不同层间倾角下砂-黏复合地层隧道开挖面稳定性离心模型试验 English Version
Centrifuge test of face stability in sand-clay layered strata with different interlayer angles
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摘要: 基于离心模型试验,系统研究了不同层间倾角及层间界面位置下砂-黏复合地层盾构隧道开挖面的稳定性。试验采用高速摄像与分析系统定量分析开挖面周围土体运动特征,采用后置应力传感器与前置土压力盒两种测量手段测定开挖面支护力,通过实时土压力监测系统获取失稳过程中土压力场的动态演化特征。通过建立三维离散元数值模型,对试验结果进行验证。研究结果表明:层间倾角显著影响开挖面失稳破坏模式。正倾角条件下,砂土与黏土呈较独立变形特征。负倾角条件下两层土体协同变形,失稳范围显著扩大,产生贯通地层界面的连续剪切区域。当层间界面位于拱顶时,正倾角工况失稳区域范围有限,而负倾角工况仍会产生明显失稳。极限支护力主要受层间界面位置影响,层间界面位于拱顶时所需极限支护力小于其位于拱轴线的情况,层间倾角对极限支护力影响相对有限。失稳区域土压力呈现先快速下降后趋于稳定的两阶段演化特征。砂土层竖向土拱率分布与失稳区域轮廓吻合,横向形成显著土拱效应,拱顶与拱腰分别位于地表附近及层间界面处。研究成果可深化对倾斜复合地层开挖面失稳机理的认识,为工程实践中施工风险控制提供一定依据。Abstract: Based on centrifuge model tests, this study systematically investigated the stability of shield tunnel face in sand-clay composite strata under different interlayer inclination angles and interface positions. The experiments employed high-speed camera and analysis systems to quantitatively analyze soil movement characteristics around the tunnel face, utilized both rear-mounted stress sensors and front-mounted earth pressure cells to measure support pressures, and captured the dynamic evolution of earth pressure fields during instability processes through real-time earth pressure monitoring systems. Three-dimensional discrete element model was established to validate the experimental results. The research findings indicate that interlayer inclination angles significantly influence the instability and failure modes of tunnel face. Under positive inclination conditions, sand and clay exhibit relatively independent deformation characteristics. Under negative inclination conditions, the two soil layers deform cooperatively, with instability ranges significantly expanding and continuous shear zones penetrating through the stratum interface. When the interlayer interface is located at the crown, positive inclination conditions result in limited instability zones, while negative inclination conditions still produce significant instability. The critical support pressure is primarily influenced by the interlayer interface position, with the required critical support pressure being smaller when the interface is at the crown compared to when it is at the tunnel axis, while the interlayer inclination angle has relatively limited impact on critical support pressure. Earth pressure in the instability zone exhibits a two-stage evolution pattern characterized by rapid initial decline followed by stabilization. The vertical soil arching ratio distribution in the sand layer aligns with the instability zone contour, forming significant lateral soil arching effects with the arch crown and arch waist located near the ground surface and at the interlayer interface. These research findings can deepen understanding of tunnel face instability mechanisms in inclined composite strata and provide guidance for construction risk control in engineering practice.
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Keywords:
- shield tunnel /
- face stability /
- sand-clay layered strata /
- interlayer angle /
- centrifuge test
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