The influence of history of water load on tunnel stresses is discussed from the point that Water load on tunnel is seepage body force, corresponding calculation method is proposed and an engineering project designed by this method is given as an example.
Die Wasserbelastung eines Tunnels ist eine Feldkraft. Von diesem Standpunkt aus wird der Einfluss der Geschichte der wassrbelastung auf die Spannungen des Tunnels diskutiert. Eine entsprechende Berechnungsmethode wird vorgeschlagen. Eine nach dieser Methode konstruiertes Projekt wird als Beispiel angegeben.
La charge d''eau provenant du tunnel constitue la force volumetrique. Le texte discute, a partir de ce point de vue, l''histoire de la charge d''eau ainsi que son influence a l''egard de la pression du tunnel. On a pr''e sen t.e la methode de calcul correspondante et donne des exemples de travaux concus d''apres cette methode.
The water load is generally considered as an inchangeable load acting on the boundaries of the lining in tunnel design. This simplification being unable to reflect the actual condition of water load on tunnel often leads to a conservative or unsafe design.
Tunnel is a structure in rock mass with concrete lining as usual. Both rock mass and concrete are porous media. Water Percolating through these media forms a potenb1al field H(x1, x2, x3) of seepage body forces, which act at every point of the field with three components:
(Figure in full paper)
From this point of view it implies that the process of tunnelling and lining will change the boundary conditions. Seepage potential field will be changed according to the change of boundary conditions even though the water head remains unchanged. Consequently the water load also varies in pace with various stages during tunnel construction so it has its own loading history. This is another important characteristic of water load acting on tunnel .
The permeability factor of intact rock is very small, being in order of 10−7 - 10-10cm/s, but permeability factor of rock mass is considerably greater (about 103–106 times) than that of intact rock  . This remarkable difference is caused by joints, cracks and fractures in rock mass with a width of 1 mm or sometimes greater than 10 mm. Fractures in rock mass connected with each other will form seepage passages for water. Fractures usually appear in groups. Each group of fractures has almost the same orientation, so the rock mass shows evidently the anisotropic permeability. As the permeability, of fractures is much greater than that of intact rock, we can approximately assume that the intact rock is impervious. Supposing the seepage flow in fracture is evenly distributed throughout the rock mass as a whole, we get a model of anisotropic homogeneous permeable medium. In general, the velocity vector at a point in space of anisotropic seepage potential field does not coincide with potential gradient and form an angle with it.