Report
on a Geological Overview of Ramban to Banihal Highway Project, Jammu and Kashmir
1.
Introduction:
Ramban
to Banihal highway project is a most difficult part of NH-1A (NH-44) due to
very rough topography with a steepest terrain on Jammu to Srinagar highway,
this is vital for providing connectivity between Ramban to Banihal. The
Geological condition is very complex in this section due to past tectonic
activity. The total length of the project is 36 km from Km 151+000 and ended at
Km 187+000, including 06 major bridges, 21 minor bridges and 6 Tunnels.
2.
Geology of the Project area:
During
the field work it has been observed, from Ramban to Banihal metamorphic rocks
are exposed along the project highway. These exposed rocks have undergone
moderate to high temperature and pressure condition due to Murree
thrust, Makarkote thrust and Panjal thrust. At some places, intrusion of granitic
rock have been observed near Panthal and khuninallah area. Two local thrusts have
been encountered named as Digdole and Magarkote thrust, at Digdole and north of
Ramsu respectively. From Ramban to Banihal, there are numerous Shear zone/seams
are present which generate rockfalls and slides along the highway on steep hill
slopes in the project area. The area from where project highway starts
km.151+000
 |
| Stratigraphic sequence of the project area (Bhat, et al.,1999) |
The rocks of Salkhala group are exposed along the
highway, comprises foliated slate, phyllite, quartzitic phyllite dolomite form
151+00 to up to km. 169+00. Salkhala group is divided to salkhala formation,
Ramban formation, sinchua formation and Baila-Gamir formation. Ramban formation
comprises slate, phyllite, dolomite and quartzite, highly jointed and sheared
at some places (At T1 and T2 tunnel) due to effect of Panjal thrust as well as Muree
thrust. Muree thrust separates murree group of rocks to metamorphic rock near
Ramban which is parallel to the Chenab river.
Ramban formation is tectonically overlain by salkhala formation near Digdole. The
Granitic rocks are exposed near Khuni nallah next to Digdole ut to Magarkote. Further
next to Magarkote km.169+000, the rocks of Ramsu formation are exposed along
the highway comprise a highly compressed unit of phyllite and phyllitic slates,
quartzite. Ramsu formation is separated tectonically from salkhala formation by
Makarkote thrust at km. 170+000. It is
recorded unfossiliferous till date. The rocks of Ramsu formation are exposed between Makarkote to Sherbibi
along the project highway. Ramsu formation has micro folds due to thrusting activity
over salkhala formation. Further from Km. 181+000 to up to end of the project
187+000, the rocks of Chamalwas formation are exposed which comprises greenish
grey slate, quartzite, metasandstone and metasiltstone which is uncomfortably overlain
by syringotheris limestone. The Chamalwas formation is also unfossiliferous
like Ramsu formation.
 |
| Lothological Strip Chart along Highway |
1.
Structures, Bridge, Retaining walls foundation and Tunnels:
As
we have know this area falls under the youngest mountain chain of the world and
most difficult zone of Jammu to Srinagar highway due to its geomorphology and
geological complexity. The lithology of the project area is metamorphic
sequence which is fresh to highly weathered in nature shows intense shearing,
fracturing and folding at at some locations (Ramban, Digdol and Ramsu,
Nachilana area).
There is need to design and execute the foundation work of structure carefully. During execution of shallow open cast foundation of bridges, geological logging of the foundation area needs to be carried out properly and if found any shear zone/seams should be treated by dental treatment as per the standard (IS:11973, 12070). At some places the nature of rock strata is noticed as poor to very poor rock (Class C, highly jointed, weathered with open joint). Such foundation location should be noticed carefully and foundation improvement to be carried out before laying the PCC by fully grouted anchoring or cyclic grouting method, if required as per IRC or IS standard (from Seri to Battery Chasma MNB at km.153+900,156+070 and 157+970, MJB 161+300).
 |
| Mom Passi, Highly Steep Terrain with Complex Geology |
There is need to design and execute the foundation work of structure carefully. During execution of shallow open cast foundation of bridges, geological logging of the foundation area needs to be carried out properly and if found any shear zone/seams should be treated by dental treatment as per the standard (IS:11973, 12070). At some places the nature of rock strata is noticed as poor to very poor rock (Class C, highly jointed, weathered with open joint). Such foundation location should be noticed carefully and foundation improvement to be carried out before laying the PCC by fully grouted anchoring or cyclic grouting method, if required as per IRC or IS standard (from Seri to Battery Chasma MNB at km.153+900,156+070 and 157+970, MJB 161+300).
