Backfilling one side of my house's foundation with gravel...Any reason not too?

I just finished repairing 2 vertical hairline cracks that were leaking like a sieve everytime it rained. How can so much water pass through 2 small cracks?
I did some research on the Net and found out that at about 8 feet below grade, some clay soils that become completely saturated with water exert about 1700 pounds of pressure per square foot. Thats a hell of a lot of pressue. Why would thas builder backfill the foundation with clay? I'm assuming the engineer and architect are aware of this fact.
So what should I do to avoid the 2 cracks from ever leaking again? I'm thinking of putting gravel and sand in the hole instead of dirt. But I'm a little worried that this might create some kind instability on the opposite side of the house's foundation since there won't be an equalizing amount of pressure from the side that has the gravel. Could this create problems down the road?
The area to be filled is about 13 feet long, 3 feet wide and 7 feet deep.
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They sell special membranes for comcrete foundations one new type is ridged for drainage to keep water away from the foundation. Waterproof your foundation, also drain tile may be good for you, the plastic pipe with holes and a sock around it. Gravel should not be necessary then
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