排水条件对不同固结度软黏土动力特性影响试验研究

地铁隧道下卧土层由于施工扰动通常存在不同固结度,列车荷载下土体应变规律也有所差异,进而产生不均匀沉降。通过室内动三轴试验系统对杭州饱和软黏土进行动力测试,研究了排水条件、固结度、振动次数对软黏土动孔压和应变的影响,在试验和现有研究成果的基础上建立了考虑初始固结度、振动次数、排水条件的应变软化模型。结果表明:固结度愈高的土体,孔压发展愈缓慢,并且随振动次数增加,在较低的孔压水平就可达到稳定,排水条件下的孔压发展规律可由不排水试验获取。土体应变随循环次数的增加而增加,随固结度的增加而降低;提出的应变模型考虑了荷载循环过程中土体的排水,可以较好地模拟不同固结度下饱和软黏土的应变发展规律。

Experimental study on effect of different drainage conditions on dynamic characteristics of soft clay under different degrees of consolidation

The underlying soil, which is disturbed by subway tunneling, will show a different degree of consolidation which is associated with the strain of soil, and thus cause uneven settlement. Hangzhou saturated soft clay is studied using a dynamic triaxial test system to find the effects of drainage conditions, degrees of consolidation and cyclic times on dynamic pore pressure and strain. A new strain-degradation model considering degrees of initial consolidation, cyclic stress ratios and drainage conditions is proposed on the basis of the experiments and the existing research findings. The results show that the higher the degree of consolidation, the slower the increase of the pore pressure. Furthermore, the pore pressure will be stabilized at a lower level with the increment of cyclic times, and the law of pore pressure under drainage conditions may be obtained from undrained tests. The dynamic strain increases with the increase of the cyclic times and decreases with the decrease of the degrees of consolidation. The proposed strain model considers the drainage of the soil during the loading cycles, and it can well simulate dynamic strain changes under different degrees of consolidation.