Tom Lunne

• Norwegian Geotechnical Institute

The article presents the concept of determining constrained modulus— M 0 , initial shear modulus— G 0 , Young modulus— E , and rigidity index— I R on the basis of parameters from static penetration tests CPTU (Piezocone Penetration Testing), SCPTU (Seismic Piezocone Penetration Testing) and dilatometer tests DMT (Flat Dilatometer Test), SDMT (Seism...

The small strain shear modulus (Gmax) of soil is an important geotechnical parameter for the design of support structures for offshore wind foundations, such as monopiles. In-situ measurement of shear wave velocity (Vs) is preferred for deriving Gmax, however it is not standard to perform such measurements at each WTG location for a large offshore...

Current practice in the offshore wind industry is to utilise existing CPTU soil behavior charts to identify soil type (e.g., clean sands to silty sands, sand mixtures, clay etc.). The charts identify drained clean sands and undrained clays; however there are limitations detecting silty soils. Accordingly, indication of soil behaviour is needed to d...

CPTUs carried out at standard rate (2.0 cm/sec) occur under conditions that range from fully undrained in clay to fully drained in clean sand. For intermediate soils partially drained conditions may occur which affect the CPTUs response (qt, u2) and complicate interpretation. Variable rate CPTU testing has been pursued in the last 20 years as one o...

Cone penetrometer tests (CPTU) are used extensively for offshore soil characterization. There are established correlations between CPTU parameters and relative density (Dr) for clean sand, but studies on Dr correlations for sand with fines content are not well-exposed. As part of a joint industry project (CSi), a dedicated programme for CPT-based D...

Large flexible calibration chambers (CC) to evaluate and develop interpretation methods for cone penetration tests (CPT) in cohesionless soils have been used since the late 1960s. Nevertheless, only average boundary stress values are known in almost all tests already performed. Tactile Pressure Sensors represent a useful tool to assess the stress d...

The relative density is an important state parameter in the determination of engineering properties of marine sands. Existing industry-acknowledged cone penetration test (CPT) correlations to relative density have been developed almost exclusively from the results of calibration chamber testing performed at stress levels higher than 50 kPa. A few s...

This article contains the analysis of the correlation between the cone resistance qc from CPTU tests and shear modulus G0 determined from seismic tests SDMT and SCPTU. The analysis was performed for sands located in Poland, characterised by differential grain size distribution and origin. The significant impact of the independent variables; grain s...

When using initial deformation from oedometer tests to quantify sample disturbance, a correction for false deformation is sometimes needed. A method to determine this false deformation is presented.

Five different cone penetrometers from different manufacturers have been used in comparative testing program at the Norwegian GeoTest site (NGTS) on silt in Halden, Norway. The influence of cone type on the standard CPTU parameters is quantified. The corrected cone resistance shows approximately the same level of scatter as the penetration pore pre...

Three series of sampling with thin-walled samplers, with and without inside clearance and without a piston, have been performed in a very soft organic clay deposit. The penetration and retrieval forces were measured throughout the operation, thus contributing to a clearer understanding of the sampling process. The measured forces show the importanc...

Throughout the history of soil mechanics, the use of test site has been very important, in a range of soil types. The sites have been used for developing new and improved equipment and methods for soil characterization in terms of in situ testing, sampling and laboratory testing. The test sites have also been very useful for trying out or verifying...

Benchmarking is of significant importance in geological and geotechnical engineering, for testing and verifying innovative soil investigation methods and foundation solutions. This Special Issue aims to present detailed characterization of a wide range of natural soils used for benchmarking in geological and geotechnical engineering that was presen...

Hydraulic soil properties, and in particular the hydraulic conductivity, is important in a number of geotechnical design cases. However, attention is often drawn towards the method of analysis rather than the quality and validity of the hydraulic properties used as input. Intact samples of sand or silt are difficult or impossible to obtain, and pre...

Intact sand samples are difficult to retrieve due to the non-cohesive nature of the material. In order to carry out advanced laboratory tests, sand specimens are commonly reconstituted to an estimated in situ relative density derived typically from empirical correlations from cone penetration tests (CPTs). The most common specimen reconstitution te...

This paper presents a summary of the geotechnical engineering properties of low to medium overconsolidation ratio offshore inorganic clays derived from a high quality database. These properties, such as preconsolidation stress and undrained shear strength, are required for design of most offshore infrastructure and for assessment of offshore geohaz...

