CPTU数据校准上海深层软土参数的随机力学-贝叶斯方法  

Stochastic mechanics-based Bayesian method for calibrating geotechnical parameters of Shanghai deep soft clay using CPTU data

作　　者：王长虹 吴昭欣 王昆[1] 汤道飞 马铖涛 WANG Changhong;WU Zhaoxin;WANG Kun;TANG Daofei;MA Chengtao(Department of Civil Engineering,School of Mechanics and Engineering Sciences,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学力学与工程科学学院土木工程系,上海200444

出　　处：《岩土工程学报》2023年第1期75-84,I0006,共11页Chinese Journal of Geotechnical Engineering

基　　金：上海高校特聘教授岗位计划项目(TP2018042);上海市浦江人才计划项目(18PJ1403900);上海市社会发展科技攻关项目(21DZ1204300)。

摘　　要：城市深层地下空间的开发需要开展科学计算。合理的本构模型和准确的岩土参数是岩土力学分析的两大支撑。修正剑桥模型(modified cam-clay,MCC)的岩土参数简单直观,被广泛应用于岩土工程实践。室内土工试验由于取样扰动、试验误差等不可避免的缺陷,难以精确获得深层岩土参数。结合先验知识、室内试验数据和孔压静力触探(piezocone penetration test,CPTU)测试数据,将关键岩土参数视为随机变量,采用随机力学-贝叶斯方法,校准深层软土的关键岩土参数,如临界状态应力比、压缩系数、回弹系数和超固结比。以上海市苏州河深层排水调蓄管道系统工程——云岭竖井基坑工程为背景,以基础底板处的深部第(8)层土为研究对象。首先,利用MCC模型的柱孔扩张理论,揭示了CPTU数据(锥尖阻力、侧摩阻力和孔隙水压力)与极限扩孔应力之间的力学转换机理,利用苏格兰Bothkennar岩土试验场地的试验数据,验证CPTU测试数据力学模型的适用性;其次,建立关键岩土参数与CPTU数据之间的二次非交叉响应面,利用MCMC(Markov-chain Monte Carlo)抽样算法,获得关键岩土参数的后验统计特征;最后,结合岩土参数的后验均值,开展超深基坑工程的数值计算。结果表明,经过柱孔扩张随机力学-贝叶斯方法校准后,关键岩土参数的不确定性大幅度降低,后验均值的预测结果与监测值较为接近,证明了该方法的高效、合理性。The construction of urban deep underground engineering requires scientific calculation.The reasonable constitutive model and accurate geotechnical parameters are the most important support for soil mechanics.The modified Cam-clay(MCC)model is a simple one as its constants are simple and intuitive,and is widely used in geotechnical engineering.However,it’s different to get precise parameters in deep soft clay by the indoor tests due to sampling disturbance,test error and other unavoidable factors.Considering the prior information,laboratory test data,and piezocone penetration test(CPTU) data,the key geotechnical parameters are treated as random variables,the stochastic mechanics-Bayesian method is proposed to calibrate the key geotechnical parameters of the deep soil layers,such as the critical state stress ratio,compression coefficient,rebound coefficient,and overconsolidation ratio.Based on the Suzhou River deep drainage and storage pipeline system in Shanghai and the foundation pit of Yunling,the deep soil layer(8) at the base plate is taken as the research object.Firstly,the mechanical conversion between the CPTU data(i.e.,cone tip resistance,lateral friction stress and pore pressure) and the limit expansion pressure of cylindrical cavity is derived in the MCC model.The mechanical conversion for the CPTU data is verified by using the test data from Bothkennar geotechnical test site in Scotland.Secondly,the quadratic response surface without being crossed between the key geotechnical parameters and the CPTU data can be established by regression.The Markov-chain Monte Carlo(MCMC) sampling method will obtain the posterior distributions of the key geotechnical parameters.Finally,The numercial calculation for the foundation pit is carried out with the mean values of the posterior geotechnical parameters.The results show that the uncertainties of the geotechnical parameters are significantly reduced,and the results obtained by the numerical simulation of the foundation pit using the mean values of geotechnical par

关 键 词：孔压静力触探 柱孔扩张理论 随机力学 岩土参数 超深基坑 

分 类 号：TU413[建筑科学—岩土工程]