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Article
Publication date: 1 February 1992

MATTHEW R. KUHN and JAMES K. MITCHELL

The discrete element method (DEM) was used to stimulate creep processes in granular materials. The authors present the main features of the numerical model, which include…

Abstract

The discrete element method (DEM) was used to stimulate creep processes in granular materials. The authors present the main features of the numerical model, which include a new viscous mechanism for particle sliding, a new feedback technique for maintaining constant stress during creep, and a scaling technique that allowed monitoring the long‐term creep behaviour of a granular assembly. The creep behaviour of the numerical model exhibited the essential characteristics of soil creep—a creep rate that decreased rapidly with time, an increase in the creep rate with the applied deviator stress, and the beginning of creep rupture. The model's numerical performance is discussed, and representative results are presented.

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Engineering Computations, vol. 9 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 28 August 2009

Ravindra K. Pande, Dhanjita Burman and Ravinder Singh

The purpose of this paper is to evaluate landslide hazard problems in Hanuman Chatti area of Uttarakhand, India. Every year NH 58 experiences landslide activities, which…

Abstract

Purpose

The purpose of this paper is to evaluate landslide hazard problems in Hanuman Chatti area of Uttarakhand, India. Every year NH 58 experiences landslide activities, which disrupts the tourist traffic to Badrinath shrine and higher Himalaya.

Design/methodology/approach

An urgent need is being felt to have a comprehensive landslide hazard evaluation factor (LHEF). The major causative factors that influence the slope stability are lithology, structure, soil depth, soil texture, geomorphology, slope morphology, slope dip, slope aspect, slope magnitude, weathering, land use and land cover and anthropogenic activities. The present analysis is based on the rating scheme in which numerical ratings for different categories are determined on the basis of their estimated significance in causing instability.

Findings

In the study area, nine old landslides (0.238 sq.km) and five new landslides (0.086 sq.km) are recorded. On the basis of the various causative factors the study area is classified into five landslide hazard classes.

Research limitations/implications

The analysis is based on the experience gained for the last seven years (1999‐2007). The period is short for developing any hypothesis but sufficient care has been taken to consider vital factors.

Practical implications

With the help of LHEF appropriate landslide hazard management tools can be adopted. Once a LHEF rating scheme in which numerical ratings for different categories are determined on the basis of their estimated significance in causing instability, is standardized it can be applied to the entire Himalayan region, which is very prone to landslide hazard.

Originality/value

Although the paper is an attempt to evaluate the efficacy of landslide hazard zonation techniques developed by various agencies in the past, some modification as per the requirement has been made in various stages of investigation.

Details

Disaster Prevention and Management: An International Journal, vol. 18 no. 4
Type: Research Article
ISSN: 0965-3562

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Article
Publication date: 1 November 1996

C. Kropik and H.A. Mang

Contains a report on three‐dimensional finite element (FE) analyses of deformations and stresses resulting from the excavation of shallow underground railway tunnels…

Abstract

Contains a report on three‐dimensional finite element (FE) analyses of deformations and stresses resulting from the excavation of shallow underground railway tunnels. Multisurface elasto‐viscoplastic material models are employed for consideration of the mechanical behaviour of the soil and the shotcrete shell supporting the excavation. Both are formulated within the framework of closest point projection algorithms. For soil a cap model is used, consisting of a curved failure surface, a tension cut‐off and an elliptical cap. The latter allows consideration of the evolution of plastic strains even for the limiting case of a purely volumetric stress state. The movement of the cap is governed by a hardening law, describing the relation between the hydrostatic pressure and void ratio. The shotcrete model is a rotating crack model, taking ageing of the maturing concrete into account. It consists of a strain‐hardening Drucker‐Prager cone and three Rankine (crack) surfaces. Demonstrates the usefulness of the cap model to predict the mechanical behaviour of the soil by means of tests on remoulded, saturated clay. The model parameters of the clayey silt of Vienna, where the analysed tunnel is located, are fit to standard test results. The parameters of the shotcrete model are fit to test results published in the literature. Compares the analysis of a single‐track tunnel with the results of field measurements from sliding micrometers. Furthermore, the stresses in the shotcrete lining are examined. In view of the inhomogeneity of the material and of unavoidable deficiencies of the measurements it is fair to say that the mechanical effects resulting from the excavation of tunnels are modelled reasonably well.

