Multidisciplinary
Geoscientific Studies For The Conservation Of Ellora Caves
Multidisciplinary
Geoscientific Studies For The Conservation Of Ellora Caves
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| Car parking and grazing by stray animals in the open ground in front of Ellora Caves | |
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The cave temples
of Ellora represented by elaborate carvings of gods and goddesses are
the product of three religious faiths. Each system has its individual
style of architecture and these are presented side by side at Ellora.
Caves 1 to 12 are Buddhist, caves 13 to 29 are Brahmanical (Hindu) and
caves 30 to 34 are Jain caves. Cave 16, which is known as the 'Kailash',
is the largest of all Ellora excavations and represents rock cut architecture
at its best. Approximately 3,00,000 cubic feet of rock has been excavated
to carve out this cave. The natural processes of weathering along with scarp retreat and biotic
interference have had a deleterious impact on the sculptures and paintings
in the caves and its environs. Unstable slopes and seepage are the
two major causes of concern.
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| Protection Measures as suggested by GSI at Ellora Caves | ||
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Westface
sculpture
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Damaged
pillars of extreme left cell
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On request of the Archaeological
Survey of India, the Geological Survey of India undertook a programme of
multi-disciplinary geoscientific studies comprising topographic survey
and geological mapping of 0.52 sq. km area, geophysical surveys, geotechnical
studies within and outside the caves, terrestrial stereo-photographic studies
of vulnerable slopes, seismic risk assessment by micro earthquake studies
and environmental impact assessment of the caves and their surroundings.
The Ellora caves are situated at the foot of a N-S trending hill with a relief of about 120 m over extensive plains of the Shivna River to the west. Two basaltic compound pahoehoe flows are exposed on the hill slopes. The caves have been excavated in the lower flow consisting of 18 flow units. The rock here is fine to medium grained, porphyritic, vesicular and moderately weathered. The lower part of each unit is marked by pipe amygdules while a highly vesicular zone characterizes the top. Three sets of primary joints are present. A prominent N-S trending, westerly dipping highly fractured zone with parallel weak planes is seen in front of the caves. Slope stability problems at Ellora are confined to the cave portals and the adjacent inter-cave slopes that bound them. The slopes immediately behind the caves are flatter / gentler and stable. Deep semi-circular scarps, 20 to 37m in height have been formed by water action in nallas near caves 5,17,24 and 29. The outer portions of caves 1 to 9 have perished, creating an overhanging block from which certain parts have been dislodged. Overhangs created by excavation of caves have also become vulnerable at a few places, especially in cave 16. Other than this, certain blocks have collapsed due to separation along unit contacts. Stability problems, which are in general restricted to the outer 1-4 m in most caves are due to overhangs created by differential weathering and also due to jointed and fractured blocks. The cave interiors are relatively stable. The presence of four sets of joints, three vertical and the fourth a steeply dipping set of relief joints along with the fracture zone and cooling cracks, has accentuated weathering and rendered the cave facades and certain slope segments weak. Wherever this fracture zone has intersected the cave openings the outer portion of the caves has collapsed as seen in caves 1- 4, 13 & 14. The relief joints with progressive under cutting of toe have played a major role in the retreat of the slope face by about 5m. |
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Northface
sculpture
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Seepage through relief joint through roof of a verandah | Northface sculpture |
Water seepage
is present in some caves at Ellora, most of which is restricted to cave
frontals / portals. The factors contributing to seepage in the caves
are the fractured facades (caves 1 to 5), thin rock cover (caves 10,
19,23, 24, etc.), presence of soil above the caves which absorbs a lot
of water and releases it slowly, feeding the weak planes in the portals
(caves 1 to 4), poor performance of the existing drains, etc. The contribution
of nalla waters for the seepages is extremely limited. However, a small
nalla above caves 1-2 was observed to feed a concealed crack during a
heavy downpour. Most of the rainwater goes as surface runoff through
the nallas but some saturates the soil. It is this water that causes
seepage. Although elaborate drains are made above the caves, not much
water is conveyed through these. The infiltration points lie up slope
of the drains and the water flows within the fractured zone (under the
drains) and seeps out from fracture zones exposed on the cut faces of
the caves. At a few places easterly sloping unit contacts also form conduits
for water seepage. Terrestrial stereo photographic studies were carried out for rock mass characterization using basic parameters of relative strength, degree of jointing / joint volume and intensity of weathering. This was then used to prepare rockmass distribution & slope protection maps. |
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The general protection measures suggested are as follows:
GSI's recommendation for environmental protection:
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| Seepage through unit contact in a facade | |
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Seepage
from rock soil interface
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| Channel on facade causing seepage | |
Work done by
Central Region, Geological Survey of India, Nagpur
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