<p> The base and shaft resistance of steel pipe piles installed in silica sand is affected by several factors; these include but are not limited to: shaft resistance degradation, shaft surface roughness, installation method, pile geometry, soil density and particle size, and setup.  This thesis focuses on the first four factors, while also considering the effect of soil density within each factor. Several of the pile design formulas available do not consider the effects of shaft resistance degradation due to load cycles during installation of jacked and driven closed-ended pipe piles, plug formation and evolution during driving of open-ended pipe piles, the degree of corrosion or pitting corrosion on the shaft surface of a pile and its potential impact on setup, and the geometry of the tip of the pile. To assess the impact on pile capacity of some of these factors, a series of static compression load tests were performed in a controlled environment in a calibration chamber with a scaled down instrumented model pile. The air-pluviation technique with different combination of sieves assembled in a large-scale pluviator was used to prepare F-55 sand samples of different density in the calibration chamber. Slight changes were made to the experimental setup to study each factor: sand sample density, driving energy, mode of installation, and geometry and shaft roughness of the model pile.</p> <p><br></p> <p>The results from the experiments confirmed that each of these factors affects the pile resistance. Some of the important conclusions were:</p> <p><br></p> <p>i. The shaft resistance of the model pile is about 2.4 times greater for jacked piles than for driven piles in dense sand, due to the greater shaft resistance degradation in driven piles. </p> <p>ii. Despite the effect of degradation, the shaft resistance of the non-displacement model pile which had no loading cycles was a ratio of 0.37 to that of the driven model pile in medium dense sand and 0.60 in dense sand, due to the absence of displacement.</p> <p>iii. An increase in the surface roughness of the jacked model piles from smooth to medium-rough resulted in an increase of the shaft resistance, which had a ratio of 7.75 to the smooth pile in dense sand and 3.05 in medium dense sand. An increase from smooth to rough resulted in an increase of the shaft resistance, which had a ratio of 8.00 to the smooth pile in dense sand and 4.26 in medium dense sand.</p> <p>iv. Although rougher interfaces produce greater interface friction angles than smooth interfaces with sand, once a limiting value of surface roughness is reached, shearing occurs in a narrow band in the sand in the immediate vicinity of the model pile, with the shaft resistance depending on the critical-state friction angle of the sand. This means the shaft resistance will not increase further with changes in pile surface roughness, due to the fact that the internal critical-state friction angle of the sand has been reached in the shear band during loading.  </p> <p>v. During installation, the conical-based pile had a higher penetration per blow compared to the flat based pile from 0 to 25.6<em>B</em> in medium dense sand and 0 to 20<em>B</em> in dense sand (<em>B</em> = base diameter). After the pile was installed beyond 25.6<em>B</em> in medium dense and 20<em>B</em> in dense sand, the penetration per blow was identical. </p> <p>vi. The base resistance of a conical-based model pile was about 0.76 times that of a flat-based model pile in dense sand and 0.56 in medium dense sand. </p> <p>vii. Jacked piles had similar base resistance ratio of about 0.93 to 0.95 of driven piles in dense sand and 0.98 to 1.05 in medium dense sand. However, they had a much higher shaft resistance ratio of about 1.67 to 2.07 in dense sand and 1.44 to 1.50 in medium dense sand. </p>

<p>  </p> <p>Knowledge of the displacement and deformation fields beneath foundation elements obtained from carefully executed experiments is required to validate state-of-the-art numerical simulations, which in turn enable the development of better foundation design methods. This dissertation presents the results of an experimental program in which load tests were performed on model footings in a half-cylindrical calibration chamber with a transparent viewing window across its diameter. The digital image correlation (DIC) method was used to obtain the strain and displacement fields in the soil from digital images taken during the tests. Tests performed on both smooth and rough footings show a significant dependence of resistance on footing base roughness, with the DIC results providing insight into the reasons for that dependence. The experimental bearing capacity results are used to validate a previously proposed method in which an equivalent friction angle is used for calculation of the bearing capacity of footings in sand.