The
foundation which will be cast over a steep slope, the edge distance, frustum of
bearing etc. should be checked as per IS 1904,13063 and IRC 78-2000. Excavation
for open foundations should be done after taking necessary safety measures for
which guidance may be taken from IS: 3764.The foundation protection work related
to structures on a steep hill slope noticed carefully at the time of design and
execution and kinematic analysis and further modeling needs to be carried out
to check the stability of foundation as per the site condition and codal
provision. The area from Maroge to Makarkote is the steepest area of the
project so special attention needs to be required in this area (Bridge at
153+900,160+300 and 169+060).
At Tunnel 1, 2 and 6 the rock mass is noted
as highly jointed and moderate to high weathered slate/phyllite/schist rock
including Dolomite. Which belongs near to class C as per the rock mass
classification, so proper attention is to be required to design the portal face
and tunnel support system based on assumed and field parameters.
The rock strata at Tunnel 3, 4 and 5 is better with compare to tunnel l, 2 and 6 known as granite/ granitic gneiss (eccept few meter sheared zone at panthal). The Rock strata of this stretch belongs to class A-B of the rock mass classification, moderately jointed and fresh in nature except Panthal bridge location where poor quality of rock mass is observed up to few meters along the tunnel axis both side from center of nallah. At this location weathering and shearing effect have been observed on right bank of panthal nallah up to few meters inside the hill slope. During excavation of tunnel a detail geological mapping including 3-D face logging should be carried out after every cycle of excavation on a scale 1:100 or 200 and if found any deviation in designed data to be communicated to designer to improve the support system and value engineering. The over breaking should be noticed carefully and blast design updated accordingly. Blast design is exercised properly in each type of rock mass for tunneling work as well as for cut slope excavation works.
 |
| Highly Jointed and Sheared Granitic Schist at Panthal Tunnel Portal |
The rock strata at Tunnel 3, 4 and 5 is better with compare to tunnel l, 2 and 6 known as granite/ granitic gneiss (eccept few meter sheared zone at panthal). The Rock strata of this stretch belongs to class A-B of the rock mass classification, moderately jointed and fresh in nature except Panthal bridge location where poor quality of rock mass is observed up to few meters along the tunnel axis both side from center of nallah. At this location weathering and shearing effect have been observed on right bank of panthal nallah up to few meters inside the hill slope. During excavation of tunnel a detail geological mapping including 3-D face logging should be carried out after every cycle of excavation on a scale 1:100 or 200 and if found any deviation in designed data to be communicated to designer to improve the support system and value engineering. The over breaking should be noticed carefully and blast design updated accordingly. Blast design is exercised properly in each type of rock mass for tunneling work as well as for cut slope excavation works.
2.
Road Cut Slope Stability Or Slope Protection works:
As the terrain of the project
is through the mountainous region, various protection works, such as revetment
walls, rock net and special slide protection works to be required to stabilize
the slope. The slope protection works will be mainly soil slope, soil-rock
slope and rock catch type.
