Coupling effect of heat-moisture-stress on the freeze-thaw characteristics of slope supported with framed anchor

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiang Tian ◽  
Li Yuan-xun ◽  
Ye Shuai-hua ◽  
Li Hui
Keyword(s):  
Coupling Effect ◽  
Moisture Stress ◽  
Freeze Thaw

scholarly journals Microscopic Characteristic Analysis on Sandstone under Coupling Effect of Freeze–Thaw and Acidic Treatment: From Nuclear Magnetic Resonance Perspective

2020 ◽  
Vol 10 (16) ◽  
pp. 5699
Author(s):  
Songtao Yu ◽  
Hongwei Deng ◽  
Guanglin Tian ◽  
Junren Deng
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Acid Solution ◽  
Coupling Effect ◽  
Fractal Dimensions ◽  
Total Porosity ◽  
Characteristic Analysis ◽  
Freeze Thaw ◽  
Ph Decrease ◽  
Nuclear Magnetic

Microscopic characteristics greatly affect mechanical and physical properties as they exert vital impact on the stability and durability of materials. In this paper, widely distributed sandstone was chosen as the research object. Sandstone was treated with a coupled effect of Freeze–Thaw (F–T) weathering and acid solution, where freeze–thaw cycles were set as 0, 10, 20, 30 and 40 cycles, and the pH of the acid solution were set as 2.8, 4.2, 5.6 and 7.0, respectively. Then, nuclear magnetic resonance was applied to measure the microscopic characteristics of sandstone, then porosity, pore size distribution and permeability before the fractal dimensions were obtained and calculated. Results show that porosity increases when F–T cycles increase, and its increase grows with the pH of acid solution decrease during the first 10 F–T cycles. Macro porosity, meso porosity and micro porosity account for the largest, second largest and smallest ratio of porosity growth. Meso porosity, micro porosity and macro porosity account for the largest, second largest and smallest ratio of total porosity. Permeability increases obviously with F–T cycle increase, while acid erosion exerts little influence on permeability increment overall. Fractal dimensions of meso pores and macro pores increase with F–T cycle increase overall, and they increase with pH decrease overall. Porosity has strong exponentially correlation with permeability. Fractal dimensions of meso pores and macro pores have good linearly correlation with permeability, while correlation between porosity and fractal dimensions are not that obvious.

Damage Model and Damage Mechanical Characteristics of Loaded Rock under Freeze-Thaw Conditions

2010 ◽  
Vol 168-170 ◽  
pp. 658-662 ◽  
Author(s):  
Hui Mei Zhang ◽  
Geng She Yang
Keyword(s):  
Mechanical Properties ◽  
Structural Damage ◽  
Damage Mechanics ◽  
Coupling Effect ◽  
Damage Model ◽  
Engineering Structures ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Loaded Rock ◽  
Total Damage

Considering the heterogeneous characteristics of rock at mesoscopic level, the damage propagation constitutive relation and evolution equation of freeze-thaw and loaded rock were established by using the theory of macro phenomenological damage mechanics and the generalized theory of strain equality. The evolutionary mechanisms of micro-structural damage and materials mechanical properties for the loaded rock were discussed under freeze-thaw condition, verified by experimental results of the freeze-thaw cycle and compression test of rock. It is shown that the freeze-thaw and loaded damage model can represent the complicated relations among the freeze-thaw, load and the damage inside the rock, reveal the coupling failure mechanism of macroscopic rock under the freeze-thaw and load from the micro-damage evolution. The combined effect of freeze-thaw and load exacerbates the total damage of rock with obvious nonlinear properties, but the coupling effect weakens the total damage. The lithology and initial damage state of the freeze-thaw and loaded rock in engineering structures in cold regions determine the weights of influence factors to mechanical properties, including environmental factor, loading factor and the coupling effects, so the rock performances different damage mechanical characteristic.

scholarly journals Coupling Effect of Strain Rate and Freeze-Thaw Temperature on Dynamic Mechanical Properties and Fractal Characteristic of Saturated Yellow Sandstone

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Peng Wu ◽  
Lianying Zhang ◽  
Xianbiao Mao ◽  
Yanlong Chen ◽  
Ming Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fractal Dimension ◽  
Strain Rate ◽  
Room Temperature ◽  
High Strain ◽  
Coupling Effect ◽  
Strain Rate Effect ◽  
Dissipated Energy ◽  
Peak Strain ◽  
Freeze Thaw

