The characterization of unsaturated soil behaviour from penetrometer performance and the critical state concept

PhD ThesisThe proportions of the Critical State surfaces of a given soil depend on its stress and moisture history, its current moisture status and soil type. The influence of these factors on the geometry of the state surfaces, and their bearing on the mechanical behaviour of the soil itself, cannot be readily perceived because of the very large number of interacting effects present in the model. The use of sophisticated computer graphics for the three-dimensional visualization of critical state surfaces would therefore provide a ready means for obtaining an insight into the complex changes taking place in critical state space. The initial part of the thesis deals with the formulation of mathematical models and computer software for integrating numerical computations, data reduction and visualization techniques for analysing critical state surfaces. The programmes developed were used for interpreting the influence of moisture status on the key behavioural patterns of three different British Soils. Systematic changes to state space due to the combined influence of moisture content variations and soil type were readily traced. It is well known that collating data for the above analysis is difficult and requires advanced measuring techniques. An attempt was therefore made to establish a connection between the data obtained from a simple field measuring device, such as a cone penetrometer, with the volume-change behaviour of soil, as modelled by its critical state surfaces. This is attempted in two stages. The first stage presented in the thesis assumes the soil to be a rigid-plastic Mohr-Coulomb material and deals with the formulation of a mathematical model to predict cone index as a function of cone geometry, penetration depth, c, cp and soil-to-metal parameters cQ and S. This model is based on the extension of the basic two-dimensional Sokolovski solution to the three-dimensional slip-line field developed during the deep penetration phase of a cone. Shallow penetration depths, at which the standard Sokolovski rupture surface interacts with the soil surface, cannot be dealt with by this approach. The second stage of the investigation attempts to connect cone index with the stress (p, q) and pore space (v) parameters of the soil on the cone surface. The model developed in the thesis is based on identifying a state parameter yr (defined by Been and Jefferies for dry sands). This establishes the position, within critical state space, of the cone surface stress and pore space parameter (p, q and v) relative to the critical state wall. The state parameter yr is then associated with soil type and moisture 2 content by a two-parameter linear function. Once these two parameters are found experimentally, cone index can be readily translated into pore-space estimates. The thesis presents the mathematical analysis which provides the basis for this correlation. The thesis describes the experimental investigations carried out to verify the performance of the theoretical models developed. The validation of the state parameter concept required the design and development of a special calibration chamber which could apply controlled boundary stresses to a cylindrical soil sample into which the penetrometer is advanced. Ideally very large sample diameters are required to minimise boundary interference, but a compromise had to be made by using miniature penetrometers and a realistic sample diameter of 100 mm. The cone penetrometer performance model was tested under laboratory conditions in an indoor soil tank. Both these investigations required tedious back-up laboratory experimentation to establish the basic Mohr-Coulomb and critical state parameters of the test soil over a wide range of moisture contents. All the soils were dealt with in a remoulded state as consistently reproducible stress and moisture histories for this case can be easily maintained in each of the very large number of samples required in the experimental programmes. The experimental work shows very clearly that the state parameter concept is applicable to partly saturated c-Sp soils over a wide range of moisture contents and that it is possible to quantify the systematic changes in the state parameter y' with soil moisture content. The predictive performance of the cone penetrometer model, within the specified penetration range, was also good. Data reduction charts for interlinking these two models are presented and the use of these charts for the derivation of pore space particulars from cone index data predicted satisfactory trends. However, this procedure appears to over-predict dry bulk density by a considerable margin. The validation presented in this study is for a single sandy loam soil. Even though the overall predictive performance of the mathematical models in this particular soil is most encouraging, it should be borne in mind that the models developed are bound to be influenced by the drastic simplifications required to interlink two disparate models, one which ignores volume change with one which does not. Further work is required to remove any detrimental consequences of these compromises and to introduce confidence in extending the findings to other soil types.Commonwealth Scholarship Commissio

Wastewater treatment using coconut fibre ash as an adsorbent for removal of heavy metals

