Abstract:
This study aims to study the effects of seat cushion made from natural rubber, nitrile rubber and butyl rubber attached by rubber glue on reducing vibration among drivers who have to operate the vehicles equipped with vibratory hammer pile. In this cross-sectional study, the selection criteria for the informants has specifically focused on the drivers who operate the vehicles equipped with vibratory hammer pile at one of the dike construction sites in Ayutthaya Province. 15 Informants have participated the study on voluntary basis. They do not have muscle and bone related illnesses. Data collection tools include the questionnaire on general information, questionnaire to assess the lower back pain and the vibration meter. The study has shown that the average age of the sample group is 43 years-old (±10.62). The average weight is 68 kilograms (±6.6). The average working hours of the driver is 8 hours per day, and the average duration they have to drive continuously in one day is 4.6 hours per day (±1.18). Regarding experience in operating the vehicles equipped with vibratory hammer pile, the average period that the driver have been working is 15.87 years (±9.87). The result of the vibration exposure assessment has indicated that before using the seat cushion, 86.67 % of the sample group has been exposed the vibration which exceed the standard recommended by ISO 2631-1,1997 (0.5 m/s2). After using the seat cushion, the number of the informants who are still exposed to vibration which exceed the standard has been decreased by 53.33%. The result of the lower back pain assessment has shown that, before using the seat cushion, 53.33% has high level of the lower back pain symptom. 46.67% has medium level of the pain. After using the seat cushion, 13.33% has high level of the lower back pain symptom. 40% has medium level of the pain. The findings from the comparison of the vibration exposure before/after using the seat cushion has shown that before using the seat cushion, the X axis is 0.124 m/s 2, the Y axis is 0.077 m/s 2, the Z axis is 0.366 m/s 2. After using the seat cushion, the vibration scale has been changed to 0.062 m/s 2, 0.011 m/s 2 and 0.282 m/s2 respectively. The P-value is at 0.001. In terms of statistical significance, the comparison of the average scale of the vibration acceleration in each frequency before and after using the seat cushion has indicated that the statistical significance at 0.05 level of 0.8 Hz, 25 Hz, 31.5 Hz, 40 Hz, 50 Hz, 80 Hz frequencies. The P-Value is equivalent to 0.034, 0.001, 0.001, 0.001, 0.012, 0.041 respectively. The sample group has high satisfaction when using the seat cushion, the average scale is 4.04.
From the result of the study, the seat cushion can reduce the physical effects caused by vibration to the employees who are the sample group in this study. The lower back pain has been alleviated and they have high level of satisfaction when using the seat cushion.