10.2 Guideway (Girder, Station)
10.2.1 Construction Method
Below the construction method adopted for the Bangalore LRT is explained based on our site survey and information obtained from BMRTL and UBTSL ("Report on Construction Methodology ELRTS Bangalore,""Construction Methodology," and other materials).
The upper structure of the guideway will be manufactured and installed by the incremental launching girder method, which is called the block method in Japan, In this method, upper structure girders are manufactured in 3-m to 4-m thickness segments, transported to the site, and fabricated by the post-tension method,
BELRT will be constructed by the following method.
(1) Foundation Structure
(a) Layout
A center line of the superstructure, bridge piers, abutments and protection walls is set on the ground.
(b) Excavation for cast-in-place piles
Geological survey: To obtain design dimensions, a geological survey is performed for each pile and an SPT test is performed at specified interval. Thus, the groundwater level and the depth of the base rock is clarified for each pile.
(c ) Excavation
For large-diameter piles, the ground is excavated with a BG14 rig device and trimmed with a drop hammer or a large core that uses a diamond bit.
The ground is drilled dry to the groundwater level, beyond which bentonite is inserted into the holes to prevent collapse.
(d) Socketing
The bedrock is drilled to a depth of up to 1.5 times the pile diameter to fix the piles. In the course of this drilling, the rupture strength of the rock is obtained.
(e) Cleaning the hole
Chips and debris are removed from the hole, into which bentonite with a specific gravity of 1.05 is poured. Reinforcing bar cages are inserted into the pile hole along the grouting pipe.
(f) Casting concrete
Concrete is cast through a tremie pipe. Concrete of grade M300 shall be used at a
