Granular materials usually copossess inherent and stress-induced anisotropy that significantly influences their mechanical behaviors. This paper presents a series of true-triaxial tests on aeolian sands to consider the inherent and stress-induced anisotropy in terms of soil deposition angles and intermediate principal stress coefficients, respectively. These results show that the deposition angle primarily affected the elastic-plastic stage under axisymmetric conditions. Otherwise, the deposition angle affects all deformation processes after the elastic stage when the intermediate principal stress coefficient changes. Moreover, the critical state is not unique but depends on the combined effect of the deposition angle and the intermediate principal stress coefficient, which indicates that the strength, stress-strain response, and dilatancy behavior of sands are affected by both inherent and stress-induced anisotropy.
This study investigates the effects of incorporating date palm wood powder (DPWP) on the thermal, physical, and mechanical properties of lightweight fired earth bricks made from clay and dune sand. DPWP was added in varying proportions (0 %, 5 %, 8 %, 10 %, 12 %, and 15 % by weight of the soil matrix) to evaluate its influence on brick performance, particularly in terms of thermal insulation. Experimental results revealed that adding DPWP significantly reduced the thermal conductivity of the bricks, achieving a maximum reduction of 56.41 %. However, the inclusion of DPWP negatively impacted the physical and mechanical properties of the samples. Among the tested bricks, those with 8 % and 10 % DPWP achieved a desirable balance, maintaining satisfactory mechanical strength within acceptable standards while achieving thermal conductivity values of 0.333 and 0.279 W/m & sdot;K, representing reductions of 37.29 % and 47.46 %, respectively. To further validate these findings, prototypes of the DPWP-enhanced fired bricks and commercial bricks were constructed and tested under real environmental conditions during both summer and winter seasons, over a continuous 12-h daily period. The DPWP-enhanced prototypes demonstrated superior thermal performance, with temperature differences reaching up to 3 degrees C compared to the commercial bricks. These findings highlight the potential of DPWP as a sustainable additive for improving the thermal insulation properties of fired earth bricks, thereby promoting eco-friendly and energy-efficient building materials for sustainable construction practices.
This work aims to isolate and screen the fungicidal endophytic bacterial strains for biocontrol efficacy against Phytophthora palmivora, a soil-borne pathogenic fungus that kills durian trees worldwide. Among more than 100 isolates, 6 strains were screened as potential fungicidal strains with inhibitory efficiency of 67.4-79.8%. Based on 16S rRNA gene sequencing and phylogenetic analysis, these strains were identified as Bacillus amyloliquefaciens EB.CK9, Bacillus methylotrophicus EB.EH34, Bacillus amyloliquefaciens EB.EH18, Bacillus siamensis EB.KN10, Bacillus velezensis EB.KN15 and Paenibacillus polymyxa EB.KN35. In greenhouse tests, the two strains P. polymyxa EB.KN35 and B. velezensis EB.KN15 significantly reduced the damage to diseased roots by P. palmivora (33.3 and 35.6%, respectively), increased the rate of survival of durian trees (only 20.8 and 22.9% plant death, respectively), and showed a positive effect on promoting durian plant growth. Notably, the potential fungicidal effect of last two strains against P. palmivora was recorded for the first time in this work. HPLC analysis showed that these strains can secret several plant growth-promoting compounds, including gibberellic acid (GA3), indole-3-acetic acid (IAA), kinetin, and zeatin. Of these, GA3 and zeatin were produced with a significant amount by both strains. The volatiles bio-synthesized by these isolates were also identified using GC-MS analysis, and some major volatiles were found as fungicidal agents. This study suggested that P. polymyxa EB.KN35 and B. velezensis EB.KN15 may be potential biocontrol candidates for durian P. palmivora and bio-fertilizers for the sustainable production of durian crops.
