砂岩石窟顶板微小型锚杆倒置锚固方法与性能研究

Study on inverted anchorage method and performance of microminiature bolts in sandstone grotto roof

石窟顶板浅层岩体剥落病害频繁发育,降低石窟结构稳定,影响石窟窟顶文化信息保存,采用扰动小、隐蔽性高的微小型锚杆垂直锚固技术,能够有效约束岩体变形、控制病害发育。本次试验选用直径8,10,12mm的玻璃纤维锚杆(GFRP)和玄武岩纤维锚杆(BFRP),根据前阶段的研究成果确定最优孔径比,将锚杆倒置植入砂岩顶板,在杆体–浆体界面小间距布设应变测点,采用循环加载模式开展现场拉拔试验。研究发现,小直径的GFRP和BFRP锚杆倒置锚固系统具有弹塑性阶段的界面协调缓变形能力,直径10 mm的锚固系统对最优孔径比匹配性最好,倒置多级注浆方式施工工艺简易,性能较好。对比前期试验结果可知,相同锚固参数的崖体水平锚固系统与顶板倒置锚固系统的极限荷载比值为1.90倍,相应的位移比值为3.27倍,应变值域比值为3.26倍,2种锚固系统性能差异与锚杆植入岩体方位和注浆质量差异等相关,相关研究成果可为微小型锚杆倒置锚固措施在砂岩平顶窟顶板的工程应用提供支撑。

The frequent occurrence of shallow rock mass peeling diseases in the roof of the grottoes reduces the stability of the grottoes¢structure and affects the preservation of cultural information.The vertical anchoring technology,with low disturbance and high concealment,effectively restrains rock mass deformation and controls the disease¢s development.This experiment selected 8,10 and 12 mm diameter Glass Fiber Bolt(GFRP)and Basalt Fiber Bolt(BFRP).The optimal aperture ratio was determined based on previous researches,and the bolt was inserted into the sandstone roof.Strain measuring points were placed at small intervals at the rod-slurry interface,and a cyclic loading mode was used for the field pull-out test.It was observed that the inverted anchorage system,using small diameter GFRP and BFRP,demonstrated interface coordination and deformation easing ability in the elastoplastic stage,and that the anchorage system with a 10mm diameter showed the best matching ability to the optimal aperture ratio.The inverted multi-stage grouting method exhibited a simple construction process and good performance.Compared with the previous test results,it can be seen that the ratio of ultimate load between the cliff horizontal anchoring system and roof inverted anchoring system with the same anchoring parameters is 1.90 times,the corresponding displacement ratio is 3.27 times,and the ratio of strain range is 3.26 times.The performance difference of the two anchoring systems is related to the difference of bolt insertion direction and grouting quality,etc.The relevant research results can provide support for the engineering application of micro-miniature inverted anchor bolt in sandstone flat roof.