Subproject B4 (finished)

Annular Gap Grouting: Hydro-Chemo-Mechanical Modeling and Space-Resolved Experimental Investigations


Overview

A classical consolidation process for weakly permeable and impermeable soils leads to unsatisfactory results with respect to the dewatering process of the annular gap grout. In order to ensure a sufficient stiffness development also under these circumstances, a two-component mortar had been investigated in the second phase of the project. The mortar mixture contains superabsorbent polymers (SAPs), which promote a rapid gelation process of the mortar within the annular gap. The water absorption as well as desorption phenomena in the multi-phase material had been modeled by a continuum-based mixture theory. The model had been calibrated and validated by experimental water absorption tests.

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Mass exchange between pore fluid and hydrogel can be observed over time. On the microscale, swelling is consequence of local fluid flow. Statistical homogenization leads finally to a macroscopic description of the mass exchange.


Ultrasound wave propagation through a mixture of glass beads and swollen superabsorbent polymers within a triaxial cell. P-wave modulus is plotted against the stress deviator q for various mass fractions of the hydrogel w. The deviator is normalized by the cell pressure. The stiffness of the mixture can be increased with respect to the initial state by choosing the right dosage of hydrogel in the mixture.


Representative Volume Element (REV) for the multi-phase material. S: solid skeleton, G: hydrogel, F: porefluid.


Two-component grouting mortar in annular gap (Initial-Boundary-Value-Problem)


Measuring the P-wave velocity within a triaxial cell. The P-wave modulus of the material can be deduced from the experimental data.