Thesis (Ph. D.)--University of Hawaii at Manoa, 2000. / Includes bibliographical references (leaves 170-177). Also available on microfiche.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1972. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

The research presented in this thesis can be split into two well-defined areas. Firstly, the effects of the addition of lime (either 2%, 4%, 6% or 8% Ca(OH)2 or 1.5%, 3%, 4.5% or 6% CaO) on various engineering properties of a sulphide (pyrites) rich, naturally occurring clay - Lower Oxford Clay (LOC) - were studied. Experimental tests representing, or relating to, tests outlined in the Design and Construction of Lime Stabilised Capping Specification (DoT, 1995) were utilised and consisted of Atterberg (consistency) tests, compaction tests, unconfined compressive strength tests, linear expansion measurements and durability tests. Also, sulphate (S03) analyses, pH measurements, differential thermogravinietric (DTG) analyses and X-ray diffraction (XRD) tests were employed to confirm experimental data. Environmental conditions were chosen to reflect temperatures experienced in the UK - between 5°C, 10°C and 20°C. The majority of samples were mellowed (the time delay between initial mixing and compaction) for 3 days at 20°C prior to testing. The results show that small additions of lime (i. e. 2% Ca(OH)2 or 1.5% CaO) modify the engineering properties of LOC by causing flocculation, and also increase S03 levels due to increased gypsum levels via pyrites oxidation. However, strength development is poor as little cementitious bonding is formed. Mellowing further modifies the engineering properties as the increased time allows greater flocculation leading to a less dense, more porous material. Also ettringite forms during mellowing allowing expansive reactions to occur prior to compaction, consuming both calcium and sulphate in the process and leading to slightly reduced pH levels compared to similar unmellowed samples. Further additions of lime give further change to the engineering properties of the LOC, up to an addition of 6% Ca(OH)2 or 4.5% CaO. Further additions result only in supplying an excess of calcium. Strength development is improved with increasing lime additions, especially after 4 weeks of curing at higher curing temperatures (20°C); however linear expansion increases and durability worsens. However, a period of mellowing prior to compaction reduces linear expansion and improves durability. Sulphate (S03) levels are also increased with increasing additions of lime due to pyrites oxidation. In samples containing >2% Ca(OH)2 or 1.5% CaO, pH levels are maintained to a level where ettringite formation is sustained rather than gypsum formation. Secondly, the effects of a secondary stabilising agent (ground granulated blast furnace slag - GGBS - incorporated at various percentage additions (2%, 4%, 6% or 8%)) on the strength development, linear expansion and durability of mellowed, lime-modified LOC is presented. For comparative purposes, Portland cement (PC) is also used. The results show that although LOC-lime-PC samples exhibit greater strengths (especially when cured for long periods at 20"C), linear expansion is lower and durability is higher in similar LOClime- GGBS samples. As the hydration process of PC produces lime, and as lime is usually consumed during GGBS hydration, then samples containing the former stabiliser will maintain pH levels well above samples containing the latter. Therefore, on soaking disruption and expansion due to the formation of ettringite (which is unstable at pH levels <10.5) is common to LOC-lime-PC samples but not in similar GGBS samples. In conclusion, the findings from this thesis indicate that soil stabilisation with lime and GGBS is particularly effective for naturally occurring sulphide rich clay soils (such as the LOC) and is an environmentally friendly alternative to PC-stabilised soils.

The stress/strain relationship for most engineering materials is known to be time dependent. This is most evident during a creep test in which continual deformations are observed under constant stress conditions. In the laboratory, a specimen of cohesive soil subjected to a constant shear stress may fail after having deformed alt relatively slow rates for a considerable time. This type of failure, termed creep rupture, is also known to occur in the field. Results of drained and undrained triaxial creep rupture tests are presented in this thesis. These tests were performed on a sensitive marine clay from western Canada which was consolidated to various stress histories. Pore pressure measurements were taken during undrained tests using an electrical transducer. In addition to the creep rupture tests, incremental load and constant strain rate triaxial tests were performed for comparative purposes. The strain rate during a creep rupture test was observed to initially decrease as the specimen strained, reach a transient minimum strain rate, and then increase until rupture. Failure was found to be inevitable whenever the strain rate started to increase after having reached a minimum value. Pore pressures measured during the undrained tests did not reflect the onset of creep rupture at the transient minimum strain rate, and therefore, the onset of creep rupture cannot be explained in terms of effective stresses. A relationship was found to exist between the deviator stress, strain and current strain rate during undrained triaxial tests having the same consolidation history. This relationship permitted the prediction of the results of constant strain rate tests based on the results of creep rupture tests. This resulted in an understanding of the interrelation between the transient minimum strain rate of a creep rupture test and the maximum deviator stress of a constant strain rate test. Once the transient minimum strain rate had been reached, the results of creep rupture tests showed that the strain rate was inversely proportional to the time remaining before rupture. This relationship is independent of stress level, consolidation history and drainage conditions. As a result, it is suggested that measurement of deformations in the field can be used to predict the time until a sudden failure would be anticipated. The upper yield strength, defined as the maximum compressive stress which will not cause a creep rupture failure, was evaluated from both creep rupture and constant strain rate tests. It was found that the compressive strength increased as a linear function of the cube root of the strain rate. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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