Includes bibliographical references. The beneficial effects of tillage are often negated in Australian soils by poor aggregate structural stability. If irrigation or rain falls on exposed freshly tilled soil, crusting or harsetting often develops on drying. Rainfall intensity, kinetic energy, rate of wetting, antecedent water content and soil management history have been implicated in aggregate breakdown.

Copies of author's previously published articles in pocket inside back cover. Bibliography: leaves 147-160. This thesis outlines the factors affecting soil strength and structural stability and their interrelationship in salt-affected soils. The objectives of this study are to investigate the influence of clay particles on soil densification and mellowing, the mellowing of compacted soils and soil aggregates as influenced by solution composition, the disaggregation of soils subjected to different sodicities and salinities and its relationship to soil strength and dispersible clay and the effect of organic matter and clay type on aggregation of salt-affected soils.

Bibliography: leaves 159-177.

Integral abutment bridges are jointless bridges in which the deck is continuous and connected monolithically with the abutment walls supported typically by a single row of piles. This thesis focuses on the effects of two major parameters on the seismic behavior of an integral abutment bridge in Tennessee by considering soil-structure interaction around the piles and in back of the abutments: (1) clay stiffness (medium vs. hard) around the piles, and (2) level of sand compaction (loose vs. dense) of the abutment wall backfilling. Modal and nonlinear time history analyses are performed on a three dimensional detailed bridge model using the commercial software SAP2000, which clearly show that (1) compacting the backfilling of the abutment wall will increase the bridge dominant longitudinal natural frequency considerably more than increasing the clay stiffness around the piles; (2) the maximum deflection and bending moment in the piles under seismic loading will happen at the pile-abutment interface; (3) under seismic loading, densely-compacted backfilling of the abutment wall is generally recommended since it will reduce the pile deflection, the abutment displacement, the moments in the steel girder, and particularly the pile moments; (4) under seismic loading, when the piles are located in firmer clay, although the pile deflection, the abutment displacement, and the maximum girder moment at the pier and the mid-span will decrease, the maximum pile moment and the maximum girder moment at the abutment will increase.

This thesis presents a study of the effects of deep excavations on adjacent metro or utility tunnel in soft to medium soil. The main objective of the thesis is to develop a method of estimating these effects quantitatively. Extensive review of relevant literature published in the past four decades was conducted in order to understand the trends and the key developments in this area. It was revealed from the literature review that the concurrent use of the Observational Method and the finite element method for monitoring and controlling of ground deformations around the excavation has become a norm for deep excavation projects. Several design charts and guidelines for estimation of effects of deep excavations on adjacent raft foundations or pile foundations were found in the literature; however, no such charts or guidelines were found for estimation of effects of deep excavations on existing circular tunnels. Consequently, the development of these guidelines was established as one of the objectives of this study. <p>The initial phase of the research was focused on detailed study and analysis of two well-documented case studies the Chicago Subway Renovation Project, USA and the Tan Tock Seng Hospital Deep Excavation, Singapore. The back analyses of these two case studies were carried out using the finite element software PLAXIS. Exact site conditions and input parameters for the soil and the structural components were incorporated as much as possible. Appropriate adjustments in some of the input parameters were necessary to achieve good match between the computed and the observed results. <p> The back analyses were followed by parametric studies to identify important variables controlling the mechanisms of soil-structure interaction. The variables identified from the parametric studies of the two case studies were: soil stiffness, tunnel lining thickness, the depth of the excavation, and the location of tunnel. These variables were used to conduct a series of finite element analyses using simplified geometry and ground conditions for the purpose of formulating preliminary design charts. Results from these analyses were recorded in terms of in-plane and out-of-plane distortion of tunnel lining as well as additional shear forces and bending moments induced in the tunnel lining due to an adjacent deep excavation. The results were made non-dimensional before presenting them as contour plots. These contour plots constitute preliminary design charts, which can be used for the estimation of tunnel lining deformation caused by adjacent deep excavation.<p> Based on the results of this study, it can be concluded that a finite element program (such as PLAXIS) that is able to model construction processes associated with tunnelling and deep excavation in urban environment can be an invaluable tool in exploring the mechanism of ground deformation around the deep excavation and in quantifying the effects of ground deformation on existing adjacent structures. The modeller must, however, be aware of the fact that ways of modelling a particular construction process could be different for various finite element programs. It is important to interpret the instructions given in the manual of the program correctly. <p>Detailed back analyses of well-documented deep excavation case histories are vital from the point-of-view of building confidence in the selected finite element program. Such analyses also have the potential to identify key variables influencing the soil-structure interaction. <p> Preliminary design charts proposed in this thesis are very convenient for obtaining approximate values of tunnel lining deformation caused by adjacent deep excavation. Non-dimensional nature of these design charts makes it possible to be used for any depth of the deep excavation and for tunnels of any size, depth of cover, and distance from the vertical face of the excavation. These design charts can be used by engineers and contractors for initial estimation, selection and preliminary design of excavation support system, and are particularly useful during the planning phase. Town planners and project managers, who need to decide on the feasibility, damage control and risk management aspects of a deep excavation project, may also find these design charts equally useful. It should, however, be kept in mind that the estimates obtained from these design charts are highly approximate and as such, should be taken as guidelines for decision making processes. These estimates do not replace site specific detailed analysis and monitoring.

