Lime-stabilization operations began on 27 March 1962, and were com- pleted on 20 January 1965. A 10 cm. thick layer of sand was placed full width of the roadbed on top of the subbase and under the concrete pave- ment. The sand served as protection
to
the lime-stabilized layer. as a cushion for the concrete pavement, and as a path for the escape of water which might penetrate from above or rise from below. The sand, within the limits of the concrete pavement forms, was compacted by light-weight self-propelled vibratory rollers.
Borrow Pits
North of km. 32. where the con- crete pavement ended and the 5 cm. thick asphalt concrete surface course began, it was more economical to con- struct the embankment with layers of imported select borrow, subbase, sand and base course materials, than to use lime-stabilization.
For the most part it was possible to provide unclassified borrow from within the right-of-way limits, in suf- ficient quantities to construct the highway embankment. In several localities the right-of-way was too narrow to provide sufficient borrow material because of the railroad on one side or the airport on the other side, and in these localities it was necessary to arrange for borrow pits adjacent to the right-of-way.
In certain areas it was possible to excavate side borrow by hand-labour methods and place it in thin lifts next to the existing road, without interfer- ence to traffic, and this was accom- plished ahead of machine grading operations.
At one point there were more than 3,000 people using hoes and shovels to dig unclassified borrow from right-of-way borrow pits, from where it was carried in baskets for a few steps to where the roadway em- bankment began as a widened section to the existing road. This particular operation was carried on as multiple- private-enterprises, usually by people living close to the highway.
Bangkok Clay being pushed from a side borrow to form an embankment
Because information was lacking in many fields important to highway con- struction in Thailand, TC1 conducted a number of studies calculated to gather authoritative data, that, after this project, should also be helpful for later programmes.
Specialized Studies
TCI also carried out some specializ- ed studies essential to this project. In order that these too might also be used in the future, the results of the studies were prepared as complete re- ports. The printed and bound reports cover these subjects:
Preliminary Report Embankment and Pavement Design. Bangkok- Saraburi Highway.
Highway Design and Control Test- ing of Lateritic Soils. By the CBR Method.
Soil Stabilization with Lime. Preliminary Report. Andesite Rock from Saraburi and Hin Kong Area. Lift-Span Operation Procedure Design Report, Prestressed Con- crete Barrier Rail, Bangkok-Sara- buri Highway.
CPHEZ
CONSTRUCT
In addition to these. TCI conducted two other specialized studies, the re- sults of which were used in the con- struction of the highway. One of these was the design and installation of fibrous wick vertical drains. These 3 in. diameter drains were placed by the engineer's field staff, in drainage fields where exceptionally high bridge built, at locations where it was rather approach embankments were to be
certain that the embankment load would cause foundation failure, unless some provision was made to con- solidate the saturated underlying soil. The drains extended as deep as 16 metres, and were placed on 2.5 metre centres, within the area to be covered by the highway embankment.
The small bore drains served exact- ly the same as large-diameter orthodox sand drains, but cost only a fraction as much to install, and were even more successful than anticipated. Jute was used as a wick, wrapped about a stiff wire, which was jetted into the saturated soil.
At three of the installations ex- periments with electro-osmosis were tried, but were only partially success- ful in accelerating the movement of pore-water toward the drains. It was discovered that much of the underly- ing soil had a fairly high salt con- tent, which reduced the resistence to the current applied to the ranges of the vertical drains, which of course reduced the effectiveness of the elec- tro-osmosis attempt. In every other way the vertical drain systems were highly effective, serving to control the consolidation of the material under the loading of the approach embank-
ment.
General Criteria
The criteria were adapted principal- ly from the American Association of State Highway Officials' (AASHO), "Policy on Geometric Design of Rural Highways". This was in ful- filment of a requirement in the en- gineering contract, which stipulated that design be in accordance with modern American highway standards,
Pouring concrete on section D
Far East Architect & Builder October, 1966
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