Evaluation of Human Body Vibration in Indian Surface Coal Mines and Prediction of Health Risk based on Health Guidance Caution Zone (HGCZ)

Abstract

The use of Heavy Earth Moving Machinery (HEMM) to perform various surface mining activities is very common in surface mining Industry. Exposure to whole body vibration from HEMM, such as Dumper, Dozer, Loader, Grader etc., has been associated with low back pain and also with the degeneration of intervertebral disc. The weight of evidence in the literature suggests that no reported studies are available with regard to evaluation of HEMM operators based on seat-back measurements, job cycle and postural variability. Further, prediction of health risks of HEMM operators due to exposure to WBV based on ISO 2631-1:1997 Standards are limited and published literature was not found regarding prediction with respect to European Union (EU) Directive 2002 in Indian surface coal mines. Therefore, the objectives of this study are to evaluate the whole body vibration exposure levels during the operation of different types of HEMM and to assess health risks of operators based on ISO 2631-1:1997 Standard and EU Directive 2002. This study was conducted at two mechanized Indian surface coal mines. HEMM operator’s exposure to vibration was measured according to the procedures stipulated in ISO 2631-1:1997 Standard. A tri-axial seat pad accelerometer was used to measure the vibration exposure levels at the operator’s seat-surface and seat-back. For cyclic operations the measurements were taken for the entire cycle of operation, whereas for non-cyclic operation the minimum measurement duration was 20 minutes. The obtained results were analyzed in accordance to frequency-weighted root mean square (RMS), vibration dose value (VDV), and crest factor (CF) as suggested in ISO 2631-1:1997 Standard. The literature survey carried out infers that there lacks reported studies on WBV evaluation of HEMM operator’s with regard to seat-back measurements, job cycle, postural variability and prevalence of Musculoskeletal disorders (MSDs) among dozers operators. Further, studies were not reported pertaining to ergonomic assessment of surface coal miners. In this regard, two mechanized surface coal mines were considered (which are designated as Mine-I and Mine-II in this report) so as to study the WBV of HEMM operators with regard to - seat-back as well as seat-surface measurements, job cycle of dumper and dozer operators, MSDs and postural variability of dozer operators, and ergonomic assessment of surface coal miners. vi Hence, this study is categorized into four objectives. To evaluate WBV of HEMM operators with regard to seat-back measurements, the study was performed on seventeen types of machinery (i.e dragline-1 no., shovel-4 no., front end loader-2 no., drill-3 no., spreader-1 no., crane-1 no., grader-3 no., water sprinkler-2 no.). The obtained results show that among all the machinery under consideration, the measured WBV of grader operators with regard to seat-back was exceeding Exposure Limit Value (ELV) as per EU Directive 2002. Hence, there should be prompt health surveillance especially for grader operators. For both seat-surface and seat-back measurements, z-axis (i.e. vertical direction) was found to be a prominent axis for most of the HEMM. To study the influence of WBV on dumper operators based on seat-surface and seat-back measurements, six dumpers (i.e. 60T-3nos. and 100T-3nos.) were taken as sample size. The measurements were taken for the entire cycle duration (i.e. loading, loaded travel, unloading and empty travel). The results obtained illustrated that haulage (loaded travel and empty travel) was the chief contributor to vibration exposure for both seat-surface and seat-back measurements. Maximum RMS of 1.12 m/s2 was reported during empty travel for seat-surface measurements and 1.09 m/s2 was reported as highest RMS during empty travel task for seat-back measurements. This high exposure to WBV during haulage would be minimized by regular maintenance of roadways and by regulating speed limits. For seat-surface measurements based on RMS, z-axis was dominant axis of vibration for all the dumpers during haulage task, whereas for seat-back measurement the dominant axis varies between x and y. Similarly, the study was conducted on dozer operators to evaluate the prominence of job cycle on WBV based on seat-surface and seat-back measurements. In this regard, eight dozers were considered and the measurements were taken at every phase of job cycle i.e., forward motion (such as cutting and drifting) and return motion (such as dozer travelling in the reverse direction). The study revealed that all the dozer operators were in severe zone (i.e. above HGCZ) with respect to measured RMS value, during forward motion and return motion, irrespective of type of measurements (i.e., seat-surface and seat-back). To evaluate the effect of WVB on dozer operators based on postural variability. Measurements were taken for three different sitting postures of the operators i.e. lean forward inclination with a trunk flexion of 15°, vertically erect posture and lean backward inclination with a trunk flexion of 15°. Among these three postures lean backward inclination with a trunk flexion of 15° was found as a favorable sitting posture for the dozer operators, as in this posture operators are exposed to minimum vibration. To study the effect of WBV on MSDs of dozer operators, subjective assessment was carried out using Standardized Nordic Questionnaire, for which sample size of forty two dozer operators were selected as exposed group. Out of this exposed group, 35 of them (i.e. 83.33%) reported severe lower back pain. Lastly, an ergonomic study of MSDs was conducted on 500 mine workers. The study demonstrated that the largest number of low-back injuries among miners is influenced by design of workplace and the way the work is organized. Hence, there is a need for intervention to mitigate the WMSDs among miners by better design of workplace and appropriate planning of job cycle, particularly in Indian surface coal mines. The thesis consists of nine chapters. The first chapter includes the general introduction followed by the origin and the objectives of the work. The second chapter gives the brief literature review. The third chapter gives the information about instrumentation and methodology. Chapter four comprehends the evaluation of whole-body vibration exposure of various HEMM operators. Chapter five discusses evaluation of WBV exposure of dumper operators based on the job cycle, followed by chapter six which discusses evaluation of WBV exposure of dozer operators based on job cycle and postural variability. Chapter seven discusses assessment of musculoskeletal disorders among dozer operators exposed to WBV. Chapter eight summarizes ergonomic assessment of musculoskeletal disorders among Indian surface coal mine workers. Chapter nine encapsulates conclusions and scope for future work in this research field.