Observation of the rock slope thermal regime, coupled with crack meter stability monitoring

Mapping Intimacies ◽

10.5194/gi-2021-5 ◽

2021 ◽

Author(s):

Ondřej Racek ◽

Jan Blahůt ◽

Filip Hartvich

Keyword(s):

Rock Mass ◽

Monitoring System ◽

Rock Slope ◽

Global Radiation ◽

Environmental Parameters ◽

Radiation Balance ◽

Rock Types ◽

Novel Approach ◽

First Results

Abstract. This article describes an innovative, complex and affordable monitoring system designed for joint observation of environmental parameters, rock block dilatations and temperature distribution inside the rock mass with a newly designed 3-meter borehole temperature sensor. Global radiation balance data are provided by pyranometers. The system introduces a novel approach for internal rock mass temperature measurement, which is crucial for the assessment of the changes in the stress field inside the rock slope influencing its stability. The innovative approach uses an almost identical monitoring system at different sites allowing easy setup, modularity and comparison of results. The components of the monitoring system are cheap, off-the-shelf and easy to replace. Using this newly designed system, we are currently monitoring three different sites, where the potential rock fall may endanger society assets below. The first results show differences between instrumented sites, although data time-series are relatively short. Temperature run inside the rock mass differs for each site significantly. This is very likely caused by different aspects of the rock slopes and different rock types. By further monitoring and data processing, using advanced modelling approaches, we expect to explain the differences among the sites, the influence of rock type, aspect and environmental variables on the long-term slope stability.

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Integrated geophysical and geotechnical monitoring for multiscale rock mass damaging investigation at the Acuto Field-Lab (Italy)

10.5194/egusphere-egu21-9403 ◽

2021 ◽

Author(s):

Guglielmo Grechi ◽

Danilo D'Angiò ◽

Matteo Fiorucci ◽

Roberto Iannucci ◽

Luca Lenti ◽

...

Keyword(s):

Rock Mass ◽

Monitoring System ◽

Thermal Stresses ◽

Central Italy ◽

Jointed Rock ◽

Failure Behavior ◽

Rock Masses ◽

Geotechnical Monitoring ◽

Strain Monitoring

Rock mass damaging has become a topic of great interest in the engineering-geology research community during the last decades as it can significantly influence slopes stability. In this sense, the study of mechanics and dynamics of jointed rock masses represents a challenge because it will allow to better understand how external continuous and transient stressors can influence the short- to long-term stability controlling their pre-failure behavior. Consequently, the detection of permanent changes in physical and mechanical parameters, due to periodic or transient stressors, is an important target to mitigate the related geological risk as it can potentially lead rock masses to failure, especially when infrastructures and natural or cultural heritages are exposed elements. In this framework, the Acuto field laboratory (Central Italy) has been designed and implemented in 2016 within an abandoned quarry by employing an integrated geotechnical and geophysical monitoring system, with the aim of investigating how natural and anthropic conditioning factors could lead fractured rock masses to failure. The integrated monitoring system, which is installed on a potentially unstable 20-m3 jointed rock block, is composed of several strain devices (i.e., strain gauges -SG- and jointmeters -JM-), one fully equipped weather station, one rock thermometer, eight high-sensitivity microseismic uniaxial accelerometers and optical and InfraRed Thermal cameras. The acquisition of long-term monitoring time-series, coupling multimethodological approaches, allowed to establish cause-to-effect relationships among different environmental stressors and induced strain effects, highlighting the continuous action of thermal stresses on rock mass deformations both at the daily and seasonal timescales. In fact, while the analysis of thermal and strain monitoring data allowed to characterize the cyclic contraction and relaxation response of major rock fractures and microcracks to temperature fluctuations, the microseismic monitoring array was able to detect during thermal transient (i.e., freezing conditions) the occurrence of microseismic emissions potentially related to the genesis or progressive growth of pre-existing cracks.Starting from 2018, experimental activities at the Acuto field lab are supported by the &#8220;Dipartimento di Eccellenza&#8221; project of the Italian Ministry of Education Universities and Research funds attributed to the Department of Earth Sciences of the University of Rome &#8220;Sapienza&#8221;.&#160; In this framework, the Acuto filed laboratory will undergo a structural upgrade that will be aimed at the investigation of two new sectors of the abandoned quarry. These new sectors will be instrumented with innovative thermal profiles probe, fiber Brag grating sensors and traditional SG and JM for detailed stress-strain monitoring, acoustic emission sensors and high-frequency and low-frequency geophones for ambient seismic noise monitoring and microseismic events detection as well as accelerometers for evaluating the rock mass response in the case of seismic shaking. The main goal of such an improvement will be both technical and methodological, and will shed light on the application of integrated geophysical and geotechnical monitoring approaches in investigating the multiscale rock mass damaging process as well as the detection of rock mass failure precursors by using non-conventional combinations and configurations of geotechnical and broad-band geophysical devices.

