Effect of crack angles on energy characteristics of sandstones under a complex stress path

2019 ◽  
Vol 218 ◽  
pp. 106577 ◽  
Author(s):  
Kang Peng ◽  
Yunqiang Wang ◽  
Quanle Zou ◽  
Zhaopeng Liu ◽  
Junhui Mou
Keyword(s):  
Stress Path ◽  
Complex Stress ◽  
Energy Characteristics ◽  
Complex Stress Path

Modified state-surface approach to the study of unsaturated soil behavior. Part I: Basic concept

2009 ◽  
Vol 46 (5) ◽  
pp. 536-552 ◽  
Author(s):  
Xiong Zhang ◽  
Robert L. Lytton
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Stress Path ◽  
Complex Stress ◽  
Soil Behavior ◽  
Elastic Surface ◽  
Surface Approach ◽  
Basic Model ◽  
Plastic Hardening ◽  
Complex Stress Path

The traditional state-surface approach to the study of unsaturated soil behavior is becoming much less popular these days, as it uses unique constitutive surfaces to represent unsaturated soil behavior. This approach is essentially a nonlinear elastic formation and cannot be used to explain complex stress-path dependency for unsaturated soils. In this paper, a modified state-surface approach (MSSA) is proposed to represent unsaturated soil behavior under isotropic stress conditions in which a conventional void-ratio state surface is considered to be made up of an elastic surface and a plastic hardening surface. The plastic hardening surface remains stationary at all times, whereas the elastic surface remains unchanged when the soil experiences elastic deformation and moves downward when there is plastic hardening occurrence. Using the MSSA, the loading–collapse (LC) and the suction increase (SI) yield curves in the Barcelona basic model (BBM) are derived. The prediction of three typical cases of soils under isotropic conditions and experimental results using the proposed approach confirmed its feasibility, simplicity, and potential for the study of unsaturated soil behavior.

The Studies of Rock Damage Softening Statistical Constitutive Model under True Triaxial Stress State

2014 ◽  
Vol 580-583 ◽  
pp. 312-315
Author(s):  
Hui Mei Zhang ◽  
Xiang Miao Xie ◽  
Geng She Yang
Keyword(s):  
Constitutive Model ◽  
Strain Curve ◽  
Stress Path ◽  
Complex Stress ◽  
Model Parameters ◽  
Stress Strain ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Complex Stress Path ◽  
The Impact

From the feature of rock micro-unit failure obeys Poisson random distribution, the damage softening statistical constitutive of was established under true triaxial confinement based on D-P criterion, so the impact of the intermediate principal stress on rock deformation and failure was considered in theory, and the actual engineering rock complex stress path evolution was reflected more realistically. Furthermore, according to the geometrical conditions of stress-strain relationship, the theoretical relationship between constitutive model parameters and the stress-strain curve characteristic parameters during the process of rock softening and deforming, which enhance the adaptability of the model. Finally, the rationality of the model verified by the measured data.

Rockfill Particle Breakage Generated by Wetting Deformation under the Complex Stress Path

2020 ◽  
Vol 20 (10) ◽  
pp. 04020166
Author(s):  
Yufeng Jia ◽  
Bin Xu ◽  
Chandrakant S. Desai ◽  
Shichun Chi ◽  
Biao Xiang
Keyword(s):  
Stress Path ◽  
Complex Stress ◽  
Particle Breakage ◽  
Complex Stress Path ◽  
Wetting Deformation

Small-strain stiffness of Zenoz kaolin in unsaturated conditions

2012 ◽  
Vol 49 (3) ◽  
pp. 311-322 ◽  
Author(s):  
Mahnoosh Biglari ◽  
Anna d’Onofrio ◽  
Claudio Mancuso ◽  
Mohammad Kazem Jafari ◽  
Ali Shafiee ◽  
...  
Keyword(s):  
Shear Stiffness ◽  
Stress Path ◽  
Small Strain ◽  
Complex Stress ◽  
Resonant Column ◽  
Wetting And Drying ◽  
Isotropic Compression ◽  
Remarkable Effect ◽  
Constant Suction

