scholarly journals Effects of Long-Term Freeze–Thaw Cycles on the Properties of Stabilized/Solidified Lead-Zinc-Cadmium Composite-Contaminated Soil

2021 ◽  
Vol 18 (11) ◽  
pp. 6114
Author(s):  
Zhongping Yang ◽  
Jiazhuo Chang ◽  
Yao Wang ◽  
Xuyong Li ◽  
Shu Li
Keyword(s):  
Compressive Strength ◽  
Contaminated Soil ◽  
Triaxial Compression ◽  
Soil Column ◽  
Column Leaching ◽  
Freeze Thaw ◽  
Triaxial Compressive Strength ◽  
Zinc Cadmium ◽  
Lead Zinc

Lead, zinc, and cadmium were used to prepare a composite-contaminated soil to replicate common situations, in which soil is usually simultaneously contaminated by multiple metals. To examine the long-term durability of stabilized/solidified (S/S) contaminated soil, specimens were subjected to a series of freeze–thaw (F-T) cycles, up to ninety times (one day per cycle), prior to testing. Triaxial compression tests, soil column leaching tests, and X-ray diffraction analysis were then employed to study the mechanical properties, environmental influences, and micro-mechanisms of the S/S lead-zinc-cadmium composite-contaminated soils after long-term F-T. The results showed that triaxial compressive strength increases within three F-T cycles, then decreases before slightly increasing or stabilizing after thirty F-T cycles. The stage of decreased cohesion thus occurs between three and fourteen F-T cycles, with variation in other factors similar to that of the triaxial compressive strength. The cohesion mainly increases between three and seven cycles. The soil column leaching test showed that the permeability of soil is more than four times higher than that of soil not subject to freeze–thaw cycles after ninety F-T cycles. XRD tests further revealed that the chemical composition of S/S contaminated soil and the occurrence of each heavy metal (HM) remained unchanged under F-T treatment.

scholarly journals Study on the variation of physical and mechanical characteristics under freeze-thaw condition

2020 ◽  
Vol 165 ◽  
pp. 03021
Author(s):  
Tian Yanzhe
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Physical And Mechanical Properties ◽  
Peak Stress ◽  
Friction Angle ◽  
Confining Pressure ◽  
Freeze Thaw ◽  
Triaxial Compressive Strength

Subjected to freeze-thaw cycles, the deformation of physical and mechanical properties is the main cause of engineering disasters. Based on the analysis of the results of triaxial compression test after different freeze-thaw cycles, conclusions are drawn that: under the certain freeze-thaw cycles conditions, with the increase of confining pressure, the triaxial compressive strength, elastic modulus and the axial strain increase gradually, indicating that the failure of rock changes from brittle failure to plastic failure; in the case of same confining pressure, with the increase of the number of freeze-thaw cycles, the triaxial compressive strength,elastic modulus of rock decreases and the axial strain corresponding to peak stress gradually increase. With the increase of the number of freeze-thaw cycles, the cohesion of grit is in the form of exponentially decays to reduce,the internal friction angle changes very little.

scholarly journals Mechanical and Failure Criteria of Air-Entrained Concrete under Triaxial Compression Load after Rapid Freeze-Thaw Cycles

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Feng-kun Cui ◽  
Huai-shuai Shang ◽  
Tie-jun Zhao ◽  
Guo-xi Fan ◽  
Guo-sheng Ren
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Stress Ratio ◽  
Triaxial Compression ◽  
Complex Stress State ◽  
Experimental Results ◽  
Testing System ◽  
Freeze Thaw ◽  
Triaxial Compressive Strength ◽  
Air Entrained Concrete

The experiment study on the air-entrained concrete of 100 mm cubes under triaxial compression with different intermediate stress ratioα2=σ2D : σ3Dwas carried out using a hydraulic-servo testing system. The influence of rapid freeze-thaw cycles and intermediate stress ratio on the triaxial compressive strengthσ3Dwas analyzed according to the experimental results, respectively. The experimental results of air-entrained concrete obtained from the study in this paper and the triaxial compression experimental results of plain concrete got through the same triaxial-testing-system were compared and analyzed. The conclusion was that the triaxial compressive strength is greater than the biaxial and uniaxial compressive strength after the same rapid freeze-thaw cycles, and the increased percentage of triaxial compressive strength over biaxial compressive strength or uniaxial compressive strength is dependent on the middle stress. The experimental data is useful for precise analysis of concrete member or concrete structure under the action complex stress state.