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Microseismic activity analysis for the study of the rupture mechanisms in unstable rock masses

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-831-2010 ◽

2010 ◽

Vol 10 (4) ◽

pp. 831-841 ◽

Cited By ~ 56

Author(s):

D. Amitrano ◽

M. Arattano ◽

M. Chiarle ◽

G. Mortara ◽

C. Occhiena ◽

...

Keyword(s):

Monitoring System ◽

Rock Slope ◽

Western Alps ◽

Permafrost Degradation ◽

High Mountains ◽

Significant Damage ◽

First Results ◽

Microseismic Activity ◽

North Western

Abstract. Rockfalls are common instabilities in alpine areas and can cause significant damage. Since high mountains have been affected by an increasing number of these phenomena in the last years, a possible correlation with permafrost degradation induced by climate change has been hypothesized. To investigate this topic, a monitoring system, made of 5 triaxial geophones and 1 thermometer, was installed in 2007 at the Carrel hut (3829 m a.s.l., Matterhorn, North-western Alps), in the frame of the Interreg IIIA Alcotra project n. 196 "Permadataroc". The preliminary data processing relates to the classification of recorded signals, the identification of the significant microseismic events and the analysis of their distribution in time and space. The first results indicated a possible correlation between clusters of events and temperature trend, and a concentration of events in specific sectors of the rock mass. Research is still in progress. The recording of data for a longer period is planned to fully understand seasonal trends and spatial distribution of microseismic activity, and possible relations with permafrost degradation. Nevertheless, the preliminary observations prove that the monitoring system can detect noises generated by rock slope deformation. Once fully developed, this technique could become a helpful tool for early warning and preliminary stability assessments.

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Stability Assessment of the Excavated Rock Slope at the Dagangshan Hydropower Station in China Based on Microseismic Monitoring

Advances in Civil Engineering ◽

10.1155/2018/4567258 ◽

2018 ◽

Vol 2018 ◽

pp. 1-16 ◽

Cited By ~ 2

Author(s):

K. Ma ◽

N. W. Xu ◽

Z. Z. Liang

Keyword(s):

