考虑应变软化和冻融循环影响的粉质黏土修正双曲线模型

熊华涛

doi:10.13204/j.gyjzG21050610

考虑应变软化和冻融循环影响的粉质黏土修正双曲线模型

doi: 10.13204/j.gyjzG21050610

熊华涛

中铁十六局集团铁运工程有限公司, 河北高碑店 074000

详细信息

作者简介:
熊华涛,男,1978年出生,高级工程师。电子信箱:124967643@qq.com

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- 被引次数: 0
出版历程
- 收稿日期: 2021-05-06
- 网络出版日期: 2022-07-25

An Improved Hyperbolic Model for Silty Clay Considering Strain Softening of Soil and Freeze-Thaw Cycle Effects

XIONG Huatao

Railway Transportation Engineering Co., Ltd., China Railway the 16th Bureau Group, Gaobeidian 074000, China

摘要

摘要: 为反映超固结土应力-应变关系在冻融循环下的变化规律,提出一种可以同时考虑应变软化和冻融循环影响的修正双曲线模型。首先,基于Kondner双曲线模型和割线模量定义,通过变换双曲线模型函数得到无量纲化割线模量E_s/E_i与无量纲化偏应力q/q_max关系的基本形式。根据压实粉质黏土的三轴试验结果,将应变软化前、后的E_s/E_i-q/q_max关系分别用幂函数描述,建立了可反映应变软化的修正双曲线模型,包含c、φ、K、n、f、g、α、β等8个参数。然后,通过确定模型参数随冻融循环次数的变化规律来反映冻融循环对土的影响。结果表明:随着冻融循环次数的增加,峰值强度和黏聚力c逐渐减小,内摩擦角φ逐渐增大;初始割线模量E_i逐渐减小,相应地K逐渐减小,n值逐渐增大;f和α反映应变软化时分段函数中割线模量的界限值,分别逐渐增大和减小;g和β反映应变软化前、后的E_s/E_i-q/q_max曲线形状,g逐渐减小,而β呈波动特征,同时上述参数与冻融循环次数的回归关系均可以采用Logistic函数拟合。在此基础上,根据修正双曲线模型和模型参数的函数表达式,编制以围压和冻融循环次数为影响因子的计算程序,模型结果可以反映围压与冻融循环对土体力学性质的影响规律。
- 应变软化 /
- 冻融循环 /
- 粉质黏土 /
- 割线模量 /
- 双曲线模型 /
- 分段函数
Abstract: In order to describe the stress-strain characteristics of strain-softening soil subjected to freeze-thaw cycling, an improved hyperbolic model was proposed. Based on the traditional Kondner hyperbolic model and the definition of secant modulus, the basic relation between dimensionless secant modulus E_s/E_i and dimensionless deviation stress q/q_max was deduced through transformation of the hyperbolic model function. A set of triaxial tests were conducted on compacted silty clay specimens subjected to different confining pressures and freeze-thaw cycles. The q/q_max-E_s/E_i relations before and after strain softening could be fitted by the power function, respectively. An improved hyperbolic model, which contained 8 parameters including c, φ, K, n, f, g, α and β, was proposed to reflect the strain softening characteristics. The influence of freeze-thaw cycles on soil characteristics was formulated by determining the laws of the model parameters changed with freeze-thaw cycles. The results showed with the increase of freeze-thaw cycles, the peak strength of specimens and cohesion c decreased gradually, the internal friction angle φ increased ceaselessly; the initial secant modulus decreased increasely, and the corresponding parameter K decreased at the same time, the parameter n increased steadily. The parameters f and α were the limit values which reflected secant moduli of picewise functions in the period of strain-softening, they increased or decreased gradually respectively with increase of freeze-thaw cycles.The parameters g and β reflected the shape of E_s/E_i-q/q curves before and after strain-softening, and g decreased steadily with the increasing of freeze-thaw cycles and β changed in fluctuation. The relations of the above parameters to freeze-thaw cycles could be fitted by the Logistic function. The improved model and representation expressions for model parameters were programmed into a calculation software, which taking the confining pressure and freeze-thaw cycles as the variables. The calculation results by the model could reflect the influence of confining pressure and freeze-thaw cycles on the mechanical properties of soil.
- strain softening /
- freeze-thaw cycle /
- silty clay /
- secant modulus /
- hyperbolic model /
- piecewise function

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