Several contributions to soil compactibility induced by cyclic loading test

To investigate the soil compactibility during the cyclic loading, three different kinds of paddy field soils were prepared so as to clarify interrelationships among stress amplitude ratio, bulk density, soil water content and pore water pressure. The presetting values of specimen include the soil water content(percent dry basis) and bulk density of 25% d.b. and 1.1 Mg/m³ respectively. The relation between the number of cyclic loading and axial strain exhibited an asymptotically increasing trend, converging toward a specific value for each experimental condition. Possible effect caused by elastic–plastic characteristics could be recognized, when axial strain for 0.5 Hz excitation becomes greater than the one of 1.0 Hz under same stress amplitude ratio. When the stress amplitude ratio took 0.1, the absolute value of axial strain of 0.5 Hz was greater than the one of 1.0 Hz, whereas its decreasing trend was recognized in the sequence of silt, clay and silty sand. The qualitative relations between pore water pressure and number of cyclic loading were also examined to scrutinize the effect of effective water pressure to the soil compactibility.     

Cyclic torsional shear loading test for an unsaturated, hollowed specimen using Bangkok clayey soil

Cyclic torsional shear loading was applied to simulate the loading characteristics which take place particularly during quick turning operations of a tractor in the field. Indoor experimental tests using a cyclic torsional shear loading method were conducted to clarify the dynamic behavior of Bangkok clayey soil. Since most agricultural soils in the field are normally unsaturated, this test method was used to better match field conditions. The dynamic behavior of our test soil was observed in conjunction with various factors including stress, strain, loading frequency, bulk density, moisture content, and number of loading cycles. Some related results were also obtained under static loading using a triaxial test method.