【摘要】：本文以蒙華鐵路郭旗隧道工程中出現(xiàn)的黃土隧道地基局部濕陷導(dǎo)致襯砌開裂,圍巖大變形的難點(diǎn)問題為背景,綜合運(yùn)用文獻(xiàn)研究、現(xiàn)場調(diào)研、室內(nèi)土工試驗(yàn)、室內(nèi)模型試驗(yàn)和數(shù)值模擬等方法對黃土隧道地基縱向局部濕陷對襯砌結(jié)構(gòu)的力學(xué)行為影響進(jìn)行了研究。主要研究工作和成果如下:(1)探明了郭旗隧道發(fā)生圍巖大變形和襯砌開裂的根本原因在于隧道穿越具濕陷性黃土地層,隧道地基局部浸水濕陷,地基承載力下降,造成隧道襯砌結(jié)構(gòu)變形和開裂�；诖�,提出了隧道基底縱向局部浸水濕陷后可能出現(xiàn)的兩種潛在破壞的結(jié)構(gòu)受力模式:一是隧道結(jié)構(gòu)呈現(xiàn)"類懸臂梁"受力;二是隧道結(jié)構(gòu)呈現(xiàn)"類簡支梁"受力。(2)由室內(nèi)土工試驗(yàn)表明,黃土的含水率對其強(qiáng)度參數(shù)的影響極其明顯,隨含水率的上升,黃土壓縮模量減小;黃土的內(nèi)摩擦角和黏聚力隨著含水量增加而大幅減小,當(dāng)含水率由9.98%上升至16.52%時(shí),粘聚力下降比達(dá)67.51%。(3)"類懸臂梁"模型試驗(yàn)結(jié)果表明:隧道結(jié)構(gòu)拱頂豎向位移隨浸水濕陷部位含水率的增加而增大,隧道結(jié)構(gòu)拱頂呈現(xiàn)"類懸臂梁"變形規(guī)律;圍巖對結(jié)構(gòu)的壓力隨含水率的變化呈現(xiàn)臺階式遞增或遞減,浸水濕陷部位拱頂和拱底壓力均減小,在臨近浸水濕陷區(qū)域拱頂和拱底壓力均增大;隧道拱頂部位表現(xiàn)為拉應(yīng)變,拱底表現(xiàn)為壓應(yīng)變,同樣在臨近浸水濕陷區(qū)交界處附近應(yīng)變變化最大,在結(jié)構(gòu)未封閉和封閉交界處拱頂拉應(yīng)變較大,因此實(shí)際工程施工過程中應(yīng)特別注意該薄弱部位。(4)"類簡支梁"模型試驗(yàn)結(jié)果表明:隧道結(jié)構(gòu)拱頂豎向位移曲線沉降槽明顯,且隨含水率的增加而增大;隧道結(jié)構(gòu)拱頂出現(xiàn)壓應(yīng)變,拱底出現(xiàn)拉應(yīng)變,最大應(yīng)變均出現(xiàn)在隧道濕陷中心處斷面;浸水濕陷部位拱頂和拱底壓力減小,在臨近浸水濕陷區(qū)域拱頂和拱底壓力增大;為此,隧道結(jié)構(gòu)拱頂在臨近浸水濕陷區(qū)部位可能發(fā)生拉裂破壞,仰拱在濕陷中心處可能發(fā)生拉裂破壞。(5)通過數(shù)值模擬對隧道地基局部浸水濕陷導(dǎo)致的"類懸臂梁"和"類簡支梁"受力模式研究,結(jié)果表明支護(hù)結(jié)構(gòu)拱頂位移,彎曲應(yīng)力和彎矩極值隨浸水濕陷范圍和含水率的增大均增大,說明隧道地基局部浸水導(dǎo)致黃土地基強(qiáng)度減小,地基承載力減弱,初支結(jié)構(gòu)易發(fā)生大變形和產(chǎn)生裂縫。
[Abstract]:Based on the difficult problems of local collapsing of loess tunnel foundation and large deformation of surrounding rock caused by local collapse of loess tunnel foundation in Guoqi tunnel project of Menghua railway, this paper makes comprehensive use of literature research, field investigation, and laboratory geotechnical test. The influence of longitudinal local subsidence of loess tunnel foundation on the mechanical behavior of lining structure was studied by laboratory model test and numerical simulation. The main research works and results are as follows: (1) the main reasons for the large deformation of surrounding rock and the cracking of lining in Guoqi Tunnel are found to be that the tunnel passes through collapsible loess strata, the local soaking of the tunnel foundation collapses, and the bearing capacity of the foundation decreases. Causes tunnel lining structure to deform and crack. Based on this, two potential structural failure modes after longitudinal local immersion and collapse of tunnel foundation are put forward: first, the tunnel structure presents "cantilever beam" force; Second, the tunnel structure shows the force of "like simply supported beam". (2) the results of indoor geotechnical test show that the influence of loess moisture content on its strength parameters is very obvious, and the compression modulus of loess decreases with the increase of water content. The internal friction angle and cohesion force of loess decrease greatly with the increase of water content, and when the moisture content increases from 9.98% to 16.522%, (3) the model test results of "cantilever beam" show that the vertical displacement of the arch roof of tunnel structure increases with the increase of water content in the waterlogged settlement, and the deformation law of the vault of tunnel structure is "like cantilever beam". The pressure of surrounding rock to the structure increases or decreases with the change of water content, the pressure of arch top and arch bottom decreases in the part of water immersion, and the pressure of arch top and arch bottom increases in the area near water immersion. The tensile strain appears at the top of the tunnel and the compressive strain at the bottom of the arch. Similarly, the strain change is the biggest near the junction of the waterlogged zone, and the tensile strain of the vault is larger at the unclosed and closed junction of the structure. Therefore, special attention should be paid to the weak part in the actual construction process. (4) the model test results of "simple supported beam" show that the settlement trough of vertical displacement curve of tunnel structure arch roof is obvious and increases with the increase of water content; The maximum strain appears in the section of the center of the tunnel collapse, the pressure of the arch top and the arch bottom decreases, and the pressure of the arch top and the arch bottom increases in the area near the water immersion collapsing area, and the maximum strain occurs at the center of the tunnel collapsing, and the pressure of the arch top and the arch bottom decreases in the area near the water immersion. For this reason, the tunnel structure dome may take place the tensile crack damage in the area near the waterlogging and collapsing area. Tension crack may occur in the center of the collapse of inverted arch. (5) through numerical simulation, the stress modes of "cantilever beam" and "similar simply supported beam" caused by local soaking and collapsing of tunnel foundation are studied. The results show that the displacement of arch roof of supporting structure is obvious. The maximum value of bending stress and moment increases with the increase of water content and water content, which indicates that local soaking of tunnel foundation leads to the decrease of loess foundation strength, the weakening of foundation bearing capacity, and the occurrence of large deformation and cracks in the initial branch structure.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：U452.11

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