台州滨海软黏土强度特性室内外联合标定

Joint laboratory and in-situ calibration of strength characteristics for Taizhou coastal soft clay

我国滨海地区广泛分布有低强度、高压缩性软黏土,其工程特性评价对工程建设影响极大。孔压静力触探(CPTU)对土体扰动小,是目前最常用的原位测试方法之一。但是CPTU测试成果需要通过解译才可实现对土体力学特性的评价,不同地区存在地区特异性。针对台州滨海地区深厚软黏土场地,开展了孔压静力触探试验和室内试验,系统地研究了台州滨海软黏土的强度特征。基于重塑台州软黏土固结快剪试验,得到了台州软黏土的归一化强度与超固结比(OCR)的关系式,其应力历史及归一化土工程特性(SHANSEP)法经验系数a为0.226,经验系数b为0.761;标定得到了台州软黏土的CPTU触探因子Nkt的范围为10.23~16.88,总平均值为14.08;基于SHANSEP公式和Nkt法解译得到的土体不排水抗剪强度su,获取了台州软黏土的原位超固结比OCR连续剖面;并标定得到了不同地层的OCR解译经验系数k的范围为0.315~0.570,建议采用k=0.33对台州软黏土超固结比OCR进行解译。

The soft clay with low strength and high compressibility is widely distributed in the coastal area of China.The engineering characteristics evaluation of soft clay is crucial for engineering construction.Piezocone penetration test(CPTU)is one of the most commonly used in-situ testing methods,which has slight disturbance on soil.However,the mechanical properties of the soil requires interpretation of CPTU test results,which is site-specific.This paper presents a study conducted in the Taizhou coastal area to investigate the strength characteristics of deep soft clay through CPTU and laboratory tests.Based on the direct shear test(consolidated quick shear)results of reconsolidated Taizhou soft clay,the relationship between the normalized strength and overconsolidation ratio(OCR)of Taizhou soft clay was obtained,where the empirical coefficients a and b of the stress history and normalized soil engineering properties(SHANSEP)method were determined to be 0.226 and 0.761,respectively.The cone factor Nkt of Taizhou soft clay were calibrated from 10.23 to 16.88,with a total mean value of 14.08.Utilizing the SHANSEP formula and the undrained shear strength su obtained by Nkt method,a continuous section of the in-situ OCR of Taizhou soft clay was derived.The interpretation empirical coefficient k of different strata OCR were calibrated from 0.315 to 0.570,a value of k=0.33 was recommended for interpreting the OCR of Taizhou soft clay.