Prathuang Usaborisut

Several contributions to soil compactibility induced by cyclic loading test

Abstract 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/m 3 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.

Progress in Mechanization of Sugarcane Farms in Thailand

Sugarcane is an important cash crop of Thailand. With a contribution of 5.5% to the total world production, Thailand is the fourth largest producer of sugarcane next to Brazil, India, and China. During the crop year 2014/15, about 103.7 million tonnes of cane was produced with a national average of about 76.6 tonnes/ha, higher than the world average of 69.5 tonnes/ha and also of those countries ranking higher in terms of total production. The major sugar-producing regions of Thailand are northeastern, central, and northern parts, for which the share of production was 44.59, 28.98, and 26.43%, respectively, in crop year 2016/17. Sugarcane is labor intensive for almost all operations, from land preparation to harvesting. Machinery can help in labor saving and timeliness of operations, improving quality of work, reducing drudgery and operation cost, and more importantly, increasing effective utilization of resources. Sugarcane growers are facing serious problems such as labor shortage and high minimum wage for manual labor. Sometimes, mishandling of a problem may result in other serious consequences. For instance, burning sugarcane to reduce labor requirement in harvesting may lead to other problems. Mechanization can play a vital role in solving problems and in improving efficiency of the present sugarcane production system. This paper presents the progress of farm mechanization in sugarcane cultivation in Thailand through on overview of the machinery used in different farm operations based on farming practices as well as their impact and also factors influencing the extent of mechanization in this crop. Future prospects of mechanization are also discussed.