冻融作用下含裂隙岩石力学特性及损伤演化规律试验研究

EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES AND DAMAGE EVOLUTION OF FRACTURED ROCK UNDER FREEZING-THAWING ACTION

实际工程中冻融循环作用下裂隙岩体损伤较为严重,研究其力学特性及损伤演化规律具有极大的现实意义。鉴于此,本文采用类岩石材料模拟不同长度裂隙对岩石力学性质及冻融损伤劣化的影响,通过试验结果分析冻融过程中岩石的变形破坏现象、抗压强度、弹性模量、应力-应变曲线等在冻融循环作用与不同长度垂直裂隙相耦合作用下的变化规律,研究结果表明:岩石的抗压强度、弹性模量随着裂缝长度增大而不断降低趋势;试样在单轴压缩整个变形过程可以分为4个阶段:(1)孔隙裂隙压密阶段;(2)预制裂隙张开阶段;(3)主干裂隙扩展延伸阶段;(4)断裂破坏阶段。冻融作用对(1)、(3)阶段影响最为明显,冻融后(1)阶段明显增长,而(3)阶段中岩石伴随着主干裂隙扩展的次级裂隙明显减少;冻融后试样相对于冻融前破坏后更加松散破碎,伴随着大量岩粉、矿物颗粒的产生。而对于不同长度裂隙试样,随着裂隙长度增长,试样破碎程度提高,且破坏模式更为复杂。本研究成果可为冻融循环作用下裂隙岩体劣化损伤及断裂特性研究提供参考。

Damage of the fractured rock mass tends to be more serious under the freezing-thawing action. It is of great practical significance to study the related mechanical properties and damage evolution law. In this paper,the rock-like material is used to simulate the influence of different length fissures and freezing-thawing action on the mechanical properties of rock. The compressive strength,elastic modulus and stress-strain curves of the rock after multi freeze-thaw action are obtained. The results show that the compressive strength and elastic modulus of the rock decrease with the crack length,but the peak strain increases. The whole deformation process of the specimens can be divided into four stages:(1) Prefabricated fissure closed stage,(2) Prefabricated fissure opening stage,(3)Trunk fissure extension stage and(4) Fracture failure stage. The effect of freezing and thawing on the formation of(1) and(3) is the most obvious. The stage(1) increases. For the stage(3),the secondary fissures of the rock accompanied by the expansion of the main fissures are obviously reduced. The testing samples undergoing freeze-thaw action is much looser than the reference samples after experiment is finished,accompanied by a large number of rock powder and mineral particles. For the different lengths of the fracture specimens,increase of the crack length makes the sample more fragmented,and the destruction mode is more and more complex. The results of this study can be expected to provide a reference for the study on the damage and fracture characteristics of fractured rock mass undergoing freeze-thaw action.