掺砂粒径分布对泥质粉砂岩填料抗剪特性的影响

Influence of Particle Size Distribution on Shear Properties of Argillaceous Siltstone Fillers

掺入不同粒径硬岩颗粒是软岩地层填方区改良软岩填料抗剪特性的重要方法。设定同粒径级配与单一粒径2类改良方式共32组试验,对比改良前后土料剪应力-剪切位移曲线,得到土料峰值剪切强度、破坏强度、粘聚力及内摩擦角等抗剪参数变化规律。试验结果表明,低应力条件下泥质粉砂岩土料受剪切作用而存在应变软化现象;掺入同级配砂粒后泥质粉砂岩土料内摩擦角随掺砂比例增加呈逐渐增大趋势,粘聚力先减小后缓慢增大;法向应力200、300kPa时,单一粒径替换后土料峰值剪切应力随掺砂中值粒径增加而缓慢增大并趋于稳定,内摩擦角随中值粒径值增大呈急剧上升后缓慢降低,在0.75 mm处取得极值;粘聚力呈先减小后逐渐增大趋势。可见采用粘聚力及内摩擦角等参数评估掺砂改良泥质粉砂岩土料抗剪特性时需注意粒径分布所引起的强度参数变化。

The mixture of hard rock particles with different particle sizes is an important method for improving the shear characteristics of soft rock fillers in soft rock stratum. Two improved methods, which were mixing with the same gradation curve and the single range of particle size, were set up a total of 32 groups separately. Then, the shear stress displacement curves of the soil before and after improvement were compared, and the variation law of shear strength, failure strength, cohesive force and internal friction angle were obtained. Test results show that the phenomenon of strain softening exists in the shear process of argillaceous siltstone fillers under the condition of low stress. The internal friction angle of fillers gradually increases with the increase of the proportion of sandstone particles, and the cohesive force decreases firstly and then increases slowly. Peak shear stress increases slowly and tends to be stable with the increase of the median particle size when the fills mixing with single range of particle size under the normal stress of 200 kPa and 300 kPa. The internal friction angle increases sharply and then decreases slowly, and reaches the extremum at 0.75 mm. Cohesion decreases firstly and then increases. Therefore, attention should be paid to the change of strength parameters caused by particle size distribution when evaluating the shear properties of the improved argillaceous siltstone fillers by means of cohesion and internal friction angle.