摘要
为了研究某工程振冲碎石桩砂质粉土复合地基剪切变形机制和强度特性,采用大型叠环剪切仪开展了两组不同桩体置换率下的碎石桩复合地基模型试验。对剪应力与剪应变、不同应力状态下复合地基变形及开挖断面进行了系统分析,研究结果表明:砂质粉土复合地基呈弹塑性体的特征,应力水平线S=0.5可大致作为弹塑性体的分界线;在复合地基大变形剪切过程中,桩土具有很好的变形协调性,且随着桩体置换率的提升复合地基剪切变形是被抑制的;目前少数明确提出复合地基抗剪强度计算公式的国家规范都建议桩土应力比n取1,即仅考虑面积置换率因素,这导致不同置换率下复合地基的抗剪强度计算结果相差较小,按规范22.7%置换率相较40.3%置换率φ值仅小1.32°,而试验结果22.7%置换率相较40.3%置换率φ值小3.65°,这表明碎石桩对复合地基抗剪能力的加固机制不仅限于置换率因素,也应考虑其对复合地基整体排水效果的改变等因素。
To study the shear deformation mechanism and strength characteristics of vibroflotation crushed stone column composite foundation in sandy silty soil,two model tests of crushed stone pile composite foundation with different displacement rates of pile were carried out by using large stacking ring shear apparatus.The relationship between shear stress and shear displacement,deformation of composite foundation under different stress states are systematic analyzed.The test results show that:1)The sandy silty composite foundation has a feature of elastoplastic object and the stress level S=0.5 can be used as the elastoplastic object’s dividing line roughly.2)In the process of large deformation destruction of composite foundation,the stone columns and soil have a good deformation consistency,meanwhile,the shear deformation is inhibited with the increase of displacement rate of pile.3)At present,a few specifications in China suggest that the number of stress ratio of pile with soil is 1 for the shear strength calculation of composite foundation,which means that only pile area replacement is considered.As a result,the calculation results of shear strength are close under different pile replacement rates.The permutation rate of 22.7%has a 1.320 gap compare with 40.3%while the pile replacement rate of 22.7%has a 3.650 gap compare with 40.3%in the model test.It indicates that the reinforcement mechanism of stone columns on composite foundation should not be limited to the factor of displacement rate,the change of drainage effectiveness of composite foundation factor should also be considered.
作者
王家辉
饶锡保
江洎洧
姚劲松
熊诗湖
卢一为
李浩民
WANG Jia-hui;RAO Xi-bao;JIANG Ji-wei;YAO Jin-song;XIONG Shi-hu;LU Yi-wei;LI Hao-min(Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources,Yangtze River Scientific Research Institute,Wuhan,Hubei 430010,China;Changjiang Institute of Survey Planning Design and Research,Wuhan,Hubei 430010,China)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2021年第4期1095-1103,共9页
Rock and Soil Mechanics
基金
国家重点研发计划(No.2017YFC0405001)
国家自然科学基金(No.51979009,No.52008032)
中央级科研院所基本科研业务费项目(No.CKSF2019191/YT)。
关键词
碎石桩
复合地基
剪切破坏
抗剪强度
stone column
composite foundation
shear failure
shear strength
