TEST FILLS TO FAILURE ON THE SOFT BANGKOK CLAY

This paper describes test fills to failure, to study the bearing capacity of soft Bangkok clay. The tests were conducted while reassessing the design and construction of a new highway between Bangkok and Siracha in Thailand. The stability calculations for the highway were based on the vane shear strength of the clay, which varied regularly along the route. The clay is 15-25m deep and has a drying crust less than 1m thick, but the weathering effect penetrates to 3-4m deep. Before construction began, three test fills were built to failure on this deposit. One section was built with a berm, one without a berm, and one on a layer of 25cm diameter bamboo fascines. The fascines were placed with centres 50cm apart on one half of the third section and without spacing on the other half. The failures developed several days after the critical fill height had been reached. At failure or some time before it, a longitudinal crack developed in the central part of the fills; total failure followed this cracking. In that part of the third section, where fascines were placed without spacing, no cracks were observed in the central part of the fill at failure; this indicates that the bamboo reinforcement was strong enough to prevent lateral movements. The results of stability analyses and relevant laboratory tests are given.