滨海软土非线性蠕变特性的试验研究

 合理描述滨海软土的蠕变规律对于软土地区各类建(构)筑物的长期稳定性和运行安全性是十分重要的。利用单向固结仪和改进的直剪蠕变仪，开展不同加荷方式下滨海软土的蠕变试验，获得应变与应力和时间的关系，分析其蠕变性状的结构性效应和影响因素，建立相应的蠕变模型。试验结果表明，天津滨海软土具有明显的非线性蠕变特性，其蠕变变形演化特征受其结构性制约和影响。在低应力水平条件下，软土蠕变量非常低，双对数应变–时间关系曲线存在明显的转折点；在高应力水平条件下，蠕变速率较高且产生很大的瞬时蠕变量；实施预压荷载作用不仅降低了软土最终的蠕变量，同时也影响到主、次固结的分界特性。采用修正的对数型表达式能较好地拟合滨海软土的瞬时弹性应变、衰减蠕变和稳定蠕变阶段。滨海软土的剪切蠕变变形在低应力水平下呈现出折线特性，而高应力条件下可近似为线性特性，其剪切模量随时间呈现减小趋势，随应力呈现先增大后减小的趋势，而黏滞系数随时间和应力呈现线性增大趋势。

EXPERIMENTAL STUDY OF NONLINEAR CREEP PROPERTY OF SOFT SOIL IN LITTORAL AREA

Reasonably describing creep law of coastal soft soil is very important for the long-term stability and running safety of buildings in soft soil area. By the unidirectional oedometer and improved direct shear creep apparatus，the creep tests in different loading methods are conducted. The relationships of stress，strain and time are got，the structural effect and influencing factor of creep character are also analyzed，and the relevant creep model is established. The test result indicates that the soft soil in littoral area of Tianjin has obvious nonlinear creep character and the creep evolutional characteristics are influenced by the structure. At low stress level，the creep deformation is very small，and there is an obvious transition in  curve of consolidation test. At high stress level，creep rate and creep deformation are high enough. When the pre-consolidation is carried out，the creep deformation turns low and the boundary of primary consolidation and secondary consolidation is influenced. The modified logarithm function can describe the transient elastic strain，attenuation creep and steady creep of soft soil in littoral area of Tianjin. The shear creep deformation assumes double line at low stress level and linear at high stress level. Shear modulus decreases over time and increases-before-decreases with the increasing stress，coefficient of viscosity increases over time and with the increasing stress.