Unconfined Compressive and Splitting Tensile Strength of Basalt Fiber-Reinforced Biocemented Sand

The strength properties of basalt fiber-reinforced biocemented (BFRB) sand specimens with various calcite contents and fiber contents are investigated through a series of unconfined compressive and splitting tensile tests. Reverse injection is introduced to improve the uniformity of the calcium carbonate precipitation. The test results show that both the unconfined compressive strength (UCS) and splitting tensile strength (STS) at a given basalt fiber content increase significantly with increasing calcite content, whereas the axial strain of the peak failure state decreases with increasing calcite content. The improved ductility has implications for loading conditions where large deformations may be anticipated. The UCS, STS, and peak failure state strain increase with increasing fiber content at a given calcite content, which is interpreted to be due to the interlocking, reinforcing, and bonding effects observed in scanning electron microscopy (SEM) images. A phase-volume framework for determining the porosity of BFRB sand is developed and used within an existing empirical formulation developed for other types of fiber-reinforced, cemented geomaterials. Moreover, the UCS and STS of the BFRB sand can be described by the existing empirical formulations incorporating the cementing factor index expressed in terms of the porosity and calcite volumetric content. Predictions based on the empirical formulations are in good agreement with the test results for the UCS and STS of the BFRB sand specimens.