Micellar Electrokinetic Remediation of TNT From Soil.

An assessment of the feasibility of micellar electrokinetic (EK) remediation of TNT from soils is presented. Batch solubilization tests and bench scale EK tests were conducted to select the best candidate surfactant and to evaluate the efficiency of removal of TNT from a real world soil. From batch tests, it was found that SDS gave the best desorption results among a group of candidate surfactants, which includes DOWFAX 8390 (anionic), Tween 80 and Brij 35 (nonionic) and CTAB and CTAC (cationic). Unenhanced and surfactant enhanced EK tests was unable to move substantial amounts of TNT across the specimen to the electrodes. TNT concentrations reduced significantly in the soil sample at sections closest to the cathode after EK processing. This was postulated to be due to transformation of TNT to TNT anions (Jackson-Meisenheimer anions or the Janovsky\u27s complex). EK tests with neutralization at the electrodes achieved both characteristics, i.e. improvement of electroosmotic flow and preventing TNT transformation to TNT anions. Changing the process parameters, such as improving electroosmotic flow, maintaining a constant pH across the medium and extending processing period also did not improve the process in terms of efficiency is evaluated by pulsing the process. The pulse type processing also did not improve electroosmotic flow nor it improved TNT transport for 5% Tween 80 solution. Electroosmotic flow significantly increased in pulse type loading with 20% methanol solution. From the limited data obtained, it is demonstrated that a pulse type loading may be a more efficient technique to drive pore fluid into the soil compared to a continuous current method. There is also evidence of improved transport of TNT in the soil specimen in this type of system. This study provides further evidence to demonstrate that nonpolar species such as TNT cannot be transported from soils by electroosmosis. The attempt to desorb, solubilize and polarize TNT by the formation of micelles with SDS, although successful in batch extraction through vigorous shaking, becomes ineffective in extracting TNT in bench scale EK experiments

One-Dimensional Consolidation of Kelang Clay

A study on the consolidation behaviour of Kelang clay is presented in this paper. The soil samples taken near the Port of Kelang showed that the clay can be divided into upper marine and the lower river clays. The initial distinction was based on the existence of sea shells in the upper deposits and none in the lower deposits. It has been shown that these two clays have different consolidation properties as well as other basic geotechnical characteristics. Consolidation history indicated that Kelang clay is normally consolidated and may be classified as a high compressibility clay. The overburden pressure due to fill must be neglected in order to obtain the true over consolidation ratio. It was also found that the correlation given by Terzaghi and Peck (1967) provided the best estimates for the compression index, particularly that of the marine clay

Fuzzy Logic System for Slope Stability Prediction

The main goal of this research is to predict the stability of slopes using fuzzy logic system. GeoStudio, a commercially available software was used to compute safety factors for various designs of slope. The general formulation of the software could analyze slope stability using various methods of analysis i.e. Morgenstern-Price, Janbu, Bishop and Ordinary to calculate the safety factors. After analyzing, fuzzy logic was used to predict the slope stability. Fuzzy logic is based on natural language and conceptually easy to understand, flexible, tolerant of imprecise data and able to model nonlinear functions of arbitrary complexity. Several important parameters such as height of slope, unit weight of slope material, angle of slope, coefficient of cohesion and internal angle of friction were used as the input parameters, while the factor of safety was the output parameter. A model to test the stability of the slope was generated from the calculated data. This model presented a relationship between input parameters and stability of the slopes. Results showed that the prediction using fuzzy logic was accurate and close to the target data

Micromechanical Formulation of the Yield Surface in the Plasticity of Granular Materials

An equation is proposed to unify the yield surface of granular materials by incorporating the fabric and its evolution. In microlevel analysis by employing a Fourier series that was developed to model fabric, it is directly included in the strength of granular materials. Inherent anisotropy is defined as a noncoaxiality between deposition angle and principal compressive stress. Stress-induced anisotropy is defined by the degree of anisotropy and the major direction of the contact normals. The difference between samples which have the same density (or void ratio) but different bedding angles is attributed to this equation. The validity of the formulation is verified by comparison with experimental data

Reliability Evaluation of Slopes Using Particle Swarm Optimization

The objective of this research is to develop a numerical procedure to reliability evaluation of earth slope and locating the critical probabilistic slip surface. The performance function is  formulated using simplified Bishop’s limit equilibrium method  to calculate the reliability index. The reliability index defined by Hasofer and Lind is used as an index of safety measure. Searching the critical probabilistic surface that is associated with the lowest reliability index will be formulated as an optimization problem. In this paper, particle swarm optimization is applied to calculate the minimum Hasofer and Lind reliability index and critical probabilistic failure surface. To demonstrate the applicability and to investigate the effectiveness of the algorithm, two numerical examples from literature are illustrated. Results show that the proposed method is capable to achieve better solutions for reliability analysis of slope if compared with those reported in the literature

Elevated Temperature Performance of Multiple-Blended Binder Concretes

Concretes that contain binary-blended binders (BBB) and ternary-blended binders (TBB) incorporating thermally activated alum sludge ash (AASA), silica fume (SF), ground-granulated blast-furnace slag (GGBS) and palm oil fuel ash (POFA) are exposed to temperatures as high as 800 °C. The water-binder ratio of the multiple-blended binder (MBB) concretes was 0.30, and the total binder and polypropylene (PP) fibre contents were 493 and 1.8 kg/m3, respectively. The elevated temperature performance of the MBB concretes is evaluated in terms of the mass loss, compressive strength, ultrasonic pulse velocity (UPV) and surface cracks. The concrete strength deteriorated significantly due to elevated temperature up to 800 °C, but the residual strength of the BBB containing 15 % AASA was higher than that of the control and 20 % AASA concretes. High-temperature exposure decreased measured UPV values. The concrete weight loss was more pronounced for TBB concretes. The elevated temperature performance of all of the TBB concretes was better than that of the BBB concretes with the same AASA replacement levels. It was observed that PP fibres help reduce spalling. BBB concrete containing 15 % AASA combined with either SF or GGBS or POFA exhibits superior performance at elevated temperature than Portland cement concrete at the same mix design proportion

Geotechnical Behaviour of a Malaysian Residual Granite Soil

Granite soil is widely distributed in Peninsular Malaysia. Steep terrain, heavy seasonal rainfall and deep tropical weathering are the main causes of numerous slope failures in this formation. Information on the shear strength of soil and its behaviour is essential for safe and economic design geotechnical structures. In order to study the fundamental behaviour of this residual soil, direct shear tests were conducted on remoulded and undisturbed specimens. The soil was subjected to soaked and unsoaked conditions to study the effects of wetting. In addition, triaxial CD and C tests were also conducted. The behaviour in direct and triaxial shear did not indicate peak strength in the stress-strain plots in all specimens. In direct shear tests, significant volume change behaviour was observed between unsoaked and soaked specimens. The shear strengths of soaked specimens were significantly lower than that of unsoaked specimens. Thus the effects of wetting is very obvious. In triaxial tests, the strength parameters (c', tP') for CD and CD tests were not found similar. All important observations are highligted in the paper