冻融作用下纤维加筋固化盐渍土的抗压性能与微观结构

冬季冻结与春季融化引起北方滨海盐渍土的工程性质劣化。为研究纤维加筋对固化土的抗压性能、抗冻融性能与微观结构变化，开展了石灰固化盐渍土和纤维与石灰加筋固化盐渍土的冻融试验、无侧限抗压试验、扫描电镜试验、核磁共振试验和压汞试验，系统分析冻融后纤维加筋固化盐渍土的抗压强度与孔隙特征间的相关性、抗冻融性能及其变化规律。结果表明：随冻融次数增加，石灰固化土和纤维与石灰加筋固化土的抗压强度、孔隙体积、孔隙率均呈阶段性变化，即冻融1~3次、冻融4~7次、冻融8~10次、冻融11~15次共4个阶段。随冻融次数增加，破坏应变增大。相同冻融次数下，2种土的破坏应变均随压实度的增大而增大，且纤维与石灰加筋固化土的抗压强度、破坏应变均大于石灰固化土，孔隙率则反之。加筋土越密实，筋土摩擦作用越强，土的抗压性能越好；纤维在土中随机分布与交织分布，对土起到了空间约束作用，提高了加筋土的抗冻融性能。研究成果可为北方盐渍土的工程利用提供理论和技术指导。

Compressive properties and microstructure of saline soil added fiber and lime under freezing-thawing cycles

Freezing in winter and thawing in spring lead to deterioration of the engineering property in the coastal saline soil in north China. In order to study the effect of the saline soil added lime (lime-soil) and saline soil added fiber and lime (fiber-lime-soil) on compressive capability, anti- freezing-thawing capability and microstructure, the freezing-thawing tests, unconfined compressive test, scanning electronic microscopy (SEM) test, nuclear magnetic resonance (NMR) test and mercury intrusion porosimetry (MIP) test are carried out, and the correlation between the compressive strength and microstructure characteristics, anti-freezing-thawing capability and its variation rules are systematically analyzed. The test results show that the compressive strength, pore volume and porosity of lime-soil and fiber-lime-soil under the freezing-thawing cycles are varied by four stages, that is, stage one (1−3 freezing-thawing cycles), stage two (4−7 freezing-thawing cycles), stage three (8−10 freezing-thawing cycles), stage four (11−15 freezing-thawing cycles). At the same freezing-thawing cycles, the failure strains of lime-soil and fiber-lime-soil increase with the increasing compactness, and the compressive strength and failure strain of fiber-lime-soil are greater than those of lime-soil, but the porosity is lower than that of lime-soil. The more the compactness is, the stronger the friction between fibers and particles, and the better the compressive properties. The interleaved fibers and randomly distributed fibers jointly limit the deformation of the soil and enhance the anti-freezing-thawing properties of the fiber-lime-soil. The results may provide the guidance in theory and technology for engineering utilization in saline soil areas in northern China.