Settlement is defined as the vertical movement of soil in the downward direction especially in soft or loose soil strata. Trenchless technology involves the installation of pipes below the ground surface without digging a trench. Different methods such as horizontal directional drilling (HDD), pipe ramming and microtunneling are used depending on soil characteristics and purpose of installation.
Soil settlement can be caused in any of these methods if proper geotechnical investigation to determine the correct method suitable for soil type is not carried out.
Trenchlesspedia Explains Settlement
Settlement is generally seen on the ground surface over sub-structures like foundations or over pipelines. Settlement can be of two types namely, systematic and large. Systematic settlement occurs as a result of voids in the annular space between the pipe and the soil due to collapse or elastic deformation. Large settlement occurs as a result of ground loss due to over-excavation creating voids and sinkholes above the borehole.
To prevent this problem, pipelines should be tested before approval, and field monitoring and geotechnical investigation should be carried out.