Ground Improvement Case Histories (eBook)

Compaction, Grouting and Geosynthetics

Jian Chu, Buddhima Indraratna, Cholachat Rujikiatkamjorn (Autoren)

eBook Download: PDF | EPUB

2015 | 1. Auflage
796 Seiten
Elsevier Science (Verlag)
978-0-08-100699-3 (ISBN)

Infos

Written by an international group of contributors, Ground Improvement Case Histories: Compaction, Grouting and Geosynthetics provides over 700 pages of international case-histories. Each case-history provides an overview of the specific technology followed by applications, with some cases offering a comprehensive back-analysis through numerical modelling. Specific case-histories include: The Use of Alternative and Improved Construction Materials and Geosynthetics in Pavements, Case Histories of Embankments on Soft Soils and Stabilisation with Geosynthetics, Ground Improvement with Geotextile Reinforcements, Use of Geosynthetics to aid Construction over Soft Soils and Soil Improvement and Foundation Systems with Encased Columns and Reinforced Bearing Layers. - Comprehensive analysis methodsÿ using numerical modelling methods - Features over 700 pages of contributor generated case-histories from all over the world - Offers field data and clear observations based on the practical aspects of the construction procedures and treatment effectiveness

Professor Indraratna is the author of more than 500 publications, including 6 books, about 200 journal papers and 50 invited keynote and plenary lectures. His contributions through research and development towards the understanding of soft soil improvement have been incorporated by numerous organizations into their engineering practices for the design of rail and road embankments.

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Written by an international group of contributors, Ground Improvement Case Histories: Compaction, Grouting and Geosynthetics provides over 700 pages of international case-histories. Each case-history provides an overview of the specific technology followed by applications, with some cases offering a comprehensive back-analysis through numerical modelling. Specific case-histories include: The Use of Alternative and Improved Construction Materials and Geosynthetics in Pavements, Case Histories of Embankments on Soft Soils and Stabilisation with Geosynthetics, Ground Improvement with Geotextile Reinforcements, Use of Geosynthetics to aid Construction over Soft Soils and Soil Improvement and Foundation Systems with Encased Columns and Reinforced Bearing Layers. - Comprehensive analysis methods using numerical modelling methods- Features over 700 pages of contributor generated case-histories from all over the world- Offers field data and clear observations based on the practical aspects of the construction procedures and treatment effectiveness

Textauszug

Chapter 1

Ground Improvement for Mitigating Liquefaction-Induced Geotechnical Hazards

Dharma Wijewickreme1,2; Upul D. Atukorala2    1 Department of Civil Engineering, University of British Columbia, Vancouver, B.C., Canada
2 Golder Associates Ltd., Vancouver, B.C., Canada

Abstract

Liquefaction of foundation soils imposes geotechnical hazards primarily in the form of loss of bearing capacity and permanent ground deformations. Foundations in liquefiable soils need to be designed to withstand these hazards, or ground improvement measures need to be implemented to mitigate the resulting impacts. Five engineering case histories are presented where ground improvement measures were undertaken to minimize the liquefaction-induced geotechnical hazards. The project sites corresponding to the case histories are located within or in the vicinity of the Greater Vancouver region of British Columbia, which is one of the zones of highest seismic risk in Canada. Details pertaining to site seismicity and subsurface conditions together with the design philosophy are presented to provide the necessary background information for the case histories. In addition, details of the construction equipment, postground improvement performance, and structural, geotechnical, and environmental monitoring that were undertaken are presented and discussed. The case histories correspond to ground improvement carried out using vibro-replacement, compaction grouting, and deep dynamic compaction methods. The protected foundations and/or structures belong to key industrial plants, highway systems, and energy networks.

Keywords

Soil Liquefaction

Ground Improvement

Deep Dynamic Compaction

Vibro-Replacement Stone Columns

Compaction Grouting

Gravel Compaction Piles

Acknowledgments

The authors are grateful to the B.C. Ministry of Transportation, Terasen Gas Utility Ltd., and Lafarge Canada Inc. for granting permission to publish the technical information associated with the case histories.

1.1 Introduction

Frequent occurrence of devastating seismic events around the world has resulted in a remarkable increase in the public interest toward earthquake preparedness. The known potential for disruption to structures and facilities has encouraged the owners to protect their assets from earthquake hazards. The seismic evaluation/upgrading programs undertaken over the last 20 years by lifeline owners in North America and Japan serves testimony to the significance of this subject (TCLEE, 1998; Wijewickreme et al., 2005). Experience from past seismic events indicates that earthquake-induced permanent ground displacements and/or loss of bearing capacity are some key geotechnical hazards to structures located at sites underlain by liquefiable soils (O’Rourke and Hamada, 1992; MCEER, 1999). After identification of the geotechnical hazards and the resulting vulnerability of a given structure, a combination of structural retrofitting and/or geotechnical remediation (ground improvement) is often considered in the design of mitigative measures.

