Thesis--M. Phil., University of Hong Kong.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

The calculation of a consolidation settlement is an important problem encountered in the foundation of buildings. Due to need for simplicity engineers are mainly using the one dimensional theory of Terzaghi for calculations of consolidation settlements with time. Consolidation tests are still performed in most laboratories with the traditional oedometer cell. Although the results of the oedometer can provide relatively reliable results, they are not equally effective for the calculation of the rate of consolidation. This primarily because of the inability of the oedometer cell to obtain full saturation of the sample. To ensure full saturation, back pressure must be applied which is not possible for conventional oedometer cell. The alternative use of the triaxial cell to examine the consolidation behavior of soils is discussed here.

The interface normal behavior between Ottawa sand and concrete for static and cyclic loading has been studied using Cyclic Multi Degree-of-Freedom test device. The static force controlled test for the interface showed exponential relation between normal stress and strain during initial loading, hyperbolic relation during unloading and linear relation during reloading. A series of cyclic force controlled interface tests are described for normal behavior and the interface behavior is found to be a function of the applied initial normal stress, the amplitude of the stress and the number of loading cycles. The reloading modulus is shown to increase with number of loading cycle. Also, a series of combined normal (force controlled) and shear (displacement controlled) tests are described in which the shear stress for given amplitude of shear displacement is found to increase as normal stress and number of loading cycles increases. The results of the laboratory tests for normal behavior are used to determine the parameters to describe the interface stress-strain response. The model is shown to describe the hysteresis behavior of the interface as a function of amplitude of normal stress and number of loading cycles. The model is used to predict the results of cyclic normal tests and combined normal and shear tests, and was found to yield satisfactory results. The interface model is implemented in a 2D nonlinear soil-structure interaction finite element procedure. The finite element procedure is verified with respect to simple problems for which close form solution or laboratory results are available. The response of the force controlled cyclic test and combined normal and shear test is then predicted using the FE procedure and reasonable results are obtained. A pier foundation subjected to base displacement is then analysed for different combinations of soil and interface behavior. Computer results are qualitatively compared with displacement and contact stresses and the effect of including the interface behavior is identified with respect to debonding and rebonding of the interface. The results of this research have provided understanding of the cyclic behavior of sand-concrete interface subjected to normal and combined normal and shear loading. The interface behavior has been represented by simple mathematical model for which parameters can be easily determined from static and cyclic tests. The model is also defined for general loading to incorporate debonding and rebonding and it is easy to implement into a FE procedure.

Foundation construction for spread wall footings normally involves constructing formwork, placing reinforcement, and pouring and curing concrete, regardless of footing size or the amount of anticipated load. Recently, the National Concrete Masonry Association (NCMA) has developed a complete foundation system called the Footer Block system. It was designed to reduce the costs of foundation construction for 1 and 2 story buildings. The footer black system consists of interlocking concrete blocks 10.2 x 40.6 x 20.3 cm (4 x 16 x 8 in). Because they are placed with no mortar, delays associated with the curing process or providing access for concrete are unnecessary. / Master of Science

Thesis (Civ.E)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982 / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 585-594. / by Imad Botros Ghantous. / Civ.E

Thesis: Sc. D., Massachusetts Institute of Technology, Department of Civil Engineering, 1977 / Vita. / Sc. D. / Sc. D. Massachusetts Institute of Technology, Department of Civil Engineering

Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Tunneling in busy urban areas is becoming a common practice, caused by the everincreasing number of commuters. This causes a decline in the service level that the surface transportation systems provide in cities. Tunneling induces movement of the soil directly surrounding the tunnel. These movements are translated into surface movements, which are translated into structural displacements of the surrounding surface infrastructure. These displacements, for which the infrastructure may not have been designed, put a question mark on the infrastructure aesthetics, serviceability, as well as structural stability. Burland and Wroth (1974) proposed a simple analytical damage assessment approach (Limiting tensile strain method (LTS)) to aid in the design of tunnels with respect to the structural integrity of the affected surface infrastructure. This study is concerned with the accuracy of this approach applied to the damage assessment of laterally unconfined, solid masonry walls, subject to a sagging mode of settlement deformation with no soil to wall friction. It is also concerned with the proposal of modifications to the approach, where deemed necessary. Finite element models of solid masonry walls are built and analysed in order to determine the accuracy of the simple analytical damage assessment approach with regard to the prediction of strains in solid masonry walls subject to tunneling-induced displacements. The predictions are found to be accurate for walls ofL/H ratio equal to 2 and larger. For walls of L/H ratio smaller than 2, the predictions are found to be underestimates. The simple analytical damage assessment approach is unable to account for the stiffness of the soil directly under the foundation of the wall. The stiffness of the soil plays a major role in the stress and strain distributions in the wall. It is therefore deemed necessary to modify the simple analytical damage assessment approach by accounting for the soil to wall interaction and the effect it has on the settlement damage to solid masonry walls. The soil to wall interaction is found to reduce the number of mitigating measures originally recommended for the walls, by the simple analytical damage assessment approach, as it accounts for the bedding of the wall into the soil previously unaccounted for. This study has reached the point where it is able to accurately predict whether a laterally unconfined, solid masonry wall, subject to a sagging mode of settlement deformation with no soil to wall friction will experience magnitudes of strain surpassing the yielding strain of the material. This was fundamentally achieved by developing a better representation of the strains in solid masonry walls as well as accounting for the inherent soil to wall interaction This study is intended to pioneer the proliferation of similar studies for various other structures. A methodology, applicable for similar investigations envisaged for other structures, is hereby developed. / AFRIKAANSE OPSOMMING: Tonnels in besige stedelike gebiede is besig om 'n allerdaagse verskynsel te raak a.g.v. die skerp toename in pendelaars. Die rede hiervoor is die afname in die kwaliteit van bogrondse vervoerdienste. Tonnels veroorsaak beweging van grond direk in aanraking met die tonnel. Hierdie bewegings versprei na die oppervlak wat strukturele verplasings veroorsaak. Vir n' struktuur wat nie vir hierdie verplasings ontwerp is nie, ontstaan vrae oor die estetika, diensbaarheid asook die stabiliteit van die struktuur. Burland en Wroth (1974) het 'n eenvoudige analitiese skade-assesseringsmetode voorgestel (Limiting tensile strain method (LTS)) vir die ontwerp van tonnels m.b.t. die strukturele integriteit van die geaffekteerde oppervlak se infrastruktuur. Hierdie studie handeloor die akkuraatheid van dié benadering, toegepas op die assessering van skade op lateraalonbeperkte, soliede messelwerkmure, onderhewig aan die deurbuigings mode van versakkingsdeformasie, met geen grond tot muur wrywing. Eindige element modelle van messelwerkmure is gebou en geanaliseer om die akkuraatheid van die eenvoudige analitiese skade-assesseringsmetode te bepaal, m.b.t. die voorspelling van die vervormings in messelwerkmure onderhewig aan grondverplasings veroorsaak deur tonnels. Die voorspellings is akkuraat in mure met lengte tot hoogte (L/H) verhoudings van 2 en hoër. Vir mure met LIH verhoudings van minder as 2, word daar gevind dat die voorspellings onkonserwatief is. By die eenvoudige analitiese skade-assesseringsmetode word die styfheid van grond direk onder die fondasies van die muur nie in ag geneem nie. Die grondstyfheid speel 'n kardinale rol by die spannings- en vervormingsverdelings in die muur. Dit is daarvoor nodig om die eenvoudige analitiese skade-assesseringsmetode aan te pas om die grond tot muur interaksie in ag te neem. Die interaksie tussen die grond en die muur veroorsaak 'dat a minder of geen skade voorkomende maatreëls getref hoef te word as wat oorspronklik deur die envoudige analitiese skade-assesseringsmetode voorgestel sou word. Dit neem die inbedding van die muur in die grond in ag, wat voorheen geïgnoreer is. Die studie het 'n punt bereik waar dit akkuraat kan voorspelof 'n lateraalonbeperkte, soliede messelwerkmuur, onderhewig aan die deurbuiging mode van versakkingsdeformasie en met geen grond tot muur wrywing, vervormings hoër as die swigvervorming van die material salondervind. Dit is bereik deur 'n beter voorstelling van die vervormings in soliede messelwerkmure asook die in agneming van inhirente grond tot muur interaksie. Die studie is veronderstel om die voorganger te wees vir soortgelyke studies toegepas op verskeie ander struktuurklasse. Die sistematiese metode wat hier ontwikkel is kan toegepas word op die ander struktuurklasse.

Shallow foundations are extensively used to support structures of all sizes and derive their support from near surface soils. Thus, they are typically embedded up to a few meters into the soil profile. Designers of shallow foundations are required to meet two limit states: overall failure of the soil beneath the foundation (bearing capacity) and excessive settlement. Existing bearing capacity design methods use an assumed shearing plane within the soil and perfectly plastic soil behavior to estimate the ultimate resistance available. The immediate settlement of a shallow foundation is typically approximated using an elasticity-based method that does not account for actual, nonlinear soil behavior. A load test database was developed from footing load tests reported in the literature to assess the accuracy and uncertainty in existing design methodologies for calculating bearing capacity and immediate settlement. The assessment of uncertainty in bearing capacity and immediate settlement was accomplished through the application of a hyperbolic bearing pressure-displacement model, and the adaptation of the Duncan-Chang soil constitutive model to footing displacements. The prediction of bearing capacity using the general bearing capacity formula was compared to the bearing capacity extrapolated from the load test database using a hyperbolic bearing pressure-displacement model. On average the general bearing capacity formula under-predicts the bearing capacity and exhibits a significant amount of variability. The comparison was used to develop resistance statistics that were implemented to produce resistance factors for an LRFD based design approach using AASHTO load statistics. The Duncan-Chang model was adapted to predict bearing pressure displacement curves for footings in the load test database and used to estimate governing soil parameters. Bearing pressure-displacement curves fitted to the observed curves were used to back calculate soil stiffness. The soil stiffness was used with an elasticity-based displacement prediction method to evaluate the accuracy of the method. Finally, the back-calculated modulus from the fitted Duncan-Chang model was used to assess the accuracy and uncertainty associated with the elasticity-based K-factor, a correlation based stiffness parameter. In general the comparisons indicate that the current design procedures over-predict the bearing pressure associated with a given displacement and exhibit a significant amount of uncertainty. / Graduation date: 2012