As an important part of blast hole filling in blasting engineering, rapid setting taphole clay material has been paid attention by many scholars. Although curing time is an important factor affecting the mechanical properties of quick setting taphole clay materials, scholars have little research on quick setting taphole clay materials. This study investigated the influence of curing time on the mechanical properties of rapid-setting taphole clay materials, analyzed the variation pattern of mechanical strength during the increase of curing time, and employed techniques such as XRD and SEM-EDS to study the impact of curing time on the crystalline phase transformation, microstructure, and element distribution of taphole clay materials. The results revealed that with the increase of curing time, all mechanical strengths of the taphole clay materials increased significantly, with a faster growth rate within the first 6 h and stabilization around 24 h. The main hydration products of the taphole clay materials are calcium carbonate and ettringite, whose contents increase with curing time, promoting the hydration process and enhancing mechanical strength. The internal structure of the material becomes denser with increasing curing time, resulting in decreased porosity, specific surface area, the average pore size and total pore volume, and the formation of a dense spatial structure, which explains the trend of strength change. This study is of great significance for selecting optimal plugging materials and curing times for mines in China to achieve efficient blasting operations.

Abstract The report on the Gjerdrum landslide highlights the need to detect quick clay without sampling. Although multiple dimensionless-number-based methods have been developed, in Norwegian industrial practice, decisive detection of quick clay relies on sampling followed by laboratory testing. This is both time-consuming and expensive. It would be a great advantage if accurate identification of quick clay could be efficiently made by some sort of geotechnical sounding in the field. Ideally such a new sounding method should be based on modifying some conventional sounding equipment where a rod with an instrumented tip is pushed or drilled into the ground. The current paper addresses work based on modifying a Conical Penetration Test device (CPTU) for this purpose. Three different, modified penetrometer tips were fabricated and tested at several sites in Norway with quick clay. In addition, cyclic CPTU tests (using a conventional CPTU tip) were performed to investigate how repetitive movements remould the clay. The results show some improved remoulding in monotonic tests by using modified tips and by cyclic testing. Still, the results seem to indicate that the fully remoulded layer around the rod in quick clay is surprisingly thin, which may be part of the reason why remoulded shear strength typical for quick clay (<0,33kPa from fall cone test according to current Norwegian standard) could not be measured in the monotonic tests. Even after several cycles the cyclic tests show higher resistance than one intuitively would expect from moving the tip in a fully remoulded clay. Another important conclusion is that the CPTU devices used in our study have insufficient accuracy on sleeve friction. The o-rings connecting the sleeve to the rod introduce friction forces that prohibit measuring remoulded shear strengths in the order of 0,33 kPa or less. The preliminary results of our study will be used to develop a sounding tool that can both properly remould the clay and accurately measure remoulded shear strength.

Abstract Recent examples of catastrophic quick clay landslides in Norway have demonstrated that the risks posed by quick clay can be partly mitigated through systematic erosion monitoring schemes. Monitoring can be carried out by comparing multi-temporal digital elevation models generated from airborne LiDAR datasets. However, aircraft-based LiDAR campaigns are expensive, and surveys are typically conducted only every few years. In contrast, Uncrewed Aerial Vehicles (UAVs) equipped with LiDAR sensors offer a cost-effective alternative for frequent monitoring of surface conditions in localized areas. This paper presents a comparison of repeated UAV-borne LiDAR measurements used to detect and monitor erosion in quick clay areas, with close-range photogrammetry used as ground truthing. Results from two case studies in southeastern Norway demonstrate that UAV-borne LiDAR measurements can be conducted with increased spatial resolution (on the centimetre scale) and at a higher frequency than aircraft-based LiDAR measurements. The method enables more rapid detection of potential erosion or other terrain changes that could threaten the stability of slopes in high-risk areas. The paper also demonstrates how rapid analyses of repeated, topographic survey data can serve as an early warning tool for critical erosion in areas with quick clay. Such tools will help transition from today’s infrequently updated static hazard maps to a more dynamic hazard management approach.

