An emerging alternative to improve the mechanical properties of fine soils susceptible to cracking is the addition of fibers obtained from reused synthetic materials such as polyethylene terephthalate (PET). The technical literature on the fracture mechanics of PET fiber-reinforced soils is rather scarce, so there has been insufficient progress in determining fracture parameters and standardized procedures to find optimal reinforcement conditions. This research uses experimental techniques to induce tensile stresses in clayey silty soil samples from the Valley of Mexico reinforced with different fiber contents. By applying approaches based on linear elastic and elastoplastic theory, parameters useful for the study of fracture mechanics and flexural strength of PET- reinforced soil were estimated: tensile strength, critical energy release rate, critical stress intensity factor, and contour integral for crack propagation under plasticity. In addition, imaging techniques are used to measure the deformations generated in bending tests of reinforced soil beams and to study crack propagation from initiation to maximum stresses. The addition of PET fibers significantly improved soil response by reducing cracking, increasing tensile strength, and providing ductile behavior as cracking progressed. These effects indicate the great potential of recycled PET fibers as a subgrade improvement method for soft, cracking soil deposits, or even for earthworks and slope stabilization in clayey soils on road projects.

Adding cement to soft soils may lead to brittle behavior and the occurrence of sudden damage. Methods to further improve the tensile and flexural properties of cemented clay are noteworthy topics. This paper mainly focuses on the effect of cement and moisture content on the strength and flexural properties of cemented clay reinforced by PVA fiber. The selected clayey soil was a kaolin with cement content of 5%, 10%, and 15% and moisture content of 50%, 56%, 63%, and 70%. The results show that the incorporation of 0.6% fiber can effectively improve the deformability of cemented clay in unconfined compression tests (UCS). The strengthening effect of fiber, as seen in the peak strength and post-peak strength of UCS, was significantly related to cement content. As the water content increased, the compressive strength of the fiber-reinforced cemented clay decreased, but its load-bearing capacity enhanced. When the cement content was 15%, the splitting tensile strength of fiber-reinforced cemented specimens increased by 11% compared to cemented soil, but the deformability of the specimens became poor. In the cement-content interval from 5% to 10%, the bending toughness was significantly improved. Sufficient cement addition ensures the enhancement of PVA fibers on strength and flexural properties of cement-stabilized clayey soil.

Underprivileged people in many parts of Asia, Africa, Europe, and Latin America use earthen dwellings because of environmental and economic advantages. However, such non-engineered structures often encounter unacceptable risks from various natural calamities such as earthquakes, floods, etc. The 3rd January 2017 moderate earthquake in Tripura (NE India) is prime evidence of severe damage to earthen houses in rural Tripura. The present research focuses on enhancing the seismic strength of traditional earthen houses through mechanical stabilization with locally available low-cost sustainable natural fibers (i.e., jute and straw) and stabilizing materials (i.e., clay and lime), respectively. Primarily, the shear and flexural strength of both stabilized and unstabilized model rammed earthen wallettes are investigated experimentally. Thereafter, a 3D finite element (FE) numerical model is developed to verify the sanctity of the experimental findings. The study reveals that fiber-reinforced earthen wallettes, especially jute fiber-reinforced wallettes, exhibited significant improvement in shear and flexural strength including ductility behaviour whereas, clay and lime-stabilized wallettes offered improvement in strength exhibiting brittle failure. Finally, the seismic response of a prototype fiber-reinforced rammed earth wall is evaluated through 3D FE-based numerical modelling considering the input motion of the 2017 Tripura earthquake which also indicated significant improvement compared to the unimproved one. However, from the viewpoint of sustainability, it is concluded that carbon emissions of approx. 38% may be reduced in the case of natural fibers such as jute and straw compared to synthetic stabilizing agents (i.e., lime). Hence, the study promotes the use of low-cost sustainable fibers with a lower carbon footprint and minimum energy consumption in earthen houses.