An experimental study has been carried out to investigate the effects of isotropic compression, wetting, and drying on the initial shear stiffness of Zenoz kaolin, an unsaturated lean clay, both in normally consolidated and overconsolidated conditions. The proposed study was conducted using fixed–free resonant column – torsional shear (RCTS). Specimens were compacted using the undercompaction technique. Initial shear stiffness was measured almost continuously along complex stress paths including (i) an initial equalization stage to a suction value of 0, 50, 150, and 300 kPa; (ii) an isotropic compression stage at constant suction, up to a net stress high enough to move the loading collapse line; (iii) an isotropic unloading stage at constant suction; (iv) a wetting and (or) drying path. The mentioned stress path allowed elimination or determination of the overconsolidation effect on the initial shear stiffness measured. The behavior observed is qualitatively similar to that of saturated soil, while wetting data clearly indicate that G0 depends significantly on volumetric behavior. In normally consolidated samples where wetting is accompanied by collapse, reduction in suction has no remarkable effect on G0. Conversely, in overconsolidated samples G0 reduces significantly as suction decreases.

Simplified analyses of stress induced anisotropy in remolded soft clay under undrained conditions

2020 ◽  
Vol 2 (105) ◽  
pp. 56-64
Author(s):  
P. Lin ◽  
Z.-x. Li ◽  
A. Garg ◽  
J.S. Yadav
Keyword(s):  
Soft Clay ◽  
Constitutive Models ◽  
Stress Path ◽  
Complex Stress ◽  
Triaxial Tests ◽  
Induced Anisotropy ◽  
Stress Induced Anisotropy ◽  
Undrained Conditions ◽  
Plain Strain ◽  
Properties Of Soil

Purpose: The soil’s anisotropy induced by stress (i.e. stress induced anisotropy) has an important effect on the behavior of soil. This paper focuses on analyzing the anisotropy of remolded Shantou soft clay under compression stress path. Design/methodology/approach: Experiments were executed by using three axle experimental instruments. The data obtained from the plain strain tests were analyzed and the relationship between stress and strain was calculated by using the modified Duncan- Chang and Lade-Duncan models. The models were modified under the condition of plain strain and cohesion. Findings: It was concluded that in complex stress path conditions, the conventional triaxial tests may not fully reflect the actual stress of soil and its response in the Duncan-Chang and Lade-Duncan models. Research limitations/implications: The formulation of Mohr-Coulomb failure criterion in the plasticity framework is quite diffcult. As a result, dilatancy cannot be described. The properties of soil in unload or drained conditions remain to be part of further investigated. Practical implications: Based upon the two stiffness parameters, the modified Duncan- Chang model has captured the soil behaviour in a very conformable way and is recommened for practical modeling. These constitutive models of soil are widely used in the numerical analyses of soil structure such as embankments. Originality/value: Duncan-Chang and Lade-Duncan models widely used in engineering practices are modes based on conventional triaxial cases. Both models have have some inherent limitations to represent the stress-strain characteristics of soils, such as shear-induced dilatancy and stress path dependency and required corrections. In this investigation, the tests are carried out in undrained conditions. It is related to the properties of soil in load conditions.

scholarly journals The theory of degradation for polymer concrete in complex stress state

2019 ◽  
Vol 135 ◽  
pp. 01054
Author(s):  
Yuliya Moreva ◽  
Andrey Varlamov ◽  
Yuliya Novoselova
Keyword(s):  
Stress State ◽  
Uniaxial Compression ◽  
Complex Structure ◽  
Experimental Studies ◽  
Complex Stress ◽  
Complex Stress State ◽  
Polymer Concrete ◽  
Steel Shell ◽  
Concrete Core ◽  
Energy Characteristics

The article discusses the features of the application of the theory of degradation to the work of an integrated structure operating in a complex stress state. The analysis of the work of an integrated structure consisting of a steel shell filled with concrete (core structure). Based on the analysis of the construction work, we obtained the relations connecting the deformations of the steel shell and the polymer concrete core of the complex structure. The obtained relations made it possible to apply the diagrams of concrete work for uniaxial compression to analyze the possibility of using concrete as a core of an integrated structure. Experimental studies of the polymer concrete core of the structure were conducted. In total, ten concrete compositions were made and investigated. The compositions of concrete differed in cementitious: cement and polyester resin. As a filler used sand, gravel, ground clay, marble flour, soda and fine mineral fibers. Samples were tested for central and eccentric compression. During the tests used the methods used in testing cement concrete. As a result of the tests, complete schedules of the work of materials for uniaxial compression were obtained. The analysis of the energy characteristics of concrete schedules based on the theory of degradation is carried out. As a result of the discussion of the results obtained, conclusions are drawn about the possibility of using polymer concrete as the supporting core of an integrated structure with an external steel shell.