Abstract A temporary monitoring and early warning system was organized during the response and recovery phase following a quick clay slide that occurred December 30, 2020, at Ask, Gjerdrum (Norway). The landslide left a steep and active scarp, ca. 1230 m long and 20 m high around a depleted zone. A monitoring system was established to warn rescue personnel, working below the scarp, about the possible occurrence of successive landslides. The scarp was initially monitored with visual observations (from ground) combined with drones (using both optical and thermal cameras). After a week, ground-based radars (InSAR) were also installed. The landslide scarp was monitored for two years. Successive landslides occurred in 60 days of the monitored period. One landslide was warned with the use of visual observations and about 20 landslides were detected and predicted with the use of radar. The radar was able to detect areas of accelerating velocities, typically in a period of a few hours prior to failure, with the total amount of deformation up to 10 mm. Ca. 145 slides of different size were mapped with the use of photos, video from drone, field observations and radar data, documenting spatial and temporal distribution, magnitude, type of mechanisms and acceleration for some of them. The largest successive slides occurred where there still was quick clay at the foot of the scarp and they remobilised the remoulded quick clay already present in the runout area. The slides occurred along the entire scarp, but mainly in the eastern and northern part, which can be explained by the steep slope gradient. Ground-based radar (InSAR) data has not been used for monitoring quick clay slide scarps previously, and it was uncertain if it would give valuable data. Radar was a very valuable tool and probably the most effective and reliable method for continually monitoring scarp deformations during search, rescue and mitigation works.

Abstract In 2021 the Norwegian Public Roads Administration (NPRA) initiated a project that aims to develop a new method for mapping and monitoring of quick clay hazards that affect our roads. The method is a pragmatic approach to evaluation of stability, where emphasis is given to qualitative assessment of slope stability, rather than quantitative methods such as stability calculations. Central to the methodology is emphasizing natural triggering mechanisms of quick clay landslides and assessing the extent to which they are present in an area. The method is based on elements from the Norwegian Water Resources and Energy Directorate (NVE) hazard classification of quick clay zones, while also drawing inspiration from an approach developed by the Ministère des Transports et de la Mobilité durable in Quebec, Canada (MTQ). The primary governing factors in this approach are to look for possibility of active erosion, earlier landslide activity and slope geometry. As part of the methodology, the project has developed a GIS (geographical information system) analysis to identify critical slopes with regards to height and inclination. In 2022 NPRA, NVE and the Geological Survey of Norway (NGU) collaborated on a field test which purpose was to test and assess the suitability of GIS analyses to identify possible triggering locations for quick clay landslides. A GIS analysis developed by NVE detects changes in the landscape from one year to another, while GIS analyses developed by NGU monitor fluvial erosion and local relief at the bottom of slopes. The field test showed that the new GIS analyses provided a highly accurate picture of slope activity in the investigated ravines. By assessing active erosion, landslide activity and slope geometry we aim to work more proactively, by systematically and efficiently prioritizing which areas need more detailed mapping, monitoring or security measures. GIS analyses will be used as a tool to help in measuring these factors in the many thousand quick clay areas in Norway.

Abstract Quick clays pose a serious threat for catastrophic landslides in Norway. The current approach for identifying and assessing quick clay landslide risk in Norway is time-consuming and costly. In response, this study presents preliminary results of an ongoing research project by the Norwegian Water Resources and Energy Directorate (NVE) to develop an innovative, data-driven methodology for proactively identifying areas potentially vulnerable to naturally triggered brittle and quick clay landslides. The proposed methodology utilizes modern technologies and available datasets, including digital terrain models, population data, geotechnical and geological soundings, and terrain change detection. Key steps include identifying areas susceptible for thick marine clay deposits, estimating streams’ water depth and erosion potential, computing the maximum release area for potential retrogressive landslides, assessing consequences in terms of affected infrastructure and population, and identifying erosion related terrain changes that may deteriorate the slope stability. The methodology is applied to a case study in southeast Norway. The results demonstrate the potential for this approach to rapidly prioritize vulnerable areas for further assessment and landslide mitigation. The data-driven and proactive nature of the methodology offers significant efficiency gains and resource savings compared to traditional assessment methods. In this paper, the implications of the new methodology for natural hazard management in Norway are described, highlighting the importance of data quality, integration, and continuous field validation is emphasized. Ongoing efforts aim to refine the models, incorporate additional factors, and move towards a more comprehensive risk-based approach to landslide mitigation.

