Tensile strength and suction of naturally available saturated clays with modified tensile testing apparatus and their relationships with unconfined compressive strength

Tensile crack development at the back of slope top is one of reasons for the slope failure. Tensile strength measurement for the analysis of such failure is very important. Here, tensile strength measuring apparatus developed by Tamrakar el al(11,12) is modified so that suction (-u(w)) could be measured along with tensile stress from the start to the end of the test. Unconfined compression (UC) tests are also done with suction measurements. Commercially available Kasaoka and Fujinomori clays are used as test specimens. Ratios of tensile strength (q(t)) to pre-consolidation pressure (P-c') found for Kasaoka and Fujinomori clays are around 0.16 and 0.07 respectively. Ratios of unconfined compressive strength (q(u)) to P-c' for Kasaoka and Fujinomori clays are around 0.50 and 0.24 respectively. Similarly, strength ratios (q(u)/q(t)) calculated for Kasaoka and Fujinomori clays are equal to 2.90 and 3.66 respectively. In case of tensile test, increment in suction value is seen around tensile failure zone. In contrary to this, in UC test, suction value decreases around unconfined compression failure. Suction values at failure in both tests are also compared and it is observed that the suction values at failure in both tests show similar values, their ratio being in the range 0.8 to 1.2.