Dynamic loading of embankment, foundation and pavement structures results in particle breakage of the constituent granular materials, when the stresses imposed on their particles exceed their strength. This paper presents the results of a number of drained cyclic triaxial tests on loose, uniformly graded samples of Dogs bay carbonate sand. It is observed that particle breakage is dependent on stress level, cyclic stress ratio, and creep and is directly related to volumetric strain. Drained cycling increases volumetric strain and therefore more breakage occurs when larger numbers of cycles are imposed. The increase in particle breakage from one cycle to the next indicates that while particles may not be loaded to their full capacity in a given cycle, they can be crushed in subsequent cycles without any variation in the amplitude of cyclic loading.

The UK's transportation network is supported by critical geotechnical assets (cuttings/embankments/dams) that require sustainable, cost-effective management, while maintaining an appropriate service level to meet social, economic, and environmental needs. Recent effects of extreme weather on these geotechnical assets have highlighted their vulnerability to climate variations. We have assessed the potential of surface wave data to portray the climate-related variations in mechanical properties of a clay-filled railway embankment. Seismic data were acquired bimonthly from July 2013 to November 2014 along the crest of a heritage railway embankment in southwest England. For each acquisition, the collected data were first processed to obtain a set of Rayleigh-wave dispersion and attenuation curves, referenced to the same spatial locations. These data were then analyzed to identify a coherent trend in their spatial and temporal variability. The relevance of the observed temporal variations was also verified with respect to the experimental data uncertainties. Finally, the surface wave dispersion data sets were inverted to reconstruct a time-lapse model of S-wave velocity for the embankment structure, using a least-squares laterally constrained inversion scheme. A key point of the inversion process was constituted by the estimation of a suitable initial model and the selection of adequate levels of spatial regularization. The initial model and the strength of spatial smoothing were then kept constant throughout the processing of all available data sets to ensure homogeneity of the procedure and comparability among the obtained V S sections. A continuous and coherent temporal pattern of surface wave data, and consequently of the reconstructed V S models, was identified. This pattern is related to the seasonal distribution of precipitation and soil water content measured on site.

A geophysical investigation was carried out after the failure of an important railway embankment in the south-east of Ireland. The embankment, which had a long-term history of stability problems, was studied using a combination of ground-penetrating radar (GPR), electrical resistivity tomography (ERT), multichannel analysis of surface waves (MASW) and geotechnical testing. A significant thickening of the ballast layer around the failure location was observed using GPR, which confirmed the existence of an ongoing stability problem in the area. ERT profiles determined the presence and spatial extent of a significant layer of soft clay both beneath and to the east of the embankment, which could have a major impact on its long-term stability. ERT also detected steeply sloping bedrock close to the failure zone that is likely to have contributed to the long-term settlement of the embankment, which necessitated frequent re-ballasting. MASW confirmed the presence of the steeply sloping bedrock in addition to determining the low stiffness (G max ) values of the embankment fill.High quality sampling of the soft clay deposit was undertaken and strength and compressibility tests revealed the importance of this layer to both the on-going serviceability problems evident for the original embankment and the stability problems encountered by the remodelled section.

Publication informationGéotechnique, 60 (11) (Kleven et al., 1986), and the normalised change in void ratio, Δe/e 0 (Lunne et al., 1997). Most of these approaches, however, require reconsolidation back to in-situ stresses, a process that may require a number of days of testing. This is a particular problem for offshore sampling, where rapid assessment of sample quality could significantly improve efficiency.A number of studies in recent years have observed that laboratory determined shear wave velocities (V s ), and corresponding small strain shear modulus, G max :are generally lower than the in-situ equivalent, and have attributed this difference to sampling disturbance (Shiwakoti et al. 2000; Porcino & Ghionna 2004). These studies involved reconsolidation of laboratory specimens back to their in-situ stress, before measurement of V s . For a quick assessment of sample quality, Hight & Leroueil (2003), Nash (2003) and Landon & DeGroot (2007) used portable bender element kits to measure V s , immediately after removal from the subsurface on unconfined samples. Hight & Leroueil (2003) also suggested simultaneous soil suction (u r ) measurements, enabling differences between unconfined and in-situ stress state to be taken into account.The use of suction measurements for sample quality evaluation was introduced by Ladd & Lambe (1963), who proposed using the ratio u r /σ' ps to evaluate disturbance, where σ' ps is the effective stress for a "perfect" sample. Calculation of σ' ps is, however, not straightforward and requires knowledge of Skempton's pore pressure parameter, A u 3 (consequent to the release of deviatoric stress), and K 0 (coefficient of earth pressure at rest). Authors such as Tanaka et al. (1996) DESCRIPTION OF SITES AND TECHNIQUESThe soft soils investigated during this study were located at Onsøy in Norway and at Ballinasloe and Bogganfin in Ireland (Table 1). A number of samplers of varying quality were used, the dimensions and features of which are given in Table 2. Onsøy, NorwayThe Onsøy test site is the main soft clay research site used by the Norwegian Geotechnical Institute (NGI). Onsøy is underlain by an extensive deposit of uniform marine clay, as described by Lunne et al. (2003). 4In this paper comparisons are made between Sherbrooke block, 76mm steel and 54mm composite piston samples at two depths (approximately 10m and 13m). The Scandinavian displacement approach was adopted for the piston sampling, wherein the sampler (with the piston in front of the sampling tube) was pushed down to the desired depth without preboring. Ballinasloe and Bogganfin, IrelandThe Ballinasloe and Bogganfin test sites (Donohue, 2005), located in the midlands of Ireland, are both underlain by post glacial lacustrine clay. Although generally uniform, the soils contain some thin silt laminations (1mm to 2mm). Testing TechniquesIn-situ V s measurements were obtained from the seismic cone (SCPT -Eidsmoen et al., 1985) Measurements of V s and u r were performed on all samples either immediately after extrusion...

