不同进洞高程隧道洞口段大型振动台模型试验研究

随着我国“一带一路”战略对中西部铁路建设投资力度的进一步加大,黄土地震区隧道安全问题日渐突出。如目前已建成的宝兰客运专线、兰渝铁路,正在修建的成兰铁路、银西铁路等都穿越黄土地震带。长期以来,进洞高程作为影响黄土隧道洞口段边坡隧道系统动力响应的重要参数,很少得到关注。因此,将进洞高程作为一个关键参数,借助振动台模型试验与数值模拟分析,定性研究了坡-隧系统动力响应的特点,设计了相似比为1∶70的隧道洞口段边坡隧道系统大型振动台模型试验。坡脚进洞和1/2倍坡高进洞模型试验震害观测结果表明:坡-隧系统坡高、坡角、入射地震波、岩土体材料、填筑方式、衬砌结构相同,进洞高程不同,洞口段破坏形态不同,破坏程度各异。进洞高程对衬砌结构加速度响应的影响与激振幅值的大小密切相关,坡脚进洞的加速度响应远远小于1/2倍坡高处进洞衬砌结构的加速度响应。

Shaking Table Model Test on the Dynamic Response of Tunnel Entrance at Different Elevations

Tunnel safety under earthquakes in loess area has become an increasingly prominent problem along with the intensifying of investment on railway construction in central and western China according to Belt and Road Initiative proposed by China. Some built projects such as Baoji-Lanzhou high-speed railway and Lanzhou-Chongqing railway, and railways under construction, including Chengdu-Lanzhou Railway and Xi’an-Yinchuan Railway, are all running across the loess seismic belt. For a long period of time, the elevation of tunnel entrance, which is an important parameter affecting the dynamic response of loess slope-tunnel system, has received few attention. In view of this, the dynamic response of loess slope-tunnel system is investigated with tunnel entrance elevation as a key parameter via shaking table test and numerical simulation. The similar ratio of slope-tunnel model was 1∶70, and the elevation of tunnel entrance was designed as zero (slope foot) and 1/2 times of slope height, respectively.Test results demonstrate that at different elevations of tunnel entrance, the failure pattern and damage degree of entrance segment are quite different despite the same conditions of slope height, slope gradient, incident earthquake wave, geomaterials, filling mode, and lining structure. The impact of entrance elevation on the acceleration in lining structure is closely related to the magnitude of the excitation amplitude, and the acceleration response of the tunnel lining structure with the entrance elevation at slope foot is much smaller than that with the entrance elevation 1/2 times of the slope height.