基于强度折减法的既有隧道安全度研究

发布时间：2018-02-01 13:52

本文关键词： 既有隧道强度折减安全系数破坏机理劣化　出处：《西南交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：本文将有限元强度折减法引入到既有隧道安全度的研究中,并以安全系数作为安全度的判断标准,在均一地层下建立地层—荷载结构模型,对隧道的支护力学行为、隧道基于不同埋深和不同洞型的破坏机理、既有隧道在围岩劣化和衬砌劣化时的安全度、既有隧道在二次衬砌局部厚度不足时的安全度进行了计算分析。本文的主要结论如下：(1)利用有限元差分软件FLAC3D,基于强度折减法,通过隧道开挖后释放荷载的控制来等效模拟隧道的支护时机效应,计算分析了隧道的支护力学行为,计算结果表明,支护时机对隧道最终的安全系数影响很小,为既有隧道安全评价的数值模拟提供计算依据。(2)通过强度折减法,对不同埋深和不同洞型隧道的破坏机理进行研究,为既有隧道的破坏机理解析提供参考。计算分析表明,隧道随着埋深的增加,安全系数呈现先增加、后减小的趋势。对于不同洞型,矩形洞室破坏形式不受埋深影响,均从洞室顶部破坏；直墙拱隧洞在浅埋时拱顶首先破坏,深埋时墙脚首先破坏；圆形隧洞与马蹄形隧洞的破坏机理相似,浅埋时拱顶首先破坏,深埋时边墙首先破坏。4种断面形式中圆形断面最为安全,马蹄形次之,矩形最不安全。(3)既有隧道产生围岩和衬砌的全部劣化时,隧道的安全系数随着劣化程度的增加而减小。围岩不同深度劣化时,当劣化深度在lm-2m,3m-4m过程中安全系数减小较多；不同部位围岩局部劣化时,仰拱处最为不利。初支全部劣化时,劣化前期安全系数降低较快；初支局部劣化时,墙脚部位劣化最为不利,边墙和仰拱次之。二衬全部劣化时,随着劣化程度的增加,安全系数减小较快；二衬局部劣化时,拱顶和拱腰局部劣化时最为不利。二衬局部厚度不足时,随着二衬厚度的减小,安全系数不断减小,其中厚度不足对拱顶和边墙部位最为不利。
[Abstract]:In this paper, the finite element strength reduction method is introduced into the study of the safety degree of the existing tunnel, and the safety factor is taken as the criterion of safety degree, and the stratigraph-load structure model is established under the uniform stratum. For the tunnel supporting mechanics behavior, the tunnel based on different buried depth and different hole type failure mechanism, the existing tunnel in the surrounding rock deterioration and lining deterioration safety degree. The safety degree of the existing tunnel is calculated and analyzed when the local thickness of the secondary lining is insufficient. The main conclusions of this paper are as follows: (1) based on the strength reduction method, the finite element difference software FLAC3D is used. Through the control of the release load after the tunnel excavation, equivalent simulation of the tunnel support timing effect, calculated and analyzed the tunnel supporting mechanical behavior, the results show that the supporting time has little effect on the tunnel ultimate safety factor. The failure mechanism of tunnel with different buried depth and different tunnel type is studied by strength reduction method. It provides a reference for the analysis of the failure mechanism of the existing tunnel. The calculation and analysis show that the safety factor of the tunnel increases first and then decreases with the increase of the buried depth. The failure forms of rectangular caverns are not affected by the depth of burying, and are destroyed from the top of the cavern. When the tunnel is shallow buried, the arch roof is destroyed first, and the foot of the wall is destroyed first when buried deeply. The failure mechanism of circular tunnel is similar to that of horseshoe tunnel. The arch top is first destroyed when shallow is buried, and the circular section is the safest in deep burying, and the horseshoe is the second. The safety coefficient of the tunnel decreases with the increase of the deterioration degree when the tunnel has all the deterioration of surrounding rock and lining. When the surrounding rock is deteriorating at different depth, the depth of deterioration is in lm-2m. The safety factor decreases more in 3m-4m process. When the local deterioration of surrounding rock is different, the inverted arch is the most disadvantageous. When all the initial branches are degraded, the safety coefficient of the early stage of deterioration decreases rapidly. In the local deterioration of the first branch, the deterioration of the foot of the wall is the most unfavorable, followed by the side wall and the inverted arch. When the second lining is all degraded, the safety factor decreases faster with the increase of the deterioration degree. When the local thickness of the second liner is insufficient, the safety factor decreases with the decrease of the thickness of the second liner. The lack of thickness is most disadvantageous to the arch and the side wall.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U457.2

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