Quarry Inspection: A Geological Perspective

by Gary J. D'Urso, U.S. Army Corps of Engineers, Pittsburgh, United States,

Document Type: Proceeding Paper

Part of: Durability of Stone for Rubble Mound Breakwaters


The need to use durable rock in building projects is becoming more critical as the costs of labor and materials rise. The Steering Committee of the 1991 Quarried Rock For Rubble Mound Structures Workshop highlighted this need, especially in view of the disconcerting fact that time-honored laboratory tests are often of questionable applicable reliability, for large rock. In addition, much of the laboratory information only hints at some of the more obvious information gained during a competent quarry investigation. There are examples of rock not meeting current specified laboratory criteria yet having a service record of successful use on a project for over fifty years (R.A. Everist, personal communication). There are other examples of rock meeting these criteria, yet failing on the project site in less than five years because of improper quarrying techniques (Marcus, 1991), These examples are dramatic evidence that current testing criteria, for large rock, needs revision and augmentation. Rocks were not created under carefully controlled conditions and must not be viewed by the construction community as being similar to a load of steel. Knowledge of even basic geologic processes and the specific geologic history of a rock is fundamental to the understanding of its strengths and weaknesses. It is suggested that the determination of rock durability should be a concerted effort of laboratory testing and professional field investigation. This paper does not address any specific problems related to rock durability but presents a general geological description of two quarries. These practical examples will show some of the inexpensive extralaboratory knowledge of rock sources that can be acquired through even an elementary geological quarry investigation. This paper also explains in a Comments section following each quarry discussion the reasons for the field observations and the petrographic descriptions.

Subject Headings: Rocks | Geology | Inspection | Laboratory tests | Field tests | Subsurface investigation | Project management | Material durability

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