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In Search of Technological Alternatives for Construction in Leh
compressed
earth blocks a viable option
Zeenat Niazi
Mission
Leh: Centuries ago, this was an important stop on the old caravan
silk route from China. Today, this isolated town is described in
tourist guide books as “merely a military base and a tourist centre”
with fascinating vistas and exotic experiences in the back-lanes of
the town. A description that presents an extremely limited view of
a region with fascinating history, culture and ecology. I am
grateful to Dr. Siddhartha of the Defence Research Development
Organisation (DRDO) whose bulldozing had made this trip possible for
me.
I was in Leh for a specific purpose - to demonstrate the TARA
Balram at the Kisan-Jawan Mela organised by the Field Research
Laboratory (FRL) of the DRDO. The FRL was established in 1960 with
an aim to find solutions (wage a war with nature - as they short-sightedly
refer to their mission) to make the hostile climate of Ladakh
reasonably green and productive for sustaining the sparse local
population and the defence forces deployed here (especially the
latter). Efforts of FRL are showing results at least in the
immediate surroundings of their campuses which are reasonably green
as are areas around Leh town. Every year, the FRL organises a two
day Kisan Jawan mela (echoing Nehru’s call of Jai Jawan jai Kisan)
with the aim to share their scientific achievements with the local
Ladakhis.
I was here to demonstrate production of Compressed Earth
Blocks at the Mela to gauge public response, but more than that my
mission was to assess the future potential of this technology for
Leh and Ladakh.
But before we go ahead, what is this region and why are we
looking for technological alternatives for building here?
Characteristic Features
Leh
along with Kargil forms the region of Ladakh in
East Kashmir. Ladakh, a high altitude plateau is a cold
desert lying in the Western Himalayan mountains very often called
“moonland” due to its peculiar terrain. The
Himalayas shadow Ladakh and form a very effective barrier to rain.
Few clouds creep across their awesome heights and as a result Ladakh
is barren without relief. The rivers from melting glaciers,
especially the many tributaries of the river Indus carry water and
support some vegetation. Along the banks of these water bodies and
in protected crevices of the mountains some splashes of green -
mainly pastures, agricultural fields and alpine vegetation are
visible that sustain the sparse habitation.
The climate is characterised by almost a total lack of
rainfall, intense solar radiation let in through clear skies and
rarefied air and large diurnal and annual variations in
temperature. A severe cold-dry season from November to April,
during which time Ladakh is mainly isolated from the rest of the
country with the mountain passes and roads blocked with snow, opens
to a mild warm-dry summer from May to October. The average annual
precipitation is about 25 mm, most of it in the form of snow from
December to March.
Lifestyles and life support systems, over the centuries have
evolved to sustain and contain the human and animal population
dependent upon limited arable land and biomass resources.
Agricultural and pastoral practices, even the concepts of polyandry
and monasticism encouraged in every family to limit the population,
lead to this end. It is only since the opening up of Ladakh by
building roads and the setting up of military bases here, that
technologies and consumer goods from “down below” (as the rest of
the country is described) have entered here.
Building Practices
The
response to the characteristic climate and isolation from the rest
of the country is especially evident in the building technology and
construction practices in Ladakh. The construction practices have
evolved in close harmony with the material resource base climate and
lifestyle of the people. Earth and stone are the common building
materials. Both walls and roofs are built in earth. In Leh town,
all the older houses and most of the new construction uses hand
moulded adobe in walls and rammed earth on timber understructure for
the flat roofs.
The present suitability of traditional earth construction
practices is being questioned, especially now that an increase in
the rainfall is observed. It is felt that this changed condition
is leading to leakages in the earthen roofs and accidents, even
partial collapse of some buildings.
Many locals point to the increase in vegetation in the
region, brought about through the efforts of FRL, as a probable
cause for the increase in rainfall. FRL, is on their part looking
for technology alternatives for construction that can cope with the
changing climate. Their search, as that of the local Hill
Council’s, has led to the choice of Compressed Earth Blocks (CEB)
as an option.
Critical interventions
The
critical issue in the new problems arising due to increased
precipitation is the leakages in roofs. Discussions with the hill
council engineers and professionals of the Ladakh Ecological
Development Group ( a local NGO) revealed that the problems lie
mainly in the weak understructure and the fact that roofs are built
with no slope to drain out the water. Even a small amount of
rainfall causes ponding on the roofs, the understructure made of
poplar branches and twigs cannot support the weight of the resultant
wet and heavy earthen mass and gives way leading to collapse. There
is also a scarcity of good quality timber, most of it reaching here
by road from Srinagar or Manali.
Solutions being tried out range from providing a minimal
slope to drain out the water, plastering the surface with clay rich
(gompa ) soil that forms an impervious layer and providing a
Corrugated Galvanized Iron sloping cover to the existing roof. The
last option, most common in the military establishments is also the
most expensive and unsustainable besides unsuited to the lifestyle
and urbanscape. All the CGI sheets come from “down below” at very
high transportation costs - largely unaffordable by the locals.
