软弱夹层对水泥土单轴压缩影响研究

Study on the influence of weak interlayer on uniaxial compression behaviors of cement soils

为探究软弱夹层厚度比对水泥土试样单轴压缩力学参数和破坏模式的影响规律,借鉴含单夹层盐岩的制样方法制备含不同软弱夹层厚度比的单夹层水泥土试样,进行室温和冻结状态下的单轴压缩试验。在室内试验研究的基础上采用PFC2D对水泥土单轴压缩进行模拟,分析试样受荷后的细观力学响应机制。最后建立软弱夹层与荷载耦合作用下水泥土单轴压缩损伤本构模型,探讨软弱夹层厚度比对试样损伤变量演化的影响。研究结果表明:(1)室温和冻结状态下水泥土试样单轴抗压强度和弹性模量均随着软弱夹层厚度比的增加呈负指数规律衰减;破坏应变随软弱夹层厚度比增加呈抛物线变化规律。(2)PFC2D模拟得到的不同软弱夹层厚度比的水泥土试样单轴压缩力学参数以及破裂模式与室内试验结果比较吻合,数值模拟和室内试验均表明软弱夹层厚度对试样破坏模式影响较大。(3)软弱夹层与荷载耦合作用损伤本构模型能够较好地描述室温和冻结状态下含软弱夹层水泥土试样在单轴压缩荷载下的应力-应变关系,软弱夹层的存在使试样变形过程中损伤程度差异明显。软弱夹层厚度比越大,在很小的轴向应变时试样总损伤变量就达到很大值,试样很快就出现破坏。

In order to explore the influence of the thickness ratio of weak interlayer on uniaxial compression parameters and failure modes of cement soil samples,cement soil samples with a single interlayer of different thickness ratios were prepared by using the sample preparation method of single interlayer salt rock,and uniaxial compression tests at room temperature and frozen state were carried out.The uniaxial compression of cemented soil was simulated by PFC2D,and the micromechanical response mechanism of the specimen after loading was analyzed.An uniaxial compression damage constitutive model of cement soil under the coupling of weak interlayer and load was established,and the influence of the thickness ratio of the weak interlayer on the evolution of damage variables was investigated.The results show that the uniaxial compressive strength and elastic modulus of cement soil samples decrease negatively exponentially with increasing the thickness ratio of the weak interlayer at room temperature or frozen state,and that the failure strain changes parabolically with enhancing the thickness ratio of the weak interlayer.The uniaxial compression mechanical parameters and failure modes of the cement soil samples with different weak interlayer thickness ratios obtained by PFC2D simulation are in good agreement with the results of laboratory tests.Both numerical simulations and laboratory tests show that the thickness of the weak interlayer has a great influence on the failure mode of the sample.The developed damage constitutive model of weak interlayer and load coupling can well describe the stress-strain relationship of cement soil samples with a weak interlayer under uniaxial compression load at room temperature or freezing state.The weak interlayer makes the damage degree of the specimens obviously different in the process of deformation.The larger the thickness ratio of the weak interlayer is,the larger the total damage variable of the sample will be when the axial strain is small,and more quickly the sample breaks.