scholarly journals Experimental and Theoretical Investigations of the Constitutive Relations of Artificial Frozen Silty Clay

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3159
Author(s):  
Zhiming Li ◽  
Jian Chen ◽  
Chaojun Mao
Keyword(s):  
Water Content ◽  
Strain Softening ◽  
Constitutive Relations ◽  
Random Variable ◽  
Confining Pressure ◽  
Silty Clay ◽  
Softening Behavior ◽  
Theoretical Investigations ◽  
Confining Pressures ◽  
Strength And Deformation

The strength and deformation characteristics of artificial frozen soils are quite sensitive to temperature, confining pressure, and water content. To investigate these effects, a series of triaxial compressive tests on frozen Harbin silty clay were conducted at temperatures of −5 °C, −10 °C, and −15 °C under different confining pressures and water contents. From the stress–strain curves under lower water content and confining pressure, strain–softening behavior was observed. The modified Duncan–Chang (MDC) model was employed to describe the constitutive relations of artificial frozen silty clay while considering the strain–softening effects. After introducing statistical damage (SD) theory, an SD constitutive model with the failure strain as a random variable was proposed, which is able to overcome the drawbacks of the MDC model. The predicted SD model results are found to be consistent with the experimental results.

scholarly journals Interval Nonprobabilistic Reliability Analysis for Ancient Landslide considering Strain-Softening Behavior: A Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zilong Zhou ◽  
Chenglong Lin ◽  
Xin Cai ◽  
Riyan Lan
Keyword(s):  
Reliability Analysis ◽  
Strain Softening ◽  
Constitutive Relations ◽  
Failure Surface ◽  
Normal Space ◽  
Probability Density Distribution ◽  
Probability Method ◽  
Uncertain Parameters ◽  
Ancient Landslide ◽  
Softening Behavior

Uncertainties in geotechnical parameters significantly affect the stability evaluation of an ancient landslide, especially when considering the strain-softening behavior. Due to the great difficulty in obtaining the probability density distribution of geoparameters, an interval nonprobability reliability analysis framework combined with numerical strain-softening constitutive relations was established in this paper. Interval variables were defined as the uncertain parameters in the strain-softening model. The interval nonprobabilistic reliability was defined as the minimum distance from the origin point to the failure surface in the standard normal space, which is the key index for describing the ability of a system to tolerate the variation of uncertain parameters. The proposed method was used to evaluate the reliability of Baishi ancient landslide. The parameter sensitivity analysis was also conducted. Through the proposed method, it is considered that Baishi ancient landslide is safe and stable, and the strain threshold kr is the dominant parameter. The results calculated by the proposed method agree well with the actual situation. This indicates the proposed method is more applicable than the traditional probability method when the data are scare.

Shear Test on Mixed Slide-Zone Soils of Landslide under Different Water Content

2011 ◽  
Vol 301-303 ◽  
pp. 1208-1213
Author(s):  
Ting Kai Nian ◽  
Zhong Kai Feng ◽  
Peng Cheng Yu ◽  
Hui Jun Wu
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Water Content ◽  
Strain Softening ◽  
Residual Soil ◽  
Strain Behavior ◽  
Softening Behavior ◽  
Direct Shear Apparatus ◽  
Slide Zone ◽  
Peak Value

This study is based on a typical residual soil landslide adjacent to Daxishan Reservior in Dalian city of China. By drilling the original samples in the field and remodeling the copy samples in the laboratory, a series of geotechnical experiments are carried out by the improved direct shear apparatus to obtain the changing law between the shear strength and water content of the mixed slide-zone soils. Emphasis is given on the shear stress-strain behavior and the corresponding constitutive model under different water content for the soils. Especially, the typical fitting equation is achieved to reflect the state of shear stress-normal stress-water content, some strain softening and hardening behavior on the mixed slide-zone soils of landslide is also discussed in detail. The results indicate that the shear strength is significantly related to water content of mixed slide-zone soils of landslide. The bigger water content of slide-zone soil is, the smaller the shear strength of soils is. When water content of mixed slide-zone soils approaches to certain value (i.e., 15%), the curve of shear stress and displacement shows a remarkable softening behavior, and the shear strength has marked a peak value.

