Ground Improvement by Inclusions in Unstable Slopes-Paper

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The paper examines reinforced ground inclusions as a method for stabilizing unstable slopes and embankments. Unlike conventional micropiles designed mainly for vertical loads, grouted inclusions can resist bending and shear while improving the surrounding soil. Grout injected through sleeved pipes can increase soil cohesion and friction, with most improvement occurring within roughly 1.5–2 m of each borehole.<br /><br />Two principal layouts are discussed. Closely spaced, inclined micropiles can form a discontinuous reinforcing screen near an embankment edge, provided they extend sufficiently above and below the potential slip surface. Alternatively, inclusions can be grouped into transverse “knives” or buttresses spaced along the slope. Buttresses concentrate reinforcement while leaving gaps that allow water to drain. Their treated zones can be modelled as improved soil with increased strength; where closely spaced, they may be treated as relatively rigid blocks supported by inclusions embedded in stable ground. Larger or deeper movements may require more rigid systems, such as large-diameter piles or reinforced-concrete modules.<br /><br />A case study describes stabilization of a highway slope at Puerto de Pajares, Spain, where slow-moving instability affected a 70 m road section. The solution combined grouted-inclusion buttresses, a reinforced-concrete slab, and drainage wells with radial drains. Each buttress contained 15 injection holes in three rows. After construction, slope movements stabilized, and analyses indicated improved safety factors.<br /><br />The authors conclude that reinforced inclusions can provide an effective, adaptable slope-stabilization solution. Buttress spacing can preserve drainage, and representing treated ground as equivalent improved soil can simplify stability analysis.

Keywords

reinforced ground inclusions

slope stabilization

embankment reinforcement

grouted micropiles

soil improvement

grout injection

buttress reinforcement

drainage wells

stability analysis

Puerto de Pajares