The 12.8 km, Thanh Tri, Vietnam ’s largest prestressed concrete bridge, was recently opened to traffic. The bridge running through Hanoi Capital with the section crossing the river being nearly 3.1 km in length will help ease traffic congestion in the city, and facilitate socio-economic development of the city and some other northern localities.
The bridge is over 33.1 m in width with six lanes, including four designed for vehicles to run at a speed of 100 km per hour. The bridge project is funded by Japan’s official development assistance and Vietnam’s reciprocal capital. Construction of the Thanh Tri Bridge look four years and was carried out by a joint venture formed by Japanese firms Obayashi Corporation and Sumitomo-Mitsui Construction Corporation, under the supervision of Pacific Consultants International. The project is managed by the Project Management Unit Thang Long under the Ministry of Transport, Vietnam.
For the first time, modern bridge construction techniques such as the special cofferdam and Movable Scaffolding System (MSS) have been introduced to Vietnam benefitting Vietnamese engineers and workers. Other technologies that were used in this project included horizontal Hacking, remedial works for defected piles that included jet grout column and injection grout.
Horizontal jacking was applied for the Main Bridge of Thanh Tri Bridge. The Main Bridges is a 7- span continuous ridgedframe Prestressed Concrete Box Girder that is 680m. The Main Bridge was constructed using balanced cantilever method. In order to minimize the tensile force of the Prestressed Concrete Box Girder and bending moment of piers due to creep, shrinkage and temperature change which occur after closure of the bridge, horizontal jacking with forces of 6,000 kN 15,000 kN were applied at the four closure sections.
Remedial Works for Defected Piles
The foundation of the Thanh Tri Bridge was done using cast–in– place reinforced concrete piles with diameters of 1.0 m, 1.5m and 2.0 m. When the piles with diameters of 1.0 and 1.5m were drilled using the Earth Drill Method, concrete defects occurred at the bottom of many of the piles due to sedimentation or corruption of drilled walls. The following grouts were applied to correct the defected piles.
(a) Column Jet Grout
Column Jet Grout is a special grouting method used to construct soil cement columns using spouted cement milk, water and air with high pressure. Three Columns Jet Grout were constructed around the defected pile with lengths of 3.0 m to 5.0 m. This method was applied to correct more than 100 defected piles.
(b) Injection Grout
Injection Grout is a low-pressure grout applied at the bottom of the defected piles. This grout was injected through the pipes for Ultra Sonic Logging Test. This method was applied to correct about 30 defected piles for this project.