Research on Post-Peak Characteristics of Elastic-Plastic Strain-Softening Model Based on Mohr-Coulomb Strength Criterions

2011 ◽  
Vol 261-263 ◽  
pp. 1439-1443
Author(s):  
Shao Qing Niu ◽  
Shuang Suo Yang ◽  
Lei Cui
Keyword(s):  
Rock Mass ◽  
Strain Softening ◽  
Triaxial Compression ◽  
Dynamic Change ◽  
Confining Pressure ◽  
Strength Parameters ◽  
Underground Engineering ◽  
Coulomb Failure ◽  
Confining Pressures ◽  
Damage Extent

Considering the characteristic that rock mass can transform from brittleness to plasticity and the dynamic change of post-peak strength parameters of the rock mass, the invariability of elastic modulus and poisson's ratio, constitutive model of rock mass could be described with the characteristic that strength parameters obey different Mohr-Coulomb failure criterions under different plastic strains. This model may reflect the post-peak subsequent characteristics of rock mass and the fact that rock mass can transform from brittleness to plasticity with the increase of confining pressure. Numerical calculation is applied to simulate the triaxial compression test under different confining pressures and underground engineering example, which proves that this model has the characteristic of reflecting the damage extent of surrounding rock.

scholarly journals Mechanical Modeling of Frozen Coarse-Grained Materials Incorporating Microscale Investigation

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Shan-Zhen Li ◽  
Liang Tang ◽  
Shuang Tian ◽  
Xian-Zhang Ling ◽  
Yang-Sheng Ye ◽  
...  
Keyword(s):  
Strain Softening ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Coarse Grained ◽  
Peak Strain ◽  
Compression Tests ◽  
Engineering Structures ◽  
Softening Behavior ◽  
Coarse Grained Material ◽  
Predicted Values

In the cold regions of China, coarse-grained materials are frequently encountered or used as backfilling materials in infrastructure construction, such as dams, highways, railways, and mineral engineering structures. Effects of confining pressure (0.2, 0.5, and 1 MPa) and frozen temperature (−2, −5, −10, and −15°C) on the stress-strain response and elastic modulus were investigated using triaxial compression tests. Moreover, the microscale structures of a coarse-grained material were obtained by X-ray computed tomography. The coarse-grained material specimens exhibited strain-softening and significant dilatancy behaviors during shearing. A modified model considering microstructures of the material was proposed to describe these phenomena. The predicted values coincided well with the experimental results obtained in this study and other literatures. The sensitivity analysis of parameters indicated that the model can simulate the initial hardening and post-peak strain-softening behavior of soils. And the transition of volume strain from contraction to dilatancy can also be described using this model. The results obtained in this study can provide a helpful reference for the analysis of frozen coarse-grained materials in geotechnical engineering.

scholarly journals Characteristics of Deformation and Damping of Cement Treated and Expanded Polystyrene Mixed Lightweight Subgrade Fill under Cyclic Load

2019 ◽  
Vol 9 (1) ◽  
pp. 167 ◽  
Author(s):  
Weihua Lu ◽  
Linchang Miao ◽  
Junhui Zhang ◽  
Yongxing Zhang ◽  
Jing Li
Keyword(s):  
Cement Content ◽  
Resilient Modulus ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Expanded Polystyrene ◽  
Total Strain ◽  
Repeated Loading ◽  
Silty Clay ◽  
Growth Trend ◽  
Confining Pressures

To investigate the deformation and damping characteristics of cement treated and expanded polystyrene (EPS) beads mixed lightweight soils, this study conducted a series of triaxial shear tests cyclic loading for different confining pressures, cement contents, and soil categories. Through repeated loading and unloading cycles, axial accumulative strain, resilient modulus, and damping ratio versus axial total strain were analyzed and the mechanical behavior was revealed and interpreted. Results show that the resilient modulus increases with increasing confining pressure and cement content. A decreasing power function can be used to fit the relationship between the resilient modulus and the axial total strain. Although sandy lightweight specimens usually own higher resilient modulus than silty clay lightweight specimens do, the opposite was also found when the axial total strain is larger than 8% with 50 kPa confining pressure and 14% cement content. For damping ratio the EPS beads mixed lightweight soil yields a weak growth trend with increasing axial total strain and a small reduction with higher confining pressure and cement content. For more cementations, the damping ratio of the sandy lightweight soil is always smaller than the silty clay lightweight soil. Nonetheless, the differences of damping ratios that were obtained under all of the test conditions are not significant.

Gas permeability of a compacted bentonite–sand mixture: coupled effects of water content, dry density, and confining pressure

2015 ◽  
Vol 52 (8) ◽  
pp. 1159-1167 ◽  
Author(s):  
Jiang-Feng Liu ◽  
Frédéric Skoczylas ◽  
Jean Talandier
Keyword(s):  
Water Content ◽  
Gas Permeability ◽  
Confining Pressure ◽  
Degree Of Saturation ◽  
Dry Density ◽  
Sand Mixture ◽  
Compacted Bentonite ◽  
High Confining Pressure ◽  
Confining Pressures ◽  
Gas Tightness

