Pure elastic stiffness of sand represented by response envelopes derived from cyclic triaxial tests with local strain measurements

Acta Geotechnica - The elastic stiffness of a fine sand at small to moderate strains ( $$\varepsilon \le 2 \times 10^{-4}$$ ) has been studied based on cyclic triaxial tests on cube-shaped samples...     

Preliminary Interlaboratory Trial for ISO/DIS 12010: Determination of Short Chain Polychlorinated Alkanes (SCCP) in Water

A first preliminary interlaboratory trial was planned to prepare ISO/DIS 12010: Water quality – determination of short chain polychlorinated alkanes (SCCP) in water – method using GC/MS and electron capture negative ionisation (ECNI). The task was to determine the sum of short chain polychlorinated n‐alkanes with carbon chain lengths of C₁₀–C₁₃ and a chlorine content between 49 and 67% in water by GC‐ECNI‐MS and quantification by multiple linear regression described in ISO/DIS 12010 as the compulsory method. Distributed samples were obtained from a real water extract spiked with a target concentration of 0.4 µg/mL sum of SCCP, i.e. the environmental quality target level according to the Water Framework Directive. The interlaboratory trial included the calibration, a column chromatographic clean up, a concentration step and an integration of chromatographic unresolved humps as well as the quantification with multiple linear regression. Reproducibility standard deviations between 21.5 and 22.9% were achieved by 17 participating laboratories from four countries. The method outlined no significant difference of the results between the standard solution and a real water matrix extract. On the basis of this succeeded preliminary interlaboratory trial the final interlaboratory trial for validation of ISO 12010 was prepared in autumn 2010.     

Shear banding in geomaterials under extensional plane strain conditions: Physical and analytical model

The shear band (SB) spacing phenomenon in geomaterials is addressed in this paper under plane strain extensional conditions. On the basis of sand box observations, a method is proposed for the prediction of the spacing between shear bands based on the so-called “bookshelf” deformation mechanism. The proposed method is based on the assumption that the material is softening inside the shear bands whereas outside the SB it undergoes elastic unloading. The underlying assumption for the prediction of SB spacing is that the material reaches the lowest possible energy rate. An analytical expression for the determination of the shear band spacing is presented taking into account the plane strain extensional deformation of the specimen. The friction due to the normal off-plane shear acting on the boundaries is then taken into account.     

Centrifuge model tests on sand specimen under extensional load

The appearance of shear banding in granular materials has been investigated intensively during the last decades and is still of ongoing importance in terms of understanding the stress–strain behaviour of the material, the localization phenomena and the interaction between soil and structure. Only less attention has been paid to the occurrence of systems of shear bands although such systems can be identified in geotechnical structures as well as in geological formations. In this paper we present results of experiments on sand specimens under extensional load in natural gravity as well as in increased gravity in the centrifuge where the influence of the stress level on the geometry of a shear band pattern, specified by the spacing of the shear bands and the angle between failure surfaces and minor stress direction, has been investigated. X‐ray technique has been used to visualize the failure zones inside the specimen, an optical measurement system called Digital Image Correlation has been applied to identify and observe the appearing deformation mechanism on the sides of the specimens in natural gravity as well as during the flight in the centrifuge. It can be shown that the geometry of the shear band pattern is sparsely influenced by the change of the stress level. Copyright © 2004 John Wiley & Sons, Ltd.     

Großkreisdifferenzgleichen

Summary Echo soundings of the U.S. Cruiser Milwaukee in the Puerto Rico Trough in 1939 are briefly discussed, and two depths of 30246 feet or 9219 m, found at 19° 36 N, 68° 20.5 W and at 19° 35N, 68° 8.75W, are stated to be the greatest depths which are known so far in the Atlantic Ocean.