XN000022-1983-04-17 — Page 4

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SUNDAY, APRIL 17, 1983

GEOTECHNICAL ENGINEERING IS MORE DIFFICULT THAN MANY OTHER ENGINEERING BRANCHES IN THAT IT DEALS WITH NATURAL MATERIALS WHICH, UNLIKE MAN-MADE MATERIALS, HAVE UNKNOWN VARIABLE CHARACTERISTICS, HE SAID.

AS AN EXAMPLE, DR BRAND CITED HONG KONG'S ROCKS WHICH HAVE BEEN +DEEPLY WEATHERED+ TO FORM WHAT IS CALLED RESIDUAL SOIL WHICH IS HETEROGENEOUS AND PERMEABLE TO WATER.

+BECAUSE IT CONSISTS OF EVERYTHING FROM CLAY TO BOULDERS OF ALL SHAPES AND SIZES, ANY TESTING METHOD ADOPTED CAN ONLY APPLY TO THE PARTICULAR PIECE OF MATERIAL UNDER STUDY,+ HE EXPLAINED.

THEN THERE IS COLLUVIUM TO DEAL WITH DEBRIS WHICH HAS ROLLED DOWNHILL FROM ROCKS AS PART OF A GEOLOGICAL PROCESS THAT IS HAPPENING ALL THE TIME, DR BRAND POINTED OUT.

THESE LAYERS OF COLLUVIUM, BY THEIR VERY NATURE, ARE USUALLY ONLY JUST IN EQUILIBRIUM.

+WHEN DEVELOPERS CUT INTO COLLUVIUM SLOPES, THEY DISTURB THE EQUILIBRIUM AND A HEAVY RAINSTORM COULD CAUSE THEM TO FALL DOWN UNLESS GOOD ENGINEERING DESIGN AND CONSTRUCTION HAS BEEN USED, HE SAID.

EXPLAINING HOW THE GCO HAS BEEN TACKLING THIS TRICKY PROBLEM, DR BRAND SAID, IT IS NECESSARY FIRST TO KNOW THE GEOMETRY OF THE SITUATION, TO ASSESS THE STRENGTH OF THE MATERIALS INVOLVED AND TO MEASURE OR PREDICT THE WATER PRESSURE IN THE SLOPE.+

COMPOUND ING THE PROBLEM IS THE MINUTE-BY-MINUTE CHANGE

OF THE WATER PRESSURE IN A HEAVY RAINSTORM.

+SOUND GEOTECHNICAL ENGINEERING EXPERIENCE AND JUDGEMENT ARE VITAL IN COMING UP WITH AN EFFECTIVE LANDSLIP PREVENTIVE PROGRAMME, HE SAID.

THE GCO PRESENTLY HAS 97 GEOTECHNICAL ENGINEERS, 10 OF THEM WITH PH D DEGREES. A TYPICAL ONE HAS A MASTER'S DEGREE IN SOIL MECHANICS, ROCK MECHANICS OR ENGINEERING GEOLOGY, WITH SEVEN YEARS' EXPERIENCE IN GEOTECHNICAL ENGINEERING AND FOUR YEARS IN GENERAL CIVIL ENGINEERING.

EXPERIENCED GEOTECHNICAL ENGINEERS ARE A RARE BREED WHICH EXPLAINS WHY THERE ARE 14 NATIONALITIES AMONG THOSE WORKING WITH THE GCO.

THE OFFICE IS CURRENTLY UNDERSTAFFED AND 22 MORE GEOTECHNICAL ENGINEERS HAVE BEEN OR ARE BEING RECRUITED FROM DIFFERENT COUNTRIES, DR BRAND DISCLOSED.

BESIDES GEOTECHNICAL ENGINEERS, THE OFFICE HAS 16 OTHER PROFESSIONAL STAFF, INCLUDING CHEMISTS, METALLURGISTS AND LAND SURVEYORS.

APAR FROM SLOPE STABILISATION WORK, THE GCO IS RESPONSIBLE FOR SUCH THER FUNCTIONS AS GEOLOGICAL MAPPING, MATERIALS TESTING, SITE INVESTIGATION, QUARRYING AND AERIAL PHOTOGRAPH INTERPRETATION.