scholarly journals On equivalent granular void ratio and steady state behaviour of loose sand with fines

2008 ◽  
Vol 45 (10) ◽  
pp. 1439-1456 ◽  
Author(s):  
M. M. Rahman ◽  
S. R. Lo ◽  
C. T. Gnanendran
Keyword(s):  
Steady State ◽  
Void Ratio ◽  
Soil Mechanics ◽  
Back Analysis ◽  
B Value ◽  
Published Data ◽  
Factors Affecting ◽  
State Variable ◽  
Cyclic Resistance ◽  
Alternative State

Void ratio has traditionally been used as a state variable for predicting the liquefaction behaviour of soils under the critical state soil mechanics framework. Recent publications show that void ratio may not be a good state variable for characterizing sand with fines. An alternative state variable referred to as the equivalent granular void ratio has been proposed to resolve this problem. To calculate this alternative state variable, a b parameter is needed. This b parameter represents the fraction of fines that actively participate in the force structure of the solid skeleton. However, predicting the value of b is problematic. Most, if not all, of the b values reported were determined by case-specific back-analysis, that is, the b value was selected so that a single correlation between equivalent granular void ratio and the measured steady state strength (or cyclic resistance) could be achieved. This paper examines the factors affecting the b value based on published work on binary packing. This leads to a simple semi-empirical equation for predicting the value of b based on fines size and fines content. Published data appear to be in support of the proposed equation. A series of experiments were conducted on a specially designed sand–fines type to provide additional validation of the proposed equation and to reinforce the use of equivalent granular void ratio in a more generalized context.

Collapse behavior of sand

1993 ◽  
Vol 30 (4) ◽  
pp. 569-577 ◽  
Author(s):  
S. Sasitharan ◽  
P.K. Robertson ◽  
D.C. Sego ◽  
N.R. Morgenstern
Keyword(s):  
Steady State ◽  
Void Ratio ◽  
Boundary Surface ◽  
Stress Path ◽  
Published Data ◽  
Stress Deviator ◽  
State Strength ◽  
Flow Slides ◽  
State Boundary ◽  
Collapse Behavior

Loose cohesionless materials can collapse during either static or dynamic loading, resulting in a rapid buildup of pore pressure and associated reduction in shear resistance. As the cohesionless material collapses, it rapidly looses resistance until the acting shear stress decreases to the available residual or steady-state strength. Specially designed stress-path testing has been performed on sand to investigate this collapse process. Results from this test program and previously published data show that a state boundary can be defined when a cohesionless material moves from peak to steady state along a constant void ratio stress path regardless of whether it is loaded drained or undrained. Further, it is demonstrated that the state boundary represents a surface in the effective mean normal stress–deviator stress–void ratio space. Hence, flow slides and liquefaction can be initiated when the stress path followed during either drained or undrained loading attempts to cross this state boundary surface. Key wordy : sand, collapse, liquefaction, stress path, state boundary, triaxial test.

The Nerlerk berm case history: some considerations for the design of hydraulic sand fills

1991 ◽  
Vol 28 (4) ◽  
pp. 601-612 ◽  
Author(s):  
Jean-Marie Konrad
Keyword(s):  
Steady State ◽  
Large Scale ◽  
Void Ratio ◽  
Strain Softening ◽  
Back Analysis ◽  
Confining Stress ◽  
Hydraulic Fill ◽  
State Strength ◽  
Undrained Strength ◽  
Unique Relationship

Back-analyses of recent large-scale slides during the hydraulic placement of an articial sand island at the Nerlerk site (Beaufort Sea) using different methods have resulted in contradictory conclusions with respect to the state of the fill. All the interpretation methods assume a unique relationship between steady-state strength and void ratio. This assumption is, however, not verified, since steady-state strength depends also on effective confining stress. This paper presents the results of a back-analysis at the Nerlerk site using a modified concept proposed by the author which isbased on nonunique values of steady-state strength for a given sand. It is established that the density conditions at Nerlerk, on average at a relative density of about 40%, and the initial stress conditions are conducive to strain softening, with a steady-state strength corresponding to the minimum strength defined by the LF line. For Nerlerk sand,the minimum undrained strength is about 18% of the steady-state strength determined with conventional methods using high confining stresses. The Nerlerk berm failures were thus "liquefaction" slides induced most likely by progressive straining. Key words: sand, undrained, strength, steady state, hydraulic fill.

Recent Studies of Tire Braking Performance

1973 ◽  
Vol 1 (2) ◽  
pp. 121-137 ◽  
Author(s):  
J. L. McCarty ◽  
T. J. W. Leland
Keyword(s):  
Steady State ◽  
Rapid Cycling ◽  
Single Cycle ◽  
Steering Angle ◽  
Slip Ratio ◽  
Factors Affecting ◽  
Braking Performance ◽  
Constant Rate

Abstract The results from recent studies of some factors affecting tire braking and cornering performance are presented together with a discussion of the possible application of these results to the design of aircraft braking systems. The first part of the paper is concerned with steady-state braking, that is, results from tests conducted at a constant slip ratio or steering angle or both. The second part deals with cyclic braking tests, both single cycle, where brakes are applied at a constant rate until wheel lockup is achieved, and rapid cycling of the brakes under control of a currently operational antiskid system.

