Towards the end of 2020 the Nigerian Society of Engineers (NSE), UK branch invited Dr Mothersille to deliver a presentation to its membership covering his area of expertise. In January 2021, Dr Mothersille gave a presentation entitled ‘An Introduction to Ground Anchor Technology’. The presentation’s objective was to provide the audience with an insight into ground (grouted) anchor technology, initially defining terms and exploring the concept and then showing a variety of applications by drawing on examples from a worldwide database. After briefly covering some basic implementation features, a case study was described that captured several world firsts concerning ground anchor usage. By the end of the session, there was no doubt attendees gained an improved fundamental understanding of how ground anchors are applied, designed, constructed and tested.
The event was declared a resounding success by the President of the NSE, Dr. Sunday Popoola. The audience’s enthusiasm was proved by the fact that the Q & A session, convened afterwards, lasted longer than the 50-minute presentation itself!
It has been years in the making, but finally, a book deal is agreed with internationally renowned publisher Taylor & Francis Group. The textbook, scheduled for completion in summer 2023, is entitled ‘Grouted Soil and Rock Anchors’.
The book is aimed at consulting engineers, contractors; civil, structural and geotechnical engineering students and even asset owners, who during their activities, propose or encounter the use of grouted anchors. These geotechnical installations have been used worldwide to support various types of structure. Over time, millions of grouted anchors have been installed successfully ranging from systems of a few tonnes capacity in small retaining walls to pre-stressed tendons of several thousand tonnes capacity to resist direct tension, sliding, overturning and dynamic loading in dams. Other applications include stabilising deep excavations, bridge abutments and several different forms of geotechnical structure.
Anchors have established a permanent place in construction practice, but for engineers and asset owners not yet thoroughly familiar with modern anchoring technology, conventional and potential applications will be outlined to provide some perspective and encourage further exploitation.
The book is structured around the key areas of design, construction, testing and service behaviour performance. In addition, maintenance inspection, condition assessment, innovative applications and current research will be addressed. In recent years standards and codes of practice have undergone significant changes, particularly in Europe, and these essential developments will also be covered.
Dr Devon Mothersille is the lead author with highly respected co-authors Dr Donald Bruce (USA) and Professor Stuart Littlejohn (UK). The authors have collectively compiled over 120 years of experience and published hundreds of technical papers and articles covering various aspects of geotechnical engineering with particular reference to ground anchoring practice. Their collective expertise has been developed from direct input into projects all over the world, academic and industrial research, and dedicated participation in various committees associated with the development of standards, codes of practice and best practice guidance documents.
November 2020 has seen the publication of the new CIRIA report C794 entitled ‘Grouted anchors and soil nails: inspection, condition assessment and remediation’. This unique document fills a gap in the current literature, where there is limited guidance on this highly specialised area. It will undoubtedly assist asset owners, designers, contractors and others involved in the condition assessment, planning and execution of the works, including monitoring, maintenance, remediation, repair and replacement of grouted anchors and soil nail structures.
The drafting of C794 was a team effort. CIRIA awarded the contract for the work to the geotechnical engineering consultancy Gavin & Doherty Geosolutions Ltd (GDG). Following reviews from a project steering group, comprising some 20 individuals, GDG engaged the services of Mr Chris Irvin (Dywidag, UK) and Dr Devon Mothersille (Geoserve Global Ltd and Single Bore Multiple Anchor Ltd) for specialist input as technical authors.
The Covid-19 pandemic demanded that the launch event for C794 took place online, and this was judged successful with some 85 participants attending. The technical authors delivered four presentations covering the following:
Introduction and background
Grouted anchors: Condition assessment and remediation
Grouted anchors: monitoring and maintenance
Soil nails and soil nail structures
The presentations were followed by a question and answer session that allowed members of the audience to clarify points of interest and gain more detail on specific areas.