</p> <p>Schmertmann's method is one of the traditional methods for estimating the settlement of axially loaded footings in sand using cone penetration test (CPT) data. The method was developed for footings placed on the surface of a single, uniform sand layer; it assumes a depth of influence below the footing base within which most of the soil deformations take place and an influence diagram to quantify the influence factor as a function of depth. However, the literature contains limited information on the strain influence diagrams for footings on layered sands, and, as a result, there is no way to accurately account for the effect of sand layering on footing settlement. In this study, Schmertmann's approach for calculating the strain influence factor is modified to account for the effect of two sand layers with varying thickness and relative density. Penetration experiments were performed using a half-square model footing (width <em>B</em> = 90 mm) placed on the surface of both single and two-layered (dense over medium-dense and medium-dense over dense), air-pluviated, silica sand samples prepared inside a half-cylindrical calibration chamber designed for digital image correlation (DIC) analysis. The test results indicate that both the thickness and relative density of the top sand layer (the layer in contact with the footing base) affect the parameters of the strain influence diagram. For dense sand over medium-dense sand, the depth to the peak strain influence factor varies with the thickness of the dense layer; however, when the thickness of the dense layer is 1.5<em>B</em> or greater, the strain influence diagram is similar to that obtained for a single, uniform sand layer. In contrast, for medium-dense sand over dense sand, the peak value of the strain influence factor varies with the thickness of the medium-dense layer up to a value of 1<em>B</em>. Based on the results obtained in this study, new strain influence diagrams are proposed for settlement calculation of square footings on two-layered sand profiles. The proposed method for estimation of footing settlement in layered sand is validated against measured data obtained from a full-scale, instrumented footing load test reported in the literature. </p> <p>The expressions for the shape and depth factors available in the literature for bearing capacity calculation are mostly empirical and are based on results obtained using limit analysis or the method of characteristics assuming a soil that is perfectly plastic following an associated flow rule. This study presents the results of an experimental program in which load tests were performed on model strip and square footings in silica sand prepared inside a half-cylindrical calibration chamber with a transparent visualization window. The results obtained from the model footing load tests show a significant dependence of footing penetration resistance on embedment depth. The load test results were subsequently used to determine experimentally the shape and depth factors for model strip and square footings in sand. To obtain the displacement and strain fields in the sand domain, the digital image correlation (DIC) technique was used to analyze the digital images collected at different stages during loading of the model footing. The DIC results provide insights into the magnitude and extent of the vertical and horizontal displacement and maximum shear strain contours below and around the footing base during penetration.</p> <p>The loading of a footing in sand generates substantial shear bands as a mechanism for failure develops with the formation of slip surfaces. The interaction of sand particles in the shear band governs its constitutive response to loading. This study provides the results of loading experiments performed under different conditions on half-square model footings (width <em>B</em> = 90 mm) in dense air-pluviated silica sand samples prepared in a half-cylindrical calibration chamber equipped with an observation window that allows collection of images of the sand domain during testing. Two sands (Ottawa sand and Ohio Gold Frac sand) with different roundness (angularity) were used to perform these experiments. The digital image correlation (DIC) technique was used to obtain the incremental strain fields in the sand domain. The zero-extension line (ZEL) concept was then used to study the shear strain localization process and to obtain the orientation of the shear bands from analysis of the incremental strain fields. The results show that sand particle morphology, footing surface roughness, load eccentricity, and depth of embedment of the model footing have an impact on the dominant shear band patterns that develop below the model footings, and, as a result, all of these factors affect the unit bearing capacity of footings. The estimated thickness <em>t</em>s of the shear band from the experiments is approximately 6<em>D</em>50 for Ottawa sand and approximately 8<em>D</em>50 for Ohio Gold Frac sand. </p>

Two-phase flow in porous media is an important subsurface process that has significant impacts on the global economy and environments. To study two-phase system in porous media, capillary pressure (Pc ), relative permeability (Kr), bulk electrical conductivity (σb) and bulk relative permittivity (εb) are often employed as characterization parameters. Interestingly, all of these parameters are functions of water saturation (S). However, the non-uniqueness in the Pc -S, Kr-S,σb-S and εb-S relationships pose considerable challenges in employing them for effective monitoring and control of the two-phase flow processes. In this work, laboratory scale experiments and numerical simulations were conducted to investigate the factors and conditions contributing to the non-uniqueness in the above relationships for silicone oil-water and supercritical CO2-water flow in porous media, with a special emphasis on geological carbon sequestration. Specifically, the