电石渣-矿渣固化膨胀土强度及微观机制研究

Study on the strength and microscopic mechanism of calcium carbide slag-slag cured expansive soil

针对南水北调中线地区膨胀土因环境湿度变化引起力学特性劣化导致的工程地质灾变问题,采用电石渣、矿渣作为固化材料对膨胀土进行改良,通过素膨胀土和改良固化膨胀土无侧限抗压强度、劈裂抗拉强度和水稳性等对比试验,分析改良固化前后的性能差异;通过X射线衍射(X-ray diffraction,XRD)、电镜扫描(electron microscope scanning,SEM)、热重分析(thermogravimetric analysis,TGA)试验及核磁共振(nuclear magnetic resonance,NMR)试验分析了电石渣-矿渣固化土的强度增长机制,揭示其微观作用机制。结果表明:以6%电石渣掺量为基础,不同矿渣掺量下的电石渣-矿渣复合改性固化土,总体上强度和耐水性能均有明显提高,并在矿渣掺量为9%时达到最大值。而随着养护龄期的增加,无侧限抗压强度和劈裂抗拉强度不断增加,水稳系数则有所减小。电石渣-矿渣复合固化土水化生成的水化硅酸钙(C-S-H)和水化铝酸钙(C-A-H),胶结土颗粒形成了紧密的团聚体,有效改善了土体的孔结构分布,提高了固化土的强度。电石渣-矿渣膨胀土复合固化方法效果明显,具有较好的工程应用前景。

This study addresses the engineering geological disaster resulting from the degradation of mechanical properties of expansive soil due to changes in environmental humidity along the Middle Route of the South-to-North Water Transfer Project.Calcium carbide slag and slag are utilized as curing materials to improve the expansive soil.Comparative tests were conducted on the unconfined compressive strength,split tensile strength,and water stability of untreated and treated expansive soil to analyze the performance differences pre-and post-treatment.The strength enhancement mechanism of the calcium carbide slag-slag cured soil was investigated through the X-ray diffraction(XRD),electron microscope scanning(SEM),thermogravimetric analysis(TGA)test and nuclear magnetic resonance(NMR)test,revealing its microscopic mechanism of action.The results showed a significant increase in the overall strength and water resistance of the calcium carbide slag-slag composite modified cured soil with different slag dosage based on 6%dosage of calcium carbide slag,and a maximum value was reached when the slag dosage was 9%.Over time,the unconfined compressive strength and split tensile strength improved,while the water stability coefficient decreased notably.Hydration of calcium silicate hydrate(C-S-H)and calcium aluminate hydrate(C-A-H)generated by the hydration of calcium carbide slag-slag composite cured soil led to the formation of tightly bonded soil particles,enhancing the soil’s pore structure distribution and strength.The evident effectiveness of the composite curing method for calcium carbide slag-slag treated soil suggests promising engineering applications.