Figure 3-67. Typical rubble-mound structures.

• Sloughing of side slope

• Slippage of base material as a result of scour by currents

• Dislodgment of stones by wave action

• Excessive setdement of the seabed supporting the structure

During the inspection of seawalls, breakwaters, groins, and jetties, similar to those shown in Figure 3-67, the inspector should check for horizontal and vertical alignment. He should also be particularly watchful for signs of breakage or displacement of large stones or concrete armor elements, and washing out of substrate under the larger stones or concrete elements, particularly at the toe of the structure. These losses can be early signs of eminent structural failures if corrective action is not taken.

Other points to check include curbing, handrails, and catwalks (as applicable) for loose, missing, or broken sections, obstructions, and other hazardous conditions.

Inspection of rubble-mound structures should include:

• Erosion of core material by wave action.

• Erosion of small stones in riprap.

• Stability of armor stones or blocks.

• Breakage and displacement of concrete armor elements.

• Washing out of substrate at the toe of the structures.

• Undermining of foundation.

• High water mark; overtopping.

• Settling of structures.

3.9.7 Typical Inspection Procedure

Inspection of a rubble-mound structure should proceed as outiined in Table 3-9.

Checkpoint Description

1 Swim around the base of the structure looking for beginning weaknesses in the base, such as washout of small stones and core material.

2 Note signs of detrimental wave action, such as scouring and sloughing.

3 Record all pertinent information on a Plexiglas slate. After returning to the surface, transfer the information into the inspection log.

4 Record the result of the above-water inspection, include a description of the alignment and general condition of the mound, such as dislodge-ment of stones, gaps, and other weaknesses.

Table 3-9

Rubble-Mound Structure Surface and Underwater Inspection Checklist

3.9.8 Equipment and Tools Required

Inspectingrubble-mound structures requires that divers be equipped with recording devices, such as a Plexiglas slate, grease pencil, and cameras.

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