3.8.1 Types of Stone Masonry Structures
Although very few waterfront structures built today are constructed from stone masonry, it is still necessary to be familiar with the inspection of this type of structure. Throughout the 19th century, stone masonry was generally used in constructing graving docks, bridge piers, quaywalls, and wharves. Typically, the quarried stone used was granite set into lime mortar or pordand cement mortar.
3.8.2 Deterioration of Stone Masonry Structures
Stone masonry structures typically develop problems at the joints between pieces
of stone. Failures of these types of structures usually occur as a result of washout of the joints. In addition, increased earth or hydrostatic pressure causes joints to crack and stones to fall out. Scouring at the base of the structure because of wave and current action and loss of fill from behind the structure are two common types of damage that can lead to serious structural failure.
3.8.3 Typical Inspection Procedure
Stone masonry retaining walls, such as those found on quaywalls and wharves, generally require only a very simple inspection, as follows:
• Begin the inspection at the waterline, checking for excessive weathering and abrasion deterioration, and loss of mortar from the joints.
• Inspect below the waterline, taking note of the general condition of the wall, and paying particular attention to the joints between each stone.
• If there are significant gaps between stones or stones are missing, note the location, depth, and length of missing stone.
• Continue to the bottom of the structure and note any undermining or scouring of the material under the wall structure.
• At any missing stone or undermining, probe the cavity to estimate the extent of the void (if any) behind or below the wall.
• Record the depth of the water at the base of the wall.
• After returning to the surface, immediately transcribe all information into the inspection log if information has not been communicated via hardwire. Also, record in the log the general condition of the wall above the waterline, especially noting all joints from which mortar has washed out.
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