A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering Geotechnical and Geoenvironmental Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 2009

This study presents the finite element simulations of reconstituted soil specimens and in»situ soil improved with PVD combining vacuum as well as heat preloading. In the laboratory, the results oflarge consolidometer tests of reconstituted Bangkok soil samples were back -calculated and simulated. In case of PVD, a surcharge of 100 kPa was applied. The simulation showed that the settlements reach 91 % degree of consolidation correspondi.ng to 113.9 mm within period of 47 days with the ratio of horizontal permeability at undisturbed zone to horizontal permeability at smear zone, kh/ks, is 3. The back-calculation of the horizontal coefficient of consolidation, Ch, is 1.93. In case of Vacuum-PVD, a surcharge of 50 kPa combining vacuum pressure of -50 kPa were applied. The simulation showed that the settlements reach 92% degree of consolidation corresponding to 114.8 mm within period of 42 days with kh/ks value is 2.7. The back-calculation of Ch value is 2.23. In case of Thermo-PVD, a surcharge of 100 kPa combining temperature of 90°C was applied. The simulation showed that the settlements reach 99.3% degree of consolidation corresponding to 142.8 mm within period of 28 days with kh/ks value is 1.4. The back-calculation of Ch value is 4.17. In case of Thermo-Vacuum-PVD, a surcharge of 50 kPa combining vacuum pressure of -50 kPa and temperature of 90°C were applied. The simulation showed that the settlements reach 99.8% degree of consolidation corresponding to 146.7 mm within period of 28 days with kh/ks value is 1.1. The back-calculation of Ch value is 4.38. In the field conditions, at Second Bangkok International Airport, two cases of conventional PVDs and Vacuum-PVDs were observed. In case of conventional PVDs, embankment was constructed into 3 stages up to 3.8 m height and installed rectangular pattern with spacing of 1 m and depth 10m. Observed settlements of 1.28 and 1.58 m were obtained with 376 and 382 days, respectively. The back-calculation and simulation of Ch value is 2.62 and 2.37 with kh/ks value are 9.2 and 10. In case of Vacuum- PVDs, embankment was constructed into 2 stages up to 2.8 m height combining vacuum pressure of -60 kPa and installed triangular pattern with spacing of 0.85 m and depth 10m. Observed settlements of 1.38 and 1.55 m were obtained with 260 days at two locations. The back-calculation and simulation of Ch value is 3.56 and 4.83 with kh/ks value are 7.3 and 10. at the campus of the Asian Institute of Technology, The cases of conventional PVDs and Thermo-PVDs were observed. In case of conventional PVDs, embankment was constructed into 1 stage up to 6 m height and installed rectangular pattern with spacing of 1 m and depth 8 m. Observed settlements of 239.5 mm was obtained with 207 days. The back-calculation and simulation of Ch value is 6.69 with kh/ks value is 6.2. In case of Thermo-PVDs, embankment was constructed into 1 stage up to 6 m height combining temperature of 75°C and installed rectangular pattern with spacing of 1 m and depth 8 m. Observed settlements of 390 mm were obtained with 207 days. The back-calculation and simulation of Ch value is 8.51 with kh/ks value is 4.1. FEM simulations and back-calculations revealed that Vacuum-PVD is faster than PVD both in the laboratory and field conditions due to the reduce effect of smeared zone and increased coefficient of consolidation during vacuum preloading and Thermo-PVD is more settlement than PVD both in the laboratory and field conditions due to the temperature increase because the viscosity of the pore water reduce