SYNOPSIS
1. RISK MANAGEMENT ON SOME LARGE TUNNELLING PROJECTS by Mr. Gus Klados
The author presents the basics of the modern trend of risk management on tunnelling projects, required by the Code of Practice for Risk Management in Tunnels (Code) prepared by The International Tunnelling Insurance Group. Though the application of the Code is voluntary, it is practically impossible to obtain Contractor’s All Risk Insurance or Third Party Liability Insurance without practicing the Code. Without these insurances employers do not sign contracts with contractors. The author discusses typical risks and risk mitigation in tunnelling through some examples of The Channel Tunnel Project, The Lesotho Highlands Water Project, The Deep Tunnel Sewer System, The Athens Metro Lines 2 & 3, The SMART Project, The Budapest Metro Line 4 and the KVMRT SBK Line Projects he participated in. Although the Code was not in force during the execution of most of these projects common engineering sense and good practice demanded that the principles of assessing, managing and mitigating risks/hazards were applied without using the terminology of the relatively new Code. The Code was used during the construction of the KVMRT SBK Line to the satisfaction of the project insurers and is going to be used on the SSP Line, too.
2. CHALLENGES OF TUNNELLING AND UNDERGROUND SPACE DEVELOPMENT IN CHINA by Prof. Jinxiu Yan (Jenny Yan)
Since 1980s, tunneling and underground works has been developing rapidly in China. Especially, in the past 15 years, the length of the tunnels built is 3 times the total length of all tunnels built before the year of 2000. Up to the end of 2015, around 40,000km tunnels have been built in China, including railway tunnels, highway tunnels, metro tunnels as well as water tunnels. Moreover, around 10,000 km tunnels are currently under construction and a large number of tunnels under design to be built in the near future. China has been the largest tunneling country in the world and around 70% of world tunneling activities are going on in China. Those tunnels, with different lengths, different size and different use, have been built by a variety of methods. Because of variable geology in China, the vast tunnel projects have been built across almost all types of complex geology and surrounding situations. This paper will present the tunneling development, the state of art of tunneling (for railway tunnels, highway tunnels, metro tunnels and water tunnels), and the challenges of the future tunneling, such as "long" (super long tunnel), "deep" (extra deep overburden), "big" (big cross section), "high" (high ground stress) and "complex" (complex geology) etc..
3. BUILDING RESPONSES DUE TO DEEP EXCAVATION FOR MUZIUM NEGARA MRT STATION, KUALA LUMPUR by Ir. Khoo Chee Min
Muzium Negara underground MRT station was constructed within 16m of the National Museum, a historically significant structure in Kuala Lumpur. The museum main building is founded on shallow footing in Kenny Hill formation. The 27m deep station excavation was constructed using diaphragm walls and top-down method. Built in 1960s, the building may had previously undergone some degree of settlement due to a series of upgrading works over the years before the station box excavation. It was therefore considered it would be more sensitive to ground movements making the challenge of controlling the impact of construction settlement even greater. This paper presents the actual performance of the settlement sensitive heritage building responses to a deep excavation carried out in close proximity.
4. GEOLOGY VIS-À-VIS TUNNELLING IN THE KUALA LUMPUR AREA by Ir. Tan Boon Kong
Geology has a direct impact on tunnelling works. Risk assessment of potential geohazards due to various ground conditions (i.e. geology) is an important component in the planning and execution of tunnelling projects. This paper discusses the geology of the Kuala Lumpur (KL) area and its impact on recent tunnelling works carried out in the area. The rock formations encountered in recent tunnelling projects in the area include Granite, the Kenny Hill formation, and the KL Limestone. Since these rock formations have their own unique features and characteristics, they impact tunnelling works differently. For example, granite exhibits distinct weathering profiles with possible boulders in the grade IV zone; hence potential soil-rock mixed face with boulders for the Tunnel Boring Machine (TBM). The Kenny Hill formation comprises interbedded Quartzite and Phyllite, with the former having very high strength (Unconfined Compressive Strength, UCS of up to ~ 300 MPa) which impedes the progress of TBM. Quartzite is also highly abrasive to TBM cutters since its mineralogical composition is basically 100% quartz or silica (SiO2). The KL Limestone is well known for its karstic features (irregular or pinnacled bedrock profile, cavities and solution channels, slump zone with Standard Penetration Test, SPT N = 0, etc.) which pose serious geohazards to tunnelling works. In addition, superficial deposits such as Alluvium and Mine Tailings also pose potential problems since they are weak materials/soils. Mining slime deposits are particularly treacherous with SPT N = 0. The occurrence of mine tailings in the Limestone pinnacle zone can potentially trigger a sinkhole when intersected by a TBM. Finally, geological structures such as major faults, quartz and granitic dykes which are prevalent in the KL area can also