胀缩性土质隧道围岩失稳机理与支护对策研究

It is very serious consequence for the tunnel engineering that the swell-shrink characteristics of soils are water swelling and shrinkage, which is one of the major technical problems for constructing tunnels through such soil area. Based on the deformation rules of surrounding rocks in the swell-shrink characteristics of soil tunnels and a large number of engineering practices, the instability precursor information of surrounding rocks, catastrophic mechanism and support measures are researched systematically by applying a variety of technical means. Through the engineering geological investigation about hydrologic geology and research on the rules of surrounding rocks deformation, the disaster geologic precursor information is differentiated. The generating conditions of disaster and influencing factors are also presented. Considering the different of wetting and drying cycles, swell-shrink rates, stress loading conditions, excavation process of tunnel and supporting structure types, the malignant deformation of surrounding rocks, the generating conditions and influencing factors of swell-shrink failure area, failure characteristics of supporting measures are studied according to model tests. And the supporting types, supporting parameters and time are discussed. The catastrophic model of surrounding rocks in swell-shrink characteristics of soil tunnels is established, which is used to research the non-linear catastrophic characteristics, define the catastrophic criterions and put forward stability control method. The research results have the important theoretical and practical significance for understanding the failure mechanism of swell-shrink characteristics of soil tunnels and solving the difficult about the stability control of surrounding rocks.

胀缩性土具有显著的吸水膨胀和失水收缩的变形特性，对隧道工程造成极为严重的后果，是目前隧道穿越此类地质区域施工中的重大技术难题之一。本项目以胀缩性土质隧道围岩变形规律研究为基础，以大量工程实践为依托，应用多种技术手段，系统地研究胀缩性土质隧道围岩灾变机理与支护对策。通过工程水文地质调研和现场围岩变形规律的研究，辨别其临灾地质前兆信息，提出灾害的发生条件与影响因素。通过考虑典型的干湿循环、胀缩率、应力加载条件、开挖工艺和支护结构型式等多种因素的正交组合，试验研究胀缩性围岩恶性变形规律、胀缩性破坏区特征及其产生条件与影响因素、支护结构破坏模式等，提成破裂区围岩的合理支护型式、支护参数和支护时机。建立胀缩性土质隧道围岩灾变模型，研究围岩失稳的非线性灾变特征，定义灾变判据，提出稳定控制方法。研究成果对认识胀缩性土质隧道围岩破坏机制，解决此类隧道围岩稳定性控制困难具有重要理论与实际意义。

胀缩性土具有显著的吸水膨胀和失水收缩的变形特性，对隧道工程造成极为严重的后果，是目前隧道穿越此类地质区域施工中的重大技术难题之一。本课题以揭示胀缩性土质隧道围岩失稳破坏机理，提出有效的支护措施为研究目标，综合采用室内试验、现场试验、理论分析与数值计算方法，依托典型胀缩性土质隧道建设工程，通过地质调研与现场试验，揭示了胀缩性土质隧道围岩致灾信息特征；采用室内力学试验方法，分析了线缩率与膨胀率的时程特性，研究了膨胀土浸水后吸水膨胀变形的规律；基于理论分析与数值计算方法，采用热-力耦合计算方法模拟胀缩性土膨胀变形过程，设置膨胀土地层线膨胀系数、比热容等参数，通过改变温度施加膨胀应力模拟降雨致使膨胀土隧道围岩变形过程，进而揭示了膨胀土隧道围岩在干湿循环作用下的变形和破坏过程，并与现场实验结果进行对比论证，验证力学模型的准确性，通过数值计算分析，评判隧道的稳定性；通过研发胀缩性土的相似材料，建立了能够有效模拟“日照”和“降雨”的地质力学模型试验装置，基于模型试验分析，揭示了干湿循环作用下膨胀土隧道围岩孕灾机理。综合以上研究成果，提出适用于胀缩性土、软弱土等隧道新型支护结构，为膨胀土质隧道灾害的预警与治理提理论基础。综上所述，本课题研究成果对认识胀缩性土质隧道围岩破坏机制，解决此类隧道围岩稳定性控制困难具有重要理论与实际意义。