【作者】 杨波；

【导师】 王铁行；

【作者基本信息】 西安建筑科技大学 ， 岩土工程， 2012， 硕士

【摘要】 黄土隧道洞口段病害较多，但目前对其病害成因及相应的处治措施尚难以把握。基于此本文对引起黄土隧道洞口段的主要病害成因进行了总结，并着重针对冻结条件下黄土的水分迁移和冻融条件下黄土隧道洞口段应力变形进行了初步研究。在冻结条件下，黄土的水分迁移呈两段式分布现象。冻结区含水量增大，未冻结区含水量减少。在相同温度梯度、冻结时间和初始含水量下，冻结锋面的含水量和位置随干密度不同而有所变化：干密度较大的含水量小于干密度较小的含水量；干密度较大的位置更靠近冷端。冻融会导致黄土强度发生劣化，现场调查了冻融导致的黄土隧道洞口段病害。在已获得的土性参数的基础上，通过有限元计算得出了冻融循环次数、覆土厚度和冻融深度对隧道洞口段应力及变形的影响。分析得出冻融循环会对拱顶和底部产生附加沉降，冻融循环第一次后对位移影响最大，并且随着覆土厚度和冻融深度的增加，影响越大。冻融循环会导致墙角和拱顶的水平应力、竖向应力降低。在相同冻融区域和分析步下，墙角水平应力和竖向应力随上覆土层厚度增加而增大。另外，随着上覆土层厚度的增加，底部中央区域将产生拉应力，且随着冻融次数的增加逐渐转变为压应力。塑性区分布随冻融循环次数、覆土厚度以及冻融深度的增加而扩大。本文最后提出了针对防止冻融病害发生的处治措施。更多还原

【Abstract】 There are many diseases in loess tunnle entrance.But now the diseases causes andthe corresponding treatment measures is difficult to grasp.Based on this,this article hassummarized the main diseases causes that caused in loess tunnel entrance,and loesswater migration under freeze condition and stress and deformation of loess tunnelentrance under the action of freeze-thaw are emphatically studied.In freezing condition,the moisture migration of loess presents two stagesdistribution phenomenon.Freezing zone moisture content increases, not frozen zonemoisture content decrease.In the same temperature gradient、freezing time and initialwater content,water content and position of the freeze front with dry density differentchanges:water content of the larger dry density is less than water content of smaller drydensity;larger dry density position is more close to the cold end.Freeze-thaw will resultin loess strength degradation happened,scene investigation has been taken for damagesthat caused by the freeze-thaw in loess tunnel entrance.On the basis of soilparameters,freeze-thaw cycle times、thickness of casing soil and freeze-thaw depthinfluence on stress and deformation of the tunnel entrance have been calculated throngfinite element method.Analysis worked out that freeze-thaw cycle generates additionalsettlement on vault and bottom,the biggest influence on displacement appears after thefirst time of freeze-thaw cycle,and larger effect appears along with increase of the coverearth thickness and freeze-thaw depth.Freeze-thaw cycle will lead to horizon stress andvertical stress of corner and vault reduced Under the same freeze-thaw area and analysisstep,horizon stress and vertical stress of corner increased along with the thicknessincrease of the overlying soil.In addition, with the thickness of the overlying soil increased,the central area at the bottom will produce tensile stress after excavation,andwith the increase of number of freeze-thaw gradually change into compressivestress.The distribution of the plastic zone expands with the freeze-thaw cycle times、theincrease of cover earth thickness and the freeze-thaw depth. Treatment measures areproposed to prevent disease caused by freeze-thaw in the end of this article.更多还原