AnchorTestTM is an innovative Cloud-based software package, specifically developed for tablets, that permits anchor test data assessment and management in real-time. The solution has two components: a front-end tablet app runs on the Apple iPad platform, and a back-end Cloud-based system running on Amazon Web Services with an online cross-platform website, which can be accessed from any PC, tablet or even mobile smartphone. This tool provides full data analysis and data management capabilities and portability to create greater efficiency in the anchor testing process. AnchorTest is programmed to accommodate the major international anchor testing codes and incorporates a revolutionary, intuitive user interface. The use of this tool creates an environment where the testing of grouted anchors has effectively become a paperless exercise, with access to instantaneous feedback on the performance of the anchors in relation to established acceptance criteria.
The Qatar Petroleum multi-storey car par project involves major deep excavation works incorporating removable single bore multiple anchors (SBMAs). These anchors are unique in that although they are removable, they are classified as permanent since a ten-year design service life was specified by the structural designers. The anchor tendons were designed by SBMA Ltd and manufactured by DeCa srl in Italy before being shipped to site in Qatar.
The mandatory acceptance testing of the production anchors is currently underway, and the use of AnchorTest has allowed specialist foundation contractor, Bauer (Qatar), to operate with improved efficiency by reducing time and costs.
SBMA Ltd, in collaboration with its certified tendon manufacturer DECA srl, have been awarded the contract to implement removable anchors for the Maggoire Policlinico Hospital in Milan, Italy. The deal involves the design, manufacture, supply and supervision of the removable anchors which will form an integral part of the foundation support system.
The SBMA removable anchor technology will be the first of its type to be used in Italy and represents an exciting opportunity for the company. The anchors are to be installed in alluvial deposits, typically comprising sands and gravels and have working loads ranging from 410kN to 700kN.
To improve the understanding of this pioneering technology, the main contractor (SIS SCPA) and specialist anchor contractor (Palingero) were invited to an impressive demonstration at the DeCa factory in Genoa. Delegations from these organisations attended the demonstration which featured a full-scale removable anchor tendon being removed from a simulated borehole after being stressed and locked-off.
Travel restrictions imposed by the Covid-19 pandemic presented challenges for Dr Mothersille attending the session; however, these were overcome by using the Facetime facility on iPhone. Using this feature, Dr Mothersille was able to participate in the demonstration and discussions in real-time. Once again, this demonstrates how innovative thinking and technology can be utilised to adapt to and overcome the difficult circumstances the industry currently faces.
A trial anchor programme is scheduled for commencement in the coming weeks.
iPhone screen shows Dr Mothersille (insert) participating in discussions in Italy from his office in the UK
iPhone screen shows Dr Mothersille (insert) participating in a factory demonstration in Italy from his office in the UK
Craig Goch Dam is a masonry gravity structure built between 1897-1904. The dam is 36.5 m high above the river bed, 119 m long, 32 m thick at the base and the foundation extend 3 m below the river bed. Craig Goch reservoir has a capacity exceeding 9 billion litres covering an area of 217 acres. The primary purpose of the dam and other reservoirs in the area is to supply Birmingham with water.
Purely for intellectual interest, Dr Mothersille and his 26-year-old son Reiss visited the structure and were fortunate enough to witness it spilling and conveying thousands of litres of water downstream.
Dr Mothersille and son, Reiss, enjoy the spectacular views of water cascading over the spillway at Craig Goch dam
Once again, the wonders of modern technology have proven effective in allowing methods of working that would not have been feasible some years ago. Accompanied by his 26 years old son Reiss, Dr Mothersille travelled to the Elan Valley in Wales to visit the Craig Goch dam. However, the travel plans were such that they clashed with a leadership event hosted by the British Standards Institution. Using the Zoom app on his mobile phone and the WiFi facilities at a service station on the M50 motorway, he was able to attend the two-hour session.
The event featured four speakers covering the following:
Update on international and European standards development policy
Update on National standards development
Inclusivity – Committee Member survey results
Evolving role of BSI as the UK’s National Standards Body
Adapting the new ‘normal’ – benefits and challenges of the abrupt move to 100% remote or virtual standards development and the on-going business/economic impacts of lockdown on participation in standards development
Dr Mothersille remotely attends BSI’s Leadership in Standards-Making event
To supplement his knowledge gained from previous training in expert witness evidence with Legal Experience Training, Dr Mothersille recently attended the Master Class in Cross-Examination via Zoom. The session involved live role-play of the cross-examination of two experienced expert witnesses by a senior barrister. A QC Deputy High Court Judge presided over the proceedings, while interventions and analysis was carried throughout by Solicitor and Director of Legal Experience Training, Penny Harper.
