SUPPORT OF UNSTABLE CLIFFS AT BARTON-ON-SEA

STABILIZATION OF UNSTABLE SLOPES SUBJECTED TO ACTIVE EROSION PRESENTS SPECIAL DIFFICULTIES. FIRST, ANY REMEDIAL WORK IS LIABLE ITSELF TO BE INITIALLY PUT AT RISK UNTIL SOME APPRECIABLE DEGREE OF BENEFIT HAS BEEN REALIZED. SECOND, THE REMEDIES MUST NOT ONLY PROVIDE SOME IMMEDIATE INCREASE IN SAFETY FACTORS BUT MUST ALSO TAKE ACCOUNT OF THE FACT THAT LONG-TERM STABILITY WILL BE ASSOCIATED WITH LOWER INHERENT STRENGTHS OF THE SOIL, AND HENCE FLATTER STABLE SLOPES, THAN THOSE EXHIBITED DURING THE ACTIVE EROSION. THE UNDERCLIFF ORIGINALLY CONSISTED OF A STRIP APPROXIMATELY 200 FT WIDE OF BROKEN GROUND BELOW A STEEP TOP CLIFF. THE BROKEN GROUND WHICH ROSE AT AN OVERALL SLOPE OF APPROXIMATELY 1 IN 3 GENERALLY CONSISTED OF CLAY BANKS AND FLAT TERRACES, WITH AN AREA TO THE REAR OF WATER-LOGGED GROUND. THE PROCESS OF EROSION HAS BEEN A TWOFOLD ONE: THE SEA, PARTICULARLY DURING STORMS AND HIGH TIDES, HAS WASHED THE TOE AWAY IN THE ABSENCE OF AN ADEQUATE NATURAL BEACH; WATER FROM SPRINGS AND FROM PRECIPITATION HAS CREATED MUD FLOWS WITH VERY FLAT SLOPES. IN THIS WAY THE INSTABILITY HAS BEEN TRANSMITTED INLAND TO THE CLIFF FACE FROM WHICH SLICES HAVE COLLAPSED AT INTERVALS. THE PRINCIPLES OF THE STABILIZATION SCHEME WERE AS FOLLOWS: (A) A PILED TRENCH WITH DEEP LONGITUDINAL CUT- OFF DRAIN INTO THE MIDDLE BARTON BEDS TO PREVENT SPRINGS BREAKING THE SURFACE; (B) COLLECTOR SYSTEMS FOR SURFACE WATER USING BERMS WITH ADEQUATE REVERSE FALLS AND OPEN DITCHES FOR MAXIMUM EFFECTIVENESS AND MINIMUM MAINTENANCE; AND (C) GRAVEL BLANKETING WITH A ROCK TOE WALL TO STABILIZE THE STEEPEST AND MOST DIFFICULT SECTIONS WHERE THE CLAY TENDS TO CONTINUE TO WEATHER FROM THE SURFACE. AN EXPERIMENTAL LENGTH OF DRAINAGE TRENCH OF 1000 FT IN LENGTH WAS CONSTRUCTED IN 1964 AND THE REVETMENT AT THE TOE IN 1966. THE STAGE 2 WORKS, CONSISTING OF 3300 FT OF DRAINAGE AND 4500 FT OF REVETMENT, FOLLOWED IN 1967-68 USING THE EXPERIMENTAL LENGTH AS AN ISLAND FROM WHICH THE WORKS EXTENDED. WELL POINTING WAS USED AS A TEMPORARY MEASURE DURING THE CONSTRUCTION OF THE DRAINAGE TRENCH. ADDITIONAL MINOR WORKS WERE CARRIED OUT IN 1969, 1970 AND 1971, INCLUDING REGRADING AND BLANKETING THE STEEPER SLOPES WHERE WEATHERING CAUSED SLOUGHING. SOME MOVEMENT HAS CONTINUED ON A SPECIALLY DIFFICULT SECTION OF THE UNDERCLIFF ALONG THE EXPERIMENTAL LENGTH WHERE OVERALL STABILITY WAS MARGINAL. THE GENERAL CONCEPT OF CLIFF STABILIZATION HAS HERE BEEN DEMONSTRATED AS SOUND WITH SPECIAL REGARD IN PREPARATION OF DESIGN TO THE CAPABILITY OF THE DRAINAGE AND COAST PROTECTION WORKS TO WITHSTAND FURTHER SMALL MOVEMENTS WITHOUT HAZARD TO THE OVERALL SCHEME; THE EXTENT OF MAINTENANCE MAY BE EXPECTED TO DECLINE AS VEGETATION, ALREADY ENCOURAGED OVER PART OF THE AREA BY HYDRAULIC SEEDING, TAKES FIRM ROOT THROUGHOUT. /AUTHOR/

  • Supplemental Notes:
    • Vol 66, No 782, P 969, 3 FIG
  • Authors:
    • Craig, R N
  • Publication Date: 1971-9

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00236253
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 8 1972 12:00AM