Background of Invention
Gravity Dams have large masses. Earthquake forces are proportion to mass. Their heaviness has added disadvantages of creating larger vertical loads on strata below dam which were hitherto unloaded.
Himalayas are weak mountains subjected to liability of very high earthquake. Hence gravity dams are highly unsuitable choice for Himalayan region.
In the choice of light-weight dams comes Arch Dams. They are lighter in weight hence are subjected to lesser earthquake forces. On the other hand they have much larger flexural strength than gravity dams to sustain the effect of vibration under higher earthquake. Very large dams in the world are made up of the shape of Arch.
But the strength of the arch depends on the strength of abutment to sustain high horizontal forces. Without huge horizontal forces supplied by mountain from the abutted portion of the arch the arch dam cannot gain strength at all. Himalayas are very weak mountain. They cannot supply horizontal forces at the springing of arch. Hence arch dams are unsuitable for Himalayan region.
This invention relates to using the third category of dams for Himalayan region namely the Shell Dams hither to unused. They have larger flexural strength than even arch dams. They do not depend on large horizontal forces from the abutment to be able to sustain strength, shape and function as arches do.
So from every point of view Shell Dams are the most suitable dams to be constructed on the rivers in the Himalayan region.
If it be a narrow deep gorge, one single semicircular hyperboloid shaped shell dam shall be designed and constructed.
If it be a wide gorge requiring low height large length dam, a series of semicircular hyperboloid shell and quarter frustum of egg shell alternatively placed side by side shall be designed and constructed.
If it be an intermediate gorge neither narrow nor wide, a combination of semicircular hyperboloid shells and frustum of egg shell shall be designed and constructed.
To assist the understanding of the invention, references will now be made to the accompanying drawing, which shows one example of the invention
FIG. 1 shows one example of a Shell Dam on a river flowing through narrow gorge of Himalayas,
FIG, 2 shows another example of shell dam on a river flowing through not a narrow gorge of Himalayas,
Detailed description of thepreferred embodiments
FIG.1 shows the upstream face of the shell darn (1) in a narrow gorge made up of a single hyperboloid (cut at semicircle) constructed in high quality concrete and pre-stressed along both sets of generators.
The waist of semicircular hyperboioid (2) forms the foundation of the dam embedded in the bed of river up to suitable depth.
The sides of the shell (3) abut on the rocks cut and treated wherever necessary to give strength sufficient to sustain and bear the resultants of horizontal water pressure acting on the shell.
The crown of the dam (4) is the large flared semicircle of hyperbotoid ptotruding in the upstream retaining the water.
FIG.2 shows the upstream face of the shell dam over a wide river between the mountains comprising of two hyperboloid shells (5) interrupted by an egg shell (6) as shown.
The waist (2) sides (3) and crown (4) of hyperboloid shells are same as described in FIG. 1,
The egg shells (6) are semicircular made of high quality concrete with hoop and meridian reinforcements having monolith interconnection (7) with the sides (3) of hyperboloid shells.
The foundation of the eggshell (8) are targe semicircles protruding upstream having anchor reinforcements against uplift embedded in the bed rocks of river.
Application Advantages and Examples
It is estimated that Himalayan Rivers have altogether one hundred thousand Megawatt capacity potential of hydro power. It is also estimated that about Rs.20 million per megawatt capacity is the cost of usual dams in Himalayas.
This invention reduces requirement of Concrete Volume from present to 7% of present volume. The cost is expected to come down from present cost to 10% of the present cost considering the extra cost of in additional reinforcements, pre-stressing strands etc.
Thus instead of spending Rs.2 trillion on dams in Himalayan region, using this invention will require only Rs.200 billion, a saving of Rs.1.8 trillion expenditure on dam, besides efficiency and less danger from earthquake.

I Claim
1. Shell Dams for Himalayan rivers comprises of shell dams made up
of one single shell structure or a combination of different types of
shell structure monolithically joint together.
2. Shell Dams for Himalayan rivers as claimed in Claim 1 wherein the
Shell Dam is made up of concrete and steel.
3. Shell Dams for Himalayan rivers as claimed in Claim 1 wherein the
Shell Dam is made up of concrete and pre-stressing strands.
4. Shell Dams for Himalayan rivers substantially as herein described
with reference to the accompanying drawing