KalpanaOne Hull Morphology

I was reviewing the April 2007 KalpanaOne Orbital Space Settlement
Revised .pdf (Al Globus, et al)and noted that the recommended hull
radiation protection for a LEO settlement (within the Van Allen Belt)
is 10 tons/square meter. This estimate is based on the 10 tons/square
meter of earth atmosphere that we earth bound humans have enjoyed
throughout our evolution. The radiation protection of the settlement
would presumably be provided by lunar regolith.
My question is this: If the cylindrical hull of KalpanaOne were
composed of a series of stacked inflatable water ice filled "donuts" -
probably consisting of several interlocking nested rings of sufficient
depth - covered by the hard cylindrical shell, would this
configuration reduce the mass of the radiation shielding required. I
ask this because I understand that water is one of the most effective
radiation shielding materials known.
I understand that obtaining the massive quantities of water for water
ice shielding would be prolematic. As a thought experiment, though,
I'm wondering if water ice radiation shielding might provide superior
structural strength, radiation shielding and micrometeorite shielding.
Does anyone know how much water ice would provide the equivalent
radiation shielding of 10 tons/square meter of atmosphere?
Chris