# Experimental Study on Strength of Polypropylene Fiber Reinforced Cemented Silt Soil
###### Abstract
They found that the addition of fly ash and fiber could improve the strength of soil, and the effect of composite modified soil was better. The optimal ratio of fly ash and fiber content was 9% and 0.4%, respectively, and the fiber length was 20 mm. [PERSON] et al. [36] improved the compressive and tensile strength of soil by adding bamboo fiber. [PERSON] et al. [37] studied lime and fly ash synergistic polypropylene fiber-reinforced expandable poly-styrene lightweight soil. The California bearing ratio (CBR) value decreased with the increase in the lightweight soil particle content in the bearing ratio test, and the addition of fiber can improve the CBR value, with the best effect being achieved when the fiber content is 0.1%. [PERSON] et al. [38] used calcined cement solid waste chopped soil stirring residue instead of cement and mixed with polyvinyl alcohol fiber. The addition of fiber significantly improved the tensile strain capacity, and the maximum value was 3.2%. [PERSON] et al. [39] used polyester fiber to improve lime or cement solidified soil and found that lime and cement could improve the compressive strength of soil, and the addition of fiber could improve the failure mode of soil and play a role in resisting deformation. [PERSON] et al. [40] studied the reinforcement effect of rice husk and polypropylene fiber on the mechanical properties in three types of cement-stabilized soils (clayey sand (SC), sandy clay of low liquid limit (CLS), and low liquid limit clay (CL)). The experimental results reveal that the addition of rice husks and polypropylene fibers in cement-stabilized soil significantly improved the unconfined compressive strength (UCS) and split tensile strength (STS). [PERSON] et al. [41] studied the mechanical and hydraulic behavior of four different cement-soil composites under confining pressure of 100-900 kPa by consolidated undrained triaxial shear test and permeability test. It was found that the combination of fly ash and sisal fiber greatly improved the peak strength of cemented soil, and the addition of sisal fiber reduced the permeability. [PERSON] et al. [42] found that fibers are essential in reinforcing the mechanical properties of ultra-high performance concrete (UHPC), particularly the tensile and flexural strength. As a typical fiber material, polypropylene fiber has been widely used in soil reinforcement due to its light weight, good dispersion, high elastic modulus, and high tensile strength. Studies have shown that polypropylene fiber cement soil combines the advantages of chemical reinforcement and physical reinforcement, which can not only improve the compressive strength of soil but also improve the shear resistance and deformation ability of soil [43]. Domestic and foreign scholars have conducted extensive research on fiber-solidified soil based on uniaxial and triaxial tests, analyzed the curing mechanism of polypropylene fiber to improve the shear strength of soil [26; 44; 45], and explored the curve-fitting state of fiber cement soil under compression [11; 17; 46]. For example, [PERSON] et al. [20] tested fiber-reinforced cement soil and non-cement soil and found that the addition of discrete fibers can improve the shear strength of a cement-solidified body. [PERSON] et al. [12] studied marine clay by conducting an unconfined compressive strength test. The addition of fiber improves the compressive strength of cement soil and the axial strain corresponding to the peak stress. The failure mode of cement soil without fiber is brittle failure, while the failure mode of cement soil with fiber is plastic failure. [PERSON], [PERSON] et al. [7], through different fiber types, including polypropylene, carpet, steel fiber and other solidified cement soil, found in the unconfined compressive strength test that the addition of fiber improved the shear strength of soil, transforming brittle failure into ductile failure, and the compressive strength increased with the increase in the fiber con-tent.