Biodynamic Modeling of a Pedestrian Impact With a Rigid Frontal Guard of a Utility Vehicle

2010 ◽  
Author(s):  
Rasoul Moradi ◽  
Chandrashekhar K. Thorbole ◽  
Michael McCoy ◽  
Hamid M. Lankarani
Keyword(s):  
Front Surface ◽  
Body Region ◽  
Computational Technique ◽  
Surface Model ◽  
Published Data ◽  
Factors Affecting ◽  
Light Trucks ◽  
Accident Data ◽  
Facet Surface ◽  
The Impact

Accident data reveals that in most pedestrian accidents, the pedestrian head and lower extremity are vulnerable to serious injuries. The vehicle front geometry profile as well as the impact speed are important factors affecting the pedestrian kinematics and injury potential. In the US, accident data also shows that the fatality rate for pedestrian/light trucks and vans (LTV) impact is greater than that for the pedestrian/passenger-car impact. Addition of a front guard on light trucks and sports utility vehicles to mitigate damage during off-road activity or to provide mounting points for extra lights, makes the pedestrian more vulnerable to the impact. In this paper, a computational technique is utilized to study the influence of the added front guard on the impacted pedestrian. A CAD model of a typical commercial frontal guard is developed and converted into a rigid facet model, and attached to the vehicle front. The validated standing dummy model in the MADYMO code is used to simulate a pedestrian, and the rigid facet-surface model of a pickup truck is used to generate a vehicle front surface. This computational model is validated by comparing the pedestrian kinematics with the published data. This study demonstrates that the pedestrian mid body region is more vulnerable with the addition of guard on the vehicle. The result from this study facilitates a better understanding of a guard design and its geometry profile as required to protect vulnerable road users.

Effects of fines on liquefaction behaviour in well-graded materials

2017 ◽  
Vol 54 (10) ◽  
pp. 1460-1471 ◽  
Author(s):  
Katherine A. Kwa ◽  
David W. Airey
Keyword(s):  
Critical State ◽  
Soil Mechanics ◽  
State Parameter ◽  
Triaxial Tests ◽  
Particle Sizes ◽  
Graded Materials ◽  
Fines Content ◽  
Cyclic Resistance ◽  
Wide Range ◽  
Soil Behaviour

This study uses a critical state soil mechanics perspective to understand the mechanics behind the liquefaction of metallic ores during transport by ship. These metallic ores are transported at relatively low densities and have variable gradings containing a wide range of particle sizes and fines contents. The effect of the fines content on the location of the critical state line (CSL) and the cyclic liquefaction behaviour of well-graded materials was investigated by performing saturated, standard drained and undrained monotonic and compression-only cyclic triaxial tests. Samples were prepared at four different gradings containing particle sizes from 9.5 mm to 2 μm with fines (<75 μm) contents of 18%, 28%, 40%, and 60%. In the e versus log[Formula: see text] plane, where e is void ratio and [Formula: see text] is mean effective stress, the CSLs shifted upwards approximately parallel to one another as the fines content was increased. Transitional soil behaviour was observed in samples containing 28%, 40%, and 60% fines. A sample’s cyclic resistance to liquefaction depended on a combination of its density and state parameter, which were both related to the fines content. Samples with the same densities were more resistant to cyclic failure if they contained higher fines contents. The state parameter provided a useful prediction for general behavioural trends of all fines contents studied.

Factors Affecting Choice of Working Stresses for High-Temperature Service

1933 ◽  
Vol 1 (3) ◽  
pp. 99-102
Author(s):  
P. G. McVetty
Keyword(s):  
High Temperature ◽  
Published Data ◽  
Creep Tests ◽  
Fundamental Study ◽  
Factors Affecting ◽  
Creep Characteristics ◽  
The Stability ◽  
Safe Working

Abstract This paper discusses the various methods which have been proposed to determine safe working stresses for high-temperature service. The question of the stability of alloys during the test and in subsequent service is considered, with particular emphasis upon probable changes in creep characteristics during long exposure to stress and temperature. It is shown that published data in general do not admit of extrapolation, and that attempts to estimate total creep in service from such data are not usually satisfactory. The author stresses the need for more fundamental study of the laws governing creep rather than creep tests of many different materials.

