Research On The Tuning Of 5Hz Hollow Cylinder Apparatus Of Zhejiang University

In civil engineering, the soil experiences complex stress paths, especially under traffic, wave or earthquake loading, which include the principal stress rotation. The traditional equipments, such as direct shear apparatus, triaxial or true triaxial tests cannot simulate the effect of cyclic principal stress rotation entirely. Now, the best way to study the soil behaviour under complex stress paths is using the advanced apparatus, i.e. hollow cylinder apparatus (HCA).Based on the investigation of the history and present achievements in HCA, this thesis summarizes the deficiencies, such as the loading mode, the measure system, and the sample preparation etc. After comprehensive research, a most advanced hollow cylinder apparatus in the world was innovated in Zhejiang University with the support of GDS instrument Ltd, England. This new apparatus provides feasibility and reliability to investigate the influence of cyclic principal stress rotation on soil characteristic, with which more information can be obtained for design and construction.The major studies and achievements in this thesis are as following:(1) This new apparatus, ZJU-HCA was introduced. Particularly the details in loading mode, measure system and data collection were presented. After comparing and analyzing, the sample dimension, the frequency of dynamic testing, and the proper transducers for accurate measuring were determined for this apparatus.(2) Nowadays, due to the difficulties in sample preparation, few studies were carried on for intact clay. Aim to prepare a high quality intact sample, a cutting-head for inner wall was invented. It was proved to satisfy the Standard for soil test method for HCA. This great achievement solves the problem of intact sample preparation, especially for soft clay. It is easy to handle and quality-guaranteed, can be popularized(3) An entire procedure for setting up a clay sample was introduced, which involves outer cell and inner cell setting. It is one of the key steps for testing and will greatly impact the results if not properly fixed or having severe disturbance. Since the soft clay itself is not strong enough to sustain the heavy top cap, a tailor-made bracket was created to reduce the load and the disturbance during sample fixing, which is very effective and useful for better testing.(4) The formulae for outer and inner radius after consolidation were derived by using iteration method. They can improve measuring accuracy; thereafter better results can be expected. It validates Tatsuoka's hypothesis and is proven to be more accurate than his equation after comparing with the local measurement obtained from Kaman sensors.(5). Being a new apparatus, it is necessary to test its reliability. For the sake of this, the hardware part and the quality of the sample were checked. A series of testing were carried to verify the stabilization under dynamic loading, the applicability of different loading shape, and the repeatability. The quality of the intact sample was also tested. All the results show that this new ZJU-HCA has the capability and reliability of simulating the complicated stress paths, including the principal stress rotation.