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循环单剪试验被认为是研究地震场地中土体动力特性最合适的方法。为减小尺寸效应影响及解决工程中广泛存在的加筋土及粗颗粒土动力特性测试问题,研究大尺寸循环单剪试验方法具有重要意义。基于此,介绍了一种大型循环单剪试验装置,采用竖向线性滑动轨道约束上加载板和采用水平滑动轨道约束下加载板,确保前者仅发生竖向平动,后者仅发生水平平动,采用层叠的、带层间橡胶膜、分离式4点支撑的钢筋环构成的柔性剪切箱为试验提供侧向边界约束,确保了对单剪土样加载边界条件的真实模拟。针对土工格室加筋橡胶砂的测试结果表明:大型循环单剪试验装置得到的土动应力-动应变关系较好地反映了土在循环荷载作用下的滞回性、非线性和棘轮特性,大型循环单剪试验装置得到的G_d-g_a和D-g_a曲线变化规律与常规尺寸试验基本一致,证明其具有可行性;大尺寸试验得到的动剪模量特性与常规尺寸试验之间的差异,与单剪试验尺寸效应结论相符;试验中阻尼比特性受尺寸效应影响的规律性不明显。
Cyclic shear test is considered to be the most suitable method to study the dynamic characteristics of soils in the earthquakes. In order to reduce the effect of size effect and solve the testing problems of dynamic characteristics of reinforced earth and coarse grained soil widely existing in engineering, it is of great significance to study the large-size single shear test method. Based on this, a large-scale cyclic single-shear test device is introduced, which uses the vertical linear sliding rail to restrict the upper loading plate and the horizontal sliding rail to restrain the loading plate to ensure that the former only has vertical translational motion and the latter only horizontal translational motion, A flexible shear box consisting of laminated, layered rubber membranes with split 4-point support bars provides a lateral boundary constraint for the test to ensure realistic simulation of the boundary conditions for single-shear soil loading. The test results of the geogrid-reinforced rubber sand show that the dynamic stress-strain relationship of soil obtained by the large-scale single-shear test device can well reflect the hysteresis, nonlinearity and ratcheting characteristics of soil under cyclic loading, The curves of G_d-g_a and D-g_a curves obtained by the large-scale single shear test device are basically the same as those of the conventional size test, which proves that it is feasible. The difference between the dynamic shear modulus characteristics obtained by the large-scale test and the conventional size test, Which is in good agreement with the conclusion of single-shear test. The regularity of the damping ratio in the test is not obvious due to the size effect.