True triaxial tests were conducted on artificially frozen sand. The effects of the intermediate principal stress coefficient, temperature and confining pressure on the strength of frozen sand were studied. The stress-strain curves under different initial conditions indicated a strain hardening. In response to increases of either the intermediate principal stress coefficient or the confining pressure or to a decrease of temperature, the strength typically increased. Furthermore, a new strength criterion was proposed to describe the strength of artificially frozen sand under a constant b-value stress path, combining the strength function in the p-q and pi planes. Considering the low confining pressure, the strength criterion in the p-q plane fitted the linear relationship in the parabolic strength criterion well. The strength criterion in the pi plane was combined with stress invariants, and a new strength criterion was established. This criterion considers unequal tension and compression strength, and integrates temperature. Test results indicated its validity. All parameters of the strength criterion could be easily determined from the triaxial compression and triaxial tensile tests.
Paleoliquefaction investigations are crucial for assessing seismic hazard potential and identifying regions susceptible to liquefaction, which is essential for seismic risk-sensitive land-use planning. This research aimed to identify paleoliquefaction sites by reviewing documented descriptions of the damages and ground deformations in Bangladesh during three significant historical earthquakes: the Bengal Earthquake (1885), the Great Assam Earthquake (1897), and the Srimangal Earthquake (1918). A paleoliquefaction map for Bangladesh was generated, locating the paleoliquefaction sites during these three major historical earthquakes. In addition, Standard Penetration Test (SPT) blow count and Down-hole Seismic Tests (DST) were conducted at selected locations to assess the Liquefaction Potential Index (LPI) by using deterministic (simplified) and probabilistic procedures. The results confirmed a high likelihood of liquefaction during future large-magnitude earthquakes. The research outcome will help to distinguish and characterize Bangladesh's susceptible regions to soil liquefaction during potential earthquakes in the future and is recommended for consideration in large-scale construction or development plans.
Stress release of the surrounding soil is the fundamental reason for many accidents in tunnel engineering. There have been a great number of numerical simulations and analytical solutions that study the tunneling-induced ground stress. This paper conducts a series of physical model tests to measure the stress state evolution of the surrounding soil during the tunnel advancing process. The ground compactness, as the most critical factor that determines the mechanical properties of sand, is the control variable in different groups of tests. The measurement results show that at the tunnel crown, the minor principal stress sigma 3, which is along the vertical direction, decreases to 0 kPa when the relative density (Dr) of the ground is 35% or 55%. Therefore, we can deduce that the sand above the crown collapses. When Dr = 80%, sigma 3 does not reach 0 kPa but its variation gradient is very fast. At the shoulder, the direction angles of three principal stresses are calculated to confirm the existence of the principal stress rotation during tunnel excavation. As the ground becomes denser, the degree of the principal stress rotation gradually decreases. According to the limited variation of the normal stress components and short stress paths at the springline, the loosened region is found to be concentrated near the excavation section, especially in dense ground. As a result, different measures should be taken to deal with the tunnel excavation problem in the ground with different compactness.
Local ecological materials in construction represent a fundamental step toward creating living environments that combine environmental sustainability, energy efficiency, and occupant comfort. It is part of an organizational context that encourages the adoption of these methods and processes. This study aims to improve the use of locally available materials, particularly soil and agricultural residues, in the Errachidia region (southeastern Morocco). In particular, date palm waste fiber, a widely available agrarian by-product, was incorporated into the soil to develop six different types of stabilized earth bricks with fiber contents of 0 %, 1 %, 2 %, 3 %, 4 %, and 5 %. The aim was to evaluate their thermophysical, mechanical, and capillary water absorption properties. Thermal properties were determined using the highly insulated house method (PHYWE), a specific methodology for assessing thermal properties in a controlled, highly insulated environment. In addition, mechanical measurements were carried out to assess compressive and flexural strength. The results obtained showed that the addition of date palm waste fibers to brick based on soil improves the thermal resistance of the bricks. Flexural and compressive strength increased up to 3 % of fiber content, while a reduction was observed above this value. The 3 % fiber content is optimal for the stabilization of brick based on soil. Then, the increase of fiber content in bricks resulted in an increase in water absorption with a decrease in the density of the bricks. Physical and chemical characterization (XRD, FTIR, SEM, and EDX) of the soil and date palm waste fibers was carried out with geotechnical soil tests. The results obtained showed that the soil studied satisfies the minimum requirements for the production of bricks stabilized by fibers. These bricks can be considered an alternative to conventional bricks in ecological construction.
