| Summary: | Water is the greatest enemy of conducting underground work that contributes to more uncertainty in the underground design work, for example tunneling, foundation and cavern. Therefore it is important to carry out experiment and investigate on how the moisture content in the rock affects its compressive strength. For this experiment carried out, gypsum rock was selected as the type of rock to be tested. In simulating the natural gypsum rock, molded gypsum specimen was used.
In addition to the experiment, stiffness and ultrasonic test was tested with the saturation of gypsum rock. With information on the influence of water saturation on the gypsum rock helps to improve the safety of foundation design or underground work when encountering gypsum rock. It therefore provides some information when gypsum rock encountered an increase of a range of moisture content.
The data obtained from this experiment shows that the as moisture content increases, compressive strength decreases. It has a more adverse effect on the gypsum rock for moisture content from 0% - 12%. The experiment also proved that the ultrasonic velocity test value as a strong correlation with the compressive strength value.
In observing the crack formation from the gypsum specimen, high speed video was used. The high speed camera provides video with high frame rate in recording the slow motion of the crack initiation. It was observed that the crack from the saturated specimens tend to have an irregular crack line, while drier specimens tend to have a straighter crack line. In addition, the crack appearing on the higher saturated specimens was slower as compared to the lower saturated specimen.
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