Geotechnical Consulting Group

Flashback Friday | No. 1 Poultry, London... Two London Underground Central Line tunnels lie to the North, while three London Underground Waterloo & City Line tunnels are present to the South. All of these tunnels converge at Bank underground station, which is just to the east of the Site. The London Underground tunnels were constructed over one hundred years ago, with cast iron segmental linings. The tunnels themselves are sensitive to distortions, as is the machinery inside the tunnels, such as the pedestrian “Trav-o-lator” or moving walkway contained within one of the London Underground Waterloo & City Line tunnels. GCG were retained by LUL to examine the short-term and long-term effects of construction on the tunnels and installations within them using advanced numerical methods. The detailed numerical analysis mimicked the historic development of the site and construction of the new structure. The most critical conditions were identified by modelling the construction sequence with the stage-by-stage deepening of the basements. Based on this analysis, a further suite of analyses were undertaken to predict the longitudinal profile of the Trav-o-lator during construction. This allowed an assessment to be made of the effects of the development on the continued operation of the Trav-o-lator. To find out more, visit our project case study: https://lnkd.in/eG8-T7VA #flashbackfriday #gcg #geotechnicalengineering #consultingengineer #rail #underground #soilconditioningtreatments #boredtunnel #tunnelling #tunnels #constructionnmethodology #soilanalysis

Flashback Friday | No. 1 Poultry, London... Two London Underground Central Line tunnels lie to the North, while three London Underground Waterloo & City Line tunnels are present to the South. All of these tunnels converge at Bank underground station, which is just to the east of the Site. The London Underground tunnels were constructed over one hundred years ago, with cast iron segmental linings. The tunnels themselves are sensitive to distortions, as is the machinery inside the tunnels, such as the pedestrian “Trav-o-lator” or moving walkway contained within one of the London Underground Waterloo & City Line tunnels. GCG were retained by LUL to examine the short-term and long-term effects of construction on the tunnels and installations within them using advanced numerical methods. The detailed numerical analysis mimicked the historic development of the site and construction of the new structure. The most critical conditions were identified by modelling the construction sequence with the stage-by-stage deepening of the basements. Based on this analysis, a further suite of analyses were undertaken to predict the longitudinal profile of the Trav-o-lator during construction. This allowed an assessment to be made of the effects of the development on the continued operation of the Trav-o-lator. To find out more, visit our project case study: https://lnkd.in/eG8-T7VA #flashbackfriday #gcg #geotechnicalengineering #consultingengineer #rail #underground #soilconditioningtreatments #boredtunnel #tunnelling #tunnels #constructionnmethodology #soilanalysis

We wish you a joyful festive season and a prosperous New Year. We are grateful for your friendship and support and look forward to continuing fruitful collaborations and engaging in new exciting opportunities. For our traditional donation, this year we have chosen Macmillan Cancer Support: https://lnkd.in/gmfbxP7

Flashback Friday | Sizewell B & C In the late 1980’s proposals for further development of the Sizewell site were in place and a detailed site investigation had been completed. Following completion of this work, designs for a new nuclear power station were prepared, which included an excavation to a maximum depth of 12m below ground level. The diaphragm walls were to act as embedded cantilevers and an important consideration in their design was the potential effect of differential movements along their length on the water-tightness of any joints within the wall. GCG was commissioned to advise on and undertake deformation analyses, appropriate to the design of the proposed diaphragm wall around the site. GCG’s finite element (FE) modelling employed non-linear stiffness characteristics of soils at small strains, which had an important influence on predictions of ground and wall displacements. A number of these analyses were undertaken in order to investigate the impact of various design assumptions on wall movements during the proposed dewatering and the subsequent excavation, and also to assess long-term conditions. The results of these analyses were used to inform the design of potential ground and wall displacements as well as the critical bending moments within the diaphragm walls. To find out more, visit our project case study: https://lnkd.in/e6EXMtDh #flashbackfriday #gcg #geotechnicalengineering #consultingengineer #nuclear #nuclearenergy 

Yesterday, I had the pleasure to deliver a lecture on "Overcoming challenges in horizontal directional drilling (HDD) - a geotechnical engineer's perspective" at the Institution of Civil Engineers (ICE) London. Thanks to British Tunnelling Society Young Members for organising, and Arabel Vilas Serín for chairing the session. The turnout was great, with many joining in-person at the ICE and over 140 attendees joining online. I am glad to have shared my experiences and perspective on HDD with fellow engineers. In my presentation, I highlighted the importance of recording and monitoring of field data which can only be achieved through close collaboration with the site team. And it is down to us, geotechnical engineers, to influence this cultural change of good HDD practice by developing rapport with the drillers, mud engineers, and workers on site. I also encouraged other practitioners in this field to enable the sharing of knowledge, data and case histories in order to advance this field. It was a delight to receive many positive feedbacks and engage in many stimulating follow-up discussions with the attendees. I am more than happy to continue with such discussions so please do not hesitate to reach out. Finally I would like to thank Geotechnical Consulting Group for their support, and special thanks to my co-authors of the paper (https://shorturl.at/7PX2O), Dr Chris Menkiti and Professor Stephan Jefferis.

