1 A newsletter published by Projects Division, MTR Corporation P. 5 - 6 The Application of RFID for XRL Contract 816A Environmental Control System 無線射頻辨識於高鐵工程合約816A 環境控制系統的應用 P. 7 - 8 WIL & SIL(E) - “In Case of Fire; Do Not Use the Lift” True or Not? 在西港島綫及南港島綫(東段)新站 「如遇火警,切勿使用升降機」 是對是錯? Dec 2013 Issue No.33 P. 9 - 10 SIL(E) 3 Months Early Degree 1 Access for WCH and OCP 南港島綫 (東段)黃竹坑站及海洋公園 站提早3個月取得「進度一」 People Development Collaboration & Trusted Partnership Projects Delivery Effectiveness SCL Contract 1106 Pillbox Relocation 沙中綫工程合約1106 碉堡遷移
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1
A newsletter published by Projects Division, MTR Corporation
P. 5 - 6 The Application of RFID for XRL Contract 816A Environmental Control System無線射頻辨識於高鐵工程合約816A環境控制系統的應用
P. 7 - 8 WIL & SIL(E) - “In Case of Fire; Do Not Use the Lift” True or Not?在西港島綫及南港島綫(東段)新站「如遇火警,切勿使用升降機」是對是錯?
Dec 2013Issue No.33
P. 9 - 10 SIL(E) 3 Months Early Degree 1 Access for WCH and OCP南港島綫 (東段)黃竹坑站及海洋公園站提早3個月取得「進度一」
People Development Collaboration & Trusted Partnership Projects Delivery Effectiveness
A pillbox constructed during the Second World War and located in the Tai Hom Village site was found to be in conflict with the diaphragm wall works for the new SCL station at Diamond Hill. In order to preserve this structure, it was decided to relocate it in one piece to a storage location at the edge of the worksite boundary. From initial surveys it was found to be constructed from a weak concrete base of varying thickness and hollow concrete blocks forming the walls. The blocks were interlocked but without mortar in the joints. The roof is a lightly reinforced concrete dome found to be of very low grade weak concrete.
The Planning
A plan was developed between MTR, the contractor, design teams and Government departments to support the pillbox and transport the whole structure on a flatbed trailer. The structure was analysed to determine how much movement the structure could withstand without causing failure, and a series of monitoring trigger levels was established. Experts from the UK in the field of ground movement monitoring were consulted and it was agreed that further monitoring by fibre optic cable should be utilised for the safety of the structure. This is a relatively recent development, and a company from Switzerland were contracted to perform the measurements.
Fibre Optic Monitoring
A fibre sensor cable of up to 70m in length was installed around the inside of the structure, and at least 10mm of sensor was fixed to the inside wall with epoxy glue at intervals of 50mm to 100mm. At every location where the sensor is fixed the strain development is monitored to detect movement. Readings were taken hourly at first and more frequently at crucial moments of the construction and during the transportation.
Project Link Issue No.33December 2013
People Development Collaboration & Trusted Partnership Projects Delivery Effectiveness
3D model of the structure during the planning stage survey規劃階段測量時碉堡結構的立體模型
The pillbox before relocation works commenced遷移工程開始前的碉堡
Close up of the sensor cable showing the epoxy glued sensor locations感應線的近貌,顯示以環氧樹脂膠固定的感應器位置
Fibre optic sensor cable installed inside the pillbox安裝在碉堡內的光纖感應線
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Project Link Issue No.33December 2013
Support Work
A steel framework was constructed around the inside of the pillbox to support the dome roof. Eight steel H-Piles were driven down 12m into the ground, four on each side of the pillbox. These would eventually act as stilts that would support the pillbox before transportation.
A concrete retaining ring wall was cast around the pillbox base to a depth of 500mm to retain the soil the pillbox base is sitting on. The retained soil was grouted with microfine cement to bind it together and effectively strengthen the base. The grouting pressure was kept low and no movement in the structure was detected.
A continuous horizontal pipe pile raft was constructed under the pillbox with only 500mm of cover to the base slab. Drilling speed was kept low to prevent heave damaging the structure. During this time a steel plate wrap was formed around the outside of the pillbox to prevent the block work wall
construction from moving due to the lack of mortar in the joints.
The pipe piled raft was to be supported on four steel beams placed perpendicular to the pipe piles and welded to the H-piles at each end. The two ends were excavated and supported on the steel work with simple construction. For the two beams in the middle of the structure, two timber headings were constructed and the beams placed inside. This minimised the amount of excavation before all four beams were installed and welded to the H-piles. The structure was now supported on the raft and connected to the H-piles acting like stilts.
Bulk excavation under the pillbox could now commence, settlement by this point was approximately 7mm in uniform settlement across the structure. By the end of the bulk excavation this had stabilised at a maximum of 16mm. Again very little differential settlement was seen and the strain inside from the fibre optic was still showing no movement.
Once excavated a haul road was constructed under the structure all the way to the temporary storage location. A flatbed trailer was brought with the capability to individually adjust the suspension on each of its 36 wheel sets to ensure the pillbox structure was not put under stress during the move.
Transportation
Once the flatbed was in place under the structure the rear two H-piles were cut. Once this section of the structure settled, strain was detected in the entrance section of the pillbox by the fibre optic monitoring. The flatbeds hydraulic suspension was adjusted such that the pillbox structure was brought back up to the original position and the strain removed. The front two H-piles were then cut and the hydraulic suspension again adjusted to level the structure. The middle four H-piles were cut two at a time and the structure was ready to move.
Pillbox excavation and installation of supportive beams碉堡挖掘及安裝支撐結構樑
Timber heading under the pipe piles and the beam installed supported by H-piles
管樁之下的木材管道及由工字樁支撐的樑柱
Horizontal pipe piled raft under construction正在建造中的水平管樁筏
End beam in place under the pipe piles and supported by the H-piles at each end
管樁之下的尾樑,每端以工字樁支撐
4People Development Collaboration & Trusted Partnership Projects Delivery Effectiveness
Project Link Issue No.33December 2013
Pillbox showing the 4 beams supported on H-piles, concrete base for the flatbed under construction
碉堡坐落在以工字樁支撐的四條樑,平板拖車的混凝土板建造中
Flatbed in place ready for cutting the H-piles prior to transportation平板拖車已在位,準備好在運送前切斷工字樁
Pillbox being transported to the storage location via flatbed trailer碉堡以平板拖車運到儲存位置
Pillbox relocation complete and awaiting the protective shed to be constructed碉堡遷移工程完成,正等待建造保護棚