Swelling pressure of a divalent-rich bentonite: Diffuse double-layer theory revisited

Physicochemical forces are responsible for the swelling pressure development in saturated bentonites. In this paper, the swelling pressures of several compacted bentonite specimens for a range of dry density of 1.10–1.73 Mg/m3 were measured experimentally. The clay used was a divalent-rich Ca-Mg-bentonite with 12% exchangeable Na+ ions. The theoretical swelling pressure–dry density relationship for the bentonite was determined from the Gouy-Chapman diffuse double-layer theory. A comparison of experimental and theoretical results showed that the experimental swelling pressures are either smaller or greater than their theoretical counterparts within different dry density ranges. It is shown that for dry density of the clay less than about 1.55 Mg/m3, a possible dissociation of ions from the surface of the clay platelets contributed to the diffuse double-layer repulsion. At higher dry densities, the adsorptive forces due to surface and ion hydration dominated the swelling pressures of the clay. A comparison of the modified diffuse double-layer theory equations proposed in the literature to determine the swelling pressures of compacted bentonites and the experimental results for the clay in this study showed that the agreement between the calculated and experimental swelling pressure results is very good for dry densities less than 1.55 Mg/m3, whereas at higher dry densities the use of the equations was found to be limited

Swelling behavior of compacted bentonite-sand mixture during water infiltration

A laboratory-based water infiltration test was conducted with compacted Calcigel bentonite-sand mixture (50:50) at room temperature to mimic the transient hydration of a backfill material in nuclear waste repository conditions. The test was performed with an innovative column-type experimental device, which facilitated the continuous and non-destructive measurements of temperature, relative humidity, water content and total stresses in both axial and lateral direction at various preselected locations along the height of soil sample. The effect of groundwater geochemistry on the bentonite hydration process was not considered in this study. The distilled water was supplied from the bottom-end under 15-kPa hydration pressure for a period of 349 days to mimic the water ingress from the host rock. The test results highlighted the hydration-induced heterogeneity in the material and its effect on the lateral swelling pressure development along the height of soil sample. The axial swelling pressure measurements revealed the factors, which affect the stress-transfer mechanism between both the ends. The simultaneous measurements of relative humidity and water content indicated the porosity redistribution close to the hydration-end during the test

An evaluation of osmotic technique under ultraviolet germicidal irradiation exposure

The osmotic technique, which uses polyethylene glycol (PEG) solutions of varying concentrations with semipermeable membranes of different molecular weight cutoffs (MWCO), is commonly used to apply suction in soils. Cellulose acetate membranes which are most commonly used, are susceptible to microbial attacks. This in turn will lead to the intrusion of PEG into soil specimens. Osmotic and vapour equilibrium techniques are often used to establish drying suction-water content soil-water characteristic curves (SWCC). In this study, suctions of 0.11 to 300 MPa were applied on Andrassy bentonite slurries. At higher applied suctions, the osmotic tests were carried under short length ultraviolet germicidal irradiation (UVGI). In addition, Atomic Force Microscopy (AFM) and Fourier Infrared (FTiR) were employed to evaluate the changes in the semipermeable membranes and PEG molecules, respectively. The water content of the clay obtained from the osmotic tests was found to be greater at the overlapping suction region. Interestingly, under UVGI exposure, the water content was found to be in good agreement with the water content determined using the osmotic technique at low suctions and the vapour equilibrium technique at higher suctions. FTiR spectrum and AFM results revealed that some changes had occurred on both the PEG and in the membrane pore sizes. However, these changes did not affect the final water content in the bentonite and therefore, more precise suction-water content SWCC for the clay could be established

Response of compacted bentonites to thermal and thermo-hydraulic loadings at high temperatures

The final disposal of high-level nuclear waste in many countries is preferred to be in deep geological repositories. Compacted bentonites are proposed for use as the buffer surrounding the waste canisters which may be subjected to both thermal and hydraulic loadings. A significant increase in the temperature is anticipated within the buffer, particularly during the early phase of the repository lifetime. In this study, several non-isothermal and non-isothermal hydraulic tests were carried on compacted MX80 bentonite. Compacted bentonite specimens (water content = 15.2%, dry density = 1.65 Mg/m3) were subjected to a temperature of either 85 or 150 °C at one end, whereas the temperature at the opposite end was maintained at 25 °C. During the non-isothermal hydraulic tests, water was supplied from the opposite end of the heat source. The temperature and relative humidity were monitored along predetermined depths of the specimens. The profiles of water content, dry density, and degree of saturation were established after termination of the tests. The test results showed that thermal gradients caused redistribution of the water content, whereas thermo-hydraulic gradients caused both redistribution and an increase in the water content within compacted bentonites, both leading to development of axial stress of various magnitudes. The applied water injection pressures (5 and 600 kPa) and temperature gradients appeared to have very minimal impact on the magnitude of axial stress developed. The thickness of thermal insulation layer surrounding the testing devices was found to influence the temperature and relative humidity profiles thereby impacting the redistribution of water content within compacted bentonites. Under the influence of both the applied thermal and thermo-hydraulic gradients, the dry density of the bentonite specimens increased near the heat source, whereas it decreased at the opposite end. The test results emphasized the influence of elevated temperatures (up to 150 °C) on the thermo-hydro-mechanical response of compacted bentonites in the nuclear waste repository setting

Swelling pressure of a divalent-rich bentonite: Diffuse double-layer theory revisited