The study aimed at evaluating the performance of coconut fibre ash as an alternative low-cost adsorbent to the synthetic adsorbents used in wastewater treatment. This research aims to identify the optimum condition for the adsorption process, considering the effect of particle size, adsorbent dosage, and contact time of adsorbents of coconut fibre ash in removing lead (Pb), copper (Cu), and zinc (Zn) metal ions from electroplating wastewater. The adsorbents coconut fibre ash was prepared through activation of carbon at 450º C after following proper cleaning and drying process. The experiments were conducted at varying adsorbent dosages (0.2 g, 0.6 g, and 1 g), particle size (50 to 200 microns), and contact times (40 minutes, 80 minutes, and 120 minutes). The result shows that adsorbents show less efficiency in removing Zn metal ions, which is not more than 34% in the case of 1g adsorbent dosage, particle size ranges 100-200 microns, and 120 minute contact time. The maximum removal efficiency of 95.04% and 80% was obtained at the optimum amount (1g) of adsorbent dosage for Pb and Cu respectively. In the case of contact time, it was identified that the optimum condition for maximum removal efficiency is 120 minutes with a 1g adsorbent dosage both for Pb and Cu ions. To ensure maximum removal of metal avoiding any desorption of the metal ion from the adsorbent surface, it was identified that a maximum contact time of 120 minutes should be allowed for adsorption. However, it could be concluded that adsorbents of coconut fibre ash can be used in treating wastewater facilitating good adsorption capacity in removing heavy metals, low cost and availability

Identification of angiotensin I converting enzyme inhibitory and radical scavenging bioactive peptides from sea cucumber (Stichopus vastus) collagen hydrolysates through optimization

The sea cucumber (Stichopus vastus) is an underutilized species, as most of its parts, including the integument (high collagen content) are thrown away during processing. The aim of this study was to investigate the effects of different hydrolysis conditions (substrate to enzyme ratio (S/E), reaction temperature, and hydrolysis time) on the angiotensin I converting enzyme (ACE) inhibitory and radical scavenging (RSc) activities of the hydrolysates produced from trypsin hydrolysis of S. vastus collagen. Optimal conditions predicted by Box-Behnken Design modelling for producing ACE inhibitory and RSc hydrolysates were found to be S/E ratio (15), reaction temperature (55°C), and hydrolysis time (1 h). Under optimal conditions, ACE inhibitory and RSc activities were estimated to be as high as 67.8% and 77.9%, respectively. Besides, some novel bioactive peptides were identified through mass spectrometry analysis. These results indicate that S. vastus hydrolysates might be used as a functional ingredient in food and nutraceutical products

Hard cocoa butter replacers from mango seed fat and palm stearin

The blending effects of mango seed fat (MSF), extracted using supercritical fluid, and palm stearin (PS) to formulate hard cocoa butter replacers (CBRs), were investigated. The triglycerides (TG), thermal properties and solid fat content (SFC) of the formulated blends were determined using different chromatographic and thermal techniques. All the blends had three main TGs; namely, 1,3-dipalmitoyl-2-oleoylglycerol (POP) (8.6 to 17.7%), 1-palmitoyl-2-oleoyl-3-stearoyl-glycerol (POS) (12.6 to 19.6%), and 1,3-distearoyl-2-oleoyl-glycerol (SOS) (37.2 to 31.4%), with SOS being the major component. The melting peak temperatures gradually increased and shifted towards higher temperatures with PS. The crystallization onset temperatures increased, while the offset decreased with PS. The SFC did not drop to 0% at 37.5 °C, which was shifted to 0% at and above 40 °C for some blends. The studies revealed that CBRs could be prepared by blending MSF and PS, and they could be utilized by chocolate manufacturers in tropical countries

ACE Inhibitory and Antioxidant Activities of Collagen Hydrolysates from the Ribbon Jellyfish (Chrysaora sp.)

Za izdvajanje bioaktivnih peptida iz kompas meduze (Chrysaora sp.) izoliran je kolagen, te je hidroliziran s pomoću tri proteaze: tripsina, alkalaze i komercijalnog prozivoda Protamex. Izmjeren je i uspoređen učinak različito inhibiranih peptida na inhibiciju angiotenzin konvertirajućeg enzima (ACE), te je pomoću metoda FRAP i DPPH ispitana njihova antioksidativna aktivnost. Osim toga, ispitan je utjecaj trajanja hidrolize na bioaktivnost peptida, tj. na inhibiciju ACE i antioksidativnu aktivnost. Najveća je ukupna antioksidacijska aktivnost (FRAP) izmjerena u hidrolizatima dobivenim pomoću komercijalne proteaze Protamex (25-27 mM) nakon 7 sati hidrolize, te nakon 9 sati hidrolize pomoću tripsina (24-26 mM). Nasuprot tome, hidrolizati dobiveni pomoću tripsina imali su najveću sposobnost uklanjanja DPPH radikala (94 % nakon 1 sata i 92 % nakon 3 sata). Hidrolizati dobiveni pomoću tripsina imali su najbolju sposobnost inhibicije ACE (89 % nakon 3 sata). Pomoću dvojne masene spektrometrije određene su sekvencije peptida koje su imale najveću aktivnost, a rezultati pokazuju da su hidrolizati imali veći udjel hidrofobnih aminokiselina i jedinstvenih sekvencija aminokiselina, što vjerojatno pridonosi njihovoj biološkoj aktivnosti.Collagen isolated from the ribbon jellyfish (Chrysaora sp.) was hydrolysed using three different proteases (i.e. trypsin, alcalase and Protamex) to obtain bioactive peptides. Angiotensin-I-converting enzyme (ACE) inhibitory activity and antioxidant activities (i.e. ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity) of the peptides were measured and compared, and the effect of the duration of hydrolysis on the bioactivity (ACE inhibitory and antioxidant activities) of peptides was also evaluated. FRAP activity was the highest in Protamex-induced (25–27mM) and trypsin-induced hydrolysates (24–26 mM) at 7 and 9 h, respectively. Conversely, hydrolysates produced by trypsin for 1 and 3 h showed the highest DPPH radical scavenging activities (94 and 92 %, respectively). Trypsin-induced hydrolysates (at 3 h) also showed the highest ACE inhibitory activity (89 %). The peptide sequences with the highest activities were identified using tandem mass spectrometry, and the results show that the hydrolysates had a high content of hydrophobic amino acids as well as unique amino acid sequences, which likely contribute to their biological activities

