Hydraulic Properties of Karst Groundwater and Its Impacts on Large Structures

Abstract

A karst environment is a particularly sensitive and risky geological formation for the infrastructure construction from the micro to the mega scale. The hydraulic properties and specific regime of groundwater in karst are, in many cases, the source of catastrophic failures. The most common destructive influence of groundwater is the consequence of: massive turbulent flows; the fast erosion of unconsolidated deposits in caverns and joints; the great kinetic energy of underground flows; propagation of hydraulic pressure at large distances (piston effect); and the enormous hydraulic pressures created in periods of full aquifer saturation, including water-hammer and air-hammer effects due to rapid fluctuation of the water levels. Despite extensive investigations, the destructive impacts are mostly unpredictable in space and time. In many cases these destructive processes take time to become established but final effects appear abruptly, causing considerable damages or failures. The most common consequences of these impacts are subsidence at the urban areas, along the roads and railways, as well as at the bottom of reservoirs; water seepage from reservoirs; break-in of groundwater under high pressure during underground excavation; destruction of surface remediation structures; destruction of tunnel lining; degradation of grout curtains, induced seismicity; decreasing of downstream spring discharges; endangerment of underground species; and the creation of many other unpredictable and unexpected problems. Some dam failures (empty reservoirs) or collapses (entire buildings and factories sinks) were catastrophic. Successful remediation solutions require serious and comprehensive investigations including long period monitoring of groundwater regimes and (in many cases) remedial works during the lifetime of the structure. During construction modifications and adaptations of structures are very common in karst. Persistent, time-consuming and expensive remedial works during the lifetime of the structure are no exception, but, rather, they are the rule.

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