Brief Comments on “Unloading Rock Mechanics” and Engineering Applications

2012 ◽  
Vol 256-259 ◽  
pp. 211-214
Author(s):  
Bao Yun Zhao ◽  
Ke Shan Zhu
Keyword(s):  
Path Dependence ◽  
Scale Effects ◽  
Stress Path ◽  
Complex Stress ◽  
Linear Elastic ◽  
Deformation And Fracture ◽  
Excavation Process ◽  
Disturbed Zone ◽  
Excavation Disturbed Zone ◽  
Stress And Deformation

Since rock masses are not a true continuous, homogeneous, isotropic and linear-elastic (CHILE) continuum, the loading and unloading behaviors differ greatly from each other. Professor Ha Qiulin and his co-workers have demonstrated that strength and deformational characteristics, initial rock stresses, scale effects, creep, deformation and fracture patterns are quite different and stress path dependence is particularly emphasized. As engineering unloading of the rock mass is essentially of a dynamic nature by excavation, we will first discuss the excavation process and related stabilization techniques. For the complex stress and deformation conditions around the excavated boundaries, it seems rational to define an excavation disturbed zone (EDZ) as in the last decades. In tunnel excavation, temperature and ventilation effects should be also taken into account. Space-and-time dependence on tunnel behaviors is important. Finally, further research topics are discussed.

scholarly journals Testing and Micromechanical Modelling of Rockfill Materials Considering the Effect of Stress Path

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Wang Feng ◽  
Chi Shichun ◽  
Li Shijie ◽  
Jia Yufeng
Keyword(s):  
Stress Ratio ◽  
Volumetric Strain ◽  
Stress Path ◽  
Complex Stress ◽  
Triaxial Tests ◽  
Rockfill Material ◽  
Rockfill Materials ◽  
Deformation Properties ◽  
Confining Pressures ◽  
Improved Model

We have extended the micromechanics-based analytical (M-A) model to make it capable of simulating Nuozhadu rockfill material (NRFM) under different stress paths. Two types of drained triaxial tests on NRFM were conducted, namely, the stress paths of constant stress ratio (CSR) and the complex stress paths with transitional features. The model was improved by considering the interparticle parameter variation with the unloading-reloading cycles and the effect of the stress transition path. The evolution of local dilatancy at interparticle planes due to an externally applied load is also discussed. Compared with Duncan-Chang’s E-u and E-B models, the improved model could not only better describe the deformation properties of NRFM under the stress path loading, but also present the volumetric strain changing from dilatancy to contractancy with increasing transitional confining pressures. All simulations have demonstrated that the proposed M-A model is capable of modelling the mechanical behaviour of NRFM in the dam.

scholarly journals Unloading Effect of the Shear Resistance of Rock Joints

2021 ◽  
Author(s):  
Jianan Yang ◽  
Shuo Wang ◽  
Qiongting Wang ◽  
Wenzheng Xing ◽  
Pengxian Fan
Keyword(s):  
Normal Stress ◽  
Stress Ratio ◽  
Stress Path ◽  
Shear Resistance ◽  
Complex Stress ◽  
Rock Joints ◽  
Roughness Coefficient ◽  
Morphologic Characteristics ◽  
Path Dependent ◽  
Unloading Effect

Abstract To investigate the stress path dependent of rock joints, a comparative experimental study was conducted using cement mortar replicas of artificially split rock joints. In total, 32 replicas were casted and divided into four groups by joint roughness coefficient (JRC). The effects of morphologic characteristics, normal stress levels and stress paths on the shear strength of joints were investigated through tangential loading tests and normal unloading tests. The comparative analysis on the test results indicated that the shear resistance has a distinct unloading effect. The variation trend of shear/normal stress ratio against the normal stress and JRC of the two test conditions were identical. However, under low normal-stress condition, the stress ratio of the joints under normal unloading stress is the higher one; while under higher normal stress, the relationship becomes converse. Compared to that of the tangential loading condition, shear/normal stress ratio of the unloading stress path reduces rapidly as the increasing of normal stress, and the influence of the morphology is masked under lower normal stress. The comparative study revealed a previously unknown unloading effect on the mechanical behavior of rock joints and will aid the estimation of the rock joints’ stability in a complex stress environment.

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