For a soil slope, soil nailing, revetment wall (180+000 to 184+000) or stone masonry walls can be used to protect the slope including bioengineering method such as hydro seeding to control surface erosion by quick vegetation development. For highly fractured rock mass, the revetment wall can be applied to protect the slope as per the site condition, if the height of the wall is more than 6 meters the strength parameters to be carried out for the wall foundation (Ramban formation, Ramsu formation and soil strata). Where the slope is stable but surface instability is occurred due to shooting stone with deferent size of rock pieces, rock net and rock catch fence to be installed as per site condition and contract agreement (Battery chasma to panthal nallah, khuni nallah and magarkot area). In the special protection works such as planer, wedge and toppling failure (Km.170+000 to 178+000 and Km.186+000 to 187+000 ), we can stitched the jointed rock mass by fully grouted rock anchoring, dowelling with or without shotcrete as per site condition but detail kinematic slope stability analysis (day lighting case) should be carried out to check the failure mechanism and FOS. Further we can confirm these results with continuum and discontinuum modeling in details if required. (Digdole,khuni nallah,panthal, Magarkot, Sherbibi and 186+000 location).
 |
| Highly Steep Cut Slop required correct Protection measures |
For a soil slope, soil nailing, revetment wall (180+000 to 184+000) or stone masonry walls can be used to protect the slope including bioengineering method such as hydro seeding to control surface erosion by quick vegetation development. For highly fractured rock mass, the revetment wall can be applied to protect the slope as per the site condition, if the height of the wall is more than 6 meters the strength parameters to be carried out for the wall foundation (Ramban formation, Ramsu formation and soil strata). Where the slope is stable but surface instability is occurred due to shooting stone with deferent size of rock pieces, rock net and rock catch fence to be installed as per site condition and contract agreement (Battery chasma to panthal nallah, khuni nallah and magarkot area). In the special protection works such as planer, wedge and toppling failure (Km.170+000 to 178+000 and Km.186+000 to 187+000 ), we can stitched the jointed rock mass by fully grouted rock anchoring, dowelling with or without shotcrete as per site condition but detail kinematic slope stability analysis (day lighting case) should be carried out to check the failure mechanism and FOS. Further we can confirm these results with continuum and discontinuum modeling in details if required. (Digdole,khuni nallah,panthal, Magarkot, Sherbibi and 186+000 location).
The
Slope geometry, rock type and shear strength parameters should be checked
properly in the field with design and drawing before executing the work of cut
slope and if found any deviation in rock type, class and cut slope angle,
protection measures must be updated accordingly. During the cut slope activity at km183+600 to
184+600 and 177+300 (SB), mass movement (creep movement) has been observed due
to excessive cut height, toe cutting of the slope, needs to be protected.
3.
Major Landslide at Highway:
Several
landslides have been encountered at Ramban to Banihal project highway, named
and chanaige as follows:
·
Seri Landslide Km.151+300
·
Landslide at Khuni nallah Km.162+800
·
LandSlide at Panthal
Bridge Km.
168+600
·
Ramsu landslide Km. 172+600
·
Landslide at Ratanbas Km.
176+100
Landslides
are natural phenomena and occurred due to natural forces as well as manmade
activity like improper excaation. As we know this area exists in zone IV on
earthquake zonation map of India. The topography of this area is very roughed
and geologically very complex in nature. When the degree of weathering
(physical, chemical and biochemical) is increased and strength parameter of
rock mass is decreased as the time passes away. When the shear strength parameters
of the rock mass are reached at peak value due to natural or manmade forces,
slope fails in continuum or discontinuum materials. Most of landslides of the
project area are governed by discontinuities except Seri landslide. The
material at Seri Slide is highly crushed and seems to continuum in nature. A
brief description of major slides along the alignment and location view is being presented below:
·
Seri Landslide: landslide
is encountered at Km 151.050 and occurred in sheared and highly crushed rock
mass (slate and phyllite) which is continuum in nature.The rock mass
fails during monsoon seasons due to decrease in shear strength parameters of
rock mass while pore water pressure increased (saturated condition).
