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LANDSLIDE TYPES AND PROCESSES

THE WHOLE RANGE OF EARTH MOVEMENTS THAT MAY PROPERLY BE REGARDED AS LANDSLIDES IS REVIEWED AND THESE MOVEMENTS CLASSIFIED ACCORDING TO FACTORS THAT HAVE SOME BEARING ON PREVENTION OR CONTROL. THE TERM LANDSLIDE IS DEFINED AS DENOTING DOWNWARD AND OUTWARD MOVEMENT OF SLOPE-FORMING MATERIALS COMPOSED OF NATURAL ROCK, SOILS, ARTIFICIAL FILLS, COMBINATIONS OF THESE MATERIALS. THE MOVING MASS MAY PROCEDE BY ANY ONE OF THREE PRINCIPLE TYPES OF MOVEMENT: FALLING, SLIDING, OR FLOWING, OR BY THEIR COMBINATIONS. MATERIALS ARE CLASSED, FOR FALLS AND SLIDES, INTO BEDROCK AND SOILS. LANDSLIDES ARE CLASSIFIED BY TYPES OF MOVEMENT, BUT IT MUST BE REMEMBERED THAT A RIGID CLASSIFICATION IS NEITHER PRACTICAL NOR DESIREABLE. VARIATIONS IN THE TYPE OF MOVEMENT AND IN THE MATERIALS VARY FROM PLACE TO PLACE, OR FROM TIME TO TIME, IN AN ACTUAL LANDSLIDE. SLUMPS AND SLUMPS COMBINED WITH OTHER TYPES OF MOVEMENT, MAKE UP A HIGH PROPORTION OF THE LANDSLIDE PROBLEMS FACING THE HIGHWAY ENGINEERS. THE MOVEMENT IN SLUMPS TAKES PLACE ONLY ALONG INTERNAL SLOPE SURFACES. SOME OF THE COMMON VARIETIES OF SLUMP FAILURE ARE ILLUSTRATED IN A FIGURE. THE PROCESS OF LANDSLIDING IS ESSENTIALLY A CONTINUOUS SERIES OF EVENTS FROM CAUSE TO EFFECT. IN MANY INSTANCES THE PRINCIPLE CAUSE OF THE SLIDE CANNOT BE REMOVED SO IT MAY BE MORE ECONOMICAL TO ALLEVIATE THE EFFECTS CONTINUALLY OR INTERMITTENTLY WITHOUT ATTEMPTING TO REMOVE THE CAUSE. LANDSLIDES GENERALLY TAKE PLACE UNDER THE INFLUENCE OF GEOLOGIC, TOPOGRAPHIC, OR CLIMATIC FACTORS COMMON TO LARGE AREAS. VERY SELDOM CAN A SLIDE BE ATTRIBUTED TO A SINGLE DEFINITE CAUSE. ALL TRUE SLIDES (EXCLUDING FALLS) INVOLVE THE FAILURE OF EARTH MATERIALS UNDER SHEAR STRESS. THE INITIATION OF THE PROCESS CAN THEREFORE BE REVIEWED ACCORDING TO: (1) THE FACTORS THAT CONTRIBUTE TO HIGH SHEAR STRESS, AND (2) THE FACTORS THAT CONTRIBUTE TO LOW SHEAR STRENGTH. THE PRINCIPLE FACTORS CONTRIBUTING TO THE INSTABILITY OF EARTH MATERIALS ARE: (1) REMOVAL OF LATERAL SUPPORT LEADING TO INSTABILITY AND ACTIONS OF EROSION, GLACIER ICE, WAVES AND LONGSHORE OR TIDAL CURRENTS; CREATION OF NEW SLOPE BY PREVIOUS ROCKFALL, SLIDE, SUBSIDENCE, OR LARGE SCALE FAULTING, AND HUMAN AGENCIES, (2) SURCHARGE WHICH INCLUDES NATURAL AND HUMAN AGENCIES, (3) TRANSITORY EARTH STRESSES WHICH MAY RESULT FROM EARTHQUAKES, VIBRATIONS FROM BLASTING, MACHINERY, AND TRAFFIC, (4) REGIONAL TILTING WHICH CAUSES PROGRESSIVE INCREASE IN SLOPE ANGLES, (5) RE- MOVAL OF UNDERLYING SUPPORT BY UNDERCUTTING OF BANKS, BY RIVERS AND WAVES, SUBAERIAL WEATHERING, SUBTERRANEAN EROSION, HUMAN AGENCY, SUCH AS MINING, AND (6) LATERAL PRESSURE DUE TO WATER IN CRACKS AND CAVERNS, FREEZING OF WATER IN CRACKS, AND SWELLING. FACTORS THAT CONTRIBUTE TO LAW SHEAR STRENGTH ARE DISCUSSED.

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  • Supplemental Notes:
    • pp 20-47, 28 FIG, 52 REF Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
  • Authors:
    • Varnes, D J
  • Publication Date: 1958

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  • Accession Number: 00235698
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 17 1970 12:00AM