DIFFICULT EXCAVATION AT CARLEY PORTER TUNNEL

DIFFICULTIES ENCOUNTERED IN CONSTRUCTION OF THE TUNNEL, AND THE MEASURES TAKEN TO OVERCOME THEM, ARE DESCRIBED AND DISCUSSED. THE TUNNEL IS A LINK IN THE CALIFORNIA AQUEDUCT, THE MAIN ARTERY OF THE STATE'S WATER PROJECT. IT IS 25,000 FEET LONG, A DRIVEN DIAMETER OF 24 FEET, AND A FINISHED DIAMETER OF 20 FEET. THE TUNNEL WAS ADVANCED FROM TWO HEADINGS, BOTH USING A SHIELD-TYPE METHOD WITH A FABRICATED STEEL LINER PLATE SUPPORT SYSTEM. RUNNING AND CAVING ACCOUNTED FOR 90% OF THE 16-MONTH LATENESS IN TUNNEL COMPLETION, RESULTING FROM THE FACT THAT THE TUNNEL CROSSES A PORTION OF A RANGE DOMINATED BY THE TWO LARGEST FAULTS IN CALIFORNIA. WHEN INTENSE GROUND LOADING FOLLOWING A FIRST RUN HAS NECESSITATED DRIVING SEVERAL SMALL DRIFTS ALONG THE OUTER SURFACE OF THE SHIELD, A SECOND RUN OCCURED FROM DECOMPOSITE GRANITE, COMING DOWN IN FRONT OF THE SHIELD AND FORMING A CHIMNEY 200 FEET TO THE SURFACE. A SINK HOLE WAS CREATED ON THE SURFACE DIRECTLY ABOVE THE FRONT EDGE OF THE SHIELD. THE MANNER OF HANDLING THIS RUN, AND A SUBSEQUENT ONE IS DESCRIBED, ENTAILING THE USE OF CHIMNEY GROUTING, NEAT CEMENT PLACED BETWEEN THIS GROUT AND A CHEMICAL LAYER, DRAIN PIPES FROM THE GROUTED AREAS TO THE TUNNELED SECTION, AND GROUT PIPES. SUBSEQUENTLY, TO HANDLE THE PROBLEM OF SOLIDIFYING THE MATERIAL IN FRONT OF THE SHIELD, CASED HOLES WERE DRILLED FROM THE SURFACE TO THE TUNNEL GRADE, AND A NEAT CEMENT GROUT WAS INJECTED INTO THE LOOSE MATERIAL. THE METHOD USED TO MINE THROUGH AND RESUPPORT A COLLAPSED SECTION OF TUNNEL IN A FAULT ZONE CONTAINING GOUGE IN THE LAKE BED SEDIMENTS IS DESCRIBED AND ILLUSTRATED, AS IS THE PROCEDURE DEVISED FOR CONSTRUCTING A SHIELD ERECTION ROOM FOLLOWING FRACTURE AND COLLAPSE OF A SHIELD. THE NEW SHIELD WAS MADE OF A36 STEEL RATHER THAN T-1 ALLOY FOR REASONS OF WELDABILITY, ECONOMY, AND AVAILABILITY.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/oclc/10480594
• Supplemental Notes:
  • Vol 40, No 6, PP 66-69, 3 FIG
• Authors:
  • Varello, P J
• Publication Date: 1970-6

Media Info

• Serial:
  • Civil Engineering
  • Publisher: American Society of Civil Engineers
  • ISSN: 0885-7024
  • Serial URL: http://www.pubs.asce.org/ceonline/newce/html

Subject/Index Terms

• TRT Terms: Chemical grouts; Chemicals; Chimneys; Earth pressure; Faults; Grout; Mining; Shields (Tunnels); Steel; Tunneling
• Uncontrolled Terms: A36 steel
• Old TRIS Terms: Caving /mining/; Geological faults; Runs /tunneling/; Shields (Tunneling)
• Subject Areas: Bridges and other structures; Construction; Highways;

Filing Info

• Accession Number: 00215376
• Record Type: Publication
• Files: TRIS
• Created Date: May 10 1971 12:00AM