Deep seated failure has not been observed but it is a large slide. For the protection measure we can used gabion wall or reinforced wire mess grid at this location with bioengineering method such as seeding root mat or hydro seeding as per the site condition. Location of all current slide https://www.google.com/maps/d/edit?hl=en&mid=1kG4dcr-_JQQmJybqIu45ttv3rmrH942Z
https://www.google.com/maps/d/edit?mid=1kG4dcr-_JQQmJybqIu45ttv3rmrH942Z&usp=sharing
 |
| Seri Landslide |
https://www.google.com/maps/d/edit?mid=1kG4dcr-_JQQmJybqIu45ttv3rmrH942Z&usp=sharing
·
Khuni nallah Landslide: Khuni nallah landslide is located at Km 166+200 just
before the bridge. This landslide is governed by discontinuity. It is occurred
due to road widening/toe cutting with a combination of planar, wedge failure
within the rock mass.
 |
| Landslide near Khuni Nallah |
The rock type
of this area noted as phylitic, granite dipping towards the highway (daylight
at some location). For control measures of this landslide we can use rock catch
fence with rock net. As we have observed, this landslide produces different
size of rock boulders so that the rock catch fence to be design after knowing
the trajectory path and kinetic energy of the detached boulders.
·
Panthal Nallah Landslide:
This landslide
is located just after the Panthal bridge
at km 168+700. The area is noted as moderately jointed granitic gneiss with steep
slope. The nature of this slide is governed by kinematic mechanism and required
slope
 |
| Landslide at Panthal Nallah |
protection as trimming of
the slope, rock netting with rock bolting. The stone masonry wall, revetment
wall can be used at the bottom of the slope. Before finalizing the rock net kinematic
analysis should be carried out to know the mode of failure and protection works
to be decided and executed accordingly.
·
Ramsu Landslide: This landslide is located at km
172+600. It is most prominent landslide in the project area and occurred due to
widening of existing road and complex mechanism of failure due to Magarkote
thrust. The rock type of this area is noted as highly compress sequence of Phyllite,
carbonaceous slate, dolomitic and siliceous limestone including quartzite of
Ramsu formation.
 |
| Ramsoo Landslide |
This area is highly sheared, fractured and folding to
Makarkote thrust. For the control measure of this landslide we can use
reinforced gabion wire mesh grid at the bottom of the slope. Loose rock
pieces/rock boulders must be removed by trimming and rock net to be used with
geo-mat from top of the slope (crown) up to the gabion wall top. The rock
bolting can be used to improve the shear parameters of the rock mass but before
finalizing special protection a detail kinematic analysis of the slope, slope 2-D
face logging, and subsurface parameter of rock mass needs to be carried out.
·
Landslide at Ratanbas: This landslide is located at Km. 181+400
near Ratanbas area. It is occurred due to planar and wedge failure in
carbonaceous slate and phyllite. Rock mass is moderately weathered.
 |
| Landslide at Ratanbas area |
Slope failure is occurred along closely spaced
and steeply dipping
joints as a planar and wedge mechanism due to the intersection of
adversely-oriented joint planes. For control measure of this landslide first we
can need to redesign the slope face geometry and remove all loose materials from rock slope then
we can use rock bolting with rock net and shotcreting. A detail analysis should
be carried out before finalizing special protection measures as 2-D slope face
logging, subsurface parameter of rock mass.
1.
Conclusion:
As we have noted that the topography
of this section is extremely rugged including steep hill slope. The area is
witnessed two major thrusts known as Digdole and Makarkote which is
tectonically active till date. It is also noticed mostly length of the project
covered by slate, phyllite and schistose rock mass wherever these rocks are
highly weathered and jointed at places may leads to problems in both cases,
slope protection as well as structures foundation stability. Special attention
is to be required during execution of cut slope excavation, tunnel portal face
as well as foundation excavation. At Seri,Ramsoo and Ratanbas landslide locations, we can also go for square
half tunnel with inclined roof top but the applicability of this type of
structure is a matter of technical and financial discussion. These types of
structures are successfully adopted in the country for highway protection from
unexpected fall, avalanche landslide on highway. At the location of Maroge, Digdole
and Makarkote bridge, foundation will be on a steep slope, an excessive excavation
will be required to layout the foundation on steep slope, is not good for
foundation stability. So we can go for pile foundation in rock on steep slope,
if required. The tunnel 3,4 and 5 will be executed as rock type seems fair to
good but special attention will be required for execution of Tunnel 1,2 and
6.
