Backfilling of the annular gap is of essential importance in mechanized tunneling. Depending on the geological and hydrological boundary conditions, various grout systems (one- and two-component) are available. Regardless of the system, two more or less conflicting requirements are placed on such mortars at the same time. On the one hand, a long workability time and a high flowability are required in order to be able to completely fill the annular gap; on the other hand, it is assumed that the mortar quickly develops sufficient stiffness and shear strength immediately after grouting, which are at least in the orders of magnitude of the soil in place.
1st project phase (July 2010 to June 2014):
Funding Period I focused primarily on single-component grouts that stiffen by squeezing water into the adjacent rock. Within the framework of the subproject, one-component mortars were systematically investigated in experiments by varying relevant material- and installation-specific parameters with regard to the decisive properties - flowability, sedimentation stability, drainability and strength development. The relationships between the parameters of individual starting components or the composition of the mortar and its properties were fundamentally investigated. Mortar compositions commonly used in practice were used as a reference.
2nd project phase (July 2014 to June 2018):
In addition to supplementary investigations on the formation of filter cakes in single-component mortars, the focus in funding period II was on the development of multi-component mortars. Here, a second component B is added to a flowable mortar (component A) immediately before grouting into the annular gap, which rapidly leads to stiffening/solidification of the mortar system. These are used when single-component mortars cannot drain sufficiently, e.g. due to low permeability of the surrounding soil. In addition to the material technology investigations, a test rig was developed with which annular gap grouting can be realistically simulated on a semi-technical scale.
3rd project phase (July 2018 to December 2022):
The main objective in funding period III is to develop deformable mortars for annular gap grouting in compressive rock based on the present orienting approaches. Such mortars should be capable of absorbing or compensating to a certain extent for the radially acting rock deformations by means of a pronounced compressive capacity and thus contribute to the long-term stability of the tunnel lining. The modifications can essentially be made by admixing different compressible components (intrinsically porous systems of different material configurations such as lightweight aggregates, plastic foams, etc.). Alternatively, the use of per se porous material is focused. In the overall project area "B" of SFB 837, the knowledge gained contributes to the overall objective of developing a deformable tunnel lining in the system "compressive rock - annular gap mortar - segment".
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Last update: Apr 25, 2024
