丹江口水库特大桥地锚式桥台CFRP预应力岩锚施工技术

Construction Techniques of Anchorage-Type Abutments with CFRP Anchor Rods in Rock Anchorages of Danjiangkou Reservoir Bridge

丹江口水库特大桥为主跨760 m双塔双索面部分地锚式混合梁斜拉桥,边中跨比为0.2,边跨端部设置空腔式箱形台身+岩锚的组合式地锚式桥台。为提高地锚式桥台在横桥向不平衡土压力作用下的抗滑稳定性,在1号地锚式桥台台身外侧墙中心线位置布置14组(每组2束)高性能竖向CFRP预应力岩锚结构,该岩锚结构由CFRP预应力锚杆和RPC粘结介质构成,分为地上锚固段、自由段和地下锚固段3段。该岩锚结构采用后安装工艺施工,即CFRP预应力锚杆先在工厂加工制作,整体运输至现场后单根整体安装下放。为验证CFRP预应力岩锚结构的可靠性、注浆工艺的可行性,在CFRP预应力岩锚主体结构施工前进行足尺模型工艺试验。工艺试验结果表明:CFRP预应力岩锚结构具有良好的锚固性能及足够的安全储备,注浆工艺可行。地锚式桥台施工时在墙身位置预埋管道,桥台及上部主梁施工后从梁面顶部通过预埋管道进行地下锚固段孔道钻孔施工,清孔后进行CFRP预应力锚杆整体下放安装,之后进行孔道注浆,最后进行CFRP预应力锚杆张拉、封锚,完成岩锚施工。该桥28束CFRP预应力岩锚已施工完成,且岩锚注浆密实,注浆强度满足设计要求。

The Danjiangkou Reservoir Bridge is a two-pylon hybrid girder cable-stayed bridge with a main span of 760 m.The stay cables are arranged in double cable planes and the longer stay cables(14 pairs in each side span)are anchored to the ground.The ratio of side span length to main span length reaches 0.2.The anchorage-type abutment consists of a void box body and rock anchorages.To ensure the anti-slip stability of the anchorage-type abutment under the unbalanced soil pressure along the bridge width,14 groups(each group contains two CFRP tendons)of vertical high-performance CFRP prestressed rock anchorages were placed along the central line of the sidewalls of the abutment No.1.Consisting of a CFRP anchor rod and RPC bonding agent,each rock anchorage is formed of a ground anchor section,a free section and an underground anchor section.The CFRP anchor rods were manufactured in the factory,integrally transported to the bridge site and installed into place one by one.Full-scale model tests were performed ahead of the construction of the main body of the CFRP prestressed rock anchorage to verify the reliability of the rock anchorage structure and the feasibility of the grouting techniques.The results of the test indicate that the CFRP prestressed rock anchorage has a better anchor performance and sufficient safety margin and the grouting techniques are feasible.During the construction of the anchorage-type abutment,ducts were pre-buried in the abutment walls.Once the construction of abutments and superstructure was completed,the duct hole drilling in the underground anchor section was carried out from the deck top through the pre-buried ducts.When the holes were cleared up,the CFRP prestressed anchor rod was integrally lowered and installed,and then the ducts were grouted.At last,the CFRP prestressed anchor rods were tensioned,and seams in the anchorage were sealed.All the 28 CFRP prestressed anchor rods had been installed,the grouping quality was good and the grouting strength met the design requirements.