According to the bending load conditions of tunnel lining concrete in service,the durabili-ties of cellulose fiber reinforced concrete(CFRC)unloaded and loaded to 40% four-point bending strength were studied:resistances of chloride ion permeability,carbonation,freezing-thawing and sulfate attack.These results were also compared with the durability of unloaded plain concrete with-out fibers.The micro-mechanisms of the effect of cellulose fiber on the durability of CFRC were in-vestigated as well.The results show that compared with the unloaded plain concrete,the durability of the unloaded CFRC is increased dramatically due to the effects of the special hollow microstructure and hydrophilicity of cellulose fiber on the optimized pore structures and homogeneous dispersion of cellulous fibers in hardened CFRC matrix,and the electric flux of CFRC only decreases by 25%;the carbonization depth of unloaded CFRC with different ages reduces by 0.9 to 2.5 mm.The external bending load slightly weakens the durability of CFRC compared to unloaded CFRC,e.g.the electric flux increases by 17%,and the carbonization depth increases by 0.2 to 1.3 mm.However,the du-rability of loaded CFRC is still better than that of the unloaded plain concrete,e.g.the electric flux only reduces by 12%,and the carbonization depth reduces by 0.4 to 1.2 mm.The relative dynamic elastic modulus increases by 3% after 200 times of sulfate dry-wet cycles.%针对隧道衬砌结构混凝土在服役过程中承受弯拉荷载的实际情况，研究了纤维素纤维混凝土分别在加载40％四点抗弯强度和不加荷载条件下的抗氯离子渗透性、抗碳化、抗冻融及抗硫酸盐侵蚀等耐久性能及其微观机理，并与未加载的普通素混凝土耐久性能进行了对比分析．结果表明：由于纤维素纤维具有独特的空腔结构和亲水性，可在硬化混凝土基体中乱向均匀分布并显著优化混凝土的孔隙结构，使得未加载的纤维素纤维混凝土与基准素混凝土相比，耐久性显著提高，电通量仅降低25％，不同龄期碳化深度减小0．9～2．5 mm．与未加载的纤维素纤维混凝土相比，加载后的纤维素纤维混凝土耐久性略有削弱，电通量增加了17％，不同龄期碳化深度加深了0．2～1．3 mm；但与未加载的基准素混凝土相比，加载后的纤维素纤维混凝土耐久性仍有所提高，电通量仅降低了12％，不同龄期碳化深度减小0．4～1．2 mm；200次硫酸盐干湿循环后，加载后的纤维素纤维混凝土相对动弹性模量仍比未加载的基准素混凝土高出3％．
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