礼让隧道石膏质围岩软化机理及模型研究

发布时间：2018-06-23 19:59

本文选题：石膏岩 + 软化试验　；参考：《重庆大学》2015年硕士论文

【摘要】：重庆梁忠高速礼让隧道穿越300m长的石膏层,石膏岩遇水易软化,对隧道施工安全构成严重的威胁,针对这一工程病害特点,本文对石膏岩进行了一系列的软化试验研究,为解决工程实际问题建立了相应的理论模型及工程应用模型。本文主要开展了以下几个方面的研究工作:①对国内外石膏岩及相类似软岩的研究现状进行分析和总结,拟定本文的主要研究内容和技术路线;对礼让隧道工程地质特征进行分析,着重分析了与石膏岩软化密切相关的水文地质条件。②对礼让隧道石膏质围岩的力学性质进行了试验研究,开展了单轴、三轴试验及剪切试验,获得了石膏岩的单轴抗压强度、弹性模量、抗剪强度、泊松比等基本力学参数,其弹性模量和单轴抗压强度均较低,属于软岩的范畴,岩石破坏形式呈脆性破坏。③针对石膏岩开展了一系列的软化试验及细观试验,揭示了石膏岩各项力学参数随浸泡时间的演化规律,并拟合出了相应的软化方程。石膏岩的单轴抗压强度、抗剪强度、弹性模量均随浸泡时间呈负指数趋势下降,而石膏岩泊松比在一定条件下随浸泡时间的增加而增加;在损伤力学基础上,推导出了基于时间因素的石膏岩软化损伤演化方程,揭示了脆性系数与软化损伤变量之间的内在关联,建立了石膏岩在不同淡水浸泡时间下的软化深度模型。基于压汞试验数据分析,发现石膏岩的孔隙率随浸泡时间的增加而增大,相应宏观表现为石膏岩单轴压缩过程中孔隙压密阶段延长、变形量增加;随着浸泡时间的增长,石膏岩性质发生改变,逐渐由脆性向延性转变。④通过分析正交软化试验结果,揭示了浸泡时间、温度和SO42-浓度等因素对石膏岩软化的影响规律,运用层次分析法计算出了各个因素的影响权重,结果表明:浸泡时间和温度在石膏岩软化过程中起决定性的作用,浸泡时间和温度的影响权值之和大于97%,其中浸泡时间的影响权值最大,超过80%,温度次之,而SO42-浓度对石膏岩的软化影响几乎为零,可以忽略不计。⑤在考虑石膏岩软化特性、获得弹性模量和泊松比随浸泡时间的变化规律的前提下,基于圆形轴对称隧道平面应变弹性解,建立了考虑软化效应的隧道围岩自稳时间评价模型。对模型进行了参数分析,在相同跨度下,自稳时间随隧道埋深的增加而减小,随完整性系数的增大而增加,随着地下水系数的增大而减小,围岩弹性模量越大自稳时间越长。分析结果表明,本文给出的考虑软化效应的隧道围岩自稳时间评价模型与实际情况相符,说明了该模型的科学性与合理性。并针对模型中关于地下水分布特征的简化问题进行了讨论,推导出考虑地下水分布特征的弹性模量及泊松比的取值公式。基于现场数据和软化试验结果,使用该模型对礼让隧道石膏段围岩自稳时间进行了评价。
[Abstract]:Through the 300m long gypsum layer of Liangzhong High-speed Liangzhong Tunnel in Chongqing, the gypsum rock is easy to soften when it meets water, which poses a serious threat to the safety of tunnel construction. In view of the characteristics of this engineering disease, a series of softening tests on gypsum rock have been carried out in this paper. In order to solve the practical engineering problems, the corresponding theoretical model and engineering application model are established. This paper mainly carried out the following aspects of research work: 1 to domestic and foreign gypsum rock and similar soft rock research status analysis and summary, draw up the main research content and technical route of this paper; Based on the analysis of the engineering geological characteristics of Licheng tunnel, the hydrogeological conditions .2, which are closely related to the softening of gypsum rock, are analyzed, and the mechanical properties of the gypsum surrounding rock of the Licheng tunnel are studied experimentally and uniaxially. The uniaxial compressive strength, elastic modulus, shear strength and Poisson's ratio of gypsum rock are obtained by triaxial test and shear test. The elastic modulus and uniaxial compressive strength of gypsum rock are lower and belong to the category of soft rock. A series of softening tests and meso tests were carried out on gypsum rock in the form of brittle failure. 3. The evolution of mechanical parameters of gypsum rock with immersion time was revealed, and the corresponding softening equation was fitted. The uniaxial compressive strength, shear strength and elastic modulus of gypsum rock decrease exponentially with immersion time, while Poisson's ratio of gypsum rock increases with the increase of soaking time under certain conditions. The evolution equation of softening damage of gypsum rock based on time factor is derived, and the inherent relation between brittle coefficient and softening damage variable is revealed, and the softening depth model of gypsum rock under different fresh water immersion time is established. Based on the analysis of mercury injection test data, it is found that the porosity of gypsum rock increases with the increase of soaking time, and the corresponding macroscopic behavior is that the pore compaction stage is prolonged and the deformation amount increases during uniaxial compression of gypsum rock, and with the increase of soaking time, the porosity of gypsum rock increases with the increase of immersion time. The properties of gypsum rock change gradually from brittleness to ductility. By analyzing the results of orthogonal softening test, the effects of soaking time, temperature and so _ 42- concentration on the softening of gypsum rock are revealed. The influence weight of each factor is calculated by AHP. The results show that the soaking time and temperature play a decisive role in the softening process of gypsum rock. The sum of the influence weights of soaking time and temperature is greater than 97, in which the influence weight of soaking time exceeds 80, followed by temperature, and the effect of so _ 42- concentration on the softening of gypsum rock is almost zero, which can be ignored when considering the softening characteristics of gypsum rock. Based on the elastic modulus and Poisson's ratio changing with immersion time and based on the plane strain elastic solution of circular axisymmetric tunnel, a self-stability time evaluation model of tunnel surrounding rock considering softening effect is established. Under the same span, the self-stability time decreases with the increase of the tunnel depth, increases with the increase of the integrity coefficient, decreases with the increase of the groundwater coefficient, and increases with the increase of the elastic modulus of surrounding rock. The analysis results show that the evaluation model of self-stability time of tunnel surrounding rock considering softening effect is consistent with the actual situation, which shows that the model is scientific and reasonable. The simplified problem of groundwater distribution characteristics in the model is discussed, and the formula of elastic modulus and Poisson's ratio considering the characteristics of groundwater distribution is derived. Based on field data and softening test results, the self-stability time of surrounding rock in gypsum section of Licheng tunnel is evaluated by using the model.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U451.2

【相似文献】