Free Swell Tests Research Articles

Determination of mechanical and hydraulic properties of polyacrylamide-added bentonite-sand mixtures

Bentonite-sand mixtures are typically used in engineering applications such as cutoff walls for waste containment facilities or barriers in landfills and freshwater reservoirs. However, low or reduced mechanical and hydraulic performance of a bentonite-sand mixture might result in the failure of the engineering structure. In order to enhance the mechanical and hydraulic properties of a bentonite-sand mixture, an anionic and a cationic polyacrylamides with a content of 1, 2, 5, 10, and 15% respectively were added to the bentonite-sand mixtures. The polyacrylamides used in this study were water-soluble synthetic polymers with high molecular weights. They had enhanced flocculation capability when coming into contact with soil and water. Standard Proctor compaction, consolidated-drained direct shear, unconfined compression, falling-head permeability, and free swell tests were performed on the bentonite-sand mixtures that had different bentonite contents. Test results indicated that cohesion, unconfined compressive strength, maximum dry unit weight, and swell index increased while internal frictional angle, permeability, and optimum water content decreased as a result of the polyacrylamide addition. The rate of change was much higher when the polyacrylamide content was increased up to 2%. The performance of the anionic polyacrylamide was found to be slightly better than that of the cationic polyacrylamide in terms of both strength and permeability. In conclusion, 2% anionic polyacrylamide addition resulted in a sufficient increase in the shear and compressive strength, a slight increase in the swell index, and a sufficient decrease in the permeability of the bentonite-sand mixtures.

Shear Strength and Consolidation Characteristics of Lateritic Soils: A Case of Asela Town, Oromia Regional State, Ethiopia

The most important engineering properties that determine the bearing capacity of soils are shear strength or ability to resist sliding along internal surfaces within a soil mass and the consolidation characteristics. Thus, in this study the shear strength and consolidation characteristics of Asela lateritic soil is studied. The shear strength parameters (i.e. Cohesion (C) and internal friction angle (Ф)) and consolidation parameters are determined using UU triaxial and 1-D odometer tests, respectively, on disturbed soil samples remolded with different densities and water contents in order to simulate the field condition. The shear strength test was done on the cylindrical samples of 38mm in diameter and a height of twice the diameter and the consolidation test were done on the samples of 75mm diameter and thickness of 20mm. In addition, the index test (specific gravity, grain size distribution, Atterberg limits and free swell tests) also conducted on air and oven-dried samples to understand the behavior and classification of the soils. The moisture content of the studied soil ranges between 17.35 – 32.51%, plasticity Index ranges between 11.8-26.4%, clay fraction ranges between 25.5-61.2, free swell ranges between 20-50% and specific gravity ranges between 2.59-2.95. The shear strength parameter, C and ɸ range from 89.63 to 161.48 Kpa and 17º-24º, respectively. The consolidation parameters: coefficient of compression ranges 0.193 to 0.581; coefficient of consolidation ranges 0.11 to 1.06 cm²/sec, coefficient of volume compressibility ranges 0.021 to 0.34m²/MN.

Development of Microfibril Absorbent Substantial for Hygiene Products using Compostable Agro-Residuals

An absorbent core structure is revealed for acquiring and absorbing aqueous-based liquids in hygiene products. The core is made of fiber pulp for wicking and absorbing an aqueous-based liquid and retaining the liquid against moderate pressure. Non-wood based regenerated cellulose fibers are an attractive alternative for cotton and wood pulp. The bast fibres and grass fibers are converted to pulp for its applicability as high absorbency, biodegradability and dissolute compost ability need for healthcare products. Enhancing the moisture transport and storage of the liquid by the delignified fibrils made serves more when compared to other natural fibers. The fibers are delignified by kraft pulping process for its strength, bulk, porosity and other functional advantages. Absorbent core properties from two different fiber pulps were investigated pertained good result. Fiber dimension and morphology were evaluated through SEM analysis and free swell test.

