The following are summaries of papers published in other parts of ICE Proceedings during 2006 that readers of Geotechnical Engineering may find of interest. Summaries of all papers in ICE journals are freely available and fully searchable at the ‘journals on-line’ section of the ICE website. See www.ice.org.uk/journals for details.
What lies beneath: surveying the Thames at Woolwich
J. Lenham, V. Meyer, H. Edmonds, D. Harris, R. Mortimore, J. Reynolds and M. Black
Proceedings of the Institution of Civil Engineers—Civil Engineering, 159, No. 1, February, 32–41
Line 1 of the Crossrail project is planned to cross the River Thames via twin tunnels at Woolwich in east London. This paper reports on the fascinating investigation into the riverbed of Woolwich Reach, involving integration of a wide range of data from historical, geophysical and borehole sources. It illustrates how combining detailed desk studies and focused borehole investigations with over-water seismic, sonar and magnetic gradiometer surveys can assist civil engineers in the design of major structures within historic urban and tidal river environments.
Are you sure of your footing?
S. Edmonds
Proceedings of the Institution of Civil Engineers—Civil Engineering, 159, No. 2, May, 52
The UK courts have served a stark warning to civil engineers about the dangers of using assumptions about ground conditions. Shareena Edmonds of UK law firm Pinsent Masons says engineers must ensure any preliminary design assumptions are verified.
Acute decompression illness in UK tunnelling
D. Lamont and R. Booth
Proceedings of the Institution of Civil Engineers—Civil Engineering, 159, No. 4, November, 185–191
Civil engineers have used compressed air to stabilise wet ground for over 150 years and continue to do so. But since 2001, compressed-air workers in the UK can no longer decompress on air alone—it now has to be done with the aid of oxygen. Despite one of the strictest regulatory environments in the world, Britain's construction industry recorded 428 cases of decompression illness between 1984 and 2002, leading to air-only decompression being banned. This paper provides an analysis of the UK's uniquely comprehensive database of compressed air exposure and decompression illness records which led to the ban. It provides a benchmark for assessing the effectiveness of oxygen decompression as well as informing other countries considering making the change.
Trenchless technology: a modern solution for clean-flowing cities
D. Downey
Proceedings of the Institution of Civil Engineers—Civil Engineering, 159, Special Issue 1—Water worldwide: principles and practicalities, May, 26–30
The Indian Government is currently using trenchless technology for construction and rehabilitation of sewers in New Delhi as part of a massive programme to clean up the Yamuna river. The work is of a similar scale and concept to Joseph Bazalgette's nineteenth century London sewerage project—the main difference being that modern urban societies, whether rich or poor, can no longer afford the disruption of major open-cut construction. This paper reports on the huge take-up of trenchless techniques in both the developing and developed world, and of its increasingly vital role in cost-effective provision and renovation of water and sewage networks in today's congested cities.
Geohazard risk management for infrastructure projects
M. Free, S. Anderson, C. Milloy and J. Mian
Proceedings of the Institution of Civil Engineers—Civil Engineering, 159, Special Issue 2—Risk: facing the reality, November, 28–34
This paper presents generic guidance for construction professionals for the assessment of geological-related hazards and risks for infrastructure projects. The risks presented by such hazards to a project are dependent upon their potential size and impact. Drawing on practical experience of civil engineering projects in the UK and worldwide, the authors show that, through a carefully planned risk management framework, the potential impact of uncertain events related to geohazards can be identified, appropriately investigated and mitigated. The corresponding reduction in uncertainty provides improved control over both costs and programme to the advantage of all parties involved.
Sustainable landslide risk reduction in poorer countries
M. G. Anderson and L. Holcombe
Proceedings of the Institution of Civil Engineers—Engineering Sustainability, 159, No. 1, March, 23–30
In developing countries many houses are built by the most vulnerable persons in unplanned settlements on land that is marginal in construction terms and often subject to high landslide risk. This paper outlines a low-cost, community-based approach to landslide risk reduction undertaken in St Lucia, West Indies. The process of establishing a Government management team integrated with joint community implementation is described. Three key elements comprising a mapping methodology for landslide risk, identification of dominant slope instability controls and implementation of low-cost sustainable measures are described. The successful pilot project demonstrates the feasibility of such a low-cost approach to landslide risk reduction and offers a major step forward in establishing appropriate preventative measures for minimising landslide risk in vulnerable communities.
