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Numerical analysis of blast-induced liquefaction of soil

Numerical analysis of blast-induced liquefaction of soil

Zhongqi Wang a ,Yong Lu

b,*

,Chunhua Bai

a

a

The State Key Laboratory of Explosion Science &Technology,Beijing Institute of Technology,Beijing 100081,China

b

Institute for Infrastructure and Environment,School of Engineering and Electronics,University of Edinburgh,Edinburgh EH93JL,UK

Received 21September 2006;received in revised form 20March 2007;accepted 27April 2007

Available online 18June 2007

Abstract

Soil has complicated properties that render the finite element modeling of blast-induced liquefaction very difficult.Recently,a numer-ical three-phase soil model has been proposed by the authors.This model contains all necessary elements for describing complex responses including the change of pore water pressure and degradation of the soil skeleton when subjected to extreme loading such as an explosion,and hence allows for the analysis and prediction of the liquefaction induced by explosion in the soil.In this paper,the three-phase model is applied to simulate the soil liquefaction.An overview of the three-phase soil model is provided first.The model is then employed to simulate physical experiments on the compressive behaviour of undrained soils under quasi-static and shock loading,respectively.Details about the porewater pressure and the effective stress on the soil skeleton are obtained from the numerical analysis and they compare well with the experimental data.An experimental case involving underwater explosion and liquefaction of a sand bed underneath is also analyzed using a coupled simulation with the three-phase soil model.The results show that the liquefaction zone can be simulated favourably.The effects of different shock loading on soil response and the assessment of the soil liquefaction based on the numerical results are discussed.

Ó2007Elsevier Ltd.All rights reserved.

Keywords:Soil;Liquefaction;Three-phase soil model;Numerical simulation;Blast wave

1.Introduction

In geotechnical engineering,concerns over the undrained compressive behaviour of soil are often associ-ated with earthquake loading and the potential of liquefac-tion.In recent years,interests are also growing in a phenomenon known as blast-induced liquefaction because of relevant civilian and military applications.For example,explosive and surface impacting loads can be used to induce a liquefaction condition to increase the density of loose soils (such as granular deposits and fills).On the other hand,explosion-induced liquefaction may cause fail-ure of man-made structures and natural slopes.An explo-sion detonated in or above a soil layer which has a high liquefaction potential could result in damages dispropor-tionate to the energy released [1].A good understanding of blast-induced liquefaction mechanism of soils is impor-tant in dealing with the above situations.

Earthquake-induced soil liquefaction has been a subject of extensive study over the last several decades [2,3].But there are important differences between blast-induced and earthquake-induced soil liquefaction.Generally,earth-quake-induced liquefaction is deemed to result from shear waves that propagate vertically toward the surface,while the predominant ground motions are in the horizontal plane.The acceleration time histories are oscillatory in nat-ure,usually running through many cycles and having peri-ods on the order of one http://www.doczj.com/doc/4da647160b4e767f5acfcee9.html paring to blast or shock loading,the earthquake peak accelerations are low,generally <1.0g.The blast-induced liquefaction tends to be far more complicated.The peak value of the loading is very large,but the loading period is very short.Besides,the shear and compression waves both become importan
t in the soil response under rapid loading.

Earthquake-induced soil liquefaction has been a subject of extensive study over the last several decades [2,3].But there are important differences between blast-induced and earthquake-induced soil liquefaction.Generally,earth-quake-induced liquefaction is deemed to result from shear waves that propagate vertically toward the surface,while the predominant ground motions are in the horizontal plane.The acceleration time histories are oscillatory in nat-ure,usually running through many cycles and having peri-ods on the order of one http://www.doczj.com/doc/4da647160b4e767f5acfcee9.html paring to blast or shock loading,the earthquake peak accelerations are low,generally <1.0g.The blast-induced liquefaction tends to be far more complicated.The peak value of the loading is very large,but the loading period is very short.Besides,the shear and compression waves both become important in the soil response under rapid loading.

0266-352X/$-see front matter Ó2007Elsevier Ltd.All rights reserved.doi:10.1016/http://www.doczj.com/doc/4da647160b4e767f5acfcee9.html pgeo.2007.04.006

*

Corresponding author.Tel.:+44(0)1316519052;fax:+44(0)1316506781.

E-mail address:Yong.Lu@ed.ac.uk (Y.Lu)http://www.doczj.com/doc/4da647160b4e767f5acfcee9.html /locate/compgeo

Available online at http://www.doczj.com/doc/4da647160b4e767f5acfcee9.html

Computers and Geotechnics 35(2008)

Numerical analysis of blast-induced liquefaction of soil

Numerical analysis of blast-induced liquefaction of soil

196–209

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