CONSTITUTIVE MODEL FOR K0 OVERCONSOLIDATED STRUCTURE CLAY
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摘要: K0固结黏土在自然界广泛分布, 其通常同时具有超固结性与天然结构性, 而K0超固结性又与K0正常固结性质存在很大差异. 为了有效的描述K0超固结性质, 在结构性模型基础上, 做了如下三点改进, 使得原模型拓展为同时考虑K0超固结特性与天然结构性影响的本构模型. (1)引入相对应力比来描述屈服面, 并引入初始各向异性转轴参量ξ来表达初始各向异性对屈服面在p-q空间的位置影响. (2)基于给定的屈服面方程, 推导得到变相应力比参量, 并将变相应力比引入到统一硬化参数中, 利用统一硬化参数可以有效描述初始各向异性固结黏土在剪切加载下的剪缩与剪胀, 应变硬化及软化现象. (3)引入反映结构性胶结强度性质的胶结参量pe, 并给出pe随塑性偏应变的衰减演化方程, 利用胶结参量可描述结构性黏土的剪胀特性. 预测与试验结果对比表明, 所提的K0超固结结构性模型可有效描述K0超固结黏土的刚度提高效应, 黏土的包辛格效应, 结构性黏土胶结强度的损失现象以及结构性黏土的应变软化现象. 证明了所提模型的适用性以及合理性.Abstract: K0 consolidated clay is widely distributed in nature. It usually has both overconsolidation property and natural structural property, and it is a significant difference for the property of overconsolidation of K0 to the normal consolidation of K0 clay. In order to effectively describe the overconsolidation properties of K0 consolidated clay, three improvements were made on the basis of the natural structure consolidated model for clay, so that the original model can be extended to a constitutive model that consider both the properties of K0 overconsolidation clay and the effects of natural structures for natural clay. (1) The relative stress ratio is introduced into the yield surface equation to describe the yield property, and the initial anisotropic consolidation stress ratio parameter ξ is introduced into the yield surface equation to express the influence of the initial anisotropy on the position of the yield surface in p-q space. (2) Based on the given yield surface equation, the phase transformation stress ratio parameter was derived, and the phase transformation stress ratio was introduced into the unified hardening parameter. The unified hardening parameter can effectively describe both the initial anisotropic shearing behavior and the dilatancy behavior, strain hardening and softening phenomenon for initial anisotropic consolidated clay. (3) The cementation parameter pe, which reflects the structural cementation, is introduced into the yield surface equation and the decay evolution equation of pe with deviatoric plastic strain is given. The dilatancy properties of structural clay can be described by using the cementation parameter. The comparison between the prediction and the test results shows that the proposed K0 consolidation model can effectively describe the stiffness enhancement effect of K0 overconsolidated clay, the Bauschinger effect of clay, the cementation strength loss phenomenon and the strain softening phenomenon of structural clay. The applicability and rationality of the proposed model are proved.
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Key words:
- structure /
- overconsolidated clay /
- dilatancy /
- strain softening /
- cementation strength
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图 1 p-q空间中的当前屈服面(px0)与结构性屈服面(p*x0)及参考屈服面(
$ {\bar p_{x0}} $ )Figure 1. Current yield surface(px0), structural yield surface(p*x0) and reference yield surface(
$ {\bar p_{x0}} $ ) in p-q space
图 2 结构性与重塑土剪胀曲线对比图
Figure 2. Comparison of shear dilatancy between structural and remolded soils
图 4 等方向固结下不同状态参量χ影响下的剪胀关系曲线
Figure 4. The dilatancy curves under the influence of different state parameters χ with isotropic consolidation
图 5 不同水泥含量模拟结构性黏土三轴不排水剪切的有效应力路径试验曲线
Figure 5. Effective stress paths test curves of structural clay under triaxial undrained shear with different cement contents
图 6 典型加载路径下应力比与偏应变关系曲线
Figure 6. Relationship curve between stress ratioes and deviatoric strain under typical loading path
图 7 e-p空间中Pappadai黏土一维压缩测试与预测对比结果
