Florian Amann

• Full Professor
• Chair at RWTH Aachen University

Catastrophic collapse of large rock slopes ranks as one of the most hazardous natural phenomena in mountain landscapes. The cascade of events, from rock-slope failure, to rock avalanche and the near-immediate release of debris flows has not previously been described from direct observations. We report on the 2017, 3.0 × 10⁶ m³ failure on Pizzo Ceng...

High-pressure fluid injections cause transient pore pressure changes over large distances, which may induce seismicity. The zone of influence for such an injection was studied at high spatial resolutions in six decameter-scaled fluid injection experiments in crystalline rock. Pore pressure time series revealed two distinct responses based on the la...

We used synthetic aperture radar offset tracking to reconstruct a unique record of ice surface velocities for a 3.2 year period (15 January 2017–6 April 2020), for the Palcaraju glacier located above Laguna Palcacocha, Cordillera Blanca, Peru. Correlation and spatial cluster analysis of residuals of linear fits through cumulative velocity time seri...

Landslide run-out modeling involves various uncertainties originating from model input data. It is therefore desirable to assess the model’s sensitivity to these uncertain inputs. A global sensitivity analysis that is capable of exploring the entire input space and accounts for all interactions often remains limited due to computational challenges...

A microphysics-based understanding of mechanical and hydraulic processes in clay shales is required for developing advanced constitutive models, which can be extrapolated to long-term deformation. Although many geomechanical tests have been performed to characterise the bulk mechanical, hydro-mechanical, and failure behaviour of Opalinus Clay, impo...

Cold water injection into geothermal reservoirs is a common, sometimes necessary, technique for multiple reasons including the replenishment and stimulation of the reservoirs, and the disposal of waste water. The injection of cold water results in a thermo-hydro-mechanical (THM) impulse, which can cause near-wellbore cracking. A method is presented...

Over the past few decades, several performance indicators have been developed to assess the impact of geological conditions on Tunnel Boring Machine (TBM) performance. These indicators primarily focus on accurately calculating the thrust force per cutter (TpC) required for a disc cutter to penetrate a specific type of rock. However, existing models...

A R T I C L E I N F O Keywords: Thermo-mechanical model Cyclic thermo-mechanical loading Long-term stability of salt cavern Horizontal salt cavern Hydrogen storage A B S T R A C T Underground salt caverns are considered viable options for hydrogen storage owing to their favorable geological properties and large storage capacity. However, during und...

The search for a suitable host rock for the deep geological disposal of high-level radioactive waste is one of the major geological challenges of our time. In Germany, alongside rock salt and crystalline rock, claystones are considered a promising geomaterial and the subject of intensive research within the scope of the site selection process. Part...

Switzerland is committed to reduce the overall greenhouse gas emissions to net-zero, meaning that any residual emission of fossil CO2 shall be compensated, either in Switzerland or abroad. Deep geothermal energy exploitation, heat storage in sedimentary rocks and permanent geological storage of CO2, are the three key elements for the Swiss net-zero...

The repurposing of abandoned coal mines in Europe presents significant opportunities and challenges for sustainable underground spatial utilization, particularly for energy storage solutions. This study focuses on the geological and mining factors influencing the feasibility of converting these abandoned coal mines into underground storage reservoi...

This study presents a thermo-hydro-mechanical framework to model hydrothermal systems within a simplified faulted synthetic reservoir, replicating current production scenarios in The Netherlands and Germany. The reservoir, composed of porous and permeable sandstone, and the confining layer, made of porous but less permeable shale, undergoes a proce...

We performed a series of hydraulic stimulations at 1.1 km depth in the Bedretto underground laboratory, Switzerland, as part of an overall research strategy attempting to understand induced seismicity on different scales. Using an ultra‐high frequency seismic network we detect seismic events as small as Mw < −4, revealing intricate details of a com...

Performing stimulation experiments at approximately 1 km depth in the Bedretto Underground Laboratory for Geosciences and Geoenergies necessitates identifying and characterizing the target fault zone for on-fault monitoring of induced fault slip and seismicity, which presents a challenge when attempting to understand seismogenic processes. We discu...

