ISSN 1003-8035 CN 11-2852/P

    大断面黄土隧道偏压下的裂缝演化机理

    Mechanism of crack development of large cross section loess tunnels under unbalanced load

    • 摘要: 为了研究偏压状态下大断面隧道衬砌开裂情况,探明大断面黄土隧道偏压下的裂缝发展机理,本文依托G30连霍高速公路清水驿至忠和段扩容改造工程-邵家堂公路隧道工程,基于扩展有限元方法在贴合实际工况的拱顶及右拱肩间30°偏压范围下,控制各组施加偏压大小相等,以偏压位置夹角\alpha 为变量对洞口段偏压隧道开裂状况进行了模拟研究。对开裂后衬砌切片提取轴力与弯矩,以内力角度分析了偏压隧道的开裂机理,通过隧道衬砌现场监测数据计算衬砌内力分布同数值模型内力分布对比,验证了模型的合理性。研究结果表明:衬砌在偏压范围内及两侧对称存在受拉受压区域,并在偏压范围衬砌内表面形成形状为\Lambda 的张拉型主裂缝;随着偏压位置夹角\alpha 由10°增大到30°,衬砌裂缝长度由4 m减小到2.8 m,衬砌裂缝深度由9 cm增加到22 cm,呈现出随夹角\alpha 增大衬砌裂缝由向长度方向发展转变为向深度方向扩展趋势;表面裂缝宽度在相同偏压大小下,整体上随着偏压位置夹角\alpha 增大而增大:在0.256 MPa时衬砌开裂,施加偏压达到2.1 Mpa时,30°夹角\alpha 下衬砌表面裂缝宽度最大为3.3 mm,10°夹角\alpha 下裂缝表面宽度为2.4 mm;提取衬砌内力表示:拱顶、右拱肩受偏压影响最大,存在最大轴向拉力及负弯矩;计算得出裂缝截面偏心距随偏压增大而减小,相同偏压大小下,偏压位置夹角\alpha =30°下衬砌裂缝截面偏心距最大,10°最小。本文研究成果可对在役偏压大断面黄土隧道运营维护提供理论参考。

       

      Abstract: In order to study the cracking situation of the lining of large-section tunnel under bias load and clarify the cracking mechanism of large-section loess tunnel under bias load, this paper takes the Shaojiatang highway tunnel project of the G30 Lianhua Expressway expansion project in Qingshuiwei to Zhonghe section as the research object, and based on the extended finite element method under the actual working conditions of the crown and right shoulder with a 30° bias load range, the lining cracking situation in the tunnel mouth section under bias load is simulated by controlling the size of the applied bias load to be equal for each group and taking the angle of the bias load position\alpha as the variable. The axial force and bending moment of the lining cut sections after cracking are extracted, and the cracking mechanism of the bias load tunnel is analyzed by the angle of the internal force. The rationality of the model is verified by calculating the internal force distribution of the lining and comparing it with the numerical model internal force distribution based on the in-situ monitoring data of the lining. The research results show that: there are tensile and compressive regions on both sides of the lining in the bias load range and a tensile main crack is formed on the inner surface of the lining in the shape of \Lambda in the bias load range; as the angle of the bias load position\alpha increases from 10° to 30°, the length of the lining crack decreases from 4 m to 2.8 m, the depth of the lining crack increases from 9 cm to 22 cm, and the trend of the lining crack changing from extending in the length direction to expanding in the depth direction is presented as the angle of the bias load position increases; the width of the surface crack increases overall as the angle of the bias load position \alpha increases; the lining cracks at 0.256 MPa and the maximum surface crack width of the lining at 30° angle of the bias load position\alpha is 3.3 mm, and the surface crack width at 10° angle of the bias load position is 2.4 mm; the internal force extraction shows that the crown and right shoulder are most affected by the bias load, and there is the maximum axial tensile force and negative bending moment; it is calculated that the eccentricity of the crack section decreases as the bias load increases, and the eccentricity of the crack section at the angle of bias load\alpha = 30° is the largest under the same bias load, while the smallest at the angle of 10°. The research results can provide theoretical reference for the operation and maintenance of in-service bias tunnels.

       

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