Investigation on the performance of ‘Fino’ materials to stabilize expansive soil: A case study in Yeka Sub City, Addis Ababa, Ethiopia

Expansive soil swells when it is wet, and it will shrink when it dries. Due to this behavior of the soil, the strength and other properties of soil are inferior. To improve its properties, it is necessary to stabilize the soil with different stabilizers. Soil stabilization is a process to treat the soil to maintain, alter, or improve expansive soil performance. In this study, the potential of 'Fino' as stabilizing additive to expansive soil was investigated for the improving engineering properties of expansive soil to be used as subgrade material. The evaluation involved the determination of the Free Swell test, CBR test, Atterberg's limits, and the Proctor test of expansive soil in its natural state as well as when mixed with varying proportions of 'Fino.' The practices were performed on six proportions 5%, 10%, 15%, 20%, 25% and 30 % with expansive soil. The research result indicated a considerable reduction in Swelling, and the Maximum dry Density of soil was improved. Optimum moisture content decreased in increasing 'Fino.' At 30% of 'Fino,' the CBR values of expansive soil increased from 1.06% to 5.94%, Liquid Limit decreased from 95.2% to 29.4%, plasticity index decreased from 57.24% to 17.82% and the degree of expansion of the natural subgrade soil has reduced from very high to medium. Hence, it is concluded that the 'Fino' at 30% has shown significant improvement in the expansive soil's engineering properties meeting the ERA and AASHTO Standard specifications requirements for road subgrade material.

Effectiveness of adding organic waste on expansive soil using handheld penetrometer and free swell test

Soil is the most important component in construction field, because soil supports construction buildings. The problem is, almost 65% soil in Indonesia is expansive soil that has large swelling and shrinking potential. This problem made worse by the tropical climate. Expansive soils easily shrink in dry season and swell in rainy season. Not only those problems, waste is also major problem in Indonesia. In order to prevent these two problems, a research was conducted by using organic waste as expansive soil stabilization material. Organic wastes that use in this research includes sugarcane bagasse, used tea leaves, rice husk ash, eggshell, and palm fiber. These five organic wastes will be combined with South Jakarta, Cikupa, Bekasi 1, Cikarang, and Bekasi 2 soil sample. All of these samples will be tested with penetrometer and free swell test. Based on the results, organic waste that most affected the increase of qu up to 69.56% and decrease of FSI up to 80.00% of South Jakarta, Bekasi 1, and Bekasi 2 samples is rice husk ash. Whereas organic waste that most affected the increase of qu up to 98.67% and decrease of FSI up to 53.41% of Cikupa and Cikarang samples is Sugarcane bagasse.

Shallow mixing and column performances of lime, fly ash and gypsum on the stabilization of swelling soils

Swelling soils are problematic in terms of geotechnics, and they require mitigation actions in preliminary works. The most commonly used method to mitigate the damage caused by swelling soils is to stabilize the soil with chemical additives by using shallow mixing or column techniques. It is important to determine the most suitable additive material and the most appropriate technique when stabilizing swelling soils. The aim of this study is to investigate shallow mixing and column performances of various additives on the stabilization of swelling soils. Lime, fly ash and gypsum were chosen as the additives for this purpose. The study was conducted in the laboratory by creating the model of the land at the laboratory scale. Two different small scale models were designed for each additive, one for investigating their shallow mixing performances, and the other one for their column performances. A curing time of 4 months was considered for all of the models. At the end of the curing time, in order to determine the changes on the swelling behaviour of the soil, free swelling test was carried out on the specimens taken from the small scale model boxes. The results showed that the best improvement was achieved with lime for both techniques with reductions of 99.8% and 51.9% in the swelling percent of the soil when using the shallow mixing and column techniques, respectively. Gypsum, on the other hand, exhibited the lowest performance for both techniques by reducing the swelling percent of the soil by 65.42% with the shallow mixing technique and 25.3% with the column technique. Lastly, the shallow mixing technique showed 47.9%, 64.41% and 40.12% higher performances than the column technique for lime, fly ash and gypsum, respectively.

Effects of Laumontite Hydration/Dehydration on Swelling Deformation and Slake Durability of Altered Granodiorite

ABSTRACT The mineral laumontite can undergo hydration/dehydration reactions at room temperature. The hydration/dehydration produces a 3 to 6 percent volume change in the unit cell. The effects of laumontite hydration/dehydration on swelling and slake durability were investigated using altered granodiorite containing laumontite from the dam foundation of Yangfanggou Hydro Power Station, Sichuan, China. The occurrence of laumontite in altered rocks was first determined by petrological analysis. Typical samples were then collected for laboratory X-ray diffraction (XRD) analyses, free swelling tests, and slake durability index (SDI) tests. The test results were analyzed to determine the quantitative relationships between laumontite content, maximum axial strain, and slake durability index. We found that hydration of laumontite led to rock swelling. As laumontite content increased, maximum axial strain increased linearly; if water penetrated the rock quickly, swelling occurred over a short period. The hydration/dehydration of laumontite decreased slake durability of the rock; the SDI decreased approximately linearly as laumontite content increased.