A database of CPTU data in marine clays, including index parameters and preconsolidation stresses from oedometer tests is established. Correlations between CPTU data and preconsolidation stress or OCR were developed based on data from 7 offshore and 1 onshore marine clay sites. Laboratory data on SHANSEP parameters of clays are collected. The CPTU...

In the 1960s, NGI investigated numerous potential research sites and established the first Onsøy soft clay site in 1968. In 2016, the NGTS project established five research sites, one of which is the NGTS Onsøy soft clay site. The purpose of this paper is to provide a reference for further in-situ and laboratory testing at the site and easy access...

An extensive database of high-quality piezocone (CPTU) and laboratory oedometer test data on onshore and offshore clays worldwide has been established. The database covers a wide range of index parameters and overconsolidation ratios (OCR) in the range 1 to 5. The purpose is to derive general correlations to model preconsolidation stress in clays f...

Geotechnical design in clay areas in Norway is mainly based on piezocone (CPTU) tests results. Strength and stiffness parameters are usually derived from CPTU parameters and empirical correlations. In order to improve geotechnical design practice (e.g. more cost-effective solutions) and to reduce risks related to the occurrence of catastrophic even...

Known challenges exist with maximum (γdmax) and minimum (γdmin) dry unit weight measurements; the respective dry unit weight results depend very much on the method or standard used. A laboratory testing programme was completed to systematically determine and compare γdmax and γdmin values derived for six different sand types by using different meth...

A comprehensive field campaign was carried out on an aged, dense, over-consolidated sand in Cuxhaven, Germany. CPTs along with a suite of additional in-situ tests, including DMTs, PLTs, shear wave velocity measurements (SDMT and MASW), nuclear densometer, manual drive-in cylinder, temperature, suction and volumetric water content testing were perfo...

The Norwegian GeoTest Site project (NGTS) established five research sites in Norway in 2016. The sites are referred to as sand, soft clay, quick clay, silt and permafrost. The project is funded by the Research Council of Norway and the aim of the project is to establish, characterize, share digital data and manage the use of the test sites in the c...

Tests on Onsøy clay (Ip = 24–27%) were performed to study the effect of sample disturbance on undrained static and cyclic shear strength. Samples with different degree of disturbance from sampling were used and parallel sets of monotonic and cyclic undrained laboratory tests were performed on block and 54 mm composite piston samples. A silty Dramme...

The Onsøy and Sarapuí II soft clays have been studied for a number of years. In particular , piezocone tests with different rates have been conducted at both sites. Since the plasticity index and the coefficient of consolidation-which play important roles in the rate effect-are different in Onsøy and SarapuÍ II clays, an interesting comparison is p...

Benchmarking is a key to the reliability of the solutions in geotechnical engineering, both for testing and verifying innovative soil investigation methods and verifying and calibrating foundation solutions. NGI and its partners, NTNU, SINTEF, UNIS and the Nor-wegian Public Roads Administration (NPRA), received funding from The Research Council of...

It is widely recognized that stress history is important and affects the stress-strain and strength behaviour of sands. Since undisturbed sand samples are almost impossible to obtain at an affordable cost, pre-shearing or pre-conditioning of reconstituted sand specimens is commonly justified by the fact that it simulates stress his-tory while corre...

The Norwegian GeoTest Sites infrastructure project, with funding from The Research Council of Norway, is a national research facility for geotechnical research. The infrastructure comprises five test sites in different soils located in Norway and on the Svalbard territory north of Norway. The data collected at these sites will be collated in a web-...

The paper contains the analysis of the influence of overconsolidation effect on the values of constrained moduli, assumed by means of two most popular in situ advanced tests. The tested soils included two geological formations: normally consolidated tills of the Pomeranian phase and overconsolidated tills of the Posnanian phase. The overconsolidati...

The preconsolidation stress (pc') is determined from high-quality oedometer test results by a variety of interpretation methods. Sample quality in the database varies from very excellent to fair (i.e. class 1-2). Results show that the five methods applied give very similar pc' values when the samples are of good quality, with pc' varying up to 14%...

Shear wave velocity (Vs) and the related small strain shear modulus (Gmax) are essential soil parameters for static and dynamic analysis of soil deformation. They can also be used as a basis for non-destructive assessment of sample quality. While the benefit of in-situ measurement of Vs is apparent, only few methods such as seismic cone (SCPTU) and...

In 1996, a retrogressive landslide claimed four lives near the village of Finneidfjord, northern Norway. Since then, the area has been developed into a prime natural field laboratory for investigating submarine slope instabilities. Research activities adopt an integrated approach in which we aim to characterize the slip planes involved in the lands...

