Shimla. News Views Post —- Indian Institute of Technology Mandi with Durham University in the United Kingdom have developed suction monitoring setup for soil cyclic triaxial testing to
investigate the impact of climate change on railway embankments.
The study was conducted by Assistant Professor Dr.Ashutosh Kuma of School of Engineerin at IIT Mandi and co-authored by Assistant Professor Dr. Arash Azizi of University of
Portsmouth in UK and Prof. David Geoffrey Toll of Department of
Engineering, Durham University in UK.
The main component of railway infrastructure is the trackbed which is
supported by earthworks. This is mainly used to support the track
infrastructure and carry the load imparted by the moving traffic. The
present design protocols only consider the load developed due to the
moving train thereby ignoring the real case scenario of changing the
natural state of the soil due to ingress and egress of water.
Oftentimes, soil used in earthworks is compacted and remains
unsaturated during its lifetime. Seasonal variations in terms of
precipitation and drought are capable of altering the amount of water
present within this compacted soil mass which can alter the strength
of the embankment.
Speaking on his work Dr. Ashutosh Kumar said, “To address the challenge of
providing sustainable and resilient transportation infrastructure
under the changing climatic conditions, IIT Mandi is working closely
with Durham University UK. We all now understand the reality of
climate change which is causing intense rainfall. Compacted soil is
susceptible to deteriorate under the changing climatic conditions due
to changes in the water holding capacity of the soil causing a
hysteretic loss in the soil strength. In addition, the repeated train
loading can exacerbate the deterioration process that would ultimately
cause premature track degradation and resulting failure.
Understanding the coupled impact of train and environmental loading is
essential to design and maintain the railway embankment against
changing climatic conditions. Therefore, this study developed a setup
within a cyclic triaxial apparatus to monitor changes in soil suction
and deformation brought by traffic-induced cyclic loading and
environmental loading, which can be used to assess climate risk at the
design stage of railway embankments.”
The soil sample used in the study was taken from a 650-km heavy haul
South African coal line that connects around 40 mines to the Richards
Bay Coal Terminal in South Africa.
Explaining the research work, Dr. Ashutosh Kumar, said, “The research
is unique in its kind as it would now allow understanding of the
coupled impact of cyclic traffic-induced loading and environmental
loading on the long-term performance of unsaturated soil present
within the railway embankments. The setup uses a high-capacity
tensiometer developed at Durham University to measure suction and
on-sample displacement transducers to measure deformation within the
soil under the coupled environmental and traffic loading.
Further, Dr, Ashutosh Kumar, mentioned, “We have adopted three testing
protocols. First, under the condition of train loading, we allowed the
water from the soil to drain freely when the soil voids were filled
completely with water as a result of intense rainfall. We then
conducted a test under constant water conditions replicating constant
weather conditions under the given traffic conditions. We followed
this by replicating the condition of the train loading under the
ongoing event of rainfall. This information was used to identify the
potential deterioration of soil strength due to wetting and drying
cycles. The deformation in the soil was associated with water
infiltration leading to a reduction in suction and hydraulic history.”
The results obtained indicate that deformation and reduction in soil
strength are due to the combined impact of cyclic and environmental
loading. The hydraulic history of soil has a predominant impact on its
ability to undergo deformation. The suction monitoring setup can test
the soil sample that has undergone the seasonal variation either in
the laboratory environment or field conditions. This would help to
develop strategies to mitigate climate risk at the design stage of
railway embankments, leading to more sustainable construction. The
novelty of this research was to gain knowledge of changes in the soil
suction and deformation of soil
under the impact of cyclic loading
together with hydraulic loading imposed by the environment.”