Abstract Quick clay landslides pose significant threats to human lives, infrastructure, and the environment. This paper summarizes nearly three decades of mitigation work in the Skjelstadmark region in mid Norway, where extensive measures were implemented to reduce landslide risk along 28 km of river channels and tributaries. The mitigation strategy combined erosion control, slope relief, and counter fills, resulting in a substantial decrease in sediment transport and landslide activity. Environmental benefits included improved water quality and enhanced fish habitats. Socio-economic benefits were also significant, safeguarding lives, protecting infrastructure, and preserving agricultural lands. The cost-benefit analysis demonstrates the economic viability of these measures, highlighting the importance of proactive risk management. This study provides valuable insights into effective mitigation strategies for quick clay landslides, emphasizing the need for continued monitoring and maintenance to ensure long-term effectiveness.

Abstract Quick clay landslides are frequent events that can cause catastrophic consequences. They can result in loss of human life, economic losses, and environmental damage. These landslides exhibit retrogressive characteristics and high mobility, primarily triggered by human interventions that affect in-situ pore pressure or slope geometry. In Norway, a significant portion of the population lives in areas at risk of quick clay landslides, necessitating the development and implementation of effective hazard assessment and management strategies. To address this need, this study proposes a framework for an early warning system by monitoring the increase in pore pressure due to human intervention. The proposed framework is implemented on two slopes with poor stability conditions. The slopes were examined using pore pressure sensors installed at various locations and depths. Slope stability analyses were conducted using a limit-equilibrium-based model. The DSHANSEP method was employed to correlate increases in pore pressure with reductions in undrained shear strength, within the context of the Mohr-Coulomb failure criteria. A four-stage warning level identification is proposed based on the required safety level by Norwegian standards and guidelines. The proposed methodology for pore pressure sensor-based early warning system is found a reasonable approach for mitigating the risks associated with pore pressure increase on quick clay slopes.

Abstract Highly sensitive marine clays, referred to as quick clays, are characterized by extreme strain-softening behavior that can result in near total strength loss from small disturbances. This makes them a potential hazard for large retrogressive or progressive landslides. Identifying such sensitive soils is essential for assessing geotechnical risks in marine clay environments. In current Norwegian practice, identification of sensitive clays relies on laboratory tests where sample extraction and testing are both time-consuming and costly. A field investigation method is desired to efficiently screen and delineate zones for sensitive materials. For this the cone penetration test with pore pressure measurements (CPTu) is a strong candidate among available methods. In this work, data from 38 road projects across Norway is used, where laboratory test results have been linked to 277 CPTu tests. The data are divided into Brittle and Non-brittle materials based on their remolded undrained shear strength. Kernel density estimation (KDE) method is used to create density distribution models for these groups in three dimensions. Although the KDE models can be used directly to screen for sensitive materials, boundaries for selected density ratios between both models are triangulated to generate a visual representation of the resulting volumes. A method to classify CPTu data using triangulated models is presented, and examples of classification result are given.

Abstract The Swedish geotechnical institute, SGI, has the mandate to prevent and minimize the negative impact of landslides, erosion and contaminated sites. SGI work to minimize the risks for landslides and to reduce the effects of such events, which includes giving geotechnical support to local Rescue Services. This article presents two examples. The first example highlights the ongoing work along the Göta River Valley aimed at minimizing the landslide hazards. This area is one of the areas in Sweden most prone to landslides, which can affect both society and individuals. Moreover, the prerequisites of landslides will most likely increase with the changing climate. As a result of the mapping of landslide risks carried out by SGI in 2009-2011 [1], there are about 160 identified sub-areas along the river that need further investigation and possible mitigation measures. Many of the areas include quick clay. The Swedish Government has given SGI the task of reducing the risk of landslides along the Göta River Valley. This work is being done together with the Delegation for the Göta River, which consists of members from the municipalities affected, organisations and other government agencies. Since the start in 2018 SGI has built up an organisation to support the municipalities in the work of preventing landslides. The second example highlights SGI’s effort to support local Rescue Services, specifically the intervention following the quick clay landslide that occurred on 23rd September 2023 at the northern entrance to Stenungsund on the E6 motorway [2]. At 02.16 the on-call officer (geotechnical engineer) at SGI was contacted by SOS Alarm. Both southbound and northbound traffic were affected by the landslide. SGI decided that two geotechnicians should assist the rescue services at the site and that two geotechnicians should act as internal support to produce documentation, make assessments, and handle internal and external information requirements.

