GATE CE 2024 Set 2 — Question 45

MSQ+2 / -0MediumAnisotropic PermeabilityPermeabilityGeotechnical EngineeringTwo-Dimensional SeepageSeepagePiping

Geotechnical Engineering → Permeability → Anisotropic Permeability

Last updated 5 September 2026

Question

Consider the statements P, Q , and R. P: Compacted fine-grained soils with flocculated structure have isotropic permeability. Q: Phreatic surface/line is the line along which the pore water pressure is always maximum. R: The piping phenomenon occurring below the dam foundation is typically known as blowout piping. Which of the following option(s) is/are CORRECT?

Correct answer (C) P is TRUE and R is FALSE; (D) Both Q and R are FALSE Solution Let's analyze the statements: Statement P : Compacted fine-grained soils with a flocculated structure (typically compacted on the dry side of optimum) have a random orientation of particles, which results in more isotropic permeability compared to dispersed structures. Thus, P is TRUE . Statement Q : The phreatic surface is the locus of points where the pore water pressure is atmospheric (zero gauge pressure). It is not the line of maximum pressure. Thus, Q is FALSE . Statement R : Piping is the progressive internal erosion of soil. Blowout (or boiling) refers to the heave of soil at the downstream toe due to high exit gradients. While related, piping below a dam foundation is not typically called "blowout piping". Thus, R is FALSE . Evaluating the options: (A) Both P and R are TRUE: False (R is false). (B) P is FALSE and Q is TRUE: False (P is true, Q is false). (C) P is TRUE and R is FALSE: TRUE . (D) Both Q and R are FALSE: TRUE . Therefore, the correct options are (C) and (D). Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (C) P is TRUE and R is FALSE; (D) Both Q and R are FALSE Solution Let's analyze the statements: Statement P : Compacted fine-grained soils with a flocculated structure (typically compacted on the dry side of optimum) have a random orientation of particles, which results in more isotropic permeability compared to dispersed structures. Thus, P is TRUE . Statement Q : The phreatic surface is the locus of points where the pore water pressure is atmospheric (zero gauge pressure). It is not the line of maximum pressure. Thus, Q is FALSE . Statement R : Piping is the progressive internal erosion of soil. Blowout (or boiling) refers to the heave of soil at the downstream toe due to high exit gradients. While related, piping below a dam foundation is not typically called "blowout piping". Thus, R is FALSE . Evaluating the options: (A) Both P and R are TRUE: False (R is false). (B) P is FALSE and Q is TRUE: False (P is true, Q is false). (C) P is TRUE and R is FALSE: TRUE . (D) Both Q and R are FALSE: TRUE . Therefore, the correct options are (C) and (D).

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