‘Quit while you are ahead – and smell the roses!’ A survey of retired Fellows of the Australian and New Zealand College of Anaesthetists

2021 ◽  
pp. 0310057X2110057
Author(s):  
Diana Strange Khursandi ◽  
Victoria Eley
Keyword(s):  
Clinical Practice ◽  
New Zealand ◽  
Standard Deviation ◽  
Response Rate ◽  
Common Factors ◽  
Published Data ◽  
Factors Affecting ◽  
Retirement Decisions ◽  
Zealand College ◽  
The Mean

There are no published data on the age of retirement of anaesthetists in Australia and New Zealand. We surveyed 622 retired Fellows of the Australian and New Zealand College of Anaesthetists to determine their ages of complete retirement from clinical practice, demographics, and whether they had retired at the age they had intended to retire. We also aimed to explore factors affecting the decision to retire, the practice of ‘winding down’, common post-retirement activities, and the arrangement of personal and professional affairs. Responses were received from 371 specialists (response rate 60%). The mean (standard deviation) age of retirement was 65.2 (6.9) years. The mean (standard deviation) retirement ages ranged from 62.0 (7.1) years (those who retired earlier than planned) to 68.0 (4.3) years (those who retired later than they had intended). The mean (standard deviation) age of retirement of the male respondents was 66.0 (6.5) years, and for female respondents was 62.7 (7.7) years. Two hundred and thirty-three respondents (63%) reported winding down their practice prior to retirement, and 360 (97%) had made a will. Poor health and loss of confidence were the two most common factors in the retirement decisions of those who retired earlier than they had planned. Our results may assist current practitioners plan for retirement, and suggest strategies to help health services, departments and private groups accommodate individuals in winding down their practice.

scholarly journals Prediction Model of Minimum Void Ratio for Various Sizes/Shapes of Sandy Binary Mixture

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Chaojie Shen ◽  
Zhaoyang Xu ◽  
Jie Yin ◽  
Jinfeng Wu
Keyword(s):  
Particle Size ◽  
Binary Mixture ◽  
Particle Shape ◽  
Void Ratio ◽  
Soil Mechanics ◽  
Influence Factors ◽  
Natural Sand ◽  
Undetermined Coefficient ◽  
Shape Characteristics ◽  
Different Origins

The minimum void ratio is a fundamental physical index for evaluating particle properties in soil mechanics, ceramic processing, and concrete mixes. Previous research found that both particle size distribution and particle shape characteristics would affect minimum void ratio, while the current research generally uses a linear model to estimate the minimum void ratio of a binary mixture, ignoring quantitative effect of particle shape on the minimum void ratio. Based on a study of binary mixtures of natural sand from three different origins and iron particles of two different shapes, this paper analyzes the influence factors of the minimum void ratio, and a quadratic nonlinear model is proposed for estimating the minimum void ratio of binary mixture. The model contains only one undetermined coefficient, a, the value of which is correlated to the particle sphericity, particle size, and particle size ratio. A theoretical calculation formula for the coefficient a is proposed to quantitatively analyze the effects of these three factors on the size of the parameters. In the end, the model is used to estimate the minimum void ratios of sand and substitute particles from different producing areas; the average difference between the estimated values and the fitted values is about 2.03%, suggesting that the estimated values of the model fit well with the measured data.

scholarly journals Modelling shear strength of compacted soils

2019 ◽  
Vol 92 ◽  
pp. 15007
Author(s):  
Sam Bulolo ◽  
Eng Choon Leong
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Soil Mechanics ◽  
Published Data ◽  
State Variables ◽  
Compacted Soils ◽  
Earth Structures ◽  
Unsaturated Soil Mechanics ◽  
Coulomb Failure Criterion ◽  
Direct Shear Apparatus

Compacted soils constitute most engineering projects such as earth dams, embankments, pavements, and engineered slopes because of their high shear strength and low compressibility. The shear strength of compacted soils is a key soil parameter in the design of earth structures but it is seldom determined correctly due to their unsaturated state. The shear strength of compacted soils can be better evaluated under the framework of unsaturated soil mechanics. Saturated and unsaturated tests were conducted on compacted specimens using conventional direct shear apparatus under constant water content condition. Tests were conducted at different water contents and net normal stresses. The main objective of this study is to develop a shear strength model for compacted soils. Initial matric suction was measured before the test using the filter paper method. The two-stress state variables together with the extended Mohr-Coulomb failure criterion for unsaturated soils were used to obtain a lower bound model of the shear strength. The model was demonstrated using published data.

Soil mechanics: breaking ground

2007 ◽  
Vol 365 (1861) ◽  
pp. 2985-3002 ◽  
Author(s):  
Itai Einav
Keyword(s):  
Grain Size ◽  
Critical State ◽  
Void Ratio ◽  
Soil Mechanics ◽  
Constitutive Models ◽  
Energy Balance Equation ◽  
Constitutive Modelling ◽  
Alternative Theory ◽  
Fitting Parameters ◽  
Cam Clay

In soil mechanics, student's models are classified as simple models that teach us unexplained elements of behaviour; an example is the Cam clay constitutive models of critical state soil mechanics (CSSM). ‘Engineer's models’ are models that elaborate the theory to fit more behavioural trends; this is usually done by adding fitting parameters to the student's models. Can currently unexplained behavioural trends of soil be explained without adding fitting parameters to CSSM models, by developing alternative student's models based on modern theories? Here I apply an alternative theory to CSSM, called ‘breakage mechanics’, and develop a simple student's model for sand. Its unique and distinctive feature is the use of an energy balance equation that connects grain size reduction to consumption of energy, which enables us to predict how grain size distribution (gsd) evolves—an unprecedented capability in constitutive modelling. With only four parameters, the model is physically clarifying what CSSM cannot for sand: the dependency of yielding and critical state on the initial gsd and void ratio.

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