What Does Systematic Settlement Mean?
Systematic settlement occurs as a result of voids in the annular space between the pipe and the soil due to the collapse of the overcut or the annular space.
It can also occur as a result of the elastic deformation of the soil in front of the advancing bore. The soil collapse can be seen on the ground surface as a trough. There are two types of settlements that can occur during trenchless pipeline installation namely, systematic settlement and large settlement.
Trenchlesspedia Explains Systematic Settlement
Settlement is the vertical movement of soil in the downward direction, especially in soft or loose soil strata. Soil settlements are mainly caused by trenchless construction methods when proper geotechnical investigation to determine the correct method suitable for soil type is not carried out. Systematic settlement reduces with distance above the crown of the pipe and with lateral distance from the pipe's centerline.
It also decreases with a decrease in overcut, increase in density and stiffness of soil, and an increase in bore diameter. When a proper investigation is carried out it helps in the selection of proper methods and tools, special attention if required by the contractor and use of ground improvement methods to control anticipated ground conditions.