Laboratory trial mixes were performed to obtain the optimum mix design of clay-cement admixtures with and without Beestar additive. The cement consists of ordinary Portland cement. Both wet and dry mixing methods were applied. The specified 1000 kPa unconfined compressive strength need to be achieved in the laboratory at 28 days curing period. The specified strength can be achieved by wet (slurry) mixing method with 200 kg/m(3) cement content at water-cement ratio of 0.50. Dry mixing method can produce the specified strength using 150 kg/m(3) cement content. Furthermore, dry mixing method with 1.0 kg of Beestar additive can attain the specified strength with 125 kg/m(3) cement content. The soil-cement deep mixing method (DMM) is currently implemented for repair and rehabilitation of Bangna-Bangpakong Highway, Bangkok, Thailand. The optimum design scheme consists of 0.60 m soil-cement pile diameter, 14 to 16 m pile lengths, 1.50 m center to center spacing and 2.50 m embankment height.

The strength and compressibility characteristics of the treated and untreated samples of soft Bangkok clay are studied in the unconfined compression tests, oedometer tests, constant stress ratio consolidation tests and undrained and drained triaxial tests. The four additives used are flyash, rice husk ash, lime and cement. The addition of 10% cement exhibited significant increase in strength and modulus of deformation and the clay material was changed to brittle material. On the other hand the addition of flyash and rice husk ash exhibited ductile behavior associated with higher strain and low strength. Constant stress ratio consolidation tests indicate that for all values of stress ratio the(e, ln p') relation cluster together. The treated sample showed very small pore pressure development in the undrained test and similarly, small volumetric strains in drained tests. Thus, the behavior of the treated samples is very close to the overconsolidated clay.

Two types of sand compaction pile (SCP) model tests have been carried out to investigate the engineering properties of locally available and low-quality sand in Thailand as well as its suitability for SCP construction materials. The SCP model tests were performed using drop hammer compaction in one case and vibrator compaction in another. The sand samples used in this study were taken from three sources: the Kampengsen, Ayutthaya and Chonburi areas in Thailand. These samples were compacted at three different densities: 60, 70 and 90%. The cone penetration test and standard penetration test were conducted in each set-up under an overburden pressure of 100 kPa. Laboratory tests were also performed to determine the corresponding physical and engineering properties of the three sand samples so as to provide comparison with the results of the field model tests. It was found that these locally available and low-quality sands exhibited satisfactory engineering properties, and can therefore be used as construction materials for SCPs. Moreover, empirical relationships have been derived between ϕ values and SPT N values. Finally, the test results were successfully applied in an example calculation.

This paper presents raft-pile-soil interaction for vertically loaded flexible raft on layered Bangkok subsoil. The piled raft foundation system is approximated to a plane strain case and analyzed using two-dimensional finite difference method. The sub-soil is modeled as a linear elastic material and the raft is modeled as a bema structure under plane strain condition. Meanwhile, the piles are simulated by a series of pile elements, which allow the shear and normal interaction at the pile-soil interface. The soil and interface parameters are determined by back analysis of the pile loading tests. The results from the analysis are compared with the previous studies and reasonably good agreement is observed. The suitability of piled raft foundation in Bangkok subsoil is assessed and general conclusions are also made. The study shows that the piled raft at stiff clay layer transfers a significant proportion (35%) of load directly to the soil.