Due to the environmental pollution caused by the production and consumption of cement, the demand for new and environmentally friendly methods to improve and strengthen the soil is increasing. In addition, reinforcing the soil with steel fibers improves the mechanical properties, including the formability and bearing capacity of the soil. The purpose of this research is to evaluate the effect of zeolite on the behavior of cemented sand soil reinforced with steel fibers. In the following, the unconfined compressive strength (UCS) test was used to check the compressive strength, and the flexural strength (FT) test was used to check the flexural. It should be mentioned that to improve the soil from cement in the amount of 5% by weight, zeolite in the amount of 0, 25, 50, 75 and 100% was used instead of cement, as well as steel fibers in the amount of 2% and random distribution in the curing of 28-day. In the results of unconfined compressive strength tests, the best replacement percentage of zeolite instead of cement in sandy soil was 25%, which initiated an increase in unconfined compressive strength and an increase in the failure strain of the sample. In the results of flexural strength tests, 25% of zeolite to replace cement in sandy soil affected the greatest increase in flexural strength and increased soft behavior. In addition, with the addition of steel fibers, the samples endured much more displacements than those without fibers. [GRAPHICS]

Shotcrete plays a pivotal role in the construction of tunnels and underground structures; however, its inherent brittleness necessitates reinforcement to enhance ductility. This research explores the use of fiber-reinforced shotcrete as primary tunnel support to enhance ductility and reduce brittleness. Traditional steel mesh reinforcement complexities have led to the investigation of alternative materials. The research evaluates different fiber mix designs, including industrial steel, recycled steel fibers from tires, and Forta fibers, examining their strength parameters and deformation performance. A 3D finite element model is used to simulate a horseshoeshaped tunnel with optimal mix design and plain shotcrete in a soil environment. The study finds that hybrid industrial and recycled fibers are more effective than single fibers, enhancing compressive, tensile, and flexural strength and reducing ground surface settlement and tensile damage. The optimal mix design of this study has increased compressive, tensile, and flexural strength, as well as flexural toughness, compared to plain shotcrete. Numerical modeling reveals that utilizing fiber reinforced shotcrete made out of optimal fiber mix design as primary support results in a significant reduction in ground surface settlement and tensile damage value. Furthermore, the study shows a significant reduction in the damaged zone area under tensile stresses. The results of the study highlight the potential of fiber reinforced shotcrete as a primary support for tunnels, leading to improved performance and sustainability in tunnel construction.

Grouted rock bolts subject to axial loading in the field exhibit various failure modes, among which the most predominant one is the bolt-grout interface failure. Thus, mechanical characterization of the grout is essential for understanding its performance in ground support. To date, few studies have been conducted to characterize the mechanical behaviour of fiber-reinforced grout (FRG) in rock bolt reinforcement. Here we experimentally studied the mechanical behaviour of FRG under uniaxial compression, indirect tension, and direct shear loading conditions. We also conducted a series of pullout tests of rebar bolt encapsulated with different grouts including conventional cementitious grout and FRG. FRG was developed using 15% silica fume (SF) replacement of cement (by weight) and steel fiber to achieve highstrength and crack-resistance to overcome drawbacks of the conventional grout. Two types of steel fibers including straight and wavy steel fibers were further added to enhance the grout quality. The effect of fiber shape and fiber volume proportion on the grout mechanical properties were examined. Our experimental results showed that the addition of SF and steel fiber by 1.5% fiber volume proportion could lead to the highest compressive, tensile, and shear strengths of the grout. The minimum volume of fiber that could improve the mechanical properties of grout was found at 0.5%. The scanning electron microscopy (SEM) analysis demonstrated that steel fibers act as an excellent bridge to prevent the cracks from propagating at the interfacial region and hence to aid in maintaining the integrity of the cementitious grout. Our laboratory pullout tests further confirmed that FRG could prevent the cylindrical grout annulus from radial crack and hence improve the rebar's load carrying capacity. Therefore, FRG has a potential to be utilized in civil and mining applications where high-strength and crack-resistance support is required. O 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).