Before the course, attendees were presented with extracts from expert witness reports and a schedule of differences of opinion between the experts. The session lasted one hour, 30 minutes and many learning outcomes were derived, which included:
• Consider how to demonstrate the factual/evidential basis of your opinion
• Delivery of a well-reasoned objective opinion and consideration of alternative methods and facts
• Anticipate and deal with the strengths and weaknesses in expert evidence on both sides
• Effective communication of complex technical evidence and reasons for agreement or disagreement
• Handle challenging cross-examination techniques
• Assist a decision-maker in understanding the facts and underlying methodology used to reach a conclusion
Overall this was an informative and enjoyable session that provided fascinating insights into, what can be, a challenging area in a specialist geotechnical engineer’s career.
Dr Devon Mothersille listens intently during the intense cross-examination of an expert witness
The Great Ocean Road is one of Australia’s most beautiful locations and arguably delivers one of the world’s greatest driving roads. Recent studies by the Department of Transport (DoT) in South Western Australia revealed the need for a detailed inspection and condition assessment of an anchored slope, located along the route, about 148km southwest of Melbourne.
Travel restrictions imposed by the Australian government, due to the Coronavirus pandemic, has necessitated a novel approach to this work. Like many sectors, the geotechnical engineering industry has had to adapt to accommodate the challenging times the world currently faces.
Recently, Dr Mothersille, through his consultancy Geoserve Global Ltd, was appointed specialist consultant to support the excellent team at the DoT. The DoT must address technically complex issues with the existing anchored rock slope. The logistical constraints associated with the site location meant that the examination of digital photographs allowed an initial assessment of the anchored rock slope. However, this progressed to the use of 3D UAV photogrammetry, where the use of drones, in conjunction with state-of-the-art software, created high-resolution 3D digital models of the anchored structure (see Figure 1).
Dr Mothersille is currently analysing these models from a rock mechanics and rock anchoring perspective to select anchors that will be subjected to detailed investigation to assess their service performance and condition. Following this, strategies will be developed for progressing the investigation remotely, without compromising the level of technical excellence required.
Figure 1: Typical screenshot captured from the 3D model created by the use of UAV photogrammetry techniques
In collaboration with foundation contractors Bauer (Qatar) and Bauer (Abu Dhabi), SBMA Ltd was engaged to design and supply the ground anchors that form an integral part of the excavation support system for the Qatar Petroleum Multi-Storey Car Park in Doha, Qatar. Construction of the 14m deep excavation will be in ground described as highly weathered Simsima Limestone. SBMA Ltd has developed a substantial amount of anchoring experience in this type of rock, having worked in the region on significant foundation projects before.
The unusual feature of this project is that the specification stipulates that the anchors are to be removable with a design service life of 10 years. Essentially, this classifies the anchors as permanent-removable anchors. SBMA Ltd’s innovative anchor design followed BS8081: 2015+A2: 2018, the British Standards Institution Code of Practice for Grouted Anchors. This code of practice included the recommendation for double corrosion protection and was approved by the client’s engineers at Qatar Petroleum.
SBMA Ltd was required to supply the anchor tendons and associated accessories in addition to designing the anchors. SBMA Ltd’s certified tendon manufacturer, DeCa Srl (based in Genoa, Italy) satisfied all the pre-qualification requirements and were subsequently commissioned to manufacture and supply the tendons, anchor heads and accessories, including special galvanized protective caps. SBMA Ltd wishes to take this opportunity to thank DeCa Srl for their resolve in delivering an excellent service despite the challenges imposed by the Covid-19 pandemic.
Fortuitously SBMA Ltd has trained and supervised engineers at Bauer (Abu Dhabi), so even though the UK is currently subject to travel restrictions; supervision of the works in Qatar will be by engineers from Abu Dhabi. When required, SBMA Ltd will provide specialist input via live stream on mobile phones and attend meetings using Teams or Zoom.