With the ever increasing urbanization in the world, the demand for underground space continues to grow. Very many urban areas are located on soft ground. Hence tunnellers need to understand how to create underground spaces in this type of strata. In this context, soft ground is defined as a geomaterial with a low strength – such sand or clay, conglomerate or weak rocks like siltstone or chalk. These geomaterials tend to behave largely as continuum. In harder rock (under low stress), discontinuous behaviour tends to dominate – such as block stability. Hence the construction and design of tunnels in harder rock is distinctly different.
First, this course will look at the over-arching principles of design in the context of soft ground. Topics such as safety, risk management, sustainability and design codes will be covered in outline. The key aspects of geotechnics will be highlighted, on the assumption that the attendees have a basic understanding of this subject already.
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Objetivos
From this course, you will gain an understanding of: The key design principles for soft ground tunnels The importance of soil-structure interaction Construction methods for soft ground tunnels Design methods for tunnel linings Sprayed concrete lined tunnels in soft ground
A quién va dirigido
This course is aimed at professionals who have some undergraduate understanding of soil mechanics and geomechanics and basic structural engineering. Potential attendees include: – Geology, Geotechnical or Civil Engineering post-graduate students interested in learning the principles of soft ground tunnelling – Geology, Geotechnical or Civil Engineering professionals who want to pursue or transition into a tunneling career – Tunneling practitioners (technicians and engineers alike) who need to refresh or update their knowledge of soft ground tunnelling – Structural Engineering professionals who want to have a more comprehensive understanding of the role of the ground in tunnel engineering This course is suitable for engineers working in all parts of this sector: clients; designers and contractors.
Temario completo de este curso
MODULE 1. General design
The course starts with a recap on general design methodology within the context of soft ground to ensure that all participants have the correct foundation for this course. A risk-based design is essential for safe designs and this is implicit or explicit in all design work. The boundaries of soft ground (vs hard rock) will be outlined. A wide range of factors influence a design such as functional requirements like waterproofing, fire protection and durability as well structural performance. Sustainability will be examined in detail.
MODULE 2. Soil-structure interaction
The biggest influence on any tunnel is the ground. A thorough understanding of the type of ground and the hydrogeology is required in order to identify the key mechanisms of ground behaviour. This governs the choice of construction method and from the two arise the design calculations. By focusing on the fundamentals of ground behaviour, the course will show how to develop safe and cost-effective solutions in any situation. Settlement is a key concern for soft ground tunnelling. Prediction, monitoring and mitigation of settlement will be discussed.
MODULE 3. Construction methods
Having understood the mechanisms present, a construction method can be chosen to manage these risks effectively. This has an influence on the design so this topic appears before design. Common construction techniques in soft ground tunnelling include: cut & cover; TBMs with segmental linings; sprayed concrete lined tunnels (SCL/NATM). Immersed tube tunnels and pipejacking are less common so they will only be discussed briefly. In addition ground treatment is sometimes used to reduce water ingress or to improve the ground.
MODULE 4. Design methods
There are three type of (structural) design methods – empirical, analytical and numerical method. Each one will be examined in detail, considering the common tools used for soft ground cases. Guidance will be given on how and when to use each method, as well as their benefits and limitations. Special structures such as portals, junctions and shafts will be considered, along with special design cases such as seismic loading and fire.
MODULE 5. Sprayed concrete linings (SCL/NATM)
This module will look in detail at SCL tunnelling in soft ground, beginning with mix design and material technology, then advancing to the properties of sprayed concrete and material behaviour. Construction methods, including the excavation sequence, have a large influence on design so this will be explored before explaining the common analytical and numerical design methods. Construction management and monitoring play a key role in successful SCL tunnelling.