| 1. Introduction | | | | found to be in order;b) Qualified persons has fully |
| Given the wide network of the MRT system in | | | | demonstrated and confirmed that it is feasible for the |
| Singapore and rate of building development, the | | | | development works to fully meet the technical |
| potential of land development along MRT lines is very | | | | requirements of Section 10 to 12 of the "Code of |
| high. In order to carry out such development, it is very | | | | Practice for Railway Protection". |
| common to see building structures and basement | | | | *Application for such exemption can be made using |
| structures adjoining to or directly above the existing | | | | FORM LTA DBC RAIL EXEMPT which is available in |
| MRT lines. | | | | the "Guide To Carrying Restricted Activities within |
| Such construction must be carried out in a manner | | | | Railway Protection and Safety Zones". |
| according to the Code of Practice to avoid detrimental | | | | 3. Protective Measures |
| effects on the sensitive MRT structures. It is important | | | | Protective measures are essential when carrying out |
| to have proper and adequate precaution/ protection | | | | construction work in close proximity to the MRT |
| measures incorporated in the design and construction | | | | structures. The protective measures can include the |
| works to avoid such effects. | | | | following:a) Rigid retaining structures (e.g. diaphragm |
| 2. Safety and Protection | | | | walls);b) Proper construction methods (e.g. top down |
| 2.1 Code of Practice for Railway Protection | | | | construction methods);c) Good water tight retaining |
| New developments that are taking place in close | | | | structures;d) Water recharging wells;e) Soil |
| proximity to existing MRT lines are subjected to the | | | | improvement techniques (e.g. jet grout);f) Debonding of |
| approval of Land Transport Authority (LTA). Full | | | | piles and diaphragm walls in the 1st and 2nd |
| compliance of the technical requirements must be | | | | Reserves;g) Silent Piler. |
| achieved as specified in the Code of Practice for | | | | Instrumentation are also necessary to monitor the |
| Railway Protection. The Code requires the developers | | | | changes that might affect the tunnels during the |
| to ensure that the movement of the MRT structures is | | | | construction works. |
| limited to the following requirements:a) Movement in | | | | 3. Conclusions |
| any direction limited to 15mm;b) Rotation of the tracks | | | | 1) Good planning and control system consisting of |
| limited to 1:1666 in any plane. | | | | Codes, Guidelines and proper procedures are essential |
| However, there are cases where the allowable limits | | | | in ensuring the successful execution of new |
| may be adjusted according to the site conditions | | | | developments near existing MRT structures and |
| (Doran, et al, 2000). Special care has to be taken when | | | | maintaining public safety. The establishment of the |
| undertaking installation of piles and diaphragm walls | | | | allowable limits by local authorities based on design |
| with the 1st and 2nd Reserve Lines. | | | | conditions and field performance provide a useful guide |
| Safety measures must be adequately in place | | | | to the engineers/contractors of these critical projects. |
| especially during the installation of piles and diaphragm | | | | 2) Construction activities within the Railway Protection |
| walls within the 1st and 2nd Reserve Line of the MRT | | | | Zone shall be regularized and controlled by the Code |
| structure. Usage of permanent casings can minimize | | | | of Practice for and executed under the supervision of |
| the potential for any imposed stress on the MRT | | | | competent engineers for minimizing detrimental effects |
| structure for installation of piles and diaphragm walls. | | | | on the existing MRT structures. |
| 2.2 Planning/ Design Consideration | | | | 3) The effects of construction on the existing MRT |
| Necessary permits from LTA must be approved | | | | structures hall be properly evaluated by necessary |
| before any new development in close proximity to | | | | analyses in the design and verified by suitable |
| existing MRT structures can take place. The various | | | | instrumentation system during construction. |
| documents to be submitted to LTA for approval | | | | 4) The application of suitable protective measures, e.g. |
| includes the following:a) Method Statement of Work;b) | | | | rigid retaining system, soil improvement techniques, |
| Instrumentation Proposal;c) Review Levels for various | | | | special equipment and advanced automatic monitoring |
| instruments. | | | | systems are fond with significant contribution to the |
| All documents are to be submitted by the Qualified | | | | safety control of underground MRT structures in close |
| Person (QP) to LTA before the undertaking of any | | | | proximity to construction sites in view of its sensitivity |
| construction of such nature. Site activities are strictly | | | | and restricted accessibility. However, proper |
| allowed to proceed after approval by LTA. For | | | | interpretation of the instrument readings, application of |
| construction of underground tunnels, exploration, | | | | good engineering judgment and supervision by |
| foundation works and development work which would | | | | competent geotechnical engineers are needed. |
| involve the use of a crane, an application for the | | | | References |
| exemption of the provisions under the Rapid Transit | | | | 1) Land Transport Authority 2000, Code of Practice for |
| Systems (Railway Protection, Restricted Activities) | | | | Railway Protection, Singapore |
| Regulations* shall be made by the qualified person in | | | | 2) S.K.Kong, Moh and Associate Pte Ltd, Safety |
| writing. | | | | Control for Development Adjacent to Existing MRT |
| LTA will approve the developmental proposal in writing | | | | Structures , Singapore |
| if the following requirements are compiled with:a) | | | | 3) Doran S.R., Wood T, Tham S.K., Copsey J.P. Shirlaw |
| Qualified person has complied with the requirements of | | | | J.N. & Wen D. 2000, The Assessment of Limits |
| Clauses 4.2 to 4.5 of the "Code of Practice for | | | | for The Movment of Subway Tunnels and |
| Railway Protection" and that all items submitted are | | | | Trackworks Due to Adjacent Construction. |