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Engineering Computations, vol. 13 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 December 2001

H. Malekzadeh, D.J. Edwards and F.C. Frank

This paper describes the development of a computer finite element method (FEM) model for simulating the temporary earthwork support technique, artificial ground freezing…

Abstract

This paper describes the development of a computer finite element method (FEM) model for simulating the temporary earthwork support technique, artificial ground freezing. Specifically, ice‐wall thickness growth and ground movement (due to frost heave and thaw settlement) were evaluated with the use of the finite element software package ABAQUS. Other parameters modelled were obtained from a combination of a priori research and invaluable practitioner experience. Simulation results were then compared with measurements obtained from a live field project to assess model accuracy. Output results obtained from the FEM analyses provided demonstrable evidence of the model’s inherent ability to simulate “realistically” the effects of ground freezing analysis process.

Details

Structural Survey, vol. 19 no. 5
Type: Research Article
ISSN: 0263-080X

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Article
Publication date: 5 October 2015

Mingjing Jiang, Fang Liu, Huaning Wang and Xinxin Wang

The purpose of this paper is to present an investigation of the effect of different gravity conditions on the penetration mechanism using the two-dimensional Distinct…

Abstract

Purpose

The purpose of this paper is to present an investigation of the effect of different gravity conditions on the penetration mechanism using the two-dimensional Distinct Element Method (DEM), which ranges from high gravity used in centrifuge model tests to low gravity incurred by serial parabolic flight, with the aim of efficiently analyzing cone penetration tests on the lunar surface.

Design/methodology/approach

Seven penetration tests were numerically simulated on loose granular ground under different gravity conditions, i.e. one-sixth, one-half, one, five, ten, 15 and 20 terrestrial gravities. The effect of gravity on the mechanisms is examined with aspect to the tip resistance, deformation pattern, displacement paths, stress fields, stress paths, strain and rotation paths, and velocity fields during the penetration process.

Findings

First, under both low and high gravities, the penetration leads to high gradients of the value and direction of stresses in addition to high gradients in the velocity field near the penetrometer. In addition, the soil near the penetrometer undergoes large rotations of the principal stresses. Second, high gravity leads to a larger rotation of principal stresses and more downward particle motions than low gravity. Third, the tip resistance increases with penetration depth and gravity. Both the maximum (steady) normalized cone tip resistance and the maximum normalized mean (deviatoric) stress can be uniquely expressed by a linear equation in terms of the reciprocal of gravity.

Originality/value

This study investigates the effect of different gravity conditions on penetration mechanisms by using DEM.

Details

Engineering Computations, vol. 32 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 March 1998

Ngai Weng Chan

Malaysia is an ex‐colonial, newly‐industrialising country, with a sustained high economic growth rate averaging eight per cent GDP per annum over the past ten years…

Abstract

Malaysia is an ex‐colonial, newly‐industrialising country, with a sustained high economic growth rate averaging eight per cent GDP per annum over the past ten years. Within such a rapidly booming economy, the pace of social, economic and political change is fast, as is the pace of technological change. Other things being equal, these are the changes in which environmental hazards can be magnified. As a result of rapid economic development, physical systems are disturbed and changed. For example, the modification of the hydrological cycle due to deforestation, urbanisation, development of hill slopes and other human land use have given rise to increased risks of landslides. In recent years, the collapse of a block of luxury condominiums in Kuala Lumpur, the Genting Highland and Pos Dipang landslide tragedies as well as other landslide disasters have caused substantial loss of life and damage to property and infrastructure. Combined with intensive development of hill slopes and hill land for housing, recreation, tourism, agriculture, highway and dam construction, and other human induced land use changes, the exposure and vulnerability of human populations to landslide hazards have also increased. Other reasons, largely structural, such as persistent poverty, low residential and occupational mobility, and landlessness, manifested in illegal squatting and farming on hill slopes and foothills have also contributed to increased vulnerability of large communities to landslide hazards in many parts of the country. As Malaysia pushes ahead to meet its target of becoming a fully industrialised country by the year 2020, further environmental degradation is expected to occur. Notwithstanding other aspects of environmental degradation, the occurrence of landslide hazards is expected to become a common feature of Malaysian life.