The Thrust-Penetration Gradient (TPG) is an essential tool in analyzing and predicting the performance of Tunnel Boring Machines (TBMs). It evaluates TBM efficiency, reflecting geomechanical dynamics during tunneling. The TPG effectively captures the complex relationship between thrust and penetration rates across various rock masses, drawing a par...

Development of brittle damage around tunnels is quite common in massive rocks under highly-stressed conditions. Understanding the shape and extent of the Excavation Damage Zone (EDZ) is important, particularly for deep geological repositories (DGRs) for nuclear waste. Within the EDZ, permeability is often increased, and in the context of nuclear wa...

Geomechanical properties of clay shales significantly depend on mineralogical composition, saturation, and burial history. In this contribution, we provide insights into a unique opportunity to study the influence of burial history on geomechanical parameters of a rock unit in a distinctive area in Northern Germany where clay shales were retrieved...

In order to estimate the depth of the Excavation Damage Zone (EDZ) using empirical or numerical approaches, the key intact properties include the Uniaxial Compressive Strength (UCS), the tensile strength, and the crack initiation threshold. In addition to these test derived values, plotting triaxial test results and determined Crack Initiation valu...

Performing stimulation experiments at approximately 1 km depth in the Bedretto Underground Laboratory for Geosciences and Geoenergies necessitates identifying and characterizing the target fault zone for on-fault monitoring of induced fault-slip and seismicity, a current challenge in understanding seismogenic processes. We discuss the multidiscipli...

Brittle faults and fault zones are among the most hydraulically active elements in predominantly impermeable crystalline host rock. They pose a significant challenge to underground infrastructure like nuclear waste repositories. Brittle fault zones frequently occur along pre-existing ductile shear zones as they introduce weakness planes in the rock...

Over the past few decades, Toarcian (Early Jurassic) black shale deposits of NW Europe have been extensively studied, and the possible global and regional mechanisms for their regional variation have been discussed. In this context, the black shales of the Northwest German Basin are still sparsely studied with regard to their palaeo-depositional hi...

The relationship between rock-slope failure and glacier retreat is complex, and paraglacial failures often lack clearly identified triggers. To better understand the role of glacier retreat in rock-slope failures, we analysed the processes that led to the October 1967 Grewingk landslide in Kachemak Bay State Park on the Kenai Peninsula, Southcentra...

Many rocks exhibit a structural composition, which leads to an anisotropic behavior of different properties. A proper understanding of the directional dependency of these properties is required to analyze and predict the failure behavior of the rock mass upon stress changes during many geo‐engineering applications. This study investigates the selec...

Clay shales are low-permeable sedimentary rocks that exhibit inherent cross-anisotropic stiffness, strength, and permeability. Accurate design of tunnels excavated in clay shales requires appropriate constitutive models that account for the anisotropic properties of the host rock, especially under undrained conditions. This paper presents a transve...

The utilization of Underground Pumped Storage Power Systems (UPSP) addresses the growing need for energy storage in the face of increasing intermittent energy sources. Simultaneously, the closure of mining activities has resulted in vast underground spaces potentially becoming available for alternative purposes. This paper explores the potential of...

Heat and electricity production from deep hot reservoirs through hydrothermal or petrothermal system requires to inject cold fluid in a naturally or artificially fractured medium. Cold water injection in a hot reservoirs causes thermo-hydro-mechanical (THM) coupled processes that may have several influences on operations and long term production [1...

Tunnelling conditions characterized by large and long-term deformations demand yielding support elements as a part of the shotcrete lining. The yielding support elements transform radial displacements into a tangential closure without compromising the lining system's support capacity and avoiding micro-cracking and over-stressing of the shotcrete d...

Geological models are commonly used to predict the position of relevant geological features, such as rock types or faults in the subsurface. These models can contain significant uncertainties, as the geological input parameters are often not perfectly known. Predictions of geological features, for example, on the level of a tunnel during an excavat...