impact on tunnelling works. Tunnelling through major faults or fault zones would encounter highly crushed/brecciated rock weathered to soils (i.e. weak zones). Quartz dykes consisting of crystalline quartz would be highly abrasive to TBM cutters and impede TBM progress. Granitic dykes encountered tend to be weathered to weaker materials/soils. In any case, faults and dykes would serve as conduits for groundwater ingress into the tunnels. In Singapore latest MRT Line construction phase, Havelock Station is located beneath Zion Road and there are five entrances connected to the station, known as Entrance A, B, C, D & E. An innovative method of using Rectangular Tunnelling Machine (RTBM) has been employed for the first time in Singapore for the underpass construction linking Entrance E & D to the main station with trenchless method. Compare with the original cut and cover method, advantages of trenchless method are such as reducing disruption and construction impact on Zion Road and preventing adverse impact to the underlying utilities and services. It will also greatly improve the productivity of construction for this underpass and reduce the duration required for the completion of this underpass structure. There could be difficulties in ground settlement control, deviation from the horizontal axis, roll of shield body, higher requirements on strength of shield body for large width of cross section. This talk will discuss the challenges during tunnelling work and design on the rectangular tunnelling machine and ground improvement
5. CHALLENGES OF UNDERGROUND SPACE DEVELOPMENT IN CONGESTED URBAN REGION OF KUALA LUMPUR by Ir. Dr. Ooi Teik Aun
This paper discusses two case histories of urban underground space development one in a mixed development of approximately 9 ha (22 ac) in the southern region of Kuala Lumpur city, the site consists of variable quality of limestone formation. The development is divided into 3 phases with Phase 1A having limestone bedrock varying from 3m to 45m below the existing ground level. The site is bounded by the Cochrane and the Maluri Klang Valley Mass Rapid Transit (KVMRT) stations. The quality of limestone bedrock at the shallow part of the site has average RQD (rock quality designation) of 0 percent and 70 percent while that of the deep part has average RQD of 0 percent to 80 percent. The Unconfined Compressive Strength (UCS) of the limestone below the basement 3 level varies from 20MPa to 80MPa. Contiguous Bored Pile (CBP) walls were used at the north and south sides of the site. The length of the CBP wall varies from 13.5m to 24m below ground level. Open cut method was adopted on the east and west side to the basement 3 levels with a slope height of 13m. Raft foundation was used for basement with limestone outcrop while bored piles were used for those deeper parts of the site. The other site is the Damansara Town Centre which was constructed in 1983 to 1986. The nine blocks of eight to ten storey buildings were founded on bored pile and H-pile foundations located in the Kuala Lumpur Kenny Hill Formation. The construction of two MRT stations within its vicinity and the rapid development in the surrounding areas has prompted the developer to decide to redevelop the more than nine acre site into a high density high rise mixed development consisting of five levels of basement car park, four levels of podium for commercial, nine blocks of 18 storey office towers and three blocks of more than 40 storey residential towers with a total built up area of 300,000 m2. The original development has four levels of basement car park resulting in the formation level of the foundation pilecap to be at RL47m. The existing retaining wall system is counterfort RC wall. The bored piles and H piles were approximately 18 metre long below the pilecap level. The redevelopment will have additional 5 levels of basement resulting in the need to install new contiguous bored pile (CBP) wall / diaphragm wall (Dwall) from ground level with diaphragm walls at the vicinity of the MRT stations. Instrumentation of CBP/Dwall is required to ensure lateral wall movements are within the allowable limits.
6. THE IMPORTANCE OF PROTECTING OUR BUILDINGS AND INFRASTRUCTURES & INNOVATIVE RESTORATION TECHNIQUES by Ir. Thavanendran Mahalingam & Er. Abishek Muurthy
Buildings are generally susceptible to gradual dilapidation over time. This problem is further exacerbated by the robust development in highly densed central business districts with the construction of various underground infrastructures within close proximity to old buildings. More than often such buildings are usually compromised and in need to be demolished if its structural integrity is not intact. Hence it is utmost important that diligent long term measures are put in place to ensure these buildings are constantly maintained and its structural integrity and serviceability is not compromised at any cost. There is a growing need for Engineers to resort to innovative solutions to solving the degradation of buildings other than demolition. The cost effective way to restoring and enhancing a building is by structural strengthening and innovative retrofitting. This paper discusses the actual experience encountered in selected buildings failures and deterioration and the solutions to restore and enhance the functionality of the buildings. The challenges faced in the restoration works as well as lessons learned from past failures are also discussed.
