Fig 1.
Particle-size distribution of the soil.
Before the tests, the soil samples were crushed by soil milling and passed through a 2.36 mm square hole sieve. The soil collected under the sieve was used for testing. D60 of the soil is 1.208mm, D30 of the soil is 0.344mm, D10 of the soil is 0.093mm, Cu and Cc of the soil are 13 and 1.06.
Table 1.
Physical indexes of soil used for testing.
Fig 2.
The carbide slag used in the study.
Because carbide slag contains a large amount of calcium hydroxide, it has strong hygroscopicity, so it needs to be dried before use. After drying and dehydration, it was crushed by soil milling and passed through a 0.075 mm square hole sieve.
Table 2.
Chemical composition of carbide slag.
Fig 3.
The fibers used for the study.
The fibers used for the study is polypropylene monofilament staple fibers, which have high strength and elastic modulus, excellent dispersion, no agglomeration, stable chemical properties, acid and alkali resistance.
Table 3.
Physical and mechanical properties of polypropylene fibers.
Fig 4.
Prepared specimen of fiber stabilized carbide slag solidified soil.
The size of the specimens were 50 mm in diameter, 50 mm in height, and the degree of compaction was 96%. After the specimens were produced using the static pressure method, they were placed in a curing box (temperature = 20±2°C; relative humidity ≥ 95%).
Table 4.
Proportions of specimens.
Fig 5.
Compaction curve of carbide slag solidified soil.
According to the experiment, the optimum moisture content of 2:8 carbide-slag-solidified soil was 13.62%, and the maximum dry density was 1.68g/cm3.
Fig 6.
Failure of the unconfined compressive test specimen.
There are many and small cracks on the surface of the sample. When the failure of the sample is serious, no fracture surface has been formed, resulting in the sliding of the soil block. At the same time, obvious expansion occurs at the end of the sample.
Fig 7.
Unconfined compressive strength of fiber stabilized carbide slag solidified soil.
For the same fiber length and content, the unconfined compressive strength of the solidified soil significantly increased with increasing curing time. For each group of fibers, the 7 and 28 d unconfined compressive strength increased with increasing fiber content, but the degree of improvement was limited.
Fig 8.
Indirect tensile strength test specimen.
Under the action of static load, the failure of specimen shows three processes: initial crack generation, crack propagation, new crack generation and fiber pulling out. After cracking, crack development and fiber pulling out will be carried out simultaneously.
Fig 9.
Results of indirect tensile strength test.
For the same fiber length and content, the indirect tensile strength of the solidified soil significantly increased with increasing curing time. With an increase in the fiber length for the same fiber content, the indirect tensile strength of the 7 d solidified soil did not increase significantly; in contrast, the indirect tensile strength of the 28 d solidified soil increased significantly.
Fig 10.
Results of unconfined compressive test with same Nf.
Under the same conditions, the unconfined compressive strength of the solidified soil slightly increased with the fiber content. The unconfined compressive strength of the solidified soil reinforced with 19 mm fibers was the highest.
Fig 11.
Results of indirect tensile test with same Nf.
Under the same Nf conditions, the indirect tensile strength of the 7d solidified soil increased with the fiber content. The indirect tensile strength of the solidified soil containing 19 mm long fibers was the highest. The 28d indirect tensile strength of each solidified soil increased significantly with the incorporation of fibers. The solidified soil containing 19 mm long fiber exhibited the highest indirect tensile strength.