黄河冲积平原深基坑施工变形黏弹塑性分析

黄河冲积平原地区基坑深度范围内典型土层为黏土和粉质黏土，具有明显的流变特征，在该类土层中进行深基坑施工支护结构变形和内力值具有显著的时间效应，为掌握各控制指标的变化趋势有必要开发相应的土体黏弹塑性本构模型。根据济南市省会文化艺术中心深基坑土样室内试验数据，构造二阶非线性牛顿体黏弹塑性模型，并建立黏弹塑性模型参数与室内土样试验数据之间的数学关系。通过建立黏弹塑性增量形式的本构模型，并进行FLAC二次开发，分析深基坑施工支护结构侧向位移、弯矩，锚索内力随时间的变化，模型精度经验证符合工程分析需要。实例分析表明，支护结构侧向变形随时间变化逐渐增大，且前期发展较快，后期变形趋于稳定。与之相反，支护结构弯矩和锚索内力的变化则呈现出先增大后小幅降低至稳定的特点。

Visco-elastoplastic analysis of deep foundation pit construction in Yellow River alluvial plain

The typical soil of deep foundation pit in the Yellow River alluvial plain is clay and silty clay. These two kinds of soils have rheological characteristics. The supporting structure deformation and internal force is time-effected when excavating in this soil. In order to master the trend of each control index, a soil visco-elastoplastic model should be developed. Based on the data of soil laboratory test in Jinan Provincial Capital Culture and Art Center deep foundation pit, the visco-elastoplastic second order nonlinear Newtonian fluid model is given. And the relationship between visco-elastoplastic model parameters and test data is built. First, the constitutive model of incremental form is built. Second, the visco-elastoplastic model is secondary developed in FLAC. Lastly, we use this model to analyze the lateral displacement moment and anchor internal force of foundation pit supporting structure. Based on this test, the model precision is proved. A case study shows that, the lateral displacement change is increased gradually with the increase of time; but the early increase is larger and the later deformation tends to be stable. The change of supporting structure moment and anchor internal force is increased at first then decreased in a small amplitude in contrary to the lateral displacement.