Suggested
topics for MTech / PhD program
o Tunnelling and ground movement
o Stability of deep excavations
o Shallow embedded structures subjected to vertical and inclined loads
o Dynamic loading of soils
o Finite consolidation
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Past and current
students
Roshan N.S. (ongoing)
Title: Effects of tunnelling below piled foundations installed in sands
The interaction between tunnels and piled foundations is investigated using the large beam centrifuge (4.5 m radius) at the National Geotechnical Centrifuge Facility at IIT Bombay. Tests are conducted at 50g centrifuge environment. The adjacent photographs show setup mounted on the centrifuge arm. The black circle is the tunnel at a known depth below the surface of the ground. The white lines are spaghettis (not clearly visible) which are used to follow the deformation patterns. The tunnel is made up of latex rubber. Potentiometers are used to note the vertical settlement of the piles. The model tunnel is filled with water before the test and this is drained during the test to simulate the collapse. A solenoid valve arrangement is used for this. Pore pressures developed in the tunnel are monitored continuously using pore pressure transducers.
Contact: roshan_ns@iitb.ac.in
Amarnath Hegde (2009)
Title:
Centrifuge Modelling
of Ground Deformation Due to Tunnelling under Vertical and Horizontal
Reinforcement
As infrastructure, buildings and services stretch through
the densely populated and scarcely limited land space, ensuring minimum
disturbance to the routine daily lives of the city is of utmost importance in
tunnel design. In order to fully understand the extent of disturbance due
to tunneling in such tight conditions, a comprehensive knowledge of the
deformation caused by tunneling will be useful. Over the years, tunnel
engineers and researchers have realized that curbing the loss of ground is
futile because of in-situ conditions and ground ambiguities. Hence the
only solution is to control the effects of deformation rather than to totally
stop it.
One of the recent pre-reinforcement methods used in
tunnel excavation is forepoling. This technique allows safe excavation
even in poor ground conditions by creating the longitudinal arching parallel to
tunnel axis. This report discusses the procedure and methodology to study
the effect of forepoles on stability and deformation of tunnel with series of
centrifuge tests in soft clay. This study becomes useful in situations
where Earth Boring Machines (EBM) are nowadays being
replaced by more modern tunnel construction equipments because of health hazard
associated with former.
Another means of pre-reinforcement technique is to
insert the vertical reinforcement from the ground surface down to the tunnel
level. The report also discusses the influence of vertical reinforcement on the
settlement trough due to tunnelling in sands using centrifuge tests. This
method is useful in shallow ground tunnelling where surface settlement affect
the structures relatively close to the tunnel.
(Email:
amarnathhegde@gmail.com)
Subhra Dutta (2008)
Title:
Modelling of tunnel excavation on the geotechnical centrifuge
Considerable ground settlement can occur during tunnel construction. Shape of the settlement trough during tunnel deformation closely follows a normal distribution curve. However, most analytical solutions only approximately represent this profile because of the assumption of uniform radial displacement field around the tunnel during its deformation which presumably exists only at shallow depths. For large diameter tunnels and when non-uniform grout pressure is used, tunnel axis is prone to distortion making these solutions unreliable. This thesis examines experimental results of tunnel collapse in small-scale centrifuge environment. Tunnel walls were represented by pressurised rubber membrane. Cover to diameter ratio of the tunnel and relative density of the sand were the only variables in the tests. All tests were conducted on the large diameter centrifuge at IIT Bombay. The results show that deformation above the crown and width of settlement trough, both increase near to the ground surface. The results are compared to data available in the literature and relationship between point of inflection and tunnel depth is derived
(Email:
subhra_318@yahoo.co.in)
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BA Mir (ongoing)
Title:
Some Studies on Reconstituted Clays
Contact:
E-mail : p7mir@civil.iitb.ac.in
Ph No. +91 22 2576 4305 (Lab)
Raghu Nandan ME
(ongoing)
Title: Re-Investigation on sample preparation
techniques for triaxial testing under monotonic and cyclic loading
Cyclic triaxial equipment in ADsoil
Laboratory, IITB Sand Pluviator equipment in ADsoil
Laboratory, IITB
Contact:
E mail: raghunme@iitb.ac.in
Ph No. +91 22 2576 4305 (Lab)