Dynamic response of RC slab with cushion layer composed of sandy soil to rockfall impact
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摘要:
钢筋混凝土（RC）板与一定厚度的土颗粒缓冲层组合结构被广泛用于山区高位单体及群发性崩塌落石的防治，为研究此类防护结构在落石作用下的冲击力衰减规律及RC板的破坏模式，开展了室外系列落石冲击试验。结果表明，增大缓冲层厚度能够有效减小最大冲击力，峰值加速度随缓冲层厚度减小而增大，尤其在缓冲层厚度为0.1 m及0.2 m时，最大值急剧增大，峰值加速度与缓冲层厚度的变化满足指数函数关系；根据量纲分析原理得到缓冲层最大冲击深度与动能的平方成正比、与最大入射冲击力成反比的计算公式，且与实测值较吻合；入射冲击力在缓冲层内的衰减率随缓冲层厚度的增加以指数函数递增，在0.6 m缓冲层厚度下可使峰值冲击力衰减70%左右；随累积冲击能级的增大，RC板经历了弯曲起裂及扩展、次级弯曲裂纹和剪裂纹产生及跨中弯曲裂纹贯通的过程，试验结束时RC板整体表现出典型的弯曲破坏特征。
Abstract:The structure of reinforced concrete (RC) slab with cushion layer composed of sandy soil is widely used in the prevention and control of high-level single rockfalls and rockfall group in mountainous areas. In order to study the impact attenuation law and the failure mode of RC slab under the rockfall load, an outdoor series impact test was carried out. The results show that an increase in the thickness of the cushion can effectively reduce the maximum impact force, and the peak acceleration increases with the thickness of the cushion, especially when the thickness of the buffer layer is 0.1 m and 0.2 m, the maximum value increases sharply. It can be obviously observed that there exists an exponential relation between the peak acceleration and the thickness of the cushion. According to the principle of dimensional analysis, the maximum impact depth of the cushion layer is directly proportional to the square of the kinetic energy, and the calculation formula is inversely proportional to the maximum incident impact force, respectively. The maximum impact depth of the cushion layer is also in good agreement with the actual measured value. The attenuation rate of the incident impact force in the cushion layer increases exponentially with the increase of the thickness of the cushion, and the peak impact force can be attenuated by about 70% under the thickness of the cushion layer of 0.6 m. With the increase of the cumulative impact energy level, the RC slab undergoes bending initiation and expansion, secondary bending cracks, shear cracks appearing, and further central bending cracks penetration, At the end of the test, the RC slab showed the typical bending failure characteristics.
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Key words:
- rockfall impact test /
- cushion layer /
- attenuation law /
- structure combination /
- failure mode of RC slab
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表 1 缓冲层参数
Table 1. Cushion parameters
天然密度/
(g·cm−3)弹性模量/
MPa含水率/
%泊松比 内摩擦角/
（°）回弹系数 1.54 15 5.39 0.27 30 0 
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表 2 试验冲击工况
Table 2. Conditions for each experiment
落石编号 缓冲层厚度/
m落石高度/
m落石质量/
kg落石体积/
m3最大能量/
kJB1 0.1～0.6 4～7 32.4 0.014 2.2 B2 0.1～0.6 4～7 70.7 0.033 4.9 C1 0.1～0.6 4～7 107.3 0.043 7.4 C2 0.5～0.6 1～7 290.8 0.125 20.0 C2 0.4 1～6 290.8 0.125 17.1
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表 3 典型试验数据
Table 3. Typical tests data
组号 高度/m 冲击力/kN 
/%
混凝土应变/με 钢筋应变/με 位移/mm F0 F1 Sx-8 Sy-11 Sy-14 Sx-17 Gx-2 Gx-6 Gy-10 Gx-11 C1-0.5m 5 107.6 34.5 32.1 102.3 20.5 24.8 56.2 324.8 489.7 47.2 20.0 3.42 6 127.1 44.5 35.0 126.9 23.5 25.3 67.4 409.4 603.0 65.0 45.3 4.28 7 146.0 49.4 33.8 164.0 27.2 26.4 76.0 482.7 667.5 75.9 76.0 4.89 B1-0.3m 5 36.2 17.9 49.5 61.4 5.3 3.0 4.4 191.0 171.7 23.3 10.2 1.41 6 40.1 19.6 48.8 70.0 6.7 6.8 7.5 209.6 183.0 37.2 17.5 1.57 7 42.4 22.3 52.5 77.2 8.4 8.3 11.6 225.9 210.2 42.6 21.0 1.72 B2-0.3m 5 58.5 30.2 51.7 112.2 5.7 4.5 25.0 362.1 397.2 54.1 21.2 2.83 6 67.1 33.0 49.1 126.1 4.0 7.1 31.3 385.2 449.9 124.2 28.8 3.20 7 76.6 38.5 50.2 147.6 10.7 9.1 34.2 414.5 488.1 147.1 43.9 3.45 C2-0.5m 5 224.2 64.1 28.6 555.0 152.5 9.3 72.2 472.8 1321.2 545.0 164.8 11.96 6 239.9 78.7 32.8 910.8 221.8 13.8 133.1 1103.4 1369.1 728.0 204.7 14.94 7 263.9 83.4 31.6 947.0 256.0 17.7 511.3 1250.5 1526.3 1041.2 244.2 18.69
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