Discussion

by Tony Kerr, Martin Lowson and Austin Smith (May 2014)

I was very pleased to learn from Kerr et al. (2014) that the Ultra Global PRT system has been successfully installed at Heathrow. As a member of Arup's Cardiff office I worked with co-author Martin Lowson and his team some 14 years ago in developing proposals to serve Cardiff Bay and the city centre. This would have been the first operational application of the system, but unfortunately funding was removed. I note that the only current application – Heathrow – is within a controlled environment. One concern we always had at Cardiff was the potential vulnerability of the track to trespass and vandalism when passing through the public domain. I wonder if this matter has been satisfactorily resolved so that more widespread use can be made of this excellent concept.

The question of vandalism risk is common to all automated public transit systems.

In an urban application the guideway is likely to be about 5 m above public spaces (roads, footpaths, open space) and this height, together with the safety fence, reduces the opportunity for vandalism to impact on operations. Furthermore, the track is under constant observation from trackside closed-circuit television and any change to the operating conditions would be recognised and dealt with. It is recognised that grade-running operations present a risk which has been tested at Heathrow, where the track is fenced alongside a public road. To date no incidents of vandalism have been observed.

Kerr et al. (2014) emphasise the need for dimensional accuracy and avoidance of ‘bumps'. Heathrow is notorious for difficulties when there is snow, so how is the effect of snow or ice build-up on the pod track avoided – either of which could be expected to disturb the dimensional accuracy? And how is wheel slippage due to ice or snow on the track gradients avoided?

In addition, what arrangements are in place for recharging pod batteries and what is the frequency of recharging events?

The approach to snow and ice at Heathrow is to manage the guideway conditions, preventing the build-up of snow and ice and hence any detrimental effects to system operation, including wheel slippage. This is achieved by dispensing de-icing fluid in areas that are susceptible as a precautionary measure when ice or snow are forecast and by regular application of de-icing fluid in the event of snowfall and during periods of icing.

The fluid is dispensed by a specialist snow and ice management vehicle that can run automatically among the passenger vehicle fleet and return to the depot for replenishment of fluid. In periods of very heavy snow, a number of pre-prepared passenger vehicles can be quickly converted to secondary snow and ice management vehicles to increase capability. Heathrow's pods: how vulnerable are they to vandals, snow and dead batteries?

Regarding battery charging, as the vehicles are light and travel at relatively low speed (up to 40 km/h), power requirements are low. As well as providing major sustainability benefits, this means that opportunity recharging at the stations can be used, while picking up and dropping off passengers or in queue lanes fitted with chargers. Having to store less charge on the vehicle means that the battery pack weighs only around 5% of gross weight compared to up to 50% of the gross weight of many other battery-powered electric vehicles.

by Stephanie Neath, Rod Hulse and Andy Codd (May 2014)

As reported by Neath et al. (2014), Gatwick airport covers a very large area in plan. Building information modelling (BIM) has been advocated for complex structures occupying relatively small areas of land, and it is interesting to see the principles applied to one where mapping, which allows for earth curvature, is normally required as opposed to a simple and local three-dimensional Cartesian coordinate system. Was the use of the Ordnance Survey's mapping system considered in this case?

The point made in section 6.8 on buried services avoidance was most encouraging. What is the effect upon liability and the disclaimers one usually sees on utility plans? In other words, will those who laid and recorded the services under this system now be responsible if the plans are wrong? Is a BIM record therefore seen as superior in some way?Gatwick airport: how accurate and permanent are the building information modelling records?

One of the most valuable aspects of BIM seems to be the way the records of what has been built might be understood easily. This is great for those who operate the project in the future, or in times of crisis or emergencies of some sort, but has consideration been given to ensuring that all the valuable data recorded today will not become unreadable?

Gatwick uses both a local ‘airport' coordinate system, which orthographically rectifies the mapping, as well as Ordnance Survey National Grid. A mathematical transformation is used to rotate and account for the earth's curvature, effectively flipping the mapping between the two systems.

Gatwick is looking to take joint responsibility for the accuracy of the data it holds on buried services. Working in this collaborative way can mutually increase the accuracy of the data Gatwick holds, and the data held about Gatwick.

Gatwick will however continue to push its suppliers to ensure the validity of the data handed over by rigorous review. At the same time Gatwick will improve the accuracy of the data provided to them at the inception of a project. Gatwick is also looking to change the current process from marking up drawings on site to introduction of cloud-based solutions to capture data in various formats and hence allow a more immediate review and/or update of its data.

