Ultrasonic test application for evaluation of improvement of marl soil stabilized by lime

Ultrasonic test has been accepted for non-destructive, fast, and accurate measurement of elastic constants, longitudinal and shear wave velocities, in rock and soil materials in the geotechnical engineering. The ultrasonic test is valid for the measurement of compression and shear wave velocities in the both anisotropic and isotropic samples. There is a direct relation between the elastic constants and elastic waves velocities. The velocity of elastic waves varies with the variation of compression and tensile strengths of materials. In this research, using ultrasonic velocity-meter, propagation velocity of high frequency pulses, according to ISRM (International Society for Rock Mechanics), and ASTM D2845 standards, was measured in samples from an unstable telecommunication station site located in Ahvaz city in Iran. The geological materials of the site were composed of marl soils, and the sequences of sandstone, and marlstone. The test results showed that longitudinal and shear wave velocities, Young's and shear modulus are higher in the sandstone samples obtained from the site than the marlstone samples. Some engineering tests showed that the marl soils due to high clay minerals content and high swelling potential are the cause of instability in the form of crack in the site. Chemical stabilization with lime was selected as a way for reduction of the swelling potential and enhancement of the strength characteristics of the marl soils. Several samples of the marl soils were mixed and cured with different (1, 3, 6, 9, 12, and15) percents of lime. Longitudinal wave velocity, according to the standards mentioned above, was measured in the prepared samples. The test results showed that longitudinal wave velocity increases in the samples with the increase of lime content from 1 up to 9 percent, and decreases after 9 percent lime. The uniaxial compression test results showed that the uniaxial strength value of the prepared samples increases with the increase of lime content from 1 up to 9 percent, and decreases after 9 percents. Also, other geotechnical tests showed that 9 percent lime in the marl soil samples, is the optimum content for the improvement of the marl soils in the site. With comparison of the results from these tests, it can be inferred that the ultrasonic testing can be used as a fast method for the evaluation of improvement of marl soils stabilized by lime.