Solving the Problems of Differential Settlement of Pavement Structures in the Bangkok Area

The Bangkok Area is underlain by 12 to 16 m deep soft compressible clay. Pavements on embankments 1.5 – 2.5 m high commonly undergo a total settlement of 500 – 1 000 mm in 10 years. This causes significant differential settlement problems between the bridge approach embankment and bridge structure founded on long piles with bases in the sand layers. Significant longitudinal or cross-sectional differential settlements of the roadway may also take place due to ground conditions. Stability and settlement are always associated problems on soft ground. Solutions that have been implemented in the past three decades include the use of preload embankments, light weight materials, concrete bearing units on precast piles, preloading with prefabricated vertical drains (PVD), and soil-cement columns. Case histories of investigation and analysis of the soil mechanics problems and design solutions by state-of-the-art methods are presented in this paper.