published_or_final_version / Civil Engineering / Master / Master of Philosophy

The objective of this research was to further understand the behavior of the soil under the action of a tillage tool, with the purpose of finding a relation between the tool geometry and the resultant soil seed bed. Thus the problem consisted of understanding the mechanics of producing soil break up and to find a logical method of analyzing it. / The problem was solved using fundamental principles of soil mechanics and force equilibrium analyzis. As a result, a mathematical model was developed which describes three failure zones within the cut soil volume. The model can be programmed into a computer to generate maps of normal and shear stresses to visualize the three failure zones. / The failure zones are the shear failure zone, the tensile fracturing zone and the no failure zone. The tensile fracturing zone is delimited by the tensile stress reaching the tensile strength of the soil at the given soil moisture content and soil density. The tensile strength of the soil was measured using an apparatus and method designed in this research. / The mathematical model gives an explanation of the mechanics of crumbling and the shape of the failed volume, but it does not give information concerning soil aggregate quality and arrangement within the soil furrow. Then, a method of analyzing the formed aggregates was developed which considers some soil physical properties of aggregates. / The study concluded that the smaller tool width and the smaller tool rake angle, among the ones used in this research, produced the most efficient geometry in producing the largest amount of soil break up, the most uniform aggregate formation and the most stable aggregate arrangement. The same tool geometry requires less energy per unit volume of soil disturbed. The best performance is produced at the lowest soil water content among those tested.

A number of methods have been proposed that utilize the time domain transformations of the frequency dependent impedance functions to perform time-history analysis of structures accounting for soil-structure interaction (SSI). Though these methods have been available in literature for a number of years, this study is the first to rigorously examine the limitations and advantages of these methods in comparison to one another. These methods contain certain stability issues that required investigating which lead to the formation of an analysis procedure that assesses a transform method’s stability. The general applicability of these methods was demonstrated by utilizing them to model increasingly sophisticated reference problems. Additionally the suitability of these methods to being incorporated into hybrid simulations of nonlinear inelastic structures considering soil-structure interaction was confirmed. The modelling of a nonlinear structure considering soil-structure interaction is an improvement over the most common modelling strategies that model solely linear-elastic behaviour.

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The design of service connections to deeply buried sewers involves a number of challenges. In practice, the loads that develop from vertical risers can damage the Tee or Wye fitting to which it is connected. This thesis studies the expected loads and resistance of these connections, and provides some recommendations for the solution of this engineering problem. Laboratory tests have been performed to explore the capacities of the existing fittings both in air and when buried in uniform sand. A test procedure different from the standard quality control test methods described in ASTM F1336-02 is used to study the performance of the fittings in air. A special test configuration was also developed for an existing pipe test cell to explore the capacities of the existing PVC Tee and Wye fittings when buried in uniform sand. An analytical formula analogous to pile downdrag and numerical analyses have been used to evaluate the test results, to calculate the capacities of the buried heavy-wall fittings, and to explore the downdrag forces that develop along vertical risers. Through comparisons with experimental measurements, it was demonstrated that these methods of analysis can be used to estimate the downdrag forces and determine the adequacy of specific fittings to resist those forces. The major conclusions drawn for the specific fittings tested in this project are summarized as follows. When axially loaded in air, both Tee and Wye fittings experience plastic yield failure. When buried, the Tee fitting fractures or yields only along the base of the riser part; while the Wye fitting itself does not fail, the riser cracks near its base where it connects to the curved pipe (450 elbow) above the Wye. Both the capacities and stiffness of the buried fitting system (either Tee or Wye) are approximately linear functions of the confining stress supplied by the surrounding soil. The accumulated downdrag along the riser in the coarse-grained soil is much smaller than that in fine-grained soil. Various practical solutions for the vertical riser problem are then discussed and recommended. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2008-12-28 21:18:30.363

A field tillage tool carrier was constructed using a tractor trailer, hydraulic cylinder and steel construction material. Tillage tool blades of varying lengths, widths and angles of attack were fabricated from steel and were used in the study of the effect of tool rake angle, tool width and depth of operation on soil strength properties, draft, draft efficiency, volume of soil manipulated, degree of soil loosening and penetration resistance. / The results showed that the draft increased with tool rake angle and width. Operating at a depth of 150 mm and 100 mm depth did not make any significant difference on the draft requirement. Low angles of attack were observed to have a greater potential to loosen the soil, and the loosening increased to a depth of 150 mm then decreased. The draft efficiency was affected by the angle of attack as well as the depth of operation. The cross sectional area of the furrow and hence the volume of soil manipulated was seen to depend on the width of the tool and the operating depth. / Slender tools and high rake angles were found to loosen the soil better than wide ones. No distinct trend existed between depth to width aspect ratio and draft requirement. No variation was observed between draft efficiency and d/w ratio. Penetration resistance increased with depth of operation as well as distance from the furrow centre after tillage. Some areas of residual high strength were sometimes left within the sphere of influence of the tools. Some tools dealt with these omissions better than others.

