Question

06: The results shown in the table below were obtained from a series of consolidated- undrained triaxial tests for specimens of saturated clay. Answer TWO of the followings: (a) Compute effective principle stresses for all specimens (b) Draw (by scale) Mohr Circle for total and effective stresses for second specimen (c) Calculate the effective shear strength parameters by using related equations for the data of the third specimen (15 Marks)

Answer 1

7.1

The suitable test for finding angle of friction and adhesion between concrete pile and surrounding soil is Direct shear test.

Direct shear experiments were carried out both to investigate the interaction between a predominantly cohesion less soil and in-situ concrete and the validation of the tangent of two-third of the angle of internal friction angle normally assumed in design involving stability of structures with respect to friction. The tests for soil to soil interface indicate internal friction angles of 13.9° and 14.3°, while the soil to in situ concrete interface indicates friction angles of 24.9° and 27.9°. For the soil–concrete interface; the tangent of two-third of the friction angles gives values that are developed by a range of normal stress indicated by the direct shear experiment. These values are between 141 and 430 kPa. The friction values computed from the soil–concrete interface are very conservative for this range of normal stress.

7.2

The number of test required to determine shear strength parameter is three (03).

Because, all specimens are supposedly saturated the shear strength are similar for all tests.