7. DESIGN AND SUPERVISION OF BORED TUNNELLING WORKS IN SOFT GROUND by Ir. Er. Dr. ONG Chee Wee, Victor
It is increasingly economically viable to build underground tunnels as precious urban lands can then be utilized for the development of buildings. However, during tunnelling, the soil around the tunnel often moves towards the tunnel opening, especially in soft ground condition. The resulting ground movements induce additional settlement, axial force, deflection and bending moment on adjacent foundations. As a result, the foundations may not be able to resist the loads induced by tunneling nearby. As more and more underground tunnels are being constructed in densely populated area, an appreciation and understanding of tunneling issues in soft ground is critical for the safety and progress of society. This talk aims to give an overview on design and supervision of bored tunnelling works in soft ground.
8. THE APPLICATION OF GEO SPRAY SYSTEM FOR TUNNEL REPAIR & PIPELINE REHABILITATION by Ir. Neo Boon Kheng
This paper discusses the application of GeoSpray, a spray applied system for a range of rehabilitation applications ranging from utility pipelines to large tunnels. This paper will also include case studies from recent projects. The high strength, ultra-low porosity GeoSpray geopolymer fiber-reinforced material is made from natural mineral polymers and recycled industrial waste. This material is designed specifically for corrosion prevention and structural enhancement of utility tunnels, sewers, chambers, manholes, potable water mains and a host of other critical structures. GeoSpray is engineered and blended suitable for pouring, placing, trowelling, spraying or centrifugal spin casting application techniques. GeoSpray geopolymer system provides cost effective, environmental friendly rehabilitation and structural improvement solution to degrading infrastructure
9. ADVANCES IN TUNNELLING IN URBAN AREAS by Mr. Don Hall
In today’s environment of increasing traffic congestion in cities clients are looking to reduce the impact on the surface during construction works. Following the successful completion of a CREG project in Zhengzhou, China, which involved jacking four (4) tunnels with two rectangular EPB Box-jacking machines and the start of the Thomson Line T221 contract in Singapore CREG are now looking at innovative ways to use box-jacking to save space in inner cities. This presentation will show the status of the T221 project and introduce the new concept of applying this LESSONS LEARNED FROM DESIGN OF DEEP EXCAVATION IN KENNY HILL FORMATION OF SPT ’N’ >50 by Ir. JOON GEI TAN & Ir. Dr. LEAN HOCK OOI This paper presents the lesson learned from deep excavation in Kenny Hill Formation of SPT ‘N’ >50. The technology to constructing underground car parks and storage areas deep excavations are for the Klang Valley MRT underground stations; which have retained depth of up to 33.5m. The stations diaphragm wall’s predicted and measured displacements and strut forces are compared and discussed. The methods to obtain and tests SPT’N’ >50 undisturbed samples are elaborated. The results of the laboratory tests, the parametric studies using Finite Element back analyses to match the measured deflected diaphragm wall displacements and the lessons learned and possible optimisation are discussed. LESSONS LEARNED DEEP EXCAVATION WORKS IN KUALA LUMPUR KARSTS – SOME CONSIDERATIONS by Ir. Dr. LEAN HOCK OOI and Ir. Dato’ T. T. HA In Kuala Lumpur Malaysia, many prestigious structures are founded in Kuala Lumpur Limestone. The Kuala Lumpur limestone is generally classified as extreme tropical karst. The karst features reported include but are not limited to the highly variable bedrock profile, and intricate three dimensional network of solution channels littered with cavities, vertical cliffs and overhangs. The challenges of civil engineering works in limestone have been acknowledged by many designers and contractors and it was given a special session in the 8th South East Asian Geotechnical Conference (SEAGC 1985) in Kuala Lumpur. In spite of the complexities related to karsts, Malaysians have successfully completed the large diameter SMART tunnel and many deep excavations and foundations in such challenging ground conditions. This paper presents the challenges and risks related to deep excavation works in karsts and some of the possible measures to minimize
For more info, please download the flyer
|