{"title":"Small strain shear modulus of saturated and unsaturated cohesive soils under anisotropic consolidation","authors":"Ngoc Bao Le , Hirofumi Toyota , Susumu Takada","doi":"10.1016/j.sandf.2024.101464","DOIUrl":null,"url":null,"abstract":"<div><p>Cohesive soils in nature are created under anisotropic stress and have various stress histories. Embankments generate greater vertical loads underground. Moreover, associated excavation activities can exacerbate the extensional stress state. This study investigated the effects of induced anisotropy on the shear modulus in saturated and unsaturated cohesive soils. A triaxial testing apparatus, equipped with local small strain (LSS) measurement devices and bender elements (BEs), was used to measure the small strain shear modulus. Two series of tests were conducted: (1) LSS and BE tests used specimens normally consolidated under a constant mean effective stress of <em>p’</em> = 300 kPa or net mean stress <em>p</em><sub>net</sub> = 300 kPa with different stress ratios to investigate the effects of anisotropic consolidation. The values of the applied stress ratios, represented as <em>K</em> = σ<em>'</em><sub>h</sub>/ σ<em>'</em><sub>v</sub> for the saturated soil and <em>K</em><sub>net</sub> = (σ<sub>h</sub>–<em>u</em><sub>a</sub>)/(σ<sub>v</sub>–<em>u</em><sub>a</sub>) for the unsaturated soil, were 0.35, 0.43, 0.6, 0.8, 1.0, 1.5, 2.0, 3.0, and 3.5. (2) BE tests used specimens consolidated under various mean effective stresses in the order of <em>p’</em> = 50, 100, 200, 300, 400, 500, and 600 kPa, and swollen in reverse order under <em>K</em> of 0.35, 0.43, 0.6, and 1.0, to elucidate <em>p’</em> and the effects of the overconsolidation ratio (OCR). The results demonstrated that <em>K</em>-consolidation under constant <em>p’</em> produces large differences in initial shear modulus <em>G</em><sub>0</sub> in saturated cohesive soil, but <em>K</em><sub>net</sub> produces only slight differences in unsaturated cohesive soil because of the influence of strong matric suction. Finally, <em>G</em><sub>0</sub> was normalized successfully considering the effects of void ratio <em>e</em>, <em>K</em>, and OCR.</p></div>","PeriodicalId":21857,"journal":{"name":"Soils and Foundations","volume":"64 3","pages":"Article 101464"},"PeriodicalIF":3.3000,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0038080624000428/pdfft?md5=31e40f412757805bbb553170f8c4639f&pid=1-s2.0-S0038080624000428-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Soils and Foundations","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0038080624000428","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, GEOLOGICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Cohesive soils in nature are created under anisotropic stress and have various stress histories. Embankments generate greater vertical loads underground. Moreover, associated excavation activities can exacerbate the extensional stress state. This study investigated the effects of induced anisotropy on the shear modulus in saturated and unsaturated cohesive soils. A triaxial testing apparatus, equipped with local small strain (LSS) measurement devices and bender elements (BEs), was used to measure the small strain shear modulus. Two series of tests were conducted: (1) LSS and BE tests used specimens normally consolidated under a constant mean effective stress of p’ = 300 kPa or net mean stress pnet = 300 kPa with different stress ratios to investigate the effects of anisotropic consolidation. The values of the applied stress ratios, represented as K = σ'h/ σ'v for the saturated soil and Knet = (σh–ua)/(σv–ua) for the unsaturated soil, were 0.35, 0.43, 0.6, 0.8, 1.0, 1.5, 2.0, 3.0, and 3.5. (2) BE tests used specimens consolidated under various mean effective stresses in the order of p’ = 50, 100, 200, 300, 400, 500, and 600 kPa, and swollen in reverse order under K of 0.35, 0.43, 0.6, and 1.0, to elucidate p’ and the effects of the overconsolidation ratio (OCR). The results demonstrated that K-consolidation under constant p’ produces large differences in initial shear modulus G0 in saturated cohesive soil, but Knet produces only slight differences in unsaturated cohesive soil because of the influence of strong matric suction. Finally, G0 was normalized successfully considering the effects of void ratio e, K, and OCR.
期刊介绍:
Soils and Foundations is one of the leading journals in the field of soil mechanics and geotechnical engineering. It is the official journal of the Japanese Geotechnical Society (JGS)., The journal publishes a variety of original research paper, technical reports, technical notes, as well as the state-of-the-art reports upon invitation by the Editor, in the fields of soil and rock mechanics, geotechnical engineering, and environmental geotechnics. Since the publication of Volume 1, No.1 issue in June 1960, Soils and Foundations will celebrate the 60th anniversary in the year of 2020.
Soils and Foundations welcomes theoretical as well as practical work associated with the aforementioned field(s). Case studies that describe the original and interdisciplinary work applicable to geotechnical engineering are particularly encouraged. Discussions to each of the published articles are also welcomed in order to provide an avenue in which opinions of peers may be fed back or exchanged. In providing latest expertise on a specific topic, one issue out of six per year on average was allocated to include selected papers from the International Symposia which were held in Japan as well as overseas.