Rock Mass ◽

Slope Stability ◽

Monitoring System ◽

Rock Slope ◽

Rock Slope Stability ◽

Hydropower Station ◽

Bank Slope ◽

The Stability ◽

The Right ◽

Dagangshan Hydropower Station

A high-resolution microseismic (MS) monitoring system was implemented at the right bank slope of the Dagangshan hydropower station in May 2010 to analyse the slope stability subjected to continuous excavation. The MS monitoring system could real-time capture a large number of seismic events occurring inside the rock slope. The identification and delineation of rock mass damage subject to excavation and consolidation grouting can be conducted based on the analysis of tempospatial distribution of MS events. However, how to qualitatively evaluate the stability of the rock slope by utilizing these MS data remains challenging. A damage model based on MS data was proposed to analyse the rock mass damage, and a 3D finite element method model of the rock slope was also established. The deteriorated mechanical parameters of rock mass were determined according to the model elements considering the effect of MS damage. With this method, we can explore the effect of MS activities, which are caused by rock mass damage subjected to excavation and strength degradation to the dynamic instability of the slope. When the MS damage effect was taken into account, the safety factor of the rock slope was reduced by 0.18 compared to the original rock slope model without considering the effect. The simulated results show that MS activities, which are subjected to excavation unloading, have only a limited effect on the stability of the right bank slope. The proposed method is proven to be a better approach for the dynamical assessment of rock slope stability and will provide valuable references for other similar rock slopes.

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Numerical Investigation on Factors Influencing the Time-Dependent Stability of the Rock Slopes with Weak Structure Planes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.177 ◽

2013 ◽

Vol 353-356 ◽

pp. 177-182

Author(s):

Lian Chong Li ◽

Shao Hua Li

Keyword(s):

Rock Mass ◽

Rock Slope ◽

Failure Time ◽

Time Dependent ◽

Catastrophic Failure ◽

Long Term Stability ◽

Stability Of Slopes ◽

Factors Influencing ◽

Weak Structure

Under the combined effects of various external factors, such as temperature, seepage, alternate wetting and drying and so on, the mechanical properties of rock mass are susceptible to be deteriorated, and its strength characteristics are significantly degraded with time. The mesoscopic damage accumulated inside the rock, contributing the rock slope instability with weak structure planes, generate the time-dependent deformation, and eventually lead to the slope failure. Given the time-dependent deformation of the rock, numerical simulations are conducted to investigate the key factors influencing the long-term stability of slopes. Numerical results show that the catastrophic failure time of slopes is linear to its cohesion, and the bigger cohesion and friction angle increase catastrophic failure time, i.e., the stability of rock slope increase. In addition, the configuration of the intact rock bridge can also influence the time-dependent slope stability. Slope height can significantly affect the slope stability and the maximum horizontal displacement. Differences in rock mass storage environment play an important role in the long-term stability of slopes.

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First results after the deployment of a subsea geodetic monitoring system

10.5194/egusphere-egu21-7315 ◽

2021 ◽

Author(s):

Pierre-François Adam ◽

Nathalie Olivier ◽

David Jaouen

Keyword(s):

Velocity Profile ◽

Monitoring System ◽

Active Faults ◽

Monitoring Program ◽

Line Of Sight ◽

Tectonic Plates ◽

Sound Velocity Profile ◽

The North ◽

First Results

Geodetic networks at sea are necessary to monitor active faults and the long term displacement of tectonic plates. iXblue has developed a new integrated subsea monitoring system: CanopusThe Canopus transponders are enable to regularly measure precisely the distance between the transponders that are in acoustic line of sight. The measurement are stored in a memory inside each beacon and can be collected from surface using acoustic modem. In collaboration with the IUEM, and in the framework of ERC Focus project, 8 Canopus beacons were deployed at each side of the North Alfeo Fault in Sicilia for a&#160; 4 years monitoring program. To prepare the deployment, a first experiment took place in Brest Bay in July 2019, and a second one in La Ciotat Bay in September 2020. Thanks to Delph subsea positioning software, simulations enable to confirm acoustic line of sight between beacons considering the local bathymetry, the sound velocity profile and the height of the transponders above the seabed. The final deployment took place in October 2020. &#160;We present here the series of test and &#160;simulations conducted before the final deployment and the first results after deployment.

