【作者】 段献良；

【导师】 陈建勋；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2010， 硕士

【摘要】 喷射混凝土在各种土建工程领域有着广泛的应用,隧道工程中喷射混凝土是隧道结构体系的主要承载单元。目前,在混凝土抗冻性方面,国内外已经做了大量的研究工作,取得了丰硕的成果,但喷射混凝土抗冻性的研究却极为鲜见。为此,本文采用理论分析和室内试验的方法,对C20和C25喷射混凝土的抗冻性进行了研究,主要取得以下成果：1、C20喷射混凝土在60个冻融循环以后,试件表面的剥落急剧增多,动弹性模量的下降较为明显,大部分试件已经接近损毁,C25喷射混凝土在100个冻融循环以后,试件表面的剥落才开始急剧增多,动弹性模量的下降也是较为明显,大部分试件接近损毁。由此可见,C25喷射混凝土比C20喷射混凝土能承受更多的冻融次数,但是二者的抗冻性都较差。2、C20喷射混凝土试件的初始动弹性模量平均值为34.52GPa,动弹性模量与冻融次数的线性回归关系为E=-0.215N+34.94(E为动弹性模量,N为冻融次数),而C25喷射混凝土分别为39.69GPa和E=-0.135N+39.55,由此可知,随冻融次数的增加,C25喷射混凝土动弹性模量的下降速度比C20喷射混凝土小,初始动弹性模量大,足见C25喷射混凝土的抗冻性能优于C20喷射混凝土。3、C20喷射混凝土试件质量损失率与冻融次数的线性回归关系为ω=0.1975N-0.346(ω为质量损失率,N为冻融次数),而C25喷射混凝土为ω=0.1925N-0.523,由此可知,随冻融次数的增加,C20喷射混凝土质量损失率的增加速度同C25喷射混凝土相差无几,而且在冻融试验初期,大部分试件都存在随着冻融循环的进行其质量反而增大的现象,从而说明质量这个指标不能较精确的反映C20和C25喷射混凝土抗冻性的差异。研究成果表明：寒冷地区隧道工程中,C20喷射混凝土抗冻性较差,对隧道结构耐久性以及安全性有较大影响,而C25喷射混凝土抗冻性能相对较好,这对隧道设计有指导意义和实用价值。更多还原

【Abstract】 Shotcrete has a wide range of applications in a variety of civil engineering field,and it is main bearing units of tunnel structure in tunnel project.Currently, frost resistance in concrete terms, has done a lot of research and has achieved fruitful results at home and abroad, but frost resistance of sprayed concrete are relatively few. Therefore, this article uses the theoretical analysis and laboratory test methods, conducted a study on frost resistance of C20 and C25 shotcrete, mainly the following results:1. After 60 freeze-thaw cycles, the specimen surface of C20 sprayed concrete flaks proliferately, dynamic elastic modulus decreases more obvious, most of the specimen is close to the damage. After 100 freeze-thaw cycles, the specimen surface flaking of C25 sprayed concrete began to proliferate, dynamic elastic modulus of decline is more obvious, most of the specimen is close to destruction. Thus, C25 sprayed concrete can withstand more freezing times than C20 sprayed concrete, but the frost resistance are more general.2. Initial dynamic elastic modulus of C20 sprayed concrete specimen averaged 34.52GPa, dynamic elastic modulus and freeze-thaw number of linear regression relationship as E =-0.215N+34.94 (E is dynamic elastic modulus, N is times of freeze-thaw), and C25 sprayed concrete respectively 39.69GPa and E=-0.135N+39.55. Suffice it to say, with the increasing number of freeze-thaw, dynamic elastic modulus of C25 sprayed concrete decreases more slowly than C20 sprayed concrete, and the initial dynamic elastic modulus is bigger, signifying frost resistance of C25 sprayed concrete is better than C20 sprayed concrete.3. Quality loss of C20 sprayed concrete samples and freeze-thaw number of linear regression relationship isω=0.1975N-0.346 (ωis the quality loss, N is times of freeze-thaw), and C25 sprayed concrete asω=0.1925N-0.523. Suffice it to say, with the increasing number of freeze-thaw, C20 sprayed concrete quality loss rate of increase in speed is almost the same with C25 sprayed concrete, and in most early freeze-thaw test specimen are present the phenomenon of increasing as the freeze-thaw cycle of their quality, thereby increasing the quality of this indicator cannot be precisely reflect C20 and C25 sprayed concrete frost resistance of the differences.Research findings show: cold regions tunnel project, C20 sprayed concrete frost resistance of poor durability to the tunnel structure, as well as security has stronger impact, and frost-resistance of C25 sprayed concrete is good, it has significance and utility value to the tunnel design.更多还原