Abstract
The behavior of granular piles with different densities and different proportions of gravel and sand on soft Bangkok clay was investigated. A total of 13 piles were installed with 0.30 m diameter and 8.0 m long using a non-displacement cased borehole method with 1.20 m spacing in a triangular pattern. The piles were grouped into 5 categories. Groups 1, 2, and 3 with 3 piles each, were constructed using sand compacted at 20, 15, and 10 hammer blows per layer, respectively. Group 4 was made of gravel mixed with sand in the proportion on 1 : 0.30 by volume and group 5 was constructed with gravel ; both groups consisted of two piles each were compacted at 15 blows per layer. Four active and 2 dummy piezometers were installed for monitoring pore pressures. The soil properties were investigated by the field vane and pressuremeter tests. The ultimate capacity of each granular pile was determined by using full scale plate load tests. Using the pressuremeter results and the method by Hughes et al (1975), the predicted ultimate pile capacity and load-settlement curve agreed well with the experimental data. The maximum bulge in the pile was observed to be about one pile diameter from the ground surface. It was found that the pile made of gravel with 15 blows per layer (Group 5) yielded the maximum ultimate pile capacity closely followed by the piles constructed out of sand with 20 blows per layer (Group 1). In an earlier investigation (Bergado et al, 1984), it was found that the ultimate pile bearing capacity was 3 to 4 times greater than that of the untreated ground and that the piles acted independently when the spacing was 3 pile diameters or greater.