Abstract Accurate prediction of landslide susceptibility and retrogression potential is crucial for risk assessment of marine clay slopes. While Canadian and Norwegian practices generally align on the key factors controlling retrogressive landslides, they differ in the selection of threshold values. This study compares methodologies for assessing retrogression in sensitive clays. One Canadian approach compares the potential energy of a slope with the energy required to remold the clay during a landslide. It aims at identifying a threshold of potential energy above which the clay is sufficiently remolded to develop into a large retrogressive landslide. In this study, the Canadian approach is tested against a revised and updated database of Norwegian quick clay landslides. Due to relatively lower undrained shear strength and plasticity indexes, a higher threshold is suggested in Norway. Building on these findings, a new framework is proposed to predict the most likely landslide mechanism. When tested against the Norwegian database, the framework accurately predicted whether a sensitive clay slope was most susceptible to rotational, flake, or retrogressive landslides.

On the importance of mineralogy and geochemistry on the development of Norwegian quick clays – a review and compiled datasets

Abstract Quick clays are fine-grained soils with high sensitivity that transform into a liquid when remoulded. The deposition history directly impacts the composition and microstructure of natural clays. This study examines the morphology at the nanoscale of two different sensitive Swedish clays (Lödöse and Kärra clay) to establish a connection between the microscopic features and the macroscopic mechanical behaviour observed at their intact and remoulded state. Using in-line holotomography, the nano-scale imaging instrument at the ID16B beamline of ESRF is employed to capture nano-level features in the natural clay specimens. The results illustrate that the size of the silt grains and the macroporosity are smaller for Lödöse clay than for Kärra clay. This might indicate the higher sensitivity of Lödöse clay. Although the macroporosity of Kärra clay reduces by 32% after remoulding, the difference in macropores recorded after remoulding Lödöse clay is negligible.

Cultural activity and impact of extreme weather events revealed by ambient seismic noise and perspective on quick clay failure monitoring in Oslo, Norway

This study investigated the sorption, desorption, and trapping of 9,10 dimethylated anthracene (DMA), copper (Cu), and cadmium (Cd) onto quick clay (QC), focusing on the effects of temperature, salinity, and their environmental relevance. Sorption isotherms were generated at different temperatures (4, 10, and 20°C) and salinities (1 and 25g·L-1). Thermodynamic parameters were calculated to elucidate the underlying mechanisms. Isosteric heat of adsorption (ΔHX) was determined to assess the heterogeneity of adsorption sites. Isotherms results were processed using the Freundlich model to assess sorption and hysteresis parameters of QC. Kinetic studies revealed a rapid initial uptake of DMA followed by a slower logarithmic phase, reaching equilibrium within 1440min. The presence of the methyl group in DMA compared to non-methylated PAHs from other studies likely influences its adsorption rate. Temperature and salinity significantly impacted both the adsorption and desorption processes. Notably, Cd adsorption was nearly made ineffective with increasing salinity. Interestingly, Cu hysteresis index (HI) decreased from 1.57 to - 0.08 with increasing salinity, suggesting a shift from inner-sphere complexation at low salinity to outer-sphere complexation at high salinity. Conversely, DMA adsorption increased by 1.83-fold with increasing salinity, likely due to the salting-out effect. Thermodynamic analysis indicated a spontaneous and endothermic adsorption process driven by a positive entropy change (ΔS0). The ΔHX values supported physical adsorption as the dominant mechanism. The observed homogeneity in ΔHX values for DMA and Cd suggests consistent interaction with the clay surface, while the heterogeneity observed for Cu signifies a variation in adsorption site energies.

Abstract. The founder of soil mechanics, Karl Terzaghi, took the initiative in 1954 to contact the Danish engineer Laurits Bjerrum, requesting to meet. Terzaghi wanted to meet the engineer who had written a paper on the stability of the unusual Norwegian quick clays at the European Slope Congress in Stockholm. Bjerrum was 36 years old at the time, had a PhD and was already director of the NGI (Norges Geotekniske Institutt – Norwegian Geotechnical Institute). From his position as director of the NGI, he was actively involved in many varied consultancies, placing great value on the continuous interaction between practice and research. Bjerrum's strategy for establishing the NGI came from the experience of other research centres such as the BRS (Building Research Station) in Great Britain and Imperial College London. In addition, having lived through the Nazi occupation of Denmark, he was predisposed to be against the misuse of authority and established an open structure for the institute from its inception. Bjerrum was in close contact with the Norwegian Institution of Technology, and, in 1952, he succeeded in getting soil mechanics incorporated as a compulsory subject in the civil engineering degree. Subsequently, in 1960, the Chair of Soil Mechanics and Foundation Engineering was established. The first laboratory of this chair was equipped with material donated by the NGI. Bjerrum died young (54 years old), but he had built an excellent reputation through his work at the NGI and his contributions to international conferences, where he maintained a close relationship with the significant figures in geotechnics: Terzaghi, Skempton, Peck and Casagrande. He made regular trips to the USA, where he was a visiting professor at MIT (Massachusetts Institute of Technology) and received the highest international decorations.

