published_or_final_version / Civil Engineering / Master / Master of Philosophy

Numerical modeling using finite element method (FEM) is well-recognized as a powerful method for both engineers and researchers to solve boundary value problems. In the modeling of geotechnical problems, the analyses are often limited to simple static problems with either steady-state effective or total stress approach while the transient response (development and dissipation of excess pore water pressure, uex) is seldom considered. Besides, infinitesimal small soil deformation is usually assumed. The simulation is further complicated when the soil-structure interaction problems involve significant soil displacements; like a pile subject to negative skin friction (NSF) and a cone/pile penetration. However, conventional FEM analysis prematurely terminates due primarily to excessive mesh distortion. One could see that simulating a transient problem with large deformation and distortion remains a great challenge. In this study, advanced FE simulations are performed to give new insights into the problems of (1) a pile subject to NSF; and (2) a cone penetration. The transient response of the NSF problem is modeled with the fluid-coupled consolidation technique and geometric nonlinearity. The fluid-coupled cone penetration problem is modeled with a newly developed adaptive approach. The NSF and cone penetration simulations involve complex soil-structure interface modeling. Two types of modified interface responses are developed and verified which consider fluid coupling. The developed algorithm is applied to back analyze a case history of a pile subject to NSF induced by surcharge loading. Promising results were shown. Development of dragload and neutral plane (NP) with time is studied. NP locates at 75% of the pile embedded length (D) in long-term. Next, a parametric study is performed to investigate the influences of pile geometries, ground compressibility and loading conditions towards the pile responses. The long-term NP locates at around 0.55D to 0.65D in the studied engineering scenarios. The maximum downdrag can be up to 10% of the pile diameter. NP shifts upward when the head load increases. A simple design chart is proposed which helps engineers to estimate the long-term axial load distribution. An illustrative example is given to demonstrate the application and performance of the chart. The study is extended to investigate the cone penetration problem. An advanced adaptive method is developed and implemented into the FE package ABAQUS to resolve the problems of numerical instability, excessive mesh distortion and premature termination. The proposed method is verified by modeling a ground consolidation problem. Next, total stress back analysis of cone penetration is conducted with the proposed method. The development of cone factor predicted by the proposed method gives a better match with the laboratory result when comparing with the built-in ALE method. Next, the development and dissipation of uex during cone advancing with the proposed method and fluid-coupled technique is investigated. uex develops dramatically around the cone tip. The soil permeability is back calculated from the dissipation test and agrees well with the input value. It is believed that the construction effects of a press-in pile and the subsequence NSF on that pile can be modeled by utilizing the finding of this study. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

M. Tech. Engineering: Civil. / Discusses the objective of this study was to develop an equation to determine the penetrometer penetration rate (DN) of a pavement consisting of Bitumen Stabilised Material layers are constructed. The aim is to use laboratory results of Bitumen Stabilised Material and study the relations between the Indirect Tensile Strength and the Unconfined Compressive Strength. With the relations a penetrometer penetration rate (DN value in millimetre per blow) can be determined. This will enable the designer to apply the strength-balance concept on a pavement consisting of Bitumen Stabilised Materials. As indicated previously it was found during the design stages that only the Indirect Tensile Strength data on the Bitumen Stabilised Material was available. Developing an equation to convert the Indirect Tensile Strength data to a DN value will allow the designer to apply the strength-balance concept and adjust the design for improved performance life of a pavement.

Shaped charges are a well established type of projectile, subjected to a lot of research ever since emerging as a viable technology in the 1940s. The penetration achieved by shaped charges decreases with increased standoff distance. This is often attributed to the shaped charge jet losing its coherence. The Swedish Defence Research Agency however, noted no such loss of coherence in its experiments. An alternative explanation to the decrease of penetration was instead proposed. The object of this thesis was to investigate this proposed theory. To this end, the hydrocode Autodyn was used, modelling the impact of a high-velocity projectile into a generic target and analysing the resulting behaviour of the target. Several setups were used and several parameters were considered when evaluating the results. The conclusion of this thesis is that the alternative explanation offered is not supported by the observed behaviour of the target in the computer model.