The remediation and management of old municipal solid waste (MSW) landfills are pivotal for advancing urban ecological sustainability. This study aims to systematically assess the mechanical properties, environmental behaviors, and synergistic mechanisms of remediated landfill-mined soil-like material (SLM) through advanced oxidation and stabilization processes. The results indicate that synergistic remediation with advanced oxidation and stabilization processes significantly increased the mechanical strength of stabilized SLM to over 0.6 MPa, and reduced the organic content by about 20 %, making it suitable for reuse in geotechnical engineering. The choice of oxidizing agents markedly affected the mechanical properties of stabilized SLM; for example, the application of sodium percarbonate in conjunction with stabilized materials further enhances the strength by simultaneously promoting the pozzolanic reaction. Furthermore, the heavy metal leaching behaviors of the stabilized SLM were found to be environmentally safe. The enhanced performance of stabilized SLM is primarily attributed to the synergistic effects of oxidation and pozzolanic reactions. The advanced oxidation process decreases organic matter content and increases its stability by reducing the proportion of readily decomposable O-alkyl C. Concurrently, pozzolanic reactions produce ettringite crystals and C-(A)-S-H gels, which not only fill micropores and improve particle bonding but also aid in heavy metal immobilization through surface adsorption, complexation, and physical encapsulation. These insights provide a comprehensive understanding of the remediation processes and resource recovery potential of SLM from old MSW landfills.
Date palm trees, especially Alhayani, Barhi, and Majhool, have a rich history in Palestine. However, the waste produced by these trees, such as unripe dates, date pits, and palm fronds, is usually burned on farms, leading to environmental concerns, or collected inside the farms for long periods, which leads to the emergence of the red date palm weevil, which works to damage palm trees. These wastes are a significant source of excellent biomass that can be used in many applications such as energy production, livestock feed, fertilizer for soil, and wooden boards, and can even be used as insulating materials as they have an excellent insulation value up to 0.083 W/ m.K [1]. This study focuses on utilizing agricultural waste from date palm trees in Palestine by grinding and transforming it into wooden blocks or pellets for use in heating, bakery ovens, household wood stoves, and other applications. The effectiveness of these waste materials for use as excellent heat value resources has been demonstrated, especially when compared to other tree waste. The heating values that were measured for date kernel (17.127 MJ/kg), palm leaf (16.887 MJ/kg), and palm frond petiole (15.990 MJ/kg) indicate their promising potential for use in heating applications. A feasibility study was conducted for a production line that converts these waste materials into wooden blocks for use in heating applications. The annual profits were estimated at approximately 41000 $, with a payback period of around 2.4 years and a return-oninvestment rate of 36 %.
Numerous specimens stored in natural history collections have been involuntarily preserved together with their associated microbiomes. We propose exploiting century-old soils occasionally found on the roots of herbarium plants to assess the diversity of ancient soil microbial communities originally associated with these plants. We extracted total DNA and sequenced libraries produced from rhizospheric soils and roots of four plants preserved in herbaria for more than 120 years in order to characterise the preservation and taxonomic diversity that can be recovered in such contexts. Extracted DNA displayed typical features of ancient DNA, with cytosine deamination at the ends of fragments predominantly shorter than 50 bp. When compared to extant microbiomes, herbarium microbial communities clustered with soil communities and were distinct from communities from other environments. Herbarium communities also displayed biodiversity features and assembly rules typical of soil and plant-associated ones. Soil communities were richer than root-associated ones with which they shared most taxa. Regarding community turnover, we detected collection site, soil versus root and plant species effects. Eukaryotic taxa that displayed a higher abundance in roots were mostly plant pathogens that were not identified among soil-enriched ones. Conservation of these biodiversity features and assembly rules in herbarium-associated microbial communities indicates that herbarium-extracted DNA might reflect the composition of the original plant-associated microbial communities and that preservation in herbaria seemingly did not dramatically alter these characteristics. Using this approach, it should be possible to investigate historical soils and herbarium plant roots to explore the diversity and temporal dynamics of soil microbial communities.