高速公路隧道水平层状围岩锚杆支护参数优化研究

公路隧道穿越水平岩层施工过程中极易出现平拱、拱顶离层破坏、拱顶弯折内鼓等现象,而利用系统锚杆的"组合梁"作用可以极大减少水平岩层的拱部掉块,保证施工质量。以大梁峁特长公路隧道K81+300～K83+308段为工程依托,在对大梁峁隧道断面围岩的物质组成、结构特征、变形破坏机理分析的基础上,利用有限元数值模拟方法对原锚杆支护方案进行了优化,提出锚杆设置范围宜为拱部160°、锚杆长度为3.5m,边墙的系统锚杆可以根据实际施工情况不设或少设,并通过现场试验数据进行了验证,进一步证明了锚杆支护优化设计合理,效果显著。

Study of the Optimization of the Parameters for the Bolting Support in Horizontally-Bedded Surrounding Rock of Expressway Tunnels

The hazards of the flat arch, the top-layer-separating destruction, the flexed and inside-raised arch crown, etc. often emerge during the construction of highway tunnels which go through a horizontal stratum, in which case making use of the function of the ＂composite beam＂of the systematic bolts can greatly reduce the fall of arch blocks so as to ensure the quality of construction. With the section of K81 ＋ 300 K83 ＋ 308 of the extra-long Daliangmao Highway Tunnel as a practical example, and on the basis of analyzing the material composition, structural characteristics and deformation and failure mechanism of the surrounding rock of the cross-section of the tunnel, the original plan of the bolting support is optimized in the light of the finite element numerical simulation method, with the suitable laying ranges of the anchor bars put forward： the bolting support should be provided within the angle of 160~ of the arch and the length of the anchor should be 3.5 m,while the systematic anchors for the side wall might be unnecessary or fewer of them might be needed according to the practical construction conditions, which has to be checked with the site test. It is proved once again that the optimized design of the parameters of the bolting support is appropriate,and the effect of the optimized support is obvious.