Thesis (M. Phil.)--University of Hong Kong, 1984.

Earthworms are well known for their casting and burrowing activities which improve soil structure and soil fertility. However, earthworm populations in temperate regions exhibit patchy distribution in space and time. This makes it difficult to predict how earthworm activities may influence paedogenesis and nutrient cycling processes at the ecosystem level. The main objective of this study was to determine the spatiotemporal dynamic of surface cast production of two earthworm species, Aporrectodea turgida and Lumbricus terrestris, on the row-interrow scale in a temperate soybean agroecosystem. Our observations demonstrated that casting activity was synchronous with plant growth. More casts were also found in the row intercepts compared to the interrow ones. Both the spatial and temporal variations are thought to be caused by the microclimate found under the plant canopy, verifying results from controlled laboratory studies that show casting activity to be controlled by soil temperature and moisture. These results suggest a possible mutualism between earthworm and plants in cultivated temperate soybean agroecosystems, but this remained to be confirmed.

Under intensive farming, soil structure degradation and soil erosion are primarily associated with losses of organic matter. Restoration of soil structure may depend on the amount and nature of the organic amendment added. The effect of the addition of humic and fibric materials, and beeswax, a naturally occurring source of long-chain aliphatics comparable to those present in humic materials, on microbial activity and the structural properties of a waterlogged silty clay low in organic carbon was investigated. The incorporation of the fibric material increased the microbial activity in proportion to the amount of material added, whereas the humic and beeswax materials had the opposite effect. All organic materials added increased the cohesion of aggregates due to non water-dispersible cements. The fibric material was predominantly composed of polysaccharides and large quantities were required to produce a positive effect. The humic material was mainly lipids and the effect was associated with the time of incubation rather than the amount of material added. Principal-component analysis showed that the humic material was more effective at stabilizing soil aggregates than the fibric material, although the fibric material had a greater effect on the resistance of aggregates to slaking forces. Further testing with beeswax showed that the clay-associated lipids increased by 3.5-4.0 times the resistance of soil aggregates to the slaking forces, whereas the effect of hydrophobic "free" lipids was transient and accessory by coating and embedding soil aggregates.

Bibliography: leaves 172-189 / xviii, 189 leaves : ill. (1 col.) ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, Waite Agricultural Research Institute, 1987

Bibliography: leaves 147-170. / x, 170 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Aims to determine the influence of sodicity on the nature and decomposition of organic matter; and the influence of organic matter and its components on the structural stability of sodic soils. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1998?

A problem endemic in the development of the built environment is poor communication between structural and geotechnical specialists. Through better communication and considering the structure and foundation as an integrated system, new opportunities may arise for achieving superior performance. This thesis investigates the seismic performance of the integrated system through the development of integrated structure-foundation models using the Ruaumoko structural analysis program. A detailed representation of the structural and foundation systems was created using Ruaumoko, providing insight into the response of a range of integrated structure-foundation systems during seismic loading. In developing both shallow and deep foundation models, some modifications were made to Ruaumoko elements in order to improve the foundation model, but generally existing element configurations were used to represent foundations. Multiple structural and foundation designs were developed using a range of approaches. Use of a range of shallow foundation design methods identified the significant impact that moment loading had on foundation performance. Partial uplift of footings was identified as detrimental to footing performance as it shifted the rotational axes, increasing moment loads and reducing effective footing area. Pinned connections between the structure and shallow footings eliminated these effects at the expense of significant redistribution of actions in the structure and increased displacements. Variation of soil conditions showed that softer soil was most likely to reduce demands on the structure at the expense of foundation non-linearity. Reduced stiffness and increased radiation damping characteristics of raft foundations compared to footing foundation systems reduced the demands on three storey structures for all soil conditions. Increased structural demands were identified for the ten storey structure as a result of the reduced impact of foundation characteristics on the response of the integrated system. The level of rotational restraint at the head of pile foundations had a considerable effect on the structure and the foundation, with free-head piles developing the largest pile displacements and actions. Reduced rotational stiffness caused a substantial change in the distribution of structural actions, while increasing rotational restraint moved the characteristics closer to the response of fixed base models. Softer soil conditions greatly increased non-linearity in the foundation soil without any definitive improvement in structural performance.