Details

Disaster Prevention and Management: An International Journal, vol. 7 no. 1
Type: Research Article
ISSN: 0965-3562

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Article
Publication date: 2 October 2017

Hossein Nematiyan Jelodar

Analysis of designing and controlling the failure of marine structures attached to the bottom of the sea under dynamic load obtained from the sea waves is one of the main…

Abstract

Purpose

Analysis of designing and controlling the failure of marine structures attached to the bottom of the sea under dynamic load obtained from the sea waves is one of the main engineering challenges in recent years. The circumstances of the onshore marine structures have their own complexity and the difficulty due to the effect of hydrodynamic factors and dynamic responses which are dominant in the marine environment. The paper aims to discuss these issues.

Design/methodology/approach

The structure elements are composed of the metal pipe with a length of 5 m, outside diameter of 20 cm and thickness of 1.5 mm. the failure control with a safety factor of 2 indicates the absence of the above marine structure failure. It has been diagnosed to be trustworthy and reliable.

Findings

In this study, the control of marine steel structure failure with the height of 60 m under the dynamic load of the sea water waves having sinusoidal shape in the Caspian Sea has been studied and analyzed.

Originality/value

In this paper, the minimum and maximum internal force and movement in six directions of freedom were obtained for each element. To analyze and control the failure, the combination of stresses caused by static and dynamic loads has been used. According to the regulation of 10-360-AISC, the control was conducted.

Details

International Journal of Structural Integrity, vol. 8 no. 5
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 20 April 2012

Pradeep K. Rawat, C.C. Pant, P.C. Tiwari, P.D. Pant and A.K. Sharma

The main objective of the study is to identify the vulnerable areas for river‐line and flash flood hazard and its mitigation through GIS Database Management System (DBMS…

Abstract

Purpose

The main objective of the study is to identify the vulnerable areas for river‐line and flash flood hazard and its mitigation through GIS Database Management System (DBMS) of geo‐hydrometeorological parameters. The Dabka watershed constitutes a part of the Kosi Basin in the Lesser Himalaya, India in district Nainital has been selected for the case illustration.

Design/methodology/approach

The Dabka DBMS is constituted of three GIS (Geographic Information System) modules, i.e. geo‐informatics (consists of geomorphology, soils, geology and land use pattern, slope analysis, drainage density and drainage frequency), weather informatics (consists of daily, monthly and annual weather data about temperature, rainfall, humidity and evaporation) and hydro‐informatics (consist of runoff, sediment delivery, and denudation). The geo‐informatics and weather informatics modules carried out by comprehensive field work and GIS mapping than both modules used to carry out hydro‐informatics module. Through the integration and superimposing of spatial data and attribute data with their GIS layers of all these modules prepared Flood Hazard Index (FHI) to identify the level of vulnerability for flood hazards and their socio‐economic and environmental risks.

Findings

The results suggest that geo‐environmentally most stressed areas of barren land (i.e. river‐beds, flood plain, denudational hills, sites of debris flow, gullies, landslide prone areas etc.) have extreme vulnerability for flood hazard due to high rate of runoff, sediment load delivery and denudation during rainy season (i.e. respectively 84.56 l/s/km2, 78.60 t/km2 and 1.21 mm/year) whereas in geo‐environmentally least stressed dense forest areas (i.e. oak, pine and mixed forests) have low vulnerability due to low rate of stream runoff, sediment load delivery and denudation (i.e. respectively 20.67 l/s/km2, 19.50 t/km2 and 0.20 mm/year). The other frazzled geo‐environment which also found high vulnerable for flood hazard and their risks is agricultural land areas due to high rate of stream runoff, sediment load delivery and denudation rates (i.e. respectively 53.15 l/s/km2, 90.00 t/km2 and 0.92 mm/year).

Research limitations/implications

For hydro‐informatics module it is quite difficult to monitor water and sediment discharge data from each and every stream of the Himalayan terrain due the steep and rugged topography. It requires strategic planning and trained man power as well as sufficient funds; therefore representative micro‐watershed approach of varied ecosystem followed for a three years (2006‐2008) period.

Practical implications

The study will have great scientific relevance in the field of river‐line flood and flash flood hazard and its socio‐economic and environmental risks prevention and management in Himalaya and other mountainous terrain of the world.

