scholarly journals Mechanical dilatancy and contraction effect of contaminated soil solidified by organic solvent

2020 ◽  
Vol 165 ◽  
pp. 02002
Author(s):  
Cheng Feng ◽  
Wei Cheng ◽  
Chen Aijun ◽  
Wu Di ◽  
Chen Junhua ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Organic Solvent ◽  
Contaminated Soil ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Soil Mass ◽  
Peak Strength ◽  
Strain Characteristic ◽  
Mix Proportion ◽  
Contraction Effect

The mix proportion experiment was applied to investigate the mix proportion scheme of organic soil mass curing agent, and the functional mechanism of organic solvent fused with soil mass was analyzed. Under conditions of low confining pressure (90~240kPa) and relative higher confining pressure (600~1200kPa), the consolidated drained triaxial shear test was applied to compare the mechanical dilatancy and contraction effect of undisturbed soil, contaminated soil and consolidated soil, and draw the mechanical volumetric strain characteristic curves. Then the volumetric strain characteristics of dilatancy and contraction behavior and their peak strength change rules of heavy metal contaminated soil, before and after consolidation, were analyzed. According to Pietruszczak’s hardening rule, the two yield surfaces volumetric strain model of heavy metal contaminated soil was established. Results indicate that heavy metal contaminated soil shows dilatancy property under the low confining condition and contraction property under high confining condition, while peak strength decreases obviously. Soil consolidation effectively improves the dilatancy volumetric strain characteristic under low confining condition, contraction volumetric characteristic under medium to high confining condition, and the peak strength increased significantly. This model makes up for the defect that the traditional single yield surface model cannot describe the critical strain state of dilatancy and contraction, and it reasonably reflects the volumetric strain change process of heavy metal contaminated soil.

scholarly journals Triaxial Compressive Failure Characteristics and Constitutive Model Study of Jurassic-Cretaceous Weakly Cemented Sandstone

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jinlong Cai ◽  
Wei Zou
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Ductile Failure ◽  
Mathematical Expression ◽  
Confining Pressure ◽  
Mining Area ◽  
Peak Strength ◽  
Correction Coefficient

A conventional triaxial compression test of Jurassic-Cretaceous typical weakly consolidated sandstone from a mining area in Ordos, China, was conducted using an MTS816 tester. Results showed that, before the peak, the rock had a distinct yield stage. When the specimen reached its peak strength, the strength decreased rapidly and showed an obvious brittle failure. When the confining pressure was increased to 15 MPa, the decrease of strength was slow and the rock tended toward ductile failure. With the increase of confining pressure, the cyclic strain initially increased slightly, whereas the volumetric strain increased greatly and the rock sample was in a compression state. When the load reached a critical value, the curve was reversely bent, resulting in volume expansion, whereas the peak strength, residual strength, and elastic modulus increased with confining pressure, and Poisson’s ratio decreased with the confining pressure. In the model based on macroscopic failure rock, the expression of the relationship between fracture angle and confining pressure provided a solid theoretical basis for the direction and failure mode of the macroscopic crack. Based on the rock strength theory and Weibull random distribution assumption of rock element strength, the damage variable correction coefficient was introduced when the residual strength was considered. Then, the mathematical expression of the 3D damage statistical constitutive model was established. Finally, the theoretical curve of the established constitutive model was compared with the triaxial test curve, which showed a high degree of coincidence.

Study on the Deformation and Strength Characteristics of Geotechnical Grille Reinforced Sand-Gravel under Low Confining Pressure

2011 ◽  
Vol 250-253 ◽  
pp. 2632-2639
Author(s):  
Bin Xu ◽  
De Gao Zou ◽  
Jing Bi ◽  
Xian Jing Kong ◽  
Tao Gong
Keyword(s):  
Residual Strength ◽  
Large Scale ◽  
Volumetric Strain ◽  
Friction Angle ◽  
Confining Pressure ◽  
Peak Strength ◽  
Strength Characteristics ◽  
Triaxial Tests ◽  
Reinforced Sand ◽  
Deformation And Strength Characteristics

A series of large scale consolidated drained shear triaxial tests were performed on reinforced and unreinforced sand-gravel specimens, the peak strength and residual strength characteristics of reinforced and unreinforced sand-gravel specimens were compared. The results show that: the peak strength, the residual strength and cohesion of reinforced sand-gravel are higher than unreinforced specimens, and is related to the characteristics of geotechnical grille used in this study. However, adding geotechnical grille has less effect on maximum volumetric strain and internal friction angle of sand-gravel.

