 50% at different initial water contents and dry unit weights that were chosen from the compaction curves. In addition, large-scale model of soil with dimensions (700 × 700 × 650) mm was used to prepare the soil samples at the same initial water content and dry unit weight to show the effect of water content changes in different relations (swelling with time, swelling pressure with time, shear strength and soil suction). The results showed that the swelling potential decreases with increase in sand content from 14 to 2.4% by adding 50% sand to pure bentonite. The swelling percent found from the large-scale model is higher than that obtained from the oedometer swelling test for the same soil. This result applies well o...

Lateral swelling pressure (LSP) of expansive soils included in the total lateral pressure (TLP) often results in instability and even sliding failure of retaining walls. In this study, a mo...

The swelling and shrinkage phenomenon in expansive soil is one of the major causes of infrastructure distress for decades. The soils with montmorillonite as primary mineral composition possess property of excessive volumetric variation during drying and wetting of soil. The volumetric changes depend on proportion of clay mineral available, their exchangeable ions, and internal microstructure. The construction of structures on expansive soils experiences tilting, total and differential settlements resulting in cracking of building and basement walls, upheaving of rigid and flexible pavements, cracking and failure of utility lines, and damage to doors and windows. In order to understand the behavior of expansive soil and to determine the extent of damage that may occur many studies have been conducted in the past. Further, to categorize the extent of damage and type of distress that can occur due to expansive soil and probable remedial measures that can be helpful to mitigate swelling pressure, large amount of literature is available. This paper reviews the state of the art research related to different types of distress caused due to expansive soil, severity of cracking damage, remedial measures, and points to be considered while selecting remedial measures for expansive soils.

The most recent advancements of the research activity that has been carried out at the Polytechnic University of Turin since the 1990s are presented, with a focus on the design approaches which can be adopted for the optimisation of the engineered clay barriers that are used as a part of the composite liners of solid waste landfills. A particular attention is devoted to the characterisation of the geosynthetic clay liners (GCLs) in terms of their microstructural features and semipermeable properties, which affect both the liquid and contaminant transport and the swelling–shrinking behaviour upon a variation in the chemical and mechanical boundary conditions. In the first part of the paper, novel analytical solutions are derived in order to account for the influence of the chemico-osmotic counter-flow on the leakage rate through a lining system that consists of a geomembrane (GM) overlying a GCL, as well as for the effect of a variation in the GCL swelling pressure on the hydraulic transmissivity of the GM–GCL interface. In the second part of the paper, a steady-state analysis approach is proposed with the aim to include all the aforementioned phenomena in the assessment of the impact of contaminant migration through the landfill bottom liners on the groundwater quality, taking into account the presence of a natural attenuation layer between the GCL and the underlying aquifer.

When a tunnel is assumed to receive swelling pressure from rocks, it is necessary to estimate the swelling pressure properly and to set the external force condition for the tunnel’s repair design. For the mountain tunnel under service in Fukushima prefecture, there was a deformation at the roadbed and the tunnel lining due to swelling rock. Therefore we developed a swelling-rock model based on onsite monitoring data and laboratory test data. The model was used to estimate the external forces for design. Several monitoring devices were installed in the site to obtain rock deformation data around the tunnel and evaluate the mechanism of swelling. In addition, swelling pressure tests using site materials were conducted to grasp the swelling characteristics of the rock. A numerical simulation model was made for the interaction between the swelling pressure of the rock and the tunnel structure using the rock deformation with the results of the tests The simulation model, which was made in consideration of past data, estimates the external forces, which are necessary for the reconstruction of tunnels in the future. This paper outlines the method of setting the swelling model by numerical analysis, the features of the model, and the results of applying it to a tunnel.

The present study investigates the geotechnical characteristics of cemented clay-crumb rubber mixture through a series of compaction, UCS, STS, CBR, one-dimensional consolidation and swelling pressure tests. Crumb rubber (0.8–2 mm size) and cement content in the mixtures were 0%, 2.5%, 5%, 7.5%, and 10%, and 0%, 3%, and 6% by the dry weight of the specimens, respectively. The results of experimental research indicated that incorporation of crumb rubber in cemented clayey soil decreases the UCS and STS but prosperously able to overcome the brittleness of cemented clay in compression and tension. The CBR values of the composite having 6% cement were found to be propitious for its use as road sub-base with light traffic. It was also noticed that crumb rubber helps in reducing the swelling pressure and compression index of the mixes, which make it is a good candidate for lightweight fill material behind the retaining walls and embankment construction. Incorporation of crumb rubber in uncemented and cement clayey soil potentially reduces the reinforcement cost and deteriorating impact of waste tire disposal on the environment.

