Experimental study of the overconsolidation and saturation effects on the mechanical characteristics and residual strength of Chlef river sandy soil
This paper presents a laboratory study of the influence of the saturation evaluated in terms of Skempton´s pore pressure coefficient (B) and overconsolidation ratio (OCR) on the behavior of Chlef sand. The study is based on drained and undrained triaxial compression tests which were carried out for Skempton´s pore pressure coefficient varying between 13 and 90% and OCR varying between 1 and 8. Tests were conducted on medium dense sand samples having an initial relative density Index Id = 0.5 at an effective stress of 100 kPa. The paper is composed of two parts. The first one presents the characteristics of the sand used in this study, the second provides an analysis of the experimental results and discusses the influence of Skempton´s pore pressure coefficient (B) and OCR on the mechanical characteristics of the sand. The tests show that the increase in the Skempton´s pore pressure coefficient (B) reduces the soil dilatancy and amplifies the phase of contractancy and reduces the frictional and characteristic
angle of the sand. The increase of OCR improves the stiffness of sand and accelerates the appearance of dilatancy; and increases frictional and characteristic angle of the sand. Moreover, the present study focuses on the effect of saturation and overconsolidation on the residual shear strength of sand.
Genesis of transitional behaviour in geomaterials: a review and gap analysis
ABSTRACT There has been sporadic but increasing reporting regarding the intermediate character of natural geomaterials which neither conforms to the general behaviour of fine-grained (clay-like) nor coarse-grained (sand-like) soils. Nonetheless, geoscience considers such soils as non-textbook or challenging geomaterials. The literature attempts to identify and analyse a range of threshold manifestations of their behaviour (e.g. liquefaction). However, the physics behind their transient nature is not described in a generic manner. Transitional behaviour (TB) is observed more often in soils containing measurable amounts of silt-size particles. The complexity of their structure – greatly dependent on a number of interrelated micro and macro parameters – is believed to discourage generalisation of the behaviour. This review collates the factors potentially controlling the reported transient character. In order to illustrate a more holistic picture of transitional soils, the available characterisation findings are critically categorised based on purpose and/or testing technique. Collective understanding of transitional soils can ultimately provide a more confident prediction of their ramifications in a wide spectrum of applications. The present initiative is meant to attract attention to the need for multidisciplinary research on quantifying the controversial character of this class of geomaterials. It is also attempted to highlight relevant discrepancies and identify research gaps.
Time and Heritage
As a historian studying what can be considered a form of intellectual history, I have slowly come to adopt Michel de Certeau’s observation made at the end of the 1980s that ‘objectifying the past, for the last three centuries, has undoubtedly left unconsidered time within a discipline that has continued to use it as a taxonomic instrument’. To a certain degree, time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it. As a historian attempting to pay attention to the time I’m living in, I have thus, like many others, noticed the swift development of the category of the present until it has become obvious that the present is omnipresent. This is what I refer to here as ‘presentism’.