劈裂损伤岩石胶结强化的蠕变特性与失稳模式

Instability mode and creep characteristics of cementation of rock with splitting damage

通过RLW-2000型三轴流变仪,对2组13个损伤试样进行胶结重增量加载蠕变试验,研究了损伤岩石胶结试样在不同蠕变应力水平下瞬时应变与蠕变应变特性,分析了不同胶结状态及胶结厚度对试样蠕变破坏强度影响,确定了胶结厚度与试样瞬时应变、蠕变应变关系,探讨了胶结试样蠕变破坏形态,确定了胶结试样蠕变破坏基本模式。结果表明:随着蠕变应力水平提高,2组试样瞬时应变均表现为减小趋势,大理岩和粗砂岩试样蠕变应变分别表现增加与减小趋势;紧缝胶结试样蠕变破坏强度大于无胶结试样,但随着胶结厚度增加,胶结试样蠕变破坏强度呈现减小趋势;在相同蠕变应力水平下,随着胶结厚度增加,胶结试样蠕变应变呈缓慢增加趋势,但蠕变应变增加幅度小于瞬时应变;紧缝胶结试样破坏主控面单一,主控面角度近似垂直,且破裂块体较大,而厚度胶结试样破坏主控面复杂,且试样上下部滑移错动失稳明显;胶结试样蠕变破坏模式分为分离破坏模式、贯穿劈裂模式与贯穿滑移模式。

The creep test of incremental loading is carried out on thirteen damaged rock samples in two groups through RLW-2000 triaxial rheology test system. Instantaneous strain properties and creep ones of cement samples of damaged rock are studied in different creep stress. The effects of different cement state and thickness on the breaking strength of creep are analyzed. The relationships between cement thickness and instantaneous strain and creep one are determined. The creep failure modes of cemented sample are discussed and its basic mode is determined. The results have shown that, with creep stress increasing, instantaneous strain of all the samples in two groups decreases. Creep strain of the marble samples increases and that of coarse sandstone decreases. Creep failure strength of narrow-slit cement samples are more than that of no-cement samples, but creep failure strength decreases with cement thickness increasing. Creep strain of cement samples increases slowly with cement thickness increasing in same creep stress, while the increasing range of creep strain is less than that of instantaneous one. Main failure surface of narrow-slit cement samples is simple and approximately right angle, with larger broken block. In contrast, main failure surface of thickness cement sample is complicated, and slip and dislocation is obvious between the upper and the lower of the sample. Creep failure of cementation samples includes three modes: split failure, fracture splitting, fracture slipping.