Radforth peat is a term introduced here to describe peats with a negligible content of mineral matter. The Sphagnum peat discussed in this paper consists mostly of fibrous particles such as stems, leaves, fiber hairs, etc. Outstanding characteristics of Radforth peats are their extremely high compressibility and high rate of creep. The variability of peat is often almost unpredictable, even within an apparently uniform deposit. Predictions of magnitude and rate of settlement are therefore difficult. Frequent disturbed sampling and classification combined with empirical relationships may give better results than infrequent undisturbed sampling, consolidation testing, and theoretical relationships. Peat fibers affect the geotechnical behavior of peat by providing an internal lateral resistance to shear deformations in the triaxial mode of shear. Since pore pressures reduce this resistance, loading under drained conditions will provide better stability through higher lateral resistance. The shear strength of peat in ring shear would be virtually unaffected by fiber reinforcement. The behavior of the Escuminac peat in ring shear was surprisingly consistent and gave parameters of c = 2.4 kPa and φ = 27 to 32 deg within a load range of 3 to 50 kPa. These values would be directly applicable in the case of retaining structures on peat, for which triaxial φ-values of 40 to 50 deg, as consistently reported in the literature, could in fact be misleading.

On reviewing the literature on peat classification, it becomes evident that most of the existing classification systems are based on the use of peats and organic soils as a growing medium in horticulture, agriculture, and forestry, or as a horticultural additive (peat moss), or as a fuel. One exception is the Radforth classification system for peat, which does pertain to engineering applications. Since this system is not based on geotechnical properties, however, it is not in itself sufficient for geotechnical classification. The term peat as used today also includes a vast range of organic soils: from jelly-like, almost liquid muds whose organic content may not even originate from peat, to extremely coarse-fibrous meshes of woody remnants and fibers. The mud is often referred to as an amorphous-granular peat and the woody mesh as a fibrous peat. These are the only two terms that have been generally adopted by geotechnical engineers, with the inevitable results that each term covers a large range of materials and that considerable overlapping occurs. An attempt is made in this paper to distinguish between various peats and organic soils on the basis of geotechnical engineering considerations. The existing von Post and Radforth systems are examined with respect to geotechnical applications. These systems are supplemented with routine geotechnical tests yielding numerical values for classification purposes.

Geotechnical investigations of waste fills are rarely undertaken, and consequently far too little is known by the geotechnical community about the engineering properties of fill, particularly waste fill such as refuse and woodwaste. In many communities waste fills are being used to create recreational areas to elevations significantly above the original terrain. Slope stability then becomes an important consideration. In addition many communities have expanded to encompass waste fill areas once thought to be beyond the limits of development. The engineering properties and long-term behaviour of these fill areas are therefore important to land use considerations. In 1983 the authors initiated a programme of investigations of the geotechnical properties of waste materials. Particular emphasis was placed on refuse landfills and woodwastes such as barkfill (hogfuel), sludge and ash wastes. Novel equipment and methods had to be introduced both in the field and in the laboratory. The field investigations were carried out in waste fills across Canada. Much of this work had to be concerned with the development of suitable equipment and test procedures. It is concluded that geotechnical investigations of these unusual and difficult materials are feasible, as long as it is recognized that conventional testing methods and analyses may not apply and that a different approach is required. No direct evidence was found that the shear strength of refuse changes with the degree of decomposition.

The closing of landfills has become commonplace. In many instances these closed facilities are desirable building sites because of close proximity to urban areas. Much of the subsurface investigation for foundation design parameters in landfills is more difficult and more expensive than for conventional sites underlain by soil or rock. A subsurface investigation of one particular landfill site is presented and discussed. The results obtained guide the decision making process for both further investigation and foundation type selection. The purpose of the paper is to inform the practicing engineer of one approach to the evaluation of geotechnical considerations of a landfill site.

Two samples developed at the University of New Brunswick for sampling of peat are described. One is a 100-mm-diameter piston sampler with a Plexiglas insert sample holder and the other is a 250-mm-square block sampler. The samplers have been extensively tested and used in Sphagnum and sedge peat and have also been used successfully in soft-to-almost-fluid organic diatomaceous soils.