Norwegian Geotechnical Institute
Norwegian Geotechnical Institute
Norwegian Geotechnical Institute NGI is a leading international centre for research and consulting within the geoscience. NGI develops optimum solutions for society, and offers expertise on the behaviour of soil, rock and snow and their interaction with the natural and built environment. NGI is a private foundation with office and laboratory in Oslo, branch office in Trondheim and daughter company in Houston, Texas, USA, and during 2014 a daughter company will be established in Perth, Australia. NGI was awarded Centre of Excellence status in 2002.The core competence is within geotechnics, engineering geology, hydrogeology and environmental geotechnology, with expertise within geomaterial properties and behaviour, numerical modelling and analysis, and instrumentation and monitoring. NGI's strength lies in the expertise of its personnel working in collaboration with clients and cooperating partners, to find practical solutions for the industry and society. NGI works within the following sectors: Offshore energy - Building, Construction and Transportation - Natural Hazards - Environmental Engineering. NGI has the honour to be the custodian of the Terzaghi and Peck Libraries. All academic material from Karl von Terzaghi and his colleague Ralph B. Peck has been given to NGI to be available for interested researchers.NGI was the host of the International Centre for Geohazards from 2003-2012, one of Norway's first Centres of Excellence . NGI's partners were NORSAR, the Norwegian Geological Survey , the University of Oslo and the Norwegian University of Science and Technology . Wikipedia.
Kasin K.,Norwegian Geotechnical Institute
Proceedings of the 5th International Conference on Geotechnical and Geophysical Site Characterisation, ISC 2016 | Year: 2016
One of the most difficult deviations to explain, has been an unexpected drop in measured values inside a homogenous clay layer. Using the correlations from Karlsrud et al (2005), the interpreted CPTU sounding show a drop in undrained strength far below a normally consolidated soil at some sites. The paper shows that the drop in cone resistance and interpreted shear strength is due to disturbance and remoulding of the clay caused by previous investigations at the same location, as it is common practise to at least perform either a Norwegian total sounding or a rotary pressure sounding at a location where a CPT is performed. Using the inclination of the probe registered during the CPTU soundings, and the thickness of the disturbed and remoulded layer in the profile, the horizontal extent of the disturbed zone around the previous sounding is estimated to be around 60 cm in diameter, or around 8 - 12 times the diameter of the drill bit that is 57 mm in diameter. © 2016 Australian Geomechanics Society.
Choi J.C.,Norwegian Geotechnical Institute |
Park J.,Norwegian Geotechnical Institute |
Renewable Energy | Year: 2013
The effects of both direction and rate of groundwater flow on the performance of various types of borehole heat exchanger (BHE) arrays are examined using a two-dimensional coupled heat conduction-advection model. The heating operations were simulated over a period of 15 yrs using three types of arrays: rectangular, L-type, and single line. The results show that the performance of the L-type and single line-type arrays (non-square rectangular arrays) was noticeably influenced by the direction of groundwater flow as well as the flow rate. When the characteristic length of Peclet number was assumed to be a unit value, the Peclet number less than 0.05 (i.e. low flow rates less than 1 m/yr in this study) was found to have negligible effects on the performance of the system, regardless of the array type or flow direction. The cold accumulation in the ground downstream of the groundwater flow seems to be related to the variation of the fluid temperature associated with the flow direction. The comparison of annual heat capacity shows that up to 13% difference can occur depending on the flow direction. This suggests that the consideration of both direction and rate of groundwater flow may be important in designing the optimal BHE arrays, particularly for the non-square rectangular arrays. © 2012 Elsevier Ltd.
Park H.,KAIST |
Lee S.-R.,KAIST |
Yoon S.,KAIST |
Choi J.-C.,Norwegian Geotechnical Institute
Applied Energy | Year: 2013
This paper presents an experimental and numerical study on evaluation of thermal response and performance of prototype precast-high strength concrete (PHC) energy pile. Short-term field thermal response tests (TRTs) were conducted for the PHC energy piles installed in partially saturated weathered granite soil deposit, in which two types of heat exchangers were considered: W and 3U-shaped heat exchangers. The TRTs were successfully simulated by three-dimensional finite element analyses employing quasi-steady-state convective heat transfer boundary condition. The numerical model was applied to simulate 3-day TRTs, and the simulation results were used for assessing effective thermal conductivity and thermal resistance. Besides, continuous and intermittent operation simulations of the energy piles were performed, and for the results of performance analyses, discussion was made to evaluate energy efficiency of the prototype PHC piles. © 2012 Elsevier Ltd.
