ICE - Institution of Civil Engineers - Virtual Library

Ground-related factors have often been the cause of significant time and cost overruns on both large and small construction projects. The traditional method of controlling such risks has been through the use of thorough ground investigation and competent geotechnical design, aiming to produce a robust scheme, well-matched to the expected ground conditions. This paper reanalyses data collected over the past two decades and suggests that, particularly in view of rapidly evolving methods of construction procurement, a new risk-based approach is needed. Key elements of this approach are outlined.

The general principles of lifeline engineering are discussed and applications are illustrated with reference to pipeline networks. Key research findings are summarised regarding the effects of utility construction on existing pipelines, advanced backfilling methods and materials, and soil-structure interaction of polyethylene pipelines. Pipeline behaviour during earthquakes is reviewed with respect to the effects of permanent and transient ground deformation. Pipeline system performance is addressed in light of geographic information systems (GIS) and the observed behaviour and analysis of large networks during recent severe earthquakes.

Many cities are tackling their urban congestion problems by utilising underground space and developing or expanding underground railways or metros. This paper presents metro projects currently being constructed in four major world cities: Los Angeles, Copenhagen, Bangkok and Toronto. An overview of each project is presented together with illustrations of the tunnelling process and station development. The major design issues common to all the projects were settlement and groundwater control. Other issues specific to particular projects, such as earthquake allowance or maintenance of traffic flow, are also discussed. The aim of the paper is to show the infrastructure developing below our cities and briefly outline some of the complex geotechnical problems faced in the construction of these essential facilities.

Finite-element or finite-difference methods are commonly used in geomechanics to model the response of soil or rock at an engineering site. These methods assume that the material is a continuum (although known discontinuities can be included explicitly). There are two drawbacks with continuum methods. Firstly, an appropriate stress-strain law for the material may not exist, or the law may be excessively complicated with many obscure parameters. Secondly, the natural development of cracks and rupture surfaces is not well-handled by continuum approaches. It is suggested that the future trend for numerical modelling in soil and rock may consist of the replacement of continuum methods by particle methods. Assemblies of discrete particles (bonded together to represent rock, and unbonded to represent soil) capture the complicated behaviour of actual material with simple assumptions and few parameters at the micro level. Complex overall behaviour arises as an emergent property of the assembly. The application of particle methods to large-scale problems is currently difficult or impossible because of high computational demands. It is shown that such applications should be feasible within ten years, and certainly within 20 years. Examples are given of the simulation of granular material and rock by particle methods.

Early approaches to land reclamation involved bulk removal of contaminated media using traditional geotechnical engineering technologies such as soil excavation and groundwater extraction. While these methods rely on readily available equipment and can be applied to a broad spectrum of contaminants, they are less than ideal. In the case of soil excavation, the approach is effective, but treatment is costly. Depending on the alternatives available, this approach may do little more than move the contamination from one site to another. With respect to groundwater extraction, the approach has proven to be very inefficient in many settings and requires extremely long time frames to complete. As a consequence, new technologies have emerged which attempt to exploit the chemical properties of contaminants to facilitate removal or destruction. The more developed of the new approaches are characterised in this paper, including how they work, how they are applied, potential limitations, and results from specific applications. While many of these new technologies have improved our ability to reclaim the land, significant limitations still leave undesirable results in terms of residual contamination and remedy cost. There is a need to continue improving and developing new technologies, especially those related to non-volatile contaminants and dense, free-phase liquids.