饱和粉砂不稳定性的试验研究

Laboratory study of the instability of saturated silty sand

通过对净砂和级配良好粉砂(含10%粉土)进行一系列三轴固结不排水试验(CU),研究了粉土、孔隙比和围压对饱和粉砂不稳定性的影响。试验结果表明,净砂与粉砂在不排水剪切条件下均会出现应变软化现象(即不稳定性)。同一围压下脆性指数(IB)随孔隙比增加,但不稳定线的应力比随孔隙比增加而减小。引用等效粒间孔隙比(ege)后,净砂和粉砂在ege-ln p′平面上拥有基本相同的临界状态线。在临界状态理论及等效粒间孔隙比的基础上,提出在同一修正状态参数(ψge)下净砂和级配良好粉砂有相似的不稳定性。

A series of isotropically consolidated undrained triaxial tests （CU） were conducted on a clean sand and a well-graded silty sand （with 10 % silt content） to investigate the effect of silt, void ratio and confining stress on the instability of saturated sands. The test results show that both clean sand and well-graded silty sand exhibit strain softening characteristics under undrained condition （i.e. instability）. Under the same confining pressure, the brittleness index increases with increasing void ratio, but the stress ratio of the instability line decreases with increasing void ratio. If equivalent intergranular void ratio （ege） is used to interpret the critical state data of the silty sand, clean sand and silty sand possess similar critical state line in ege-ln p＇ plane. Based on the critical state theory and equivalent intergranular void ratio, clean sand and well-graded silty sand exhibits similar instability under the same modified state parameter （ψge）.