GCG Senior Geotechnical Engineer, Serena Che, to deliver a British Tunnelling Society Young Members (BTSYM) Lecture... We are pleased to announce that GCG’s Senior Geotechnical Engineer, Serena Che, will be delivering an in-person lecture, organised by the British Tunnelling Society Young Members (BTSYM), entitled ‘Overcoming challenges in horizontal directional drilling – a geotechnical engineer’s perspective’, on 11th December 2024, at the Institution of Civil Engineers (ICE), from 18:00 – 19:30. This event is FREE TO ATTEND. Event Information: Horizontal directional drilling (HDD) is a trenchless method commonly used for pipeline and cable installation. It is ideally suited to crossings beneath natural and manufactured obstacles and offers substantial cost, safety and environmental benefits. Despite the wide use of HDD, there remain concerns regarding project risk in certain situations. Key to HDD success is good management of the drilling fluid and the avoidance of excessive mud loss. Fundamental risks in HDD arise from pressure build-up in-bore leading to hydrofracturing of the ground, heave of the overburden and mud loss – either to formation, subsurface infrastructure or up to the surface. Poor cuttings transport is a main trigger for bore blockage, leading to potential hydrofracture and the manifestation of the hazards associated with these risks. In this lecture, a case study involving HDD bores for cable landfall of an offshore windfarm is discussed. The aforementioned risks associated with mud loss are most severe in this type of HDD, where drilling starts at a clifftop and descends to punchout in the seabed. In-bore pressures before punchout are elevated by the hydrostatic head of the drilling fluid from the clifftop entry pit. This lecture will conclude with some lessons learnt, recommendations to minimise the risks of hydrofracture and bore blockage, and advice to other young engineers interested in this field. Following the event, there will be a networking session with drinks at ICE Kendal’s bar, sponsored by Geotechnical Consulting Group (GCG). To find out more, including booking information, visit - https://lnkd.in/eht_Mtew #GCG #ICE #BTSYM #Lecture #Learning #Education #GeotechnicalEngineering

Flashback Friday | Gode Wind Offshore Wind Farm... Located in the German part of the North Sea, the Gode Wind Offshore Wind Farm (OWF) and comprises nearly 100 wind turbine generators (WTG), each of which is supported by a 7.5 m diameter monopile foundation. The ground conditions in this area feature relatively homogeneous dense to extremely dense sands overlain by looser post-glacial sediments. At the time, monopiles in sand were commonly designed using the API p-y formulation. This method is based on empirical load-displacement data obtained from full-scale load testing conducted in the 1970s. However, the dimensions of monopiles significantly differ from the dimension of piles used in those historic tests. Consequently, the application of the API p-y formulation would have been stretched beyond its verified range. The Gode Wind OWF monopiles were designed using modified API p-y curves. As part of the design process, GCG was commissioned to undertake 3D FE analyses to predict the behaviour of monopiles at selected locations across the OWF, to benchmark and validate the geotechnical design under serviceability and ultimate limit state conditions. The FE analyses incorporated advanced soil models to accurately represent the small strain stiffness properties of the sands, adopting reasonably conservative parameters. To find out more, visit our project case study: https://lnkd.in/eQRDKk-u #flashbackfriday #gcg #geotechnicalengineering #consultingengineer #windenergy #offshorewind #offshorewindfarms #monopiles 

Flashback Friday | Heathrow Airport, Terminal 5... The majority of the below-ground construction at London Heathrow Airport’s Terminal 5 (T5) was carried out in deep open-cut excavations made in the London Clay Formation underlying Terrace Gravels. There was a need to adopt slopes that were as steep as possible, to minimise the excavation and backfill volumes, but which would be stable for periods of up to 6 months. Temporary slope geometries were initially selected on the basis of experience and precedents for other, usually shallower, short-term slopes cut in the London Clay Formation. GCG was commissioned to carry out finite element (FE) analyses of the temporary slope geometries at T5. The aims of the analyses were to examine the times before failures developed and to identify the potential failure mechanisms. Prior to carrying out the FE analyses, the GCG team specified extensive ground investigations at T5 to characterise in detail the London Clay Formation. Appropriate soil models were chosen and associated model parameters derived. The models were then calibrated using two cases of slope failures local to T5. To find out more, visit our project case study: https://lnkd.in/e-5YHiiq #flashbackfriday #gcg #geotechnicalengineering #consultingengineer #airports #aviation

Our Senior Partner Dr Angeliki Grammatikopoulou will be presenting an online lecture entitled: “The application of numerical analysis in the assessment and design of monopiles for offshore wind farms” next Wednesday on the 20th November at 6pm EET. The lecture is organised by the Hellenic Society of Soil Mechanics and Geotechnical Engineering (HSSMGE Greece) and will be presented in Greek.   The lecture will be broadcasted live. A link to the lecture will be posted by the HSSMGE soon.

Due to the planned Tube strikes this Thursday, 7th November, the British Tunnelling Society Young Members have decided to postpone the upcoming evening lecture by our Senior Geotechnical Engineer Serena Che to 11th December 2024. The lecture will take place at the Godfrey Mitchell Theatre at the Institution of Civil Engineers (ICE) from 18:00 to 19:30 with post lecture drinks sponsored by GCG. Further details of the lecture may be found here: https://lnkd.in/ekS3HaAt This event will still be a hybrid event and will be broadcast live via zoom. Hope to see you there!