The whole of this thesis is my work unless specifically indicated to the contrary in the text, and has not been submitted in part or in whole to any other University. Some thirty years ago the author operated a deep sounding machine, one of the first in the country, on a misty lake in Ireland and marvelled at the way subsoil information could be garnered. The magic of the moment never entirely passed and when the opportunity arose to use the technique in Natal the die was cast. The development of the national road system surged in the early 1970's and since many of these roads on the Natal coastal routes crossed extensive recent alluvial deposits, the geotechnical problems of instability and settlement became major factors in the road design. Traditional methods of investigation consisted of boreholes with sampling and laboratory testing. Whilst these were satisfactory, provided they were of adequate quality, they were relatively expensive if sufficiently detailed models of the subsoil were to be obtained for design purposes. Cone penetration testing provided a potential a solution and this led to research work conducted over a period of twenty five years which continues today. The initial development of ideas for improvements to the mechanical equipment took place whilst the author was carrying out preliminary investigations for freeway routes over the coastal alluvial deposits. This was followed by a period devoted largely to cone penetration testing research and deVelopment and to embankment design methods at the National Institute for Transport and Road Research, and to the initial registration for a Master's degree under the supervision of Professor K Knight in 1975. This research programme was completed as originally envisaged, but not submitted because during its course the author conceived the idea of the piezometer cone. This proved to be such an exciting prospect that the research and development continued for a number of years until piezometer cone testing has now become almost routine for geotechnical investigations on alluvial deposits. In 1983, due to Professor Knight's retirement from the University, Mr Phillip Everitt was appointed as the supervisor. At that stage piezometer testing was becoming accepted internationally and new aspects and information frequently appeared. It was apparent, however, that the essential proof of the system for the prediction of embankment performance was to use it at embankments where the performance had been monitored. Eventually grants were provided by the Department of Transport for this, which enabled two research projects to be conducted during 1989 - 1990 and 1991 - 1992. After completion of the first of these a presentation of the author's work on cone penetration testing since the mid 1960's was made to the Faculty of Engineering at the University of Natal. The Executive Committee of the University Senate subsequently approved, in August 1991, that the registration be upgraded to doctoral status. Mr Everitt's encouragement during this extended period has been a vital factor in ensuring an outcome for this task and the author wishes to express his gratitude for this. / Thesis (Ph.D.)-University of Natal, Durban, 1992.

Many embankments on the soft, highly variable, recent alluvial deposits along the South African coast have suffered large settlements necessitating ongoing costly repairs. Due to the soft variable soils, borehole sampling is difficult and laboratory testing requires to be extensive for adequate subsoil modelling; cone penetration testing was considered to be a potential means to overcome these problems. Twenty five years ago in South Africa, as elsewhere, cone penetration testing equipment was relatively crude and the methods of interpretation were simplistic. The application of cone penetration testing to recent alluvial deposits therefore required improvements to both the equipment and the derivation of soil parameters. The equipment was upgraded by introducing strain gauge load cells capable of measuring cone pressures in soft clays with adequate accuracy. Hence, correlations of cone pressures with compressibility and shear strength became possible. Predictions of settlement times and magnitudes are of equal importance and a consolidometer-cone system was developed to assess both of these. A piezometer was incorporated into a cone to ascertain whether the settlements were due to consolidation. The piezometer cone performed so well that it superseded the consolidometer-cone and by 1977 a field piezometer cone was in regular use. Developments in piezocone interpretation have taken place concurrently with those in equipment; coefficients of consolidation are evaluated from pore pressure dissipations, and soils identified from the ratio of pore and cone pressures. These developments have been validated in two recent research projects, by comparing measured and predicted settlements at eleven embankments monitored for up to fifteen years. The data shows that for embankments on the recent alluvial deposits the constrained modulus coefficient, am is : am = 2,6 ± 0,6 The data also shows that coefficients of consolidation from piezometer cone dissipation tests are correlated with those from laboratory tests and back analysed embankment performance as follows : Embankment c = 3 CPTU c = 6 Lab cv It is concluded that piezometer cone penetration testing is particularly suitable for the geotechnical investigation and the subsequent design of embankments on recent alluvial deposits and should be considered as complementary to boreholes with sampling and laboratory testing. The existing database of embankment performance should be expanded with particular emphasis on long term measurements and on thorough initial determination of basic soil parameters / Thesis (Ph.D.)-University of Natal, Durban, 1992.

