岩土类材料的静水压力效应

EFFECT OF HYDROSTATIC PRESSURE ON GEOMATERIALS

岩土类材料的抗剪强度主要包括黏聚强度和摩擦强度,由材料颗粒间的黏聚力、摩擦力及颗粒的破碎提供,受静水压力的影响显著。分析材料在不同静水压力下2种强度的发挥机制,及材料颗粒破碎对抗剪强度的影响规律,阐述了岩土类材料静水压力效应产生的机制:低静水压力下,材料组分间的相互错动导致材料的破坏,表现为剪应力比破坏;高静水压力下,材料组分破碎导致材料的破坏,表现为剪应力破坏。采用三轴压缩子午面上的破坏函数发展了非线性统一强度模型,使其不仅能够合理地反映材料的中主应力效应,而且能更好地描述材料的静水压力效应,即抗剪强度与剪切滑动面上正应力之间的非线性关系。利用国内外取得的试验数据验证发展后的非线性统一强度模型,表明可合理地反映岩土类材料的静水压力效应,及复杂应力条件下岩土类材料的三维非线性强度特性。

Shear strength of geomaterials including cohesive strength and frictional strength is significantly influenced by the hydrostatic pressure. The shear strength is provided by cohesive force,frictional force between granules and the crush of granules. Roles of cohesive strength and frictional strength played under different hydrostatic pressures were analyzed,and the shear strength property influenced by the crush of granules was also studied,then the mechanism of hydrostatic pressure effect was expounded. When the material was under a low hydrostatic pressure,the mutual movement of granules resulted in the failure of geomaterials,which exhibited the shear stress ratio failure characteristics. When the material was under a high hydrostatic pressure,the crush of granules resulted in the failure of geomaterials,which exhibited the shear stress failure characteristics. The failure function in meridian plane of triaxial compression was used to revise the nonlinear unified strength model. The revised nonlinear unified strength model described not only the effect of intermediate principle stress,but also the effect of hydrostatic pressure on geomaterials more reasonably. Compared with the data from a number of true triaxial tests,the revised nonlinear unified strength model was shown to describe well the hydrostatic pressure effect and 3D nonlinear strength properties under multiaxial stress conditions of different materials.