Physicochemical and biochemical properties of pepsin-solubilized collagen isolated from the integument of Sea Cucumber (Stichopus vastus)

The integument (high collagen content) of sea cucumber Stichopus vastus is generally wasted after harvesting, whereas only its stomach and intestines are eaten in few Asian countries. Amino acid composition, thermal transition temperature (Tm), zeta potential, solubility, moisture absorption and retention capacities, proximate composition and morphology of pepsin-solubilized collagen (PSC) isolated from the integument of S. vastus were studied. Amino acid composition revealed that glycine was dominant in the isolated collagen. PSC was found to have an isoelectric pH of 4.67, good moisture absorption and retention capacity at higher humidity, a sharp effect of pH and NaCl concentration on solubility, and an inverse relationship between temperature and viscosity. PSC also showed the maximum Tm to be 37.3C, very high protein content and ultrastructural characteristics. Hence, the PSC has the potential to be used as a functional ingredient in food, cosmetics and nutraceutical products

Characterization of crystallization and melting profiles of blends of mango seed fat and palm oil mid-fraction as cocoa butter replacers using differential scanning calorimetry and pulse nuclear magnetic resonance

Mango seed fat (MSF) and palm oil mid-fraction (POMF) blends were stabilized prior to investigate crystalliza- tion and melting behavior, solid fat content (SFC) and triglyceride compositions. Ten blends at various ratios of MSF/POMF, 95/5 (blend 1), 90/10 (blend 2), 85/15 (blend 3), 80/20 (blend 4), 75/25 (blend 5), 70/30 (blend 6), 65/35 (blend 7), 60/40 (blend 8), 55/45 (blend 9), 50/50 (blend 10) were used in this study. Results showed that the major triglyceride ranges in all blends were from 11 to 38.8% 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), from 22.1 to 36.9% 1,3-distearoyl-2-oleoyl-glycerol (SOS), and from 15.4 to 16.2% 1-palmitoyl-3-stearoyl-2- oleoyl-glycerol (POS), respectively. The melting behavior indicated a single curve with only one maximum and one small shoulder for the blends of 3 to 6. The blends having 70, 75, 80, and 85% of MSF showed similar crystallization pattern with a single curve having one maximum peak heights at temperatures of 10.17, 10.58, 11.54, and 11.66 °C. The SFC of the blends no. 1 to 5 was found to be close to these SFC of commercial CB at 10 to 20 °C temperatures. A multiple regression equation was developed which showed strong correlations between triglycerides of blends 1 to 10 and their properties. The studies revealed that preparation of green quality cocoa butter replacers (CBRs) is possible using MSF and POMF

Biochemical and radical-scavenging properties of sea cucumber (Stichopus vastus) collagen hydrolysates

The molecular mass distribution, amino acid composition and radical-scavenging activity of collagen hydrolysates prepared from collagen isolated from the sea cucumber Stichopus vastus were investigated. b and a1 chains of the collagen were successfully hydrolysed by trypsin. The molecular mass distribution of the hydrolysates ranged from 5 to 25 kDa, and they were rich in glycine, alanine, glutamate, proline and hydroxyproline residues. The hydrolysates exhibited excellent radical-scavenging activity. These results indicate that collagen hydrolysates from S. vastus can be used as a functional ingredient in food and nutraceutical products