大断面矩形顶管隧道开挖面土体稳定性研究  

Soil Mass Stability at the Working Face of a Rectangular Pipe-Jacking Tunnel with a Large Section

作　　者：许有俊[1] 梁玮真 刘忻梅[2] 崔广琴 白雪光 

机构地区：[1]内蒙古科技大学土木工程学院,包头014010 [2]内蒙古科技大学数理与生物工程学院,包头014010 [3]包头城建集团股份有限公司,包头014010

出　　处：《现代隧道技术》2017年第5期70-77,85,共9页Modern Tunnelling Technology

基　　金：内蒙古科自然科学基金项目(2017MS(LH)0523);内蒙古自治区高等学校科学技术研究项目(NJZY14167)

摘　　要：文章以采用土压平衡矩形顶管法施工的内蒙古科技大学地下通道为背景,采用理论分析、数值模拟、现场监控量测等手段,对砂砾石地层条件下矩形顶管开挖面的主动和被动破坏规律进行了研究,主要得到了以下结论:(1)考虑顶管隧道开挖面为矩形断面的特点,建立梯形楔体计算模型,推导出开挖面主动破坏时的极限支护应力计算公式并应用于实际工程,采用该公式计算得到的极限支护压力与数值模拟计算结果相差较小,两种研究方法得到了相互验证;(2)采用FLAC3D数值模拟得到的地表沉降槽与实测地表沉降槽形态基本相似,近似服从正态分布,且地表沉降值基本接近;(3)随着支护应力比的减小,开挖面塑性区逐渐由开挖面前方向斜上方发展,当支护应力比为0.165时,开挖面前方土体水平位移骤然增加,开挖面塑性区延伸至地表,土体丧失整体稳定性,发生主动破坏,且从开挖面失稳后地表塑性区扩展形态来看,基本接近梯形楔形体形状,从而验证了解析公式计算模型的合理性;(4)随着支护应力比的增大,开挖面前方土体塑性区自开挖面顶部向地表斜上方延伸,当支护应力比为3.0时,塑性区发展至地面,此时土体失稳,发生被动破坏,其塑性区范围远小于主动破坏时的塑性区。Based on an underpass project at the Inner Mongolia University of Science and Technology, which was constructed with an earth pressure balance rectangular pipe-jacking machine, the active and passive failure laws of the excavation face of the rectangular jacking pipe in sand and gravel are studied using theoretical analysis, numeri- cal simulations, and site monitoring. The following conclusions are determined： 1） in light of the characteristics of rectangular sections, a trapezoidal wedge calculation model is set up, a calculation formula for extreme support stress during active failure of the tunnel face is derived and applied in a practical project, and the limited support pressure calculated by the above formula is determined to be very close to that of the numerical simulation, so the two methods are verified; 2） the form of the ground surface settlement trough simulated by FLAC3D is similar to the measured ground settlement trough, which approximately complies with a normal distribution and is very close to the ground settlement value; 3） with a decrease of the support stress ratio, the plastic zone of the excavation face de- velops from the front of the face to the inclined top. When support stress ratio is 0.165, the soil horizontal displace- ment in front of the excavation face suddenly increases, the plastic zone extends to the ground surface and active fail- ure occurs with a loss of overall stability. The development pattern of the plastic zone at the surface after excavation face failure resembles a trapezoidal wedge shape, so the rationality of the calculation model is verified; and 4） with an increase of the support stress ratio, the plastic zone in front of the excavation face develops from the face top to the inclined top and reaches the ground surface, resulting in instability of the soil mass with passive failure occur- ring when the support stress ratio is 3.0, and the plastic zone is much smaller than that of active failure.

关 键 词：矩形顶管 砂砾石地层 开挖面稳定性 数值模拟 支护力 

分 类 号：TU43[建筑科学—岩土工程] U455.47[建筑科学—土工工程]