黄土地基动力沉降特性试验研究

路基工后沉降控制是客运专线路基工程研究的重点内容，其中地基在列车荷载长期重复作用下的累积沉降不可忽视。为揭示黄土地基在列车振动荷载长期作用下的沉降变形，通过对原状黄土试样的循环三轴试验，模拟实际列车荷载瞬时加载状态，采用不等向长持时加载，得出了在不同围压条件下黄土的动强度特性和循环应力-累积应变关系，并对较小循环应力下的循环应力-累积应变关系进行了归一化处理，得到了以下结论：①黄土的累积应变随时间的增加而增大，当循环应力不超过临界应力时，应变会最终达到稳定；反之，黄土结构遭到破坏，应变不能达到稳定；②不同围压下的黄土累积应变均随循环应力的增大而增大，且临界循环应力随围压的增大而增大。③在同一围压状态和同一应变破坏标准下，动强度随振次的增加而减小；④在不同围压、相同振次条件下达到相同的应变所需要的循环应力随围压的增大而增大；⑤在较小循环应力作用下，不同围压下黄土的累积应变随循环应力增加呈线性增长。

Experimental study of dynamic settlement behavior of loess foundation

The settlement after construction is the major research project for subgrade of dedicated passenger railway line, in which it is indispensable to keep the accumulated settlement under long-term train load repeatedly with a reasonable range. To discover the rule of loess foundation accumulated settlement under long-term train load repeatedly, a series of cyclic traxial texts were carried out for undisturbed loess; through anisotropic and long duration loading simulating the condition of constant loading of train load, the loess behavior of dynamic strength and cyclic stress-accumulated strain relationship under different confining pressures were obtained; and the cyclic stress-accumulated strain relationship at small cyclic stress were normalized. Results show that (1) The loess accumulated strain increases as time, and it can reach a relative stability value when the cyclic stress is less than critical stress, whereas it can't do. (2) The loess accumulated strains under different confining pressures increase with the increase of the cyclic stress; and the critical stress increases with the increase of confining pressure. (3) Under the same confining pressure and strain failure criterion, the dynamic strength decreases with the increase of cyclic number. (4) Under different confining pressures and the same cyclic number, when reach the same strain value, the cyclic stress increases with the increase of confining pressure. (5) When the cyclic stress is small, the loess accumulated strains under different confining pressures increase linearly with the cyclic stress.