双碑隧道加宽带安全度研究

发布时间：2018-10-17 08:54

【摘要】：以重庆双碑隧道为实际工程背景，按照该双碑隧道加宽段与普通段的实际开挖断面尺寸、围岩和初期支护材料参数以及施工方法，采用大型有限元软件迈达斯GTS模拟隧道加宽带施工过程，分析双碑隧道加宽带仅在初期支护的作用下围岩的稳定性、各工况下的安全系数以及加宽段与普通段结合处（变截面）的位移，应力及支护参数的合理性。 ①采用有限元软件迈达斯GTS建立二维有限元模型，应用强度折减法对实际的四种工况（埋深100m III级围岩双洞、埋深100mIV级围岩双洞（台阶法）、埋深100mIV级围岩双洞（双侧壁法）、埋深在150mIV级围岩单洞）下，，对围岩及初期支护做弹塑性数值模拟分析；重点分析了隧道加宽段的位移随着强度折减系数变化的曲线，根据隧道失稳的判据，得到各工况下的安全系数；以及在实际的支护参数下，围岩的位移，应力和塑性区的分布规律；并对施工方案进行了比选。 ②通过建立三维有限元模型，在埋深100m III级围岩工况下，分析对双碑隧道加宽带与普通段结合处（变截面）过渡段的整体稳定性，分析过渡段围岩在实际初期支护参数下的位移，应力和塑性区特征，同时分析喷混层的受力情况，得出过渡段变截面的最不利受力位置。通过以上研究方法得到以下结论： ①各个工况下加宽段的安全系数不同，最小值为在埋深在150mIV级围岩工况下安全系数值为2，最大值为埋深100m III级围岩双洞工况下安全系数为4.6。 ②无论是从围岩位移还是从支护结构应力情况，加宽段与普通段结合处（变截面）最不利位置均在右侧拱腰，水平收敛值达到开挖跨度的0.6%，同时喷混层出现了拉应力，且数值达到了0.323Mpa，因此施工时应注意对变截面处的加固，必要时可增加端承处的喷射混凝土厚度，或者在端承处也植入锚杆，保证变截面的安全。
[Abstract]:Based on the actual engineering background of Chongqing Shuangbei tunnel, according to the actual excavation section size of the widening section and ordinary section of the tunnel, the parameters of surrounding rock and initial supporting material and the construction method, The large finite element software Midas GTS is used to simulate the construction process of tunnel plus wide band, and the stability of surrounding rock under the action of initial support is analyzed. The safety factor and displacement, stress and support parameters at the joint of widening section and ordinary section (variable section) are reasonable under each working condition. 1 A two-dimensional finite element model is established by using the finite element software Midas GTS. The strength reduction method is applied to the actual four working conditions (100m deep III class wall rock double hole, buried depth 100mIV class wall rock double hole (step method), buried depth 100mIV class surrounding rock double hole (double lateral wall method), buried depth in 150mIV class surrounding rock single hole). Elastoplastic numerical simulation analysis of surrounding rock and initial support is made, and the curve of displacement with strength reduction coefficient in widening section of tunnel is analyzed emphatically. According to the criterion of tunnel instability, the safety factor under each working condition is obtained. And the distribution law of displacement, stress and plastic zone of surrounding rock under the actual supporting parameters. 2 through the establishment of three-dimensional finite element model, under the condition of 100m III surrounding rock, This paper analyzes the overall stability of the transition section (variable section) in the joint of double tablet tunnel with wide band and common section, analyzes the displacement, stress and plastic zone characteristics of the surrounding rock of the transition section under the actual initial supporting parameters, and analyzes the stress situation of the shotcrete layer at the same time. The most unfavorable force position of the transition section is obtained. The conclusions are as follows: (1) the safety factor of the widening section is different under different working conditions. The minimum value is that the safety coefficient of buried depth is 2 under the condition of 150mIV class surrounding rock, and the maximum value is 100 m III grade surrounding rock under double tunnel condition. The safety factor is 4.6 2 whether from the displacement of surrounding rock or from the stress of supporting structure. The most unfavorable position at the joint (variable section) of the widening section and the common section is in the right arch waist, the horizontal convergence value reaches 0.6 of the excavation span, and the tensile stress appears in the mixing layer and the value reaches 0.323 Mpa.Therefore, attention should be paid to the reinforcement of the variable section in construction. The thickness of shotcrete can be increased when necessary, or anchors can be inserted at the end supports to ensure the safety of variable sections.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U452.1;U458

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