HILL ROADS

1. Mr. DesaiA. P.
SGMRP, Mahagaon.

2. Alignment survey for hill roads
1. Reconnaissance survey:-
the general route for the alignment is selected
during the reconnaissance. First the topographical,
geological and meteorological maps of the area and
aerial photographs are studied. This may be
followed by aerial reconnaissance where it is
necessary and feasible.
subsequently the ground reconnaissance and
detailed study of difficult stretches are carried out.

3. 2. Trace cut
Trace cut is a narrow cut, 0.6 to 1.0 m wide,
prepared along the alignment of the road to enable
access for inspection during location of the route.
the route selected during the reconnaissance
is transferred on the ground during the trace cut so
as to provide an access for sub sequent detailed
survey.
1m to 1.2m wide track is constructed with
easier gradient than the specified gradient.

4. 3.Detailed survey
During the detailed survey, bench mark
are fixed and the longitudinal and cross
sections are obtained. A strip covering about
15m on either side of straights and 30 m at
sharp curve may be studied. The centerline is
marked by stacks and reference pillars.
Hydrological and soil investigation are carried
out for the route.

5. Geometrics of hill roads
The geometric standards for gradient,
superelevation and radius of curve etc. on
hill roads are different from those in plains.
The main reason for the difference are the
topography and other problems in alignment
of hill roads.

6. Width Of Pavement, Roadway Width
Highway
classification
Pavement
width in M
Road way width
in M (Excluding
side drain &
parapet)
NH & SH
Two lane 7 8.80
Single lane 3.75 6.25
MDR 3.75 4.75
ODR 3.75 4.75
VR 3.00 4.00

7. Camber
Type of surface Camber %
Subgrade, earth road
and shoulders
3.0 to 4.6
Gravel and WBM
surface
2.5 to 3.6 %
Bituminous
surfacing
2.5 %
Cement concrete 2.0%

8. Sight distance
S.S.D.= 0.278Vt + 𝑉2
254
𝑓
O.S.D.=0.556𝑣𝑏+2s+0.278T𝑣𝑏+0.278vT
Speed
Kmph
20 25 30 40 50
OSD m 20 30 35 50 70
Speed
kmph
30 40 50
OSD m 90 145 210

9. Super Elevation
e= 𝑣2
225
𝑅
Gradients: the ruling and limiting gradients
in mountainous terrain and in steep terrain
over 3000 m. height above mean sea level are
5% and 6% respectively.
upto 3000 m height above MSL are 6%
and 7 % respectively.

10. Types Of Curve
1. Hair pin curve
2. Salient curve
3. Re-entrant curve
4.Hair pin curve- these are the curve in hill
roads, which change direction through an angle of
180° or so, down the hill on the same side is
known as hair pin curve.
5.Salient curve- the curve having their convexity
on the outer edges of a hill road are called salient
curve.

11. 3. Re- entrant curve
The curve having their convexity on the
inner edge of the hill road are called re-
entrant curve.

12. Prevention and control of land slides
1. By providing proper and effective drainage
system to collect and divert seeping water.
2. By constructing breast wall and retaining wall.
3. By providing proper slopes and their treatment
to minimize the erosion.
4. By improving stability conditions of soil.
5. By stone pitching, cement grouting to the hill
slopes, which will minimize the erosion and
improve the stability.
6. Growth of vegetation.

13. 7. Relocation of road.
8. By reducing angle of slopes.
9. By wire-netting.

14. Drainage Structures
1.Surface Drainage- proper arrangement for
drainage of surface water is important to
prevent erosion and land slides.
a) Side drains- the drains are provided to carry
rain water from the surface of carriageway
and also from sloping side of hill.
1. Angle drain
2. Saucer drain
3. Kerb and channel drain

15. 2.Controlling seepage flow
For controlling seepage flow sub-surface
drains are provided at foot of the hill slope as shown
in fig.
3. Cross drainage-
an efficient cross drainage system is essential
for disposal of the surface water collected by catch
water drains and side drains across the hill road.