Vertical Walls with Concrete Facing Panels
TRIVANDRUM - KERALA - India
Airports Authority of India
FLYOVER FOR BRIDGE ACROSS CHAKKAI CANAL
Photo 2: Installation of stone column
Photo 3: Laying of boulders at foundation levels on top
Photo 4: Placement of boulders
Photo 5: Installed Paraweb
FLYOVER FOR BRIDGE ACROSS CHAKKAI CANAL_4
A Bridge was planned to be constructed across the Chakkai canal connecting NH bypass with the new international airport in Trivandrum. The approach ramp for the bridge was to be constructed using reinforced soil (RS) wall concept. The foundation soil was found to have inadequate bearing capacity to bear the load of the RS walls. Soil investigation reports revealed that the subsurface soil primarily consisted of clay upto 3m depth followed by sand with silt upto 4.5m and with traces of clay as deep as 9m. Ground water table was also encountered near the ground owing to the proximity of the Chakkai canal.
Reinforced Soil wall with concrete panels as facia and Paraweb as reinforcement was selected as the best solution in comparison to RS wall with steel strips. T-shaped panels with plain finish were mainly used as facia panels and bottom panels were half panels. Some special end panels and corner panels were also used. The connection between the panels & facia was done by galvanized toggles and loops. PVC dowels were used to connect different types of panels. One side of the approach ramp had a curvature of radius 35m which put forward a great challenge in front of the designers & construction team. Additionally, the width of ramp was less than the length of reinforcing strip- ParaWeb required by design. ParaWeb strips of either side of walls were connected to each other. Initially, a proposal for soil replacement was suggested to improve the bearing capacity of the foundation soil. However, due to high water table, replacement of soil could become a cumbersome and difficult process. Thus, keeping in mind the high water table and excessive consolidation settlements, such a ground improvement technique was to be proposed which would improve bearing capacity of soil, reduce post-construction settlement and also facilitate the process of implementation. Thus, considering all these factors, stone column technique with composite soil was proposed. The proposal got approved by IIT Chennai who also gave the approval for the design.