Strain Softening of Siltstones in Consolidation Process

Strain softening is the mechanical behavior of soil and rock materials and is important in understanding soft rock foundation. To investigate the mechanical behavior of siltstone, a sedimentary soft rock, consolidation tests using constant-strain rate loading were conducted using the consolidation ring to constrain lateral deformation. Using Quaternary siltstones distributed in the Boso Peninsula, central Japan as specimens, strain softening in the consolidation process was confirmed in some formations using two test machines at Kyoto University and Nagoya Institute of Technology. Just before the yielding, stress decreased suddenly at increasing strain. The stress at the time of the softening differed even for specimens taken from the same formation. Furthermore, micro-focus X-ray CT images taken before and after the tests indicated that the specimens had no macro cracks inside. This suggests that strain softening is not due to brittle failure in local areas but due to the softening of the framework structure of the siltstone itself

Consolidation problem solution with a coupled hydro-mechanical formulation considering fluid compressibility

There are two principles which may be referred to as essentials to describing soil and rock behavior. The mechanical behavior is associated to the law of conservation of linear momentum, allowing forces balance analysis and the hydraulic behavior is characterized by mass conservation. These phenomena are related: stress-strain state is affected by fluid pressures and vice-versa. Therewith, it is intuitive the understanding of the importance of coupled analyses, which are certainly a more precise manner of describing how mechanical and hydraulic behavior are connected. Given certain difficulties related to the modeling process, porous media numerical model representation is usually simplified. In certain cases, simplifications do not imply on losses in results and behavior prediction. However, some situations require more comprehensive approaches, with development of previously neglected conditions. The main objective of this paper is to present a formulation for fully coupled hydro-mechanical analyses considering fluid and solids compressibility. This formulation, implemented in Finite Element program ALLFINE [1,2,3], was tested for a one-dimensional consolidation case. A sensitivity analyses for the fluid compressibility parameter using modified Cam-clay constitutive model showed that this consideration affects fluid pressure responses significantly, with a delay in fluid pressure dissipation during consolidation process. The simulations results were compared to Terzaghi’s analytical solution for the onedimensional consolidation problem. Also, the comparison of the simulation results to the analytical responses clearly shows the differences between using linear elastic and elastoplastic models. In simulations for different stress levels with the modified Cam-clay model, it is possible to capture a flow induction effect due to high stress levels

Explicit instructions and consolidation promote rewiring of automatic behaviors in the human mind

One major challenge in human behavior and brain sciences is to understand how we can rewire already existing perceptual, motor, cognitive, and social skills or habits. Here we aimed to characterize one aspect of rewiring, namely, how we can update our knowledge of sequential/statistical regularities when they change. The dynamics of rewiring was explored from learning to consolidation using a unique experimental design which is suitable to capture the effect of implicit and explicit processing and the proactive and retroactive interference. Our results indicate that humans can rewire their knowledge of such regularities incidentally, and consolidation has a critical role in this process. Moreover, old and new knowledge can coexist, leading to effective adaptivity of the human mind in the changing environment, although the execution of the recently acquired knowledge may be more fluent than the execution of the previously learned one. These findings can contribute to a better understanding of the cognitive processes underlying behavior change, and can provide insights into how we can boost behavior change in various contexts, such as sports, educational settings or psychotherapy

Modeling the Role of the Cell Cycle in Regulating Proteus mirabilis Swarm-Colony Development

We present models and computational results which indicate that the spatial and temporal regularity seen in Proteus mirabilis swarm-colony development is largely an expression of a sharp age of dedifferentiation in the cell cycle from motile swarmer cells to immotile dividing cells (also called swimmer or vegetative cells.) This contrasts strongly with reaction-diffusion models of Proteus behavior that ignore or average out the age structure of the cell population and instead use only density-dependent mechanisms. We argue the necessity of retaining the explicit age structure, and suggest experiments that may help determine the underlying mechanisms empirically. Consequently, we advocate Proteus as a model organism for a multiscale understanding of how and to what extent the life cycle of individual cells affects the macroscopic behavior of a biological system

EVALUATION OF TIME RATE OF CONSOLIDATION AND UNDRAINED SHEAR STRENGTH OF HYDRAULICALLY PLACED FINE COAL REFUSE

Fine coal refuse (FCR) refers to the fines generated during the processing of raw coal. FCR is usually mixed with flocculant and water and hydraulically placed behind impoundments. It is generally assumed that the FCR in these impoundments will consolidate over time due to the overburden weight of the materials above, losing some of the fluid-like properties that it possessed when initially placed. However, some in situ observations have shown that there exists under-consolidated material within slurry impoundments even after many decades of deposition. These under-consolidated materials can be prone to destabilization and flow, which can result in fatalities and environmental disasters. The purpose of this study is to investigate the consolidation behavior and effect of flocculant on the material properties and flowability of the FCR.Traditional consolidation tests were conducted on in situ FCR samples obtained from a range of depths behind an impoundment. The consolidation response of the in situ samples was compared with companion samples of fresh liquid slurry pre-consolidated to stresses corresponding to the depths of the recovered in situ samples. A finite difference model used to calculate time rate of consolidation of the FCR using variable coefficient of consolidation which was obtained by consolidating FCR slurry under different pressures. The results were compared to traditional Terzaghi method with constant coefficient of consolidation. Laboratory vane shear tests were conducted to study the influence of flocculant on undrained shear strength of the FCR and modified flow table tests performed on consolidated FCR slurry samples prepared with different background fluids.The results suggest that the variable coefficient of consolidation method may best predict the time rate of consolidation for the FCR slurry compared to traditional methods which use the in situ coefficient of consolidation. Although the particle size analysis revealed that the effect of flocculant degrades over the time, vane shear results suggest that the flocculant increases the undrained shear strength and can improve the FCR resistance to flow at early stages of consolidation. The results of this study give a better understanding of the consolidation behavior and undrained shear resistance of the hydraulically placed FCR behind impoundments

