曲线平行双隧道施工引起的地表沉降规律分析

曲线双隧道开挖不同于直线型隧道,近年来曲线线型多应用于地铁隧道。为研究地铁常见的曲线平行双隧道施工引起的地表沉降规律,基于吉隆坡MRT一期北段工程的施工实测数据,对4个位于不同曲线半径处的观测面沉降数据进行了分析。分析结果表明:单线曲线隧道引起的地表沉降槽有不对称现象,最大沉降值位置在隧道轴线下方;当覆土厚度等于隧道轴线距离时,曲线平行双隧道引起的地表沉降槽为对称的高斯分布,最大沉降位置在双线隧道中线位置处;随着曲线半径减小,地表沉降量将增大,当半径减小到300 m时沉降显著增加,减小千斤顶速度对减小沉降量影响不明显,应保持合理的土仓压力并适度提高注浆量。

Case Study on the Surface Settlement Induced by Shielding Curved Twin Tunnels

The surface settlement induced by curved twin tunnels is different from that induced by straight twin tunnels. In recent years, the curved alignment has usually been applied to metro tunnels. Based on the in-situ data from the first phase project of MRT in Kuala Lumpur, the surface settlement induced by the excavation of curved twin tunnels was analyzed. Four observation cross sections located in the portions with different radius of curved alignment were chosen to study the surface settlement profile of curved alignment. The results show that the surface settlement profile caused by a curved single tunnel sometimes tends to be asymmetrical and the surface settlement on the internal of alignment subsides is more than that on the external, which may caused by the uneven jacking thrust. The maximum settlement occurs under the tunnel axis. When the distance between two tunnels is equal to the cover depth, the surface settlement profile caused by curved twin tunnels with different radius is always a V-shaped symmetric Gauss curve like that caused by straight twin tunnels. The maximum settlement occurs on the middle line of twin tunnels. As the radius of curved alignment decreases, the maximum surface settlement increases. Especially, when the radius decreases to be 300 m, the maximum settlement increases significantly, which could be effectively alleviated by a reasonable earth pressure and a moderate increase of grouting volume rather than by slowing down the speed of jacks.