土工布加筋粗颗粒土变形与强度特性试验研究

Experimental Study on Deformation and Strength Behavior of Geotextile Reinforced Coarse-grained Soil

对不同土工布加筋层数的粗颗粒土试样进行常规三轴固结排水剪切试验,探讨试样加筋层数(简称筋数n=0～3)对粗颗粒土变形、强度特性的影响。结果表明:筋数n每增加1,不同围压下试样破坏时的轴向应变增大0.91%～2.00%,土体韧性增强,筋材可抑制试样的侧向变形;不同围压下,平均筋数n每增加1,试样变形模量增大5 378 kPa。加筋能够增大相变时的体积应变;在p–q平面内,同一筋数n下的相变点和破坏点均可用直线拟合。粗颗粒土的强度指标总体随筋数的增加而增大。对线性指标c和非线性指标φ0、Δφ,其随试样筋数n的变化均可近似用直线表示;n每增加1,内摩擦角φ′增大1.75°。最后提出一个方便表述加筋量多少的指标—加筋疏密指数IR,并给出三轴试验获得IR的方法。整理发现试样黏聚力c及准黏聚力Δc(加筋土比素土黏聚力的提高量)与IR均可用直线拟合;IR每增加1 m–1,c和Δc分别提高9.1和13.5 kPa。利用该参数对三轴试验下砂土、黏土和粗颗粒土加筋对其强度提高的效果进行总结分析,加筋对不同土c提高量差异显著,IR每增加1 m–1,砂土、黏土和粗颗粒土c分别提高0.07、0.50和8.75 kPa。基于准黏聚力原理,建立c及Δc与IR的关系,可根据该公式直接估计土体加筋后的黏聚力或准黏聚力。

The influences of geotextile reinforcement layer number n on the deformation and strength properties of coarse-grained soil were investigated by using the consolidated-drained triaxial compression tests on the samples with different n(n=0~3).The experimental results showed that the axial strain at failure increases by 0.91%~2.00%under different confining pressures,with the increment of n of 1,indicating the improvement of toughness.The geotextile could inhibit the lateral deformation of soil samples.The deformation modulus increased averagely by 5 378 kPa with the increment of n of 1 under different confining pressures.The reinforcement could increase the volumetric strain at phase transition.Both points at phase transition and at failure with the same n could be fitted by lines in p–q plane.The strength indexes increased with the increase of n generally.With respect to the linear index c and nonlinear indexes such asφ0 andΔφ,its relationship with n was approximately linear,and the internal friction angle increased by 1.75 degrees with the increment of n of 1.Finally,the index of reinforcement IR was put forward by considering the description of the quantity of reinforcement conveniently,and the method to obtain IR by triaxial shear test was given.It was found that the relationships between cohesion c,pseudo-cohesionΔc(cohesion increment of reinforced earth)and IR could be fitted by lines,and with the increment of IR of 1 m–1,c andΔc increased by 9.1 kPa and 13.5 kPa,respectively.Using this parameter IR,the effect of strength increase to sands,clay and coarse-grained soil under triaxial test was analyzed and summarized.There were significant differences on the cohesion increment among these soils,where the c for sands,clay and coarse-grained soil increased by 0.07,0.50 and 8.75 kPa with the increment of IR of 1 m–1.Based on the pseudo-cohesion principle,the relationships between c,Δc and IR were established,which can be used to evaluate c andΔc of reinforced earth directly.