To address the issues of high porosity and low strength in calcium sand of artificial islands, this study focuses on improving the calcium sand's mechanical properties. The effects of WER curing methods and coconut fiber modification on the UCS and microscopic mechanisms of calcium sand are investigated. The results indicate that both fiber incorporation and the increase in WER ratio can enhance the unconfined compressive strength of calcareous sand, with the addition of a certain amount of coconut coir fiber showing a more significant strength increase. The optimal recommended dosage of WER is 15%, which results in an UCS of 1218 kPa, an increase of nearly 4.27 times compared to 9% WER dosage. Coconut coir fiber has good tensile strength that can improve the compressive strength of calcareous sand after curing. The UCS of calcareous sand cured with a fiber content of 0.3% to 0.5% is increased by 1247 kPa to 1792 kPa compared to cured soil with no fiber. The strong binding nature of WER addresses the issue of large porosity in calcareous sand. Together with the penetrating coconut coir fibers, it forms a three-dimensional reticular framework structure, thereby enhancing the compressive performance of the calcareous sand-cured soil mass.

Two common waste by-products in Thailand, rice husk ash (RHA) and coir fiber (CF), were used alongside lime (L) to stabilize laterite soil and create a sustainable subbase material for pavements. The mechanical properties of the laterite soil mixed with RHA, lime, and CF were evaluated through compaction characteristics, unconfined compressive strength (UCS), California bearing ratio (CBR), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analyses. The dry soil mass was replaced with 10% and 20% RHA, and CF was added at 0.5%, 1%, and 1.5%. Additionally, based on the initial consumption of lime (ICL) test, 8% lime was incorporated into the mixture. The samples were cured for 7 days (short-term) and 56 days (long-term) before undergoing various tests. In terms of compaction, results showed that increasing the content of RHA, CF, and lime led to a decrease in maximum dry unit weight and an increase in optimum moisture content. The 10RHA8L and 20RHA8L mix designs demonstrated the highest UCS and CBR values after 56 and 7 days of curing, respectively. EDX analysis revealed the formation of calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) gels on the particle surfaces, leading to a denser and more cohesive structure. Based on these findings, the mixture containing 20% RHA and 8% lime exhibited the most favorable properties for use as a subbase material in road and embankment construction.

Thailand is situated in the heart of Southeast Asia and is classified as having a tropical climate with high rainfall frequency and occurrence of floods. The weakening effect of water on laterite soil has led to different road damages such as potholes. Under these adverse environmental conditions, heavy traffic could also result in the formation of cracks and poor performance of roads. This study investigates the effects of Rice Husk Ash (RHA), Lime (L), and Coir Fiber (CF) as soil reinforcement material on the engineering properties of laterite soil. Several tests were conducted including the Unconfined Compressive Strength (UCS) test, three-point bending flexural strength, direct shear test, completely soaked durability test (to mimic flood conditions), X-ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM) to observe the micro-structural changes of stabilized soil. The laterite soil was replaced by 10%, and 20% of RHA, 1% of CF, and 8% of L. The samples were cured for 7, 28, and 56 days before conducting the tests. The 20RHA8L mix designs showed the highest UCS value after 56 days curing period. In terms of the durability test results, the 20RHA8L mix design also exhibited the lowest reduction in compressive strength (3.8% drop) after undergoing 6 wetting-drying cycles. According to flexural strength, the 20RHA1CF8L (20%RHA, 1%CF, 8%L) mix design indicated a tenfold increase in flexural strength compared to the natural laterite soil after 28 days of curing. Based on the findings of this research, CF and RHA are beneficial for earth structures such as embankments and road layers that are subjected to significant tensile stresses. These waste materials can also reduce the brittleness of lime-stabilized soil.

In tropical regions, heavy rainfall induces erosion and shallow landslides on road embankments. Cement-based stabilization methods, common in these regions, contribute to climate change due to their high carbon footprint. This study explored the potential application of coir fiber-reinforced laterite soil-bottom ash mixtures as embankment materials in the tropics. The objective is to enhance engineered embankment slopes' erosion resistance and stability while offering reuse options for industrial byproducts. This study examined various mix designs for unconfined compressive strength (UCS) and permeability, utilizing 30% bottom ash (BA) and 1% coir fiber (CF) with varying sizes ranging from 10 to 40 mm, 6% lime, and laterite soil (LS), followed by microstructural analyses. The results demonstrate that the compressive strength increases as the CF length increases to 25 mm. In contrast, permeability increases continuously with increasing CF length. Lime-treated mixtures exhibit superior short- and long-term strength and reduce permeability owing to the formation of cementitious materials, as confirmed by microstructural analyses. A lab-scale slope box was constructed to evaluate the surface erosion of the stabilized laterite soil embankment. Based on the rainfall simulation results, the LS-BA-CF mixtures show better resistance to erosion and deformation compared to untreated LS, especially when lime is added to the top layer. This study provides insights into a sustainable and cost-effective approach for slope stabilization using BA and CF, offering a promising solution for tropical regions susceptible to surface erosion and landslides.

