黄土隧道地基纵向局部湿陷对结构的力学行为影响研究
发布时间：2018-11-26 19:14
【摘要】：本文以蒙华铁路郭旗隧道工程中出现的黄土隧道地基局部湿陷导致衬砌开裂,围岩大变形的难点问题为背景,综合运用文献研究、现场调研、室内土工试验、室内模型试验和数值模拟等方法对黄土隧道地基纵向局部湿陷对衬砌结构的力学行为影响进行了研究。主要研究工作和成果如下:(1)探明了郭旗隧道发生围岩大变形和衬砌开裂的根本原因在于隧道穿越具湿陷性黄土地层,隧道地基局部浸水湿陷,地基承载力下降,造成隧道衬砌结构变形和开裂。基于此,提出了隧道基底纵向局部浸水湿陷后可能出现的两种潜在破坏的结构受力模式:一是隧道结构呈现"类悬臂梁"受力;二是隧道结构呈现"类简支梁"受力。(2)由室内土工试验表明,黄土的含水率对其强度参数的影响极其明显,随含水率的上升,黄土压缩模量减小;黄土的内摩擦角和黏聚力随着含水量增加而大幅减小,当含水率由9.98%上升至16.52%时,粘聚力下降比达67.51%。(3)"类悬臂梁"模型试验结果表明:隧道结构拱顶竖向位移随浸水湿陷部位含水率的增加而增大,隧道结构拱顶呈现"类悬臂梁"变形规律;围岩对结构的压力随含水率的变化呈现台阶式递增或递减,浸水湿陷部位拱顶和拱底压力均减小,在临近浸水湿陷区域拱顶和拱底压力均增大;隧道拱顶部位表现为拉应变,拱底表现为压应变,同样在临近浸水湿陷区交界处附近应变变化最大,在结构未封闭和封闭交界处拱顶拉应变较大,因此实际工程施工过程中应特别注意该薄弱部位。(4)"类简支梁"模型试验结果表明:隧道结构拱顶竖向位移曲线沉降槽明显,且随含水率的增加而增大;隧道结构拱顶出现压应变,拱底出现拉应变,最大应变均出现在隧道湿陷中心处断面;浸水湿陷部位拱顶和拱底压力减小,在临近浸水湿陷区域拱顶和拱底压力增大;为此,隧道结构拱顶在临近浸水湿陷区部位可能发生拉裂破坏,仰拱在湿陷中心处可能发生拉裂破坏。(5)通过数值模拟对隧道地基局部浸水湿陷导致的"类悬臂梁"和"类简支梁"受力模式研究,结果表明支护结构拱顶位移,弯曲应力和弯矩极值随浸水湿陷范围和含水率的增大均增大,说明隧道地基局部浸水导致黄土地基强度减小,地基承载力减弱,初支结构易发生大变形和产生裂缝。
[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.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U452.11
本文编号：2359382
[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.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U452.11
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