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Joint opening and head distribution in the foundation rock of the Albigna Gravity Dam


The interaction between joint water pressure and joint opening in the rock foundation of dams may play a crucial role both for seepage loss and stability analysis. A comprehensive research project was car-ried out in the rock foundation of the Albigna gravity dam focusing on the monitoring of head distribution along a number of long boreholes with the Piezodex sliding piezometer probe and on the measurement of strain profiles with the Sliding Micrometer. The observation of the deformational behavior and the piezometric pres-sure distribution as a function of seasonal reservoir water level fluctuation over a period of 6 years yielded a wealth of interesting information. In the granitic rock mass two large "active joints" could clearly be identified which open and close due to variation of the reservoir water level. At a given critical water level the opening of the joints becomes specially pronounced leading to a higher water conductivity. A back analysis of the meas-ured potential field for several reservoir water levels indicates the correlation between the changing conductiv-ity of the two particular joints and their opening and closing.


Kovári, Kalman and Bergamin, Stefan

Index Terms:

piezodex; sliding micrometer; seepage; monitoring; measurements; rock; TunnelingGroup; analysis; large dam

Further Information:

Date published: 1994