Abstract
We report results of experiment on the estimation of decreasing strength of natural stone exposed to repeated dynamic loading. The study was conducted in order to assess the feasibility of using natural stone for the accompanying extraction of stone blocks under conditions of gravel quarries. We examined samples from 13 Ukrainian deposits of natural stone. The stresses were created by a weight dropped on the tiles made of natural stone. The damage was evaluated using the ultrasonic device UK-14MP. The established resistance of rock to repeated impact actions showed that at a low specific energy of the impact (1.47‒2.7 kJ/m 3 ) there are the granites (Zhezhelivski, Tokivski, Koretski deposits) that are almost not destroyed. These very deposits are suitable for the accompanying extraction of blocks of natural stone under conditions of gravel quarries. Building structures from these fields can be used in facilities and buildings that are exposed to vibration. Depending on the energy capacity of destruction, we conditionally divided natural stone into three groups. By applying a nondestructive control, we found that granites lose their strength prior to destruction from 11.6 to 41.5 % because of anthropogenic microcracking. The fatigue strength of granites is affected by the content of quartz; an increase in quartz results in increasing strength. It is demonstrated that the texture of granite exerts not a less impact on the strength of the stone; an increase in grain size in granite leads, despite a considerable content of quartz, to a decrease in the stone fatigue strength. Increasing accessorial minerals in granites leads to a decrease in fatigue strength
Highlights
Destructions resulting from a long-lasting exposure to repeated or variable loads are called fatigue destruction
– layer of sand; 5 – sample of the tested stone; 6 – wooden box Resistance of rock to impact action was determined in line with a procedure according to GOST 30629-2011 “Facing materials and articles made of rock
It is difficult to sort rocks for fatigue strength, so a given procedure is effective for assessing the resistance of natural stone to a single impact
Summary
Destructions resulting from a long-lasting exposure to repeated or variable loads are called fatigue destruction. The largest stresses at which a sample of rock can for a long time maintain stability (solidity) under conditions of variable loads without breaking are called the limit of fatigue strength. This phenomenon was first discovered by the German scientist Völer, a railroad engineer who developed the procedure for determining the limit of fatigue strength and formulated several laws of fatigue durability of parts and assemblies in the railroad rolling stock. It is possible to assess the weakening of strength of rocks under the action of cyclic dynamic loads using nondestructive methods. Analysis of the intensity of carrying out blasting operations, as well as the resistance of rocks to cyclic dynamic loads, will make it possible to split a quarry into zones where it would be possible for each deposit to isolate damaged and undamaged areas of the rock massif
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