人工冻结黏土经验模型参数确定及蠕变规律验证

人工冻结法不仅常用于软土、砂层中地铁旁通道开挖及基坑围护等工程,在富水、深厚岩土层矿山井筒建设中也常采用此方法。掌握人工冻土物理力学性质及蠕变规律对安全、快速施工至关重要。对采用冻结法施工的某矿立井深部地层黏土进行-5、-8、-10、-15℃下单轴抗压强度试验及不同应力水平的蠕变特性试验。试验结果表明:抗压强度与冻结温度呈线性相关;在同一试验温度下,随着应力等级升高,轴向变形呈上升趋势;在同一应力水平下,随着试验环境温度下降,轴向变形呈下降趋势。引入考虑温度效应的经验蠕变模型,在各负温及不同应力水平下的应变与时间取对数具有线性关系的基础上,将线性表达式代入对应公式中联立方程组进行求解确定模型参数。将模型计算值与试验数据进行对比,反映出该模型能够较好地模拟人工冻结黏土蠕变初始变形阶段和稳定变形阶段。所建立的模型具有参数较少、易于确定、参数物理意义明确等优点,为冻结壁设计提供了一种有效的计算方法。

Parameter Determination of Empirical Model of Artificial Frozen Clay and Verification of Creep Law

The artificial freezing method is not only commonly used in the excavation of subway side passages in soft soil,sand layers,and foundation pit support,but also in the construction of mine shafts with rich water,deep rock and soil.Mastering the physical,mechanical properties and creep laws of artificial frozen soil is essential for safe and fast construction.Perform uniaxial compressive strength tests at -5,-8,-10 and -15 ℃ and creep characteristics tests at different stress levels on the deep formation clay of a mine shaft constituted by the freezing method.The experimental results show that the compressive strength is linearly related to the freezing temperature;At the same test temperature,as the stress level increases,the axial deformation shows an upward trend;At the same stress level,as the test environment temperature decreases,the axial deformation shows a downward trend.Introduce an empirical creep model that takes into account the temperature effect,based on the linear relationship between the strain and time at each negative temperature and different stress levels,the linear expression is brought into the corresponding formula to solve the simultaneous equations to determine the model parameters.Comparing the calculated values of the model with the experimental data shows that the model can better simulate the initial deformation stage and the stable deformation stage of artificially frozen clay.The established model has the advantages of fewer parameters,easy determination,and clear physical meaning of the parameters,which provides an effective calculation method for the design of frozen walls.