本文關(guān)鍵詞：地下工程中若干失穩(wěn)破壞問(wèn)題的機(jī)理和冗余度研究　出處：《天津大學(xué)》2014年博士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： 地下工程 深基坑 隧道 破壞 冗余度 離散元 物質(zhì)點(diǎn)法

【摘要】：在城市化進(jìn)程中，地下空間的利用成為趨勢(shì)。然而由于地下工程固有的復(fù)雜性，使得地下工程事故，例如深基坑的垮塌和隧道開(kāi)挖面的失穩(wěn)等，時(shí)有發(fā)生。然而目前對(duì)于這些失穩(wěn)破壞問(wèn)題的產(chǎn)生發(fā)展機(jī)理、仿真模擬方法及預(yù)防控制理論等研究較少，沒(méi)有形成系統(tǒng)的理論體系，限制了地下工程的建設(shè)與發(fā)展。 本文將大變形計(jì)算方法離散元（DEM）和物質(zhì)點(diǎn)法（MPM）應(yīng)用于若干地下工程失穩(wěn)破壞問(wèn)題的模擬和機(jī)理研究中，同時(shí)針對(duì)地下工程連續(xù)破壞的控制提出冗余度設(shè)計(jì)理論，主要內(nèi)容如下。 （1）對(duì)深基坑工程連續(xù)倒塌和冗余度研究的必要性進(jìn)行了分析，指出基坑工程中冗余度研究的目的、分類(lèi)和作用，并且對(duì)兩個(gè)典型事故中的冗余度問(wèn)題進(jìn)行了剖析，初步總結(jié)了基坑工程中的冗余度設(shè)計(jì)方法。 （2）利用離散元對(duì)基坑環(huán)梁支撐結(jié)構(gòu)的連續(xù)破壞進(jìn)行了模擬，并且提出了一種適用于基坑支撐體系的冗余度評(píng)價(jià)指標(biāo)，進(jìn)而對(duì)不同環(huán)梁支撐方案的冗余度進(jìn)行了定量對(duì)比，結(jié)果表明，利用合理增加傳力路徑等措施可以有效提高支撐體系冗余度。 （3）以探究支撐端部連接對(duì)支護(hù)結(jié)構(gòu)冗余度的影響為出發(fā)點(diǎn)，對(duì)兩種連接情況的基坑的破壞過(guò)程進(jìn)行了離散元模擬，對(duì)其中的連續(xù)破壞現(xiàn)象進(jìn)行了分析。結(jié)果表明支護(hù)體系冗余度的提高可以有效抵抗連續(xù)破壞的發(fā)生，防止基坑在局部破壞情況下導(dǎo)致整體崩潰。 （4）利用有限元和MPM從小變形及大變形兩方面對(duì)兩級(jí)支護(hù)基坑進(jìn)行了剪切滑動(dòng)面開(kāi)展及變形破壞等方面的分析�？偨Y(jié)了無(wú)支撐多級(jí)支護(hù)基坑的變形、穩(wěn)定、剪切面發(fā)展及協(xié)同工作機(jī)理等特點(diǎn)，為進(jìn)一步深入系統(tǒng)分析這種新型支護(hù)方法打下了理論與方法上的基礎(chǔ)。 （5）傳統(tǒng)的隧道開(kāi)挖面穩(wěn)定計(jì)算方法僅能得出穩(wěn)定安全系數(shù)，并不能提供開(kāi)挖面的破壞過(guò)程、破壞形態(tài)及破壞程度等信息。因此將MPM應(yīng)用于隧道開(kāi)挖面的失穩(wěn)破壞模擬中，首先利用已有的離心機(jī)試驗(yàn)結(jié)果和解析方法對(duì)MPM計(jì)算進(jìn)行了驗(yàn)證，進(jìn)而系統(tǒng)研究了土質(zhì)條件、土體強(qiáng)度分布、埋深、無(wú)支護(hù)段長(zhǎng)度等因素對(duì)開(kāi)挖面破壞機(jī)理和程度的影響，為隧道設(shè)計(jì)和風(fēng)險(xiǎn)評(píng)估提供了參考。
[Abstract]:In the process of urbanization, the utilization of underground space has become a trend. However, due to the inherent complexity of underground engineering, underground engineering accidents, such as the collapse of deep foundation pit and the instability of tunnel excavation surface, etc. However, at present, there are few researches on the mechanism, simulation and control theory of these instability and failure problems, and no systematic theoretical system has been formed. It limits the construction and development of underground engineering. In this paper, the discrete element method (DEM) and the material point method (MPM) are applied to the simulation and mechanism study of instability and failure of some underground engineering. At the same time, the redundancy design theory is put forward for the continuous failure control of underground engineering, the main contents are as follows. 1) the necessity of continuous collapse and redundancy study of deep foundation pit engineering is analyzed, and the purpose, classification and function of redundancy research in foundation pit engineering are pointed out. The redundancy problem in two typical accidents is analyzed, and the design method of redundancy in foundation pit engineering is preliminarily summarized. 2) the continuous failure of bracing structure of ring beam of foundation pit is simulated by discrete element, and a redundancy evaluation index suitable for bracing system of foundation pit is put forward. Furthermore, the redundancy of different bracing schemes is compared quantitatively. The results show that the redundant degree of bracing system can be effectively improved by using reasonable increase of load transfer path and so on. In order to explore the influence of support end connection on the redundancy of supporting structure, the failure process of foundation pit with two kinds of connections is simulated by discrete element method. The results show that the increase of redundancy of supporting system can effectively resist the occurrence of continuous failure and prevent the foundation pit from collapsing under the condition of local failure. In this paper, finite element method and MPM are used to analyze the shear sliding surface and deformation failure of two-stage supporting foundation pit, and the deformation of multi-stage braced foundation pit is summarized. The characteristics of stability, shear plane development and cooperative working mechanism lay a theoretical and methodological foundation for further and systematic analysis of this new support method. 5) the traditional calculation method of tunnel excavation surface stability can only obtain the stability safety factor, and can not provide the damage process of the excavated surface. Therefore, MPM is used to simulate the instability of tunnel excavation surface. Firstly, the existing centrifuge test results and analytical methods are used to verify the calculation of MPM. Furthermore, the influence of soil condition, soil strength distribution, buried depth, length of unsupported section on the failure mechanism and degree of excavation surface is studied systematically, which provides a reference for tunnel design and risk assessment.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TU91;TU753

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