湛江结构性黏土自钻旁压试验的加载速率效应

doi:10.16285/j.rsm.2020.1502

岩土力学 ›› 2021, Vol. 42 ›› Issue (6): 1557-1567.doi: 10.16285/j.rsm.2020.1502

湛江结构性黏土自钻旁压试验的加载速率效应

舒荣军^{1, 2}，孔令伟^{1, 2}，师文卓^{1, 2}，刘炳恒^{1, 2}，黎澄生^{1, 2}

1. 中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室，湖北武汉 430071；2. 中国科学院大学，北京 100049

收稿日期:2020-10-08 修回日期:2021-03-01 出版日期:2021-06-11 发布日期:2021-06-15
通讯作者: 孔令伟，男，1967年生，博士，研究员，博士生导师，主要从事特殊土的力学特性与灾害防治技术方面的研究。E-mail: lwkong@whrsm.ac.cn E-mail:shurongjun16@mails.ucas.ac.cn
作者简介:舒荣军，男，1995年生，博士研究生，主要从事特殊土的力学特性方面的研究
基金资助:
国家自然科学基金（No.41877281）

Effects of loading rate on SBPT responses of Zhanjiang structured clay

SHU Rong-jun^{1, 2}, KONG Ling-wei^{1, 2}, SHI Wen-zhuo^{1, 2}, LIU Bing-heng^{1, 2}, LI Cheng-sheng^{1, 2}

1. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China

Received:2020-10-08 Revised:2021-03-01 Online:2021-06-11 Published:2021-06-15
Supported by:
This work was supported by the National Natural Science Foundation of China(41877281).

摘要/Abstract

摘要： 作为一种具有高结构屈服强度的灵敏性黏土，湛江黏土力学性质的加载速率效应值得关注。为了研究湛江黏土原位力学性质的加载速率效应，开展了不同加载速率的自钻旁压试验，分析应力速率对湛江黏土原位不排水抗剪强度、线性刚度以及剪切模量非线性衰减特性的影响。结果表明：应力速率越大，不排水抗剪强度就越大，二者之间具有良好的线性关系，这一变化关系不同于文献中控制应变速率的研究结果；线性割线剪切模量G_ur随应力速率的增大而增大，经相应速率下G_ur归一化后的不排水抗剪强度落于较窄的数值区间内，表明应力速率对峰值强度对应的应变影响很小；加载速率越大，切线剪切模量G_t衰减幅度越大、衰减越迅速、G_t-γ衰减曲线越陡，但对于各应力速率，G_t均约在γ = 0.1%时衰减至小于G_ur；加载速率影响了各应变区间内G_t的衰减幅度和速度，加载速率越小，衰减集中发生于越低的应变水平。研究指出湛江黏土特殊的微观结构是控制其力学性质加载速率效应的主导因素，并通过开展原状土样和重塑土样的室内超微型贯入试验予以初步印证。认为应当重视土体原位力学性质的加载速率效应，同时关注加载速率历史对土体蠕变性质的影响。

关键词: 结构性黏土, 自钻旁压试验, 超微型贯入试验, 速率效应, 剪切模量, G-??衰减曲线

Abstract:

The study on influence of loading rate on mechanical behavior of Zhanjiang clay, which is a kind of sensitive clay with high yield strength, could be noteworthy. In order to study the loading rate effects on intact mechanical properties of Zhanjiang clay, the self-boring pressuremeter tests (SBPT) under five different loading rates have been carried out. The influence of stress rate on undrained shear strength, linear stiffness and non-linear degradation of shear modulus of the soil have been discussed. It is shown that the greater stress rate results in higher undrained shear strength, proposing strong linear correlation between two variables, and that behaves differently from the results of tests controlling strain rate given in literature. The linear secant shear modulus G_ur increases with stress rate and the undrained shear strengths varies within a class with small width after normalized by corresponding G_ur, which indicates little effect caused by loading rate on the strain corresponding to the peak strength. The significant degradation of tangential shear modulus G_t, at higher gradient and the steeper G_t-γ decay curve have been observed when at higher stress rate. The value of shear strain where G_t decreases to less than G_ur is about 0.1% for all stress rate conditions. The loading rate significantly affects the amplitude and the gradient of the decay of G_tin the corresponding class. The smaller the stress rate leads to the lower strain level where the decay of G_t mainly occurs. It is recognized that the special microstructure could account for the loading rate effects of Zhanjiang clay and this comment is preliminarily proved by super-mini-penetration tests conducted on both undisturbed and remolded samples. It is recommended that special attention should be paid to both the loading rate effects on in-situ mechanical properties and the influence of “loading rate history” on creep behavior of soils.

Key words: structured clay, self-boring pressuremeter test, super mini-penetration test, rate effects, shear modulus, G-? decay curves

中图分类号:

TU413

舒荣军, 孔令伟, 师文卓, 刘炳恒, 黎澄生, . 湛江结构性黏土自钻旁压试验的加载速率效应[J]. 岩土力学, 2021, 42(6): 1557-1567.

SHU Rong-jun, KONG Ling-wei, SHI Wen-zhuo, LIU Bing-heng, LI Cheng-sheng, . Effects of loading rate on SBPT responses of Zhanjiang structured clay[J]. Rock and Soil Mechanics, 2021, 42(6): 1557-1567.

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湛江结构性黏土自钻旁压试验的加载速率效应

Effects of loading rate on SBPT responses of Zhanjiang structured clay

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