A MASW Seismic survey was conducted along the pipeline jacking route of Bukit Batok East Ave 2, Bukit Batok (MH1 to 2a), as documented in this report.
The survey sought to explore the depths of rock and potential problems along the pipe jack line.
The survey relied heavily on the Geometrics Geode system, boasting remarkable stability and accuracy of data combined with incredibly rapid acquisition rates
To perform the survey, one person was responsible for controlling the survey and operating the seismic system, while four local staff members assisted with laying out the geophones, positioning, and managing the survey. The seismic system and computer were set up on the ground and all position and distance measurements were documented in field notes. Later, ground marks were picked up and related to the field data. Each seismic survey file was stored in data files on the hard disk and further backed up on secure cloud storage (Dropbox).
Take note of the vibrant blue sections - the one on the left represents the basic frequency and the bent part reveals the shift from 200m/sec in weathered rocks to 800m/sec in unaffected stones, approximately 50 m from the MH1 bus shelter along Line 2a.
Observe the increase in velocity at 14m, pointing to the presence of granite Grade G3 (as interpreted), and the further surge in velocity at 19m that alludes to granite at Grade G2 (as interpreted). Here is an example of the velocity model for the beginning of Line 1 (Line 1, 0m distance from MH2a).
Analysis of our data shows that the shift from G5 to G4 follows an up-and-down trend from depths of 12 to 20 metres. Additionally, the transition from G4 to G2/3 exhibits a fluctuating pattern, ranging from shallow near MH2a (12 metres) to as deep as 22-25 metres at a distance of 100-150 metres, before levelling off to depths of 12-15 metres close to MH1. An alignment between the shaft depth and the rock on the left-hand side is also noticeable.