Numerical parametric study on behavior of bearing reinforcement earth walls with different backfill material properties

This paper presents a numerical parametric study on behavior of bearing reinforcement earth (BRE) walls with different backfill properties using the finite-element method software PLAXIS 2D. The primary objective of this study was to improve the understanding of bearing stress, settlement, lateral earth pressure, and horizontal wall movement of BRE walls with different backfill materials. The second objective of this study was to evaluate the effects of various soil–structure interactions, foundations, and stiffness of reinforcements on horizontal wall deformations. The backfill materials consisted of four types of soil, which were mixtures of silty clay and sand at different fine contents of 2, 20, 40, and 80% by dry weight. The model parameters for the numerical simulation were obtained from the conventional laboratory tests and back-calculated from the laboratory pullout tests of the bearing reinforcement. The geotextile elements were used to model the bearing reinforcements by converting the contribution of friction and bearing resistances to the equivalent friction resistance, which was represented by the soil–bearing reinforcement interaction ratio, Rinter. The values of Rinter decreased following a polynomial function as an increase of fine content in the ranges of 0.65–0.38 and 0.75–0.40 for the numbers of transverse members, n = 2 and 3, respectively. The simulated bearing stress in the reinforced zone decreased from the front to the back of the wall because the BRE wall behaved as a rigid body built on the relatively firm foundation retaining the unreinforced backfill. The foundation settlement decreased from the facing of the wall to the unreinforced zone for all backfill properties due to the slight rotation of the wall. The relationship between the maximum horizontal wall movement and the fine content can be expressed by a polynomial function. The maximum horizontal wall movement significantly increased as the fine content increased. The excessive movement was realized when the fine content was greater than 45%. The increase of the fine content moved the location of the maximum wall movement higher up from the mid to the top of the wall. A numerical parametric study was conducted to investigate the soil–structure interaction, foundation, and stiffness of reinforcement. These parameters affected the horizontal wall deformation, which is especially important for serviceability of BRE walls. The knowledge gained from this study provides a preliminary guideline in predicting the behavior of BRE walls and may be used to investigate other BRE walls with different wall heights and features of bearing reinforcements

Highly polymorphic microsatellite markers for the assessment of male reproductive skew and genetic variation in Critically Endangered crested macaques (Macaca nigra)

Genetic analyses based on non-invasively collected samples have become an important tool for evolutionary biology and conservation. Crested macaques (Macaca nigra), endemic to Sulawesi, Indonesia, are important for our understanding of primate evolution as Sulawesi macaques represent an exceptional example of primate adaptive radiation. Crested macaques are also Critically Endangered. However, to date we know very little about their genetics. The aim of our study was to find and validate microsatellite markers useful for evolutionary, conservation and other genetic studies on wild crested macaques. Using faecal samples of 176 wild macaques living in the Tangkoko Reserve, Sulawesi, we identified 12 polymorphic microsatellite loci through cross-species PCR amplification with later modification of some of these primers. We tested their suitability by investigating and exploring patterns of paternity, observed heterozygosity and evidence for inbreeding. We assigned paternity to 63 of 65 infants with high confidence. Among cases with solved paternity, we found no evidence of extra-group paternity and natal breeding. We found a relatively steep male reproductive skew B index of 0.330±0.267; mean±SD) and mean alpha paternity of 65% per year with large variation across groups and years (29-100%). Finally, we detected an excess in observed heterozygosity and no evidence of inbreeding across our three study groups, with an observed heterozygosity of 0.766±0.059 and expected heterozygosity of 0.708±0.059, and an inbreeding coefficient of -0.082±0.035. Our results indicate that the selected markers are useful for genetic studies on wild crested macaques, and possible also other Sulawesi and closely related macaques. They further suggest that the Tangkoko population of crested macaques is still genetically variable despite its small size, isolation and the species’ reproductive patterns. This gives us hope that other endangered primate species living in small, isolated populations may also retain a healthy gene pool, at least in the short term

A novel green construction material from water treatment sludge

A novel water treatment sludge-fly ash geopolymer is investigated in this research with the intention to develop an alternative green construction and building materials, without the usage of Portland cement as a cementing agent. Two waste by-products namely water treatment sludge and fly ash (FA) were used in this research. The liquid alkaline activator, L used was a mixture of sodium silicate solution (Na2SiO3) and sodium hydroxide solution (NaOH). This paper investigates the effect of liquid alkaline content and Na2SiO3/NaOH ratio on compressive strength of sludgefly ash geopolymer. The scanning electron microscopy (SEM) is undertaken to understand the role of of liquid alkaline content and Na2SiO3/NaOH ratio on strength development. Test results show that Na2SiO3/NaOH ratio of 80:20 and L/FA ratio of 1.3 are the optimum ingredient providing maximum unit weight and strength. The water treatment sludge traditionally destined for landfill can be used in a sustainable manner as alternative aggregate to develop geopolymer masonry unit

Strength Properties of Coffee Waste Based Geopolymers

2nd International Conference on Environmental Geotechnology,Recycled Waste Materials and Sustainable Engineering, EGRWSE 2019 -- 16 June 2019 through 20 June 2019 -- -- 248969A considerable amount of coffee waste is disposed in the landfills annually. This study aims to investigate the possible use of coffee waste based geopolymers as a green construction material for landfills. Coffee is an organic and a biodegradable material. In order to use coffee waste as a construction material, the strength development of a coffee-based geopolymer was observed. Fly ash or rice husk ash were used as a precursor. These precursors were preferred because they are silica and alumina rich materials. Alkaline activator formed of sodium silicate and sodium hydroxide (Na2SiO3–NaOH) was used to trigger the geopolymerization process. Three variables were tested, the ratio of Na2SiO3–NaOH; effect of ash type, and curing time on the strength development of coffee-based geopolymers. By adding 30% of ash into coffee waste, a geopolymer was synthesized with an activator/ash ratio of 1.7 and Na2SiO3–NaOH ratio of 90–10%, which provided the highest (up to 1000 kPa) unconfined compressive strengths. This paper denotes that the coffee based-geopolymerization products will further develop the organic material into a nondegradable material, therefore suggesting geopolymers as an option to stabilize highly organic soils. © 2021, Springer Nature Switzerland AG