Laboratory Test Of The Application Of New Rotary Penetration Apparatus In Stiff Loess

Cone penetration test (CPT) has been gradually used more than 50 years in China in a wide area of engineering, and now is accepted by geotechnical engineers as an in-situ testing measure. Compared with traditional drilling testing, CPT has many advantages, such as its continuum of data obtain, intuitive, reliability and repeatability. CPT, as a common by used in-situ testing measure, has a very important status in engineering reconnaissance, and has been applied widely into the actual projects. However, the limitation of penetration capability of cone penetration apparatus sets an obstacle on accurate determination in hardpans, such as hard loess and soft rock layers.In this paper, the accuracy and rationality of the newly developed rotary penetration apparatus have been verified, and the conclusion is that this apparatus can control the penetration force, the velocity of penetration or rotary velocity respectively. In addition, it is concluded that the apparatus can simulate the sample compressed by layers in different depth by controlling and imposing the lateral pressure and vertical pressure on the sample.The research focuses mainly on the rotary penetration in Xi'an Loess in laboratory. Through the comparison of the domestically common-used testing approach and the rotary penetration approach, it is proved that the rotary penetration apparatus can improve the penetration capability. The analysis shows that, the main penetration ability is influenced by the effect factors as follows: the diameter of cone probe, the velocity of penetration, and velocity of rotary. With the comparison of Probe resistance results calculated with different parameters, the analysiss, has given strong evidences to support that the apparatus can improve the capacity of penetration.The probe resistance in the rotary penetration has a closed relationship with the sample property, and another important outcome in this paper is about the quantitative analysis on the relationship between loess shear strength strength and key testing parameters, such as probe resistance and rotating torque, which is on the foundation of the new apparatus's veracity and rationality. This work significantly extends the application of rotary penetration from laboratory test to actual applications.