黃土隧道地基縱向局部濕陷對結(jié)構(gòu)的力學(xué)行為影響研究
[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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