TABLE OF CONTENTS Most of the systems discussed in Chapter 3 have fascia elements that are integral with the primary vertical elements. Sheet piling presents full face coverage. Secant piles and tangent piles cover the entire excavated face with the concrete placed in the excavated shaft. Slurry walls present a complete face of tremied concrete and Trench Boxes incorporate the facing panels as an integral part of the box.
Three systems have separate fascia systems. These are soldier pile and lagging, soil nailing, and micropile walls. Underpinning in Chapter 3 is often actually an adaptation of soldier pile and lagging and so will not be dealt with separately. In soldier pile, and lagging and micropile walls, the fascia is called lagging while the fascia of soil nailed systems is a thin shell placed by shotcrete methods.
The word lagging, as it is used it in the earth retention industry, has nothing to do with the facing on a hoisting drum, nor the habit of falling behind. Lagging, in this context, describes the material used to span the gap between soldier piles. While it is usually wood, and placed by hand, it does not necessarily have to be so. It can be of concrete or steel. The span between soldier piles is normally in the range of 6-10 feet (1.8-3.0 m). Soldier pile and lagging systems are designed as free draining systems, so that any water which encounters a lagged wall is expected to seep through the wall. Timber lagging is therefore...