A number of methods have been proposed that utilize the time domain transformations of the frequency dependent impedance functions to perform time-history analysis of structures accounting for soil-structure interaction (SSI). Though these methods have been available in literature for a number of years, this study is the first to rigorously examine the limitations and advantages of these methods in comparison to one another. These methods contain certain stability issues that required investigating which lead to the formation of an analysis procedure that assesses a transform method’s stability. The general applicability of these methods was demonstrated by utilizing them to model increasingly sophisticated reference problems. Additionally the suitability of these methods to being incorporated into hybrid simulations of nonlinear inelastic structures considering soil-structure interaction was confirmed. The modelling of a nonlinear structure considering soil-structure interaction is an improvement over the most common modelling strategies that model solely linear-elastic behaviour.

The physical state of the seedbed is of importance to the plant environment as it influences some important processes in the soil such as seedling emergence, water and solute transport, and ease of root penetration. This is affected to a large extent by tillage process, the tillage implement type and the geometry of the implement used. / A field experiment was carried out on a clay soil to determine the effect of the geometry of bladed tillage implements on some soil physical properties after tillage. The soil properties evaluated were bulk density, mean clod size distribution and total pore space after tillage and the extent of loosening achieved. / Implement parameters considered were blade width, rake angle and depth of operation of the implement. Two blade widths of 75 and 150 mm were evaluated in combination with three rake angles of 30, 60 and 90 degrees. Each tillage implement was drawn through the soil at four operating depths of 100, 150, 200 and 250 mm. / Larger rake angles were observed to result in larger mean aggregate sizes and greater bulk density reductions when compared to smaller rake angles. Greater reduction in bulk density was observed with the wider of the two blade widths evaluated. Mean clod size after tillage was also observed to be large for the wider of the two widths evaluated. Irrespective of width and rake angle, greater operating depths resulted in larger mean clod sizes and greater reductions in bulk density as compared to shallower operating depths. Fractal analysis showed the extent of fragmentation to be greater at shallower operating depths, hence the small mean clod sizes obtained.

Minimization of Construction Costs of Substation Grounding Grids: In every electrical installation, one of the most important aspects is adequate grounding; in particular, the grounding of high-voltage substations to protect people and equipment in the event of an electrical fault. Well-designed grounding systems ensure the performance of power systems and safety of personnel. It is desirable that the substation grounding provides a near zero resistance to remote earth. The prevailing practice of most utilities is to install a grid of horizontal ground electrodes (buried bare copper conductors) supplemented by a number of vertical ground rods connected to the grid, and by a number of equipment grounding mats and interconnecting cables. The grounding grid provides a common ground for the electrical equipment and for all metallic structures at the station. It also limits the surface potential gradient. Currently the IEEE 80-2000 standard for substations grounding limits the determination of the grounding parameters (namely step, touch and ground potential rise) to that of a uniform soil model unless the Sunde graphical method is used. With the Sunde graphical method, it relies on interpretation to obtain a two layer soil model. Without the use of the graphical method, the IEEE 81-1983 has several empirical equations that can be used for the two layer model; however, these equations rely on the use of images which retard the speed of calculations to the point where the overall optimization of the grounding grid (with respect to size and shape) has yet to be determined. The goal of the thesis was to improve upon the current restrictions for the grounding grid design, while minimizing the material (i.e., copper conductors) and installation costs of a grid. The first part of the research examined previous work through a combination of literature review, mathematical computations, and field measurements to validate the theoretical aspects of grid design. The thesis introduces an optimized uniform and two-layer soil with fast accurate calculations directly from soil measurements without the use of graphical methods or the use of complex image theory. Next, the thesis develops enhanced grounding parameter equations using Simpson’s Rule of integration. The final part of the thesis demonstrates how it is possible to optimize the configuration of the grounding grid itself, minimizing costs, and yet still achieving a safe installation. This is the first time such an optimization is possible, and it is made possible by the techniques developed in this thesis. The techniques are applied to existing real-world grid designs, and the results obtained show the effectiveness of the method in reducing construction costs. This thesis shows how these construction and material savings are realized by utilizing a process whereby the grounding design minimizes the overall cost. The overall contribution of this thesis is the optimization of the grounding grid design by eliminating the current restrictions found in the IEEE standards 80 and 81, respectively, and offering an optimized grounding system design, starting from the soil model to the actual grounding design itself.

Persistent soil compaction by heavy-axle-load vehicles is a growing concern for the long-term productivity of clay soils. For optimum soil management, however, we must be able to evaluate adequately soil structural damages. This study compares different methods of assessing soil structure as affected by compaction and subsoiling treatments in a clay soil under corn production. / The tests used were: total porosity as calculated from densimeter readings and from soil cores; structural porosity; water desorption characteristics; and soil profile examination. These tests were performed in three layers of 20 cm and evaluation was based on their practicality and their ability to differentiate between treatments and to correlate with corn yield. / The results confirm that total porosity is a poor indicator of compaction in the subsoil. In soil profile assessments, ped descriptions were preferable to examination of pores. Water content and saturation deficit at $-$4.0 and $-$100 kPa were the best indicators of treatments and plant response.