Se ha llevado a cabo:A) Un estudio de las propiedades básicas del suelo no saturado (tipo limo) a escala microestructural, incluyendo esqueleto sólido, fase liquida y fase gaseosa. B) Elaboración de un modelo conceptual discontinuo de comportamiento. La geometría interna esta construida por partículas, agua retenida en forma de meniscos alrededor de los contactos y aire ocupando los restantes poros. La interfase liquido gas esta gobernada por la succión y la tensión superficial. Los meniscos tienen un efecto rigidizador del esqueleto.Se observa la posible redistribución de la humedad y del aire, quedando acoplados en definitiva los aspectos mecánicos y de flujo.C) En base a lo anterior, implementación de un modelo numérico discontinuo de ensayo de comportamiento basado en ordenador. Se ha adaptado y modificado el D.E.M. de P.A. Cundall (diferencias finitas explicitas en el tiempo), indicado en el caso que se trata, con no-linealidades geométricas. Se han desarrollado importantes algoritmos de control geométrico. D) Verificación parcial del modelo y aplicación a casos típicos en suelo no saturado, especialmente el colapso.En conjunto es una herramienta útil para su estudio y permite apreciar algunos interesantes mecanismos de actuación de la succión a escala microscópica.

This thesis presents a study of the effects of deep excavations on adjacent metro or utility tunnel in soft to medium soil. The main objective of the thesis is to develop a method of estimating these effects quantitatively. Extensive review of relevant literature published in the past four decades was conducted in order to understand the trends and the key developments in this area. It was revealed from the literature review that the concurrent use of the Observational Method and the finite element method for monitoring and controlling of ground deformations around the excavation has become a norm for deep excavation projects. Several design charts and guidelines for estimation of effects of deep excavations on adjacent raft foundations or pile foundations were found in the literature; however, no such charts or guidelines were found for estimation of effects of deep excavations on existing circular tunnels. Consequently, the development of these guidelines was established as one of the objectives of this study. <p>The initial phase of the research was focused on detailed study and analysis of two well-documented case studies the Chicago Subway Renovation Project, USA and the Tan Tock Seng Hospital Deep Excavation, Singapore. The back analyses of these two case studies were carried out using the finite element software PLAXIS. Exact site conditions and input parameters for the soil and the structural components were incorporated as much as possible. Appropriate adjustments in some of the input parameters were necessary to achieve good match between the computed and the observed results. <p> The back analyses were followed by parametric studies to identify important variables controlling the mechanisms of soil-structure interaction. The variables identified from the parametric studies of the two case studies were: soil stiffness, tunnel lining thickness, the depth of the excavation, and the location of tunnel. These variables were used to conduct a series of finite element analyses using simplified geometry and ground conditions for the purpose of formulating preliminary design charts. Results from these analyses were recorded in terms of in-plane and out-of-plane distortion of tunnel lining as well as additional shear forces and bending moments induced in the tunnel lining due to an adjacent deep excavation. The results were made non-dimensional before presenting them as contour plots. These contour plots constitute preliminary design charts, which can be used for the estimation of tunnel lining deformation caused by adjacent deep excavation.<p> Based on the results of this study, it can be concluded that a finite element program (such as PLAXIS) that is able to model construction processes associated with tunnelling and deep excavation in urban environment can be an invaluable tool in exploring the mechanism of ground deformation around the deep excavation and in quantifying the effects of ground deformation on existing adjacent structures. The modeller must, however, be aware of the fact that ways of modelling a particular construction process could be different for various finite element programs. It is important to interpret the instructions given in the manual of the program correctly. <p>Detailed back analyses of well-documented deep excavation case histories are vital from the point-of-view of building confidence in the selected finite element program. Such analyses also have the potential to identify key variables influencing the soil-structure interaction. <p> Preliminary design charts proposed in this thesis are very convenient for obtaining approximate values of tunnel lining deformation caused by adjacent deep excavation. Non-dimensional nature of these design charts makes it possible to be used for any depth of the deep excavation and for tunnels of any size, depth of cover, and distance from the vertical face of the excavation. These design charts can be used by engineers and contractors for initial estimation, selection and preliminary design of excavation support system, and are particularly useful during the planning phase. Town planners and project managers, who need to decide on the feasibility, damage control and risk management aspects of a deep excavation project, may also find these design charts equally useful. It should, however, be kept in mind that the estimates obtained from these design charts are highly approximate and as such, should be taken as guidelines for decision making processes. These estimates do not replace site specific detailed analysis and monitoring.

