SYNOPSIS

The seminar will be split into two main parts:

1.    Challenges of Underground Construction in the Built-up Environment

The talk intends to direct the focus on the application of unusual construction methods and related design and construction challenges highlighting solutions to major challenges of planning underground projects in the heavily built-up zones of urban environments. This is presented in the form of examples from the viewpoint of a practitioner, who is deeply involved in the actual design for the implementation of such projects. Infrastructure in large cities is getting denser over time. Therefore, interference with existing structures is becoming a very common feature during the implementation process of new projects. As consequence, actual geotechnical challenges often relate to the application of innovative methods of construction to minimize potential construction impact or disruption.

Duration:    2 hours


2.    Simplified Approaches for Complex Assessments Related Top TBM Tunnelling

For very complex and complicated situations, related design tasks can be carried out based on simplified approaches when they are derived using proper engineering analysis. These simplified approaches are especially relevant for preliminary assessments, such as tender designs, when too detailed analyses are either too time consuming or, due to lack of detailed information, would need to be based on too many assumptions, anyhow. In such cases, relevant design results can be obtained efficiently by applying simplified methods.

Therefore, the main aim of this talk is making the auditorium remember some of the basic analysis tools, which they might have heard during their engineering training. With proper engineering judgment, many of which could be used to derive such simplified analysis approaches. This is demonstrated with the help of three practical examples.

a)    Large diameter rock TBM under high water head

Driving a large diameter TBM in rock conditions under high water head conditions requires assessment of ground water inflows during driving and stoppage for cutterhead intervention. This becomes particularly important when defining the detailed requirements of the TBM during a tender whether the expected inflow quantities can be managed and what pumping capacities are required. Based on numerical analysis of few selected cross sections, assessment in different overburden and water head scenarios can be made and results simplified to be applied to varying conditions without further numerical analyses.

b)    Preliminary assessment settlements of complicated excavations

Complicated cross sections such as NATM excavation are excavated in many sub-stages with staged ground support application following these stages. Therefore, numerical analysis of such an excavation result in complicated models and time-consuming analyses. This can be simplified by analyzing only an “incremental” tunnel advance which than can be superimposed with each other applying a generalized volume loss approach.

c)    Special tools for assessment of monitoring results.

Tools for assessing the longitudinal distribution of settlement monitoring results along a tunnel drive to derive data which can be used to make decisions related to tunnel driving.

Duration:    2 hours


BIODATA OF SPEAKER

Dr. OSCAR SIGL

Dr. Oskar Sigl graduated as Diploma Engineer (MSc.) 1985 from Technical University of Graz (Austria), in Civil Engineering specializing in geotechnics and soil mechanics.

In 1991, after working for five years as Teaching Assistant at the Institute for Geomechanics and Tunnelling, he achieved with distinction the PhD in mining engineering at the Mining University of Leoben (Austria).

Oskar’s more 35 years of experience cover a wide range of underground infra structure projects such as subways, railways, roads, power transmission cables, sewerage mains, underground storage schemes and caverns.

Oskar has been working in Singapore since 1997, where he was involved in the detailed design of almost all major underground infra structure projects. This includes the North East Line, Circle Line, Downtown Line, Thomson-East Coast Line, Cross-Island Line MRTs, the SPPA high voltage transmission cable tunnels, the Kallang Paya Lebar and Marine Costal Expressways, the Deep Tunnel Sewer System, and many more.

Outside of Singapore, Dr. Sigl was involved in leading roles in the design of underground subway systems in Kuala Lumpur, Dubai, Perth, Hong Kong, as well as the design of underground oil and fuel storage cavern schemes in Saudi Arabia, India and the UAE.