Effect of ageing on the properties of a clay soil contaminated with glycerol

ABSTRACT Effect of ageing on the behaviour of a contaminated clay soil was studied. Contaminated soil samples were prepared by adding 4, 7 and 10% solution of glycerol to an uncontaminated soil. Atterberg limits, compaction, free swelling and unconfined compression strength (UCS) tests were performed on the contaminated soil samples at ages of 0 (immediate), 7, 14, 30, 60 and 90 days. The results show that the Atterberg limits are increased with increasing the percent of glycerol and ages except samples with 0 ages. For sample contaminated with 10% glycerol at age of 90 days the reduction in maximum dry unit weight and the increase in optimum water content were 5.4% and 16.7%, respectively. The results also indicate that the potential of swelling is proportional to the percents of glycerol and ages. The changes in the value of UCS are in opposite direction with percent of glycerol and ages. The reduction in strength of contaminated samples with 7 and 10% glycerol at age of 90 days are 62 and 68%, respectively, compared to the samples that were contaminated with 4% glycerol solution. Scanning electron microscopy (SEM) shows that increasing the age will change the structure and behaviours of soil samples.

Studies on Hydration Swelling and Bound Water Type of Sodium- and Polymer-Modified Calcium Bentonite

Modified calcium bentonite (Ca-bentonite) is extensively used in engineered barrier systems (EBSs) for municipal and industrial disposal sites due to its high swelling potential and low hydraulic conductivity. However, few studies have focused on the micromechanism of hydration and swelling under the effect of inorganic chemical solution. In this study, free swell index (FSI) and the type and content of modified Ca-bentonite bound water under the inorganic chemical solution were quantitatively studied by using the free swell test and nuclear magnetic resonance (NMR). According to the results, modification of sodium and polymer significantly increases the FSI of Ca-bentonite, bringing it close to that of natural sodium bentonite. In addition, the chemical stability of polymer-modified bentonite is significantly higher than that of sodium-modified bentonite but less than that of natural Na-bentonite. The FSI of modified Ca-bentonite decreases with the increase of cation valence and ionic strength. T2 distribution curves of the two types of modified bentonite are three-peak curves. With the increase of ionic strength, the content of total water and permeated hydrated water (accounting for 69%–95%) in bentonite decreases gradually, whereas the surface hydration water (accounting for 2%–31%) and free water content (accounting for 0–15%) increase. A uniform linear relationship exists between the FSI and corresponding total peak area of NMR (independent of ion valence, concentration, and bentonite type). Furthermore, a linear relationship exists between the FSI of the same type of bentonite and the T2 relaxation time. Research results can provide data and theoretical basis for quantitative analysis and mechanism of the hydration swelling of bentonite.

CLAYEY SOIL AMENDMENT BY HYDROPHILIC NANO BENTONITE FOR LANDFILL COVER BARRIER: A CASE STUDY

Methane and carbon dioxide are of major concern as greenhouse gases; the landfills have the problem of controlling these gases. Al Akaider in Jordan is the second biggest landfill suffers controlling gases as it lacks a cover design system. In this work, the main goal is to investigate the appropriateness of amended expansive clayey soil in Irbid as a cover barrier. The expansive soil is unwanted in construction projects, thus the modification of this expelled soil enables using it as a low cost landfill cover barrier. In this research, the effect of adding nano-clay material (Hydrophilic Nano Bentonite) on the geotechnical characteristics, hydraulic conductivity, and gas transport coefficients of the clayey soil are studied. The soil samples were obtained from Irbid city. Unconfined compressive strength and free swelling tests were performed on soil samples with different percentages of nano-clay added in the range (0.1% to 1.2%) by weight. The results indicated that the addition of nano-clay at low percentages increases the strength of expansive soil up to 315 kPa at 0.6% of nano-clay and the swelling potential decreased dramatically with the addition of nano-clay. The optimal percent of nano-clay was found to be 0.6%. The intrinsic permeability of the amended soil was 6.03×10–15 m2. The average values of fluid transport coefficients were determined at 25 °C. The hydraulic conductivity for water was about 6.5×10–10 m/s. Gas conductivity coefficients for CO2 and CH4 were 5×10–9 m/s and 2.5×10–9 m/s respectively. Gas diffusion coefficients for CO2 and CH4 were 3×10–6 m2/s and 4×10–6 m2/s respectively.

