Skew (or Skew Angle)

The acute angle formed by the intersection of the line normal to the centerline of the road improvement, with the centerline of a culvert or other structure.

Skin Friction

Resistance to thrust caused by soil pressure around the casing.

Skinning

The act of fitting a steel cylinder over the MTBM shield body to increase the diameter of an existing MTBM with the use of an appropriately upsized cutter wheel. Also referred to as upsizing or shimming.

Sleeve Pipe

A pipe installed as external protection to a product pipe.

Slide

Movement of a part of the earth under force of gravity.