This paper presents a methodology for determining the radial swelling pressure that develops in a cylindrical plastic cell when the bentonite sample it contains is hydrated. Strains in the cylindrical cell wall are measured using strain gauges fixed to its external surface. The plastic cell material is assumed to behave in an elastic manner at the level of strain developed, and a best-fit solution for the pressure that results in the measured strains is calculated using an algorithm of optimisation. Even though the solution obtained is unique, it is also checked to verify that the calculated radial pressure results in the quantity of elastic energy developed in the cylindrical cell wall being a minimum. While the measurements obtained using the strain gauges allow the evolution of swelling pressure to be monitored from a qualitative viewpoint, the precise quantification of swelling pressure is difficult because not all the required pressure measurements were available. This paper demonstrates that the proposed methodology allows the qualitative monitoring of swelling pressures in bentonite cores during hydration. It also provides the basis for a quantitative procedure to be developed in the future.

In this article, the potential of a binder developed by admixing fly ash and ground granulated blast furnace slag (GGBS) to stabilise expansive soils is evaluated. Laboratory tests included determination of free swell index, swell potential and swelling pressure tests of the soil/binder mixtures at different mixing ratio. The test results showed decrease in the swelling behaviour of the soil with increase in binder content. The percent swell–time relationship was observed to fit the hyperbolic curves enabling us to predict the ultimate percent swell from few initial test results. Addition of 1% of lime to the binder showed further improvement in reducing swelling. A good linear relationship is established between percent oedometer swell and modified free swell index (MFSI) for soil/binder mixtures without lime but the same has not been observed in the presence of lime. The compressibility characteristics of the soil/binder mixtures reduced nominally with increase in binder content but in the prese...

The one-dimensional (1-D) potential heave (or swell strain) of expansive soil is conventionally estimated using the swelling pressure and swelling index values that are determined from different types of oedometer test results. The swelling pressure of expansive soils is typically measured at saturated condition from oedometer tests. The experimental procedures of oedometer tests are cumbersome as well as time-consuming for use in conventional geotechnical engineering practice and are not capable of estimating heave under different stages of unsaturated conditions. To alleviate these limitations, semi-empirical models are proposed to predict the variation of swelling pressure of both compacted and natural expansive soils with respect to soil suction using the soil-water retention curve (SWRC) as a tool. An empirical relationship is also suggested for estimating the swelling index from plasticity index values, alleviating the need for conducting oedometer tests. The predicted swelling pressure and estimated swelling index are then used to estimate the variation of 1-D heave with respect to suction for expansive soils by modifying Fredlund’s 1983 equation. The proposed approach is validated for eight field sites from six countries — namely, Saudi Arabia, Australia, Canada, China, USA, and UK — and on six different compacted expansive soils from USA.

Highly-compacted bentonite (HCB)-based sealing systems are being developed for potential use in nuclear fuel waste repositories because of their inherent physicochemical and rheological properties. Results from previous short-duration (40–90 days) studies with highly-compacted (HC), water infused, confined Wyoming MX-80 bentonite revealed that a uniform dry density ≥ 1.6 g/cm3 (resulting in a swelling pressure above 2000 KPa, water activity below 0.96 and an average pore size of

Many sections of floodwalls in New Orleans, LA were damaged or suffered catastrophic failure as a result of Hurricane Katrina. One of the key triggering mechanisms of failure reported is the gap development between the floodwall and soil. This study developed an effective retrofitting technique to prevent this gap development by introducing a buried layer of self-sealing sand and bentonite mixture. This self-sealing layer was expected to swell fast enough so that it could seal the gap without any time delay and to exert insignificant swelling pressure to the levee so that it did not affect the stability of the levee. Among several mixtures of sand and bentonite, the mixture of 70% sand and 30% bentonite (by dry weight) proved to be a more effective one among laboratory and large scale model tests conducted in this study by swelling fast enough to seal the gap (approximately 10% swelling strain in 2 days), but exerting insignificant swelling pressure (162.03 kPa in 2 days) to the levee. From the numerical ...

