In the surrounding rural region of Hawassa village houses are constructed by using soil, wood, teff straw, and water which is called chika in the local name, although its degradable materials prompt a shift to adobe brick for durability. Adobe brick, prevalent in rural locales, offers social, economic, and cultural advantages. However, its inherent flaws include brittleness, low compressive, and tensile strength, along with moisture sensitivity. This research aims to enhance the native soil attributes of Hawassa villagers by integrating sisal fiber for brick production. The investigation employed soil, water, and sisal fiber to create enhanced adobe bricks. A displacement controlled uniaxial testing machine was utilized to evaluate the compressive strength of the bricks. Findings indicated that a 0.9% sisal fiber inclusion achieved a maximum compressive strength of 13.44 MPa, outperforming conventional samples by 3.4 times, alongside a flexural strength of 0.097 MPa, exceeding conventional results by 3.34 times. The study includes a comparative analysis of mechanical properties and a cost evaluation between traditional and enhanced approaches.

In this research, a soil reinforcement approach was explored by introducing a polyvinyl acetate polymer treatment along with sisal fiber material, considering two mean particle sizes (D50 = 0.63 and 2.00 mm). The sand specimens were mixed with varying sisal fiber contents (Fs = 0 to 0.8%) and polyvinyl acetate polymer contents (PVAc = 6%, 9%, and 12%). A series of unconfined compression tests were performed to evaluate the compressive strength of the tested materials. The experimental findings indicate a positive correlation between the concentration of polyvinyl acetate polymer and the unconfined compressive strength within the tested range. The shear strength and of the sand initially increases with rising sisal fiber contents and then decreases with further increments in sisal fiber, peaking at a maximum value when the fiber content reaches a threshold of 0.6%. The findings validate the significance of the strain energy parameter as a reliable indicator for elucidating and forecasting the mechanical characteristics of soil reinforcement. New correlations have been developed to predict variations in unconfined compressive strength and peak strain energy based on the studied parameters (Fs, PVAc, and D50). The agreement between predicted and measured characteristics validates the effectiveness of these established relationships in accurately predicting UCS and strain energy factors.

In response to escalating environmental concerns, this study explored the use of sisal fiber as a sustainable alternative to traditional cement or synthetic fibers for soft soil stabilization. An optimal selection test was conducted to determine the optimal sisal fiber characteristics and their impact on the mechanical performance of cemented soil. The findings indicated that incorporating sisal fibers into cemented soil inhibits crack propagation, thereby enhancing its strength and ductility. A significant improvement was achieved by incorporating optimal fiber parameters (content = 0.4 %, length = 11 mm) into the cemented-soil, the compressive strength reached 4.4 MPa (by 29.4 %). In addition, to further improve the work performance of sisal fibercemented soil (SFCS), alkaline and acetylation treatments were applied, respectively, to prevent volume instability and degradation of sisal fiber. The study also evaluated the effects of these modification methods on the physical properties of sisal fiber and the strength of sisal fibercemented soil (SFCS). The results showed that a 6 % NaOH treatment was determined to be the most effective modification method, reducing the moisture affinity of sisal fiber, improving fiber-matrix bonding, and consequently enhancing the mechanical properties of SFCS (by 18.7 %). However, it should be noted that an excessively high concentration may adversely affect fiber properties, negatively impacting the strength of SFCS (by up to 11.59 %).

As one of the world's most fragile and sensitive ecological regions, Xizang risks significant environmental damage from using traditional materials, including cement and lime, to improve and reinforce loose accumulated sandy soil slopes. To address this issue, this study utilized a low-concentration biodegradable polyvinyl alcohol (PVA) solution combined with sisal fibers (SFs) to stabilize loose accumulated sand in southeastern Xizang. A series of physical, mechanical, and microscopic analyses was conducted to evaluate the properties of the treated sand. The results indicated the following. 1) The stress-strain curves of the improved samples exhibited an elastic-plastic relationship. Failure was observed in two stages. At a strain of 3% or less, the samples demonstrated elastic deformation with a linear increase in stress, whereas the deviator stress increased rapidly and linearly with an increase in axial strain. Once the strain exceeded 3%, the deformation became plastic with a nonlinear increase in the stress-strain relationship, and the growth rate of the deviator stress gradually decreased and leveled off. 2) Under varying confining pressure conditions, the relationship curve between the maximum (sigma 1-sigma 3)max similar to sigma 3 for both untreated loose accumulated sandy soil and soil improved with the PVA solution, and the sisal fiber was approximately linear. 3) The SFs created a skeletal-like network that encased the soil particles, and the hydroxyl functional groups in the PVA molecules bonded with both the soil particles and the fiber surface, thereby enhancing the interfacial properties. This interaction resulted in a tighter connection between the soil particles and SFs, which improved the stability of the structure. 4) The incorporation of a PVA solution and SFs significantly enhanced the mechanical strength and deformation resistance of the loose accumulated sandy soil. The optimal ratio for the improved soil was SP = 3% and SL = 15 mm, which increased the cohesion from 24.54 kPa in untreated loose accumulated sandy soil to 196.03 kPa. These findings could be applied in engineering practices to improve and reinforce loose accumulated sandy soil slopes in southeastern Xizang and provide a theoretical basis for such applications.

Frost heave in cold regions requires urgent measures to improve the mechanical properties of soils. However, harsh climatic and environmental conditions escalate the costs of engineering construction and operation. Therefore, it is imperative to enhance the sustainability of engineering designs. In this study, different sisal fibre contents, specific proportions of metakaolin, and alkaline activators were added to silty clay to alleviate frost heave, as well improve the mechanical properties of soils. Firstly, the unconfined compressive strength (UCS) and shear strength of soil samples containing varying sisal fibre geopolymer were tested before and after freeze-thaw cycles (FTCs). To analyse the effect of FTCs on thermal conductivity, the thermal conductivity of fibregeopolymer solidified soil (FGSS) with different sisal fibre contents was evaluated. Subsequently, X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry were conducted on the samples before and after the FTCs. Then, the variations in soil temperature, volumetric unfrozen water content, heat flux, vertical deformation, and soil pressure during the FTCs were analyzed. The results indicated the following: 1) Sisal fibre and geopolymer improved the mechanical performance and adhesion among soil particles of FGSS after the FTCs. 2) The thermal conductivities of FGSS showed a tendency of initially increasing, then decreasing, and finally increasing as the sisal fibre content increased. 3) The addition of sisal fibres did not cause new chemical reactions but inhibited the reaction between metakaolin and the alkaline activator. 4) The combination of sisal fibre and geopolymer effectively mitigated frost heave. 5) Sisal fibre incorporation reduces CO2 emission index and economic efficiency index. Therefore, FGSS is proposed to provide a green and effective approach for addressing geotechnical engineering issues in cold regions.

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.