The authors view a BIM record as being a more advanced asset record, based on the amalgamation of disparate sources of information into more of a ‘one-stop shop'.

Gatwick ensures that the technology used to store and view these records is capable of reading all the varying formats of data that it holds. Future-proofing of its data is a major consideration in any technology decision that is made.

Future users also need to be able to see the history of what data were used, where they came from, how accurate they are, what method was used to determine the accuracy and so on. This must be documented to avoid falling back into the cycle of constantly repeating surveys because of uncertainty about the validity and accuracy of the asset records.

by Tatamangalam Ananthakumar and Karath Jayesh (February 2014)

Can Ananthakumar and Jayesh (2014) provide further information about the form of contract, outturn cost, cyclone insurance, use of project management consultants and environmental targets?

The contract was a Fidic Conditions of Contract for Plant and Design-Build (Yellow Book; Fidic, 1999). Though there were many hurdles, the project was completed within the budget mainly because of timely completion. All construction works in the Kattupalli yard were insured through the contractor's all-risk policy and damage caused by cyclones was fairly reimbursed. BMT Consultants was also responsible for the cost monitoring of port works, while STUP Consultants and Lloyds Register were involved in the ship lift and shipyard construction as third-party quality consultant and certification agency respectively. Environmental standards were set during the project inception stage as per statutory requirements, and these are being monitored continuously and maintained at satisfactory levels. Kattupalli port breakwater: cyclone damage was covered in the contractor's all-risk policy

by Akira Inokuma and Daisuke Nagayama (November 2013)

Could Inokuma and Nagayama (2013) comment on the extent of any public consultation on the choice of the Fukushima plant sites? The relevance to the UK is that one of the six sites chosen for new nuclear power plants, Bradwell-on-Sea, sits near the fault zone of the most damaging earthquake in the UK's recorded history, in 1884. The chance of flooding seems high, not due to a tsunami but rather due to small sea surges breaching the seismically weak earth banks defending the low-lying site. If the contamination and exclusion zones at Fukushima were overlaid on Bradwell, they would extend across the Thames estuary and into central London (less than 80 km away) where much of the UK's economic activity is based. The risk, expressed as a multiple of these factors, seems comparable to that of Fukushima. There has been no public enquiry on the choice of site, and consideration of seismicity has been excluded from some of the studies commissioned to justify the site. Fukushima contamination zone would extend to London if similar flood damage happened at Bradwell

Unfortunately the authors are unable to comment on the extent of public consultation on the choice of the Fukushima plant sites. The judgment on nuclear power sites depends on politics, economics and social values as much as science and technology. For further information the contributor is referred to The Official Report of the Fukushima Nuclear Accident Independent Investigation Commission (National Diet of Japan, 2011).

by Mario Riccio, Mangos Baroni and Marcio Almedia (November 2013 special issue)

The compaction grouting technique adopted by Riccio et al. (2013) does not always give such good results in soft soils. A couple of years ago the City of Rio de Janeiro embarked on a project to improve poor ground conditions around the Rodrigo de Freitas lagoon in the heart of Rio. The area has a history of large settlements affecting the park facilities at this site. Compaction grouting was selected and, as the authors and most geotechnical engineers in Rio are aware, the results were unsuccessful – the park has already settled some 400 mm to date. Based on overwhelming evidence of this technique's limitations in Brazil and elsewhere, I no longer use it for soft soils.

The technique reported in the paper is not compaction grouting as mentioned in the discussion, but involves the combined use of grouted columns with prefabricated vertical drains.

The combined use of columns, including grouted columns, with prefabricated vertical drains to support embankments built on soft soils deposits is not recent. Xu et al. (2006) proposed the use of deep-mixed columns to improve soft soils combined with prefabricated vertical drains. A similar method was proposed by Liu et al. (2008), combining dry jet-mixed columns with prefabricated vertical drains to accelerate dissipation of excess pore water pressure induced by jet-mixing. Han (2012) reported the use of many kinds of columns combined with prefabricated vertical drains in situations involving soft soils. These included sand-compaction piles, stone columns, deep-mix columns, vibro-concrete columns and cement–fly ash–gravel columns as well as grouted columns. Athlete's Park in Rio de Janeiro was stabilised with grouted columns and vertical drains, not just compaction grouting

In the case of the Rodrigo de Freitas lagoon, the technique was incorrectly used (Almeida et al., 2013). The columns did not reach the strong soil strata as column injection stopped at the middle of the soft soil layer.