Constitutive models for peat - a review

This paper presents a review of the main constitutive models for peat and other highly organic soils having extremely high water content. At present, predictions of the geomechanical behaviour of such soils for design practice are mostly based on constitutive theories developed for fine-grained mineral soils. Concepts of primary consolidation and secondary compression as applied to peat are explained using the two-level structure assumption of micropores and macropores [1]. As background, the historical development of consolidation hypotheses A&B [24] regarding the concepts of primary consolidation and secondary compression is reviewed for both mineral and organic soils. Based on microscopic examinations and in-situ testing, it is generally accepted that hypothesis B is more suitable for peat. The micro-mechanical rheological model proposed by Berry and Poskitt [2] and the isotache-compression model developed by den Haan [6] were reported to have good agreement with experimental laboratory results for fibrous and amorphous peats. Attention is given to the structural anisotropy of peat material, inherent by its fibrous nature, in these constitutive frameworks

Discussion of “Reclaimed Lignin-Stabilized Silty Soil: Undrained Shear Strength, Atterberg Limits, and Microstructure Characteristics” by T. Zhang, G. Cai and S. Li

The discussers read with interest the recent paper by Zhang et al. (2018), which reports on the investigation of the effects of 0–12% lignin additive on some index and shear strength properties of a silty soil material. The use of the fall-cone device to study undrained shear strength variation with moisture content is pleasing to see and shows how the approach is useful for this purpose: namely the study of undrained strength variation. We wish to make the following comments regarding some of the underlying assumptions in the paper by way of offering some other explanations and interpretations for the results obtained

The Unseen in the Modern Image World

The twentieth century is often characterized as an age of images. The majority of theories about technologies of vision in the twentieth century – photography, film, digital imagery – seize on the proliferation of visual stimuli and their desensitizing or liberating possibilities. In the always incomplete theorization of images, what we see and what sees us often defines and delimits us, but at the same time, we define and delimit what we see. The inherent limitations of vision that result from the capabilities of the visual mechanism and its technological extensions shape both individual perception and the broader realm of cultural vision. In an age dominated by the visible, the limits of vision either provide respite from the mass of images we are forced to perceive or they constrain how we construe the world visually. The Unseen in the Modern Image World reconsiders the complex and mutually constitutive relationship between visual perception and literary production in the twentieth century. This study resituates both literary and critical discourses on the boundaries of the perceptible in order to foreground the dependence of vision on its limits. I recontextualize the most formative theories of novelistic production of the century alongside theories about the dominance of vision in modernity in order to suggest that the constraints rather than the proliferations of visual perception shape modern prose. I elaborate the predominance of the unseen through its clashes with the limits of visuality: Martin Heidegger’s shadow through which modernity projects itself beyond the representational bounds of “the world picture,” and Walter Benjamin’s elaboration of the masses’ distracted visual reception, brought about by film, which he argues profoundly alters perception. I ground subsequent chapters by demonstrating that the boundaries of perception not only elude the presumed dominating grasp of “the world picture” but also reduce our visual apprehensions of the world to mere extractions from the infinitely vaster realm of the unseen, a terrain that the modern novel—from Joseph Conrad and Henry James through Don DeLillo—grounds itself upon

Stabilization of a highly expansive soil using waste-tire-derived aggregates and lime treatment

This study investigates the combined efficacy of waste-tire-derived aggregate (TDA) materials and hydrated lime on the compactability, compressive strength and swelling potential of a highly expansive soil from South Australia. A total of 21 mix-designs, covering a comprehensive range of soil–TDA–lime combinations, were examined through standard Proctor compaction, unconfined compressive strength (UCS) and oedometer swell tests. The mobilized UCS exhibited a ‘rise–fall’ behavior, peaking at 5% TDA content and subsequently decreasing (monotonically) for higher inclusions of TDA. Increasing the TDA mean particle size (from 1.67 to 3.34 mm) also contributed positively to the UCS development. Addition of TDA to the soil/soil–lime-blends produced notable reductions in the swelling potential; the reduction was primarily governed by higher TDA contents, and, to a lesser degree, for larger TDA mean particle sizes. However, the role of TDA particle size in reducing swelling was found to be more significant than that of enhancing the UCS. As expected, lime treatment of the soil–TDA blends provided major further improvements to the UCS and swelling potential reduction; the achieved UCS improvements being positively proportional to the lime content and curing time. In view of the experimental results, soil–lime blends containing TDA to soil–lime mass ratios of up to 10% (preferably employing coarse-sand-sized equivalent TDA) can be deemed as suitable choices (capable of adequately mitigating the swelling potential, while simultaneously enhancing the UCS). © 2022 The Author

An objective framework for determination of the air-entry value from the soil–water characteristic curve

The air-entry value (AEV) suction, marking the transition between saturated and unsaturated soil mechanics, is arguably the most important parameter interpreted from the soil–water characteristic curve (SWCC); its accurate determination being essential for the prediction of unsaturated soil properties. The AEV is commonly obtained by a subjective and time-consuming graphical construction. This micro-article proposes an objective framework, developed based on a practical mathematical translation technique, for the AEV determination. Explicit equations for the AEV are derived based on eleven well-established SWCC fitting functions, covering a wide range of functional complexities. In addition to its objective nature (providing unique interpretations of the AEV), the proposed framework complements numerical implementations of unsaturated soil constitutive models. © 2021 The Author(s