Challenges with the measurements of minimum and maximum dry unitweights, and their dependency on the method or Standard used, are well known. A laboratory testing programme has been carried out to systematically determine the minimum and maximum dry unit weights of 5 different sands using different Standards and in-house methods. Minimum and maximu...

This study presents empirical correlation between shear wave velocity and relative density established from triaxial tests with bender elements on North Sea sands. The correlation is applied on in-situ locations with available P-S-Logging and CPT data. The resulting relative densities are compared. The results are generally in good agreement and re...

High plasticity deepwater clays are common in Gulf of Guineas (GoG), Offshore Africa. These clays normally have a very high water content. In addition to the in situ static and cyclic shear strength of the high plasticity clays, remoulded behavior of the high plasticity clays is discussed in this paper. Results from thixotropy tests, reconsolidated...

A new piston sampler has been developed for use with a Remotely Operated Seafloor Drilling System (ROSDS). The aim was the design of a sampler that provides high quality samples of soft to very firm clays with a recovery of at least 90%. A systematic review of all the variables influencing the sample quality was conducted and the results were consi...

Petronas Carigali Sdn Bhd (PCSB) manages about 150 existing platforms at various sites across South China Sea. Integrity reassessment on these existing structures using non-linear pushover analyses has frequently indicated lateral foundation failure at collapse. However to date there has been no physical observations of foundation failures. Foundat...

Gas migration along wells from reservoir formations to shallow sub-seabed strata was identified to occur at a field, offshore Malaysia. Since 1993 numerous shallow gas kick events had occurred in the vicinity of the platform designated in this paper as Platform DB, at gas charged layers of 60m and 90m below mudline. The occurrence of shallow gas ki...

The paper describes operational details and performance results of a new deepwater seismic probe for measuring the in situ shear wave velocity (Vs) of offshore soils. The system uses a seismic cone that incorporates two sets of geophones located 1 m apart in the probe so as to allow for true-interval determination of the in situ Vs profile. The sys...

A literature survey has provided quite variable results with respect to rate effect on cone penetration test(CPT) in sand. Most of the available data refer to the penetration rate in the range 2 mm/s – 20 mm/s, and show some rate effect. The analysis of the data shows that the factors controlling rate effect on CPT in sand are excess pore pressure...

Two soil investigations were performed in soft, lightly overconsolidated clays in 1,300m of water depth. This paper will review and compare the results of these investigations and the subsequent onshore laboratory testing, in particular focusing on the quality of the samples and the performance and efficiency of the seafloor based drilling system t...

For the last 40 years, the CPT has played a key role in offshore soil investigations, mainly in connection with oil and gas development, but also for other purposes. The offshore application of CPT has been an important factor with regards to development of equipment, data processing and interpretation. Each of the following aspects are discussed i...

It has been reported in the literature that net cone penetration resistance is normally higher than the penetration resistance measured using full-flow cylindrical (T-bar) or spherical (ball) penetrometers, and also that the ball penetration resistance is generally very close to the T-bar penetration resistance. In this paper, a worldwide high-qual...

Offshore developments for hydrocarbon resources have now progressed to water depths approaching 3000 m, with geotechnical design increasingly focused on soft sediments in the upper 30 m or so of the seabed. Due to the difficulties and high cost in recovering high-quality samples from deepwater sites, there is increasing dependence on in situ testin...

Stress history is usually determined by interpreting the results of oedometer tests to obtain the preconsolidation stress using traditional methods such as those proposed by Casagrande and Janbu. Both these methods are based on the assumption that the soil experiences a change in stiffness, from a stiff response to a soft response, close to the pre...

In summary, application of the Pacheco Silva (1970) method to the highly overconsolidated clay samples has shown that the method is simple to use and results in consistent values of preconsolidation stress provided the straight line portion of the virgin compression curve can be defined. The authors agree with Dr. Clementino that the method is inde...

After many decades of research, the issue of sample disturbance is still important as regards to determining reliable and representative soil parameters for foundation design in soft clays. Parallel laboratory tests have been carried out on high-quality block samples and ordinary piston tube samples from 12 deposits of soft Norwegian marine clays....

Vane shear strength and cone resistance for Scandinavian soft to medium stiff clay has been compared for six different sites in Norway and Sweden.At five of the sites, three in Drammen, one in Onsøy, and one in Gøteborg, the clays have been sedimented in an entirely marin environment. At the Skå-Edeby site the conditions have been marine-brackish o...

