基于大型直剪的砂土及其筋土界面剪胀性研究

Interface Stress-dilation Analysis of Sand with Large Scale Shear Test

采用大型直剪仪,对三向土工格栅加筋北京地区砂土的界面剪胀特性进行了试验研究,通过大型直剪试验模拟砂土加筋时的剪切作用过程,得出了以下结论:1砂土在剪切过程中都是由短暂的剪缩效应发展为稳定的剪胀效应;2在低含水率时砂土的剪胀效应较明显,随着含水率的增加,剪胀效应有一个先降低后升高的过程,当含水率增大到12%且竖向应力为215~323k Pa时,砂土的剪胀效应会超过含水率为2.5%时的剪胀效应;3当竖向压力小,砂土较为松散时,砂土基本没有剪胀效应,但是随着竖向压力的增大,砂土的剪胀效应经历从无到有并且是先升高后降低的过程。当竖向应力在215~323k Pa时剪胀效应最显著;4格栅加筋可以降低砂土的剪胀效应,并且压力越大降低效果越明显。

An experimental investigation was conducted to study the dilatancy effect of the sand interface reinforced by three-directional geotechnical grille in Beijing area,adopting large-scale direct shear apparatus. By experiments using large-scale direct shear apparatus and simulating the shearing process during the sand reinforced,conclusions are drawn as follows: During shearing,the short shear compression effect of the sand develops into stable shear dilatancy effect; dilatancy effect of the sand at low moisture content is obvious,with the increase of the moisture content,dilatancy effect decreases first,then it increases; when the water content increases to a certain amount,dilatancy effect can exceed itself—the one at low moisture content; when the vertical pressure is small and the sand is relatively loose,the sand almost shows no dilatancy effect,but as it increases,the dilatancy effect of the sand also increases,but then it decreases; grill reinforce can slowdown the dilatancy effect of sand,and the greater the pressure is,the more obvious the effect will be.