Triaxial mechanical properties and micro mechanism of fiber-modified cement soil

In order to explore the modification effect and its micro mechanism of polyester (PET) fiber on the mechanical behavior of coastal cement soil, triaxial and micro tests were carried out on the polyester fiber–modified cement soil (PECS). The unconsolidated undrained (UU) triaxial test shows that (1) the stress–strain curve of PECS samples gradually changes from strain softening type to strain hardening type with the increase of confining pressure and fiber content. (2) The shear strength and cohesion of PECS samples first increased and then decreased with the increase of fiber content. When the content of PET fiber was 0.4%, it reached the maximum value, which was 11 ~ 15% and 13 ~ 16% higher than that of CS samples, respectively. However, its internal friction angle is not sensitive to the fiber content. (3) With the increase of confining pressure and fiber content, the failure mode of PECS samples gradually changes from shear failure to bulging failure. Microscopic tests show that (1) appropriate amount of PET fiber can improve the strength of PECS samples by filling pores and bridging. (2) When PET fiber is excessive, the agglomeration effect of PET fiber will reduce PECS’s strength. The research results provide a solid reference for the application of PECS in practical engineering.