Overview
Practical application tests with sprayed sheet systems for tunnel construction come across the same principal style of questioning over and over again. This is because initially the use of sprayed sheets is not a question of the new product but it is a question of a partially new system of construction.
With the proposed testing programme the general influence of the use of the sprayed sheet system in underground construction will be tested from a technical and economical point of view.
The main objective of the project is to record and evaluate the overriding technical and economical factors which influence the use of the sprayed sheets in tunnel construction.
The project went through following steps:
- There were questions concerning the drainage concept and the bearing capacity of the composite system because the sprayed sheet is connected to the underground as well as to the overlying stratum. This overriding questioning has been tested independently of the products through model calculations and studies.
- Particularly the adhesive compound of the two support basins which is produced by the sprayed sheet leads to a greater bearing capacity of the whole system. The dimension of the increase in bearing strength is established as a function of the compound strength by simulated calculations.
- Changes in the construction of the sealing system with sprayed sheets in comparison to the conventional prefabricated sealing sheets make a new conception of the drainage system necessary. The drainage function of the protective flow has to be taken over by other drainage measures. A basic concept which also considers the problem represented by scale deposits have been prepared.
Funding
Results
The main question, which was also the trigger for the research has been answered in the sense that the spray seals effects are only subordinated to the structural system of the liner. Decisive for the formulation of requirements for spray films are the issues of the seal piercing technology.
Thus the question of the economic savings potential by influencing the static support system has become obsolete and was not pursued in the context of work.
With regard to the applications of spray seals the issues of durability in the future are yet to be treated.
In many fundamental issues washing and sealing problems have been affected in the context of research, some of which are very controversially discussed. As a part of the research project, these aspects have been excluded. However, it seems that it exists a considerable need for further research.