循环荷载下裂隙对加固体强度及破坏模式影响

盾构端部加固体中的裂隙对加固体的强度及破坏模式具有不同的影响。基于沈阳市地下综合管廊实际工程,用三组不同配比的水泥砂浆模拟端部加固体,用预制PVC片模拟试件中0°、30°、60°、90°的单裂隙和30°、60°的平行双裂隙。对预制裂隙试件进行循环加载试验,研究存在裂隙的端部加固体力学特性和破坏模式。研究结果表明:胶结能力较好的1∶1配比的端部加固体预制裂隙试件具有最大的疲劳峰值强度和疲劳寿命,其疲劳峰值强度和疲劳寿命均会随着胶结能力的减弱而减小;裂隙的存在会使试件的疲劳峰值强度和疲劳寿命降低,尤其当试件出现竖向劈裂破坏时,竖向裂隙对其疲劳强度和疲劳寿命的影响尤为明显;单裂隙试件多为拉―压破坏和剪切破坏,双裂隙试件多为共轭剪切破坏,并伴随有明显的共轭剪节理出现。

Effect of Cracks on the Strength and Failure Mode of Reinforced Solids Under Cyclic Loading

The cracks in the solids at the end of the shield have different effects on the strength and failure mode of the solids. Based on the actual project of the underground comprehensive pipe gallery in Shenyang City, three sets of cement mortars with different proportions were used to simulate the end solidification, and the pre-made PVC sheets were used to simulate single cracks of 0°, 30°, 60°, and 90° and parallel double cracks of 30° and 60° in the test pieces. The cyclic loading test was carried out on the pre-formed fracture specimens to study the mechanical properties and failure modes of the ends with cracks. The results show that the 1:1 ratio of the end-filled solid pre-formed fracture specimens with good cementation ability has the maximum fatigue peak strength and fatigue life, and the fatigue peak strength and fatigue life are reduced with the decrease of cementation ability; the existence of cracks will reduce the fatigue peak strength and fatigue life of the test piece, especially when the test piece has vertical splitting damage, and the effect of vertical crack on its fatigue strength and fatigue life is particularly obvious; most of the specimens with single crack are tensile compression failure and shear failure, and the double-fracture specimens are mostly conjugate shear failures, acco mpanied by obvious conjugate shear joints.