加筋红砂岩力学特性研究

Study of mechanical properties of reinforced red sandstone

为改变传统红砂岩由于强度低无法作为高速公路路基填料的现状,将红砂岩与土工格栅及格宾组合形成加筋土,探究加筋条件下的力学特性。采用粗粒土三轴剪切仪,进行0层、2层、3层水平铺筋条件下的不排水剪切试验,并引入强度比参数对加筋效果进行定量评价。试验结果表明:当轴向应变小于2%时,加筋土的强度没有明显变化,轴向应变继续增大,加筋土强度逐渐超过纯土样,在400 kPa围压时大主应力差提高了50%;相同层数的格宾加筋强度普遍高于格栅加筋,其加筋效果系数均在1.39以上;筋材能明显提高红砂岩的峰值强度和土体延性,使红砂岩的黏聚力最大提高149%,摩擦角最大提高15.32%。采用邓肯-张模型和离散元模拟对加筋土的力学性质进行评估,为加筋土力学评价体系的建立提供参考。

In order to change the current situation that the traditional red sandstone can not be used as expressway subgrade filler due to its low strength,red sandstone was combined with geogrid and Gabion to form reinforced soil,and the mechanical properties under reinforced conditions were explored.The undrained shear tests of 0,2 and 3 layers of horizontal reinforcement are carried out by using coarse-grained soil triaxial shear instrument,and the strength ratio parameter is introduced to quantitatively evaluate the reinforcement effect.The test results show that when the axial strain is less than 2%,the strength of reinforced soil does not change significantly,the axial strain continues to increase,the strength of reinforced soil gradually exceeds that of pure soil sample,and the large principal stress difference increases by 50%at the confining pressure of 400 kPa.The quantitative analysis of reinforcement effect shows that under the same confining pressure,the reinforcement strength of gabion with the same number of layers is generally higher than that of grid reinforcement,and the reinforcement effect coefficient is more than 1.39;the reinforced material can significantly improve the peak strength and soil ductility of the red sandstone,resulting in a maximum increase of 149%in the cohesion of the red sandstone,but only a maximum increase of 15.32%in the friction angle.Finally,the Duncan-Zhang model and discrete element simulation were used to evaluate the mechanical properties of the reinforced soil,providing a reference for the establishment of the reinforced soil mechanical evaluation system.