Swelling deformations leading to convergence of tunnels may result in significant difficulties during the construction, in particular for long term use of tunnels. By extracting an experimental based explicit analytical solution for formulating swelling strains as a function of time and stress, swelling strains are predicted from the beginning of excavation and during the service life of tunnel. Results obtained from the analytical model show a proper agreement with experimental results. This closed-form solution has been implemented within a numerical program using the finite element method for predicting time-dependent swelling strain around tunnels. Evaluating effects of swelling parameters on time-dependent strains and tunnel shape on swelling behavior around the tunnel according to this analytical solution is considered. The ground-support interaction and consequent swelling effect on the induced forces in tunnel lining is considered too. Effect of delay in lining installation on swelling pressure which acting on the lining and its structural integrity, is also evaluated. A MATLAB code of “SRAP” is prepared and applied to calculate all swelling analysis around tunnels based on analytical solution.

The support systems of excavations (such as underground mining openings and water tunnels) experience the time dependent induced pressure of the ground in vicinity of swellable rock. This research examines the interaction of swellable rock under different initial pressure to simulate the behavior of such rocks behind the support systems. A device was designed and constructed to model the condition in laboratory. Marlstone samples from Marash project in North West of Iran were chosen to perform the tests. The swelling pressure under different initial support pressure (ISP) was measured over time. The lowest swelling pressure was recorded under the minimum initial pressure. The swelling pressure of samples do not expose under high ISP (about 5 times of the steady swelling pressure). The differential swelling pressure (swelling pressure minus the ISP) generally increases from a minimum, at the lowest initial pressure, to a maximum, at the initial pressure equal to the steady swelling pressure. After reaching this maximum value, the differential pressure reduces back to zero where the ISP hampers the swelling phenomenon.

Adequate rock support in weakness zones that may contain swelling minerals poses one of the main challenges of excavating tunnels in hard rock conditions. Deformations under such conditions are influenced by several factors, including the properties of the rock mass, rock stress and the possible swelling potential of the minerals. Thus, dimensioning rock support may be challenging. To increase the knowledge regarding the processes behind deformations in areas of swelling gouge material, an experimental triaxial laboratory test of such material was performed. The main objective was to investigate whether the material might exert pressure under typical in situ stress conditions, or whether other processes might be dominant. In addition, the possible elastic and strength properties of such material were investigated. The testing was performed on reconstituted cores with material from four different locations in eastern Norway. The material was dried and then pressed into cores using a compactor. The triaxial testing consisted of four successive phases: pre-stressing 1; water addition under constant strain; pre-stressing 2 and failure. The results indicate that factors other than swelling pressure are the main causes of tunnel deformation, as no build-up of swelling pressure was observed during the water addition phase. Initially, the E-modulus and strength properties of the samples were very low, which can cause large, immediate deformations in situ. In addition, creep and possibly a reduction in the Emodulus during water addition seemed to cause time-dependent deformation. © The Author(s) 2019. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Many pioneering foundation techniques have been suggested for plummeting the unfavorable heave of foundations placed in expansive clays. This paper presents another innovative technique of the determination of load creating a specified amount of settlement and load which maintains no uplift/no settlement. In the present study a slip layer of varying thickness is introduced along the pile periphery and depth of swelling zone, intensity of anisotropic swelling pressure are varied and stress based analysis is conducted and load creating a known amount of settlement and load which maintains no uplift/no settlement are found out. It is accomplished that (a) Increase in expansive zone increases, load required for known amounts of settlement increases for a given slip element thickness, bulb diameter and swelling pressure (b) The soil heave and pile uplift are immensely affected by the intensity of anisotropic swelling pressure intensity. (c) Provision of slip element below the pile tip reduces the pile upheaval.

In geotechnical engineering field, bentonite–sand mixtures have been proposed and used as engineered barriers for containing the waste. This paper presents the laboratory evaluation of compressibility by performing one-dimensional consolidation tests on six different mixtures of bentonite with sand. The bentonite–sand mixtures were formed by varying sand content in bentonite in increments of 5% from 5 to 25% by dry weight. Dry bentonite–sand mixtures were placed initially in the consolidation cell at their loosest dry state and then allowed to saturate. Swelling characteristics and swelling pressures of the bentonite–sand mixtures were also evaluated. This paper also presents the laboratory evaluation of permeability of the bentonite–sand mixtures by performing falling head test after every load increment during the consolidation test. This study arrived at the conclusion that amount of swelling (expressed in percentage) and swelling pressure decreased with addition of sand. Moreover, changes were observed for the consolidation parameters upon addition of sand to bentonite. The void ratio versus log of permeability plots was found to be linear, and permeability was found to increase with increase in sand content.