Originality/value

This study generated primary data on hydro‐informatics and weather informatics to integrate with geo‐informatics data for flood hazard assessment and mitigation as constitutes a part of multidisciplinary project, Department of Science and Technology (D.S.T.) Government of India.

Details

Disaster Prevention and Management: An International Journal, vol. 21 no. 2
Type: Research Article
ISSN: 0965-3562

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Article
Publication date: 1 February 1992

RICARDO DOBRY and AND TANG‐TAT NG

A general overview is presented on applications of the discrete element method (DEM) to granular media. A literature survey is performed of static and dynamic simulations…

Abstract

A general overview is presented on applications of the discrete element method (DEM) to granular media. A literature survey is performed of static and dynamic simulations using random arrays of compliant particles, and forty‐two references published mostly in the last ten years are identified and categorized according to a number of relevant criteria. It is concluded that the interest in the use of the technique is rapidly increasing in the research and engineering community, with applications concentrated in soil mechanics, rock mechanics, grain flow and engineering problems. Additional studies and verifications of some numerical aspects of the DEM technique are suggested including parametric studies and comparisons. Program CONBAL‐2 (CONTACT + TRUBAL in 2D) developed by the authors based on TRUBAL created by Strack and Cundall, is described. CONBAL‐2 uses the complete Mindlin solution for the contact between two spheres and thus can be used for small strain and cyclic loading. The program is applied to study the cyclic response of uniform, medium dense to dense rounded quartz sand. Cyclic strain‐controlled loading at constant volume is applied to isotropically consolidated, random arrays of 531 spheres, using cyclic strains ranging from 10–4% to 10–1%. The calculated shear modulus, Gmax, constrained modulus, D, and Poisson's ratio at small strains are correlated with the confining pressure, the porosity of the array, and the coordination number. The calculated variations of secant modulus and damping ratio with cyclic strain compare favourably with the experimental results on sands compiled by Seed and Idriss. Finally, ‘pore water pressure buildup’ and cyclic stiffness degradation of the material with number of cycles is calculated at a cyclic strain of 10–1%, and the prediction is found to represent closely cyclic undrained experiments on sands. The existence of a threshold strain, yt ≈ 10–2%, found experimentally, is also predicted by the simulations.

Details

Engineering Computations, vol. 9 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 2 October 2017

Abdolhosein Haddad, Danial Rezazadeh Eidgahee and Hosein Naderpour

The purpose of this study is to introduce a relatively simple method of probabilistic analysis on the dimensions of gravity retaining walls which might lead to a more…

Abstract

Purpose

The purpose of this study is to introduce a relatively simple method of probabilistic analysis on the dimensions of gravity retaining walls which might lead to a more accurate understanding of failure. Considering the wall geometries in the case of allowable stress design, the probability of wall failure is not clearly defined. The available factor of safety may or may not be sufficient for the designed structure because of the inherent uncertainties in the geotechnical parameters. Moreover, two cases of correlated and uncorrelated geotechnical variables are considered to show how they affect the results.

Design/methodology/approach

This study is based on the failure and stability of gravity retaining walls which can be stated in three different modes of sliding, overturning and the foundation-bearing capacity failure. Each of these modes of failure might occur separately or simultaneously with a corresponding probability. Monte Carlo simulation and Taylor series method as two conventional methods of probability analysis are implemented, and the results of an assumed example are calculated and compared together.

Findings

The probability analysis of the failure in each mode is calculated separately and a global failure mode is introduced as the occurrence of three modes of sliding, overturning and foundation-bearing capacity failure. Results revealed that the global mode of failure can be used along with the allowable stress design to show the probability of the worst failure condition. Considering the performance and serviceability level of the retaining structure, the global failure mode can be used. Furthermore, the correlation of geotechnical variables seems to be relatively more dominant on the probability of global failure comparing to each mode of failure.

Originality/value

The introduced terminology of global mode of failure can be used to provide more information and confidence about the design of retaining structures. The resulted graphs maintain a thorough insight to choose the right dimensions based on the required level of safety.

Details

World Journal of Engineering, vol. 14 no. 5
Type: Research Article
ISSN: 1708-5284

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