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Jefferis S.A.,Environmental Geotechnics Ltd. | Jefferis S.A.,University of Oxford | Merritt A.S.,Geotechnical Consulting Group LLP
Coupled Phenomena in Environmental Geotechnics: From Theoretical and Experimental Research to Practical Applications - Proceedings of the International Symposium, ISSMGE TC 215 | Year: 2013

When tunnelling in unstable grounds it is necessary to remove the cut soil from the face whilst maintaining face stability. This can be achieved by slurrifying the excavated soil and using a circulating fluid to remove it from the face. In another system, earth pressure balance tunnelling, the cut soil is continuously formed into a paste which is extracted via a screw conveyor in which it must build a plug. To support the face, the slurry or paste must seal the face as it must be pressurised sufficiently to counter the soil and groundwater pressures. Typically, bentonite slurries are used for slurry tunnelling but polymer systems can offer advantages. For earth pressure balance machines, soil conditioning additives are more complex and varied; many different materials are used including foams. This paper gives an overview of the problems associated with analysing the behaviour of tunnelling additives and invites further research. © 2013 Taylor & Francis Group.


St John H.D.,Geotechnical Consulting Group LLP
Geotechnical Aspects of Underground Construction in Soft Ground - Proceedings of the 8th Int. Symposium on Geotechnical Aspects of Underground Construction in Soft Ground, TC204 ISSMGE - IS-SEOUL 2014 | Year: 2014

All building and civil engineering projects needing basement and sub-structures require geotechnical engineers to work closely with a project team from the project conception through to completion in order to identify and manage the risks that the ground and surroundings present. The appreciation of these risks requires an understanding of the way in which cities have and are evolving and an appreciation of the institutional framework within which we operate. The paper describes how such projects evolve and draws a distinction between the smaller scale 'domestic' basement schemes and 'commercial' schemes both of which present new challenges to our skill and ingenuity. © 2014 Korean Geotechnical Society.


Elshafie M.Z.E.B.,University of Cambridge | Choy C.K.C.,Geotechnical Consulting Group LLP | Mair R.J.,University of Cambridge
Geotechnical Testing Journal | Year: 2013

Major cities in the world are experiencing a rapid growth in population while becoming increasingly overcrowded and congested. In recent years, this has created a huge demand for underground infrastructure, which often involves the design of major mass transit tunnel systems; these tunnel systems (underground tunnels and metro stations) are becoming increasingly necessary to construct in very close proximity to existing buildings. The prediction of excavation-induced deformations, therefore, becomes a key issue in the planning and design process for these schemes. However, current design approaches are conservative and often lead to unnecessary concern and expenditure in the design and provision of protective measures. A better understanding of the mechanisms involved in the excavation soil-structure interaction could reduce costs and help avoid potential problems. A series of small-scale model tests was carried out in the geotechnical centrifuge at Cambridge University to investigate the interaction between excavations and model buildings. Excavations (simulated by adopting a novel two-fluid technique) in a "free field" were also undertaken to assess the difference between free-field ground movements and those affected by a stiff model building. A detailed description of the centrifuge models and test procedures is presented in this paper, followed by the presentation of test results that demonstrate the effect of the stiffness of the model building on the excavation-induced displacements. Copyright © 2013 by ASTM International.


Barbosa P.,Iberdrola | Geduhn M.,IMS Ingenieurgesellschaft MbH | Jardine R.,Imperial College London | Schroeder F.,Geotechnical Consulting Group LLP | Horn M.,Bilfinger Construction GmbH
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 | Year: 2015

Iberdrola is developing the Wikinger offshore windfarm in the German Baltic Sea. Wind turbines are supported by four legged jackets founded on driven open ended steel piles. Loading will be predominantly axial with shaft resistance governing design. Ground conditions over much of the project area comprise of thick Chalk layers. A review of current pile design methods and related onshore pile test campaigns highlighted significant design uncertainties and led to a decision to conduct dynamic and static offshore pile tests. This paper summarizés the aims and rationale of the tests carried out in late 2014, describes the design of the remotely operated testing arrangements and reports on an associated research project that is advancing with Imperial College London and Geotechnical Consulting Group. © The authors and ICE Publishing: All rights reserved, 2015.


Barbosa P.,Iberdrola | Geduhn M.,IMS Ingenieurgesellschaft MbH | Jardine R.,Imperial College London | Schroeder F.,Geotechnical Consulting Group LLP | Horn M.,Bilfinger Construction GmbH
Frontiers in Offshore Geotechnics III - Proceedings of the 3rd International Symposium on Frontiers in Offshore Geotechnics, ISFOG 2015 | Year: 2015

Iberdrola is developing the Wikinger offshore windfarm in the German Baltic Sea. The wind turbines will be supported by four legged jackets founded on driven open ended steel piles. Loading will be predominantly axial with shaft resistance governing design. Ground conditions over much of the project area comprise of thick Chalk layers. A review of current pile design methods for Chalk and related onshore pile test campaigns highlighted significant design uncertainties and led to a decision to conduct dynamic and static offshore pile tests at the site. This paper summarizes the aims and rationale of the tests carried out in late 2014, describes the design of the remotely operated testing arrangements and reports on an associated research project that is advancing in conjunction with Imperial College London and Geotechnical Consulting Group. © 2015 Taylor & Francis Group, London.

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