不同水饱和度充填体力学性能及损伤机制研究

Mechanical properties and damage mechanism of backfill with different water saturation

注浆充填被广泛应用于提升岩溶区溶洞的工程稳定性,充填体力学性能直接影响工程建设及服役安全性。采用单轴抗压强度试验机、压汞仪和扫描电镜针对不同含水饱和度石灰石尾矿基充填体的力学特性和损伤机制进行了系统研究。结果表明:随着饱和度增加,充填体抗压强度先提高后减小,饱和度为75%时,抗压强度最优,养护龄期为28 d时抗压强度可达6.8 MPa。微观分析可知,充填体水化产物为无定形凝胶(C-S-H凝胶、N-C-S-A-H凝胶)、钙矾石和未反应的石灰石尾矿颗粒,含水饱和度为75%时,内部结构最致密。基于充填体的应力-应变关系,描述了单轴压缩条件下不同饱和度充填体的变形过程,随着饱和度的增加,充填体破坏模式由剪切破坏转变为拉伸破坏。因此,建立了不同饱和度充填体的损伤本构模型,为岩溶充填工程的设计及服役性能评判提供可靠依据。

Grouting filling is widely used to improve engineering stability in karst areas and mechanical properties of filling body directly affect engineering construction and service safety.Mechanical properties and damage mechanism of fillings with different water saturation were systematically studied with uniaxial compressive strength testing machine,mercury porosimeter,and scanning electron microscope.The results have shown that compressive strength of backfill body increases first and then decreases with the increase of water saturation.When water saturation is 75%,compressive strength is best and compressive strength can reach 6.8 MPa when curing age is 28 days.Microscopic analysis has shown that hydration products of backfill body are amorphous gel(C-S-H gel,N-C-S-A-H gel),ettringite,and unreacted limestone tailings particles.The internal structure is densest under the condition of 75%water saturation.Based on stress-strain relationship of limestone tailings-based backfill,deformation process of backfill with different water saturation under uniaxial compression was described,the failure mode of backfill changes from shear failure to tensile failure with the increase of water saturation.Therefore,damage constitutive models of different saturation fillings were established,which provides reliable basis for design and service performance evaluation of karst filling engineering.