Raymond N. Yong

Buffer capacity and lead retention in some clay materials.

The link between buffer capacity and the ability of clays to retain Pb in interactions between Pb contaminant leachate and the clays, has been studied, using a natural clay from Quebec and laboratory-prepared clays (kaolinite, illite, and smectite). The retention of Pb in the clay suspensions as they received increasing amounts of acid was investigated, and the results examined in terms of the buffer capacity of the clays. As the clays receive increasing amounts of acid (e.g. akin to addition of acid leachate), high amounts of Pb can be retained if the buffer capacity prevents the pH from dropping to values where precipitation mechanisms are not operative. The high carbonate content in the illite gave it a higher buffer capacity than the smectite and natural clay, and permitted it to retain high amounts of Ph. High Pb uptake by the clays can affect the buffer capacity and the Pb retention capacity.

Analysis and prediction of tyre-soil interaction and performance using finite elements

Abstract The finite element method [FEM] of analysis previously developed for prediction of rigid wheel-soil interaction is improved and extended to take into account (a) the effect of flexibility of tyre carcass where energy losses now occur in development of mobility, (b) a simpler requirement for specification of boundary condition using input loading, and (c) normal and tangential load stress from the tyre distributed across the tyre-soil interface and varying with slip. The comparisons of analytically computed (predicted) drawbar pull with actual experimentally obtained drawbar pull results for tests in three types of tyres show good correlations. The effect of inflation pressure on development of tyre deformation energy losses can be seen from the analytically computed values.

Finite element analysis of plane soil cutting

Abstract This study develops the finite element method (FEM) of solution to provide a theoretical means for determination of soil performance under the actions of a cutting blade—and the forces required to promote cutting. The developed FEM takes into account the effect of progressive and continuous cutting of the clay soil at the tip of the blade, with possible development of failure zones in the soil whenever the shear strength of the soil is exceeded. The solution provides detailed information on stress and deformation fields in the soil, together with tangential and normal pressures developed at the blade soil interface Correspondence between theoretically computed displacement fields and measured values has been obtained. In addition, the theoretically computed and experimentally measured values for forces developed in blade thrust are seen to be in close agreement.

Prediction of wheel-soil interaction and performance using the finite element method

Abstract In this experimental-analytical study of wheel-soil interaction, a technique based on the finite element method is used for predicting continuous wheel performance and subsoil response behaviour. The evaluation of wheel-soil interaction performance at any degree of slip is performed using energy principles. The analytical technique utilizes experimentally determined wheel-soil particle path as displacement input for load simulation to predict the soil response beneath the wheel. An incremental loading approach is adopted to satisfy as closely as possible the soil loading path. The solution requires initial conditions which establish the soil at zero energy level (no stress history) and proceeds to stationary wheel positions with wheel-soil penetration equal to its dynamic sinkage. The method of analysis then proceeds to the steady-state wheel travel mode. The predicted drawbar pulls and subsoil behaviour results are presented and shown to compare well with the experimentally measured values.

Interparticle action and rheology of kaolinite-amorphous iron hydroxide (ferrihydrite) complexes

Abstract The complexes of kaolinite and amorphous iron hydroxides (ferrihydrite) initially prepared at pH 3.0 and 9.5 were brought to equilibrium at different pH values at pH 3–10. Bingham yield stress for the suspensions of the complexes have been examined as a function of pH. The complexes prepared at pH 3.0 and 9.5 both gave higher Bingham yield stress than the kaolinite in higher pH range, and the amorphous iron hydroxides in the complexes prepared at 9.5 were more effective in enhancing yield stress. The results are discussed in terms of the charge characteristics of the amorphous iron hydroxide and its association with the kaolinite surfaces by means of electron microscopy and zeta potential and surface area determinations.

Particle interaction and rheology of illite-iron oxide complexes

The Bingham yield stress for suspensions of illite-iron oxide complexes is examined as a function of pH and iron oxide content. Addition of iron oxides to illite increased the yield stress over a pH range of 3 to 10. With increasing pH the yield stress decreased for the complexes with iron oxides of 2 and 5% while the complexes with iron oxides of 7, 10, and 20% exhibited the maximum yield stresses at pH values from 6 to 8. The iron oxides which are not associated with the illite enhanced the yield stress more than the iron oxides precipitated on the illite surfaces. The yield stress for the complexes was correlated with their zeta potential, and the higher yield stress is considered due to smaller interparticle repulsion.

Containment of High-Level Radioactive and Hazardous Solid Wastes with Clay Barriers

Introduction Radioactive and Hazardous Solid Waste Isolation Nature of Clays Clay-water Reactions and Partly-saturated Water Transport Contaminant-clay Interactions and Impacts Thermal, Hydraulic, Mechanical, Chemical and Biological Processes Clay Evolution and Long Term Buffer/Barrier Performance Field and Mockup Experiments Modelling for Prediction and Performance Assessment Safety Assessment and Performance Determination

Tyre flexibility and mobility on soft soils.

Abstract Five model tyres were tested in the soil bin to investigate the effects of wheel flexibility on the tyre-soil performances. Two different soil types were used together with various inflation pressures which governed the tyre flexibility. The results confirm that tyre flexibility contributes significantly to the development of all the energy components [equation (1)] in the tyre-soil system. As can be seen from the contrasting performances shown, increasing the inflation pressure may allow for a favourable increase in the drawbar pull in one soil (frictional soil) so long as the input energy available can be increased, whilst the reverse may be true in the case of the other (clay) soil. The finite element model used satisfactorily confirms the measered values obtained and is seen to be able to account for tyre flexibility as shown in Figs. 11–14.

Prediction of salt influence on unfrozen water content in frozen soils

Abstract The influence of salts in the pore water in freezing soils is examined from the experimental viewpoint, using the differential scanning calorimetry technique for generation of multiple endotherms of the frozen test samples. The experimental values obtained for montmorillonite, kaolinite and grundite, are evaluated in terms of unfrozen water contents for the respective soils at various subfreezing temperatures for various concentrations of NaCl. Comparison of experimental values with theoretical predictions using a combined salt exclusion and diffuse double-layer model shows excellent quantitative agreement for the montmorillonite soil samples, but only qualitative agreement for the kaolinite and grundite soils. The reasons for this lie in the theoretical model requirement for interlamellar migration of water in soil freezing for suitable application of the diffuse double-layer part of the model.

Development of a criterion for road surface roughness based on power spectral density function

Abstract This study has demonstrated that the non-contact acoustical transducer is a reasonable sensor for reflecting the road roughness profile, and the procedure is much faster in detecting the road surface roughness as compared to other measurement devices. Thus, it is a very promising sensor with regard to road roughness measurement. Furthermore, the ISO may be employed to classify the road grade. However, the assumed linearity in the PSD on a log-log graphical representation may not be true in reality, especially in the lower frequency band. Therefore, a new approach to classify road surface roughness is to be developed.