胶结结构性黏土的试验研究与本构建模

发布时间：2018-04-08 13:26

本文选题：胶结结构性土　切入点：本构模型　出处：《北方工业大学》2017年硕士论文

【摘要】：胶结结构性广泛存在于天然土中。胶结的存在使得天然土的强度较重塑土高,然而随着变形的发展胶结会逐渐减弱。因此,天然土的模量在加载初期较重塑土大但最终会趋近于重塑土的模量。这种现象不能被实际工程忽视,否则可能会增加实际工程的危险系数。因此,建立能够考虑天然土中胶结影响的本构模型具有重要的意义。由于天然土中胶结存在较大的离散性,并且取样过程也会使得其胶结发生变化,因此作者采用泥浆浇筑法进行胶结结构性黏土试样的制备以模拟天然胶结结构性黏土的主要特征。使用国产WG(GDG)系列高压固结仪和英国GDSTTS标准应力路径三轴仪对其进行一维压缩试验和常规三轴压缩排水剪切试验。试验结果表明:(a)胶结使其剪切破坏后的最终应力比高于相应重塑土;(b)胶结限制了试样剪切时体积应变的自由发挥。基于试验结果,将p～q应力空间中静止的临界状态线(CSL)扩展为动态的移动临界状态线(MCSL)。MCSL与CSL平行且随着胶结减弱不断移向CSL。根据MCSL建立了新的屈服面并依照相关联流动准则修正了剪胀方程,将胶结考虑进结构性土 UH模型。基于SMP准则的变换应力三维化方法,将胶结结构性土UH模型扩展到三维应力空间。与原结构性土UH模型相比,本文所提模型增加了一个新的结构性参数——初始胶结应力s0,其值为p～q坐标中MCSL与CSL之间的初始水平距离,通过无侧限抗压试验确定该参数。模型的演化规律表明本文所提模型能够光滑、连续地描述:(a)胶结结构性土的等向压缩;(b)胶结结构性土剪切破坏后最终应力比的变化特点;(c)胶结结构性土的剪胀规律;(d)胶结结构性土真三轴剪切中应力Lode角的影响。通过将胶结结构性土的试验数据与模型预测进行对比,表明胶结结构性土UH模型能够较合理地对结构性土的等向压缩、一维压缩、排水/不排水常规三轴剪切、等p排水三轴剪切及真三轴剪切等力学行为进行预测。
[Abstract]:The cementation structure exists widely in natural soil.The strength of natural soil is higher than that of remolded soil due to the existence of cement, but the cementation will weaken gradually with the development of deformation.Therefore, the modulus of natural soil is larger than that of remolded soil at the beginning of loading, but will eventually approach the modulus of remolded soil.This phenomenon can not be ignored by practical engineering, otherwise it may increase the risk coefficient of actual engineering.Therefore, it is of great significance to establish a constitutive model which can take into account the effect of cementation in natural soil.Because of the large dispersion of cementation in natural soil and the change of cementation in the sampling process,The experimental results show that the final stress ratio after shear failure is higher than that of the corresponding remolded soil.A new yield surface is established according to MCSL and the shear expansion equation is modified according to the associated flow criterion. The cementation is considered in the structural soil UH model.The UH model of cemented structural soil is extended to three dimensional stress space based on SMP criterion.The evolution of the model shows that the model presented in this paper is smooth.By comparing the experimental data of cemented structural soil with the model prediction, it is shown that the UH model of cemented structural soil can reasonably compress the structural soil in isotropic direction, one dimensional compression and conventional triaxial shear of drainage / undrained soil.The mechanical behaviors of isop drainage triaxial shear and true triaxial shear are predicted.
【学位授予单位】：北方工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU442

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