Experimental Study on Abutment Back Gravel Soil Reinforced with Rapid Hydraulic Impact Compaction
To explore the dynamic characteristics and influencing rule of gravel soil reinforced with rapid hydraulic impact compaction,the field test of box culvert abutment backfill gravel soil reinforced with rapid hydraulic impact compaction was carried out based on the abutment backfill project on Weifang-Qingdao expressway.The test used embedded soil pressure gauges,strain gauges and other monitoring elements to monitor the stress and strain development rule of gravel soil and culvert back during the tamping process.Taking dynamic stress,residual stress,tamping settlement,standard penetration number and culvert back strain as evaluation indicators,the dynamic stress propagation rule of rapid hydraulic impact compaction was explored.The influence of tamping times,tamping energy,tamping spacing and other factors on the reinforcement effect of gravel soil was analyzed;meanwhile the influence of construction vibration on the bridge culvert abutment back was analyzed.The result indicates that the dynamic stress generated by rapid hydraulic impact compaction is mainly transmitted along the vertical direction.The effective reinforcement depth can reach 2 m,and the attenuation speed is fast in the horizontal range of 0.5 m.Due to the reinforcement effect of tamping on surrounding soil,the dynamic stress increases obviously when the tamping point is close to the tamping point.Increasing tamping can effectively improve the reinforcement effect,and the reinforcement effect is more significant when using high-grade tamping.The reinforcement effect increases with the increase of number of tamping times,but the compaction effect produced by each blow gradually decreases.For the gravel soil subgrade,the number of tamping times should be less than 9.Appropriately reducing the tamping spacing can improve the reinforcement effect,and the appropriate tamping spacing is 1.5 times of the hammer diameter.The strain of culvert back structure caused by tamping,which has little effect on the safety of box culvert and other structures,is far less than the standard value.The study result can provide the design and construction references for similar bridge culvert abutment back subgrade filling compaction projects.
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