Study of Dynamic Response of Soft and Hard Interbedded Rock Slopes under Earthquakes
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摘要: 软硬互层顺层岩质边坡在我国强震区广泛存在，地震极易诱发该类边坡产生地质灾害. 针对地震作用下软硬互层顺层岩质边坡动力响应关键科学问题开展研究，基于离散元数值模拟法，揭示了软硬互层顺层岩质边坡动力响应规律，分析了不同边坡特征因素对其动力响应的影响. 结果表明：地震作用下软硬互层边坡变形破坏主要受软硬岩间层面控制，坡表剪切口和软岩位移增量明显；地震波在传播过程中，软硬岩层对地震加速度具有放大作用，其中软岩的放大作用更明显；地震波频谱特征显示：当地震波从硬岩传播至软岩时，多个固定频段被显著放大，当从软岩传播至硬岩时，频谱有所降低；坡表位移和加速度放大系数随软岩和层面强度的增加而减小，随层厚比的增加而增大；软岩强度和层厚比会改变地震波中显著放大频段的位置，二者增大时，放大频段的数量不变，频率减小；岩层层面强度降低时，放大频段的数量和频率不变，放大程度增大.Abstract: Soft and hard interbedded rock slopes are widely distributed in meizoseismal areas of China and geological disasters are prone to be induced on such slopes due to earthquakes. In this paper, the key scientific issues of the dynamic response of soft and hard interbedded rock slopes under earthquakes were studied. The discrete element numerical simulation method was used to reveal the dynamic response of soft and hard interbedded rock slopes and influences of different slope factors on the dynamic response. The results show that bedding planes between soft and hard rocks play a main control role in the deformation and failure of the slope. Displacements obviously increase on the shear outlets and soft rock of the slope surface. Accelerations of seismic waves are amplified by soft and hard strata during the propagation of seismic wave and soft rocks have a significant amplification effect on the accelerations. The seismic wave spectra show that multiple fixed frequency bands are obviously amplified when the seismic wave propagates from hard rocks to soft rocks; the spectra decrease when the seismic wave propagates from soft rocks to hard rocks. The displacements and the amplification coefficients of acceleration decrease with the increase of the strength of soft rocks and bedding planes, while increase with the increase of thickness ratio. The locations of obviously amplified frequency bands are influenced by the strength of soft rocks and bedding planes. When the strength of soft rocks and bedding planes increase, the number of amplified bands remains the same and frequencies decrease. The reduction of the strength of bedding planes will not change the number and frequency of the amplified bands, but increase the degree of amplification.
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图 1 软硬互层顺层岩质边坡数值模型(单位：m)
Fig. 1. Numerical model of soft and hard interbedded rock slope (unit: m)
图 2 El Centro地震波加速度时程曲线
Fig. 2. Time-history curve of acceleration of El Centro seismic wave
图 6 竖直和水平方向监测点PGA
a.垂直方向各点PGA；b. 水平方向各点PGA
Fig. 6. PGA of monitoring sites in vertical and horizontal directions
图 7 不同位置监测点加速度的傅氏谱
a. 模型底部；b. 模型中部；c.模型顶部
Fig. 7. Fourier spectra of acceleration of monitoring sites at different locations
图 8 不同软岩强度下坡表各点最大位移和测线1上各点PGA
a. 坡表监测点最大位移；b. 测线1上监测点PGA
Fig. 8. Maximum displacements of monitoring sites on slope surface and PGA at test line 1 under different strength of soft rock
图 9 不同软岩强度下A1监测点加速度傅式谱
a. 强度1；b. 强度2；c. 强度3
Fig. 9. Fourier spectra of acceleration of A1 monitoring site under different strength of soft rock
图 10 不同岩层层面强度下坡表各点最大位移和测线1上各点PGA
a. 坡表监测点最大位移；b. 测线1上监测点PGA
Fig. 10. Maximum displacements of monitoring sites on slope surface and PGA at test line 1under different strength of bedding plane
图 11 不同岩层层面强度下A1监测点加速度傅式谱
Fig. 11. Fourier spectra of acceleration of A1 monitoring site under different strength of bedding plane
图 12 不同层厚比下坡表各点最大位移和测线1上各点PGA
a. 坡表监测点最大位移；b. 测线1上监测点PGA
Fig. 12. Maximum displacements of monitoring sites on slope surface and PGA of monitoring sites at test line 1 under different thickness ratio
图 13 不同层厚比下A1监测点加速度傅式谱
a. 层厚比0.5；b. 层厚比1；c. 层厚比1.5
Fig. 13. Fourier spectra of acceleration of A1 monitoring site under different thickness ratio
表 1 岩石物理力学指标
Table 1. Physical and mechanical indices of rock
序号 密度(kg·m-3) 粘聚力(MPa) 内摩擦角(°) 体积模量(GPa) 剪切模量(GPa) 抗拉强度(MPa) 1
2
3
42 000
2 150
2 350
2 6500.30
0.45
0.60
1.5030
35
40
500.17
0.83
3.48
10.000.11
0.48
1.38
5.400.10
0.22
0.60
0.80
下载: 导出CSV
表 2 岩层层面物理力学指标
Table 2. Physical and mechanical indices of bedding plane
序号 粘聚力(MPa) 内摩擦角(°) 法向刚度(GPa·m-1) 切向刚度(GPa·m-1) 1
2
30.1
0.1
0.120
30
4012
12
126
6
6
下载: 导出CSV
表 3 数值模拟加载方案
Table 3. Loading schemes of numerical simulation
工况 软岩强度 岩层层面强度 层厚比 1
2
3
4
5
6
71
2
3
3
3
3
3B
B
B
A
C
B
B1.0
1.0
1.0
1.0
1.0
0.5
1.5
下载: 导出CSV
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