Strain rate is not only an important influence factor for deformation property but also an important parameter for analyzing the dynamic mechanical behavior of rock material. In this study, the dynamic compressive mechanical properties of saturated yellow sandstone at four strain rates and six freeze-thaw temperatures are investigated by using the SHPB test system. The coupling effect of strain rate and freeze-thaw temperatures on the mechanical parameters of rock material are discussed in detail, and the relationship formula of peak strain and dissipated energy with strain rate and freeze-thaw temperature are also established. Finally, the fractal dimension characteristic of fracture specimens with the strain rate and temperature are analyzed by using the fractal dimension method. The research results indicate that (1) with the increase of strain rate, the increase speed of peak strain, peak strength, and dissipated energy at medium strain rate level was obviously higher than that at high strain rate level, indicating that the strain rate effect weakened at high strain rate. (2) Freeze-thaw temperature can improve the brittleness-ductile transformation rate of saturated specimens. (3) According to the strain rate sensitivity coefficient, at room temperature, the strain rate effects on peak strain and peak strength are weakest, while at -20°C ~ -30°C, they are most significant. In addition, the strain rate effect on dissipated energy is significant at room temperature, while weakest at -30°C. (4) The fractal dimension gradually increases with strain rate increasing or freeze-thaw temperature decreasing, indicating that the freeze-thaw environment has a positive function for increasing the damage and fracture degree of specimens for saturated specimen. Our research results can provide an extremely important theoretical basis for the dynamic disaster prevention and structural design of rock engineering in cold regions.

scholarly journals Coupling Effect of Salt Freeze-Thaw Cycles and Carbonation on the Mechanical Performance of Quick Hardening Sulphoaluminate Cement-Based Reactive Powder Concrete with Basalt Fibers

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1142
Author(s):  
Guoping Huang ◽  
Hui Wang ◽  
Feiting Shi
Keyword(s):  
Flexural Strength ◽  
Mechanical Performance ◽  
Coupling Effect ◽  
Quadratic Function ◽  
Reactive Powder Concrete ◽  
Basalt Fibers ◽  
Freeze Thaw ◽  
Sulphoaluminate Cement ◽  
Reactive Powder ◽  
Mechanical Strengths

The effect of salt freeze-thaw cycles coupled with carbonation on the mechanical performance of quick hardening sulphoaluminate cement-based reactive powder concrete combined with basalt fibers was investigated. The ratios of basalt fibers in sulphoaluminate cement-based reactive powder concrete (SAC-RPC) were 1%, 2%, 3% and 4% by the volume of concrete. The mechanical strengths (compressive strength, flexural strength and bonding strength) of SAC-RPC were investigated after curing for 5 h, 1 d, 14 d and 28 d, respectively. Meanwhile, the mechanical strengths of resultant concrete were detected, when different NaCl freeze-thaw cycles and carbonation were adopted. Results showed that the addition of basalt fibers could effectively improve the mechanical strengths, especially the flexural strength of SAC-RPC. The dosage of 3.0% was the threshold value affected mechanical strengths. The flexural, compressive and bonding strengths of SAC-RPC were higher than 8.53 MPa, 34 MPa and 3.21 MPa, respectively. The mass loss and mechanical strengths loss of SAC-RPC increased in the form of quadratic function with the increasing number of NaCl freeze-thaw cycles and varied in the form of quadratic decreasing function. Meanwhile, the effect of carbonation on the mechanical strengths of SAC-RPC can be ignored. Additionally, the coupling effect of salt freeze-thaw cycles and carbonation could accelerate the attenuation of concrete strength. The mechanical strengths loss demonstrated a decreased quadratic function with the increasing volume of basalt fibers.

scholarly journals Investigation on Durability Behaviour and Optimization of Concrete with Triple-Admixtures Subjected to Freeze-Thaw Cycles in Salt Solution

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Xuejiao Li ◽  
Wensheng Wang ◽  
Zhiqing Zhu ◽  
Kunkun Zheng
Keyword(s):  
Salt Solution ◽  
Coupling Effect ◽  
Orthogonal Experiment ◽  
Cold Climate ◽  
Working Environment ◽  
Mineral Admixtures ◽  
Cement Concrete ◽  
Chloride Permeability ◽  
Freeze Thaw ◽  
Air Entrained Concrete

