不同颗粒级配钙质砂剪切特性研究

为研究钙质砂剪切特性,对某岛钙质砂进行4组固结排水三轴试验,其围压分别是50、100、200、400 kPa。应力应变曲线表明钙质砂体变先剪缩后剪胀,在剪胀发展的过程中伴随应变软化现象。为进一步探究钙质砂应变软化的原因,筛除粒径小于0.5 mm,重复试验。研究结果表明大颗粒的钙质砂并没有出现应变软化现象。给出如下结论:(1)应变软化出现的位置比较偏后,且随着围压的增长,峰值强度会逐渐后移;(2)在低围压条件下钙质砂颗粒破碎诱发的应变软化可能性低;(3)细小颗粒诱发扁平状钙质砂出现定向滑移是试样表现应变软化的关键因素;(4)围压越高细小颗粒诱发应变软化的难度越大,峰值强度逐渐后移,并伴随着剪切带的出现。

Experimental research on shear behavior of different particle gradation of calcareous sand

Four consolidated drained triaxial tests of an island calcareous sand were carried out to research its shear behavior,the confining pressure was 50 kPa,100 kPa,200 kPa and 400 kPa respectively. The stress and strain curves show that the calcareous sand body is shrinkage and dilatancy in turn,accompanied by the phenomenon of strain softening during the development of dilatancy. In order to further explore the reason of the strain softening of calcareous sand,then,particles smaller than 0.5mm are removed and the tests are repeated. The results show that there is no strain softening phenomenon in the calcareous sand of large particles. This paper convinces that:(1) the position of strain softening occurs relatively later,and with the increase of confining pressure,the position of the peak strength will gradually move backward;(2) the possibility of strain softening induced by particle breakage of calcareous sand under low confining pressure is very low;(3) fine particles are the key factors to induce the directional slip of flat calcareous sand;(4) the higher the confining pressure is, the higher the difficulty of the strain softening is,the peak strength is move backward gradually, accompanied by the appearance of the shear band.