Relationship between penetration resistance and strength compressibility characteristics of soil

Abstract

The strength and compressibility properties of soil were determined from the soil collected by using Modified Shelby Tubes. Then these were used to correlate with Standard Penetration Resistance. Generally Standard Penetration Test (SPT) is performed as only means of subsoil investigation in Bangladesh. Detail investigation accompanied with laboratory tests are performed for important project only. Practicing engineers usually rely on SPT field test data and Correlations of SPT-N value with various soil parameters. Sometimes client are not convinced to spend more money for subsoil investigation. They are only willing to pay for SPT field test. Therefore it is necessary to know the correlations between SPT-N value and soil parameter of clay so that SPT-N value can be used for designing foundation. The objectives of the study were to develop a mechanism of controlling height of fall of SPT hammer, to establish correlation between penetration resistance and undrained shear strength of soil and to establish correlation between penetration resistance and compression index of soil. SPT and undisturbed sampling was done in four sites covering stiff soil and soft soil. From the test results following conclusions may be drawn. A linear relation between unconfined compressive strength and SPT-N value was found for all soils, soft or stiff, low or high plasticity. The relation is qu = 16.5N in kPa. Linear relation between compression index and SPT-N value was found for stiff soil. For soft soil the relation was found to be random in nature. Reliable linear relationship between natural moisture content and SPT-N value was found for all sites. However, no generalized or normalized relationship was found. Linear relationship between initial void ratio and SPT-N value was found for all sites. However, no generalized or normalized relationship was found for initial void ratio. Linear relationship between dry density and SPT-N value was found for all sites. However, no generalized or normalized relationship was found for dry density.