Veröffentlichungen des Instituts für Geotechnik (IGT) an der ETH Zürich

Swelling Rocks, Swelling Processes, Anhydritic Claystones, Anhydrite Dissolution, Gypsum Precipitation, Self-Sealing

Anhydritic claystones are highly problematic for underground construction because of their swelling ability: When the rock comes into contact with water, the rock volume expands due to swelling of both clay as well as anhydrite. When the expansion is restricted, e.g., by an invert arch in tunneling, the swelling rocks can exert high pressures on the lining and damage the structure. The swelling behavior of purely argillaceous rock (containing solely swelling clays and no anhydrite) can be attributed mainly to osmotic processes and is well understood for the conceptual design of tunnels, as opposed to the swelling of anhydrite, where considerable knowledge gaps exist.

Swelling Rocks, Swelling Processes, Anhydritic Claystones, Anhydrite Dissolution, Gypsum Precipitation, Self-Sealing

Anhydritic claystones are highly problematic for underground construction because of their swelling ability: When the rock comes into contact with water, the rock volume expands due to swelling of both clay as well as anhydrite. When the expansion is restricted, e.g., by an invert arch in tunneling, the swelling rocks can exert high pressures on the lining and damage the structure. The swelling behavior of purely argillaceous rock (containing solely swelling clays and no anhydrite) can be attributed mainly to osmotic processes and is well understood for the conceptual design of tunnels, as opposed to the swelling of anhydrite, where considerable knowledge gaps exist.

Tunnelling, Squeezing, Schistosity, Heterogeneity, Analytical Solution, Numerical Modelling, Segmental Lining

The magnitude of squeezing deformations in tunnelling often varies over short distances, even if there is no obvious change in the construction method, in the depth of cover, in the lithology or rock structure. As long as the reasons for the variability are not known, the tunnelling-induced convergences cannot be predicted with sufficient reliability. Reliable predictions, however, are important for determining the temporary support or the excavation diameter. Otherwise, large-scale tunnel repairs may be necessary, which can cause delay and additional costs due to remedial actions as well as due to the enforced interruption of other operations in progress at the same time.

Tunnelling, Squeezing, Schistosity, Heterogeneity, Analytical Solution, Numerical Modelling, Segmental Lining

The magnitude of squeezing deformations in tunnelling often varies over short distances, even if there is no obvious change in the construction method, in the depth of cover, in the lithology or rock structure. As long as the reasons for the variability are not known, the tunnelling-induced convergences cannot be predicted with sufficient reliability. Reliable predictions, however, are important for determining the temporary support or the excavation diameter. Otherwise, large-scale tunnel repairs may be necessary, which can cause delay and additional costs due to remedial actions as well as due to the enforced interruption of other operations in progress at the same time.

Silty Sand, Dynamic Behaviour, Earthquake Engineering, Basin Effects, Soil Structure Interaction, Alpine Valleys, Seismic Monitoring, Dams

Silty Sand, Dynamic Behaviour, Earthquake Engineering, Basin Effects, Soil Structure Interaction, Alpine Valleys, Seismic Monitoring, Dams

Gravel Columns, Bearing Capacity, Soil Conditions, Soil Characteristics, Lacustrine Clay

Gravel Columns, Bearing Capacity, Soil Conditions, Soil Characteristics, Lacustrine Clay

Tunnelling, Tunnel Jacking, Ground Stability, MC Model, MCC Model

Rock Pressure, Tunnel, Tunnelling, Gotthard, Gibraltar Tunnel

Advance Drainage, Drainage Boreholes, Tunnel, Face Stability, Limit Equilibrium, Fault Zone, Drainage Capacity, Equivalent Hydraulic Conductivity, Borehole Casing, Lead-Time, Groundwater Drawdown, Settlement, Inflow, Grouting Body, Displacement, Characteristic Line

Landslide, Mudslide, Soil Mechnics, Hydraulic, Rhine, Rüdlingen

Landslides triggered by rainfall cause significant damage to infrastructure annually and affect many lives in several parts of the world, including Switzerland. These landslides are initiated by a decrease in the effective stresses, and hence the shear strength of the soil, as a result of the increase in pore water pressure.

Flood Protection, Rhone, Failure Mechanism, Overflow

Knowledge of the performance of river dykes during flooding is necessary when designing governmental assistance plans aimed to reduce both casualties and material damage. This is especially relevant when floods have increased in their frequency during the last decades, together with the resulting material damage and life costs.

Braunkohlebergbau, Altlasten, Tonboden, Bodenverbesserung

Double porosity soil is characterised by a soil continuum containing two distinct porosities. Typically, this consists of macro-grains (lumps) of soil that have an internal porosity defined as the intragranular porosity. The spaces between lumps are identified as intergranular voids that give rise to the intergranular porosity.

Permafrost, Rock Glacier, Crawling Motion, Slope Instability, Geotechnical Engineering

Alpine permafrost exists at high altitude at lower latitudes, such as in the Swiss Alps. Accelerating climate change, including rising mean annual air temperature and extreme rainfall conditions in alpine regions induces permafrost degradation.

Hochwasserschutz, Wasserretention, Rhone, Geotechnik

Die Hochwasserereignisse der letzten Jahrzehnte haben die Grenzen des Hochwasserschutzes deutlich ans Licht gebracht. Die Analyse der Auswirkungen von Klimaänderungen lässt zudem eine Erhöhung des Hochwasserrisikos befürchten. Viele Flussdämme als wichtiger Bestandteil des Hochwasserschutzes stammen aus dem 19. Jahrhundert und entsprechen nicht mehr dem heutigen Stand der Technik. Der Handlungsbedarf ist gross und es müssen Prioritäten entsprechend dem Gefährdungspotenzial gesetzt werden. In dieser Hinsicht sind zusätzliche Kenntnisse vom Verhalten der Flussdämme unter wiederholter Hochwasserbelastung und wechselnder Witterung notwendig.

Tunnelling, Claystones, Gypsum Keuper, Swelling Process

Sulphatic claystones are among the most problematic rocks in tunnelling due to their distinctive swelling properties. They are known to have caused severe damage, for example, to numerous tunnels excavated in the Gypsum Keuper formation. The repairs were extremely costly and time-consuming, and often provided only a temporary solution. The setbacks experienced in tunnelling through Gypsum Keuper may be attributed, among other things, to our limited knowledge of the macroscopic principles governing the swelling process and the underlying microscopic mechanisms.

Tunnelling, Tunnel Advance, Rock Pressure

In the last two decades, Brillouin distributed fiber-optic sensing has became a widely accepted, mature technology. On the other hand, geotechnical monitoring applications of this technology are still rare, as the fragile fiberoptic and the harsh soil environment are a difficult combination. Additionally, due to high uncertainties in soil behavior, deeper understanding of geomechanical principles is necessary in order to achieve meaningful results when using these sensors.

Tunnelling, Rock Pressure, Tunnel Advance

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Gefrierverfahren, Tiefbau, Tunnelbau, TH-Modell, Thermohydraulisches Modell

Beim Gefrierverfahren wird der Baugrund temporär künstlich vereist und somit verfestigt, versteift und abgedichtet. Im Untertagebau dient dieses Verfahren zur Gewährleistung der Standsicherheit des Vortriebsbereichs und zur Beschränkung der Geländesetzungen.