Anti ram perimeter barriers are part of the protection of important facilities such as power plants, air ports and embassies against unrestricted vehicle access. Many different systems can be used to achieve the containment goal. One of these systems makes use of soil embedded posts either single posts if the soil is hard enough or groups of soil embedded posts tied together by beams if the soil is not hard enough for a single post to stop the in-coming truck. The design of these soil embedded posts needs to take account a number of influencing factors which include the soil strength and stiffness, the post strength and stiffness, the mass of the vehicle and its approach velocity. This dissertation describes the work done to develop a set of design recommendations to select the embedment of a single post or group of posts. The post is a steel beam with an H shape cross section: W14X109 for the single post system and W14X90 for the group system with a double beam made of square hollow steel section HSS8X8X1/2. The spacing of the posts for the group includes 2.44 m, 4.88 m, and 7.32 m. The soil strength varies from loose sand and soft clay to very dense sand and very hard clay. The vehicle has a mass of 6800 kg and the velocities include 80 km/h, 65 km/h, and 50 km/h. The design guidelines presented here are based on 10 medium scale pendulum impact tests, 2 medium scale bogie impact tests, 1 full scale impact test on a single post, 1 full scale impact test on a group of 8 side by side posts with a 5.2 m spacing and connected with two beams, approximately 150 4-D numerical simulations of full scale impact tests using LS-DYNA, as well as fundamental theoretical concepts.

AN INVESTIGATION OF ACCURACY OF INERTIAL INTERACTION ANALYSES WITH FREQUENCY-INDEPENDENT IMPEDANCE COEFFICIENTS Yilmazok, &Ouml / zg&uuml / n M.S., Department of Civil Engineering Supervisor: Assoc. Prof. Dr. B. Sadik Bakir November 2007, 79 pages The inertial interaction between the soil and structure alters dynamic response characteristics of a structure due to foundation deformability, such that the flexibility and energy dissipation capability of surrounding soil may lead to a significant increase in period and damping of structural oscillations. The inertial interaction analyses can be accomplished through utilisation of frequency dependent foundation impedance coefficients that are reported in literature for various soil conditions and foundation types. However, such analyses should be performed in frequency domain, and applicable to only cases that linear structural response is considered. Alternatively, equivalent frequencyindependent foundation impedance coefficients can be employed, such that a constant excitation frequency is assumed in calculation of these coefficients. In this study, it is assumed that the fundamental frequency of a fixed-base structure, which can be obtained through employing available empirical relationships or a modal analysis, can be substituted for excitation terms in impedance expressions. The error induced in calculation of peak structural distortions is investigated through comparisons of structural response due to frequency-dependent and frequency-independent foundation impedance coefficients. For analyses, a linear single-degree of freedom oscillator is considered for modeling the structure. The frequency-dependent impedance of a rigid disk foundation resting on elastic halfspace is simulated by a limited number of discrete elements. The response calculations are performed in frequency domain, through employing 72 acceleration records. It is concluded that, the natural frequency of fixed-base building can be considered as effective excitation frequency for calculation of foundation impedance coefficients, when the effect of inertial interaction on structural response is moderate. Through employing equivalent-linear approximation for the structural response, it is shown that the conclusion is also valid in cases that nonlinear structural response is considered. However, when the inertial interaction has more profound effects on the structural response, the use of natural frequency of flexible-base structure, which is calculated iteratively due to its dependence on foundation-impedance factors is recommended.

In today&rsquo / s world, buried structures are used for a variety of purposes in many areas such as transportation, underground depot areas, metro stations and water transportation. The serviceability of these structures is crucial in many cases following an earthquake / that is, the earthquake should not impose such damage leading to the loss of serviceability of the structure. The seismic design methodology utilized for these structures differs in many ways from the above ground structures. The most commonly utilized approach in dynamic analysis of underground structures is to neglect the inertial forces of the substructures since these forces are relatively insignificant contrary to the case of surface structures. In seismic design of these underground structures, different approaches are utilized like free-field deformation approach and soil-structure interaction approach. Within the confines of this thesis, seismic response of highway tunnels is considered through a case study on Bolu Tunnels, which are well documented and subjected to D&uuml / zce earthquake. In the analyses, the seismic response of a section of the Bolu tunnels is examined with 2-D finite element models and results are compared with the recorded data to evaluate the capability of the available analysis methods. In general, the results of analyses did not show any distinct difference from the recorded data regarding the seismic performance of the analyzed section and that the liner capacities were sufficient, which is consistent with the post earthquake condition of the Bolu Tunnels.