Experimental effectiveness of rock fracture grouting

Abstract

The objective of this investigation is to experimentally determine the effectiveness of fracture sealing in welded tuff using ordinary portland cement and microfine cement grouts. Fracture grouting will most likely be used to seal fractures intersecting high level nuclear waste repositories. Fractures are potential pathways for the migration of radionuclides. Laboratory experiments have been performed on seventeen tuff cylinders. (1) tension induced cracks, (2) natural and, (3) sawcut surfaces serve as fractures. Prior to grouting, the hydraulic conductivity of the intact rock and that of the fractures themselves are measured under a range of normal stresses. Grouts are injected through axial boreholes at pressures of 0.3 to 4.1 MPa while holding fractures under a constant normal stress. Five grout formulations have been selected. Minor amounts of bentonite (0 to 5 percent by weight) have been added to these grouts to increase stability. Water to cement ratios range from 0.45 to 1.0. Permeameter testing of grouted fractures is used to evaluate the effectiveness of fracture grouting.