The Einstein Telescope will be a gravitational wave observatory comprising six nested detectors, three optimized to collect low-frequency signals, and three for high frequency. It will be built a few hundred meters under Earth’s surface to reduce direct seismic and Newtonian noise. A critical issue with the Einstein Telescope design are the three c...

Stability of coal pillar (walls) is of great importance to security of underground mining. Periodic excavation and water table variation subject coal pillars (walls) to cyclic load with varying stressing rates and wetting–drying (WD) circumstances. Therefore, investigation on mechanical responses of coal exposed to effects of WD and compressive dif...

For analyzing the influence of structural anisotropy on the hydro-mechanical behavior of a clay shale, we performed three consolidated, undrained triaxial compression tests with different geometric specimen configurations. Opalinus Clay specimens were tested with bedding plane orientations of 30°, 60°, and 90° with respect to the horizontal. Result...

For analyzing the influence of structural anisotropy on the hydro-mechanical behavior of a clay shale, we performed three consolidated, undrained triaxial compression tests with different geometric specimen configurations. Opalinus Clay specimens were tested with bedding plane orientations of 30°, 60°, and 90° with respect to the horizontal. Result...

The entire water cycle is contaminated with largely undetected micropollutants, thus jeopardizing wastewater treatment. Currently, monitoring methods that are used by wastewater treatment plants (WWTP) are not able to detect these micropollutants, causing negative effects on aquatic ecosystems and human health. In our case study, we took collective...

Test Stand for True Triaxial Rock tests at the Institute of Geomechanics and Underground Construction at RWTH Aachen University: • True anisotropic • All principle stresses independent • Large sample sizes (30 x 30 x 45 cm3) • Up to 30 MPa • Injection tests • Fracture localisation

Die realistische Abbildung der geologischen Verhältnisse und geomechanischen Prozesse im Untergrund stellt eine zentrale Frage bei der Suche nach geeigneten Endlagerstandorten dar. Um diese in repräsentativen Laborversuchen untersuchen zu können, bedarf es besonderer Versuchsgeräte, mit denen die vorherrschenden Druckverhältnisse in einem ausreiche...

The way rocks deform under changing stress conditions can be described by different deformation modes, which is fundamental for understanding their rheology. For Opalinus Clay, which is regarded as a potential host rock for nuclear waste, we investigate the failure mode as a function of applied effective stress in laboratory experiments. Therefore,...

This article presents the stresses at the center of a Brazilian disk (BD) for transversely isotropic rocks. It is shown that the solution of stresses at the center of an anisotropic disk is a function of the disk radius and the magnitude of applied load, as well as the material orientation with respect to the load axis and two dimensionless ratios...

Gravitational wave detectors like the Einstein Telescope will be built a few hundred meters under Earth's surface to reduce both direct seismic and Newtonian noise. Underground facilities must be designed to take full advantage of the shielding properties of the rock mass to maximize the detector's performance. A major issue with the Einstein Teles...

The way rocks deform under changing stress conditions can be described by different deformation modes, which is fundamental for understanding their rheology. For Opalinus Clay, which is considered as a potential host rock for nuclear waste, we investigate the failure mode as a function of applied effective stress in laboratory experiments. Therefor...

The increased interest in subsurface development (e.g., unconventional hydrocarbon, engineered geothermal systems (EGSs), waste disposal) and the associated (triggered or induced) seismicity calls for a better understanding of the hydro-seismo-mechanical coupling in fractured rock masses. Being able to bridge the knowledge gap between laboratory an...

The stress state in a rock mass is complex. Stress redistribution around underground excavation may lead to various failure modes, including compressive-shear, tensile-shear, and tensile failures. The ability to perform laboratory tests with these complex stress states is significant for establishing new strength criteria. The present paper introdu...

Tunnelling conditions characterized by large and long-term deformations demand yielding support elements as a part of the shotcrete lining. The yielding support elements transform radial displacements into a tangential closure without compromising the lining system's support capacity and avoiding micro-cracking and overstressing of the shotcrete du...

