Hydrogeology of Crystal Rocks in the Planning and Construction of Underground Structures

Abstract

Underground excavations usually have a significant impact on hydrogeological runoff. Water seepage affects underground construction and the long-term behaviour of the structure. The flow paths can be altered by underground activity and the spring areas can become infiltration zones. Concerning the healthy massif, permeabilities near a cavity can increase or decrease. The increase in permeability through excavations in an environment of shear stress and associated water inlets, have a lapse, which can lead to problems in mechanized tunnels when falling below a critical feed rate. When a rock mass is drained, deformations occur, which are reflected in surface settlements; the drainage of the massif causes changes in the physical parameters and the chemical composition of the groundwater. The characteristics of the leaks found in tunnels and drains do not reflect the state of the unaffected groundwater. Numerous parameters in the forecast can lead to over- or underestimations of the actual flow rates of water seepage. In addition to a forecast, it is recommended to carry out sensitivity and risk analyses, in particular to exceeding the value of the forecast and when assessing environmental compatibility, the worst possible scenario