scholarly journals Influence of Water Pressure on the Mechanical Properties of Concrete after Freeze-Thaw Attack under Dynamic Triaxial Compression State

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Ruijun Wang ◽  
Yan Li ◽  
Yang Li ◽  
Fan Xu ◽  
Xiaotong Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Water Pressure ◽  
Mass Loss Rate ◽  
Triaxial Compression ◽  
Ultimate Compressive Strength ◽  
Peak Strain ◽  
Freeze Thaw ◽  
Dynamic Triaxial Compression

This study aims at determining the effect of water pressure on the mechanical properties of concrete subjected to freeze-thaw (F-T) attack under the dynamic triaxial compression state. Two specimens were used: (1) a 100 mm × 100 mm × 400 mm prism for testing the loss of mass and relative dynamic modulus of elasticity (RDME) after F-T cycles and (2) cylinders with a diameter of 100 mm and a height of 200 mm for testing the dynamic mechanical properties of concrete. Strain rates ranged from 10−5·s−1 to 10−3·s−1, and F-T cycles ranged from 0 to 100. Three levels of water pressure (0, 5, and 10 MPa) were applied to concrete. Results showed that as the number of F-T cycles increased, the mass loss rate of the concrete specimen initially decreased and then increased, but the RDME decreased. Under 5 MPa of water pressure and at the same strain rate, the ultimate compressive strength decreased, whereas the peak strain increased with the increase in the number of F-T cycles. This result is contrary to the variation law of ultimate compressive strength and peak strain with the increase in strain rate under the same number of F-T times. With the increase in F-T cycles or water pressure, the strain sensitivity of the dynamic increase factor of ultimate compressive strength and peak strain decreased, respectively. After 100 F-T cycles, the dynamic compressive strength under all water pressure levels tended to increase as the strain rate increased, whereas the peak strain decreased gradually.

scholarly journals Experimental Research on Mechanical Properties and Microstructure Characteristics of Silty Clay Subgrade Filler With Red Pisha Sandstone and Carbide Slag in Seasonal Frozen Regions

2021 ◽  
Author(s):  
Yuhang Liu ◽  
Dongqing Li ◽  
Feng Ming
Keyword(s):  
Mechanical Performance ◽  
Triaxial Compression ◽  
Strength Loss ◽  
Silty Clay ◽  
Freezing And Thawing ◽  
Highway Engineering ◽  
Freeze Thaw ◽  
Carbide Slag ◽  
Triaxial Compressive Strength ◽  
Improvement Effect

Abstract As the foundation structure of highway engineering, the quality of the subgrade determines the service life of highway engineering. Under this condition, the filling soils are frequently improved for raising the stability of the subgrade. Proper utilization of lower-cost waste materials will reduce demand for natural materials and the cost of construction. In this study, the red Pisha sandstone (RPS) and carbide slag (CS) as green and sustainable materials to reinforce the silty clay. The improvement effect was evaluated through freeze-thaw cycles test, triaxial compression strength test, particle-size distribution test, X-ray diffraction test, and scanning electron microscopy test. The results indicated that the addition of 15wt.% RPS and 15wt.% CS increased about 136% of the triaxial compressive strength of silty clay. With the increase of freeze-thaw cycles, the strength loss ratio and the deformation change slightly. It also has the excellent function of freezing and thawing resistance and shear strength. The key factors for the superior mechanical performance of RPS-CS stabilized silty clay are that more sand-size particles are beneficial to the hydration reactions of RPS and CS during the entire curing time, adequate flocculation and agglomeration of soil particles occurred. Many small-sized rounded and plate-like CSH gels filled most of the soils pores and isolated pores fractures became fewer in the samples, which produced a denser and less permeable material. The outcomes of this research will contribute to the utilization of red Pisha sandstone and carbide slag as a sustainable stabilizer in highway subgrade applications in seasonal frozen regions.

