玄武岩纤维水泥改良风积沙强度及孔隙结构研究

Experimental study on unconfined compressive strength and microstructure of cemented aeolian sand reinforced with basalt fiber

为了研究纤维掺量对玄武岩纤维水泥改良风积沙的孔隙结构和无侧限抗压强度的影响,开展核磁共振试验和无侧限抗压强度试验。试验选用玄武岩纤维,纤维掺量分别为0%,0.2%,0.5%,0.8%,1.1%,1.4%,1.7%,水泥掺量为5%,风积沙来自新疆和若铁路工地现场。核磁共振试验结果表明,水泥改良风积沙的T2弛豫时间为0.37μs~1.98 s,对应的孔隙半径为0.74 nm~0.39 mm;而玄武岩纤维水泥改良风积沙的T2弛豫时间为0.31μs~1.07 s,对应的孔隙半径为0.61 nm~0.21 mm。与未掺纤维的水泥改良风积沙试样相比,纤维掺量为0.8%的玄武岩纤维水泥改良风积沙试样中的大孔占比减少了25.7%,中孔占比增加了12.7%,而微孔和小孔占比变化较小。无侧限抗压强度试验研究结果表明,水泥改良风积沙试样的无侧限抗压强度和峰值应变分别为0.80 MPa,1.29%,与水泥改良风积沙相比,玄武岩纤维水泥改良风积沙试样无侧限抗压强度的强度增强比为1.14~1.54,最优纤维掺量为0.8%;而玄武岩纤维水泥改良风积沙的峰值应变与纤维掺量正相关,延性增强比为1.43~2.67。掺入纤维提高了水泥改良风积沙的能量吸收能力,与水泥改良风积沙相比,最优纤维掺量的水泥改良风积沙的能量吸收能力提高了2.73倍。掺入玄武岩纤维提高了水泥改良风积沙的无侧限抗压强度,增强其延性。研究成果可为风积沙铁路路基基床表面层填料的设计和施工提供参考。

The main objective of this work is to study the unconfined compressive strength(UCS)and pore size of cemented aeolian sand reinforced with basalt fiber.In this context,a series of experiments are conducted.The cemented aeolian sand reinforced with basalt fiber samples which basalt fiber contents are 0%,0.2%,0.5%,0.8%,1.1%,1.4%,1.7%respectively.The cement content is 5%.Nuclear magnetic resonance(NMR)tests result show that the T2 relaxation time of cemented aeolian sand and cemented aeolian sand reinforced with basalt fiber are 0.37 ms~1.98 s and 0.31 ms~1.07 s respectively,and the corresponding pore radius is 0.74 nm~0.39 mm and 0.61 nm~0.21 mm.Compared with cemented aeolian sand without fiber,the volume proportion of macropores of cemented aeolian sand reinforced with 0.8%basalt fiber decreases by 25.7%,while the volume proportion of mesopores increases by 12.7%,while the volume proportion of micropores and pores changes little.The UCS and peak strain of cemented aeolian sand are 0.80 MPa and 1.29%respectively.Compared with cemented aeolian sand,the strength increase ratio of UCS of cemented aeolian sand reinforced with basalt fiber is 1.1~1.54.The maximum UCS is attained at a basalt fiber content of 0.8%,while the peak strain of cemented aeolian sand reinforced with fiber is positively correlated with the fiber content.The ductility index is 1.43~2.67.The energy absorption capacity of cemented aeolian sand is improved by the addition of fiber,and the energy absorption capacity of cemented aeolian sand reinforced with the optimal fiber content is increased by 2.73 times.The obtained results allowed highlighting the beneficial effect of the fiber,the cemented aeolian sand reinforced with fiber specimens were found to be much more ductile and higher UCS than the specimens without fiber,which is highly desirable in many backfill surface layer of the aeolian sand railway subgrade bed.