STABILITY OF SLURRY TRENCH EXCAVATIONS IN SOFT CLAY

A SEMI-EMPIRICAL METHOD IS DESCRIBED FOR ESTIMATING THE STABILITY OF THE SIDE FACES OF A DEEP CUTTING WHICH IS PARTLY OR COMPLETELY FILLED WITH A LIQUID OF LOW SHEAR STRENGTH. CONCERNING THE SLIDING MASSES IT IS ASSUMED THAT A FAILURE WILL ONLY OCCUR IN THE VERTICAL PLANE OR IN AN INCLINED PLANE OF 45 DEGREES. THIS MAKES IT POSSIBLE TO CLARIFY, IN A SIMPLE FASHION, THE BEHAVIOUR OF THE ANISOTROPIC GRAINED SHEAR FORCE IN CLAY. SO IT IS ASSUMED THAT A MODIFIED "WING" FORCE IS RELEVANT FOR THE FAILURE ALONG VERTICAL PLANES AND THAT THE STRAINED TRIAXIAL COMPRESSIVE STRENGTH OF SAMPLES, COMPRESSED TO THE IN-SITU STRESSES, IS RELEVANT FOR THE FINAL MOBILIZED RESISTANCE OF THE PLANE INCLINED AT 45 DEGREES. THE PROPOSED METHODS ARE USED IN ORDER TO DERIVE THE SAFETY FACTORS OF THE SIX SLURRY TRENCH WALLS, OF WHICH FOUR HAVE EXPERIENCED AN INNER DIRECTED FAILURE OF THE SIDE SURFACES. THE CALCULATIONS RESULT IN REASONABLE SAFETY FACTORS FOR ALL EXCAVATIONS WITH "NORMAL LIFE SPANS", I.E. BETWEEN ONE AND A FEW DAYS. IN THOSE CASES WHERE THE EXCAVATION WAS LOADED QUICKLY TO FAILURE, IN WHICH THE SUPPORTING LIQUID WAS PUMPED OUT, THE ANALYSES GAVE SAFETY FACTORS UNDER UNITY AND THUS PROVED THE SAFETY OF THE METHOD. FOR ALL SIX CASES THE CORRELATION BETWEEN THE CALCULATED CRITICAL DEPTHS WHICH NEED NOT NECESSARILY CORRESPOND WITH THE TOTAL DEPTH OF THE EXCAVATION, AND THE OBSERVED DEPTH OF MAXIMUM DEFORMATION WAS GOOD. THE COVERING ABSTRACT FOR THE CONFERENCE IS IRRD NO 306088.

  • Authors:
    • AAS, G
  • Publication Date: 1976-3

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 01301873
  • Record Type: Publication
  • Source Agency: Bundesanstalt für Straßenwesen (BASt)
  • Files: ITRD
  • Created Date: Nov 21 2010 8:25AM