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Paraglacial Cirque Headwall Instability - Regional Scale Assessment Of Preconditioning Factors

10.5194/egusphere-egu2020-17195 ◽

2020 ◽

Author(s):

Andreas Ewald ◽

Jan-Christoph Otto

Keyword(s):

Rock Mass ◽

Rock Slope ◽

Regional Scale ◽

Regional Analysis ◽

Slope Instability ◽

Geotechnical Data ◽

Systematic Assessment ◽

Slope Inclination ◽

First Results ◽

Elevation Model

Cirques are characteristic landforms in high alpine environments with flat cirque floors flanked by steep headwalls. From a rock-mechanical perspective, rock walls are assumed to adjust over time according to their internal rock mass strength, which is determined by a number of factors including e. g. intact rock strength and fracture system characteristics. However, temperatures permanently below freezing as well as glacier coverage keep cirque headwalls stabilised so that slope inclination can evolve during glaciation that is far beyond strength equilibrium. When cirque headwalls deglaciate, the relative importance of rock mass properties increases drastically as they precondition rock slope instability. Cataclinal headwalls, where major fracture sets dip out of the slope, are rated as unstable and usually respond rapidly to glacier retreat. Anaclinal headwalls with in-dipping fracture sets in contrast respond delayed and probably less drastically. To date, a systematic assessment of the predisposition of cirque headwalls for rock slope instability following deglaciation is lacking. We aim to tackle this lacking by a systematic regional analysis of predisposition factors using GIS tools.&#160;For the central Hohe Tauern Range, Austria, regional datasets are available for the most important preconditioning factors including topography (digital elevation model), geology (digital geological map), glacier extent (digital glacier inventory), and permafrost distribution (PERMAKART 3.0). We combined geomorphometric analyses with geotechnical data to locate and evaluate the sensitivity of glacier headwalls to rock slope instability using GIS and object-based analysis techniques.&#160;Our results show that a vast majority of the headwalls identified can be divided by a significant convexity in the slope profile curvature into a larger, upper and a lower, steeper headwall section (> 60&#176;). The lower limit of the steeper section is marked by a significant concavity in the slope profile curvature, which is commonly known as the schrundline. Assuming that the convex transition between steeper and flatter headwall section constitutes the upper limit of enhanced headwall retreat e. g. by periglacial weathering inside the bergschrund, we further address this headwall section as the schrundwall.&#160;Geotechnical data (foliation dip and direction) has been digitalised and interpolated in a yet oversimplified manner, to distinguish&#160; headwalls into cataclinal, anaclinal and orthoclinal slopes. Slope inclination and foliation dip has been interrelated to identify e. g. particularly sensitive overdip slopes. First results show that anaclinal and orthoclinal as well as cataclinal headwalls are quite common features in the study area. However, overdip slopes with steeply (30&#176;-60&#176;) outdipping foliation are almost exclusively found in schrundwall sections.&#160;The persistence of steep overdip schrundwalls may be related to permafrost occurrence, which is subject to further analysis. Our approach, applied to modeled subglacial topography, may be of great value to anticipate future paraglacial instabilities in glacier headwalls.

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Stents for the Treatment of Aortic Aneurysms

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615578 ◽

1999 ◽

Vol 82 (S 01) ◽

pp. 171-175 ◽

Cited By ~ 1

Author(s):

D. Ebert ◽

M. Langer ◽

P. Uhrmeister

Keyword(s):

Endovascular Treatment ◽

Endovascular Repair ◽

Abdominal Aortic Aneurysms ◽

Aortic Aneurysms ◽

Imaging Modalities ◽

Exclusion Criteria ◽

Multicenter Studies ◽

Abdominal Aortic ◽

First Results

SummaryThe endovascular treatment of abdominal aortic aneurysms has generated a great deal of interest since the early 1990s, and many different devices are currently available. The procedure of endovascular repair has been evaluated in many institutions and the different devices are compared. The first results were encouraging, but complications like endoleak, dislocation or thrombosis of the graft occurred. By the available devices the stent application is only promising, if the known exclusion criteria are strictly respected. Therefore a careful preinterventional assessment of the patient by different imaging modalities is necessary. As the available results up to now are preliminary and the durability of the devices has to be controlled, multicenter studies are required to improve the devices and observe their long- term success in the exclusion of abdominal aortic aneurysms.

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