[1] Physicochemical forces are responsible for the swelling pressure development in saturated bentonites. In this paper, the swelling pressures of several compacted bentonite specimens for a range of dry density of 1.10–1.73 Mg/m3 were measured experimentally. The clay used was a divalent-rich Ca-Mg-bentonite with 12% exchangeable Na+ ions. The theoretical swelling pressure–dry density relationship for the bentonite was determined from the Gouy-Chapman diffuse double-layer theory. A comparison of experimental and theoretical results showed that the experimental swelling pressures are either smaller or greater than their theoretical counterparts within different dry density ranges. It is shown that for dry density of the clay less than about 1.55 Mg/m3, a possible dissociation of ions from the surface of the clay platelets contributed to the diffuse double-layer repulsion. At higher dry densities, the adsorptive forces due to surface and ion hydration dominated the swelling pressures of the clay. A comparison of the modified diffuse double-layer theory equations proposed in the literature to determine the swelling pressures of compacted bentonites and the experimental results for the clay in this study showed that the agreement between the calculated and experimental swelling pressure results is very good for dry densities less than 1.55 Mg/m3, whereas at higher dry densities the use of the equations was found to be limited

PERLINDUNGAN HUKUM TERHADAP PENYANDANG DISABILITAS YANG TERAMPAS KEMERDEKAANNYA DALAM SISTEM PERADILAN PIDANA

ABSTRAKWan Reni Ritanti, 2014PERLINDUNGAN HUKUM TERHADAP PENYANDANG DISABILITAS YANG TERAMPAS KEMERDEKAANNYA DALAM SISTEM PERADILAN PIDANAFAKULTAS HUKUM UNIVERSITAS SYIAH KUALA(vi, 55), pp., bibl., app.Ainal Hadi, S.H.,M.Hum.Adanya kasus yang menyebabkan terampasnya kemerdekaan penyandang disabilitas di luar negerimendorong lembaga PBB yakni UNODC dan lembaga non pemerintahan Law Reform Trust, serta beberapa negara untuk membuat aturan mengenai pemenuhan hak bagi penyandang disabilitas yang terampas kemerdekaannya, yang aturan tersebut didasarkan pada konvensi internasional mengenai hak penyandang cacat. Indonesia turut meratifikasi konvensi internasional ini menjadi UU No.19 Tahun 2011, namun pada kenyataannya pemenuhan hak terhadap penyandang disabilitas belum terimplementasi secara menyeluruh.Tujuan penulisan skripsi ini untuk menjelaskan pemenuhan hak terhadap penyandang disabilitas yang terampas kemerdekaannya dalam sistem peradilan pidana dan menjelaskan faktor-faktor yang mendorong perlunya dibuat aturan khusus mengenai pemenuhan hak bagi penyandang disabilitas yang terampas kemerdekaannya.Data dalam penulisan skripsi ini diperoleh melalui penelitian kepustakaan (library research), yang dilakukan untuk memperoleh data dengan memanfaatkan literatur seperti peraturan perundang-undangan, bahan kuliah, buku-buku, dan bahan-bahan lainnya yang dapat digunakan untuk memperoleh data sekunder.Hasil penelitian menunjukkan bahwa pemenuhan hak penyandang disabilitas yang terampas kemerdekaannya dalam sistem peradilan pidana di Indonesia masih belum ada sehingga dapat mengacu pada UU Pemasyarakatan dan Peraturan Kepala Polisi Republik Indonesia yang telah ada. Adanya instrumen internasional mengenai perlakuan terhadap tahanan cacat, adanya negara lain yang telah memiliki aturan mengenai penyandang disabilitas yang terampas kemerdekaannya, dan adanya kasus penyandang disabilitas yang terampas kemerdekaannya di luar negeri turut menjadi faktor yang mendorong perlunya Indonesia untuk membuat aturan khusus mengenai pemenuhan hak terhadap penyandang disabilitas yang terampas kemerdekaannya.Disarankan kepada pemerintah Indonesia untuk dapat membuat sebuah aturan khusus bagi penyandang disabilitas yang terampas kemerdekaannya demi kepentingan dimasa yang akan datang. Kepada aparat penegak hukum agar memiliki pengetahuan mengenai perlakuan dalam menangani penyandang disabilitas yang terampas kemerdekaannya dalam sistem peradilan pidana.Banda Ace

Consideration of microstructure in modelling the hydro-mechanical behaviour of unsaturated soils

The hydro-mechanical behaviour of unsaturated soils is often highly influenced by the microstructure; therefore, it can be beneficial to consider the effect of microstructure in a hydro-mechanical constitutive model. This paper considers the use of a microstructure-related model that adopts the effective degree of saturation as a microstructural index. The model can be used to reproduce the hydro-mechanical behaviour while the effect of the microstructure is considered. For comparison, a non-microstructuredependent model is also employed. The models are applied to simulate the behaviour of two different soilsand a comparison of the models’ performance in simulating triaxial test behaviour is made. Based on the comparison with experimental results and the non-microstructure-dependent model, it can be concluded thatthe adoption of the effective degree of saturation is beneficial to studying the hydro-mechanical behaviour of unsaturated soils affected by the microstructure

Microstructurally related model for predicting behaviour of unsaturated soils with double porosity in triaxial space

The microstructure can have an important impact on the hydraulic and mechanical behaviors of unsaturated soil; therefore, it must be considered in constitutive models to enable accurate predictions of soil behavior. This paper focused on the constitutive modeling of soils that exhibited a dual porosity structure. Based on the assumption that macro and micropores contained in the double porosity structure had different influences on the mechanical and hydraulic behaviors, the effective degree of saturation (Se) was selected as a microstructural index. This microstructural index was implemented within Bishop’s effective stress-based approach and the Glasgow coupled (GCM) and modified Cam-Clay models (MCC) were adopted as the basic framework for the development of a constitutive model. Typical samples of low expansive, nonexpansive, and collapsible soils with dual porosity were selected to validate the model’s performance, and the model performed well when compared with experimental data for isotropic compression, triaxial shear, and wetting tests