Holdfast Training Services Trial Blog

Temporary works for engineers course

This week I attended the Laing O’Rourke Temporary Works for Engineers course. I thought I would make some reflections on the course by considering its relevance to the Royal Engineers and the role of engineers on site in solving temporary works challenges. I recently said I would avoid text heavy blogs so I am already breaking my own rule; therefore I have stolen some pictures from Google to break it up!

I have uploaded the pre-course assessment as a general level of expectation of the knowledge of the engineers prior to attendance.

TWFE pre course work

The course was run by the head of the Laing O’Rourke Temporary Works office, Kit Yardley, supported by their senior geotechnical engineer, Keith Miller. The target audience for the course was civil engineering and building graduates who had gained significant site experience (therefore about 5 years since graduation). The aim of the course was “to give participants a working knowledge of temporary works, group procedures, use of the Laing O’Rourke precast assembly manual and the use of current EN/BS standards and guidance in the industry”. The course achieved this aim and effectively covered content within the PET (C) structures, foundations, applied structures modules condensed into only 3 days with a fairly healthy A4 folder to take away.

Course content – PET officers are well prepared technically.

What is the safe depth of an unsupported excavation…

The participants were not required to take in all of the subject matter but become more aware of risks of working with, and designing, temporary elements. The course content included cranes and hoists, soils, excavation support, formwork, falsework, backpropping, concrete pressure, scaffolding, loading platforms, pile/crane mats and many other temporary works structures. I found it comforting that the majority of the theory behind each of the topics was covered on the PET course, where others clearly had not recently been refreshed in modules I cited above. Most of the participants completed the pre-course work getting all of the answers correct, although a couple struggled with question 8.

Experience required.

The area which was unfamiliar to me was the understanding of proprietary systems that are used for falsework and the Laing O’Rourke precast system. While this sort of knowledge can be gained now on site, it is somewhat symptomatic of the imbalance of site experience PET officers have compared to their technical understanding gained on Phase 1. I believe it is better to have a technical understanding which is then enhanced through gaining practical experience on site.

Temporary works course for military engineers.

I would strongly argue that with a little tweaking of specific lectures from the PET course a very thorough and relevant temporary works course could be delivered to military construction forces. The challenge would be to deliver sufficient practical information to the MCF. There were numerous insightful examples of good and bad temporary works practices delivered during the Laing O’Rourke course, supplemented with photographs, sketches and You Tube clips and so I am sure relevance to military engineering projects could easily be achieved.

I think a temporary works coordinator course would be a useful addition to the set of tools delivered to an MCF project delivery team. The ability to recognise the non-designed temporary works that are required for a project to be delivered, and how they are to be managed (identified, designed, checked, certified, monitored, reviewed), would only improve the efficiency and safety of a project.

Cause of failure? Prop locations, different crane used to that designed for, outrigger spreaders

Conclusion

My initial view of working on a Laing O’Rourke project is that they appear pretty diligent regarding temporary works challenges. Their engineers get site experience after graduating from a civil/building degree. There is a rotation between sites (it seems everyone will do their time at Hinkley) to gain broad experiences. When suitably experienced, engineers are trained (refreshed) in engineering principles to strengthen their ability to manage and lead temporary works. This seems pretty analogous to officers within the Royal Engineers but perhaps a slightly greater emphasis on temporary works for the wider Corps MCFs should be made (as well as the many other courses they are now advised to complete) as we move back into an upstream capacity building role.

Overview. I am working on a Laing O’Rourke project near Elephant and Castle Station. The site previously consisted of an 8-storey office block which was mostly demolished prior to site handover. It included a one-storey basement and therefore the start state for this project is at one storey below ground level. The project endstate is the erection a 40-storey residential tower complete with two basement levels, along with a separate office development of eight storeys.

The existing (confined) site

Contract. The project is currently running on a Letter of Intent to achieve enabling works which comprise of the secant pile wall and capping beam, construction of part of the bearing piles, realignment of mechanical and electrical utilities and demolition of an existing sub-station. These works total £4.4M with a provisional sum of £1.1M to effectively close the project if the subsequent superstructure contract is not approved. The enabling works would give a future developer opportunity to construct something of their design, hence making the site attractive to other investors. This staged approach also gives the client time to ensure the remaining programme to build the tower meets their time and cost drivers. Quality is also important, but the balance is very much cost, then time and quality.

Pile load test. The design of load bearing piles for the tower will be finalised based on the results from the static load test that was carried out this week. The soil profile is generally 7m of river terrace deposits, 20m of London clay and then a deeper band of Lambeth Bed sands. Toeing into the sand (circa 30m pile length) will give the end bearing resistance needed but the number of piles will be determined from analysis of the load bearing test. Having heard John bang on about these types of soils I have now seen them and a static load bearing test rig in action – all making sense.

Pile load test. Test to 10MN or 75mm settlement.

There are two proposals for the load bearing piles:

1. Individual large diameter piles (41no 1500mm diameter rotary under bentonite)
2. Raft foundation (comprising 124no 750mm CFA piles).

The confined nature of the site means the bentonite option is not preferred because the amount of equipment would mean little else could happen concurrently onsite. Therefore the raft option is likely to be adopted, notwithstanding the outcome of the load bearing test, although it will mean excavation around the piles is pretty tight.

Sustainability. Laing O’Rourke are keen to demonstrate adoption of the Construction Logistics and Cycle Safety (CLOCS) initiative. It was brought home as I read an article in the Evening Standard which talked about the death of a cyclist after being hit by a HGV yesterday

Evening Standard reporting of cyclist death

The statistics point to HGVs being responsible for a high proportion of accidents considering their number compared to other road users. Furthermore, the HGVs were often construction vehicles such as tippers or mixers. I then picked up the NCE magazine to is see an article on “Cyclists’ safety is now critical”. There are levels of adoption of CLOCS going from using CLOCS compliant supply companies (see photo below of tipper with side protection rails and warning signage) to running Construction/Cycle days where cyclists can come and get a mini bike service and have a chat about cycle safety. The question is how is this best achieved on this site to show adoption of the scheme, especially as the site is adjacent to one of Boris’s cycle superhighways.

CLOCS Compliant tipper vehicle on site

The digital age. At this stage of the project the understanding of how best to implement BIM and realise the benefits of digital engineering is yet to be determined. There have been some point cloud (3D image survey) productions of the site (see below) but how this can be advanced is being established. The Laing O’Rourke Leadenhall Project (Cheesegrater) modelled the construction process of the whole building to refine the method in order to make it more efficient. Other advantages of digital engineering include cost and time savings by being able to demonstrate exactly what is required and the sequence in which the works would need to be carried out. At a more refined level, 3D modelling of reinforcement in the capping beam is an area which is likely to be explored due to the variation along the length of it on this particular site, not to replace drawings but to be used alongside them. The capping beam is an area I am to be responsible for so more to follow.

Point Cloud Survey of the site.