Abstract: Taking two-way Jiangshuiquan tunnel with eight-lane of Jinan connecting line on Beijing-Shanghai expressway as the study background, the distribution law of the secondary stress σθ of the surrounding rock around the flat elliptical tunnel was analyzed, and the relationship between the tunnel rise-span ratio m and the σθ was simulated under six conditions GK1~GK6, among them: the section of GK1 was the design section; GK2~GK3 were formed by the combination of two ellipses, and the intersection of ellipses was located at the common tangent point of three center circles at the foot of the wall; GK4 ~ GK6 were ellipses with different m. Taking σθ of the surrounding rock of the tunnel vault that was the most disadvantageous part of the tunnel changed from compressive stress to tensile stress as the control standard of the surrounding rock stability, the arch wall rise-span ratio m1 of the single-span four-lane highway tunnel was analyzed. The results show that the value of σθ of the flat elliptical tunnel decreases gradually from the maximum span to the middle of the span, and the flatter the tunnel is, the larger the σθ is at the maximum span and the smaller the σθ is at the middle of the span; and whether there is tensile stress or compressive stress in the middle of the span depends on the value range of the tunnel rise-span ratio m; the main factor affecting the σθ of the surrounding rock of the flat tunnel is the arch wall rise-span ratio m1; the reasonable arch wall rise-span ratio m1R of single-span four-lane highway tunnel is put forward, that is the m1R of the surrounding Ⅲ-, Ⅳ-&Ⅴ-grade rock should be less than 0.420 ~ 0.490, 0.365~0.420 and 0.280~0.365 respectively on the premise of meeting the requirements of tunnel clearance.

Key words: tunnel engineering, single-span four-lane highway tunnel, arch wall rise-span ratio m1, secondary stress σθ

摘要： 以京沪高速公路济南连接线浆水泉双向八车道隧道为工程背景，分析了扁平隧道洞周围岩二次应力σθ的分布规律；数值模拟了6种断面GK1~GK6的隧道高跨比m与σθ的关系，其中：GK1为设计断面，GK2~GK3由2个椭圆组合形成，椭圆交接处位于三心圆在墙脚处的公切点，GK4~GK6为不同高跨比的椭圆；以隧道最不利部位拱顶σθ由压应力转为拉应力作为围岩稳定性控制基准，对单跨四车道高速公路隧道的拱墙高跨比m1进行了分析。研究表明：从最大跨度处直到跨中处，σθ在数值上逐渐减小，且洞室越扁，最大跨度处的σθ越大，跨中处的σθ越小；跨中处出现受拉应力还是受压应力取决于m的取值范围；影响扁平隧道洞周围岩二次应力σθ的主要因素是拱墙高跨比m1；提出了单跨四车道高速公路隧道的合理拱墙高跨比m1R值，即在满足隧道净空要求的前提下，Ⅲ、Ⅳ、Ⅴ级围岩m1R应分别小于0.420~0.490、0.365~0.420和0.280~0.365。

关键词: 隧道工程, 单跨四车道高速公路隧道, 拱墙高跨比, 解析计算, 围岩二次应力