Method for grouting pipe liners

A method of lining a pipe, said pipe having a longitudinal extent and a predetermined internal diameter, said pipe further having access to the interior thereof from the surface at first and second longitudinally spaced-apart access manholes, said method comprising:

• placing a tubular liner in said pipe, said liner having an external diameter such that an annular cavity is formed intermediate said pipe and said liner, an interior of said liner being maintained at substantially atmospheric pressure and said liner further having a tendency to collapse if subjected to an external pressure which is in excess of a maximum pressure which exceeds atmospheric pressure by a predetermined amount;
• forming a pumpable cement grout, said grout comprising:
• hydraulic cement;
• water in an amount sufficient so that the water-to-cement ratio of said grout is from about 0.60 to about 1.00 by weight;
• and
• pre-generated aqueous foam in an amount sufficient to adjust the wet density of said grout to a value of from about 48 to about 72 pounds per cubic foot;
• pumping said cement grout under positive pressure into said annular cavity so that said grout fills said annular cavity by flowing in a generally longitudinal direction through said pipe from said first access manhole towards said second access manhole, said pressure under which said cement grout is pumped into said annular cavity being maintained about equal to or less than said maximum pressure;
• and
• terminating said pumping of said cement grout into said annular cavity when said flow of said grout through said pipe reaches said second access manhole.

A method for lining a conduit, said method comprising the steps of:

• placing a tubular liner in said conduit so that at least one cavity is formed intermediate said conduit and said liner, an interior of said liner being maintained substantially unpressurized and said liner having a tendency to collapse if subjected to an external pressure in excess of a predetermined maximum pressure, said conduit having an internal diameter equal to or less than about 60 inches so that access to said interior of said liner is available at least one manhole located along a length of said liner, and said liner being sized so that a radial clearance of about 3 inches or less is formed between said liner and said conduit;
• forming a pumpable cement grout, said grout comprising:
• hydraulic cement;
• water in an amount sufficient so that the water-to-cement ratio of said grout is from about 0.60 to about 1.00 by weight;
• and
• pre-generated aqueous foam in an amount sufficient to adjust the wet density of said grout to a value of from about 48 to about 72 pounds per cubic foot;
• pumping said cement grout into said cavity under positive pressure, so that said grout fills said cavity by flowing in a direction generally along an axis of said cavity;
• and
• maintaining said positive pressure under which said cement grout is pumped into said cavity intermediate said conduit and liner at about equal to or less than said predetermined pressure.