Data have been reviewed from sites in Europe and North and South America as well as published data from South Africa. The review has concentrated on dissipation data from piezocone tests (CPTU) to compare predicted coefficient of consolidation and permeability values using published interpretation techniques with available reference values. The res...

For offshore drilling, and in particular when drilling from fixed platforms in deep waters, the mud pressure will be high compared with the hydraulic fracture pressure (i.e., the formation strength) close to the sea floor. The first casing (the conductor) should therefore be installed to a depth where the formation strength is sufficient to prevent...

As a joint research project sponsored by the French–Norwegian Foundation for Scientific and Industrial Research, the Norwegian Geotechnical Institute, Geodia/Geocean, and École Polytechnique have carried out in the summer of 1990 a series of special in situ pressuremeter and cone penetration tests at a permafrost site in Longyearbyen, Svalbard. The...

Results of 43 load tests on driven and jacked piles performed at eight calyey sites have been back-analysed using piezocone test data. A method to evaluate the axial capacity of piles has been proposed in which the pile unit skin friction and the unit end bearing resistance are computed from the net corrected cone resistance, q net . Correlation fa...

Difficulties in obtaining high-quality soil samples from deepwater sites have necessitated increasing reliance on piezocone, T-bar and ball penetration tests to determine soil properties for design purposes. This paper reports the results of an international collaborative project in which a worldwide high-quality database of lightly over-consolidat...

Methods for the testing of weak soils, and characteristic features of the extraction of undisturbed specimens are examined. The effect of soil-sample disturbance on characteristics is evaluated.

This paper describes geology, soil profiles and geohazards for typical deep water areas, identifies design issues, calculation procedures and required soil parameters for geotechnical design of deep water structures and slope stability evaluations, shows how geology and geohazard phenomena can be identified by geophysical and geological methods, an...

With support from the Norwegian Deepwater Programme - Seabed Project NGI developed criteria for design of a new deepwater seabed sampler. The aims of the design was to have a sampler that can penetrate 15 - 20 m below seabed in 2000 m, with at least 95 % recovery and sample quality similar to what can be obtained with a thin wall piston sampler in...

Undrained triaxial and direct simple shear tests on samples reconsolidated to the in situ effective stresses and oedometer tests have been carried out on standard piston tube and on high quality block samples from 12 deposits of soft Norwegian marine clays. Based on the results of a selected number of these tests, empirical procedures for estimatin...

A comparative study of the NGI Direct Simple Shear Test (DSST) and the Mikasa Direct Shear Test (DST) is reported. Samples from Norwegian Drammen clay and Japanese Ariake clay were subjected to both types of test. An evaluation of these test results and a theoretical consideration on the different shearing mechanisms has shown that although the DST...

The paper aims at providing a case-study of uncertainty-based characterisation of selected engineering parameters in Troll marine clay. Second-moment uncertainty characterisation for data from laboratory and in-situ tests is performed. First-Order Second-Moment (FOSM) approximation is applied for probabilistic second-moment characterisation of deri...

The Troll site is underlain by a thick deposit of uniform marine clays and glacial tills. Though most of the work reported here was related to the development of a large CONDEEP concrete gravity structure, which at the time of its installation was the largest in the world, the ground conditions encountered apply across a wide area of the Norwegian...

A cost efficient way of investigating shallow sediments and for collecting soils data for many offshore geotechnical problems, e.g. anchoring of floating structures with suction piles or evaluation of submarine slope stability, is to carry out seabed sampling to say 25 m below seabed and in addition perform seabed CPTUs to say 40 m. Based on a revi...

New correlations between various CPTU factors, undrained shear strength and overconsolidation ratio have been developed for soft to medium stiff clays. The correlations are based on comparing the CPTU results against undrained traxial compression strength and preconsolidation pressure determined on block samples of very high quality taken with the...

The results of a pilot study investigating correlations between index tests and soil design parameters for offshore clays are presented. An important objective of the study is to develop a database consisting of high quality laboratory data from tests conducted in a consistent manner. The database includes ten sites from locations in the Atlantic O...

The Sherbrooke block sampler has been used at Drammen clay site in Norway. Standard piston samples have been obtained at the same site by the 54 mm Norwegian sampler and 75 mm Japanese sampler. Subsequent laboratory tests(CAUC triaxial and CRS odometer) clearly show the superior quality of the block samples compared to the piston samples. The effec...