寒区冻融隧道二衬横向渐近偏转演化及力学性态研究

寒区季节性冻融导致围岩破碎层和松动圈的应力应变空间重构,为描述冻融影响下隧道二衬沿断面横向偏转的渐近演化,以吉林老爷岭寒区隧道入口和中段两个代表性断面的拱腰、拱墙390 d现场倾角变形数据为基础,结合衬砌开裂及偏转力学性态特征,应用数值模拟试验,综合分析正温、负温、冻季、融季4时期衬砌渐近性偏转、围岩破碎层及松动圈演化、衬砌应力应变特征等关键问题。研究表明：隧道入口段偏转随季寒交替变化显著,左拱墙和左拱腰测点倾角变化分别呈“倒V”及“下凹”状,偏转在融季响应滞后,在冻季响应超前,在冻融期则有“突变”趋势;而隧道中段受到的影响总体比入口处小,右拱腰在冻季、正温期有不同程度的波动偏转,左拱腰倾角则呈现“上凹”变化,其在融季有滞后偏转现象;计算松动圈直径满足冻融期>负温期>正温期,且隧道入口>隧道中段,通过数值模拟得到塑性区轮廓>计算松动圈,可见在衬砌冻融期的伤害比在其他时期更显著,应防范冻融期温度变化带来的衬砌偏转风险。

Lateral asymptotic deflection evolution and mechanical behavior of secondary linings of freeze-thaw tunnels in cold regions

The seasonal freezing and thawing in cold regions result in the spatial reconstruction of stress and strain in fractured strata and loosening zones of the surrounding rocks. To describe the asymptotic evolution of transverse deflection of tunnel linings under the influences of freezing and thawing, the key characteristics of asymptotic deflection, evolution of rupture layer, loosening zone and stress-strain of linings in the period of positive temperature (PT), negative temperature (NT), frozen season (FS) and melting season (MS) are analyzed based on the 390 days’ in-situ inclination deformation data of the arch waist and wall at tunnel entrance and in the middle section in the Laoyeling cold region of Jilin Province, China. The numerical simulation tests are applied and combined with the mechanical properties of cracking and deflection of linings. The results show that the deflection at tunnel entrance changes significantly with the alternation of seasonal cold. The wall and waist of the left arch are "inverted V"- and "concave"-shaped, respectively. In terms of deflection response, it shows a "lag" in MS and an "ahead" trend in FS, and a "sudden change" trend in MS and FS. And the influence in the middle section of the tunnel is smaller than that at the entrance. The waist of the right arch has different degrees of "fluctuation" deflection in FS and PT, while that of the left arch presents "concave" change, and it has "lag" deflection in MS. The calculated diameter of loosening circle satisfies MS & FS>NT>PT, and that at the entrance is larger than that in the middle of the tunnel. The contour of plastic zone is larger than that of loosening ring by numerical simulation. Therefore, the damage of the linings during the freeze-thaw period is more significant than that in other periods, so the risk of deflection of linings caused by temperature change should be highlighted.