气动式四向控制空心圆柱扭剪仪的研制与应用

上海交通大学既有的空心圆柱扭剪仪只有扭矩可以进行动态控制,可进行动剪应力扭剪试验。为了研究应力主轴旋转对土体力学特性的影响规律,在仪器采用应力控制模式和考虑经济性的前提下,对既有空心圆柱扭剪仪进行气动化改造,使之具备轴力、扭矩和内外围压都可以独立自动控制的四向振动能力。首先介绍改造后仪器(SJTU-HCA)的组成和技术参数,梳理了气动控制相比于液压控制的优点,推导了进行主轴固定单调剪切试验和纯应力主轴循环旋转试验的基本公式,并且设计了仪器控制程序和自动控制算法。通过对砂土任意主应力角的主轴固定单调剪切试验,初步验证了仪器的静态加载能力。通过保持偏应力q、平均主应力p和中主应力参数b这3个控制参数下的纯应力主轴循环旋转试验,验证了仪器的动态加载能力,说明了改造后仪器具备各种复杂应力路径的工作能力。气动式改造经验可为今后研发土工仪器设备提供参考。

Development and application of pneumatic hollow cylinder apparatus with four-direction dynamic loads

Only the torque can be dynamically controlled in the traditional hollow cylinder apparatus, and the dynamic shear tests can be carried out. The existing hollow cylinder apparatus is modified to have the four-direction vibration capability, including axial force, torque, internal and external pressures, to study the influences of wave loads. The composition and technical parameters of SJTU-HCA are mainly introduced. The basic formulas for the fixed principal stress axis tests and the principal stress axis cyclic rotation tests are deduced, and the instrument control programs including the automatic control algorithm are prepared. The static loading ability of the apparatus is verified by the fixed principal stress axis tests of any principal stress angle for sand. Further, the dynamic loading capacity of the apparatus is verified by the principal stress axis cyclic rotation tests for sand under the three control parameters including the defection stress q, the average principal stress p and the principal stress parameter b. The results prove that the SJTU-HCA can work with various complex stress paths. The pneumatic improvement experience may provide a reference for the future development of geotechnical apparatus.