Du J.,Wuhan University |
Yin K.,Wuhan University |
Lacasse S.,Norwegian Geotechnical Institute
Landslides | Year: 2013
The prediction of active landslide displacement is a critical component of an early warning system and helps prevent property damage and loss of human lives. For the colluvial landslides in the Three Gorges Reservoir, the monitored displacement, precipitation, and reservoir level indicated that the characteristics of the deformations were closely related to the seasonal fluctuation of rainfall and reservoir level and that the displacement curve versus time showed a stepwise pattern. Besides the geological conditions, landslide displacement also depended on the variation in the influencing factors. Two typical colluvial landslides, the Baishuihe landslide and the Bazimen landslide, were selected for case studies. To analyze the different response components of the total displacement, the accumulated displacement was divided into a trend and a periodic component using a time series model. For the prediction of the periodic displacement, a back-propagation neural network model was adopted with selected factors including (1) the accumulated precipitation during the last 1-month period, (2) the accumulated precipitation over a 2-month period, (3) change of reservoir level during the last 1 month, (4) the average elevation of the reservoir level in the current month, and (5) the accumulated displacement increment during 1 year. The prediction of the displacement showed a periodic response in the displacement as a function of the variation of the influencing factors. The prediction model provided a good representation of the measured slide displacement behavior at the Baishuihe and the Bazimen sites, which can be adopted for displacement prediction and early warning of colluvial landslides in the Three Gorges Reservoir. © 2012 Springer-Verlag.
Grimstad G.,Norwegian Geotechnical Institute |
Degago S.A.,Norwegian University of Science and Technology
Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering | Year: 2010
Elastoplastic models, based on experiments on reconstituted clays, tend to adapt an associated flow rule. This assumption is then included in models for natural clay. However, laboratory experiments indicate that the idea of associated flow in natural clay is insufficient. Therefore a new model, abbreviated as n-SAC, is proposed in this paper. The model incorporates creep, using the time resistance concept, with a single creep parameter determined from oedometer tests. Two different cap surfaces are defined in the model, i.e. the reference surface (or alternatively surface of equivalent stress measure, p eq) and the potential surface, Q. Different (kinematic) rotational hardening rules for the two surfaces are defined along with two hardening rules for the size of the reference surface. The two size hardening rules consists of one for the decrease in compressibility for equivalent reconstituted material and one for loss of unstable structure. A fully implicit backward Euler implementation scheme for the n-SAC model is used for the simulations shown in this paper. © 2010 Taylor & Francis Group, London.
Nadim F.,Norwegian Geotechnical Institute
Submarine Mass Movements and Their Consequences - 5th International Symposium | Year: 2012
Stability evaluation of submarine slopes under earthquake loading is an important and challenging issue in many offshore geohazards studies. Generally, three scenarios of earthquake-induced slope failure should be evaluated and analyzed: (1) Failure occurs during the earthquake. In this scenario, the excess pore pressures generated by the cyclic stresses degrade the shear strength so much that the slope is not able to carry the static shear stresses, (2) Post-earthquake failure due to increase in excess pore pressure at critical locations caused by seepage from deeper layers; and (3) Post-earthquake failure due to creep. Soils that have strong strain-softening characteristics and high sensitivity are most susceptible to failure during earthquake shaking. The scenario of excess pore pressure migration from deeper layers into critical areas, leading to slope instability, is quite important and could occur over a time span of years or even decades in deep marine clay deposits. However, post-earthquake creeptype failure is believed to be the most common mechanism for clay slopes. In a risk assessment framework, the uncertainties in all the parameters and models used in the stability assessment must be addressed and the consequences of slope failure must be evaluated. It is often difficult to separate the uncertainties due to lack of knowledge (epistemic uncertainties) from the natural variability of the physical parameters such as soil shear strength and earthquake characteristics. The risk assessment procedure outlined in the paper integrates the results of geotechnical evaluations with other evidence, like dating of the previous slide events, to provide a more rational estimate of the annual probability of earthquake-induced submarine slope instability. © Springer Science+Business Media B.V. 2012.
