Reliability of using standard penetration test (SPT) in predicting properties of silty clay with sand soil

The properties of soil play an important role in many practices for geotechnical engineering. To determine the real values of these properties special techniques should be followed such as undisturbed samples and initial overburden pressures should be taken into consideration. Actually, it is difficult to obtain 100% undisturbed samples due to handling, transportation, release of overburden pressure and poor laboratory conditions. So, prediction of some properties such as shear strength parameters (c & <p) for hard and dry silty clay with sand soil with the help of standard penetration test (SPT) provides a good opportunity to obtain these parameters without using of more laboratory tests. Standard penetration tests (SPT), rough measure the strength of soil. The great merit of this test and the main reason for its widespread use is that it is simple and inexpensive. The shear strength parameters which can be inferred are approximate, but may give a useful guide in ground conditions where it may not be possible to obtain borehole samples of adequate quality like clay containing sand or gravel. This study was undertaken in order to study the reliability of using standard penetration test (SPT) in predicting some properties, (such as Atterberg limits LL, PL, PI, and shear strength parameters (c & <p)), of silty clay with sand soil. Many samples from this soil have been investigated for this purpose. The results of the research indicated that the shear strength of soil affects SPT number. Empirical equations to identify the shear strength parameters of silty clay with sand soil using corrected SPT number (N") have been proposed.