气压辅助土压平衡盾构掘进地表变形规律研究

    STUDY ON THE SURFACE DEFORMATION LAW OF SHIELD TUNNELING IN AIR PRESSURE ASSISTED EARTH PRESSURE BALANCE MODE

    • 摘要: 软土地层中盾构掘进引起的地表变形易造成邻近建/构筑物变形开裂,构成安全隐患并产生不利的社会影响。广州市地铁18号线陇枕出入场线是位于软土地层的浅埋隧道,为有效控制盾构掘进引起的地表变形,先后采用全土压平衡模式和气压辅助土压平衡模式进行掘进。对比两种掘进模式下的实测地表变形数据,发现当地层气密性良好时,采用气压辅助土压平衡模式能更好地控制地表变形。分析两种掘进模式下的地表变形规律以及影响因素,结果表明:两种掘进模式下,地表变形发展均可分为5个阶段,且地表变形主要发生在第Ⅲ阶段和第Ⅳ阶段;全土压平衡模式第Ⅲ阶段地表变形以沉降为主,采取中盾注浆措施或气压辅助土压平衡模式均会导致此阶段地表隆起,第Ⅲ阶段地表变形量与气压值的线性相关性更高;气压辅助土压平衡模式第Ⅳ阶段地表变形量与盾尾注浆压力、盾尾注浆量、气压值的线性相关性依次增加,皮尔逊相关系数分别为0.53、0.62、0.84,通过调节气压值可有效控制地表变形量。研究结果可为类似条件下气压辅助土压平衡盾构工程的地表变形控制提供一定理论依据和技术支撑。

       

      Abstract: In soft ground, the surface deformation caused by shield tunneling easily results in the deformation and cracking of adjacent buildings, bringing safety hazards and adverse social effects. In order to effectively control the surface deformation during shield tunneling, the earth pressure balance(EPB)mode and the air pressure assisted earth pressure balance(APEPB)mode were successively adopted in Longzhen Exit and Entry Lines of Guangzhou Rail Transit Line 18,which were shallow-buried tunnels in soft ground. First, the measured surface deformation data were analyzed in the two tunneling modes. It indicates that the APEPB mode does better in controlling surface deformation when the stratum has good air tightness. Second, the surface deformation law in the two modes as well as the influence of construction parameters on the surface deformation were studied. It indicates that the development of the surface deformation can be divided into five stages and the deformation values in the third and fourth stages are the largest. In the third stage, the surface deformation is mainly subsidence in the EPB mode, but the surface will uplift when adopting the middle-shield grouting or the APEPB mode. Compared with the middle-shield grouting volume, the linear correlation between deformation value and air pressure value is higher. In the APEPB mode, the linear correlations between deformation value in the fourth stage and grouting pressure value, grouting volume, and air pressure value increase successively, whose Pearson correlation coefficients are 0.53, 0.62 and 0.84,respectively. It indicates that the surface deformation can be effectively controlled by adjusting the value of air pressure. The results can provide a theoretical basis and technical support for the control of surface deformation under similar conditions during shield tunneling in the APEPB mode.

       

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