11.5 Ground Settlement
Settlement is the movement of the surface ground caused by the tunnelling operation as well as consolidation due to groundwater removal. The potential for settlement of the surface because of the tunnelling operation must be assessed from the geotechnical investigations undertaken and appropriate measures should be taken to minimise and control it. Where such settlement will result in damage to buildings or property, then that property may have to be acquired or an appropriate compensation and/or damage repair program implemented as part of the tunnel planning process.
To minimise possible claims for property damage, a property condition survey should be undertaken to records the condition of existing structures or buildings. The survey records the condition of a property, either prior to construction commencing or at a subsequent point in time and involves an inspection and photographic record of the structure or building.
Some soil formations may be susceptible to vibration caused by the tunnel construction and such effects may be at some distance from the actual site. The geotechnical investigation should establish the presence or otherwise of such soil profiles and action should be taken to adopt construction methods that limit vibrations to a suitable level. Where buildings or property may be harmed by such vibration, suitable mitigation and/or repair strategies will be required.