Ana Heitor

A laboratory study on the shear behavior of mixtures of coal wash and steel furnace slag as potential structural fill

The accumulation of industrial waste materials (e.g., coal wash and steel furnace slag) has become a critical environmental problem in Australia in recent years. The possible re-use of these types of materials as structural fill for transport embankments and land reclamation is one of the preferred options from a waste management perspective. Consequently, an experimental testing program was undertaken using the triaxial apparatus to evaluate the shear behavior of compacted mixtures of coal wash (CW) and steel furnace slag (SFS). The effect of varying the confining pressure and the percentage of coal wash on the isotropic compression line, the stress-strain behavior, and particle degradation during drained shearing was evaluated. The percentage of coal wash was found to influence the shearing behavior of the CW-SFS mixtures. When the content of coal wash increased, the shear strength of the CW-SFS mixtures decreased and the axial strain corresponding to the peak stress ratio increased. Moreover, the incidence of particle breakage increased for those mixtures with a higher CW content due to the low particle strength of CW. This paper also provided a non-linear strength envelope and a corresponding empirical equation to capture the shear strength of CW-SFS mixtures.

Drained and Undrained Shear Behavior of Compacted Coal Wash

AbstractCoal wash is a granular waste material that is readily available in the vicinity of coal mining operations. While its potential use in structural fills has been recognized in the past, the effects of particle breakage on the geomechanical performance of the material have not been thoroughly investigated. In this paper, an experimental study on a selected coal wash is undertaken to characterize the influence of compaction and particle breakage on its corresponding stress-strain behavior. Particular emphasis is given to the role of compaction energy level and associated breakage incurred during compaction on the drained and undrained shearing behavior. The incidence of particle breakage for undrained and drained shearing was observed to be different, which in turn had a strong influence in the yielding behavior and the critical state. Furthermore, the critical state conditions for coal wash seem to be better described through a three-dimensional surface incorporating the effect of breakage.

Field Investigation on Compaction and Strength Performance of Two Coal Wash-BOS Slag Mixtures

The effective reuse and recycling of industrial byproducts, namely coal wash (CW) and Basic Oxygen Steel slag (BOS), through large-scale geotechnical projects (e.g. land and port reclamation) is economically beneficial and environmentally sustainable. Nevertheless, due to the heterogeneity of these granular waste materials, the actual performance of compacted fill in the field can be significantly different from that observed in the laboratory. This paper reports the results of a compaction field trial carried out at Port Kembla Outer Harbor reclamation site (Wollongong, Australia) to evaluate the in-situ performance of two selected CW-BOS blends. Based on a number of field density tests, it was found that 4 passes of compaction were adequate for achieving a fill density > 90% standard Proctor compaction. A series of dynamic cone penetration tests (DCPTs) confirmed that compacted CW-BOS fills have a greater strength compared to compacted sandy fill, as the number of blows to penetrate 100 mm is greater than 20 for both materials. Furthermore, plate load tests were also performed and swelling was routinely monitored. The results are presented and discussed.

Aspects related to the small strain shear modulus behaviour of compacted soils subjected to wetting and drying

The dynamic properties of a soil are routinely investigated to describe its engineering behavior under repeated loading. Although the effect of suction on the dynamic response of soils is significant, there have been limited studies in which the post-compacted changes in suction induced by wetting and drying cycles have been considered. In this paper, aspects related to the dynamic properties with special reference to the small strain shear modulus of compacted soils subjected to wetting and drying are described. Further evidence on the dynamic response in terms of small strain shear modulus (G0) of a compacted soil subjected to wettingdrying is presented and novel insights into small strain behavior in multiple cycles of wetting and drying are shown. Particular emphasis is placed on the hysteric behavior and its dependence on the suction history. The results not only confirm the importance of the current suction ratio (or CSR), but also suggest that subsequent wetting-drying cycles further induce hysteretic changes in relation to the small strain shear modulus, particularly when following the wetting paths.

Performance of Rubber Tire-Confined Capping Layer under Cyclic Loading for Railroad Conditions

AbstractThe need for long-term performance of rail infrastructure has now become imperative because heavy-haul railways are expected to withstand higher speeds and heavier axle loads, especially fo...

Evaluating the Properties of Mixtures of Steel Furnace Slag, Coal Wash, and Rubber Crumbs Used as Subballast

AbstractSteel furnace slag (SFS) and coal wash (CW) are two common by-products from the coal-mining and steel industries in Australia. Rubber crumbs (RC) is a material derived from waste tires cont...

Effect of Rubber Crumbs on the Cyclic Behavior of Steel Furnace Slag and Coal Wash Mixtures

AbstractThe practical application of waste materials such as steel furnace slag (SFS) and coal wash (CW) is becoming more prevalent in many geotechnical projects. While adding rubber crumbs (RCs) f...

Use of the soil modulus for compaction control of compacted soils

Insufficient compaction conditions can cause significant roadway infrastructure maintenance costs. Conventional compaction control, using nuclear methods, is based on the discrete in situ determination of the dry density and moisture content. Recently, there has been an increase interest in alternative methods for compaction control using intelligent compaction technologies. This method enables the continuous measurement of the soil modulus and the degree of compaction on the layer that is being compacted. Thus, the efficiency of the compaction process can be maximized. Although the adoption of this method is very promising, it constitutes a change of project specification for the contractors (i.e. use of the soil modulus instead of the dry unit weight). Furthermore, the role of dry unit weight, moisture content and matric suction on the soil modulus is still not well understood. This paper presents a review study of the effect of soil types, prepared under standard the same Proctor compaction energy, on the small-strain shear modulus. The results suggest that there seems to be a close relationship between the fines content and small strain shear modulus on the dry side of the optimum, whereas, its effect seems less evident on the wet side of the optimum.

Influence of Particle Gradation and Shape on the Performance of Stone Columns in Soft Clay

A stone column typically consists of particles whose influence has largely been overlooked in design practice in terms of stress transfer, pattern of deformation, and intrusion of fines (clogging). This article presents an experimental study on the load-deformation behavior of a model stone column installed in soft clay with a particular emphasis on the influence of particle gradation and shape under undrained loading. The results show that particle gradation and shape have a significant influence on the load-deformation behavior and the extent of fines intrusion into the stone columns. Relatively well-graded particle sizes favor the development of higher peak shear stresses accompanied by lateral bulging, whereas more uniform grading results in the development of distinct shear planes and smaller peak shear stresses. Deformed columns were also examined using computed tomography, and the porosity profiles at the end of the test were determined using micrographs. Maximum porosity typically occurred in the zone of extreme lateral deformation, with the results suggesting that the extent of fines intrusion was influenced by particle morphology.