Gauer P.,Norwegian Geotechnical Institute
Cold Regions Science and Technology | Year: 2014
Besides the runout distance of an avalanche information on avalanche intensity along the path is often required for hazard zoning or planning of mitigation measures. The avalanche (front) velocity is a common intensity measure as it can be linked to expected impact pressures. Furthermore, the velocity of an avalanche determines if the avalanche stays in its usual track or if the avalanche unexpectedly deviates and thus endangers areas believed to be safe. Therefore, a reliable prediction of the expected velocities is most important. However, many of the prevailing avalanche models either tend to underestimate velocities or they overestimate the runout distances.In this paper, several avalanche front velocity measurements from the Ryggfonn test site are presented. The measurements are derived from photo and/or video analyses of mainly dry-mixed avalanches. Some of these observations are partly supplemented by Doppler radar measurements.Additionally, the measurements from the Ryggfonn test site are compared with published velocity measurements from other locations to obtain a wider spectrum of avalanche conditions. By analyzing these velocities, constraints for possible rheological models of avalanche flows are obtained.The measurements of the presented avalanches, of which the most were relatively large to their path and can be classified as dry-mixed avalanches (i.e. they were partially fluidized and accompanied by a powder cloud), suggest a lower (apparent) velocity dependency of the bottom friction term than generally believed. The measurements show that the maximum front velocities of these avalanches scale with the square root of the total fall height of the avalanche front, that is, the maximum velocity Um∝Hsc. © 2013 Elsevier B.V.
Berre T.,Norwegian Geotechnical Institute
Geotechnical Testing Journal | Year: 2011
The main purpose of this paper is to describe the present practice for triaxial testing at the Norwegian Geotechnical Institute with particular reference to testing of soft rocks from the oil reservoirs in the North Sea. The following aspects related to this testing are described: (a) testing equipment, (b) procedures for typical stages of the testing, (c) estimation of the allowable rate of loading to control excess pore pressures, (d) means to speed up the expulsion of pore liquid from low permeability rocks, (e) local measurements of strains with LVDTs, and (f) testing at high temperatures. Copyright © 2011 by ASTM International.
Andersen K.H.,Norwegian Geotechnical Institute |
Schjetne K.,Norwegian Geotechnical Institute
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2013
Abstract: The paper presents diagrams of the (1) drained and undrained effective stress friction angles of sand; (2) dilatancy angle of sand; (3) parameters in a nonlinear constrained modulus expression for virgin loading, unloading, and reloading on sand and silt; and (4) diagrams with the coefficient of permeability for sand, silt, and clay. The database parameters are suitable for preliminary assessments or applications when assumed parameters are acceptable. The database can also be helpful in planning and interpreting site-specific tests and in reducing the number of site-specific tests. For important projects the parameters should be determined by site-specific tests. © 2013 American Society of Civil Engineers.
Cuisiat F.,Norwegian Geotechnical Institute |
Skurtveit E.,Norwegian Geotechnical Institute
Journal of Structural Geology | Year: 2010
The generation of clay smears along faults in uncemented sediments has been studied through laboratory experiments in a newly developed high stress ring shear apparatus. The main objective is to investigate basic mechanisms involved in the deformation process of sediments during faulting and formation of clay smears. The experimental test program comprises ring shear tests on sand with embedded clay segments (sand-clay sequence) under constant effective normal stress. Visual inspection of the samples after testing, analyses of thin sections and permeability measurements across the shear zone are used to characterise geometrical continuity, thickness and sealing potential of the smear. Deformation processes such as grain reorientation, clay smear and cataclasis are identified from the tests. The complexity of the shear zone is observed to increase with the effective normal stress applied to the specimen and the number of clay segments used in the ring (multilayered sand-clay sequences). At low effective normal stress, in clay-rich sediments, clay smear is the most efficient mechanism for permeability reduction. The permeability across the smear decreases with ring rotation (or shear displacement) and effective normal stress. A maximum decrease of two orders of magnitude compared to the permeability of the surrounding sand is observed after 90° rotation under 10.5 MPa effective normal stress. Sand-sand juxtaposition shear is dominated by grain rolling causing only minor permeability reduction. At high effective normal stress, permeability measurements across clay smear and sand-sand juxtaposition yield similar values indicating that the permeability reduction is dominated by grain size reduction in the sand. © 2009 Elsevier Ltd.