Microstructure investigation of soft clay after a vacuum PVD second improvement: a case study in Bangkok area Thailand

This study first demonstrates the microstructural changes of soft Bangkok clay at a real construction site following vacuum PVD modification of soft clay at a − 9-m elevation obtained from Thailand’s Suvarnabhumi Airport. In contrast to the undisturbed soil and the first-improvement soil, the second vacuum PVD improvement transformed the face-to-face orientation of the soil structure into edge-to-face flocculated particles. This approach also greatly affected the inorganic NaCl salts leaching from the pore water, resulting in stronger bonding with less soil permeability and an improved consolidation of soil structure. The repulsive interactions between the soil particles lowered the average liquid limit and plastic limit values, which contributed to the edge-to-face flocculation of the soil particles and greatly increased the shear strength. Vacuum PVD with a second improvement is a highly effective solution for raising the settlement rate and minimizing the settlement time to improve soft clay with low strength and high compressibility.