AGILE Tropicana has engaged G&P Professionals Sdn Bhd to assess the impact of the proposed high rise mixed development to the future MRT tunnels as the future KVMRT Line 2 tunnels (Northbound and Southbound) will have its proposed alignment cutting across the project site.

Project Challenges

One of the biggest challenges of this project is to control the movement of the MRT tunnels within the stringent criteria according to Railways (Railway Protection Zone) Regulations 1998 (PU(A) 367 1998). Some of the important criteria are listed as follows:

• Total movement < 15mm in any plane.
• Differential movement < 3mm in 6m (1:2000) in any plane.
• No sheet piles, piles, foundation, boreholes or wells shall be driven within First Reserve.
• For the pile foundation constructed in the Second Reserve, the piles are designed so that they are debonded within the zone of influence of the underground structure and develop all of their load either in shear or end bearing from soil located below zone of influence of the structure.

• To assess the anticipated movement of the MRT tunnels due to the development
• To model complex soil-structure interaction (i.e. MRT tunnels at varying depths and orientations)
• To examine the proposed piled foundation with non-regular loadings pattern that could not be properly modelled and assessed using 2D analysis

THE CHALLENGES

The railway tracks transverse a distance of 350km from north to south passing through subsoils which vary from soft alluvium deposits to dense residual soils. In addition, the geometrical tolerance of the railway tracks is very stringent, especially for trains with high design speeds of 180km/hr. The design performance requirements include differential settlement of not more than 10mm over a chord length of 10m and settlement of not more than 25mm within 6 months after completion.
Hence, various ground treatment techniques were adopted to meet the performance requirements and construction schedules, especially when long stretches of the embankment supporting the tracks traverses very soft to soft alluvium deposits with thickness of 15m to 20m.

DRAWBRIDGE that links Muara North and Muara South (two reclaimed areas on the north and south of Terengganu River) to create a strategic connection between Kuala Terengganu City across the north and south of Terengganu River, which leads all the way to Kuala Terengganu�s Sultan Mahmud Airport. G&P Geotechnics Sdn Bhd have been engaged by Zelan-Hasrat Sedaya Consortium to provide alternative design for pile cap and foundation system of four (4) marine piers (namely Pier P3, Pier P4, Pier P5 and Pier P6).

The subsoil condition is summarised in Figure 1.

Design Requirement

• Vertical settlement of pile group < 10mm.
• Lateral displacement of pile group limited to 20mm in any direction.
• Pile cap crack width requirement = 0.1mm (Table 1 in BS5400-4 �Extreme Environment� for marine structures with concrete surface exposed to abrasive action by sea water).
• Accidental ship impact load.
• Wind load on drawbridge and towers.

Design Methodology

Pile Group Analysis

Pile group analysis was carried out using PIGLET software (soil-structure interaction software for pile group analysis developed by M.F.Randolph).

Design loads were provided by bridge engineer with all the load cases in service limit state (SLS) and ultimate limit state (ULS).

Design Pile working capacity for 1m diameter precast spun pile is 5500kN.

Design Lateral working load for 1m diameter precast spun pile is 135kN.

Pile Cap Analysis

Pile cap Structural analysis was carried out using SAFE version 12

Preliminary Pile Test

Maintained Load Test

The average settlement for 100% working load is 8.98mm which satisfies the design criteria.

Lateral Pile Load Test

Non-linear yielding behavior of the pile deflection is observed during lateral pile load test on site.

Back analysis based on lateral pile load test concluded that the actual subsoil shear modulus is lower than the value adopted in the design assumption. Thus, pile group re-analysis was carried out based on the updated subsoil shear modulus.

Summary of Alternative Design

Original design of 15 nos. of 1000mm diameter bored pile for Pier P3 was replaced with alternative design of 28 nos. 1000mm precast spun pile (combination of vertical and raked piles)

Original design of 55 nos. of 1500mm diameter bored pile for Pier P4 and P5 were replaced with alternative design of:

• 118 Nos. 1m dia. precast spun pile (combination of vertical and raked piles)
• 86 Nos. vertical pile.
• 32 Nos. raked pile
• Pile length = 30m – 36m
• Pile cap area = 1932m²
• Pile cap volume = 7025m³

Initial design of 15 nos. of 1000mm diameter bored pile for Pier P6 was replaced with alternative design of 24 nos. 1000mm precast spun pile (combination of vertical and raked piles).

Slanted Columns & Ring Beams

The A3 block is the main academic block and the largest structure in the university campus with a total floor area of 58 598 m2. This block houses a 7-storeys library with the centre of each floor being a large atrium space with an increasing diameter at each floor, featuring the structural slanted columns that have been placed at its perimeter. The slanted columns and the ring beams were further analysed to confirm the behaviour of the unique structural elements. The ring beam with the floor slab behave like a tie beam and restraints the movement of the slanted columns in the horizontal direction.

Sloping Roof

The A1, A2, A4, and A5 academic blocks are the other academic blocks with a total floor area of 21 854 m2 over 5 floors. Within these blocks, all the teaching and learning facilities such as lecture halls and teaching rooms are provided. At the centre of each floor is a large atrium at each floor where large circular voids were created. The roof structure for A1, A2, A4 and A5 blocks was designed and constructed as reinforced concrete structure due to architectural requirements on the laying of the roof tiles. Hence, the casting of the sloped roofs were done in several layers to achieve the required finish quality and consistency.

1. Casting sequence of concrete roof beam and slab in a few of horizontal layers
2. Schematic diagram indicating loadpath for ring beam (tension) and slanting column (compression)
3. Constructed slanting columns and ring beams
4. Aerial view of A4 block in construction