Geotextiles are widely being used for different soil engineering applications such as filtration, separation, drainage, reinforcement and erosion control. Synthetic geotextiles are mainly produced from the petroleum-derived polymeric materials. The environmental awareness and concern towards sustainability necessitated the application of a more sustainable alternative with natural fibre-based geosynthetics. In this paper, the physical and mechanical properties of five different natural fibres, namely abaca, coir, jute, pineapple and sisal fibres, which could be a suitable candidate for geotextile applications have been analysed and compared. Out of the five different types of the fibres analysed in the present study, the highest average diameter, density and flexural rigidity were found to be for coir and the lowest were found to be for pineapple. It was observed that all the five types of the fibres have the potential for soil reinforcement applications. The unconfined compressive strength of the unreinforced clay was increased by 2, 3.3, 4. 4.1 and 5 times, when reinforced with abaca, coir, pineapple, sisal and jute fibres, respectively. However, jute fibres have low rigidity. The present study concluded that these natural fibres can perform effectively as a raw material for geotextiles. Pineapple fibre absorbs high amount of water and hence may degrade faster comparing to other natural fibres. The fibres which contain high proportion of cellulose possess high tensile strength. For coir fibres, due to the presence of high amount of lignin the life is comparatively high. Thus, blending of the fibres in suitable proportions can complement each other and can lead to the production of better geotextile materials in various applications. Considering the durability, strength and compatibility in blending and spinning, an attempt was made in the present study to develop woven geotextiles from 50% coir:50% sisal blended yarns which are found to be superior in functional characteristics.

Micaceous weathered granitic soil (MWGS) is prevalent in the tropical regions of southern China, characterized by high compressibility, low compactability, and inadequate strength properties due to the presence of mica. Stabilization is crucial for transforming MWGS into a sustainable construction material for geotechnical engineering. This study focuses on enhancing the mechanical properties of MWGS by using coir fibers and fly ash, both locally available agricultural and industrial byproducts. Unconfined compression tests and consolidated drained triaxial compression tests were conducted on fiber-reinforced and fly-ash-treated MWGS under different stabilization conditions, considering the effects of fiber content, fly-ash content, and curing age. Scanning electron microscopy and energy-dispersive spectroscopy were also used to trace the microstructural evolution of the soil fabric in response to fiber reinforcement and fly-ash treatment. The experimental results indicate that higher fly ash content and longer curing give significantly improved soil strength and stiffness but poorer ductility. Incorporating coir fibers into the cemented soil matrix not only enhances the composite's strength, stiffness, and toughness but also shifts the shear response from brittle to ductile. For example, the compressive strength of MWGS could be improved by 49.1% with the inclusion of 1% content of coir fiber. Under the optimal dosage of fiber and fly ash, the soil compressive strength increased significantly from 114 kPa to 725 kPa. Microstructural analysis reveals that the bonding, friction, and interlocking among fibers, hydration products, and soil particles are the main contributors to the stable and strong microstructure and consequently the enhanced mechanical behavior of MWGS. This study provides an innovative and effective method for utilizing waste byproducts in stabilizing MWGS for practical geotechnical engineering applications.

Pervious concrete is a special type of concrete with high porosity but with limited structural strength. Geogrid reinforced pervious concrete is a specialized type of pervious concrete that incorporates geogrids for added structural performance. The composite material benefits from the geogrid's tensile strength and load-spreading capability with the addition of geogrids. Present study aims at investigating the mechanical, shrinkage and clogging characteristics of Styrene Butadiene Rubber (SBR) modified pervious concrete reinforced with glass fiber mesh, HDPE mesh, fiber glass geogrid, HDPE geogrid and coir geogrid. SBR modification is done from 0% to 15% by weight of cement The results show a palpable improvement in flexural strength of pervious concrete. HDPE geogrid provides almost the double flexural strength as non-reinforced pervious concrete. SBR modification of pervious concrete also enhanced the mechanical properties. Each grid/mesh has its own optimum dosage of SBR for maximum flexural strength. Laying geogrids can reduce the drying shrinkage of pervious concrete. The relative contact area of grid/mesh with the cement paste is a critical factor in reducing drying shrinkage. However, geogrid can lead to clogging in pervious concrete. Soil particles get accumulated in the void spaces and thereby reduce its permeability. Coir geogrid traps a larger quantity of soil particles impairing the permeability. Functional regression modelling by Functional Data Analysis approach is used to analyse the relationship between various grids and meshes with the properties of pervious concrete. The p-value and derivative plots gives better insight into the factorial effects.

Earthquake is one of the most critical hazard that damage buildings all over the world. Earthquake can result in ground shaking, soil liquefaction, damages, or even leads to complete collapse of buildings. So, buildings must be built to withstand the effect of earthquake so as to secure living conditions. Isolation method emerged as one of the efficient techniques for reducing the severe effects of earthquake. This project proposes a promising seismic isolation method by analysing different isolation method. A variety of isolation materials are available in order to reduce the seismic impact on buildings. This study investigated the efficiency of isolation materials such as polyurethane (PU) foam, coir fibre polyester composite, and geomembrane on seismic effect. In order to study the effectiveness of different isolation materials, seismic responses such as maximum roof acceleration, storey displacement, drift, and base shear of G+4 building was analysed using linear analysis by ANSYS software. Thus, this work aimed to propose the best suitable position of the most effective isolation material that reduces the seismic energy transferred. On other hand the use of this isolation method can provide an economic way to reduce the seismic energy transferred.