Influence of Reconsolidation Procedure on Small Strain Shear Modulus and Undrained Shear Behavior of Silts Subjected to Tube Sampling Disturbance

This thesis presents results of a laboratory testing program that studied the effects of laboratory simulated tube sampling disturbance on the undrained shear strength behavior of reconstituted low plasticity silts at overconsolidation ratios of 1.0 and 3.6. The three test soils consisted of two different mixtures of kaolin clay and silica silt and a reconstituted natural Dedham silt. Triaxial tests with bender elements were conducted on the reconstituted samples using the Ideal Sampling Approach (ISA) followed by post-ISA reconsolidation and undrained shear. The specimens were subjected to ± 1% and ± 3% ISA axial strain cycles. Changes in shear wave velocity and small strain shear modulus during simulation of tube sampling was used to develop a better understanding of the effects of sample disturbance on the undrained stress-strain-strength behavior of silts. Laboratory simulated tube sampling disturbance changed the undrained shear behavior of the low plasticity silts from contractive to dilative. The reconstituted silt samples experienced significant loss in effective stress due to ISA disturbance which decreased with an increase in overconsolidation ratio and plasticity. The normalized undrained shear behavior of the tested reconstituted silt samples did not show any dependency on the consolidation stress level, however, an increase in the consolidation stress level increased the tendency for the low plasticity silts to exhibit dilative behavior. The effect of Recompression and SHANSEP consolidation procedures on recovering the undisturbed behavior was found to be dependent on the plasticity of the soil, to some extend on the pre-ISA consolidation stress, level of ISA disturbance experienced by the specimen and the overconsolidation ratio. The measured shear wave velocity and small strain shear modulus at various stress states showed significant reduction during ISA disturbance which could be used as an indicator of sample disturbance in similar types of silts. However, after reconsolidating the specimens back to the initial effective stress state the shear wave velocity and small strain shear modulus values were mostly recovered indicating little to no influence of sample disturbance. The amount of reduction in shear wave velocity and small strain shear modulus was found to be dependent on plasticity of soil, level of disturbance and overconsolidation ratio

From creation to consolidation: a novel framework for memory processing

Long after playing squash, your brain continues to process the events that occurred during the game, thereby improving your game, and more generally, enhancing adaptive behavior. Understanding these mysterious processes may require novel theories

The State of e-Banking Implementation in Nigeria: A Post-Consolidation Review

The most widely used e-Banking instrument in �igeria is e-Payment, particularly the automatic teller machine (ATM) card. However, with the adoption of e-Banking by all the banks in �igeria, the volume of cash in circulation has continued to increase pre-and-post bank recapitalization/consolidation exercise. Furthermore, some of the 25 banks that survived the exercise were found lately to have depleted their capital base and have lost credibility before the consumers, e-Banking implementation notwithstanding. Therefore, in this paper, we review the state of e-Banking implementation in �igeria and evaluate the influence of trust on the adoption of e-Payment using an extended technology acceptance model (TAM). Similarly, we investigate organizational reputation, perceived risk and perceived trust in the management of banks as a factor for enhancing customer loyalty. The findings in this work reveal that perceived ease of use and perceived usefulness are not only antecedent to ebanking acceptance, they are also factors to retain customers to the use of e-banking system such as organizational reputation, perceived risk and trust

Stress-induced reduction of dorsal striatal D2 dopamine receptors prevents retention of a newly acquired adaptive coping strategy

The inability to learn an adaptive coping strategy in a novel stressful condition leads to dysfunctional stress coping, a marker of mental disturbances. This study tested the involvement of dorsal striatal dopamine receptors in the dysfunctional coping with the Forced Swim test fostered by a previous experience of reduced food availability. Adult male mice were submitted to a temporary (12 days) reduction of food availability [food-restricted (FR)] or continuously free-fed (FF). Different groups of FF and FR mice were used to evaluate: (1) dorsal striatal mRNA levels of the two isoforms of the dopamine D2 receptor (D2S, D2L). (2) Forced Swim-induced c-fos expression in the dorsal striatum; (3) acquisition and 24 h retention of passive coping with Forced Swim. Additional groups of FF mice were tested for 24 h retention of passive coping acquired during a first experience with Forced Swim immediately followed by intra-striatal infusion of vehicle or two doses of the dopamine D2/D3 receptors antagonist sulpiride or the D1/D5 receptors antagonist SCH23390. Previous restricted feeding selectively reduced mRNA levels of both D2 isoforms and abolished Forced Swim-induced c-fos expression in the left Dorsolateral Striatum and selectively prevented 24 h retention of the coping strategy acquired in a first experience of Forced Swim. Finally, temporary blockade of left Dorsolateral Striatum D2/D3 receptors immediately following the first Forced Swim experience selectively reproduced the behavioral effect of restricted feeding in FF mice. In conclusion, the present results demonstrate that mice previously exposed to a temporary reduction of food availability show low striatal D2 receptors, a known marker of addiction-associated aberrant neuroplasticity, as well as liability to relapse into maladaptive stress coping strategies. Moreover, they offer strong support to a causal relationship between reduction of D2 receptors in the left Dorsolateral Striatum and impaired consolidation of newly acquired adaptive coping