Effect of Water Chemical Corrosion on Strength and Cracking Characteristics of Rocks - A Review

2004 ◽  
Vol 261-263 ◽  
pp. 1355-1360 ◽  
Author(s):  
Xia Ting Feng ◽  
Shao Jun Li ◽  
Sih Li Chen
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Shear Strength ◽  
Water Chemistry ◽  
Chemical Corrosion ◽  
Long Term Stability ◽  
Effect Of Water ◽  
Triaxial Compressive Strength ◽  
Cracking Characteristics

Study of effect of water chemistry corrosion on strength and cracking characters of rocks is an important aspect to improve long-term stability of rock engineering and increase efficiency of geothermal and petroleum developing. This paper reviews new progress of study on this topic. It includes effect of water chemical corrosion on triaxial compressive strength, uniaxial compressive strength, shear strength, tensile strength, and cracking characteristics of rocks. The mechanism of water chemical corrosion is analyzed. The further study on this topic is also discussed.

scholarly journals Intelligent Prediction Model of the Triaxial Compressive Strength of Rock Subjected to Freeze-Thaw Cycles Based on a Genetic Algorithm and Artificial Neural Network

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xin Xiong ◽  
Feng Gao ◽  
Keping Zhou ◽  
Yuxu Gao ◽  
Chun Yang
Keyword(s):  
Neural Network ◽  
Genetic Algorithm ◽  
Artificial Neural Network ◽  
Compressive Strength ◽  
Rock Mass ◽  
Ann Model ◽  
Cold Regions ◽  
Freeze Thaw ◽  
Triaxial Compressive Strength ◽  
Artificial Neural

Rock compressive strength is an important mechanical parameter for the design, excavation, and stability analysis of rock mass engineering in cold regions. Accurate and rapid prediction of rock compressive strength has great engineering value in guiding the efficient construction of rock mass engineering in a cold regions. In this study, the prediction of triaxial compressive strength (TCS) for sandstone subjected to freeze-thaw cycles was proposed using a genetic algorithm (GA) and an artificial neural network (ANN). For this purpose, a database including four model inputs, namely, the longitudinal wave velocity, porosity, confining pressure, and number of freeze-thaw cycles, and one output, the TCS of the rock, was established. The structure, initial connection weights, and biases of the ANN were optimized progressively based on GA. After obtaining the optimal GA-ANN model, the performance of the GA-ANN model was compared with that of a simple ANN model. The results revealed that the proposed hybrid GA-ANN model had a higher accuracy in predicting the testing datasets than the simple ANN model: the root mean square error (RMSE), mean absolute error (MAE), and R squared ( R 2 ) were equal to 1.083, 0.893, and 0.993, respectively, for the hybrid GA-ANN model, while the corresponding values were 2.676, 2.153, and 0.952 for the simple ANN model.

scholarly journals Experimental Study on the Mechanical Properties of Sandstone under the Action of Chemical Erosion and Freeze-Thaw Cycles

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Lizhuang Cui ◽  
Nan Qin ◽  
Shuai Wang ◽  
Xuezhi Feng
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Triaxial Compression ◽  
Rock Properties ◽  
Chemical Solution ◽  
Compression Tests ◽  
Chemical Erosion ◽  
Freeze Thaw ◽  
The Impact

In order to study the mechanical properties of sandstone under the coupling action of chemical erosion and freeze-thaw cycles, the fine-grained yellow sandstone in a mining area in Zigong, China, is collected as the research object. The changes in mechanical properties of yellow sandstone under the coupling action of chemical solution erosion and freeze-thaw cycles are analyzed based on uniaxial compression tests (UCTs) and triaxial compression tests (TCTs). The results show that, with the increase in freeze-thaw cycles, the compressive strength, elastic modulus, and cohesion of the sandstone samples decrease with varying degrees. Under constant freeze-thaw cycles, the most serious mechanical properties of degradation are observed in acidic solution, followed by alkaline solution and neutral solution. Under different confining pressures, the compressive strength and elastic modulus of the sandstone samples decrease exponentially with the increase in freeze-thaw cycles. Under the action of the chemical solution erosion and freeze-thaw cycles, the internal friction angle fluctuates around 30°. For the cohesion degradation, 35.4%, 29.3%, and 27.2% degradation are observed under acidic, alkaline, and neutral solutions. Nuclear magnetic resonance imaging shows that the chemical erosion and freeze-thaw cycles both promote the degradation of rock properties from surface to interior; after 45 freeze-thaw cycles, the mechanical properties drop sharply. To properly design rock tunneling support and long-term protection in the cold region, the impact of both freeze-thaw cycles and chemical erosion should be considered.

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