Historically, ground improvement has been used as a means of improving the postconstruction bearing capacity and settlement performance of soils under static loading conditions, and a variety of ground improvement techniques have evolved in the past few decades (Mitchell, 1981; Japanese Geological Society, 1998). In addition to resisting static loads, some of the ground improvement measures have been effectively used to retrofit facilities that are located within, or that have foundations supported on, liquefiable soils. These measures include dynamic deep compaction, vibro-replacement using stone columns, compaction piling, explosive compaction, and compaction grouting.

The observed performance of sites following major earthquake events—for example, 1964 Niigata (Niigata, Japan), 1995 Hyogoken Nanbu (Kobe, Japan), 1999 Kocaeli (Turkey), 2001 Nisqually (Washington state, U.S.)—indicates that the sites with improved ground had generally less susceptibility to earthquake-induced ground deformations and resulting damage than the sites that had not been densified (Mitchell et al., 1998; Hausler and Sitar, 2001; Hausler and Koelling, 2004).

Amid these ground improvement efforts, including the examination of past earthquake damage and postearthquake operations, there is a need for more documentation of approaches and illustrative case histories related to the use of ground improvement. Clearly, advances in the state of practice in seismic evaluation and retrofit of facilities require dissemination, particularly within the structural and geotechnical engineering disciplines.

With this background, and drawing from a number of case histories from Greater Vancouver, British Columbia (B.C.), Canada, this chapter illustrates several key facets and considerations in the engineering of ground improvement to mitigate liquefaction-induced geotechnical hazards. The sites of the case histories are situated within one of the zones of highest seismic risk in Canada (NBCC, 1995). The region encompasses significant areas underlain by marine, deltaic, and alluvial soil deposits, some of which are considered to be susceptible to liquefaction and large ground movements when subjected to earthquake shaking. Seismic performance of the structures and lifelines located within such weak ground conditions has been of particular concern to the region at large.

The following aspects are specifically addressed:

• Current approaches for the evaluation of seismic vulnerability, including identification and prediction of geotechnical hazard (prediction of earthquake-induced ground deformations)

• Influence of soil conditions (including key controlling parameters and features), presence of site constraints, and environmental concerns in governing the selection of the most appropriate ground improvement method

• Ground improvement schemes/configurations used in addressing typical engineering situations

• Verification testing for quality control

• Monitoring of existing facilities during adjacent ground improvement construction

Examination of case histories involving observed field performance during past earthquakes is not included in the scope of this chapter.

Because all the case histories presented herein emanate from one general geographic area, some common background information related to the Greater Vancouver region is also included in the following sections as a part of the introduction. The approaches used in the assessment of earthquake-induced geotechnical hazard, as well as the philosophy adopted in the engineering design and evaluation of seismic retrofit measures, were found to be generally applicable to all the case histories. As such, this information has also been presented concisely in this introductory section.

1.1.1 Greater Vancouver region of British Columbia

More than 2 million people live in the Greater Vancouver region of British Columbia, Canada (see Fig. 1.1 for approximate location). The region covers a triangular-shaped area of about 3000 km2 bounded by the Coast Mountains to the north, the Cascade Mountains to the south and southeast, and by the Strait of Georgia to the west. The Fraser River extends through the area and has developed a delta some 30 km long and 25 km wide.

Figure 1.1 Location plan.

Regional surficial geology

The regional surficial geology of the area has been mapped in detail by the Geological Survey of Canada (Armstrong, 1976, 1977; Armstrong and Hicock, 1976a,b). Glaciers repeatedly covered the area during the Pleistocene era, resulting in deposition of relatively competent glacial till and proglacial sands. Since the retreat of the last glaciers, more recent sediments (Holocene or postglacial deposits) associated with the Fraser River and other watercourses have been laid down. Channel fill and flood-plain deposits cover almost all of the low-lying areas within the Greater Vancouver region. These recent sediments are relatively unconsolidated and are judged to provide a medium for ground motion amplification and also considered susceptible to liquefaction when subjected to earthquake shaking.

Regional seismicity

The seismicity in the area results from the thrusting of the offshore Juan de Fuca plate beneath the continental North American plate. The subduction zone is located off the west coast of Vancouver Island. There are three distinct sources of earthquakes: (1) relatively shallow crustal earthquakes (depths in the order of 20 km); (2) deeper intraplate earthquakes (~ 60 km deep) within the subducted plate; and (3) very large interplate earthquakes, also referred to as megathrust or subduction earthquakes. Earthquakes within the first two categories (crustal and intraplate) have been recorded at regular intervals over the last several decades in the area. The largest recent earthquakes are those near Campbell River, B.C. in 1946 (M = 7.3), near Olympia, Washington in 1949 (M = 7.1), near Seattle/Tacoma, Washington in 1965 (M = 6.5), and near...

Produkt-Details

• Erscheint lt. Verlag: 16.6.2015
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geologie
• Themenwelt: Technik ► Bauwesen
• ISBN-10: 0-08-100699-3 / 0081006993
• ISBN-13: 978-0-08-100699-3 / 9780081006993