In this paper,a single tunnel four lane highway tunnel as the background,the large cross section of the tunnel excavation and support of the mechanical properties of the mechanical proper-ties were studied.The results show that:in the early stage of excavation,the surrounding rock has a large settlement rate and the amount of value,the impact of the roof displacement of the tunnel is a large part of the excavation.In the course of construction,the upper structure support is reasonably determined, meanwhile,it can effectively control the deformation of surrounding rock.Within the range of K5 +530-K5 +660,the maximum settlement value is 34 mm,the worse the geological condition is,the larger the cross-section of the excavation,the more simple support structure,the greater the deformation of sur-rounding rock.The pressure of the measuring points of the left and the right arch of the tunnel section first increases and then tends to be stable.Buried deep under the same conditions,the left hole and a right hole rock pressure level and distribution law is consistent,adjacent to the lateral arch pressure than the other side to large dome,the maximum pressure is 0.27 MPa,side wall pressure minimum is 0.06 MPa;in the process of stress change,steel arch left arch shoulder maximum stress 45 MPa,left arch waist at the maximum stress 32 MPa,excavation in the process of formation of the pressure arch struc-ture,self bearing capacity of surrounding rock effectively play.%以某单洞四车道高速公路隧道为背景，对车道特大断面大跨度隧道的开挖与支护力学性能进行了研究。结果表明：开挖前期，围岩均有较大的沉降速率及量值，对拱顶位置位移影响较大的是隧道上部分的开挖。在施工过程中，对上部结构支护进行合理确定，同时对其进行及时封闭可有效控制围岩变形。在 K5＋530－K5＋660的里程范围内，沉降值最大为34 mm，地质条件越差，开挖的断面就越大，支护结构也就越简单，围岩变形就会越大。隧道断面左、右拱肩测点的压力均先增大最后趋于平稳。埋深条件相同，左洞和右洞围岩压力水平及分布规律是一致的，相邻侧拱部的压力比另一侧的要大，拱顶最大压力为0.27 MPa，外侧边墙的压力最小，为0.06 MPa；在应力变化过程中，钢拱架左拱肩处最大应力为45 MPa，左拱腰处最大应力为32 MPa，说明开挖过程中形成了压力拱结构，围岩自承能力得到有效地发挥。
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