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THURSDAY, DECEMBER 14, 1998

DESIGNING DAMS

A SCIENTIFIC PROCESS *******

THE SENIOR RESIDENT ENGINEER OF THE HIGH ISLAND WATER SCHEME, MR. A.P. FRASER SAID TODAY (THURSDAY) THE DESIGN OF DAMS HAD, IN RECENT YEARS, BECOME A FAR MORE SCIENTIFIC PROCESS AND USED HIGH ISLAND AS THE LATEST AND MOST MODERN EXAMPLE.

SPEAKING AT THE Y'S MEN'S CLUB LUNCHEON MEETING, HE SAID THE EMPIRICAL APPROACH WAS VERY MUCH THE RULE IN DAM DES IGN UNTIL THE LAST FEW DECADES.

+USUALLY THE EMPIRICAL RULES WERE CORRECT BUT THE BAS IC BEHAVIOUR OF THE MATERIALS WAS NOT UNDERSTOOD AND THE FACTORS OF SAFETY OF THE DAMS COULD NOT BE CALCULATED, HE SAID.

+THIS COULD LEAD TO GROSSLY OVER-DESIGNED, UNECONOMIC DESIGNS OR EQUALLY POSSIBLY TO INTRINSICALLY UNSAFE STRUCTURES.

MR. FRASER POINTED OUT THAT RESEARCH IN SOIL AND ROCK MECHANICS HAD GIVEN THE DESIGNER MORE INSIGHT INTO THE PROPERTIES AND BEHAVIOUR OF EARTH AND ROCKF ILL.

+EQUIPMENT IS NOW AVAILABLE TO TEST THE STRENGTH OF VARIOUS FILLS. THE USE OF COMPUTERS HAS REDUCED THE DRUDGERY OF THE SOLUTION OF STABILITY ANALYSES FOR DAMS, HE SAID.

+MATHEMATICAL MODELS OF DAMS CAN BE CREATED, USING FINITE ELEMENT ANALYSES AND THE STRESS AND THE STRAIN AT ANY POINT IN A DAM CAN BE CALCULATED.

+THE ENTIRE CONSTRUCTION AND IMPOUNDING SEQUENCE CAN BE

SIMULATED BY THESE MATHEMATICAL MODELS.+

HOWEVER, MR. FRASER SAID, THESE METHODS WERE MERELY SOPHISTICATED TOOLS AND THE IR VALUE WAS ONLY AS GOOD AS THE BASIC DATA FED INTO THEM.

REFERRING TO THE DAMS AT THE HIGH ISLAND WATER SCHEME, HE SAID THEY EMPLOYED NEW TECHNIQUES IN THE USE OF THE IR ASPHALTIC CONCRETE CORES.

THE USE OF ASPHALTIC CONCRETE CORES, HE ADDED. WAS DETERMINED BY THE LACK OF SUITABLE IMPERMEABLE MATERIAL FOR A CONVENTIONAL CLAY CORE IN THE NEIGHBOURING AREA.

MR. FRASER ALSO SPOKE ABOUT THE DIFFERENT TYPES OF DAMS AND HOW TO CHOOSE THE RIGHT TYPE.

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