Soil Arching in Sandy Slopes

Abstract

Recently soil arching theory has been extended to the study of forces and stresses exerted by a yielding soil mass against discrete piles embedded in a slope and extending into a firm, non‐yielding base. Many uses of discrete pile retaining wall systems exist in current geotechnical practice. In each case, soil arching has been relied upon to some extent as a means of stabilization without concise information about the required spacing of the stabilization piles. This lack of information requires a design engineer to err on the conservative side, and to place the piles closer together than they need be. This study examines the role of soil arching in discrete pile retaining walls and provides an information base for rational design. The present research objective is to experimentally model soil arching action between piles, to determine the influence of and relationships between the essential parameters, and to compare predictions from several new arching theories to experimental model results. The results of the experimental and theoretical comparisons indicate that discrete piles embedded in a slope into a firm, non‐yielding base, can provide significant additional stability to a slope if conditions for soil arching are met. Files can be installed without significantly decreasing slope stability during construction. For retaining walls that rotate vertically about the base between “fixed” side supports, the data obtained by the modified Bransby and Smith numerical method closely approximates experimental results. The stress transfer ability of loose soil is greater than previously thought. A loose deposit does not preclude the possibility of mobilizing soil arching or side friction. In soldier pile and lagging systems, material costs, strengths, and sizes can be optimized to achieve maximum benefit from soil arching.