硫酸盐腐蚀锚索结构锚固性能退化规律试验研究

EXPERIMENTAL STUDY ON DEGRADATION BEHAVIOR OF ANCHOR CABLES DUE TO SULFATE CORROSION

硫酸盐腐蚀是锚索结构长期锚固性能退化的原因之一。为模拟围岩约束条件下硫酸盐对锚索浆体的腐蚀及腐蚀后的锚固受力过程,设计外包钢管圆柱形素水泥浆中置钢绞线短黏结试件并进行长期硫酸盐干湿循环腐蚀,然后通过静力拔出试验观察黏结受力过程,获取黏结滑移曲线,定义锚固特征参数。结果表明:围岩约束作用对腐蚀过程及拔出受力过程产生显著影响,腐蚀引起的物理损伤得以阻止,化学损伤成为主要腐蚀损伤方式;拔出破坏特征为:浆体螺旋肋逐渐被磨平,索体最终被抽出;全程黏结滑移曲线由初期极速上升段、中后期锯齿形上升段及末期快速下降段组成;当围岩变形模量增大时,设计允许滑移、设计强度、极限滑移以及极限强度均随之增大;当浆体腐蚀程度增大时,设计强度、极限滑移以及极限强度随之降低,而设计允许滑移则因浆体模量的退化而随之增大。

Sulfate corrosion is one of the reasons why anchor cables undergo the degradation of long-term anchoring capacity. To simulate the sulfate corrosion to the host concrete of anchor cables and the anchoring behavior after corrosion under the restriction of rock,a kind of short-bonded specimen of cylindrical plain cement concrete wrapped by a steel pipe outside and permeated by a steel strand centrally was designed. Then a long-term sulfate corrosion to the specimens in cyclic wetting and drying conditions was conducted. When the corrosion test was completed,a static pull-out test was executed to observe the anchoring process,to obtain the bond-slip curves and to define the characteristic anchoring parameters. The results showed that the restriction of rock had a significant impact on corrosion process and anchoring behavior in pull-out process. The physical damage was prevented and the chemical damage was the main way of corrosion. In the pull-out test,the spiral ribs of concrete were planished gradually and the cable was pulled out finally. The whole bond-slip curve consisted of a sudden rising initially,then a jugged rising and a rapid falling stages finally. When the deformation modulus of rock increased,the allowable design slip,design strength,ultimate slip and ultimate strength increased accordingly. And when the corrosion of the concrete was aggravated,the design strength,ultimate slip and ultimate strength decreased accordingly,while the design slip increased due to the degradation of concrete modulus.