Study Of Shear-wave Velocity And Cyclic Triaxial Liquefaction Tests Apparatus And Its Application

Because of the shortage of effective testing methods and device to study the correlation between liquefaction resistance and the shear-wave velocity of saturated sand at present, a new kind of combined test apparatus is developed through which shear-wave velocity measurement of soil samples and cyclic triaxial test can be carried out simultaneously. The main work is described as follows.First, the principle of sample shear-wave measurement by means of torsion vibration is studied and the technical programs to realize torsion vibration are presented. In the design process of such combined test apparatus, a series of important problem is discussed, such as the acoustic impedance match of material, frequency design and reliability determination, etc. Furthermore, the accuracy of device has been verified by the contrast test with bend-element tests and resonant column tests. Using the new apparatus, an initial shear-wave velocity control technique of saturated sand sample in the triaxial load cell was developed. Then, cyclic triaxial liquefaction tests were conducted by controlling the shear-wave velocity to study the correlation between the liquefaction resistance and shear-wave velocity of saturated sand. The result shows that the shear-wave velocity of saturated sand could be strongly related to the liquefaction resistance under a certain liquefaction criterion.Finally, the difference of soil stratum shear-wave velocity surveyed in-situ by single-hole method or cone penetration test and those obtained in laboratory test are discussed, which proves to be limited caused by sampling disturbance and directly related to the embedded depth and the soil indicator of soil layer. The variation of soil stratum shear-wave velocity depending on the depth can be reflected by the laboratory test result.