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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。
The typical soil layers within the depth of foundation pit in the alluvial plain of the Yellow River are clay and silty clay with obvious rheological characteristics. The deformation and internal force values of the deep foundation pit supporting structures in this kind of soil have significant time effects, In order to grasp the changing trend of each control index, it is necessary to develop corresponding soil viscoelasto-plastic constitutive model. According to the indoor test data of deep foundation pit in Jinan Capital Culture and Art Center, the second order nonlinear Newtonian viscoelastic-plastic model is constructed and the mathematical relationship between visco-elastic plastic model parameters and indoor soil sample data is established. Through the establishment of constitutive model of visco-elastic and plastic incremental form and the secondary development of FLAC, the lateral displacement, moment and internal force of anchor cable during construction are analyzed. The precision of the model is verified by the engineering analysis need. The case study shows that the lateral deformation of support structure increases with time, and the initial development is rapid and the deformation tends to be stable in the later period. In contrast, the moment of supporting structure and the change of internal force of anchor cable show the characteristics of first increasing and then decreasing slightly to stable.