深埋工况下的Pasternak模型修正: 土拱效应、隧道下穿、验证

The Pasternak model modification under deep burial conditions:soil-arch effect,tunnel undercrossing,and verification

Pasternak模型是研究新建隧道下穿既有隧道的重要模型,由于深埋工况下土拱效应的作用,采用Pasternak模型研究深埋隧道将导致计算结果偏差较大。为了考虑土拱效应的影响,对Pasternak模型进行了补充和修正,提出了Double Pasternak模型,将深埋隧道视为放置在Double Pasternak上的Euler-Bernoulli梁,从而建立新建隧道下穿深埋隧道的解析分析方法,明确了在理论分析中深埋隧道采用Double Pasternak模型,浅埋隧道采用Pasternak模型。实验研究发现,既有隧道以1.5倍覆跨比为临界点分为深埋隧道和浅埋隧道两部分,深埋隧道覆跨比越大,土拱效应越明显,浅埋隧道土拱效应可忽略不计,证明了不同的埋深模式采用不同弹性地基模型的正确性。将所提计算方法与现场实测结果进行对比,发现计算结果与实测结果有较好的一致性,从而验证了解析解答的正确性。

Pasternak model is an important model to study new tunnels crossing under existing tunnels.Due to the effect of soil-arch effect under deep burial conditions,the use of Pasternak model to study deep tunnels will lead to large deviation of calculation results.In order to consider the influence of soil-arch effect,the Pasternak model is supplemented and modified,leading to the Double Pasternak model.The deep tunnel is regarded as the Euler-Bernoulli beam placed on the Double Pasternak elastic foundation.An analytical analysis method for the longitudinal deformation of the deep tunnel caused by excavation of new tunnel is established.In this situation,the Double Pasternak model is adopted for the deep tunnel and the Pasternak model is adopted for the shallow tunnel.The experimental results show that the existing tunnel can be divided into two parts,that is,the deep tunnel and the shallow tunnel,with 1.5 times of thickness-span ratio as the critical point.The soilarch effect becomes significant with the increase of thickness-span ratio of deep tunnel,and the soilarch effect of shallow tunnel can be ignored,proving that it is correct to use different elastic foundation models for different buried depths.By comparing the proposed calculation results with the field measurements,it is found that the calculated results are in good agreement with the measured ones»thus verifying the correctness of the analytical solution.