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
Construction on soft soils is always accompanied by the risk of significant, time-dependent settlement and bearing capacity failure. As technical knowledge has advanced, optimised ground improvement has offered significant economic advantages in reducing net settlement and resisting failure by installation of more flexible and cost-effective stone columns or sand compaction piles in the ground, rather than more rigid inclusions such as steel or concrete piles. The stiffness and strength of the subsoil around the columns is greater, and the consolidation time is reduced through shorter (radial) drainage paths.Gravel Columns, Bearing Capacity, Soil Conditions, Soil Characteristics, Lacustrine Clay
Construction on soft soils is always accompanied by the risk of significant, time-dependent settlement and bearing capacity failure. As technical knowledge has advanced, optimised ground improvement has offered significant economic advantages in reducing net settlement and resisting failure by installation of more flexible and cost-effective stone columns or sand compaction piles in the ground, rather than more rigid inclusions such as steel or concrete piles. The stiffness and strength of the subsoil around the columns is greater, and the consolidation time is reduced through shorter (radial) drainage paths.Tunnelling, Tunnel Jacking, Ground Stability, MC Model, MCC Model
This thesis investigates the problem of time-dependent stability of geotechnical structures (such as trenches or tunnels) in medium- to low-permeability water-bearing grounds, typically clayey or silty soils. The peculiarity of these soils is that they respond to excavation with a delay. The time-dependency can be traced back to the swelling process triggered by the dissipation of the excavation-induced negative excess pore pressures. Unstable conditionsmay necessitate improvement or reinforcement of the ground or the application of a support (e.g. by compressed air or pressurized bentonite slurry in the case of tunnel face). As such measures may present economical and operational disadvantages, the question of whether and for how long the excavation can remain stable without support is of great practical relevance. The stand-up time (time lapsing between end of the excavation and the occurrence of failure), and thus the feasibility of refraining from ground reinforcement, improvement or support, depends essentially on soil strength and permeability.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.
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.