The track alignment design of TIAA MRT construction includes horizontal and vertical alignment. The horizontal alignment of the main track is designed as circular curves wrapped by spiral curves at both ends and then connected to the linear section. For side tracks and depot tracks, the horizontal alignment is designed as circular curves and linear sections intertwined with vertical curves connecting the linear gradients.
On-site measuring tasks include control survey and construction measurement. As track construction is the following construction to civil engineering, when transferring measurement data from civil engineering tender to track construction tender, control point and bench mark (B.M.) surveys should be performed to avoid station structure invasion. Control point measurement is performed to control surface area location. The measurement method adopted compound traverse survey in which considered the civil engineered transfer control points of station area as the starting side/closure side. As for leveling surveys, the station top B.M. is fixed and we adopted the direct leveling method using a precise automatic level measuring to and fro the station.
Prior to track construction, necessary construction measurements are performed. To complete such measurements, the first step is to set out center tracks according to traverse coordinates from the alignment data. Then, proceed on the track panel assembly and complete the route center coordinates and elevation random checks. Throughout the track construction period, Leica GRP 1000 Track Measuring Trolley and Total Station Theodolite on the loading server motor are used for on-site measurements. The equipment would be quickly set up as a measurement point and could display immediate measuring results for on-site adjustment. When setting up or transferring a measurement point, it would be directly leveled in which the tread surface height would be compared with trolley statistics. The survey will only continue when the comparison is correct to assure the accuracy of elevated height.
Before pouring concrete onto the track bed, track alignment and elevation tests should be performed by track measuring trolleys. After the test results are confirmed to meet standard, the concrete pouring process could then proceed. Finally, after rail laying and the final alignment adjustment are completed, general construction survey is conducted to assure rail gauge, horizontal alignment and vertical alignment are correct and accurate.