In the seasonal frozen area of northeast China, cement concrete is usually in a working environment of cold climate and chlorine erosion coupling effect. In general, with a reasonable addition of air entraining agent (AEA) and multimineral admixtures such as fly ash, blast furnace slag, and silica fume, the durability of cement concrete under the effects of freeze-thaw and salt solution can be significantly improved in cold regions. However, due to several more compositions of cement concrete with multiple mineral admixtures, it would take excessive trial mixtures to select the desired mixture proportion based on the conventional method. This means a great deal of costs of raw materials and laboratory experimental time. In this paper, the experimental scheme of mixture proportion for air-entrained concrete with multimineral admixtures was designed based on the orthogonal experiment design method. Based on the compressive strength, rapid chloride permeability, and weight loss and relative dynamic elastic modulus after salt freeze-thaw cycles, the influence of different mineral admixtures and their dosages on the durability of concrete subjected to freeze-thaw in salt solution was analyzed. After that, based on genetic algorithm, an optimization of mixture proportion was proposed, which only requires less trial mixes and accessible optimization process. The test results indicated the superiority of air-entrained concrete with multimineral admixtures when serving in salt freeze-thaw environment. Eventually, it was also verified that the optimized concrete in this paper could achieve pleasurable durability performances under salt freeze-thaw cycles.

Damage Evolution of Concrete by Electrical Resistivity Monitoring Methods

2015 ◽  
Vol 796 ◽  
pp. 85-89
Author(s):  
Shuang Lu ◽  
Li Na Zhou ◽  
Zheng Wang
Keyword(s):  
Electrical Resistivity ◽  
Damage Evolution ◽  
Electrochemical Impedance ◽  
Coupling Effect ◽  
Resistivity Measurement ◽  
Electrical Resistivity Measurement ◽  
Monitoring Methods ◽  
Surrounding Water ◽  
Freeze Thaw ◽  
Hydraulic Concrete

The leaching behavior of hydraulic concrete can’t be neglected for its long-term exposure to surrounding water resulting in irreversible damage to durability, such as strength loss and porosity increase. Given that the coupling effect of leaching and freeze-thaw cycling on the durability of hydraulic concrete especially in severe cold regions is a big challenge. For the quite slow process of natural leaching, electrochemical accelerated leaching method (EALM) was proposed to investigate the damage evolution under two test schemes (scheme one is only leaching for 50 days and scheme two is first 100 rapid freeze-thaw cycles and then leaching for 50 days) designed in this work. The electrical resistivity and calcium oxide dissolution mass were measured through electrochemical impedance spectroscopy (EIS), namely two-probe method, and EDTA titration method, respectively. Based on electrical resistivity measurement, the measurable damage can be discussed during abovementioned singe and coupled tests. The results indicate that compared with single leaching test, the leaching coupled with the freeze-thaw cycling leads to over 50% electrical resistance loss.

Evaluation of Ultimate Serviceable State of the Cross-Sea Bridge Pier under Freeze-Thaw and Erosion Coupling Effect

2012 ◽  
Vol 256-259 ◽  
pp. 1484-1491
Author(s):  
Qian Qiao Zhao ◽  
Lu Jin
Keyword(s):  
Coupling Effect ◽  
Strength Criterion ◽  
Engineering Calculation ◽  
Assessment Method ◽  
Bridge Pier ◽  
Wave Load ◽  
Freeze Thaw ◽  
Concrete Pile ◽  
Pile Cap ◽  
Durability Assessment

In order to put forward a durability assessment method of concrete structure based on the engineering calculation and analysis, combining with the characteristics of northern freezing coastal areas and the non-navigable spans bridge construction，the paper built the Ottosen strength criterion on concrete under freeze-thaw and erosion coupling effect. By the application of strength criterion, calculation and analysis, it has been evaluated the crack resistance at a few key points of the concrete pile cap on the bottom. The result illustrates that there will appear concrete cracks at the middle of the cushion cap bottom after a 130-year serviceable period when the bridge is attacked by the once-in-a-century wave load or ice load, that is, the safety serviceable period of the bridge pier is 130 years.

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