Decoupling the mechanical role of pore liquids in soils to liquid viscous effect and solid–liquid adhesion effect

Acta Geotechnica - This paper presents a novel conceptual approach for evaluating the mechanical effect of pore liquids on the overall geotechnical behavior. The approach is based on empiric...     

Steady‐state solution for cylindrical penetrometers

This paper suggests a new method for obtaining steady‐state solutions for ‘full‐flow’ penetrometers. The method is based on the numerical solution of the small strain plastic‐flow problem (i.e. rigid plastic material) with an inhomogeneous strength field, which is determined by converting changes of material properties over time in a stationary frame of reference into spatial distribution of strength in a moving frame of reference. Rather than building streamlines from back integration of soil element distortion, as previous methods have suggested, the method treats the domain as continuous with the associated field equations. The method employs an upstream weighting technique for the determination of information flow within the domain. The execution order for the calculation is based on topological ordering. This results in the calculation having a complexity of O(N), as compared with O(N^1.5) for the strain path or streamline methods (N is the number of discretized points), which significantly reduces the calculation time. The formulation is presented for the cylindrical (T‐bar) penetrometer, and includes aspects of soil strength degradation, strain rate effects, strength anisotropy, and interface strength law. Comparison to previously published values, based on large displacement finite element simulations with remeshing, showed good agreement, indicating on the correctness of the suggested approach. Investigation into the soil rigid‐body rotation and the remolding effect on anisotropy characteristics showed an interesting behavior, where the decrease of strength anisotropy due to remolding has a greater influence when the soil strength is higher in the vertical direction. Copyright © 2009 John Wiley & Sons, Ltd.     

The KC method: Numerical investigation of a new analysis method for reinforced soil walls

Reinforced soil walls commonly include facing elements which affect the mechanical behavior of the system. However, the design procedures involved in the existing codes and manuals (e.g. FHWA, BS8006, AASHTO, etc.) do not consider the structural contribution of the facing to the wall stability. Recently, a new computer based method for the analysis of reinforced soil walls which takes into account the interaction between the facing and the soil reinforcement layers was presented [Klar A and Sas T. Rational approach for the analysis of segmental reinforced soil walls based on kinematic constraints. Geotextiles and Geomembranes 2009;27:332-340]. This method demands full compatibility between the reinforcement layers and the deforming wall, and is solved as an optimization problem on this constraint. This kinematic compatibility (KC) method entails several assumptions regarding the interaction between the three components of the system (soil, wall, and reinforcement). This paper compares the KC method to a more rigorous continuum analysis. Results show that the KC method is capable of replicating the behavior of the more rigorous system, with a good agreement on both the value of maximum tensile forces in the reinforcement and shear and bending moment distributions along the wall. The KC method has a certain advantage over continuum methods, such as finite element or finite difference, since it requires limited input data that can easily be obtained from field tests.     

Sound waves excitation by jet-inflated bubbles in clusters of galaxies

We show that repeated sound waves in the intracluster medium (ICM) can be excited by a single inflation episode of an opposite bubble pair. To reproduce this behaviour in numerical simulations, the bubbles should be inflated by jets, rather than being injected artificially as already full-blown bubbles. The multiple sound waves are excited by the motion of the bubble–ICM boundary that is caused by vortices inside the inflated bubbles and the backflow ('cocoon') of the ICM around the bubble. These sound waves form a structure that can account for the ripples observed in the Perseus cooling flow cluster. We inflate the bubbles using slow massive jets either with a very wide opening angle or that are narrow and precessing. The wide jets (or collimated fast winds) are slow in the sense that they are highly subrelativistic,   v _j∼ 0.01 c – 0.1 c   , and they are massive in the sense that the pair of bubbles carries back to the ICM a large fraction of the cooling mass, i.e.  ∼1–50 M_⊙ yr⁻¹  . We use a two-dimensional axisymmetric (referred to as 2.5D) hydrodynamical numerical code ( vh-1 ).