RT Journal Article
T1 In-situ stress amplification due to geological factors in tunnels: The case of Pajarestunnels, Spain
A1 Hijazo Ramiro, Teresa
A1 González De Vallejo González, Luis Ignacio
AB Geological and geomechanical anisotropies can significantly increase the magnitude of in-situ stress in a rockmass excavated for tunnelling purposes. Four tunnels for the new high-speed railway lines in Pajares in theCantabrian Mountains, N. Spain, were analysed and significant deformations was found to have occurred inforty specific zones of these tunnels during excavation, requiring much more support than envisaged beforeconstruction. Local factors influencing in-situ stress have been identified in these zones of the tunnels, related togeological structures of high compressive tectonic stress regimes including thrust faults, folds with steep flankdip, orwith geomechanical anisotropies in contact zones between rock formations of different strengths. Amethodologicalprocedurewas applied to four tunnels to assess the influence of the geological anisotropies on the insitustress magnitudes. This procedure is based on the analysis of tunnel deformations and the support pressureneeded to stabilise the excavations affected by geological anisotropies.The increase of in-situ stress due to local factors is expressed by the Stress Amplification Factor (SAF) definedby the ratio between the K(σH/σV)local value estimated in a particular rock mass tunnel zone andthe mean K(σH/σV)regional value representative of the whole rock mass tunnel. Kregional was estimatedfrom hydrofracture tests and from the TSI index. Klocal was calculated from the back analysis of the supportpressure required to stabilise the deformed tunnel zones. SAF values for the forty specific tunnel zones rangedfrom 1.1 to 2.5. This significant increase in the magnitude of in-situ stress emphasises the influence ofgeological and geomechanical anisotropies in tunnel stability and support design. The results provide aquantitative approach for assessing structural stresses in rock masses for tunnelling excavations.
PB Elsevier
SN 0013-7952
YR 2012
FD 2012
LK https://hdl.handle.net/20.500.14352/42188
UL https://hdl.handle.net/20.500.14352/42188
LA eng
DS Docta Complutense
RD 8 abr 2025