P N OJHA, BRIJESH SINGH, V V ARORA, PRAMOD NARAYAN, AMIT TRIVEDI & MANTU GUPTA


3. Sample Collection and Laboratory Tests


The concrete core samples were extracted (Figure 1) from all accessible portions of the dam, covering the entire structure. A total of 100 samples of 150mm and 100mm diameter were tested. Visual observation of all the accessible portions of the four galleries, including the upstream and downstream portion of the dam, were carried out at the site and the concrete core samples extracted from different locations were also observed for any abnormal reaction in the concrete. During site inspection, based on data recorded by the relevant dam authority, it was found that the upstream side of the dam face was the most exposed to solar radiation during the summer period. No signs of distress in the concrete was apparently visible. Visual inspection of the concrete cores, as extracted, indicated dense and well-compacted concrete.


Figure 1. Concrete core extraction in the gallery of the dam The equivalent cube compressive strength was determined on hardened concrete core


samples of 150mm and 100mm diameter, extracted from the dam as per IS:516. The concrete core specimens were tested in a strain-controlled compression testing machine of 3000kN capacity (Figure 2) at a room temperature of 27 ± 2ºC, and relative humidity of 65% or more. Two extensometers in the middle half of the height were used to obtain the strain, and the two strains were averaged. Both ends of the concrete cylinders were finished parallel by grinding.


8 DAM ENGINEERING


Vol XXXII Issue 1


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