Improved paths and tracks: Part 1
Practical Action
Surfacing
Most paths and tracks have not been
'constructed' but have developed naturally from
0.2m 0.2m 0.1m
5% 5%
the passage of traffic. The compaction of the soil
by pedestrians, animals, or light vehicles is
Camber
usually sufficient to give a satisfactory surface.
The addition or replacement of surfacing material
●flat or undulating ground or ridge crests and direct ascents of slopes
●particularly useful in wet or marshy areas
is relatively expensive and can only be justified in
5%
special circumstances. Examples of such circum-
stances are marshy areas, very rough terrain, very
sandy soils, or easily erodible soils on steep
slopes. For these sections selected material is
brought to the site and is used to construct the
Crossflow (outsloping)
●side-sloping ground
●permeable soils
●moderate/low surface run-off
path in one or more layers. Ideally suitable
material should be obtained from pits excavated
5%
close to the section under construction. Where
the major problem is an erodible surface, a single
Crossflow (insloping)
layer of well-compacted gravelly soil may be
adequate. If the naturally occurring soil is very
weak, such as loose sand, construction using
●side-sloping ground ●high surface run-off
●impermeable soils ●steep slopes
several layers will be necessary. This spreads the
load of the traffic through the layers and reduces
the pressure on the underlying soil. A certain
amount of clay mixed in with the gravel helps to
Figure 3: Typical cross-sections for
improved paths and tracks
bind the material together and produce a dense
impermeable surface layer. Figure 4 illustrates
some surfacing methods for paths and tracks. (In
very marshy areas special techniques, which will
be described in a later technical brief, are required.)
Construction sequence
Where a section of path or track is to be reconstructed or improved, the construction
sequence shown in Figure 5 should be followed.
Thin blinding layer of fine
material with some clay for
binding
One or two layers of coarse
gravely material to provide
strength
Fine surfacing
materials
Smaller stones packed and
hammered in
Large stones laid on edge
(approx half depth)
●well-used paths ●poorly-drained, thin, or fragile soils
(a) Typical construction
100 – 200mm
●string construction ●good for heavy traffic and weak soils
soils (b) ‘Telford’ construction
Stones (approx. 100mm x 150mm
Larger edging stone
Large boulders
on the outside
Small boulders
on the inside
75mm sand
●string construction
●rough terrain
●steep gradient
●can be rough to walk on
(c) Stone pitching
Rubble
●rough terrain
●rocky or bouldery areas
(d) Boulder pavement
Figure 4: Surfacing methods for paths and tracks
4