首页|定向剪切应力路径下类弱胶结软岩椭圆各向异性强度准则

定向剪切应力路径下类弱胶结软岩椭圆各向异性强度准则

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地下工程开挖卸荷引起的围岩应力重分布将影响弱胶结软岩强度,导致巷道围岩产生不均匀大变形,甚至造成塌方、冒顶等安全事故.以膨润土、风积砂、石膏粉和滑石粉为原料制备类弱胶结软岩试样,利用GDS SSHCA空心圆柱扭剪仪开展主应力定向剪切试验,研究大主应力方向对弱胶结软岩应力-应变曲线、峰值应力(变)和抗剪强度的影响规律,探索主应力方向诱导的弱胶结软岩强度各向异性特征.结果表明:当0°＜α＜45°时(α为大主应力与竖直方向的夹角),试样产生轴向压应变和剪应变,且随着α的增加,试样轴向应变占比逐渐减小,剪应变占比逐渐增加;当α=45°时,试样以剪应变为主,并伴随体积扩容现象;当45°＜α＜90°时,试样受侧向挤压产生轴向拉应变与剪应变.当0°≤α≤30°时,峰值剪应力比(Tzθ/p')max随α的增加逐渐增大;而当30°＜α ≤90°时,(τzθ/p')max则随着α的增加逐渐减小;当α=30°时,(τzθ/p')max=0.81,为最大值,这表明软岩具有显著的各向异性特征.基于峰值剪应力比演化特征,假设(τzθ/p')max包络线为椭圆形,建立一个可描述弱胶结软岩各向异性的椭圆强度准则.利用三轴试验和纯剪试验确定模型参数并依据定向剪切试验结果验证模型的可靠性.研究成果可为地下工程围岩变形控制与灾害防治提供理论支撑.
Elliptical anisotropic strength criterion of similar weakly cemented soft rock under directional shear stress path
The surrounding rock stress will redistribution during the underground engineering excavation process.This will affect the strength of weakly cemented soft rock,leading to uneven and large deformation of the surrounding rock of the tunnel,and even causing safety hazards such as collapse and roof fall.In this study,similar weakly cemented soft rock samples were synthesized using a mixture of bentonite,aeolian sand,gypsum,and talcum powders.Then,the directional shear tests with different direction angle of major principal stress were conducted by using GDS SSHCA hollow cylinder torsional shear apparatus.The stress vs.strain curves,peak stress variations,and shear strength are investigated and explored the strength anisotropic characteristics of similar weak cemented soft rock induced by the direction of major principal stress.The results show that both axial compressive strain and shear strain simultaneously generated when 0°＜α＜45°(α is the angle between the major principal stress and the vertical direction).And the axial strain gradually decreases,while the shear strain gradually increases with the increases of α;If α=45 °,shear strain predominated and accompanied with volume expansion phenomenon.The samples were subjected to tensile stress and torsional shear stress,which lead to the axial tension and shear strains when 45 °＜α＜90 °.The peak shear stress ratio(τzθ/p')max increased with α=30°,after which it decreased until α=90°.The peak shear stress ratio is 0.81,which highlights the rock's pronounced anisotropic behavior.Utilizing the above findings and assumed the envelope of(rzθ/p')max in the deviatoric plane follows elliptical shape.Then,the elliptical anisotropic strength criterion of weakly cemented soft rock under directional shear stress path was established to describe the anisotropic strength characteristic of weakly cemented soft rock.The ellipse major and minor axis parameters can be obtained by using triaxial and pure shear tests.The validity of this model is confirmed by the results of directed shear tests.This research provides a theoretical basis for controlling deformations and preventing disasters in the field of underground engineering.

rock mechanicssimilar weakly cemented soft rockanisotropyelliptical strength criteriondirectional shearpeak shear stress ratio

刘家顺、郑智勇、左建平、王洋、生彦涛、周妮

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辽宁工程技术大学土木工程学院,辽宁阜新 123000

中国矿业大学(北京)力学与建筑工程学院,北京 100083

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

岩石力学 类弱胶结软岩 各向异性 椭圆强度准则 定向剪切 峰值剪应力比

国家自然科学基金国家自然科学基金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开放基金

5210408852374091SKLGME022021

2024

10.13722/j.cnki.jrme.2023.0871

岩石力学与工程学报
中国岩石力学与工程学会

岩石力学与工程学报

CSTPCD北大核心
影响因子：2.589
ISSN：1000-6915
年,卷(期)：2024.43(5)
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