Variation in Geotechnical Behavior of Bentonite-Soil Blends in the Salty Environment of Liner

Waste management is one of the most critical issues in Bangladesh. Every day thousands of people are dumping their daily household wastes in some specific dumping sites. The leachate that is being generated from these wastes is changing the quality of the soil by mixing with the surrounding soil and is also contaminating the groundwater. Several components such as water and different varieties of salt are found in the leachate. This paper represents the findings of a recent study on the effect of inorganic NaCl salt on certain geotechnical properties of clay soil mixed with bentonite used as a liner material. The clay soil was collected from a local household waste dump in the Khanabari area of Khulna district. The soil was mixed with different percentages of bentonite (10% & 20%) to test the effect of various concentrations (0M, 0.1M & 1M) of inorganic salt. For this reason, laboratory tests like compaction test, liquid limit test, 1-D consolidation test, permeability test, free swell test and pH test were performed. Finally, it was concluded that a salty environment could have a significant effect on the mixture's geotechnical characteristics.

EFFECTS ON MODIFIED PROPERTIES OF EXPANSIVE CLAY SOIL USING WASTE HOLLOW CONCRETE BLOCK (HCB) AND CEMENT PLASTER WASTE MATERIALS FOR SUBGRADE CONSTRUCTION

Expansive soils characterized by changing its volume and strength due to seasonal variations. Due to this volume changes, expansive clay soil caused many problems in road construction and is relatively common in Ethiopia. As a result, such types of soil are not adequately for road construction, which requires proper attention. The focus of this study was to improve the engineering properties of the expansive clay soil with the addition of waste materials to use as a subgrade construction material. Soil samples were taken from three locations within the study area and performed laboratory tests for the moisture content, specific gravity, free swelling, Atterberg limit, and compaction test on its natural state. The expansiveness of the soil from the three locations were determined. The highest value of expansiveness from these samples considered for the experiment by the addition of waste materials concentration with 5%, 10% 20%, and 30% by weight. Test results indicated that the moisture content, free swelling, specific gravity Atterberg limit decreased, while the maximum dry density increased as the concentration of waste material increase. Hence, the minimum amount of waste materials comprised of 10% that will improve the strength of expansive clay soil for use in road subgrade construction.

Study of the Potential Use of Clay from Muratara Regency as Subtituent Materials for API Bentonite for Drilling Mud based on API RP 13B Mud Slurry Properties Tests

Bentonite, especially Sodium (Na) Bentonite is a type of clay that is used as a basis for water-based drilling mud in the of oil and gas wells drilling throughout the world including Indonesia, bentonite used in Indonesia is still partially imported from abroad. Sodium Bentonite can be substituted with ordinary clay which is treated by beneficiation throught addition of Na2CO3. The area of Musi Rawas Utara (Muratara) Regency of South Sumatra Province contains clay reserves resulting from pyroclastic deposit which will be investigated as potential subtitutional materials of imported API Bentonite.
 Clay samples from 6 different locations were prepared by first looking for the best % swell of sample beneficiation combination from all over the 36 combinations through the free swell test, the results obtained that the 4% BWOC Na2CO3 combination gave the best % swell. From this, 24 samples were prepared for various measurements of mud properties using standard equipment and procedures following the API RP 13 B for water-based mud with drilling grade Na-bentonite (API Bentonite) as standard material.
 The test includes 7 properties which are divided into 16 measurement units namely density, rheology, filtration, solid and liquid content, sand content, pH and methylene blue capacity etc. The test results show that the Na2CO3 beneficiation is able to change ionically the characteristics of the clay, but from the aspect of the suitability of the value of each test parameter to the standard value shows that none of the samples has full compatibility, which is mean that Muratara clay technically cannot be used as a substituent material of API Bentonite.

