浅埋偏压小净距隧道地震响应特性研究

发布时间：2018-08-25 12:52

【摘要】：我国西南地区地质条件复杂、地震频发,特别是部分地区还属于高烈度地震区,地震区隧道工程就必须解决地震条件下隧道稳定性的问题。在山区修建隧道时,受到特殊地形及地质条件、桥隧搭接方式等因素的限制,双洞隧道的左右洞间距已经不能保证达到规范的要求,为此修建了较多的浅埋偏压小净距隧道。由于此隧道形式在地震下的响应情况还不明确,也少见于文献报道,故本文利用振动台试验研究浅埋偏压小净距隧道在地震下的响应规律,探究其地震响应机理。本文以国家自然科学基金项目“含地下洞室(群)岩石边坡地震灾变行为与抗震性能评价"(编号:51204125)为依托,开展了浅埋偏压小净距隧道的大型振动台试验,并采用MidasGTS/NX软件对左右洞隧道在不同方向、不同加速度峰值的汶川波作用下隧道的响应规律进行了分析。主要研究内容与结论如下:(1)进行大型振动台模型试验,得出了在不同方向、不同加速度峰值汶川地震波输入下浅埋偏压小净距隧道模型的加速度与动应变响应规律,并分析其原因与特性。认为衬砌加速度受地震波的入射方向影响较大,且Z向的影响大于X向,XZ双向的影响大于单向。左洞隧道的加速度响应大于右洞隧道。左洞隧道的左半部分,由于埋深较浅、接近临空坡面,且地震波在坡面会产生波场分裂现象,不同类型的波叠加形成复杂的波场,对隧道衬砌的加速度影响较大。右洞隧道的拱顶和拱脚区域加速度响应较为剧烈,是抗震设防应着重考虑的部位。(2)衬砌应变受地震加速度峰值的影响较大。隧道衬砌在地震作用下承受拉压循环荷载,以受拉为主。右洞隧道衬砌的动应变响应大于左洞隧道。右洞隧道由于上覆岩层较厚,在地震作用下,隧道衬砌的拱脚处,拉压应变变化剧烈,是最危险的区域。在对衬砌进行配筋时,左洞隧道应采取非对称配筋,在接近临空面的部分适当增加配筋率。隧道的拱脚处应配置双向受力钢筋,防止拉压破坏。(3)建立地震作用下浅埋偏压小净距隧道的数值计算三维数值模型,得到了在相同工况下隧道的加速度、内力等响应规律,并通过隧道衬砌的加速度进行对比分析,验证了数值模型的可靠性。利用数值模型计算了地震作用下隧道横截面和纵向的轴力、弯矩和剪力值,隧道横截面的拱脚部位内力值最大,沿隧道的纵向内力值变化不大。
[Abstract]:The geological conditions in southwest China are complicated and the earthquakes occur frequently, especially in some areas, which belong to the high-intensity seismic area. Tunnel engineering in the seismic area must solve the problem of tunnel stability under earthquake conditions. In the construction of tunnels in mountainous areas, due to special terrain and geological conditions, bridge and tunnel overlap mode and other factors, the distance between left and right tunnels of double-hole tunnel can no longer meet the requirements of the code. For this reason, more shallow burying tunnels with small offset and clear spacing have been built. Because the response of this tunnel form under earthquake is not clear, and is seldom reported in the literature, this paper studies the response law of shallow bias pressure and small net distance tunnel under earthquake by shaking table test, and probes into its seismic response mechanism. Based on the project of National Natural Science Foundation, "earthquake disaster behavior and Seismic performance Evaluation of Rock Slope with Underground cavern (Group)" (No.: 51204125), a large-scale shaking table test of a tunnel with shallow partial pressure and small spacing is carried out in this paper. MidasGTS/NX software is used to analyze the response law of the tunnel under the action of Wenchuan wave in different directions and different acceleration peaks. The main research contents and conclusions are as follows: (1) the response law of acceleration and dynamic strain of the tunnel model with small net distance of shallow buried bias under different direction and different acceleration peak value Wenchuan earthquake wave input is obtained by the model test of large shaking table. The causes and characteristics are analyzed. It is considered that the lining acceleration is greatly affected by the incident direction of seismic wave, and the influence of Z direction is greater than that of X direction XZ direction is greater than that of one direction. The acceleration response of the left tunnel is larger than that of the right tunnel. The left half of the left side of the left tunnel is shallow in depth, close to the slope surface, and the seismic wave will produce wave field splitting phenomenon on the slope surface. Different types of wave superposition form complex wave field, which has a great influence on the acceleration of tunnel lining. The acceleration response of the arch roof and arch foot of the right tunnel is more intense, which should be considered in seismic fortification. (2) the lining strain is greatly affected by the peak seismic acceleration. The tunnel lining is subjected to the cyclic load of tension and compression under earthquake action, mainly under tension. The dynamic strain response of right tunnel lining is larger than that of left tunnel. Due to the thick overlying strata in the right tunnel, the tension and compression strain of the arch of the tunnel lining changes sharply under the earthquake, which is the most dangerous area. When lining is reinforced, asymmetric reinforcement should be adopted in the left tunnel, and the reinforcement ratio should be increased appropriately in the part near the empty surface. In order to prevent the damage of tension and compression, the tunnel arch should be equipped with bidirectional steel bar. (3) the numerical model of shallow buried bias small net distance tunnel under earthquake action is established, and the response law of tunnel acceleration and internal force under the same working condition is obtained. The reliability of the numerical model is verified by comparing and analyzing the acceleration of tunnel lining. The axial force, bending moment and shear force of the tunnel cross section and longitudinal are calculated by using the numerical model. The internal force of the arch foot of the tunnel cross section is the largest, but the longitudinal force along the tunnel does not change much.
【学位授予单位】：中南林业科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U452.28

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