Slope stability problems exist within the Appalachian Basin as a result of the emplacement of coal mine waste materials on mine outslopes. Prevention or elimination of slope instability problems can be costly. In an attempt to test alternative methods of slope stabilization, the U.S. Bureau of Mines determined some physical characteristics and shear strengths of ungrouted and polyurethene- grouted samples of coal refuse, coal spoil, and natural soils collected at a number of mine outslope sites in Pennsylvania and West Virginia. The particle size distribution, percent field porosity, percent field water content, and shear strengths of the materials were determined in the laboratory. Fifty drained direct shear strength tests were performed with the sample materials using a 0.06-M3 shear box. Tests were done at field moisture, 100-pct saturation, and grout-infused conditions. Normal loads of 103 kn m- 2, 206 kn m-2, and 416 kn m-2 were used. The grout-infused tests generally showed strength increases. An infinite slope model was used to demonstrate the potential effectiveness of in situ grouting for a variety of field slope conditions. This modelling suggests that in situ grouting has the potential of stabilizing slopes of up to 35 deg at depths of 14m for refuse material and 30 deg at depths of 5m for spoil and soil materials. The validity of these increases in material strength by grout injection will require field testing for confirmation.
Int. J. Min. and Geol. Eng., V. 8, 1990, PP. 227-240