Figure 7. Comparison of one-dimensional compression test and prediction results of Pappadai clay in e-p space
图 8 e-p空间中三种水泥含量黏土的一维压缩测试与预测对比结果
Figure 8. One-dimensional compression test and prediction results of three kinds of clay with cement content in e-p space
图 9 常规三轴压缩下Pappadai黏土的应力比与偏应变测试与预测结果对比
Figure 9. Comparison of prediction and test results of stress ratio versus deviatoric strain for Pappadai clay under conventional triaxial compression
图 10 常规三轴压缩下Pappadai黏土的体应变与偏应变测试与预测结果对比
Figure 10. Comparison of prediction and test results of volume strain versus deviatoric strain for Pappadai clay under conventional triaxial compression
图 11 常规三轴不排水剪切加载下Pappadai黏土的偏应力与偏应变测试与预测对比
Figure 11. Comparison of prediction and test results of deviatoric stress versus deviatoric strain for Pappadai clay under conventional undrained triaxial compression
图 12 常规三轴不排水剪切加载下Pappadai黏土的孔隙水压力与偏应变测试与预测对比
Figure 12. Comparison of prediction and test results of pore water pressure versus deviatoric strain for Pappadai clay under conventional undrained triaxial compression
图 13 常规三轴不排水剪切加载下Ariake黏土的偏应力与偏应变测试与预测对比
Figure 13. Comparison of prediction and test results of deviatoric stress versus deviatoric strain for Ariake clay under conventional undrained triaxial compression
图 14 常规三轴不排水剪切加载下Ariake黏土的孔隙水压力与偏应变测试与预测对比
Figure 14. Comparison of prediction and test results of pore water pressure versus deviatoric strain for Ariake clay under conventional undrained triaxial compression
图 15 小围压下常规三轴不排水剪切Ariake黏土的偏应力与偏应变测试与预测对比
Figure 15. Comparison of prediction and test results of deviatoric stress versus deviatoric strain for Ariake clay under conventional undrained triaxial compression with lower confining pressure
图 16 小围压下常规三轴不排水剪切Ariake黏土的孔隙水压力与偏应变测试与预测对比
Figure 16. Comparison of prediction and test results of pore water pressure versus deviatoric strain for Ariake clay under conventional undrained triaxial compression with lower confining pressure
图 17 等方向固结LCT黏土三轴压缩下偏应力与轴应变测试及预测对比
Figure 17. Comparison of prediction and test results of deviatoric stress versus axial strain for isotropic consolidated LCT clay under conventional triaxial compression
图 18 等方向固结LCT黏土三轴压缩下体应变与轴应变测试及预测对比
Figure 18. Comparison of prediction and test results of volume strain versus axial strain for isotropic consolidated LCT clay under conventional triaxial compression
图 19 K0固结LCT黏土三轴压缩下偏应力与轴应变测试及预测对比
Figure 19. Comparison of prediction and test results of deviatoric stress versus axial strain for K0 consolidated LCT clay under conventional triaxial compression
图 20 K0固结LCT黏土三轴压缩下体应变与轴应变测试及预测对比
Figure 20. Comparison of prediction and test results of volume strain versus axial strain for isotropic consolidated LCT clay under conventional triaxial compression
图 21 纯黑黏土常规三轴压缩下偏应力与轴应变测试及预测对比
Figure 21. Comparison of prediction and test results of deviatoric stress versus axial strain for isotropic consolidated pure black clay under conventional triaxial compression
图 22 纯黑黏土常规三轴压缩下孔隙比与轴应变测试及预测对比
Figure 22. Comparison of prediction and test results of void ratio versus axial strain for isotropic consolidated pure black clay under conventional triaxial compression
表 1 黏土材料参数
Table 1. Material parameters for clay
Clay type Ms λ κ ζ ω pe(MPa) Pm(MPa) Pi(MPa) α Pappadai 1.3 0.39 0.015 1.5 0 2.8 0.012 0.3 0 Cement clay1 1.3 0.93 0.12 1.5 0 0.08 0.002 0.05 0 Cement clay2 1.3 0.98 0.02 1.5 0 0.3 0.002 0.13 0 Cement clay3 1.3 1.18 0.011 1.5 0 3.5 0.002 1.5 0 Ariake 1.26 0.22 0.01 1.5 0.5 3.06 0.002 0.13 0.3 LCT 1.1 0.56 0.01 1.5 1 0.06 0.01 0.02 0.01 Pure black 0.85 0.13 0.02 0 1 0.001 0.001 0.01 0.3 
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