裂隙与持续荷载影响下砂浆锚杆腐蚀退化的试验研究

Experimental investigation of corrosion-induced degradation of rockbolt considering natural fracture and continuous load

锚杆是岩土工程中应用最广泛的锚固结构之一。锚杆腐蚀严重影响锚固结构的长期使用性能,导致锚固工程过早失效破坏。砂浆锚杆的腐蚀退化机理尚不完全清楚,特别是考虑到岩体的天然裂隙和锚杆所受到的持续荷载作用。本文考虑天然裂隙和持续荷载,开展了锚杆腐蚀退化综合试验研究。对不同位置裂隙的混凝土-砂浆-锚杆试件进行了腐蚀试验。采用可施加持续应力装置对锚杆施加连续的轴向载荷,并采用电化学方法加速锚杆腐蚀。通过对不同腐蚀时间的锚杆进行拔出试验,得到了腐蚀试件的黏结滑移关系。进一步讨论了天然裂隙和连续荷载对锚杆腐蚀特性、腐蚀机理和黏结性能退化的影响。结果表明,锚杆腐蚀显著降低了砂浆锚杆的黏结强度和临界滑移长度。腐蚀程度为3.45%~4.98%的锚杆黏结强度较腐蚀前下降39.5%~65.8%。锚杆在天然裂隙附近更容易发生局部腐蚀。天然断裂越靠近加载端,腐蚀引起的黏结强度退化越严重。轴向载荷越大,腐蚀退化越明显。本研究解释了砂浆锚杆在裂隙岩体中的腐蚀退化机制,为锚杆支护耐久性设计提供了参考。

Corrosion of rockbolt significantly affects the long-term serviceability of anchorage structures,resulting in premature failure of rock engineering.The corrosion and degradation mechanism for mortar grouted rockbolt is far from clear.In this paper,comprehensive experiments were carried out to investigate corrosion-induced degradation of rockbolt considering natural fracture and continuous load.Concrete-mortar-rockbolt specimens with an initial crack at different locations were made.Continuous axial loads were applied to the rockbolt by a puller system.The electrochemical method was employed to accelerate rockbolt corrosion.The bond−slip relationships for corroded specimens were obtained by the direct pull-out test of rockbolt.Further,the effects of natural fracture and continuous load on the corrosion characteristics,corrosion mechanism and bond performance degradation of rockbolt were discussed.Results show that corrosion of rockbolt significantly reduces the bond strength and critical slip displacement of rockbolt.The bond strength for the rockbolt with a corrosion degree of 3.45%−4.98%reduces by 39.5%−65.8%compared with that before corrosion.Corrosion of rockbolt is more prone to occur near the natural fracture.The closer the natural fracture to the loading end,the more severe the corrosion-induced bond degradation.The larger the axial load,the more significant the corrosion degradation.