THE PROPERTIES OF LATERITE SOILS AS THEY AFFECTS THE STABILITY OF BITUMEN STABILISED BRICKS

The purpose of this study is to determine the properties of laterite soil and how they affect the stability of bitumen stabilized bricks. The samples for the study were disturbed samples sourced in seven locations in Adamawa State. Each sample weigh 20kg transported to the laboratory for tests. The tests conducted include: Sieve Analysis, sedimentation Test, Liquid Limit Test, Plastic Limit Test, Activity Ratio, Free Swell Test and Optimum Moisture Content Test. Three research questions guided the study and the findings of the study include; that the samples shows increase percentage smaller or less than 63 microns sizes, which indicate that the samples are more of silt and clay particles. The properties of the laterite soils taken for the study include; liquid limit ranging from 35-49, plasticity index from 11-14 percent, the activity ratio ranges from 1.0-1.4, and free swell test shows less than 100 percent. One of the recommendations made was that, Laterite soil stabilization should precede a study of the particles size distribution to ensure that the categories of the Laterite soil can bland with the bitumen emulsion to envelop the particles for the purpose of preventing moisture movement in the bricks.

Effect of industrial wastes and lime on strength characteristics of clayey soil

PurposeThe purpose of this paper is to attempt to use two industrial wastes; waste foundry sands (WFS) and molasses (M) along with lime (L) to improve the strength characteristics of clayey soil.Design/methodology/approachIn the first part of the study, the optimum percentages of materials (WFS, molasses, lime) have been found out by conducting differential free swell (DFS) and consistency limit tests on clayey soil by adding various admixtures. The second and third part of the study investigates the compaction behaviour and unconfined compressive strength (UCS) of clayey soil on addition of optimum amount of various materials alone and in combination with each other. Finally, the micro-structural behaviour of addition of optimum percentages of lime, WFS and molasses using Scanning electron microscopic technique has been discussed.FindingsThe laboratory results revealed that the addition of optimum content of lime along with WFS and molasses reduced DFS and plasticity index and increased maximum dry density and UCS values. The microstructural behaviour showed that the presence of lime and molasses filled the voids present in the soil and the addition of WFS helped in providing compact structure, thus improving the strength characteristics.Practical implicationsThe study will be helpful in designing low-cost pavement designs for rural roads.Social implicationsThe adverse effect of waste materials on environment may be solved by using them in improving the strength characteristics of clayey soils, thereby providing healthy environment to living beings.Originality/valueThe study will help to provide low-cost methods to improve strength characteristics of clayey soil along with the use of waste materials; the disposal of whose is a challenging task.

Sensitivity of bentonite swelling to pore water activity

The deformability of bentonites is strongly conditioned by their salinity conditions. Consequently, the chemomechanical coupling must be taken into account to characterise correctly the deformational behaviour of these materials. Some models have been developed that account for this coupling. These models, which usually assume a double-porosity approach to characterise the structure of compacted bentonite, idealise the geochemical system, commonly using a simplified definition of the activity of the species dissolved in the aqueous solutions present in the bentonite pores. In this paper, the significance of the formulation used to calculate the activities is analysed. As a sensitivity exercise, the extended Debye–Hückel model is applied to estimate the activity coefficients of the species in the macrostructure. The exercise is conducted by simulating vertical free-swelling tests under different salinity conditions. It is shown that when the salinity conditions are not negligible, the results are improved using this illustrative model compared with the case in which the activity of the species was assumed equal to their concentration. Although the formulation of the activity coefficients could be improved for higher-salinity conditions, this study highlights the sensitivity of the bentonite mechanical behaviour to the activity definition.

Swelling Curve in Terms of Effective Stress for Expansive Clays

Expansive soils can present an unsaturated state where the soil exhibits volume changes due to both moisture variations that change the state of stresses and moisture variations that interact with its mineralogical characteristics. These special kinds of soils are normally clay type soils that had suffered isomorphous substitution creating a charge imbalance of the clay mineral crystals. This imbalance promotes the trapping of water molecules by the clay particles. It is commonly assumed that a high plasticity index can be an indication of a clay´s high swell potential. However, in arid regions, it is possible to have clays with very high swell potential and low plasticity indexes due primarily to a decrease in the state of effective stress, which will produce expansion of the material. It is common practice to study the swelling characteristics of these soils by performing free-swell tests that can be used for designing removal and replacement backfills or drilled shafts. However, the expansion percentage obtained from this type of test is actually in terms of total stresses and not in terms of effective stress, as it is commonly assumed. Moreover, it is highly dependent on the magnitude of the preload used. This paper presents some efforts made to obtain the swelling part of the curve in terms of effective stresses from the traditional free-swell test. It was hypothesized that the shape of this curve could either have the shape of the rebound curve from a saturated consolidation test or a shape similar to the soil-water characteristic curve.

