粉煤灰改良红层泥岩填料静三轴试验研究

Experimental Study on Static Triaxial Test of Fly Ash Modified Red Mudstone Filler

红层泥岩的吸水软化和体积膨胀特性易造成路基翻浆冒泥现象及路基不均匀沉降等病害,在作为公路路基填料时应对其进行改良。本文选用粉煤灰作为改良剂,通过室内X射线衍射试验、化学成分测试和易溶盐等试验,分析红层泥岩和粉煤灰的成分组成及离子含量;通过无侧限抗压强度试验、室内变水头渗透试验和固结等试验分析了试样改良前后物理力学特性;通过常规三轴UU试验,研究了不同粉煤灰掺量对改良试样剪切应力-应变及抗剪强度的影响;分析了粉煤灰掺量为10%时,养护龄期对改良试验抗剪强度参数的影响。结果表明:该地区红层泥岩属低液限黏土,其易溶盐溶液中的SO42-离子含量最高,pH值呈碱性;三轴剪切试验中,改良和未改良试样均呈塑性破坏,试样粉煤灰掺量和龄期均对试样抗剪强度提高具有促进作用,且黏聚力增长幅度远大于内摩擦角;粉煤灰掺量为10%龄期28 d时,试样黏聚力较未改良未养护试样和10%掺量未养护试样分别提升37.9%和6.9%,内摩擦角分别增大了1.2°和0.7°。试样的静力学试验均验证了粉煤灰改良的可靠性。

The water absorption and softening and volume expansion characteristics of the red mudstone are prone to cause the phenomenon of slurry mud and uneven settlement of the roadbed and other diseases,so it should be improved when used as highway roadbed filler.In this paper,fly ash was chosen as an improver to analyze the compositional composition and ionic content of red-bedded mudstone and fly ash through indoor X-ray diffraction tests,chemical composition tests and easily soluble salts.The physical and mechanical properties of the specimens before and after improvement were analyzed by unconfined compressive strength tests,indoor variable head penetration tests and consolidation tests.The effects of different fly ash admixtures on the shear stress-strain gauge shear strength of the modified specimens were investigated by conventional triaxial UU tests;the effects of the age of maintenance on the shear strength parameters of the modified tests when the fly ash admixture was 10%were analyzed.The results show that the red mudstone in the area is a low liquid-limit clay with the highest SO42-ion content and alkaline pH in its labile salt solution.In triaxial shear test,both modified and unmodified specimens showed plastic damage,and both the amount and age of fly ash admixture of the specimens contributed to the increase of shear strength of the specimens,and the increase of cohesion was much larger than the internal friction angle.The cohesive force of the specimens at the age of 28 d with 10%fly ash was 37.9%and 6.9%higher than that of the unmodified unmaintained specimens and 10%unmaintained specimens,respectively,and the internal friction angle increased by 1.2°and 0.7°.The hydrostatic experiments of the specimens all verified the reliability of the fly ash improvement.