dynamic capillary pressure effect, which indicates the dependence of the Pc - S relationship on the rate of change of saturation (αS/αt) during two-phase flow in porous media was investigated. Using a silicone oil-water system, the dynamic capillary pressure effect was quantified in term of the parameter named the dynamic coefficient, τ , and it was found to be dependent on the domain scale and the viscosity ratio of the two fluids. It was found that τ increases with the domain scale and the viscosity ratio. It is inversely affected by αS αt , which is related to the degree of resistance to the fluid motion, namely, viscosity. In almost all cases, τ was found to decrease monotonically with an increase in water saturation, S. An order increase in magnitude of τ was observed as the domain scale increases from 4cm scale to 8cm in height. A similar order of increase in τ was observed in the 12cm high domain scale. There is an order increase in the value of τ for the silicone oilwater system as the viscosity ratio increases from 200 to 500. For the supercritical CO2 (scCO2) and water system in porous media, the experiments and numerical simulations showed that τ increases with rising system temperature and decreasing porous media permeability. Dimensionless analysis of the silicone oil-water experimental results showed that by constructing non-dimensional groups of quantities expressing a relationship among different variables on which τ depends, it is possible to summarise the experimental results and determine their functional relationship. A generalised scaling relationship for τ was derived from the dimensionless analysis which was then validated against independent literature data. The exercise showed that the τ-S relationship obtained from the literature and the ii scaling relationship match reasonably well. This work also demonstrated the applicability of an artificial neural network (ANN) as an alternative computational platform for the prediction of the domain scale dependence of τ . The dependence of the Kr-S relationship on αS/αt was also investigated. The results showed that the Kr-S curve under dynamic flow condition is different from that under the quasi-static condition. Kr for water (Krw) increases with increasing water saturation and decreases with the increase in viscosity ratio while Kr for silicone oil (Krnw) increases with decreasing water saturation as well as with the increase in viscosity ratio. Also, Krw decreases while Krnw increases with the increasing boundary pressure. However, the εb-S and σb-S relationships were found to be independent of αS/αt for the scCO2-water system in carbonate and silicate porous media. Nevertheless, the εb and σb values decrease as the water saturation decreases in the two porous media samples. While εb decreases with increase in temperature in silica sand, the trend in the limestone showed a slight increase with temperature, especially at high water saturation. Also, the εb-S relationship is shown to be affected by pressure in silica sand increasing with the pressure of the domain. On the contrary, the σb-S relationship increases as the temperature increases with more significance at higher water saturation in the silica sand sample. This work further demonstrated the application of a membrane in the monitoring of the CO2 in geological sites used for carbon sequestration. Commercial silicone rubber coupled with a pressure transducer showed potential in the detection of CO2 leakage from geological sites. The response of the device in terms of the mass of permeated gas, permeability and gas flux were investigated for both CO2 and N2. In addition, the monitoring of potable water contamination in a shallow aquifer by the migrating or leaking of CO2 is demonstrated with the combination of the pH analysis, geoelectrical measurement techniques and the membrane-sensor system. Overall, the work in this PhD research demonstrated robust applications of two-phase systems'characterization parameters under different scenarios in the porous media. Implications of the findings in this work to the monitoring and control of two-phase systems in porous media are expatiated.

Autoclaved aerated concrete is a used building material, especially for its thermal insulating properties. During autoclaving, an aerated concrete microstructure produces crystalline CSH phases, primarily tobermorite. The ingoing substances are calcium oxide and silica. In addition to commonly used raw materials, secondary raw materials rich in silicon dioxide can be used for production. The use of secondary raw materials gives the opportunity for the construction industry to be more environmentally friendly. Another benefit is the reduction of financial costs. The work explores the influence of individual secondary raw materials on the microstructure. High-temperature fly ash, fluid fly ash, cinder, ground glass and zeolite were used The raw materials were mixed with unalloyed lime at a molar ratio of calcium oxide to silicon dioxide of 0.73 and 1.0. Autoclaving capsules were used to synthesize tobermorite under laboratory conditions. Autoclave was performed at 170 °C and 190 °C with hydrothermal durations of 4, 8 and 16 hours. The most important influence on the microstructure was high-temperature fly ash, on the contrary, the greatest influence on the mechanical properties is attributed to the ground glass.