考虑吸力变化的非饱和高液限黏土-土工织物界面剪切特性研究

Study of interface shear characteristic between unsaturated high liquid limit clay and geotextiles considering suction change

以高液限土为填料的加筋挡墙广泛在南方地区应用,加筋挡墙土体吸力经常随气候变化而发生变化,直接影响筋土界面强度特性,考虑吸力变化的非饱和高液限黏土-土工织物界面强度特性亟待深入研究。利用ZFY-1A型非饱和土应变控制式直剪仪对非饱和高液限黏土-土工织物界面进行控制吸力的剪切试验,探讨吸力循环变化(干湿循环)对筋-土界面剪切特性的影响。研究表明,高液限黏土-土工织物界面的抗剪强度随着净法向应力的增加而增大;随着循环次数的增加,界面强度呈现先升高而后衰减的变化规律。经历3次干湿循环的界面强度低于未经历干湿循环的强度。随着循环次数的增加,界面强度总体上呈降低趋势。吸力增加的速率b?随吸力循环次数的增加先增大后减小,有效界面摩擦角??、界面有效黏聚力ac?、界面综合摩擦系数f?、综合摩擦系数比K与此类似。max?w含水率变化量的最大值随着净法向应力、循环次数的增加而增大。最大剪胀量max(h H)随循环次数的增加先增大后减小,随净法向应力的增大而减小。最后通过对数拟合,得出经历若干次基质吸力循环后的界面强度计算公式。

In South China, the geosynthetic reinforced retaining wall using high liquid limit soil as backfill is applied widely. Because of climate change, the suction between unsaturated high liquid limit clay and geotextile is altering; thus influencing the interface shear characteristic. So the interface shear characteristic between unsaturated high clay and geotextile considering suction change should be studied deeply. In this paper, a series of direct shear tests are performed using ZFY-1A direct shear apparatus to investigate the shearing resistance properties of high plasticity clay-geotextile interface under suction cycle. Results of experiment indicate that the peak shear strength of the soil-geotextile interface increases with the net normal stress. Interface strength increases at first and then reduces with the increase of cycling times, interface strength is lowest through 3 times of the dry-wet circulation. And interface strength is reduced in general. δb, δ＇, ca＇, f＇ and K increase and then decrease with the increase of cycling times. △wmax increases with the cycling times and net normal stress. （h/H）max decreases with net normal stress, and increases then decreases with the increase of cycling times. Finally, the interface strength formula under different suction conditions is obtained through the logarithmic fitting.