In the context of selecting and designing a future repository site for nuclear waste, a proper understanding of the host rock's physical behavior is required. One of the fundamental characteristics is the hydraulic diffusivity of the host rock, i.e., the ratio between permeability and storativity. For low-permeability rocks, however, determination...

The stability analysis of underground excavations constructed in low-permeable rocks requires a comprehensive understanding of the short- and long-term pore pressure response around the excavation. This paper presents the results of a novel in-situ experiment, which was conducted in Opalinus Clay at the Mont Terri Underground Rock Laboratory, Switz...

The increased interest in subsurface development (e.g., unconventional hydrocarbon, deep geothermal, waste disposal) and the associated (triggered or induced) seismicity calls for a better understanding of the hydro-seismo-mechanical coupling in fractured rock masses. Being able to bridge the knowledge gap between laboratory and reservoir scales, c...

Environmental monitoring of aquatic systems is the key requirement for sustainable environmental protection and future drinking water supply. The quality of water resources depends on the effectiveness of water treatment plants to reduce chemical pollutants, such as nitrates, pharmaceuticals, or microplastics. Changes in water quality can vary rapi...

A microphysics-based understanding of mechanical and hydraulic processes in clay shales is required for developing advanced constitutive models, which can be extrapolated to long-term deformation. Although many geomechanical laboratory tests have been performed to characterize the bulk mechanical, hydro-mechanical and failure behaviour of Opalinus...

We investigated the induced seismicity, source mechanisms and mechanical responses of a decameter-scale hydraulic stimulation of a pre-existing shear zone in crystalline rock, at the Grimsel Test Site, Switzerland. The analysis reveals the meter-scale complexity of hydraulic stimulation, which remains hidden at the reservoir-scale. High earthquake...

The present time is a significant stage in the adjustment of mountain slopes to climate change and specifically atmospheric warming. This review examines the state of understanding of the responses of mid-latitude alpine landscapes to recent cryospheric change and summarizes the variety and complexity of documented landscape responses involving gla...

A comprehensive characterization of clay shale behaviour requires quantifying both geomechanical and hydromechanical characteristics. This paper presents a comparative laboratory study of different methods to determine the water permeability of saturated Opalinus Clay: i) pore pressure oscillation, ii) pressure pulse decay, and iii) pore pressure e...

Landslide run-out modeling involves various uncertainties originating from model input data. It is therefore desirable to assess the model's sensitivity. A global sensitivity analysis that is capable of exploring the entire input space and accounts for all interactions, often remains limited due to computational challenges resulting from a large nu...

Six hydraulic fracturing (HF) experiments were conducted in situ at the Grimsel Test Site (GTS), Switzerland, using two boreholes drilled in sparsely fractured crystalline rock. High spatial and temporal resolution monitoring of fracture fluid pressure and strain improve our understanding of fracturing dynamics during and directly following high-pr...

Six hydraulic shearing experiments have been conducted in the framework of the In-situ Stimulation and Circulation experiment within a decameter-scale crystalline rock volume at the Grimsel Test Site, Switzerland. During each experiment fractures associated with one out of two shear zone types were hydraulically reactivated. The two shear zone type...

The Einstein Telescope (ET) is a proposed next-generation, underground gravitational-wave detector to be based in Europe. It will provide about an order of magnitude sensitivity increase with respect to the currently operating detectors and, also extend the observation band targeting frequencies as low as 3 Hz. One of the first decisions that needs...

Ground-penetrating radar (GPR) and seismic imaging have proven to be important tools for the characterization of rock volumes. Both methods provide information about the physical rock mass properties and geological structures away from boreholes or tunnel walls. Here, we present the results from a geophysical characterization campaign that was cond...

We performed a series of 12 hydraulic stimulation experiments in a 20m×20m×20m foliated, crystalline rock volume intersected by two distinct fault sets at the Grimsel Test Site, Switzerland. The goal of these experiments was to improve our understanding of stimulation processes associated with high-pressure fluid injection used for reservoir creati...

Hydraulic fracturing (HF) experiments were conducted at the Grimsel Test Site (GTS), Switzerland, with the aim to improve our understanding of the seismo-hydro-mechanical processes associated with high-pressure fluid injection in a moderately fractured crystalline rock mass. Observations from one of these HF experiments indicate simultaneous propag...

