08.45 - 11.30 Workshop A: Ground treatment techniques for cost efficient urban tunnelling

(includes refreshment break)

Rationale:

To improve the strength, stiffness and reduce the permeability of ground while constructing underground structures close to existing structures techniques such as grouting and ground freezing are used. Ground treatment is particularly important when working below the ground water table in saturated ground. However, treating unsatisfactory ground conditions in urban tunnelling always increases costs and often can delay the project scheduling.

The workshop discusses the available techniques in ground treatment in general, and in ground freezing and grouting in particular. The workshop will discuss methods of assessing whether ground treatment is necessary or likely to be beneficial and also methods for testing the effectiveness of ground treatment and incorporating the results of ground treatment in predicting the effect of tunnelling on existing structures.

Learning objectives:

• What are the ground treatment techniques which are currently practiced in urban tunnelling conditions
• What to consider when planning a ground freezing or grouting scheme
• Methods for assessing whether ground treatment will be beneficial
• Treating water-logged conditions effectively through grouting or ground freezing
• Method for testing the effectiveness of ground treatment

Workshop leader:

Andy Pickles
Director
GOLDER ASSOCIATES

Andrew Pickles is one of the founding Directors of GCG (Asia). He has twenty five years’ experience in civil and geotechnical engineering on major projects in the UK, Hong Kong, South East Asia and Southern Africa. During this time, he has worked for consulting and contracting firms and client bodies. His experience includes the design and construction of reclamations, retaining walls, deep excavations, cut and cover and soft ground tunnels, piles and shallow foundations, earthworks and ground treatment. In addition, has acted as an expert witness in construction related disputes and mediations and he has wide experience interpreting site investigation and monitoring data.

12.15 - 15.00 Workshop B: Current techniques in condition assesment of structures and instrumentation for urban tunnelling

(includes lunch break)

From piling deformation to the loss in structural quality, structural damages to buildings in close vicinity to urban tunnel construction sites are prevalent. An improper or inadequate structural assessment leads to costly delays, litigations and ineffective changes to route alignments.

An effective and early condition assessment regime, aided by new analytical modelling techniques and instrumentation will greatly improve the project’s timely delivery and the quality of construction. This workshop will introduce the phenomenon of ground movement against different types of tunnelling methods and then discuss the methodology in the prediction of ground displacement based on empirical and numerical approaches.

It will also present the patterns of ground movement in different soil conditions based on previous experience and finally discuss the use of building damage classification method based on building strains and will also touch on building monitoring and instrumentation.

• Choose the right tunnelling methods taking into account ground movement pattern and their magnitude
• Assessing the precondition survey requirement of existing structures
• Improving the assessment techniques through enhanced inputs from the design and construction methodologies involved in underground structures
• Understand the risks involved on structural damages and learn how to mitigate or reduce them

Workshop leader:

Eric Chui
Head of Tunnels & Ground Engineeing
ATKINS

Eric has over 19 years’ experience in the study, design and construction management of large infrastructure projects in different parts of the world including several major tunnelling projects and has managed major multidisciplinary projects in Hong Kong. He has particular expertise in design of soft ground and rock tunnels constructed by various methods including TBM (Compressed air, EPBM, slurry and double-shield hard rock machine), cut and cover, pipe-jacking, Horizontal Directional Drilling (HDD) and drill and blast methods. He has experience in underpinning works for buildings, cavern design (large span rock tunnels), deep shafts design and damage risk assessment of tunnel works adjacent to structures.

His involvement in various Hong Kong tunnel projects includes: SIL C902, HATS 24, Lai Chi Kok Transfer Scheme, West Island Line, Express Rail Link, Kowloon Southern Link, Shatin to Central Link and West Rail Projects for KCRC, Central-Wan Chai Bypass Tunnel and P2 Underpass for CEDD and various cable tunnels (by HDD/TBM/ Pipe Jacking method) for CLP.