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MONDAY, MAY 9, 1983
EFFORTS TO IMPROVE SLOPE STABILITY CONTINUE
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THE GOVERNMENT IS NOT COMPLACENT ABOUT THE OVERALL SITUATION WITH REGARD TO SLOPE STABILITY, EVEN THOUGH HONG KONG STOOD UP THE WETTEST YEAR VERY WELL TO THE HEAVY DOWNPOURS LAST YEAR SINCE RECORDS BEGAN IN 1884, THE PRINCIPAL GOVERNMENT GEOTECHNICAL ENGINEER, DR EDWARD BRAND, SAID TODAY.
HE SAID THAT EFFORTS WOULD CONTINUE TO BE PUT INTO MEASURES TO IMPROVE AND CONTROL GEOTECHNICAL ENGINEERING PRACTICE.
SPEAKING AT THE LUNCHEON OF THE ROTARY CLUB OF EAST TSIM SHA TSUI, DR BRAND SAID SINCE 1977, WHEN THE GEOTECHNICAL CONTROL OFFICE WAS SET UP, MORE THAN $470 MILLION HAD BEEN SPENT ON THE LANDSLIP PREVENTIVE MEASURES PROGRAMME.
+AND EXPENDITURE IS CONTINUING AT THE RATE OF ABOUT $50 MILLION PER YEAR, HE SAID.
AT A +ADDITIONALLY, A GREAT DEAL OF STABILISATION WORK, COST OF SEVERAL HUNDRED MILLION DOLLARS A YEAR, IS CARRIED OUT IN BOTH THE PUBLIC AND PRIVATE SECTORS IN ASSOCIATION WITH CAPITAL PROJECTS.
DR BRAND SAID THAT ONE QUESTION QUITE OFTEN ASKED BY THE PUBLIC WAS +HOW SAFE ARE HONG KONG'S SLOPES?+, BUT, THIS QUESTION WAS NOT EASY TO ANSWER IN ABSOLUTE TERMS, HE SAID.
+AS WITH ALL CIVIL ENGINEERING STRUCTURES, SLOPES ARE DESIGNED ON THE BASIS OF FACTORS OF SAFETY, WHICH IS BASICALLY THE RATIO OF THE DESIGN STRENGTH OF A STRUCTURE TO THE MINIMUM STRENGTH REQUIRED FOR IT TO BE STABLE, DR BRAND SAID.
+OBVIOUSLY, THE DESIGN STRENGTH MUST BE HIGHER THAN THE MINIMUM VALUE REQUIRED FOR STABILITY, OTHERWISE THE STRUCTURE WOULD FALL DOWN. +
IN ASSESSING THE STABILITY OF A SLOPE, OR IN DESIGNING A NEW ONE, A GEOTECHNICAL ENGINEER MUST TAKE ACCOUNT OF A NUMBER OF FACTORS. HE MUST STUDY THE GEOLOGY AND GEOMETRY OF THE SLOPE AND OF THE SURROUNDING AREA HE MUST BE ABLE TO MEASURE ACCURATELY THE STRENGTH CHARACTERISTICS OF A LARGE MASS OF SOIL AND ROCK: AND HE MUST BE ABLE TO PREDICT THE WATER PRESSURES THAT WILL DEVELOP IN THE SLOPE DURING A HEAVY RAINSTORM.
+THE MEASUREMENT OF THE STRENGTH CHARACTERISTICS IS DIFFICULT ENOUGH, BUT THE PREDICTION OF WATER PRESSURES IS THE MOST PROBLEMATICAL ASPECT OF ALL IN THE SLOPE DESIGN. IT IS THEREFORE ALSO CRITICAL TO SLOPE SAFETY, DR BRAND SAID.
+SLOPES ARE DESIGNED TO A GIVEN STANDARD OF SAFETY ENGENDERED IN THE FACTOR OF SAFETY USED BY THE DESIGNER. THERE WILL ALWAYS BE SOME PROBABILITY OF FAILURE, EVEN IF THIS IS EXTREMELY SMALL. THE PROBABILITY OF FAILURE WILL OBVIOUSLY BE REDUCED AS THE DESIGN FACTOR OF AFETY IS INCREASED.+
/DR BRAND