Soft coastal cliff: understanding and managing retreat
B. E. Waters and H. R. Payne
Proceedings of the Institution of Civil Engineers—Maritime Engineering, 159, No. 2, June, 77–79
This article reports on a seminar held at the Institution of Civil Engineers in May 2004. This, and a previous meeting in 2002, stemmed from Government-funded research into soft cliff erosion. While the previous meeting dealt with the theory, this one dealt with more practical issues by way of four papers. Dr Neil Dixon described work carried out on landsliding of unprotected London Clay cliffs at Warden Point on the Isle of Sheppey. Dr Alan Clark described practical examples of engineering schemes at Lyme Regis and at Castlehaven, Niton and the Military Road on the Isle of Wight. The final two papers described aspects of work on the Norfolk coast: Dr Mike Walkden presented a process-based regional model of shoreline recession while Peter Frew of North Norfolk District Council described the problems faced by his authority in managing a retreating coastline where property is under threat.
Membrane action in ground-bearing concrete slabs
J. R. Eyre
Proceedings of the Institution of Civil Engineers—Structures and Buildings, 159, No. 3, June, 153–163
Loading a ground-bearing slab at a location distant from the slab edge will inevitably incur membrane action. This membrane action can result in considerable enhancement of maximum load-carrying capacities. Although the enhancement may not be as great as for suspended slabs laterally restrained by their supports, it is nevertheless still substantial. Now that slabs are often continuously cast over large areas there may be considerable benefit from taking advantage of this load-carrying enhancement. The present paper presents a theoretical study of the effects of membrane action in these circumstances. It suggests that the inability of previous theoretical models to reproduce the failure loads from tests on slabs or to account for the considerable scatter in results may be the result of ignoring membrane action. An upper-bound plastic analysis is used to shed new light on the evolution of mechanisms and shows that, depending on stiffness, slabs on grade reach collapse loads with one of two modes. Either collapse takes place in flexure at a peak of the non-linear load–deflection behaviour or by punching through provoked by a through-depth crack at the perimeter of the loaded area. With pure flexure plastic methods, past analyses have failed to provide a non-trivial estimate of the size of the failing mechanism. Inclusion of membrane action is shown to predict the radius of the probable preferred collapse mechanism. A parametric study is provided, but further research work providing experimental scrutiny and convenient design routines is needed before this is of immediate benefit to the practitioner.
Using waste to reduce slope erosion on road embankments
J. de Oña and F. Osorio
Proceedings of the Institution of Civil Engineers—Transport, 159, No. 1, February, 15–24
Urban waste may be used to reduce slope erosion of highway embankments. Whereas different kinds of compost have been tested in the USA for highway revegetation, sewage sludge has been used only for agricultural purposes. This paper presents the results of research carried out in order to study the viability of the application of sewage sludge compared with compost. Test areas measuring 4 m × 5 m were constructed on a new highway embankment with 2:1 and 3:2 side slopes in the south of Spain. Crop cover and erosion were evaluated for plots with application of three dosages of compost and three dosages of sludge. Also, the costs of the proposed application are analysed. This treatment costs, on average, 0·24% of the budget for new roads infrastructure, and reduces soil loss by up to 30% on average. Based on these results, compost and sludge can be successfully used to reduce slope erosion on highway embankments. However, standards and specifications are required for their routine application.
Rail ballast: conclusions from a historical perspective
P. Claisse and C. Calla
Proceedings of the Institution of Civil Engineers—Transport, 159, No. 2, May, 69–74
Although it is now universally accepted that good-quality hard angular stone of nominal size 40–50 mm is the best material for ballast, historically track has been for longer on non-stone ballast than on stone ballast. Even the stone ballast specified up until the 1980s was of a smaller average size than present ballast. Research into the two-layered ballast system and a study of development of ballast specification from the early 1900s suggests that current ballast specifications should be changed to ballast of smaller size. This would: cause substantial reduction in maintenance requirements for ballasted railway track; reduce track noise levels; provide better ride quality; and increase ballast life.
Investigation of railway track subgrade. Part 2: Case study
M. J. Brough, G. Ghataora, A. B. Stirling, K. B. Madelin, C. D. F. Rogers and D. N. Chapman
Proceedings of the Institution of Civil Engineers—Transport, 159, No. 2, May, 83–92
Track quality indices, continued track component performance and subsequent maintenance are highly dependent upon trackbed stiffness. This is exacerbated by consolidation and settlement of subgrade and the subsequent differential track geometry. Consequently, any site investigation to diagnose the causes of track geometry deterioration should include an assessment of stiffness parameters. In addition to stiffness assessment, a trackbed investigation should comprise a full assessment of ballast, sub-ballast and subgrade condition. If information about any of these layers is omitted, a complete diagnosis is not feasible, and consequently appropriate ground improvement schemes may not be implemented. Test devices suitable for trackbed investigation to assess the causes of track settlement have been identified in a previous paper in this series. This paper summarises the staged trackbed investigation performed at a site historically requiring high maintenance, suspected as being caused by poor subgrade. The paper concludes with a diagnosis of the site and suggested remedial schemes deemed suitable for generic treatment of poor subgrade sites.
