简化增量法计算土钉轴力的模型准确性分析  

Characterization of model accuracy in prediction of soil nail loads using simplified incremental calculation method

作　　者：阙云[1] 黄瑞 林沛元 杨光华[4] QUE Yun;HUANG Rui;LIN Peiyuan;YANG Guanghua(College of Civil Engineering,Fuzhou University,Fuzhou,Fujian 350108,China;School of Civil Engineering,Sun Yat-Sen University,Guangzhou,Guangdong 510275,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai,Guangdong 519080,China;Guangdong Research Institute of Water Resources and Hydropower,Guangzhou,Guangdong 510635,China)

机构地区：[1]福州大学土木工程学院,福建福州350108 [2]中山大学土木工程学院,广东广州510275 [3]南方海洋科学与工程广东省实验室(珠海),广东珠海519080 [4]广东省水利水电科学研究院,广东广州510635

出　　处：《岩石力学与工程学报》2021年第1期158-174,共17页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(41702215,52008408);福建省自然科学基金资助项目(2018J01771)。

摘　　要：基于朗肯主动土压力原理的土钉轴力简化增量计算方法虽已广泛应用于工程实践,其模型预测精度尚缺乏系统性评估。鉴于此,本文首先从在中国建造和监测的土钉墙中收集了178根土钉共466个实测土钉轴力数据,建立数据库并进行全面分析,排查异常数据。利用剩下的143根土钉的正常数据,对上述朗肯简化增量法的模型准确性进行评估,并考察3种不同的工况对模型准确性的影响。模型的准确性由模型因子表征,其定义为土钉轴力实测值与预测值的比值。研究表明,通常情况下当前的朗肯简化增量法模型平均低估土钉最大轴力10%~17%,预测精度的离散性大,高于90%;平均高估土钉平均轴力约15%,预测精度离散性中等,约为70%。此外,朗肯增量法的模型精度与其预测值的大小呈现统计负相关性。提出基于库仑主动土压力的土钉轴力计算简化增量法,并引入一个修正系数(可取为0.75)进行计算结果校正。库仑简化增量法从统计平均意义上是无偏的,精度离散性中等,为44%~66%。研究还显示,2种轴力分配模式、土钉墙超载情况及支护类型对朗肯和库仑简化增量法的模型精度影响较小,而土体类型对模型精度有显著影响。分析证实朗肯简化增量法与库仑简化增量法的模型因子分别服从对数正态分布和韦布尔分布。最后,以土钉墙为基本单位,从另外4个角度对两类增量法的准确性评估进行了补充分析与对比。Although the Rankine-based simplified incremental calculation method(SICM) has been widely applied in practice for prediction of nail loads,its model accuracy has not yet fully assessed. In this paper,a large database containing a total of 466 measured nail loads from 178 nails reported in the literature was established. After removing questionable data,the remaining load data from 143 nails were used to evaluate the accuracy of the Rankine SICM,which is characterized by the model bias defined as the ratio of measured to predicted nail loads,and the influence of 3 working conditions on the accuracy of the SICM was also investigated. The results show that,under typical cases,the current Rankine SICM underestimates averagely the maximum nail load by about 10% to 17% with a high prediction dispersion over 90% while overestimates the mean nail load by about 15% with a moderate prediction dispersion of about 70%. In addition,the accuracy is statistically correlated to the magnitude of the predicted value,which is undesirable. It was proposed to estimate the nail load based on the Coulomb active earth pressure theory instead of the Rankine theory for accuracy improvement. A calibration constant of about 0.75 is introduced to calibrate the computed nail load. The Coulomb SICM was demonstrated to be unbiased on average with a medium prediction dispersion from 44% to 66%. It is also shown that the accuracies of both Rankine and Coulomb SICMs are significantly influenced by soil types whereas the influence of load allocation schemes,external loading conditions and wall types is marginal. The model biases of Rankine and Coulomb SICMs respectively follow lognormal and Weibull distributions. Finally,the accuracies of the two types of SICM were discussed complementally from another four angles.

关 键 词：土力学 土钉墙 土钉轴力 简化增量法 模型不确定性 可靠度设计 

分 类 号：TU43[建筑科学—岩土工程]