砂土岩溶复合地层中盾构施工塌陷灾害的突发机制研究

When shield tunneling is conducted near the interface between the buried karst caverns and covering sand strata, geohazards such as sink hole may occur. This research investigates the triggering mechanisms of sudden sink hole caused by shield tunneling and establishes a safety construction theory of shield tunneling via consideration of sand covered karst strata. Research will be conducted through laboratory test using in-situ sandy soil and artificially manufactured transparent soil, field monitoring, theoretical analysis, and numerical simulation. The following key scientific problems will be investigated: i) to analyze the distribution and transferring pattern of stress during shield tunneling in sand layer and karst strata, to reveal stability loss of karst cavern induced by slurry grouting and mechanism of subsequent soil collapse and to establish the relationship between stability of sand with slurry and the size of karst cavern opening; ii) to reveal the mechanism of interior erosion of fine particle and evolvement of fracture induced by grouting injection into sand; iii) to investigate the relationship between deformation behavior of sand and particle erosion, and to reveal effect of grouting material on the stability of sand. The results of this study can propose a prediction method of sink-hole hazards scientifically during shield tunneling near the interface of buried karst caverns covered by sand strata. This study also provides a scientific base to establish a safety construction theory for shield tunneling in karst strata with caverns covered by sandy deposit.

砂土覆盖型岩溶地层交界面附近盾构施工时，极易产生岩溶塌陷等工程地质灾害。本项目以华南地区砂土覆盖型岩溶地层为研究对象，以现场砂性土以及透明模拟土为试验材料，采用室内试验、现场测试、理论分析、数值模拟相结合的方法；探明砂土与岩溶界面附近盾构施工时诱发地质灾害的机理与演化规律。拟解决如下关键科学问题：①分析确定盾构施工中砂土与岩溶复合地层中的应力分布与传递规律，探讨盾构施工诱发岩溶洞口的失稳模式与坍塌灾害的演变机理，建立岩溶孔洞尺寸与砂土层稳定性的相互关系；②揭示泥浆注入砂土层引起水土颗粒的潜蚀与劈裂裂缝的产生与演化的规律；③探讨在浆液作用下，砂土的变形与颗粒迁移的关系，揭示注浆材料性状对砂土稳定性的影响。研究成果预期可以提出盾构在砂土覆盖型岩溶地层界面施工时，诱发地质灾害的科学预测方法，进而为砂土覆盖型岩溶复合地层中盾构施工的安全控制提供重要的科学依据与理论支撑。

砂土覆盖型岩溶地层交界面附近盾构施工时，极易产生岩溶塌陷等工程地质灾害。针对这一问题，本项目以华南地区砂土覆盖型岩溶地层为研究对象，以现场砂性土以及透明模拟土为试验材料，采用室内试验、现场测试、理论分析、数值模拟相结合的方法展开研究。具体成果如下：.（1）本研究围绕盾构施工中注浆等外力引起砂土层中水土细颗粒迁移，形成砂土层管涌通道，造成的地面冒浆与诱发岩溶塌陷这个主题，建立砂土层内水与细颗粒在盾构注浆压力的驱动下形成贯通地面的通道以及诱发岩溶坍塌的颗粒级配、水力梯度、注浆压力、流量、砂土的密实度之间的定量关系。.（2）阐明产生冒浆事故与塌陷灾害的施工条件(开挖面泥水压力、注浆量、注浆压力)与细颗粒级配、溶洞距离、溶洞口大小的相互关系。应用物理模型试验、现场试验、渗流潜蚀耦合理论，以及数值模拟等技术与理论手段，阐明砂土薄覆盖型岩溶地层中盾构界面施工条件发生冒浆与塌陷灾害的发生机理。.（3）建立可综合考虑岩溶上覆砂土层中浆液和细颗粒迁移作用过程、防止岩溶地面塌陷灾害的盾构施工控制理论模型。.成果可为我国砂土覆盖型岩溶地区地下工程施工引起地质灾害的防治对策的确立，提供重要的科学依据，具有广阔的应用前景。