为探究更为安全、有效的边坡落石防护结构,本研究基于光滑粒子流体动力学—有限元(SPH-FEM)耦合动力学数值计算及1∶10几何相似室内模型试验,针对“砂土—发泡橡胶”复合垫层棚洞的减振机制展开研究。结果表明:落石以20 m/s速度冲击时,顶板腹部正中单元峰值应力可达2.89 MPa,超过C30砼极限抗拉强度2.01 MPa;添加0.2、0.4、0.6、0.8、1.0 m发泡橡胶垫层后,正中单元峰值应力依次为2.36、1.12、0.79、0.65、0.58 MPa,相较于纯砂土垫层,降幅依次可达18.34%、61.25%、72.66%、77.51%、79.93%;针对试验期间棚洞顶板腹部纵向测点P1,添加2、4、6 cm厚橡胶垫层,其峰值应变由50.57 με依次降至27.17、15.22、10.36 με,降幅为46.27%、69.90%、79.51%;针对顶板腹部横向测试位置T1,复合垫层工况下应变峰值由48.47 με降至26.54、17.29、13.59 με;复合垫层可大幅降低落石冲击能量与顶板应力水平,模型试验与数值计算结果基本相吻合,本文工况下发泡橡胶现场设置厚度以0.4~0.6 m为宜。研究成果可为相关防护工程设计提供借鉴与参考。
In order to explore a more safe and effective slope rockfall protection structure, this study is based on the numerical calculation of SPH-FEM coupled dynamics and the 1∶10 geometric similarity indoor model test, aiming at the vibration reduction mechanism of the "sand-foamed rubber" composite cushion shed tunnel. The results show, when the falling rock is impacted at the speed of 20 m/s, the peak stress of the central unit of the roof abdomen can reach 2.89 MPa, which exceeds the ultimate tensile strength of C30 concrete by 2.01 MPa. After adding 0.2, 0.4, 0.6, 0.8, and 1.0 m foam rubber cushion, the peak stress of the central unit is 2.36, 1.12, 0.79, 0.65, and 0.58 MPa, which is 18.34%, 61.25%, 72.66%, 77.51%, and 79.93% lower than that of the pure sand cushion. Add 2, 4 and 6 cm thick rubber cushion at the longitudinal measuring point P1 on the roof belly of the shed during the test, and the peak strain is 50.57 με. It dropped to 27.17, 15.22 and 10.36 με respectively. The decrease was 46.27%, 69.90% and 79.51%. For the transverse test position T1 of the roof abdomen, the peak strain under the composite cushion condition is 48.47 με to 26.54, 17.29, 13.59 με. The composite cushion can significantly reduce the impact energy of rockfall and the stress level of the roof. The model test and numerical calculation results are basically consistent. The suitable thickness for on-site setting of foam rubber under this working condition is 0.4~0.6 m. The research results can provide reference and reference for relevant protective engineering design.
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