Acyclovir is an antiviral drug used in the treatment and prevention of herpes simplex and varicella-zoster viral infections. The major problem in the transdermal delivery of acyclovir is the permeation in sufficient amounts to deeper layers of the skin and into the systemic circulation. Acyclovir is a hydrophilic substance with a low partition coefficient, resulting in poor penetration through the excellent barrier of the skin, the stratum corneum. In an attempt to enhance the transdermal permeability of acyclovir, the aim of this study was to employ terpenes as possible penetration enhancers. Terpenes are constituents of natural essential oils, with widespread medicinal use including in aromatherapy. The terpenes used in this study were 1,8-cineole, limonene, menthol, menthone, and 13- myrcene. Terpenes are not only used as penetration enhancers, but are even more often present in drugs and cosmetics. Limited studies have been done concerning the penetration of terpenes through the skin. Thus, not only the effect of the terpenes on the penetration of acyclovir, but also the penetration of the terpenes themselves were studied. The influence of acyclovir on the penetration of the terpenes was also determined. In vitro permeation experiments were performed on human skin using Franz diffusion cells. The skin was pretreated with a 5 % solution of the terpene in ethanol and left for 30 minutes to enable ethanol evaporation and terpene incorporation into the skin. Saturated aqueous solutions of acyclovir (pH 7.4) were added in the donor compartment before and after skin pre-treatment. The acyclovir concentration retrieved from the receptor compartment of the Franz cells was analyzed by HPLC. The amount of terpene that penetrated were semi-quantitatively determined by GC. Penetration of acyclovir was significantly enhanced by two terpenes, viz. 1,8-cineole and menthol. The extent of enhancement was, however, not large enough to be of clinical use. The enhancement in acyclovir penetration observed upon ethanol pre-treatment alone, or in the presence of limonene, menthone or ~-myrcene, was not significant. Penetration enhancement of acyclovir by the terpenes was in accordance with previous studies, which postulated better enhancement of hydrophilic drugs by hydrophilic terpenes. Large percentages of the terpenes with log P values within the optimum log P range (1 - 3) penetrated, as was found with menthone and menthol. Penetration decreased accordingly as the log P, and thus lipophilicity, increased. Stratum corneum retention is regarded as the most plausible explanation for this phenomenon. In the case of 1,8- cineole, enhancer pooling in the stratum corneum could be a possible reason for its poor penetration. Acyclovir significantly influenced the penetration profiles of some of the terpenes, but no clear explanation could be given. / Thesis (M.Sc. (Pharm.))--North-West University, Potchefstroom Campus, 2004.

An experimental research program was designed to study laminar flows through and over models of porous media with or without inertial effects. The models used were made up of circular or square rods arranged to cover solid volume fraction ϕ ranging from 0.03 to 0.49, and filling fraction h / H ranging from 0.34 to 1 of the test channel. In this way, the ratios of the depth of the test section to the porous medium pore H / l ranged from 5.75 to 18.25. Three types of model porous media were tested: (1) two-dimensional ‘horizontal’ models, having rod axes aligned along the span of the channel in a staggered or non-staggered fashion; (2) three-dimensional ‘vertical’ models with rod axes aligned in the transverse direction; and (3) three-dimensional ‘mesh’ models with rod axes aligned along both transverse and spanwise directions. Using a pressure-driven viscous fluid, the bulk Reynolds number Rebulk was varied from 0.1 to 10.3. Velocity measurements were obtained using particle image velocimetry at various streamwise-transverse planes of the test section. Differential pressure measurements were also obtained using electronic transducers. These measurements were used to determine relevant governing equations for the flow through the porous media; to characterize the effects of ϕ rod shape and arrangement, h / H, H / l, porous media dimensionality, and Rebulk on the flow; and to predict the flow at the porous medium-free flow interface. The Izbash and quadratic Forchheimer equations were respectively found to describe well the flow through two- and three-dimensional porous media. Penetration of the free flow into the porous medium varied with ϕ and rod arrangement, but was nearly independent of the rod shape. At the interface between the porous medium and the free flow, h / H and H / l effects were found to be counteractive. Penetration was highest for the vertical models compared with the mesh and horizontal models. Inertial dependence of interfacial flow was weak when porous medium conditions were considered. The interfacial flow was found to follow a dose response formulation with a predictable slip coefficient.

No description available.

The production of gelatine at Gelita N.Z. Ltd. is a time consuming process. The time limiting step in the process is the pre-treatment of the collagen tissue of the raw material in a lime/sodium sulfide solution. The liming solution breaks down the collagen in the tissue to gelatine. This is a necessary step prior to the extraction of gelatine from the hide pieces. The current liming process takes nearly 50 days to complete. Methods were investigated to increase the rate of penetration of the chemicals into the bovine hide raw material. An increase in the penetration of the liming solutions would lead to shorter processing times for this step in the process. The methods that were investigated were temperature controlled mixing, fluidization of the hide pieces and the use of ultrasound. Of all the methods tested, the fluidization of the hide pieces gave the best results. The pretreatment time of the hide pieces was reduced 9 days with this technique. Methods were also investigated to monitor the levels of conditioning in the raw material An accurate technique to measure hide conditioning was important to pilot plant trials. This helped determine how well any of the trail methods increased the penetration of chemicals into the hide pieces. The use of an ultraviolet dye proved an effective method of measuring conditioning for all the pilot plant trials. The level of chemical penetration was monitored by assessing the penetration of the UV dye. The penetration of the UV dye could be quantified by using imaging software. A possible method of monitoring conditioning in full-scale production was tested. It was determined that the glycosaminoglycans and soluble collagen released into the liming solution could be accurately measured, and related to the overall conditioning of the raw material.