GEOLOGIC ASPECTS OF SOFT-GROUND TUNNELING

SOIL MECHANIC FACTORS THAT DETERMINE TUNNELING CONDITIONS FOR A PROPOSED EARTH TUNNEL ARE DISCUSSED. IN CONNECTION WITH SOFT-GROUND TUNNELING, THE DIFFICULTIES IN COST OF CONSTRUCTION OF THE TUNNEL WITH GIVEN DIMENSIONS DEPEND ALMOST EXCLUSIVELY ON THE STAND-UP TIME OF THE GROUND. THE STAND-UP TIME INDICATES THE TIME THAT ELAPSES BETWEEN THE EXPOSURE OF AN AREA AT THE ROOF OF THE TUNNEL AND THE BEGINNING OF NOTICEABLE MOVEMENTS OF THE GROUND ABOVE THIS AREA. THE FACTORS THAT DETERMINE THE STAND-UP TIME OF AN UNSUPPORTED ROOF AREA WITH GIVEN DIMENSIONS DEPEND TO A LARGE EXTENT ON THE POSITION OF THE WATER TABLE. ABOVE THE WATER TABLE, THE STAND-UP TIME DEPENDS ESSENTIALLY ON THE TENSILE AND SHEARING STRENGTH OF THE GROUND. SIX PRINCIPLE CATEGORIES OF GROUND MUST BE DISTINGUISHED: FIRM, RAVELING, RUNNING, FLOWING, SQUEEZING, AND SWELLING. THESE CATEGORIES ARE DISCUSSED AND DEFINED. SERIOUS DIFFICULTIES THAT MAY BE ENCOUNTERED DURING THE CONSTRUCTION OF AN EARTH TUNNEL AR& DIRECTLY OR INDIRECTLY DUE TO THE PERCOLATION OF WATER TOWARDS THE TUNNEL. METHODS OF IMPROVING THE PROPERTIES OF SOFT GROUND ARE DESCRIBED. RELIABLE INFORMATION ON SUBSOIL CONDITIONS ARE OBTAINED BY MEANS OF TEST BORINGS. IT IS CONCLUDED THAT MORE KNOWLEDGE IS NEEDED IN THE FIELD OF SOFT-GROUND TUNNELING ON THE DETAILS OF THE STRUCTURE OF SEDIMENTARY DEPOSITS, THE BEHAVIOR OF DIFFERENT SEDIMENTS AT TUNNEL HEADINGS, AND THE LOADS ON TEMPORARY AND PERMANENT TUNNEL SUPPORTS.

• Supplemental Notes:
  • Applied SedIMENTATION, PP 193-209, 6 FIG, 10 REF
• Corporate Authors:

  John Wiley & Sons, Incorporated

  111 River Street
  Hoboken, NJ  United States  07030-6000
• Authors:
  • Terzaghi, K
• Publication Date: 1950

Subject/Index Terms

• TRT Terms: Boring; Businesses; Excavation and tunneling; Geology; Loads; Percolation; Sedimentary rocks; Shear strength; Soft rock; Soil mechanics; Soil tests; Stripping (Pavements); Structural supports; Subsoil; Swelling; Swelling soils; Tensile strength; Tunneling; Water table
• Old TRIS Terms: Firm; Geology (Soils); Percolation rate; Sedimentary deposits; Soil swell; Supports
• Subject Areas: Bridges and other structures; Geotechnology; Highways; Hydraulics and Hydrology;

Filing Info

• Accession Number: 00234419
• Record Type: Publication
• Files: TRIS
• Created Date: Dec 9 1994 12:00AM