Engineering properties of Norwegian peat for calculation of settlements

publishedVersio

Estimating shear wave velocity with the SCPTu and Bender element

The shear wave velocity (vs) is an important soil and rock property that can both be used in several geotechnical problems including for evaluation of dynamic properties of soils as well as in determining the maximum value of soil stiffness at small strain. This property is also seen to give good correlations with other soil parameters used in settlement and stability analyses. The Norwegian Public Roads Administration (NPRA) has recently invested in equipment to measure this fundamental soil property both in the laboratory using bender elements and out in the field using a seismic CPTu (SCPTu). NPRA has also developed internal procedures and techniques to standardize logical interpretations. To assist with this standardization procedure, NPRA has conducted soil investigations at a site in Fredrikstad municipality in the southern part of Norway. The investigations included SCPTu and extraction of high quality mini-block samples. The shear wave velocity is estimated after consolidation in the triaxial apparatus. The laboratory program was done right after the sample extraction and repeated on stored samples a couple of weeks later. Comparison of vs measured in the laboratory was then made with the field measurements with SCPTu. The work gives comparison of the field and laboratory measurements. Correct interpretation approaches are necessary for the laboratory tests as these are found to be more sensitive to small changes in experimental conditions than the SCPTu. Recommendations on how to reduce discrepancies between laboratory and field data are given

Norway's National GeoTest Site Research Infrastructure (NGTS)

publishedVersio

Back-calculation of pillar foundation for Skjeggestad Bridge

In 2015, a landslide incapacitated the expressway E18 in southern Norway because one of the large foundation pillars of the southern lane of Skjeggestad Bridge near Mofjellbekken failed. This accident immobilised throughway traffic between Oslo and southern Norway for 17 months until the bridge became fully operational again. This paper focuses on the adjacent bridge pillar of the northern lane which experienced substantial displacements during the landslide. The paper presents the back-calculated reserve capacity of the pile foundation immediately after the landslide occurred. This was essential to establish the impact of the slide on the foundation capacity and evaluate the safety of the northern lane for traffic. The paper is a companion of the paper presenting the two-and three-dimensional analyses of the landslide that occurred in Mofjellbekken. The software Trimble NovaPoint Geosuite was used for an integrated design approach examining the soil layering, selecting the soil parameters and doing capacity calculations on the pile foundation (and calculating the stability analyses in the companion paper). The soil parameters were selected based on a statistical analysis of the key parameters and for cases with insufficient information correlations on similar soils are used. Two modelling approached were investigated to simulate the slide impact on the piles. The sensitivity of the lateral performance of the piles to soil stiffness was investigated based on recommendations from different guidelines. The implication of these analyses on pile cross-sectional utilization is discussed.publishedVersio

3D stability analyses of Skjeggestad landslide

In 2015, a sudden landslide caused the failure of one of the pillars supporting the southern lanes of the Skjeggestad Bridge near Mofjellbekken on Expressway E18. The transportation corridor was closed to traffic for 17 months. To investigate the cause of the failure, an assessment of slope stability is necessary. Usually, limit equilibrium analysis of the middle two-dimensional (2D) cross-section is modelled. The Skjeggestad landslide geometry was not close to a 2D case, and three-dimensional (3D) modelling is more appropriate to analyse the slope. The paper calculates the stability of the slope that failed and compares the results of 3D finite element analyses with classical limit equilibrium and 2D finite element analyses. The analyses were run in the Novapoint GeoSuite Stability software. The soil parameters, including their statistical values, were obtained with the GeoSuite Soil Data Interpretation (SDI) module. A companion paper at this conference analyses the pillar neighbouring the landslide with the module GeoSuite Piles. The paper illustrates the importance of 3D effects in a stability analysis. The results of the analyses also illustrate the need to include appropriate consideration of any strain-softening and spatial variation of soil properties.publishedVersio

Back-calculation of pillar foundation for Skjeggestad Bridge

In 2015, a landslide incapacitated the expressway E18 in southern Norway because one of the large foundation pillars of the southern lane of Skjeggestad Bridge near Mofjellbekken failed. This accident immobilised throughway traffic between Oslo and southern Norway for 17 months until the bridge became fully operational again. This paper focuses on the adjacent bridge pillar of the northern lane which experienced substantial displacements during the landslide. The paper presents the back-calculated reserve capacity of the pile foundation immediately after the landslide occurred. This was essential to establish the impact of the slide on the foundation capacity and evaluate the safety of the northern lane for traffic. The paper is a companion of the paper presenting the two-and three-dimensional analyses of the landslide that occurred in Mofjellbekken. The software Trimble NovaPoint Geosuite was used for an integrated design approach examining the soil layering, selecting the soil parameters and doing capacity calculations on the pile foundation (and calculating the stability analyses in the companion paper). The soil parameters were selected based on a statistical analysis of the key parameters and for cases with insufficient information correlations on similar soils are used. Two modelling approached were investigated to simulate the slide impact on the piles. The sensitivity of the lateral performance of the piles to soil stiffness was investigated based on recommendations from different guidelines. The implication of these analyses on pile cross-sectional utilization is discussed

3D stability analyses of Skjeggestad landslide

In 2015, a sudden landslide caused the failure of one of the pillars supporting the southern lanes of the Skjeggestad Bridge near Mofjellbekken on Expressway E18. The transportation corridor was closed to traffic for 17 months. To investigate the cause of the failure, an assessment of slope stability is necessary. Usually, limit equilibrium analysis of the middle two-dimensional (2D) cross-section is modelled. The Skjeggestad landslide geometry was not close to a 2D case, and three-dimensional (3D) modelling is more appropriate to analyse the slope. The paper calculates the stability of the slope that failed and compares the results of 3D finite element analyses with classical limit equilibrium and 2D finite element analyses. The analyses were run in the Novapoint GeoSuite Stability software. The soil parameters, including their statistical values, were obtained with the GeoSuite Soil Data Interpretation (SDI) module. A companion paper at this conference analyses the pillar neighbouring the landslide with the module GeoSuite Piles. The paper illustrates the importance of 3D effects in a stability analysis. The results of the analyses also illustrate the need to include appropriate consideration of any strain-softening and spatial variation of soil properties