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Biomasses are organic materials that are derived from any living or recently-living structure. Plenty of biomasses are produced nationwide. Biomasses are mostly combusted and usually discarded or disposed of without treatment as biomass ashes, which include wood and sugarcane bagasse ashes. Thus, recycling or treatment of biomass ashes leads to utilizing the natural materials as an economical and environmental alternative. This study is intended to provide an environmental solution for uncontrolled disposal of biomass ashes by way of recycling the biomass ash and replacing the soils in geotechnical engineering projects. Therefore, in this study, characteristic tests of wood and sugarcane bagasse ashes that are considered the most common biomass ashes are conducted. The test of chemical compositions of biomass ashes is conducted using energy dispersive X-ray spectroscopy (EDS), and Scanning Electron Microscope (SEM), and heavy metal analysis is also conducted. Engineering behaviors including hydraulic conductivity, constrained modulus and shear modulus are examined. Also, coal fly ash Class C is used in this study for comparison with biomass ashes, and Ottawa 20/30 sands containing biomass ashes are examined to identify the soil replacement effect of biomass ashes. The results show that the particle sizes of biomass ashes are halfway between coal fly ash Class C and Ottawa 20/30 sand, and biomass ashes consist of a heterogeneous mixture of different particle sizes and shapes. Also, all heavy metal concentrations were found to be below the US Environmental Protection Agency (EPA) maximum limit. Hydraulic conductivity values of Ottawa 20/30 sand decrease significantly when replacing them with only 1%–2% of biomass ashes. While both the constrained modulus and shear modulus of biomass ashes are lower than Ottawa 20/30 sand, those of mixtures containing up to 10% biomass ashes are little affected by replacing the soils with biomass ashes.

This experimental investigation quantified the shear wave velocity (V s ) of granular packs composed of large grains mixed with small quantities of finer grains, up to the critical fines content (FC * ). Bender element tests were performed on 112 mixtures to quantify the variation of V s with fines content (FC), particle size ratio, and void ratio. When FC was less than FC * , the shear wave velocity decreased with increasing FC, due to the reduction in interparticle contacts between large grains. In addition, the observed reduction in packing stiffness was more apparent as the size difference between the two particles increased. Most notably, the results of this study demonstrated that V s of granular mixtures of two different silica particles with FC < FC * was best expressed in terms of intergranular void ratio when finer particles were treated as void space, as opposed to the global void ratio.

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In this study, a rainer system capable of forming a large homogeneous granular specimen is introduced. A series of laboratory tests is carried out in order to study the performance of the proposed system. The features of the rainer system used in this study are the adoption of a porous plate and the air-pluviation without changing the deposition intensity. Without a porous plate, the rainer induces an insignificant density increase with increasing drop height, providing a dense to very dense specimen. However, the rainer with a porous plate produces a medium dense to dense specimen, with a drastic density increase at drop heights of 10–40 cm and a progressively reduced rate of density increase at larger drop heights. It is shown that the density obtained by using a porous plate rainer with a 70 cm drop height is similar to that achieved by using a conventional rainer with a 10 cm drop height. It is concluded that the use of a conventional rainer that adopts a porous plate significantly widens the range of density achievable even without an alteration in the deposition intensity. It is also concluded that using the rainer with a porous plate significantly improves the vertical and horizontal homogeneities of the specimen. The relative density evaluated from the measured cone resistance appears to provide a reasonable estimation at depths of 40–80 cm. The profile of shear wave velocity measured using bender elements seems to accurately reflect the vertical non-uniformity of the specimen.