What are the bolts driven into the rock on some beaches for?

A permeable solution can be obtained by one or more rows of timber piles driven directly into the beach at relatively ... sheet piling can be filled with sand, gravel, earth or stone with the top layer consisting of rock or rubble ..... By the end of 1991 some areas were scoured out to bare rock and the beaches. read more

Once the bolt has popped out as much as it can (about a 1/2" from the wall) slide a "tuning fork" under the hanger and pull. "Tuning forks" are made simply by grinding out the center of a #3 or #4 Lost Arrow. The resulting tool (which resembles a tuning fork) is driven under the hanger. read more

Install setting tool fully onto the exposed threaded end. Provide space between the setting tool and the hex nut. Initially torque the bolt to the required torque with an impact gun, pneumatic, or hydraulic torque wrench. This action migrates the cone into the shell, thus expanding the mechanical anchor into the rock. read more

Counting against underground mining are the costs, which, for each ton of material mined, are much higher underground than on the surface. There are a number of reasons for this, not the least of which is that the size of underground mining equipment—because of ground conditions, ore body geometry, and other factors—is much smaller than in the open pit. read more