A problem endemic in the development of the built environment is poor communication between structural and geotechnical specialists. Through better communication and considering the structure and foundation as an integrated system, new opportunities may arise for achieving superior performance. This thesis investigates the seismic performance of the integrated system through the development of integrated structure-foundation models using the Ruaumoko structural analysis program. A detailed representation of the structural and foundation systems was created using Ruaumoko, providing insight into the response of a range of integrated structure-foundation systems during seismic loading. In developing both shallow and deep foundation models, some modifications were made to Ruaumoko elements in order to improve the foundation model, but generally existing element configurations were used to represent foundations. Multiple structural and foundation designs were developed using a range of approaches. Use of a range of shallow foundation design methods identified the significant impact that moment loading had on foundation performance. Partial uplift of footings was identified as detrimental to footing performance as it shifted the rotational axes, increasing moment loads and reducing effective footing area. Pinned connections between the structure and shallow footings eliminated these effects at the expense of significant redistribution of actions in the structure and increased displacements. Variation of soil conditions showed that softer soil was most likely to reduce demands on the structure at the expense of foundation non-linearity. Reduced stiffness and increased radiation damping characteristics of raft foundations compared to footing foundation systems reduced the demands on three storey structures for all soil conditions. Increased structural demands were identified for the ten storey structure as a result of the reduced impact of foundation characteristics on the response of the integrated system. The level of rotational restraint at the head of pile foundations had a considerable effect on the structure and the foundation, with free-head piles developing the largest pile displacements and actions. Reduced rotational stiffness caused a substantial change in the distribution of structural actions, while increasing rotational restraint moved the characteristics closer to the response of fixed base models. Softer soil conditions greatly increased non-linearity in the foundation soil without any definitive improvement in structural performance.

A problem endemic in the development of the built environment is poor communication between structural and geotechnical specialists. Through better communication and considering the structure and foundation as an integrated system, new opportunities may arise for achieving superior performance. This thesis investigates the seismic performance of the integrated system through the development of integrated structure-foundation models using the Ruaumoko structural analysis program. A detailed representation of the structural and foundation systems was created using Ruaumoko, providing insight into the response of a range of integrated structure-foundation systems during seismic loading. In developing both shallow and deep foundation models, some modifications were made to Ruaumoko elements in order to improve the foundation model, but generally existing element configurations were used to represent foundations. Multiple structural and foundation designs were developed using a range of approaches. Use of a range of shallow foundation design methods identified the significant impact that moment loading had on foundation performance. Partial uplift of footings was identified as detrimental to footing performance as it shifted the rotational axes, increasing moment loads and reducing effective footing area. Pinned connections between the structure and shallow footings eliminated these effects at the expense of significant redistribution of actions in the structure and increased displacements. Variation of soil conditions showed that softer soil was most likely to reduce demands on the structure at the expense of foundation non-linearity. Reduced stiffness and increased radiation damping characteristics of raft foundations compared to footing foundation systems reduced the demands on three storey structures for all soil conditions. Increased structural demands were identified for the ten storey structure as a result of the reduced impact of foundation characteristics on the response of the integrated system. The level of rotational restraint at the head of pile foundations had a considerable effect on the structure and the foundation, with free-head piles developing the largest pile displacements and actions. Reduced rotational stiffness caused a substantial change in the distribution of structural actions, while increasing rotational restraint moved the characteristics closer to the response of fixed base models. Softer soil conditions greatly increased non-linearity in the foundation soil without any definitive improvement in structural performance.

Thesis (Ph. D.)--University of Adelaide, Dept of Soil Science, 1987. / Includes bibliographical references (leaves 207-222).

Thesis (Ph.D.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 156-164)