Soil liquefaction triggers during earthquakes: which of the following factors are associated with the behavior of saturated sand that can lead to liquefaction?

Introduction / Context:
Liquefaction is a seismic phenomenon where saturated, loose sands lose strength and stiffness, behaving temporarily like a liquid. Recognizing controlling factors is vital for site selection, ground improvement, and performance-based geotechnical design.

Given Data / Assumptions:

• (1) Number of stress cycles during shaking.
• (2) Frequency and amplitude of earthquake-induced vibrations.
• (3) Intrinsic sand characteristics (gradation, fines, fabric).
• (4) Relative density/state (loose to dense).

Concept / Approach:
Excess pore pressure builds when cyclic shear strains cannot dissipate, reducing effective stress. More stress cycles and larger amplitudes promote pore-pressure buildup. Susceptible soils include uniformly graded, loose sands or silty sands with low plasticity. Higher relative density generally increases resistance to liquefaction.

Step-by-Step Solution:
Evaluate (1): More cycles increase cumulative pore-pressure rise.Evaluate (2): Higher amplitude and certain frequency content are more damaging.Evaluate (3): Soil properties (void ratio, fines content, plasticity) govern susceptibility.Evaluate (4): Relative density is a primary state variable; denser sands resist liquefaction.Therefore, all four factors are associated with liquefaction behavior.

Verification / Alternative check:
Empirical charts (e.g., cyclic resistance ratio vs SPT/CPT) and case histories incorporate shaking intensity, duration (cycles), and soil state/characteristics, confirming the set of factors.

Why Other Options Are Wrong:

• Any subset (e.g., 1,2,3 or 2,4) omits relevant contributors recognized in liquefaction evaluation frameworks.

Common Pitfalls:

• Ignoring the role of saturation/drainage; liquefaction requires saturated conditions and limited drainage during shaking.

Final Answer:
1, 2, 3 and 4