Laboratory study on the effect of leachate type to swelling behavior of bentonite

Bentonite is well known as highly plastic, swelling clay material, the product of volcanic ash. An experimental test of the effect of leachate type on swelling behavior of bentonite has been conducted. Four types of liquids, tap water, 10 g/l of NaCl solution, 11.1 g/l of CaCl2 solution, and 100 ml/l of ethanol solution were used in the tests. Liquid limit, plastic limit, free swelling index, and swelling pressure tests were carried out to evaluate the relative swelling ability of bentonite when interacted with different leachate types. The result of free swelling tests indicated bentonite swelled higher when interacted with tap water and ethanol solution compare with NaCl solution and CaCl2 solution as a liquid. The value of liquid limit and plastic limit of bentonite for ethanol solution and CaCl2 solution were highest and lowest among liquid tested, respectively. The result also showed that bentonite has the highest swelling pressure when contacted with tap water but opposite for NaCl solution.

Experimental study on the 1-D free swelling of compacted bentonite

This paper presents a new designed 1-D free swelling test of compacted bentonite in glass tubes to simulate the process by which the bentonite cushion in the nuclear waste disposal reservoir swells and squeezes into the crack after absorbing the fissure water from surrounding rock. Deionized water and NaCl, Na2SO4, CaCl2 solutions with different concentrations were used as soaking solutions, and the change of the specimen height with time was recorded until the swelling completed. The effects of initial dry density, initial water content, and soaking solution concentration and type on the swelling deformation of bentonite were analyzed. Results show that the maximum swelling strain, almost independent from initial water content, increases with the initial dry density. The increase in the concentration of the salt solution reduces the free swelling deformation, and the degree of inhibition is related to the type of the salt solution. The effect of the concentration and type of the salt solution on swelling property can be uniformly reflected by the osmotic suction that acts as an additional stress applied on bentonite and is quantified as osmotic pressure item of the total effective stress proposed previously that controls the swelling strain of compacted bentonite. Then, the maximum swelling strains of the compacted bentonite under different soaking solutions in 1-D free swelling test can be predicted by a uniform power-law relationship with the total effective stress.

Bentonite Extrusion into Near-Borehole Fracture

In this paper, we discuss laboratory experiments of bentonite swelling and coupled finite element simulations to explicate bentonite extrusion. For the experiments, we developed a swell cell apparatus to understand the bentonite migration to the near-borehole fracture. We constructed the swell cell using acrylic, which comprised of a borehole and open fracture. Initially, the borehole of the swell cell was filled with bentonite and liquid. Then, the apparatus was sealed for observations. Due to the liquid saturation increase of bentonite, its swelling pressure increased. The developed pressure caused the extrusion of bentonite into the fracture, and the flow of bentonite from the borehole decreased with time. Moreover, for the effectiveness of bentonite-based plugging, there is a limiting condition, which represents the relation between the maximum bentonite migration length with the fracture aperture. Additionally, we also performed the bentonite free swelling test to assess the swelling potential to the fluid salinity, and we observed that with the increase of the salinity, the swelling potential decreased. In addition, we present a fully coupled two-phases fluids flow (e.g., liquid and gas) and deformation flow finite element (FE) model for the bentonite column elements and swell cell model. We also combined the Modified Cam Clay (MCC) model and the swelling model for the bentonite deformation flow model. Then, we also present the validation of the bentonite model. To model other sub-domains, we used the poro-elastic model. Additionally, we obtained the transition between the wetting phase (i.e., liquid) and non-wetting phase (i.e., gas) using the Brooks–Corey model. From the finite element results, we observed that due to the liquid intrusion into the bentonite, the developed capillary pressure gradient results in a change of the hydro-mechanical behavior of the bentonite. Initially, we observed that due to the high capillary pressure gradient, the liquid saturation and the swelling pressure increased, which also decreased with time due to a reduction in the capillary pressure gradient. Thereby, the swelling pressure-induced bentonite migration to the fracture also decreased over time, and after the equilibrium state (for a negligible pressure gradient), there was no significant transport of bentonite into the fracture.