This research studies the unconfined compressive characteristics of cement-treated sand reinforced with palm fiber. Type 1 Ordinary Portland cements with 3, 5, and 7% dry sand weight were mixed with sand and different amounts of water to produce cement-treated sand. Palm fiber contents of 0.5, 1, and 2% volume and fiber lengths of 10, 20, and 40 mm were utilized. Three performance parameters were considered to assess the performance of the cemented sand reinforced with palm fiber: peak strength, strain ratio, and toughness. The results showed that incorporating palm fiber elements could improve the peak strength and ductility and reduce brittleness by increasing the fiber content and length. All palm-fiber-reinforced samples showed a softening behavior and changed the behavior of cement-treated sand from brittle to semi-ductile or ductile. The compressive strength of reinforced cemented sand increased when the fiber length was 40 mm, and the compressive strength was reduced as the fiber content exceeded 1.0%. Palm fiber was the most efficient at increasing the toughness of the cemented specimen because of its rigidity and bridging ability. The optimum fiber content and length for the cement–treated sand were 1.0% and 40 mm, respectively.

Although the dilatancy of uniform sands or gravelly soil has been studied extensively in geotechnical engineering, studies on dilatancy of geogrid-reinforced coarse-grained soils are remarkably scarce in the literature. This paper presents an experimental investigation of the effects of geogrid and gravel content on the dilative behaviors of geogrid-reinforced sand-gravel mixtures. For this purpose, a series of large-scale direct shear tests were conducted on unreinforced and geogrid-reinforced sand-gravel mixtures with varying gravel content. It was found that the inclusion of geogrids results in higher ductility and friction angles of the specimens tested. Dilation was enhanced by an increase in gravel content but suppressed by the inclusion of geogrids. A hyperbolic model is developed to fit the stress-dilation relationship for the geogrid-reinforced specimens tested. The findings of this study may lead to a better understanding of the dilative behaviors of geogrid-reinforced coarse-grained soils.

This paper presents an experimental investigation of the effect of load duration on particle breakage and dilative behavior of a residual soil. To deepen the understanding of particle breakage subjected to load duration, the large-scale monotonic triaxial (TX) tests and creep TX tests were conducted on residual soil in saturated conditions. Values of particle breakage for the monotonic loading condition are compared with corresponding values for the creep loading condition calculated using a relative breakage index. For the creep TX tests, the load duration results in >1.5 times greater breakage index than the values of the monotonic TX test did. The obtained results suggest that load duration and stress level beneficially influence the particle breakage in the form of dilation suppression. The linearity is observed between the shear stress ratio and the dilation rate. A cycle with three phases is provided to help understand the creep behavior of coarse-grained residual soil: the concentration of ...

Our study investigates the geotechnical engineering properties of cement fly ash gravel mixtures in the laboratory. Gravels with three different size ranges were blended with cement and fly ash. The mixture properties were investigated, including the porosity, density, permeability, unconfined compressive and splitting tensile strengths, cohesion, and friction angle after curing for 28, 50, and 90 days, respectively. The experimental results revealed that the gravel sizes and fly ash contents significantly influenced the strength characteristics. The permeability coefficients of the cement fly ash gravel mixtures were 0.9 to 1.7 cm/s, much higher than a soil-cement column. The unconfined compressive strengths and splitting tensile strengths were found to be from 3.75 to 18.5 MPa and from 0.5 to 2.5 MPa, respectively. The cohesion and friction angle values ranged from 2.2 to 5.3 MPa and 30 to 40 degrees. The mixture strength was 6 to 30 times higher than a soil-cement column. The 15% fly ash provided the best strength characteristics as it exhibited the most significant calcium silicate hydrate contents. Thus, using cement fly ash gravel column-supported embankments is more productive than using a soil-cement column and granular pile to increase the column-bearing capacity and overall stability and accelerate the consolidation process.