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针对西江特大桥广州岸岩锚锚碇系统的承载稳定性问题,采用工程地质勘察、室内及现场原位岩石力学特性试验、钻孔摄像及声波测试等手段,获取承载边坡的岩体地质力学特性,并建立边坡地质力学模型,同时进行现场拉锚试验验证预应力锚索设计的可靠性。采用三维数值模拟方法研究锚碇系统在施加预应力和承担外荷载两种情况下,边坡岩体的稳定性和锚碇群锚中不同位置的预应力锚索锚固力的分布特征。研究表明,在桥梁施工荷载的拉拔作用下,广州岸锚碇边坡整体稳定,坡表变形为毫米级;锚索锚固力呈不均匀分布形态,主要集中在锚固段前2 m范围内,最大值出现在锚固段端头;锚碇群锚的锚固力应力集中程度由大到小依次是角锚、边锚、中间锚。超载试验表明,整个锚碇系统的极限抗拔力不小于8倍设计荷载。锚索现场监测数值显示,锚碇承载期间锚索索力基本稳定,中间锚的索力小于角锚。研究方法及成果可供类似的桥梁及抗倾拔工程中的岩锚锚碇设计及安全评价借鉴。
Aiming at the bearing stability of the rock anchorage system in Guangzhou coast of the Xijiang River Bridge, the geomechanics of rock mass bearing the slope is obtained by means of engineering geology investigation, in-situ and in-situ rock mechanics characteristics test, borehole imaging and acoustic testing Characteristics, and establish slope geomechanical model, at the same time on-site pull anchor test to verify the reliability of prestressed anchor cable design. The three-dimensional numerical simulation method is used to study the stability of slope rock mass and the distribution of prestressed anchor cable anchorage force at different positions in the anchorage group anchorage system under both prestressed and unloaded external loads. The results show that under the action of bridge construction load, the slope of Guangzhou coast anchorage is stable and the slope table is deformed to millimeter. The anchoring force of anchorage cable is inhomogeneous distribution, mainly concentrated within 2 m of the anchorage section, The maximum appears in the end of the anchorage segment; Anchorage anchorage group anchorage stress concentration in descending order of angle anchor, edge anchor, intermediate anchor. Overload test shows that the ultimate anchorage system ultimate pull-out force of not less than 8 times the design load. The on-site monitoring data of anchor cable show that the anchor cable force is basically stable during anchor load, and the cable force of the middle anchor is smaller than that of the anchor. The research methods and results can be used for the design and safety evaluation of rock anchorage in similar bridges and anti-dumping projects.