A database of research quality CPTU and shear wave velocity information for Norwegian marine clays has been assembled so as to study the small strain stiffness relationships for these materials and to examine the potential use of CPTU and V s data in combination for the purposes of characterising these soils. Data for sites where high quality block sampling was carried out have mostly been used.Improvements have been suggested to existing correlations between G max or V s and index properties for these soils. Recent research has shown that CPTU q t and especially u 2 and V s can be measured reliably and repeatably and are not operator or equipment dependant. Therefore a new soil classification chart involving Q t and normalised shear wave velocity (V s1 ) or V s1 and Δu/σ v0 ' is presented. Using this chart it is possible to clearly distinguish between clays of different OCR.

The Ripley Landslide is a small (0.04 km2), slow‐moving landslide in the Thompson River Valley, British Columbia, that is threatening the serviceability of two national railway lines. Slope failures in this area are having negative impacts on railway infrastructure, terrestrial and aquatic ecosystems, public safety, communities, local heritage and the economy. This is driving the need for monitoring at the site, and in recent years there has been a shift from traditional geotechnical surveys and visual inspections for monitoring infrastructure assets toward less invasive, lower cost, and less time‐intensive methods, including geophysics. We describe the application of a novel electrical resistivity tomography system for monitoring the landslide. The system provides near‐real time geoelectrical imaging, with results delivered remotely via a modem, avoiding the need for costly repeat field visits, and enabling near‐real time interpretation of the four‐dimensional electrical resistivity tomography data. Here, we present the results of the electrical resistivity tomography monitoring alongside field sensor‐derived relationships between suction, resistivity, moisture content and continuous monitoring single‐frequency Global Navigation Satellite System stations. Four‐dimensional electrical resistivity tomography data allows us to monitor spatial and temporal changes in resistivity, and by extension, in moisture content and soil suction. The models reveal complex hydrogeological pathways, as well as considerable seasonal variation in the response of the subsurface to changing weather conditions, which cannot be predicted through interrogation of weather and sensor data alone, providing new insight into the subsurface processes active at the site of the Ripley Landslide.

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Satellite Interferometric Synthetic Aperture Radar (InSAR), geological data and Small Unmanned Aerial Vehicle (SUAV) surveying was used to enhance our understanding of ground movement at five areas of interest in Northern Ireland. In total 68 ERS-1/2 images 1992-2000 were processed with the Small Baseline Subset (SBAS) InSAR technique to derive the baseline ground instability scenario of key areas of interest for five stakeholders: TransportNI, Northern Ireland Railways, Department for the Economy, Arup, and Belfast City Council. These stakeholders require monitoring of ground deformation across either their geotechnical infrastructure (i.e., embankments, cuttings, engineered fills and earth retaining structures) or assessment of subsidence risk as a result of abandoned mine workings, using the most efficient, cost-effective methods, with a view to minimising and managing risk to their businesses. The InSAR results provided an overview of the extent and magnitude of ground deformation for a 3000 km 2 region, including the key sites of the disused salt mines in Carrickfergus, the Belfast-Bangor railway line, Throne Bend and Ligoniel Park in Belfast, Straidkilly and Garron Point along the Antrim Coast Road, plus other urbanised areas in and around Belfast. Tailored SUAV campaigns with a X8 airframe and generation of very high resolution ortho-photographs and a 3D surface model via the Structure from Motion (SfM) approach at Maiden Mount salt mine collapse in Carrickfergus in 2016 and 2017 also demonstrate the benefits of very high resolution surveying technologies to detect localised deformation and indicators of ground instability.