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针对循环剪切作用对Sandwich形加筋土界面剪切特性影响研究不足的状况,采用室内大型直剪仪对Sandwich形加筋土进行了一系列循环直剪试验。试验所用的筋材为土工格栅,砂为福建标准砂,黏土为含水率为28%的重塑黏土,分别在竖向应力为30,60,90kPa,剪切位移幅值为3,6,9mm,剪切速率为1,2,5,10mm·min~(-1),薄砂层厚度分别为4,6,8,10,12,14mm时,研究了剪切速率、薄砂层厚度、循环剪切幅值和竖向应力等因素对Sandwich形加筋土筋土界面循环剪切特性的影响。试验结果表明:在薄砂层厚度由2mm增加到14mm的过程中,界面的峰值剪应力呈现出先增大后减小的现象,峰值剪应力先由54.3kPa增加到67.9kPa,然后又减小到59.4kPa,薄砂层厚度为8mm时筋土界面峰值剪应力达到最大值67.9kPa;当剪切速率为1 mm·min~(-1)时,筋土界面主要表现出剪切硬化现象,且在前几个循环周次,峰值剪应力增幅较大,随着循环周次的增加,增幅逐渐减小;当剪切速率大于1 mm·min~(-1)时,筋土界面表现出剪切软化现象,且剪切速率越大,软化现象越明显;在剪切幅值从3mm增加到9mm的过程中,循环剪切时筋土界面的剪胀、剪缩交替现象越来越明显,并且剪切幅值越大,界面最终剪缩量也越大;竖向应力为30,60,90,120kPa时,筋土界面对应的峰值剪应力分别为32.6,43.2,60.4,82.9kPa,表明随着竖向应力的增加,筋土界面的峰值剪应力也随之增加。
Aiming at the lack of research on the influence of cyclic shear on the shear characteristics of Sandwich reinforced earth interface, a series of direct shear tests were carried out on the Sandwich reinforced earth using a large indoor direct shear instrument. The geogrid used in the experiment was geogrid, the sand was Fujian standard sand, and the clay was remolded clay with moisture content of 28%. When the vertical stress was 30,60,90kPa and the shear displacement amplitude was 3,6, 9mm, shear rate of 1, 2, 5, 10mm · min ~ (-1), thin sand layer thickness of 4,6,8,10,12,14mm, the shear rate, the thickness of thin sand , The effect of cyclic shear amplitude and vertical stress on the cyclic shear characteristics of Sandwich reinforced earth reinforcement. The experimental results show that the peak shear stress of the interface increases first and then decreases when the thickness of sand layer is increased from 2mm to 14mm, the peak shear stress increases from 54.3kPa to 67.9kPa and then decreases to 59.4 kPa. The peak shear stress at the interface of soil and reinforcement reaches 67.9 kPa when the thickness of sand layer is 8 mm. When the shear rate is 1 mm · min ~ (-1), the interface of soil and reinforcement mainly shows shear hardening, and In the first few cycles, the peak shear stress increases more greatly, and decreases with the increase of the number of cycles. When the shear rate is more than 1 mm · min -1, Softening phenomenon is more obvious. In the process of increasing the shear amplitude from 3mm to 9mm, the phenomenon of dilatancy and alternate shear-shrinkage at the soil-soil interface during cyclic shear is more and more obvious. And the greater the shear amplitude, the greater the final shear and shear of the interface; the peak shear stress corresponding to the interface of the soil and the soil when the vertical stress is 30, 60, 90 and 120 kPa respectively is 32.6, 43.2, 60.4 and 82.9 kPa, With the increase of vertical stress, the peak shear stress at the soil-soil interface also increases.