不同围岩条件玻璃纤维增强塑料锚杆结构破坏机制现场试验研究

FIELD TEST ON PULLOUT BEHAVIORS OF ANCHORAGE STRUCTURES WITH GLASS FIBER REINFORCED PLASTIC RODS FOR DIFFERENT SURROUNDING ROCK MASSES

锚杆支护方法在岩体加固工程中应用较为广泛,锚杆作为支护结构的核心应具有足够的安全度和耐久性。由于钢材易腐蚀,钢锚杆的耐久性受到极大的关注。玻璃纤维增强塑料(GFRP)锚杆是一种由树脂和玻璃纤维复合而成的新型加固材料,与钢筋锚杆相比,它具有较好的力学性能和耐腐蚀性能。通过现场原型试验,系统分析了不同围岩环境和受力条件下GFRP锚杆的抗拉特性,论证GFRP锚杆使用的适宜性,为GFRP锚杆的推广应用提供了较充分的基础数据。根据现场锚杆结构拉拔破坏性试验,研究了GFRP螺纹锚杆破坏机制和应力应变规律,为GFRP锚杆的工程应用提供了理论依据。试验结果表明,GFRP锚杆结构破坏形式有3种:杆体自由段脆性劈裂破坏、锚杆和砂浆界面剪切破坏及砂浆和围岩界面剪切破坏;GFRP锚杆的锚固机制因围岩风化程度不同而异;锚杆应力应变在锚固体内的传递深度随围岩风化程度的增加而增加;围岩风化程度越高,围岩和砂浆接触面强度较低,随着荷载的增加,围岩和砂浆界面出现剪切滑移破坏。

Steel anchor rod is one of the widely used reinforcement materials in slope engineering, tunnel engineering or large caves; but it may be eroded by groundwater or chemical solutions, which will cause the reductions of mechanical strength and service life. Compared with steel, the glass fiber reinforced plastic（GFRP） rod has higher strength and corrosion-resistance behavior. The GFRP rods are then adopted in reinforcement of various cases; and therefore a series of field tests with different surrounding rock masses are performed. The field tests show the feasibility of GFRP rods. According to the test results, the GFRP rod failure mechanism, its stress-strain behaviors, and the theory under cyclic loading are considered. In the tests, cyclic loading is applied by jacking apparatus; and the strain is measured by strain gauge. The tests show that there are three failure modes of GFRP rods as follows： brittle fracture of unbonded section; shear failure between the anchorage rod and grout; and shear failure between the grout and surrounding rock mass. The tests also show that the reinforcement mechanism is different for surrounding rock masses with different weathered grades; and the influential depth of pullout force increases with the increase of weathered grades of surrounding rock masses. For the strong weathered rock mass, a relative shear displacement appears between the anchorage grout and rock mass with the increase of pullout force. The reason is that for surrounding rock, the cohesive strength of interface between anchorage grout and surrounding rock mass is relative low.