煤渣改良路基填料冻融力学行为的机理分析

Mechanism Analysis of Freeze-thaw Mechanical Behavior of Cinder Improved Roadbed Filler

为研究冻融循环作用对煤渣改良路基填料的力学性能影响,揭示其作用机理,对红黏土试样开展了冻融循环试验和固结不排水三轴压缩试验,并对试验后的试样进行电子显微镜扫描以及微观结构定量分析。研究表明:掺入煤渣能够有效改良路基填料力学性能,改良效果与煤渣掺量呈正相关,应力应变曲线表现出硬化性;随着冻融次数的增加,改良路基填料应力-应变曲线仍为应变硬化型,但其破坏应力显著地衰减,土体颗粒间的黏结作用减弱,成型的块体减少,裂隙发育快,孔隙增大增多,接触形式由面-面接触逐渐过渡为边-面接触,最后发展为边-边或点-面接触,此外不论是总的孔隙面积、周长,还是最大的孔隙面积、周长、平面孔隙度都增大。

In order to study the effect of freeze-thaw cycle on the mechanical properties of cinder-improved subgrade filler and uncover its mechanism, the consolidation undrained triaxial test(CU) was carried out on red clay samples. Scanning electron microscopy(SEM) and microstructure quantitative analysis were performed on the tested samples. The results showed that the incorporation of cinder effectively improved the mechanical properties of the subgrade packing, the improvement was positively correlated with the dosage of cinder, and the stress-strain curves displayed hardening. With the increase of freeze-thaw times, the stress-strain curve of the improved subgrade packing was still strain-hardened. However, its failure stress was significantly attenuated, the bonding effect between soil particles was weakened, and the formed block was reduced. Additionally, the improved subgrade packing’s fracture development was speedy, the pore size and its number increased, and the contact form gradually transitioned from surface-surface contact to edge-surface contact. Finally, it developed into edge-edge or point-surface contact. Whether it was the total pore area, perimeter, or the maximum pore area, the perimeter and plane porosity both increased.