SETTLEMENTS AND STRENGTHENING OF SOFT CLAY ACCELERATED BY SAND DRAINS

THE 24-ACRE SOUTH PORTAL ISLAND FOR THE SECOND HAMPTON ROADS CROSSING IN VIRGINIA WAS SURCHARGED AND THE COMPRESSION AND STRENGTHENING OF UNDERLYING SOFT CLAY WERE ACCELERATED BY JETTED SAND DRAINS TO MEET THE REQUIREMENTS OF AN ECONOMICAL CONSTRUCTION SCHEME, TO MINIMIZE POST-CONSTRUCTION SETTLEMENTS, AND TO MAINTAIN STABILITY DURING CONSTRUCTION. THE ISLAND WAS EXTENSIVELY INSTRUMENTED, AND THE PAPER PRESENTS ANALYSES AND CONCLUSIONS FROM SELECTED DATA. BOTH LABORATORY AND FIELD DATA INDICATE A MUCH HIGHER RATION OF UNDRAINED SHEAR STRENGTH TO OVERBURDEN PRESSURE THAN WOULD BE EXPECTED FROM WELL-KNOWN CORRELATIONS BETWEEN THIS RATIO AND PLASTICITY INDEXES. LABORATORY VALUES OF THE HORIZONTAL AND VERTICAL CONSOLIDATION COEFFICIENTS WERE LOWER THAN INDICATED BY MEASURED SETTLEMENT RATES; VALUES DERIVED FROM FIELD PERMEABILITY TESTS PROVED MORE RELIABLE. HORIZONTAL DISPLACEMENTS IN THE SOFT CLAY, ESTIMATED BY FINITE-ELEMENT ANALYSES AND MEASURED BY INCLINOMETERS, PROVED TO BE USEFUL INDICATORS OF THE OVERALL SAFETY OF THE SLOPES. THE EFFECT OF UNKNOWN FACTORS AND VARIABLE SOIL PARAMETERS WAS MINIMIZED BY CONSTRUCTION DOCUMENTS WRITTEN WITH A SPECIFIC BID ITEM FOR "DELAY TIME", A DEVICE THAT PROVED FINANCIALLY BENEFICIAL. THE SOLUTIONS TO THE PROBLEMS OF THIS SITE CAN BE USED FOR SIMILAR SAND DRAIN PROJECTS WHERE THERE IS SUBSTANTIAL UNCERTAINTY AND VARIATION OF THE SOIL PARAMETERS. THE SOIL PARAMETERS REPORTED ARE, OF COURSE, APPLICABLE ONLY TO SIMILAR EXTENSIVE NONSTRATIFIED CLAY DEPOSITS.

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 18-26
  • Monograph Title: Soil slopes and embankments
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00236755
  • Record Type: Publication
  • ISBN: 0309021901
  • Files: TRIS, TRB
  • Created Date: Jan 31 1974 12:00AM