土工布与砂土界面循环剪切动力特性

Cyclic shear dynamic properties of geotextile-sandy soil interfaces

利用室内大型循环直剪仪进行了一系列筋土界面循环剪切试验,筋材采用土工编织布和无纺土工布,土体采用中国ISO标准砂,在竖向应力分别为30、60、90kPa,剪切位移幅值分别为1、3、5mm,砂土密实度分别为22%、52%、75%时,研究了竖向应力、剪切位移幅值、砂土密实度对筋土界面循环剪切特性的影响,分析了循环剪切过程中2种土工布与砂土界面的剪切应力峰值和剪切应力-剪切位移的变化规律。研究结果表明:2种土工布与砂土界面均会发生循环剪切软化现象,但软化规律不同;竖向应力从30kPa增大到90kPa时,土工编织布与砂土界面循环剪切应力峰值增大了72.9%,无纺土工布与砂土界面循环剪切应力峰值增加了167.5%,表明竖向应力对土工编织布与砂土界面的循环剪切特性影响明显;剪切位移幅值分别为1、3、5mm时,土工编织布与砂土界面剪切应力峰值分别为25.9、27.9、29.8kPa,无纺土工布与砂土界面剪切应力峰值分别为21.8、23.8、22.6kPa,表明随着剪切位移幅值增大,土工编织布与砂土界面剪切应力峰值随之增大,而无纺土工布与砂土界面剪切应力峰值先增大后减小;在3种砂土密实度下,土工编织布与砂土界面剪切应力峰值之间的最大差值不超过2kPa,无纺土工布与砂土界面剪切应力峰值之间的最大差值不超过3kPa,表明砂土密实度对2种土工布与砂土界面的循环剪切特性影响不明显。

A series of cyclic direct shear tests of soil-reinforcement interfaces were performed by using a large-scale direct shear device.Woven geotextile and nonwoven geotextile were used as reinforcement materials.Chinese ISO standard sand was used as soil mass.When the vertical stresses are 30,60 and 90kPa respectively,the cyclic shear displacement amplitudes are 1,3and5 mm respectively,and the sandy soil densities are 22%,52% and 75% respectively,theirinfluences on the cyclic shear properties of soil-reinforcement interfaces were studied,and the development laws of peak shear stresses and the relationships of shear stresses and shear displacements in the processes of cyclic shear tests on two kinds of geotextile-sandy soil interfaces were analyzed.Study result indicates that the cyclic shear softening phenomena appear on woven/nonwoven geotextile-sand interfaces,and the softening laws are different.When the vertical stress increases from 30 kPa to 90 kPa,the peak shear stress of woven geotextile-sandy soil interface increases by 72.9%,and the peak shear stress of nonwoven geotextile-sand interface increases by 167.5%,so the influence of vertical stress on the cyclic shear properties of geotextile-sandy soil interface is obvious.When the shear displacement amplitudes are 1,3and5 mm respectively,the peak shear stresses of woven geotextile-sandy soil interface are 25.9,27.9and 29.8kPa respectively,and the peak shear stresses of nonwoven geotextile-sandy soil interface are 21.8,23.8and 22.6kPa respectively,which shows that the peak shear stress of woven geotextile-sandy soil interface increases with the increase of shear displacement amplitude,while the peak shear stress of nonwoven geotextile-sandy soil interface firstly increases and then decreases.Under the three sandy soil densities,the differences among the peak shear stresses of woven geotextile-sandy soil interface do not exceed 2kPa,and the differences among the peak shear stresses of nonwoven geotextile-sandy soil interface do not exceed 3kPa,which shows that the sandy soil density has no significant influence on the cyclic shear properties of woven/nonwoven geotextile-sandy soil interfaces.