红层地区基坑锚杆抗拔承载力及计算参数时变特性  

Time-varying characteristics of pullout bearing capacity and calculation parameters of excavation anchors in the red bed area

作　　者：刘晓明[1] 刘舒 杨康 LIU Xiaoming;LIU Shu;YANG Kang(College of Civil Engineering,Hunan University,Changsha 410082,China)

机构地区：[1]湖南大学土木工程学院,长沙410082

出　　处：《中国科技论文》2023年第4期366-371,共6页China Sciencepaper

基　　金：国家自然科学基金资助项目(51578230)。

摘　　要：针对锚杆在服役过程中承载力可能下降的问题,对红层地区某基坑工程开展多批次锚杆拉拔试验,得到了红层软岩锚杆的荷载-位移曲线(P-S曲线),揭示了红层软岩基坑锚杆抗拔承载力随时间衰减的特征。首先基于锚固体-岩土界面的三折线本构模型,推导出锚杆端部(锚头)的荷载-位移关系式;然后基于现场试验数据,采用鲸鱼优化算法进行计算参数反演,得到关系式的计算参数值及其随时间的变化特性。结果表明:红层软岩基坑锚杆抗拔承载力随时间衰减,且承载力衰减幅度随着时间的增长并不收敛,荷载-位移关系式的计算参数也随时间变化:服役3年后,锚固界面极限强度降低了46.8%,侧摩阻力传递系数降低了60.6%,极限荷载下锚固体的脱黏段长度降低了16.7%,而极限剪切位移增加了36.9%;与服役近1年相比,锚杆抗拔承载力与计算参数随时间的变化没有稳定趋势,因此对基坑支护结构延长使用年限应谨慎对待。The pullout bearing capacity of the anchors may decrease during the service process.A series of anchors pullout tests were carried out for a certain excavation project in the red bed area to obtain the load-displacement curve(P-S curve) of the red bed soft rock anchors.These data reveal that the pullout bearing capacity of excavation anchors in the red bed soft rock decays with time.First,based on the three-fold line constitutive model of the solid-rock interface,the load-displacement relationship of the head of the anchors was derived.Then,the whale optimization algorithm was used to inverse the calculation parameters through the field test data.Thus,the values of the calculation parameters of the formula and the time-varying characteristics of these parameters were obtained.The results show that the pullout bearing capacity of anchors rods in red bed soft rock excavation decays with time,and the attenuation amplitude of bearing capacity does not converge with time.The calculation parameters of the load-displacement formula also change with time.After 3 years of service,the ultimate strength of anchoring interface has been reduced by 46.8%.The transfer coefficient of lateral friction resistance has been reduced by 60.6%.The length of the debonded section of the anchors under ultimate load has been reduced by 16.7%,while the ultimate shear displacement increased by 36.9%.Compared with the results of anchors used near one year,the pullout bearing capacity of anchors and the calculation parameters have no stable trend over time.Therefore,the extension of the service life of the excavation supporting structure should be treated with caution.

关 键 词：红层软岩 基坑锚杆 抗拔承载力 参数反演 时变特性 

分 类 号：TU470.3[建筑科学—结构工程]