The Award for Technical Excellence celebrates a technical development that has helped a company improve its performance or delivery of a project. Entrants were expected to demonstrate innovation to reduce costs, improve efficiency or improve safety; collaboration with clients and partners to develop solution; potential to benefit future project or application delivery; and enabling previously challenging project or concept to be delivered at lower risk.
Atkins and London Underground – London Underground: Chalfont and Latimer to Chesham Metropolitan line enhancement works
Atkins was commissioned by London Underground (LU) to carry out enhanced design works at an earthworks cutting located on the Metropolitan line between Chalfont & Latimer and Chesham stations. Four key areas of advancement were made during the project: type of restraint provision for Rope Access works being undertaken on the slope below; installation method and type of erosion mat pin restraint; use of advanced topographical survey equipment; and use of specially prepared soil nailing plant. The collaborative effort made by the team during the enhancement works has enabled the 125-year-old cutting to be brought up to current design standards, minimising future maintenance costs and has greatly improved the operation safety of the line for the next generation.
Bam Ritchies – A holistic approach to the treatment of abandoned chalk mines
The holistic approach to tackling abandoned chalk mines began at Briars Lane where a flexible grout treatment system, adapting to varying ground conditions, was developed. It was then improved further and used successfully for three subsequent projects. The solution involves 3D modelling which facilitates treatment management and helps understanding of data anomalies, edge effects and development masking. A single OPC limestone mix was developed that permeates through debris and provides compaction in lower permeability ground. The validation procedure developed establishes new standards allowing objective assessments of success and value for money. The treatment strategy also includes consistent risk management. Real-time monitoring ensures good control and 3D model updating throughout the project.
Cambridge University, Thames Water’s Lee Tunnel Project Management Team, and the Morgan Sindall, Vinci and Bachy Soletanche joint venture – Closing the loop – performance-based design of a deep circular shaft in London
During the design stage for tunnelling projects, it is crucial to reliably predict the magnitude and distribution of ground movements around these excavations to design adequate protective measures for adjacent infrastructure. It is also important to understand the strains and stresses in the shaft lining. The objective of the monitoring scheme at Thames Water’s Abbey Mills Shaft F was to address these two challenges. The instrumentation used for the scheme comprised fibre optic strain sensing technology to measure strains in the diaphragm walls. In addition, conventional instruments were installed to monitor the ground movements associated with the shaft construction. As suggested by this study, future shafts can be designed and built with diaphragm walls optimised to take the loading more efficiently. As a result, the volume of concrete and/or reinforcement used could be significantly reduced.
CH2M Hill – Geotechnical risk management for the mechanised tunnelling on the Kishanganga Hydroelectric Project in Kashmir, India
The Kishanganga 330MW Hydroelectric Project required 15km of the tunnel to be constructed using a 6.18m diameter double-shield tunnel boring machine (TBM) to erect a segmental concrete lining. Squeezing ground conditions had the potential to either entrap the TBM and/or to cause overstressing of the segmental lining which had to be erected at the rear of the TBM shield. CH2M Hill undertook geotechnical design and co-ordination of the work involved to develop the strategy and geotechnical risk mitigation approach. A guidance document was prepared for use on site to manage the risks to the TBM, segmental lining and personnel. The TBM tunnel was completed successfully ahead of budget and schedule in May 2014, with additional cost and programme savings compared to previous tunnelling methods used in the Himalayan region.
Dr Sauer & Partners and London Underground – Assessment of existing infrastructure using a staged ground movement approach for the Bank Station Capacity Upgrade
The Bank Station Capacity Upgrade involves the construction of large tunnels and shafts in close proximity to existing London Underground (LU) civil assets. With more than 300 assets in the zone of noticeable impact, it was crucial to efficiently assess the structural and operational impact of the ground movement associated with the excavation. A rationalised, staged approach was adopted, including risk-based reviews of LU operational issues to avoid unnecessary intrusive mitigation measures. This approach made the assessment more efficient, allowing focus to be directed on the assets where movements will have the greatest impact.
Groundforce and the Costain Skanska joint venture – Development of a bespoke high preloading temporary propping solution for Crossrail’s Paddington Box project
Crossrail Paddington Station Box is a 263m-long, 22m-wide and 20m-deep, reinforced concrete box structure, which involved a unique construction excavation to within 100mm of a live tunnel. The Costain and Skanska join venture (CSJV) approached Groundforce to develop auxiliary prestressing units (APUs) for Groundforce’s 750Te hydraulic props. Two temporary additional jacking rams were introduced into the system to augment the central ram on each prop. The development of a high pressure hydraulic pump meant that the required pre-load could be delivered in a phased manner between the three rams. Extensive load monitoring was undertaken of the temporary props at Paddington, this allowed the design and construction teams to better understand the behaviour of the structure. The data collected is being used to further industry understanding of the behaviour of major propping schemes.
Mott MacDonald – The accelerated programme for the Moorgate shaft at Crossrail’s Liverpool Street Station
As part of the Crossrail Project, the start of the Moorgate shaft diaphragm wall construction was delayed by 11 months due to the need to extract the foundation piles of the building that had previously occupied the site. Mott MacDonald identified a potential programme saving through omission of some or all of the temporary works props by using 3D numerical modelling of the actual construction sequence of both the shaft and the adjoining SCL tunnels. Mott MacDonald embarked on a carefully defined and controlled Verification Process that used real time site data to re-engineer the design. Effectively this was a reverse Observation Method approach delivered a 14-week programme saving so that the shaft base slab was completed two weeks ahead of the project critical milestone for handover to the tunnel contractor.
Utterberry – Use of wireless sensors for remote monitoring during construction of the Eleanor Street shaft and adits for Crossrail
At Crossrail’s Mile End station, a network of 30 Utterberry self-powered wireless sensors were used to remotely monitor Crossrail tunnel conditions during construction, measure tunnel wall-inclination and displacement in three axes with sub-millimetre precision, along with tunnel temperature and humidity. The installation of the sensors was performed by one person, using a 3m pole. The entire sensor system weighed less than 20g. No scaffolding or cherry picker lift systems were required, and the entire installation took less than four hours. The data produced by the monitoring system is a rich dataset that provides substantial information about the conditions of the monitored assets. The system is also self-resetting in the event of sensor disturbance, and this action can be performed remotely without operator intervention.
VHE Construction – In-situ remediation of chromite ore processing residue at Shawfield, Glasgow
The Shawfield Project involved the removal of the risks associated with ground contamination on the site, mainly in the form of chromite ore processing residue (COPR), and the preparation of derelict land for redevelopment. The Remedial Options Appraisal recommended the use of a highly reactive chemical reductant solution, HM Earthcare Calcium Polysulphide, which was selected for in-situ chemical injection. The solution was injected under low pressure via steel rods inserted into the ground to a prescribed depth. The injection works successfully treated around 70,000m3 of COPR contaminated soils to 6m below ground level in a six-month treatment period. VHE Construction was also responsible for the demolition of several buildings and removed in excess of 25,000m3 of surface concrete and foundations which were processed, recycled and re-used on site.