No abstract

The US practice of ground improvement is divided into six main categories: densification, consolidation, reinforcement, chemical treatment, thermal stabilization and biotechnical stabilization. Densification, which applies mainly to granular soils, includes vibrocompaction, dynamic compaction, blasting and compaction grouting. Consolidation is basically achieved through preloading and the use of vertical drains. Soil reinforcement is divided into two groups: those involving compacted fill such as mechanically stabilized backfill systems, and those applied in situ such as soil nailing, element walls, micropiles and stone columns. The chemical treatment methods discussed are those applied at depth such as permeation grouting, jet grouting, deep soil mixing and lime columns. Thermal stabilization is covered through ground freezing and its use in urban construction. Finally, biotechnical stabilization, which is one of the latest developments in the field, is briefly presented. Discussed in the paper are the applications, advantages, limitations, design and construction aspects of each ground improvement method as well as the durability and long-term performance of the improved ground. The use of ground improvement in environmental engineering is briefly highlighted.

The use of ground improvement in transportation projects is studied through its application to the four main systems of transportation: surface, underground, marine and air. The ground improvement methods applied involve densification, consolidation, weight reduction, reinforcement, chemical treatment, thermal stabilisation and biotechnical stabilisation. Improvement of the weak soils provided increased bearing capacity, settlement control, lateral stability, environmental control and liquefaction resistance. Included in the paper are visions of ancient builders as well as modern innovative applications of a variety of ground improvement techniques. Nous étudions l'utilisation des améliorations de sol dans la construction d'infrastructures de transport, en l'appliquant aux quatre moyens de transport principaux: surface, sous terre, par mer, par air. Les méthodes d'amélioration des sols appliquées sont la densification, la consolidation, l'allégement, le renfort, le traitement chimique, la stabilisation thermique et la stabilisation biotechnique. L'amélioration des sols faibles leur donne une capacité porteuse accrue, un contrôle du tassement, une stabilisation latérale, un contrôle environnemental et une résistance à la liquéfaction. Dans cet exposé, nous rappelons aussi les techniques des anciens bâtisseurs et certaines applications modernes novatrices d'une variété de techniques d'amélioration.

Infrastructure safety and security is a growing area of engineering analysis. Dams and levees need to be considered as part of these critical infrastructure assessments. In the United States alone, there are over 80,000 dams and 100,000 miles of levees. Over 26,000 of these dams are classified as high or significant hazard. A study has recently been undertaken with the goal of expanding blast security assessments for modeling the impacts of explosions to include analysis of embankment dams and levees. Specific aims of the study include developing reasonably accurate models to assess localized, shallow impacts and developing methods to assess global stability impacts. Assessing these structures requires a unique combination of understating of blast impacts, soil modelling under high energy dynamic loading, embankment dam failure modes, and conventional geotechnical slope stability. A trial dam section was developed and possible failure mechanisms due to blast impacts were determined. Published numerical soil models, developed and validated for land mine analyses, were evaluated with regard to typical soil properties of embankment dam materials. An applicable soil model was selected, and the numerical trial dam model was analysed for an explosion on the crest. The results were assessed using conventional geotechnical engineering software and engineering judgment. A step-by-step procedure for assessing the impacts of explosions on embankment dams has been developed, and a simplified chart for assessing localized breach potential have been developed. Areas for further study and validation are also identified. The work combines research from military applications with state-of-the-art infrastructure security analyses and conventional geotechnical engineering evaluations.

Application of the ground improvement methods discussed in part 1 is demonstrated through 12 case studies involving a variety of techniques, ground conditions and applications of the completed facilities. A combination of ground improvement methods is used in some cases. The design and construction issues of the methods used are highlighted, together with the benefits derived from their application. A special emphasis is placed on the selection of an appropriate ground improvement method, or a combination of methods, for each case application.