GATE Civil Engineering (CE) 2017 Shift 1 Solved Paper

A consolidated undrained $\left(\overline{\mathit{C}\mathit{U}}\right)$ triaxial compression test is conducted on a normally consolidated clay at a confining pressure of 100 kPa. The deviator stress at failure is 80 kPa, and the pore-water pressure measured at failure is 50 kPa. The effective angle of internal friction (in degrees, up to one decimal place) of the soil is ________