The instability of quick clay is a contributing factor for landslides within Scandinavia, Canada, and Russia. The addition of salts into quick clay is known to improve the remoulded shear strength and liquid limit. In this study, the mixing of salts recycled from waste incineration fly ash into remoulded quick clay was studied and compared with the incorporation of pure salts for applications in salt wells and for excavation applications. The salts were added as solutions at low concentrations and as solids at high concentrations and stored for 1, 28 or 90 days before testing. Nearly all samples with added salts had a liquid limit that exceeded the water content and a remoulded shear strength, which exceeded 0.5 kPa. The pure potassium chloride had the largest effect, followed by the recycled chloride mixture with the highest concentration of K+. While a change in the geotechnical properties was immediately evident upon the mixing, the effect on the shear strength increased further with increasing storage time. The findings imply that the recycled salts may be used to improve the geotechnical properties of excavated soft clays during the handling and transport to landfills as a viable and low-emission alternative to cementitious binders.

The estimation of undrained shear strength ( ) from Cone Penetration Test with pore pressure measurement (CPTu) for two sites was investigated in this research. The CPTu cone parameters: net cone resistance ( ), excess pore pressure ( ) and effective cone resistance ( ) were used to estimate the for the two sites and the values obtained were compared with the undrained shear strength in triaxial compression ( calculated from Anisotropically Consolidated Undrained Compression (CAUC) triaxial test results. For the clayey silt site, the undrained shear strength from the CAUC tests are higher compared to the values obtained from the CPTu, and the highest correlation was obtained from the effective cone resistance parameter . For the quick clay test site, the value and were relatively the same and showed stronger correlation as compared to the clayey silt site. The measured from the cone parameter had the highest correlation. It was concluded that and yields good correlation with the CAUC results for the clayey silt and quick clay test sites respectively as compared to the other con parameters.

Abstract Multichannel analysis of surface waves (MASW) is a noninvasive active-source technique for determination of near-surface shear wave velocity (VS) profiles. Here we introduce and describe MASWavesPy, an open-source Python package for processing and inverting MASW data, whose design follows an object-oriented paradigm. To assess the performance of the new tool, measurements were conducted at four benchmark sites in Norway, characterized as silt, soft clay, silty sand, and quick clay. The results show that the VS profiles obtained with MASWavesPy compare well with those obtained previously at the respective sites using invasive, noninvasive and laboratory techniques. Furthermore, the efficiency and usability of the new package is superior to previous versions developed by same authors. The software can be accessed through the Python Package Index (PyPI) at https://pypi.org/project/maswavespy/ along with sample data. This work further explores the inter-session variability of MASW measurements for civil engineering applications at soft soil sites. For this purpose, repeated measurements were conducted over a 7-year period at a silty sand site in South Iceland and the recorded time series analyzed using the newly developed tool. The inter-session variability of the analysis results is reported in terms of Rayleigh wave phase velocity, interval VS profiles, and time-averaged VS for reference depths commonly used in practice.

The Trondheim and Gauldal areas in Mid-Norway are characterized by thick marine deposits from the ice age and deglaciation period. The following glacio-isostatic rebound has led to river incisions in the valleys and extensive landsliding and ravine erosion. This study is based on data from an upgraded Quaternary geological map of this region for the areas below the highest sea level after the last ice age, with a focus on landslide scars and ravines. The study has a multidisciplinary approach, which is important in order to get a good regional geological understanding of the ground conditions and the landscape development. This means that geological, geomorphological, geotechnical, geophysical and hydrogeological data are used. The study area is divided into six parts, based on natural topographical divisions and the distribution of landslide scars and ravines. Factors influencing the development of sensitive clay and the triggering of landslides are described for each area; these include sediment distribution, thicknesses and stratigraphy, bedrock topography, the degree of leaching of clay, groundwater conditions, the number, size and shape of landslides, and the distribution of rivers, streams and ravines. The study shows that the size, behaviour and erosional potential of the main river or stream influence the landscape development to a high degree. The erosional basis, stratigraphy and presence of bedrock are essential for leaching and the development of quick clay.