The gas-tightness of compacted bentonite–sand mixtures is important to the total sealing efficiency of geological repositories. The initial aim of this work was to determine whether the combination of a high confining pressure (Pc) and incomplete saturation could cause a bentonite–sand mixture to become gas-tight. The results show that the physical characteristics of the materials (degree of saturation, Sr; porosity, [Formula: see text]; and dry density, ρd) are very sensitive to changes in the applied confining pressures and their own swelling deformation (or shrinkage). The combination of these changes affects the sample’s effective gas permeability (Keff). For materials prepared at a relative humidity (RH) of 98%, Keff decreased from 10−16 to 10−20 m2 when Pc increased from 1 to 7 MPa. This means that gas-tightness can be obtained for a compacted bentonite–sand mixture when the materials experience a series of changes (e.g., w, Sr, [Formula: see text], and ρd). In addition, larger irreversible deformation (or hysteresis) was observed during the loading–unloading cycle for the sample with higher water content. This phenomenon may be attributed to larger interactions between the macrostructural and microstructural deformations and the decrease of preconsolidation pressure during hydration.

Influence Study of Confining Pressure on the Dynamic Parameters of the Silty Clay

2013 ◽  
Vol 353-356 ◽  
pp. 579-584
Author(s):  
Qiong Shen ◽  
Cong Cai ◽  
Qing Cheng Mo ◽  
Yong Ding Tian ◽  
Zhan Yuan Zhu
Keyword(s):  
Damping Ratio ◽  
Confining Pressure ◽  
Response Analysis ◽  
Dynamic Shear Modulus ◽  
Silty Clay ◽  
Resonant Column ◽  
Dynamic Parameters ◽  
Confining Pressures ◽  
Test Process ◽  
Made In

The dynamic parameters of silty clay in Dujiangyan under dynamic loading are studied with RCA resonant column apparatus made in GDS Company of British with different confining pressures. The results show that: The test process can be reproducible; the maximum dynamic shear modulus and damping ratio are increasing, and the shear strain amplitude is decreasing with increasing confining pressures. The empirical formula of the dynamic parameters of silty clay in Dujiangyan vs. confining pressures is formed. The study can provide basic data for seismic dynamic response analysis of soil.

Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

2021 ◽  
pp. 105678952199119
Author(s):  
Kai Yang ◽  
Qixiang Yan ◽  
Chuan Zhang ◽  
Wang Wu ◽  
Fei Wan
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Damage Evolution ◽  
Damage Assessment ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Damage Variable ◽  
Natural State ◽  
Carbonaceous Shale

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

Mechanical behaviour of powders using a medium pressure flexible boundary cubical triaxial tester

2003 ◽  
Vol 217 (3) ◽  
pp. 233-241 ◽  
Author(s):  
F Li ◽  
V M Puri
Keyword(s):  
Shear Modulus ◽  
Mechanical Behaviour ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Alumina Powder ◽  
Medium Pressure ◽  
Mean Pressure ◽  
Confining Pressures

A medium pressure (<21 MPa) flexible boundary cubical triaxial tester was designed to measure the true three-dimensional response of powders. In this study, compression behaviour and strength of a microcrystalline cellulose powder (Avicel® PH102), a spray-dried alumina powder (A16SG), and a fluid-bed-granulated silicon nitride based powder (KY3500) were measured. To characterize the mechanical behaviour, three types of triaxial stress paths, that is, the hydrostatic triaxial compression (HTC), the conventional triaxial compression (CTC), and the constant mean pressure triaxial compression (CMPTC) tests were performed. The HTC test measured the volumetric response of the test powders under isostatic pressure from 0 to 13.79MPa, during which the three powders underwent a maximum volumetric strain of 40.8 per cent for Avicel® PH102, 30.5 per cent for A16SG, and 33.0 per cent for KY3500. The bulk modulus values increased 6.4-fold from 57 to 367MPa for Avicel® PH102, 3.7-fold from 174 to 637 MPa for A16SG, and 8.1-fold from 74 to 597MPa for KY3500, when the isotropic stress increased from 0.69 to 13.79 MPa. The CTC and CMPTC tests measured the shear response of the three powders. From 0.035 to 3.45MPa confining pressure, the shear modulus increased 28.7-fold from 1.6 to 45.9MPa for Avicel® PH102, 35-fold from 1.7 to 60.5MPa for A16SG, and 28.5-fold from 1.5 to 42.8MPa for KY3500. In addition, the failure stresses of the three powders increased from 0.129 to 4.41 MPa for Avicel® PH102, 0.082 to 3.62 MPa for A16SG, and 0.090 to 4.66MPa for KY3500, respectively, when consolidation pressure increased from 0.035 to 3.45MPa. In addition, the shear modulus and failure stress values determined from the CTC test at 2.07, 2.76, and 3.45MPa confining pressures are consistently greater than those from the CMPTC test at the same constant mean pressures. This observation demonstrates the influence of stress paths on material properties. The CTT is a useful tool for characterizing the three-dimensional response of powders and powder mixtures.

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