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目前,有些黄土公路隧道受到地形限制只能采取小净距隧道形式,为了更好地解决彼此开挖相互受影响带来的安全隐患问题,笔者开展了6组基于先加载后开洞思路的离心模型试验,研究了不同净距和间距的组合下双洞效应黄土公路隧道地表及地层的变形规律。试验结果表明:间距保持1D时,随着净距的增大,双洞间的相互影响程度明显减弱,先行洞开挖对后行洞的次生扰动逐级递减;地表沉降轮廓由单核心盆地演变为多核心盆地,地层变形曲线从V形发展为W形;压力拱效应明显且成拱高度随两隧体净距的增加而升高。间距变为2D时,无论净距如何取值,地表和地层沉降的最大值都会在右侧隧道中心线附近出现,右侧隧道上覆土体变得更为敏感。净距2D间距2D时,地表和地层沉降均在右侧先行隧道拱顶上方出现6组工况下的最大沉降值,评定为最不利工况;间距1D净距取1.5D和2D时,两隧体间均可形成自稳的宽底承载土柱体。因此,小净距黄土公路隧道合理净距取值范围为1.5D~2D,相应的掌子面间距宜控制在1D内。
At present, some loess tunnels can only take the form of small clear distance tunnel due to the terrain restriction. In order to solve the potential safety problems caused by mutual excavation, the author carried out 6 sets of centrifugation based on the idea of opening after loading first Model tests were conducted to study the deformation of the earth’s surface and formation under the double-hole effect in a tunnel with different spacing and spacing. The experimental results show that the mutual influence between the two holes is obviously weakened with the increase of the clear distance when the spacing is maintained at 1D. The secondary disturbance of the tunnel after the first hole excavation decreases progressively. The surface subsidence profile evolves from the single core basin For the multi-core basin, the stratigraphic deformation curve developed from V-shape to W-shape. The pressure arch effect was obvious and the height of the arch increased with the increase of the clear distance of the two tunnels. When the spacing is changed to 2D, the maximum value of surface and subsidence will appear near the center line of the right tunnel regardless of the clearance distance, and the soil on the right tunnel will become more sensitive. When the clear distance is 2D, the maximum settlement value of 6 groups of working conditions appears on the top of the tunnel on the right side and is evaluated as the most unfavorable condition. When the distance 1D is 1.5D and 2D, Between the tunnel body can form a self-sustained wide bottom bearing soil column. Therefore, a reasonable distance between the small clear-distance loess highway tunnel should be within the range of 1.5D ~ 2D and the corresponding distance between the two faces should be controlled within 1D.