Untersuchungen zur Zementfiltration während der Herstellung von Verpressankern in nichtbindigen Böden

Cement grout filtration during installation of grouted ground anchors in non-cohesive soils

Pressure grouting during installation of grouted ground anchors is known to increase anchor capacity in non-cohesive soils, but little information is available on correlations between applied grouting pressures, duration of grouting, ground conditions and increase of anchor pull-out capacity.
Based on laboratory and in situ tests as well as numerical simulations the processes taking place during installation of grouted ground anchors are investigated for non-cohesive soils. It was aimed to determine the influence of pressure grouting on the stresses on the anchor body and the properties of the adjacent soil. The knowledge of those is considered prerequisite in order to determine the anchors pull-out capacity.
Laboratory experiments are presented, which investigated the filtration process of cement grouts and the properties of the filter cake material, taking into account the influence of grouting pressure and initial water/cement ratio of the grout.
In in situ tests during anchor installation the grout pressure was measured inside the borehole during and after anchor installation. Measurements confirmed a grout filtration inside the grouting length and indicated the increase of radial stresses on the anchor body.
Finally a numerical model is proposed to simulate the filtration process of cement grout in a fully coupled flow-displacement finite element analysis.