Comparison of different approaches to model compensation grouting

Settlement related building damage caused by the construction of new tunnels has become a major issue in new urban infrastructure projects. Protective measures, such as compensation grouting are now often applied in order to minimize the impact of tunnelling on existing structures. It has been observed during different construction projects that the pressure due to grouting can have a damaging effect on the lining of newly constructed or existing tunnels and therefore it is often required to allow for the load due to grouting in tunnel lining design. Numerical methods are frequently used for this purpose. However, there is a lack of understanding of how the grouting pressure is transferred into the ground. This paper presents a plane strain Finite Element (FE) study in which compensation grouting is modelled in detail by incrementally applying the grouting pressure over a range of grouting ports. The results are compared with analyses in which the grouting pressure is applied over a wider extent of the tube-a-manchette (TAM) and recommendations are given for the FE modelling of compensation grouting.