Effect of wet – dry cycles on CBR value and grain size distribution particle on compacted residual tuff soil

Abstract Uncertain climate change is a natural phenomenon that common nowadays. Soil the result of weathering rocks and one causes this weathering. Residual soil formed on top original rock layer. In addition to parent rock, also affects residual soil, both in terms grain size shear strength. This modeling was carried out by giving wet-dry treatment tuff samples at Institut Teknologi Sumatera (ITERA) which were compacted with cycle 2 cycles, 4 6 8 10 cycles. From treatment, it will be seen gradation magnitude CBR value. The obtained calculated based concept breakage, namely Br value each 15.89%; 21.51%; 25.35%; 32.01%; 36.28%. For values for initial conditions are 50.74%, 40.34%; 29.763%; 25.16%; 22.825%; 20.580%. These results indicate longer occurs greater soil. reason, process needs considered use as subgrade road pavement.