基于二元介质模型的高应力结构性黄土强度准则
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摘要
结构性黄土的力学性能、工程特性与重塑土有显著区别,特别是在高应力作用下黄土的结构性对抗剪强度的发挥有显著影响。因此基于陕北某高填方工程黄土地基,对原状黄土与重塑黄土进行了室内高围压固结排水三轴试验。通过分析原状与重塑黄土的应力应变曲线和偏应力差值曲线,研究了结构性黄土的强度变化机理,结果表明黄土在低围压下结构性强度迅速发挥,并随着围压的增大、胶结物质持续破坏,内摩阻力发挥开始逐渐增强;基于结构性岩土材料破损机理的二元介质模型,通过引入抗剪贡献率ξv,修正并建立了高应力下结构性黄土的抗剪强度准则;并与试验结果进行对比,表明该强度准则能够一定程度上反映出结构性黄土在不同围压作用下粘聚分量与摩擦分量分步发挥的内在机理。
The mechanical properties and geotechnical characteristics of structured loess and reconstituted loess are distinct in many aspects,especially the play of shear strength will be affected by loess structure characters under high stress.Therefore,based on a loess foundation of a high-fill project in northern Shaanxi,the consolidated drainage three-axis test of undisturbed loess and reconstituted loess under high confining pressure was carried out. And the strength behavior and mechanisms of structured soils were analyzed from the stress-strain curves and partial stress differential curve of undisturbed loess and reconstituted loess. The results show that the structural strength of loess is rapidly exerted under low pressure,then the internal friction begins to gradually develop with increasing confining pressure and the decomposing cementing substance; based on the geo-binary medium model considering the fracture mechanism of geomaterials,the strength criterion for structured loess under high stress is modified and established by introducing the parameter of shear resistance contribution ratio ξv. By comparisons of predictions with experimental data, it was demonstrated that the modified shear strength criterion could reflect the inherent playing mechanism of the cohesive component and friction component under different confining pressures.
The mechanical properties and geotechnical characteristics of structured loess and reconstituted loess are distinct in many aspects,especially the play of shear strength will be affected by loess structure characters under high stress.Therefore,based on a loess foundation of a high-fill project in northern Shaanxi,the consolidated drainage three-axis test of undisturbed loess and reconstituted loess under high confining pressure was carried out. And the strength behavior and mechanisms of structured soils were analyzed from the stress-strain curves and partial stress differential curve of undisturbed loess and reconstituted loess. The results show that the structural strength of loess is rapidly exerted under low pressure,then the internal friction begins to gradually develop with increasing confining pressure and the decomposing cementing substance; based on the geo-binary medium model considering the fracture mechanism of geomaterials,the strength criterion for structured loess under high stress is modified and established by introducing the parameter of shear resistance contribution ratio ξv. By comparisons of predictions with experimental data, it was demonstrated that the modified shear strength criterion could reflect the inherent playing mechanism of the cohesive component and friction component under different confining pressures.
引文
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[13] Wang J G,Leung C F,Ichicawa Y. A simplified homogenization method for composite soils[J]. Computers and Geotechnics,2002(29):477-500.
[14]刘恩龙,沈珠江.结构性土的强度准则[J].岩土工程学报,2006,28(10):1248-1252.
[15]刘恩龙,沈珠江.结构性土强度准则探讨[J].工程力学,2007,24(2):50-55.
[2] Mitchell J K. Fundamentals of soil behavior[M]. New York:Wiley,1993.
[3]胡再强,沈珠江,谢定义.结构性黄土的本构模型[J].岩石力学与工程学报,2005,24(4):565-569.
[4]俞茂宏.工程强度理论[M].北京:高等教育出版社,1999.
[5]胡海军,蒋明镜.引入离散元所得破损规律的结构性黄土本构模型[J].岩石力学与工程学报,2016,35(S1):3241-3248.
[6]邵生俊,陶虎,许萍.黄土结构性力学特性研究与应用的探讨[J].岩土力学,2011,32(S2):42-50.
[7]罗爱忠,邵生俊,陈昌禄,方娟.湿压剪条件下黄土的结构屈服与强度特性[J].地下空间与工程学报,2014,10(6):1243-1249.
[8]蒋明镜,胡海军,李涛.非饱和结构性黄土双轴湿陷试验的离散元分析[J].地下空间与工程学报,2016,12(4):1110-1116.
[9]沈珠江.岩土破损力学:理想脆弹塑性模型[J].岩土工程学报,2003,25(3):253-257.
[10] LAMBE T W. A mechanical picture of shear strength in clay[C]//Research Conference on Shear Strength of Cohesive Soils, University of Colorado, Boulder, Colorado, 1960:555-580.
[11]沈珠江,胡再强.黄土的二元介质模型[J].水利学报,2003,25(7):1-6.
[12]刘恩龙.岩土破损力学结构块破损机制与二元介质模型[J].岩土力学,2010,31(S1):13-22.
[13] Wang J G,Leung C F,Ichicawa Y. A simplified homogenization method for composite soils[J]. Computers and Geotechnics,2002(29):477-500.
[14]刘恩龙,沈珠江.结构性土的强度准则[J].岩土工程学报,2006,28(10):1248-1252.
[15]刘恩龙,沈珠江.结构性土强度准则探讨[J].工程力学,2007,24(2):50-55.