Prakash et al ( Solar Architecture and Earth Construction in
North Western Himalayas) have suggested the use of jack arches
using Compressed Earth Blocks to make roofs that will provide the
required thermal insulation , water tightedness and a flat surface.
The traditional adobe masonry walls in Leh are quite adequate
from the point of view of strength to hold up the heavy roofs. This
is evident in the centuries old construction in Leh. However, the
earthen walls do not offer any resistance to moisture and in the
case of rains (which we now know is fairly regular) these tend to
erode making the structure weak and unable to support the roof
loads.
Although the issue of water tight roofs is more urgent, that
of water resistant walls cannot be ignored. The potential of
utilisation of CEB for both walls and roofs makes this alternative
more attractive here.
The Technology of Compressed Earth Blocks in the context of Leh (Ladakh)
In engineering terms, earthen masonry units, as practising
earth technologists will agree, must satisfy two main criteria
before they can be accepted for use in construction:
1. Adequate Compressive strength (especially wet strength)
and
2. Resistance to erosion.
The compressive strength is governed to large extent by soil
quality: coarse grains of the soil providing strength and acting as
a skeleton and clay particles binding the whole together to form the
masonry unit. This is traditionally known and uncomplicated adobe
construction of Leh utilises this quality of soil.
Such bricks are perfectly safe to be used for masonry in
regions where they do not come in contact with water. Earth bricks,
however, indicate a loss in strength when wet. Clay particles tend
to lose the binding ability in wet condition leading to
disintegration of the block. This action is enhanced if the block
is porous, as when uncomplicated (adobe), and allows rapid water
absorption. Strength we know can be enhanced considerably by
compacting the soil and increasing the block density. This results
in reducing the porosity and therefore the rate of water absorption,
thus slowing down the process of block disintegration. In addition,
if a stabiliser is added to the soil such as cement or lime, this
will stabilise the block and the loss in strength due to saturation
will not be drastic.
Erosion, the second criteria, is a surface characteristic. A
rough hand moulded block is more liable to be affected by the
vagaries of wind and rain (especially rain) than a smooth machine
moulded one. Surface erosion soon leads to loss in strength as the
walls get exposed to water penetration. Surface treatments like
plasters and paints provide adequate protection. Stabilisation
within the block is also useful and the wall can be left exposed
without plasters.
Let us now put this knowledge in the context of Leh. The
soil in Leh town is sandy with a high coarse grain fraction and
negligible clay. It not only has poor binding properties but is
also very difficult to compress. It is necessary to mix it with a
finer soil. The locals know this well and have traditionally used
the Gompa earth (probably from the Spituk monastery area) and the
Shy soil from Shey village, which are mainly fine silty-sands with
some clay fraction, to make their adobe. The two soils mixed with
local Leh soil can now be moulded in a soil press to give strong and
well moulded Compressed Earth Blocks. During my visit, we mixed
Shey soil with the local Leh soil in a proportion of 3:1 and
compacted the mix in the TARA Balram soil block press. The blocks
were very well formed with high green strength.
To get around the problem of achieving adequate wet strength
and erosion resistance, compaction of soil substantiated with
stabilisation appears to be an optimum solution. Although, one
could only go in for simply stabilised adobe without compaction, in
order to achieve adequate “wet strengths” one would have to use very
high quantities of the stabiliser especially as the block is
uncomplicated and porous. The former option optimises stabiliser
use and is thus better suited for Leh ( manpower for compaction
being more easily available than cement which comes from Chandigarh,
Srinagar or Manali at an exorbitant cost of Rs. 350 per bag).
Networking for appropriate and speedy interventions
I realised that these conclusions have been
similarly reached by engineers of the newly elected Hill Council as
well as by the Military Engineering Services and the Ladakh
Ecological Development Group . They are all experimenting in small
ways to reach to the correct soil - stabiliser mix, appropriate soil
stabilization and processes for compaction. Even as I write, I am
informed that a private builder has obtained hydraulic equipment to
manufacture Compressed Earth Blocks for private construction in Leh
town.
Ladakh, especially the town of Leh is undergoing rapid change, both
demographically and technologically as roads and eyes open to
developments “down below”. It is clear, however, that earth will
continue to be used for construction in this region at a large
scale. Compressed Stabilised Earth Blocks have the potential of a
viable option in the future basket of building material choices for
Ladakh. Current interventions to introduce CEB to the region are at
best sporadic and unsupported by technical know-how. These need to
be co-ordinated, technically supported and linked to the
practitioners. The co-ordinated efforts of the concerned
organisations can accelerate the appropriation of this technology by
the local population leading to appropriate change in construction
practises and improved building systems.
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