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Laboratory model test study on strengthening landslide dam material by vibroflotation method
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摘要: 为丰富堰塞坝开发利用理论，探究其改良加固的可行性，对易贡大滑坡残存的天然堰塞体进行取样，设计了不同频率的室内振冲模型试验，研究了振冲法对堰塞体材料的加固效果和密实机理。模型试验采用砂雨法制样，综合测试了振冲后地基的孔压累计消散规律、土压力发展规律，加固效果和复振效应等。试验结果表明：在振冲器的贯入过程中，松散堰塞料中的土压力和超静孔压迅速上升，在振冲器的上拔和分段留振作用下，堰塞料的超静孔压表现为小幅上升和消散、逐渐稳定的总体趋势。随着振冲次数的增加（2~3次复振后），堰塞料地基的土压力逐渐稳定，超静孔压峰值逐渐下降并趋于稳定。因此振冲对松散堰塞体材料的加固效果明显，振冲后堰塞体材料的锥尖阻力大幅提升，但堰塞料密实后，进一步提高复振次数不能有效改善加固效果。满足易贡堰塞体材料的振冲设计方案为：采用125 Hz频率进行4~5次振冲，或采用150 Hz频率进行2~3次振冲。研究结果可为堰塞坝料地基的振冲加固提供理论依据。Abstract: In order to enrich the theory on development and utilization of landslide dam and explore the feasibility of its improvement and reinforcement, the residual landslide dam caused by Yigong landslide was sampled, the indoor vibroflotation model tests with different frequencies were designed, and the reinforcement effect and compaction mechanism of vibroflotation method on landslide dam material were studied. The sand rain method was used for the sample placement in the model tests to comprehensively test the cumulative dissipation law of pore pressure, the development law of earth pressure, reinforcement effect and repeating vibration effect of the foundation after vibroflotation. The test results indicate that the earth pressure and excess pore pressure in the loose landslide dam material rise rapidly during the penetration of the vibrator. Under the pull-up and segmental vibration retention of the vibrator, the excess pore pressure of the landslide dam material showed a general trend of small rise, dissipation and gradual stability. With the increasing number of vibroflotation (after 2-3 repeated vibrations), the soil pressure of the foundation gradually stabilized, and the peak value of excess pore water pressure gradually decreased and tended to be stable. Therefore, the reinforcement effect of vibroflotation on loose landslide dam material was obvious. After vibroflotation, the cone resistance of landslide dam material was greatly increased. However, after the densification of landslide dam material, the increasing number of repeated vibrations was unable to further improve the reinforcement effect effectively. The vibroflotation reinforcement mechanism of landslide dam material mainly included vibrator squeezing, consolidation drainage, and vibroflotation compaction. The vibroflotation design scheme meeting the requirements of Yigong landslide dam material was: vibroflotation with 125 Hz frequency for 4-5 times or vibroflotation with 150 Hz frequency for 2-3 times. The research results can provide a theoretical basis for vibroflotation reinforcement of landslide dam material foundation.
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Key words:
- landslide dam material /
- vibroflotation /
- frequencies /
- reinforcement effect /
- reinforcement mechanism
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图 2 堰塞坝原状材料和试验材料的级配曲线
Figure 2. Grading curve of undisturbed material and test material of landslide dam
图 3 振冲器贯入、留振和上拔过程中的孔压变化
Figure 3. Variation of excess pore pressure during penetration, retention and pull-up of vibrator
图 4 100 Hz频率下超静孔压峰值随振冲次数的变化
Figure 4. Variation of peak value of excess pore water pressure with vibration number at 100 Hz frequency
图 5 125 Hz频率下超静孔压峰值随振冲次数的变化
Figure 5. Variation of peak value of excess pore water pressure with vibration number at 125 Hz frequency
图 6 150 Hz频率下超静孔压峰值随振冲次数的变化
Figure 6. Variation of peak value of excess pore water pressure with vibration number at 150 Hz frequency
图 7 不同振动频率下深度70 cm，径向20 cm处动土压力随时间的变化曲线
Figure 7. Variation of dynamic earth pressure with time at depth of 70 cm and radius of 20 cm under different frequencies
图 8 不同振动频率下深度30 cm，径向20 cm处动土压力随时间的变化曲线
Figure 8. Variation of dynamic earth pressure with time at depth of 30 cm and radius of 20 cm under different vibration frequencies
图 9 不同振动频率下深度10 cm，径向35 cm处土压力随时间的变化曲线
Figure 9. Variation of dynamic earth pressure with time at depth of 10 cm and radius of 35 cm under different vibration frequencies
图 10 100 Hz频率下土压力变化率随振冲次数的变化
Figure 10. Variation of earth pressure change rate with vibration number at 100 Hz frequency
图 11 125 Hz频率下土压力变化率随振冲次数的变化
Figure 11. Variation of soil pressure change rate with vibration number at 125 Hz frequency
图 12 150 Hz频率下土压力变化率随振冲次数的变化
Figure 12. Variation of earth pressure change rate with vibration number at 150 Hz frequency
图 13 距离振冲中心20 cm处锥尖阻力随深度的变化曲线
Figure 13. Variation of cone tip resistance with depth at 20 cm from the center
图 14 距离振冲中心35 cm处锥尖阻力随深度变化曲线
Figure 14. Variation of cone tip resistance with depth at 35 cm from the center
图 15 排水量与振冲次数的关系
Figure 15. Relationship between amount of drained water and vibration number
图 16 振冲法加固堰塞体材料机理的示意
Figure 16. Schematic diagram of vibroflotation compaction mechanism of landslide dam material
表 1 不同振动频率下不同位置处最大静力触探值比较
Table 1. Comparison of maximum static cone penetration test values at different locations under different vibration frequencies
单位：MPa 频率/Hz 第1次振冲 第2次振冲 第3次振冲 第4次振冲 第5次振冲 第6次振冲 20 cm 35 cm 20 cm 35 cm 20 cm 35 cm 20 cm 35 cm 20 cm 35 cm 20 cm 35 cm 100 5.33 4.25 6.90 5.13 7.93 5.35 7.96 5.32 8.16 5.61 7.67 5.58 125 5.77 4.87 5.28 5.20 6.74 5.87 8.38 6.69 8.63 8.46 9.46 7.99 150 7.64 6.59 10.00 9.86 10.55 9.50 11.01 10.15 10.70 10.50 9.90 10.07 
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