Clay Pipe Installation Handbook

Appendix: Microtunneling and Glossary

Microtunneling is a revolutionary method of installing clay pipe without the need of excavating trenches.

Procedure: A launch pit is excavated at the location of a future manhole. A thrust wall is installed to resist the jacking force. A lazer guided cutting head and shield is jacked into the ground at the proper horizontal and vertical alignment and pipe after pipe are jacked through from behind. The excavated soil is conveyed through the pipe by slury or auger and removed at the launch pit. The operation continues until the cutting head, shield and pipe emerge into a receiving pit which is normally the location of a future manhole.

Microtunneling is still a specialized application for installing clay pipe. For additional information about this unique technology, contact the National Clay Pipe Institute or its member companies. Also see ASTM C 1208 Standard Specification for Vitrified Clay Pipe and Joints for use in Jacking, Sliplining and Tunnels.

microt1.GIF (4934 bytes)

Glossary

angular material - a fractured and suitably sized bedding for pipe and fittings.

ASTM Standard - manufacturing, installation and testing standards issued by the American Society for Testing and Materials.

bedding material - material placed under and around clay pipe to develop the required load factor.

compaction - hand, mechanical or water consolidation of backfill.

density - a relative measure of the consolidation of a bedding or backfill material.

design trench width - trench width at the level of the top of the pipe.

final backfill - material used to fill the trench from the initial backfill to the finished ground surface.

geofabric - a drainage fabric which allows the flow of water while preventing the movement of soil.

gradeliner - a device that transfers the line and grade data from the survey markers to the location of the invert of the pipeline.

haunch - area of the bedding under the lower quadrants of the pipe.

initial backfill - native or import material extending from the top of the bedding material to a height ol 1-foot above the top of the pipe barrel.

load factor - ratio of the field supporting strength ol the pipe to its specified 3-edge bearing strength.

laser - a device that sends a straight beam of lighi on the proper line and grade to a target.

log book - daily record of construction activity.

migration - the movement of soil into adjacent material.

native material - material present in or which has been removed from the trench.

OSHA - Occupational Safety and Health Administration.

riser - building sewers connected to deeper main lines.

sheeting - wood or metal restraints used to suppori the trench walls.

shield - movable trench box used in place of sheeting and shoring.

shoring - equipment used to prop or support the trench sheeting or trench wall directly.

slicing - the act of consolidating the bedding material in the pipe haunch areas usually with a shovel.

stopper - a temporary plug inserted in a pipe or fitting.

tapping - the method used to field connect a building sewer to a main line.

waterstop - vertical barriers placed across the bottom of the trench to prevent migration of soil fines due to water movement.

well points - single or multiple pipe which are usually fitted with a screen for the temporary removal of water from the bottom of the trench.

NCPI - Clay Pipe Installation Handbook

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