Bioengineering technology of quick grass establishment for erosion control on railway batters
Creators: name: Fox, James Lawrence
Publisher: name: CQUniversity
Year: 2022
Subjects: subject: 99999 Engineering not elsewhere classified
subject: FOS: Other engineering and technologies
subject: 90305 Rehabilitation Engineering
subject: FOS: Medical engineering

description: The erosion of railway batters is inevitable as they are constructed with soil. The deteriorating batters could undermine the structural integrity of the rail formation. This thesis aimed to research the quick establishment of grass on these steeply sloping batters to minimise erosion. The major research tools used in this investigation included seed germination experiments, quantitative assessment of soil loss due to rainfall induced erosion and single and multi -site field trials to demonstrate large scale application of a bio-engineering approach for railway batter erosion control.<br>Initially research was carried out in a laboratory to address the poor germination of Buffel (Cenchrus ciliaris) grass seeds and to develop ways to advance germination to increase canopy cover. The effects of different germination media, concentration and soaking duration in sulphuric acid (H2SO4) on seed germination were evaluated. Germination was most successful when seeds were soaked for four minutes with undiluted H2SO4. Thus it was established that undiluted H2SO4 treatment may be employed for improving Buffel seed germination, provided safety issues for bulk handling are addressed.<br>Research at the Gregory experimental site presents a comparative field study on rapid grass establishment with different weight ratios of grass species mixtures on batters, aided by drip line irrigation, to reduce erosion. Annual Jap millet (Echinochloa esculenta) and perennial Buffel grasses were primarily used as vegetation covers on experimental batter plots. Results revealed that after three weeks of establishment the annual species significantly reduced soil erosion compared to the perennial species. Alternately after eight months, the slow growing Buffel achieved over 80% cover and became as effective as the rapid growing Jap millet, reducing soil loss by over 70% compared to 0% cover control plots.<br>The single site field trial at Holmes cutting used a gravity driven drip irrigation system to establish the grasses. Through observational research both cuttings at the site achieved an effective canopy cover of 70-80% within 12 weeks, significantly reducing eroded soil subsiding onto the track.<br>The Bauhinia Regional Rail Project (BRRP) was a large scale field application, combining improved germination procedures and advanced bioengineering techniques to establish an accelerated canopy cover. Satisfactory growth was shown by Buffel and Rhodes grasses on the railway batters within a week of seeding with pre - germinated seeds where the irrigation water was secured. The bioengineering techniques showed the feasibility of developing sufficient grass cover within eight weeks after seeding of railway batters.<br>Across these studies, strong evidence can be seen for the advantages of using bioengineering techniques to promote the growth of grass to mitigate erosion on the steep slopes of railway batters.