Temporal changes in groundwater chemistry can reveal information about the evolution of flow path connectivity during crustal deformation. Here, we report transient helium and argon concentration anomalies monitored during a series of hydraulic reservoir stimulation experiments measured with an in situ gas equilibrium membrane inlet mass spectromet...

Abstract. Ground-penetrating radar (GPR) and seismic imaging have proven to be important tools for the characterization of rock volumes. Both methods provide information about the physical rock mass properties and geology structures away from boreholes or tunnel walls. Here, we present the results from a geophysical characterization campaign that w...

The Einstein Telescope (ET) is a proposed next-generation, underground gravitational-wave (GW) detector based in Europe. It will provide about an order of magnitude sensitivity increase with respect to currently operating detectors, and furthermore, extend the observation band towards lower frequencies, i.e., down to about 3\,Hz. One of the first d...

Permeability enhancement of a reservoir through hydraulic stimulation is ever so often accompanied by potentially hazardous induced seismicity. Monitoring of in situ pressure propagation remains an important step in understanding the underlying seismo‐hydromechanical processes during hydraulic stimulation and mitigating hazardous induced seismicity...

This paper presents the results of 124 pure Mode I fracture toughness tests on two types of anisotropic rocks, the metamorphic Grimsel Granite and the sedimentary Mont Terri Opalinus Clay. The results show that Mode I cracks in anisotropic rocks tend to kink towards the foliation or bedding planes that are weaker in strength. The experiment data fo...

Plain Language Summary Hydraulic shearing of preexisting fractures and hydraulic fracturing are commonly used to enhance the hydraulic conductivity and connectivity within in situ fracture networks, for example, in the framework of geothermal heat exploitation. Both treatments are based on high‐pressure fluid injections that induce deformation in t...

Geotechnical assessment of the refilling of the Lüschersee A mass movement of several m/year towards the Nolla stream was detected at the southern Heinzenberg (Grisons, Switzerland) in the 19 th century. Debris flows originating from the upper stream valley reached the Hinterrhein valley at irregular intervals, creating temporary dams, which raised...

Six hydraulic shearing experiments have been conducted in the framework of the In-situ Stimulation and Circulation experiment within a decameter-scale crystalline rock volume at the Grimsel Test Site, Switzerland. During each experiment one out of two different shear zone types were hydraulically reactivated. An extensive monitoring system of senso...

The history of reservoir stimulation to extract geothermal energy from low permeability rock (i.e. so-called petrothermal or engineered geothermal systems, EGS) highlights the difficulty of creating fluid pathways between boreholes, while keeping induced seismicity at an acceptable level. The worldwide research community sees great value in address...

Supplement of "Hydraulic fracture propagation in a heterogeneous stress field in a crystalline rock mass" inlcuding Text S1: Pressure vs. Flow-rate analysis Text S2: Transmissivity values Text S3: Detailed observation of tilt, strain and pressure Text S4: Summary of the MF injection pressure and seismic characteristics Text S5: Fracture orientati...

As part of the In-situ Stimulation and Circulation (ISC) experiment, hydraulic fracturing (HF) tests were conducted in a moderately fractured crystalline rock mass at the Grimsel Test Site (GTS), Switzerland. The aim of these injection tests was to improve our understanding of processes associated with high-pressure fluid injection. A total of six...

We performed a series of 12 hydraulic stimulation experiments in a 20 x 20 x 20 m foliated, crystalline rock volume intersected by two distinct fault sets at the Grimsel Test Site, Switzerland. The goal of these experiments was to improve our understanding of stimulation processes associated with high-pressure fluid injection used for reservoir cre...

As part of the In-situ Stimulation and Circulation (ISC) experiment, hydraulic fracturing (HF) tests were conducted in a moderately fractured crystalline rock mass at the Grimsel Test Site (GTS), Switzerland. The aim of these injection tests was to improve our understanding of processes associated with high-pressure fluid injection. A total of six...