Coastal engineering impact: when a water wave strikes a sea-shore structure (such as a seawall, quay, or breakwater), what combined effects can occur on the structure and its foundation system?

Introduction / Context:
Wave–structure interaction in coastal engineering involves more than a simple static push of water. Breaking waves impose rapidly varying impact loads, generate internal pressures within porous media, excite vibrations in the structure, and may progressively weaken or undermine foundations through scour and pore-pressure cycling. Understanding this suite of actions is crucial for safe design and maintenance.

Given Data / Assumptions:

• Structure is located at or near the shoreline (e.g., seawall, quay wall, breakwater).
• Incident waves may break, run up, and reflect against the structure.
• Foundation media can be granular and partially saturated, allowing pore-pressure transmission.
• No special energy dissipation devices are assumed unless noted.

Concept / Approach:
Hydrostatic pressure acts over wetted surfaces. Superimposed on this is dynamic/slamming pressure during wave impact, which can be several times quasi-static levels for short durations. Cyclic loading induces vibrations (structural response) and fluctuating pore pressures (internal pressures) within armor layers and backfill. Repeated cycles and turbulent jets can cause toe scour and reduce effective stresses, gradually weakening the foundation.

Step-by-Step Solution:
Identify static component: hydrostatic pressure varies with depth (p = rho * g * h).Recognize dynamic component: impact/impulsive pressure spikes during breaking or run-up.Acknowledge vibration: time-varying forces excite structural modes, causing measurable vibrations.Account for internal pressure: wave pumping across permeable facings/backfill builds transient pore pressures.Note foundation weakening: scour and cyclic pore-pressure reduce safety margins over time.

Verification / Alternative check:
Field inspections after storms often reveal face damage, displaced armor, backfill settlement, and toe scour—empirical evidence of the combined actions listed.

Why Other Options Are Wrong:

• Each single effect (A–D) can occur; limiting the answer to only one omits the broader, realistic loading scenario.

Common Pitfalls:

• Treating wave loading as purely hydrostatic and ignoring impulsive loads.
• Overlooking pore-pressure effects through joints and permeable layers.

Final Answer:
all of the above.