高速液压夯加固台背碎石土现场试验研究

Experimental Study on Abutment Back Gravel Soil Reinforced with Rapid Hydraulic Impact Compaction

为探究高速液压夯加固碎石土的动力特性及影响规律,依托潍坊至青岛高速公路某台背回填工程,开展了高速液压夯加固箱涵背侧回填碎石土的现场试验研究。试验采用预埋土压力计、应变片等监测元件的方式,监测夯击过程中碎石土及涵背的应力、应变发展规律。以动应力、残余应力、夯沉量、标准贯入击数及涵背应变作为评价指标,探究了高速液压夯的动应力传播规律,分析了夯击次数、夯击能、夯间距等因素对碎石土加固效果以及施工振动对桥涵台背的影响。结果表明:高速液压夯所产生的动应力主要沿竖向传递,有效加固深度可达2 m,在水平向0.5 m范围内衰减速度快;由于夯击对周围土体的加固作用,对临近夯点夯击时,其动应力明显增加;增加夯击能可有效提高加固效果,使用高档位夯击时加固效果更为显著;加固效果随夯击次数的增加而增强,但每一击所产生的密实效果逐渐降低,对碎石土路基,夯击次数以小于9次为宜;适当减小夯间距可提高加固效果,适宜夯间距为1.5倍夯锤直径;夯击产生的涵背结构物应变远小于规范值,对箱涵等构筑物的安全影响很小。研究成果可为类似桥涵台背路基填土夯实工程的设计及施工提供借鉴和参考。

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.