Comparison of CPTu Test and Laboratory Test Results in Determination of Shear Strength of Uromieh Lake Bridge Site Soils

In this study the undrained shear strength of soft soils of Uromieh Lake Bridge site is measured by CPTu and compared with the results of laboratory tests conducted on undisturbed and remolded samples. The CPTu tests conducted in 8 boreholes up to 100m.Unconfined compression test conducted on the undisturbed samples from the depth 20 to 30 m showed 0.3 to 0.4 kg/cm2 for undrained shear strength, meanwhile they are resulted 0.4 to 0.7 kg/cm2 from CPTu tests for the same depths. In spite of the undisturbed samples are obtained by thin wall tubes, but a reduction in strength due to sample disturbance are appeared. This reduction is about 30 to 70 percent. The results of remolded samples showed about 0.1 to 0.12 kg/cm2 for undrained shear strength. The difference between these values and the values resulted from undisturbed samples is about 4 times and the value of CPTu tests is about 5 times. Therefore the soft soils of Uromieh Lake are sensitive and in situ tests like CPTu is suitable and reliable for testing of them.