Strength Characteristics of Three Indurated Horizons in Massachusetts

Abstract

Identification of fragipans is often difficult due to the lack of quantitative differentiating criteria. The unconfined compression (UC) test was used to characterize strength properties of three indurated horizons. Tests were performed in the laboratory on undisturbed core samples equilibrated to one of four moisture conditions: wet, 0.1 MPa, 0.5 MPa, or air‐dried. Fragipans developed in basal till exhibited maximum UC strength values of about 100 kPa at moisture contents < 0.10 kg kg−1 and minimum UC strength of < 25 kPa at wetnesses of 0.14 kg kg−1 or more. Between these two critical moisture contents, strength varied inversely with wetness. A pan formed in post‐glacial colluvial deposits showed similar maximum UC strength values but still retained about 70% of its UC strength at the wet moisture condition. The UC testing data enabled separation of the fragipans developed in the glacial till from indurated horizons formed in the colluvial material. Pocket and Proctor penetrometers were investigated to determine their suitability for routine recognition of fragipan horizons in the field, especially during wet soil conditions. Their application did not improve upon current field techniques.

Fragipan formation in argillic brown earths (Fragiudalfs) of the Milfield Plain, north‐east England. I. Evidence for a periglacial stage of development

“…Strong depletion and preferential loss of all forms of extractable iron and manganese relative to aluminium in the greyish zones, with enrichment in adjacent narrow reddish borders (Table 2), indicates a redox related process. This micromorphological and chemical evidence supports the process of development proposed in several American fragipan studies (Gile, 1958;Miller et al, 1971;Pickering & Veneman, 1984) involving lateral diffusion of manganous and ferrous ions mobilized during periods of localized waterlogging in polygonal zones. The process has affected both fissure infill and fissure walls so that the width of the grey zones (up to 2cm) is considerably greater than that of the infilled fissures (0.5 cm or less).…”

“…Most North American authors reject the permafrost hypothesis and favour development in a temperate environment. Compaction has been variously attributed to contraction under slight overburden pressures; rearrangement of soil constituents on wetting and drying; additions of illuvial material along contraction fissures; pressures generated by tree roots; or inheritance from till fabrics (Soil Survey Staff, 1975;Pickering & Veneman, 1984;Bryant, 1989). Several studies support the clay bridge hypothesis to explain brittleness when moist (Miller et al, 1971;Wang et al, 1974;Lindbo & Veneman, 1989).…”

Weed Responses to Soil Compaction and Crop Management

“…In other experiment years, the highest values of soil bulk density were caused from low soil moisture content (110 g kg -1 ) and the lowest soil bulk density values occurred in 2001 and 2004 when high soil moisture content (210 g kg -1 ) was present at compaction application. In experiments of Pickering and Veneman (1984), soil dry density increased to the soil moisture content 0.11-0.12 kg kg -1 and started to decrease at higher moisture contents.…”

A Proposed Pan Layer Classification for Soils of Suez Canal Area, Egypt

“…lost 79% of its hardness. The mechanism of soil strength reduction with increasing wetness is explained by Pickering and Veneman (1984). They reported that the partial dissolution of the bonding agent between peds and particles, and the reduction of interparticulate friction by films of moisture that import as a lubricant effect.…”