The influence of cementation on liquefaction resistance of sands
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Cohesionless sands are known to be susceptible to failure by liquefaction when they are saturated and subjected to earthquake shaking. Considerable study has been directed towards this subject over the past 20 years in recognition of the possibility of large-scale property damage or loss of life due to this type of failure. Recent evidence has shown that small degrees of cementation in a sand significantly reduce the likelihood of liquefication. However, the work to date has been limited to studies with conventional testing devices and simple loading paths. These devices are suspected of inducing premature failure in cemented soils, and are not capable of modeling the effects of multiaxial loading. In this investigation, there were two major objectives. The first involved the development and fabrication of a new three~dimensional shear device with the capability of applying load to cemented sands with a minimum of stress concentration effects, and of using load paths which are more representative of the true effects of an earthquake than is possible in conventional equipment. The second concerned performance of a series of production tests to investigate the behavior of cemented sands under a range of earthquake loading paths. The production tests were Iargely performed using the new three—dimensional shear device. The test results showed that cemented soils have more resistance to earthquake loading than previously thought since stress concentration effects in conventional testing do induce premature failure through the effects of stress concentrations. On the other hand, it was found that either cemented or uncemented sands show less resistance to earthquake loadings if multiaxial stress conditions are applied to the sample as opposed to uniaxial loadings. This is important in explaining the fact that sites with seemingly similar conditions often show different behavior, since slightly different earthquake loading pattems can cause different responses. One factor explaining differences in response is found to be the mean normal stress, which is not the same for all loadings, and plays an important role in the pore pressures developed in the soil.
- Doctoral Dissertations