Adding fiber reinforcement to a loose sand alters the effective stress of the sand skeleton. The rate of pore water pressure build-up when undrained is reduced, and liquefaction may be delayed or prevented. Here the results of cyclic triaxial tests are presented that show this benefit. They are interpretated so the load carried by the fibers is separated from that carried by the pore water and sand skeleton. A newly defined pore pressure ratio demonstrates when the pore water pressure build-up is insufficient for liquefaction to occur. The rule of mixtures is used, along with separate constitutive laws for the sand skeleton and fibers. Account is given to the anisotropic fiber orientation distribution, by which the fibers affect the sand skeleton differently during compression and extension cycles. It is found that the stress state of the sand skeleton remains bounded by critical state strengths after many cycles, as is the case for unreinforced sands. Not correctly determining the load carried by the sand skeleton and adopting the conventional rather than a new pore pressure ratio makes the fiber reinforcement technology appear less effective at suppressing liquefaction than it actually is. This may, unfairly, hinder its uptake in industry.

Mixing discrete flexible fibers into sand is a reinforcement technology that increases the sand’s strength as well as ability to resist liquefaction. This study demonstrates the mechanisms by which the applied loads are distributed across and shared by a sand’s skeleton, the fibers, and the pore water in drained and undrained triaxial compression tests. It is shown how the effective stress on the sand skeleton may be quantified by invoking the rule of mixtures and separate constitutive laws for the fibers and sand skeleton. It is also shown how the fibers alter the load paths experienced by the sand skeleton. Most notably it is shown how the fibers prevent liquefaction and that the conventionally defined pore water pressure ratio may incorrectly indicate otherwise. Alternate and more suitable pore water pressure ratios are introduced, accounting for the transversely isotropic orientation distribution of fibers that prevails in most fiber-reinforced soils, that gives an accurate indication of how far away the reinforced sand skeleton is from a liquefied state. The new pore pressure ratios, which are dependent on the direction of the principal stresses and account for the fiber orientations, are for use in any situation when the potential liquefaction of fiber-reinforced sand is a concern. Use of the conventional pore pressure ratio, which until now has been the only one employed in the literature, may make the fiber-reinforcement technology appear less effective at suppressing liquefaction than it actually is. This may, incorrectly, hinder its uptake in industry.

Desiccation cracking frequently occurs in mud, clay, and pavement. Understanding the evolution of desiccation cracking may facilitate the development of techniques to mitigate cracking and even prevent it from developing altogether. In this study, experimental investigations were performed focusing on the effects of fibers on the evolution of desiccation cracking in soil-cement. Varied types of fibers (i.e., jute fiber and polyvinyl alcohol fiber (PVA)) and fiber contents (i.e., 0%, 0.25%, 0.5%, and 1%) were involved. The digital image correlation (DIC) method was employed to capture the evolution and propagation of cracks in the soil-cement specimens when subjected to desiccation. The results show that the presence of fibers imposes significant effects on the crack propagation pattern as well as the area and length of the cracks in the soil-cement during shrinkage. The addition of fibers, however, insignificantly affects the evaporation rate of the specimens. The crack area and crack length of the specimens decreased significantly when more fibers were included. There were no macroscopic cracks observed in the specimens where the fiber content was 1%. The DIC method effectively helped to determine the evolution of displacement and strain field on the specimens’ surface during the drying process. The DIC method is therefore useful for crack monitoring.

In this study, the feasibility of using red mud (RM)-loess (L) mixture (RM-L) to treat acidic wastewater (AW) containing Mn(II) was investigated through batch experiments. The optimum mass ratio of RM to L was obtained by exploring the treatment performance of varied mass ratios of RM to L on AW under different initial pH values. Furthermore, the effects of dosage, contact time, and initial concentration on the treatment of AW with RM-L under optimum mass ratio were explored. The removal mechanism of Mn(II) was clarified using adsorption mathematical models combined with characterization. The results indicate that the optimum mass ratio of RM to L was 7:3. The addition of L promotes the equilibrium adsorption for Mn(II) on RM-L under optimum mass ratio (RM-L (7:3)) and improves the dispersibility of RM-L (7:3). Moreover, hydroxyl, carbonate, and metal-oxygen groups in RM-L (7:3) play an important role in the removal of Mn(II) and the increase in pH value to 8.4 from 3. The adsorption type of Mn(II) is monolayer adsorption, and the adsorption process of Mn(II) is spontaneous and dominated by chemical adsorption.

Geogrid-reinforced piled embankments (GRPEs) provide an economical and effective way to construct highways and railways on soft soil foundations. This paper proposed a new design method for GRPEs. The method was based on the soil arching and tensioned-membrane effects, the bearing capacity of the subsoil was considered as well. The originality of the proposed method lies in considering the stress history of the subsoil, and different over-consolidation ratios (OCRs) were used in calculating the settlement of subsoil. This design method, initially, established the vertical equilibrium of the unit body between the pile caps immediately above the subsoil. After that, the design charts were produced by solving the overall equilibrium equation from which engineers can intuitively obtain the maximum strain of reinforcement, and the tensile force can be used in the ultimate limit state analyses. The design method was then validated by three case studies, which showed good reliability with the maximum error being less than 18%. Parameter study results indicated that the maximum strain of reinforcement for the under-consolidated soil was 80–120% larger than that for normally consolidated soil and more than four times greater than that for over-consolidated soil.