44 CIVIL WORKS GUIDELINES FOR MICRO-HYDROPOWER IN NEPAL
Box 4.4 Soil cement canal in Andhi Khola, Nepal
In the Andhi Khola Irrigation Project (AKIP) designed by
BPC Hydroconsult, soil-cement was tested as an option for
irrigation canals. The soil-cement was prepared using a
mix of one part cement and one part sand to ten parts of
local red coloured clayey silt soil. The red colour of the soil
indicates a high iron content, which reacts with cement to
form a hard layer on the excavated surface of the canal.
Two applications of soil-cement were tested in 1990 and
1991. The first test used soil which was graded using a 4-
mm sieve, with larger lumps and soil broken up with a
tamper. After mixing the dry ingredients of cement, sand
and soil, water was added and mixed thoroughly until the
mortar reached the desired consistency for plastering. The
excavated surface of the canal which contained permeable
soil and gravel was first made moist by sprinkling water and
of the Andhi Khola soil cement canal can be seen in Photo-
graph 4.10.
To date, the performance of the soil-cement lining at Andhi
Khola has been good. The 1990 test section developed
some cracks after a week, apparently due to an excess of
water in the mix, which then caused cracking as the soil-
cement dried up and hardened. These cracks have not
worsened. The 1991 section has not shown any cracking.
The lining installed in the steep canal section has also been
performing well.
The advantage of this technique is that it is low cost. Be-
tween 20% and 40% of the cement required for a conven-
tional concrete mix is replaced by soil. The procedures are
easy to learn and are similar to those used for traditional
Photo 4.10 Soil cement lined canal section at Andhi Khola, Nepal.
then the mix was applied firmly to a thickness of 40 mm and
packed tightly to eliminate air pockets. The surface was
trowelled smooth and then cured for a week.
In 1991, a 15 mm sieve was used to grade the soil over a
test section of 140 m2. Later more demanding conditions
were used for a further test over a section of 25 m length, a
gradient of 1:20 and a velocity of approx. 1.3 m/s. A section
houses constructed in the Andhi Khola area. However, one
prerequisite for this type of canal is the need for high iron
content in the soil used to prepare the mix. Other soils will not
perform well. Another conclusion that has been drawn from
the Andhi Khola experience is that soil-cement canals are
not appropriate for turbulent flows. They are suitable where
seepage control is required and the gradient is gentle (veloc-
ity limited to ~1.0 m/s.)