Predicting long-term soaked CBR of gypsiferous subgrade soils
S. S. Razouki and D. K. Kuttah
Proceedings of the Institution of Civil Engineers—Transport, 159, No. 3, August, 135–140
Thirty-two laboratory California Bearing Ratio (CBR) tests were carried out on a CH gypsiferous subgrade soil with an initial gypsum content of 34%. The soil samples were prepared according to ASTMD 1883-99 at 95% of the maximum modified AASHTO dry density. For each 40 lb (178 N) and 70 lb (311·5N) surcharge load, eight pairs of CBR samples were prepared, and soaked for periods of 0, 4, 7, 15, 30, 60, 120 and 180 days respectively. To develop a general empirical formula for predicting long-term soaked CBR from unsoaked CBR, use was made of available results on CH soil with a gypsum content of 15%, on granular gypsiferous soils of the SW-SM group with a gypsum content of 64%, and on SM soils with gypsum contents of 34% and 61%. The empirical equation developed in this paper enables the soaked CBR to be determined from the unsoaked CBR for all types of gypsiferous soil and for any surcharge load and soaking period. The equation's validity was examined using six different gypsiferous soils (eight case studies) including both granular and fine-grained soils. This paper also shows the invalidity of Fekpe's empirical equation in modeling the long-term behaviour of gypsiferous soils.
Use of recycled aggregates for cementitious backfill
G. S. Ghataora, I. Alobaidi, E. Faragher and S. Grant
Proceedings of the Institution of Civil Engineers—Waste and Resource Management, 159, No. 1, February, 23–28
Laboratory and field trials were conducted to assess the performance of cementitious backfill material for reinstatement of trenches and excavations in roads. Backfill material was produced using recycled granular aggregates, pulverised fuel ash and cement. A conventional compacted recycled granular material was used as a control to compare the performance of cementitious backfill. The results showed that recycled granular materials, with a particle size ranging from 5 to 38 mm, could be used to form a cementitious backfill with strengths that comply with the Highway Authorities and Utilities Committee's Specifications for the Reinstatement of Openings in Highways (SROH) for cementitious backfill. This backfill was prepared using conventional mixing plant and was straightforward to install on site. Settlements of trenches with granular backfill up to 1 year of monitoring were found to be higher than the corresponding ones with cementitious backfill. However, settlements for both types of backfill were within the limits of the SROH and did not require any subsequent intervention measures. Although the stiffness of the granular backfill was initially lower than that of the surrounding ground, within a year it had increased to the same level. The cementitious backfill was stiffer than the adjacent ground, but no detrimental effects were observed over the period of monitoring.
Analysing river bank seepage with a synthetic design hydrograph
I. Butera and M. G. Tanda
Proceedings of the Institution of Civil Engineers—Water Management, 159, No. 2, June, 119–127
The design conditions of a river embankment are usually computed in a steady state, in a similar way to those due to the maximum river level of an assigned return period. The seepage analysis of the water pressure that stresses the embankment, with an increase in the risk of failure owing to both static instability and piping effects, results in an overly prudent evaluation that can be recognised as a non-economic design. The seepage steady state condition is, however, rarely verified in most river embankments, owing to the limited duration of floods and the poor conductivity of the soils that are usually adopted to construct river banks. Attempts to design in an unsteady regime have been made in recent years by means of mathematical models, but the selection of a design hydrograph in a river remains an ongoing problem. Over recent years, a new procedure for the identification of an efficient synthetic design hydrograph (SDH), with an assigned return period, has been developed by Maione and co-workers. This procedure has been successfully applied in the design of flood control reservoirs and in the evaluation of flood routing in rivers with large flood plain storage. In the current paper this SDH is applied in the analysis of seepage through a river embankment, as an attempt to design the river embankment in an unsteady regime; the SDHs of a given return period are applied to a levee with a simple geometry using a semi-analytical model and the main hydraulic quantities (maximum water level, time of maximum, etc.) of the seepage through the soil can be determined. All the real floods are then used as input for the model and the main hydraulic quantities of each flood are determined. The reliability of the design flood methodology has been tested by way of a comparison between the outcomes from the SDHs and the application of real floods.
