Passage IV
The soil beneath a heavy structure can fail (crack or flow). Adding wires to a soil produces a mixture with a greater compressive strength than that of the soil alone. (Compressive strength is the minimum downward pressure that will cause a material to fail.)
Mixtures of Soil X and 1 mm diameter steel wires were tested for compressive strength. All the wires in a mixture had the same length (1 cm, 2 cm, or 3 cm) and the same angle (90°, 120°, 150°, or 180°, as shown below).
Figures 1, 2, and 3 show how the compressive strength of the mixtures with 1 cm, 2 cm, and 3 cm wires, respectively, varied with wire angle and with the percent by mass of the wires.
Diagram and figures adapted from Amir Kalhor, “Effect of Metal Fibers on Clayey Soils.” ©2008 by Electronic Journal of Geotechnical Engineering.
23. According to Figures 1−3, for mixtures containing 1.0 percent by mass of wires bent at an angle of 90°, as wire length increased, the compressive strength:
Your Answer is
Correct Answer is C
Explanation
1.0% in 1cm is about 170 at 90 degrees, the corresponding value of 2cm is about 180, and the corresponding value of 3cm is about 150, so first rise and then fall, choose C