Hong Kong : Progress of opening-up investigation in second stage of holistic assessment strategy for Hung Hom Station Extension under Shatin to Central Link Project.
According to the holistic assessment strategy of MTR Corporation Limited (MTRCL) regarding the platform slabs and diaphragm walls of the Hung Hom Station Extension under the Shatin to Central Link (SCL) Project accepted by the Government on December 5, 2018, the MTRCL proceeded to commence the relevant work on December 10. The first purpose of opening up the concrete is to carry out physical investigations at locations with gaps in the documentation, so as to verify the as-constructed conditions of the connections between the platform slabs and diaphragm walls. The second purpose is that, in view of the allegations on the cutting-short of steel bars, the MTRCL needs to open up certain connections between the platform slabs and diaphragm walls for detailed inspection, and to conduct non-destructive tests to verify the works quality of the coupler connections. The locations of opening-up were randomly selected based on a statistical approach.
According to the information from the couplers' supplier, proper installation requirements of a coupler are:
there shall be a maximum of two full threads exposed; and
the embedded length of the threaded steel bar inside the coupler shall be at least 40 millimetres.
The MTRCL uses the phased array ultrasonic examination to verify the embedded length of the threaded steel bar inside the coupler. As the allowable measurement tolerance of the test is 3 millimetres, equipment readings below 37 millimetres are regarded as failing to meet the requirement. The test is carried out by the professional technicians of A.E.S. Destructive and Non-Destructive Testing Limited.
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|Date:||Jan 3, 2019|
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