Abstract: A design scheme for river sand cushion layer shed tunnel was proposed considering the concept of buffer travel. Based on the hazardous rock and rockfall disaster at the entrance of a certain tunnel project, an indoor test model was constructed, and a shed tunnel calculation model using the SPH-FEM coupling algorithm was established. The research results show that compared to traditional sand cushion layer, the peak stress at the central measuring point of the river sand cushion layer shed tunnel roof decreases by 42.52%, the peak compressive stress of the column decreases by 65.77%, and the peak rockfall acceleration decreases by 56.84%. Compared to the sand cushion layer, the depth of the impact pit of the falling ball in the river sand cushion layer has increased from 28.54 mm to 58.24 mm, with an increase of 50.99%. Under the condition of river sand cushion layer, the impact penetration buffering stroke of the falling stone is much higher than that of the sand cushion layer, thereby improving the energy dissipation and seismic reduction effect of the river sand cushion layer shed tunnel. The actual size shed tunnel structure model is reconstructed again. After the river sand cushion layer is laid, the peak stress of the abdominal unit of the roof decreases by 53.41%, the peak displacement of the abdominal unit of the roof decreases by 34.44%, and the peak rockfall acceleration decreases by 55.41%.

Key words: tunnel engineering; rockfall impact; shed tunnel structure; river sand cushion layer; model testing; SPH-FEM

摘要： 在考虑缓冲行程理念下提出了河砂垫层棚洞设计方案，依托某隧道工程洞口危岩落石灾害，构建了室内试验模型，建立了SPH-FEM耦合算法的棚洞计算模型。研究结果表明：相较于传统砂土垫层，河砂垫层棚洞顶板中心测点应力峰值降幅达42.52%，立柱压应力峰值降幅达65.77%，落石加速度峰值降幅达56.84%；相较于砂土垫层，河砂垫层下落球冲击坑深度由28.54 mm增加至58.24 mm，增幅达50.99%，河砂垫层情况下落石的冲击侵彻缓冲行程远高于砂土垫层，以此提升了河砂垫层棚洞耗能减震效果；再次构建实际尺寸棚洞结构模型，当铺设河砂垫层后顶板腹部单元应力峰值降幅达53.41%，顶板腹部单元位移峰值降幅34.44%，落石加速度峰值降幅达55.41%。

关键词: 隧道工程；落石冲击；棚洞结构；河砂垫层；模型试验；SPH-FEM