Discussion of construction norms

Conclusions

• 1. In the cases in which grouting is applied to reduce the inflow of ground water into the relieving drainage conduits of the linings of free-flow underground structures, it is recommended that the grouted zone (thickness 2–10 m) be constructed at a certain distance (1–3 m) from the surface of the lining, and that the drainage conduits be located in an ungrouted layer between the lining and the grouted zone.

• 2. The proposed type of construction ensures a high relieving effect of the drainage system, which cannot be achieved with other well-known combinations of drainage elements in the grouted zone, and permits lightening the linings of underground structures.

• 3. The formulas presented in this article make it possible to carry out, with a sufficiently high degree of accuracy, the analyses required for designing transverse-hole or longitudinal tubular drainage systems in combination with impervious grouting, as well as other analyses connected with seepage in the design of underground structures.

• 4. In order to establish the degree of agreement among the analytical, laboratory (by the electrohydrodynamic-analogy method, etc.), and full-scale data, it is necessary to measure on the constructed structures the residual heads acting on the linings, as well as the flows seeping through the grouted zone into the drains, or, in the absence of drains, through the lining and into the structure.