scholarly journals Experimental Research into the Evolution of Permeability of Sandstone under Triaxial Compression

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5065
Author(s):  
Liming Zhang ◽  
Shengqun Jiang ◽  
Jin Yu
Keyword(s):  
Axial Strain ◽  
Triaxial Compression ◽  
Testing Machine ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Rate Of Change ◽  
Peak Strength ◽  
Sudden Increase ◽  
Seepage Pressure ◽  
Confining Pressures

Failure tests on sandstone specimens were conducted under different confining pressures and seepage pressures by using an MTS triaxial rock testing machine to elucidate the corresponding correlations of permeability and characteristic stress with confining pressure and pore pressure during deformation. The results indicate that permeability first decreases and presents two trends, i.e., a V-shaped increase and an S-shaped trend during the non-linear deformation stage. The greater the seepage pressure, the greater the initial permeability and the more obvious the V-shaped trend in the permeability. As the confining pressure was increased, the trend in the permeability gradually changed from V- to S-shaped. Compared with the case at a high confining pressure, the decrease of permeability occurred more quickly, the rate of change becomes greater, and the sudden increase observed in the permeability happened earlier under lower confining pressures. Within the range tested, confining pressure exerted a greater effect on the permeability than the seepage pressure. In comparison with the axial strain, volumetric strain better reflected changes in permeability during compaction and dilation of sandstone. The ratio of crack initiation stress to peak strength ranged from 0.37 to 0.50, while the ratio of dilation stress to peak strength changed from 0.58 to 0.72. Permeabilities calculated based on Darcy and non-Darcy flow changed within the same interval, while the change in permeability was different.

scholarly journals Application of nanoscale zero-valent iron in hexavalent chromium-contaminated soil: A review

2020 ◽  
Vol 9 (1) ◽  
pp. 736-750
Author(s):  
Xilu Chen ◽  
Xiaomin Li ◽  
Dandan Xu ◽  
Weichun Yang ◽  
Shaoyuan Bai
Keyword(s):  
Heavy Metal ◽  
Hexavalent Chromium ◽  
Contaminated Soil ◽  
Zero Valent Iron ◽  
Toxic Heavy Metal ◽  
Factors Affecting ◽  
Metal Pollutants ◽  
Nanoscale Zero Valent Iron ◽  
Low Toxicity ◽  
Heavy Metal Pollutants

AbstractChromium (Cr) is a common toxic heavy metal that is widely used in all kinds of industries, causing a series of environmental problems. Nanoscale zero- valent iron (nZVI) is considered to be an ideal remediation material for contaminated soil, especially for heavy metal pollutants. As a material of low toxicity and good activity, nZVI has been widely applied in the in situ remediation of soil hexavalent chromium (Cr(vi)) with mobility and toxicity in recent years. In this paper, some current technologies for the preparation of nZVI are summarized and the remediation mechanism of Cr(vi)-contaminated soil is proposed. Five classified modified nZVI materials are introduced and their remediation processes in Cr(vi)-contaminated soil are summarized. Key factors affecting the remediation of Cr(vi)-contaminated soil by nZVI are studied. Interaction mechanisms between nZVI-based materials and Cr(vi) are explored. This study provides a comprehensive review of the nZVI materials for the remediation of Cr(vi)-contaminated soil, which is conducive to reducing soil pollution.

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.

The Study of Remediation Standards of Heavy Metal-Cu Contaminated Soil Based on Risk Assessment

2011 ◽  
Vol 414 ◽  
pp. 93-98
Author(s):  
An Ping Liu ◽  
Xiao Nan Sun ◽  
Fang Yang ◽  
Xing Xing Yao
Keyword(s):  
Risk Assessment ◽  
Heavy Metal ◽  
Soil Remediation ◽  
Contaminated Soil ◽  
Assessment Model ◽  
Risk Assessment Model ◽  
Oral Ingestion ◽  
Cu Contamination ◽  
Standard Value ◽  
Exposure Methods

This paper describes the model of heavy metal-Cu contaminated soil remediation standard value based on risk assessment. In the Cu contamination risk assessment model, the main exposure methods are oral ingestion and inhalation through breathing, which not only simplifies the calculation but also make people get a clearer understanding of the way of Cu contamination. We get the simplified formula, calculate and discuss Cu contaminated soil remediation target value in specific parameters to provide reference and basis for the remediation of Cu contaminated soil.

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