Effect Of Drying-wetting Cycles Research Articles

Effects of drying-wetting cycles and free iron oxides on the mechanical behaviors of a partially decomposed granite residual soils

Effects of drying-wetting cycles and free iron oxides on the mechanical behaviors of a partially decomposed granite residual soils

Effect of drying-wetting cycles on the durability of calcareous sand reinforced by MICP and recycled shredded coconut coir (RSC)

Microbial-induced carbonate precipitation (MICP) technique has been adopted in geotechnical engineering widely. In this study, the effect of drying-wetting cycles on MICP-recycled shredded coconut coir (RSC) reinforced calcareous sand was studied, and the deterioration mechanism under drying-wetting cycles was revealed. Test results indicated that drying-wetting cycles exert an important influence on the durability of MICP-RSC reinforced specimens. With the increase of drying-wetting cycles N, the specimens demonstrated significant increase in mass loss rate and critical void ratio, decrease in maximum shear modulus, peak strength and toughness. Furthermore, an increase in the initial relative density reduced the deterioration of MICP-RSC reinforced specimens exposed to drying-wetting cycles. Higher initial relative density of the specimen correlates with an increased maximum shear modulus, peak stress and toughness, a decreased in permeability and critical void ratio. Microanalysis revealed that the generated calcium carbonate adhering to sand particles and RSC gradually dropped off with the increase of N, weakened cementation, and led to the deterioration of MICP-RSC reinforced specimens, which is consistent with the deterioration characteristics under drying-wetting cycles.

Effect of drying-wetting cycles on pore characteristics and mechanical properties of enzyme-induced carbonate precipitation-reinforced sea sand

Enzyme-induced carbonate precipitation (EICP) is an emanating, eco-friendly and potentially sound technique that has presented promise in various geotechnical applications. However, the durability and microscopic characteristics of EICP-treated specimens against the impact of drying-wetting (D-W) cycles is under-explored yet. This study investigates the evolution of mechanical behavior and pore characteristics of EICP-treated sea sand subjected to D-W cycles. The uniaxial compressive strength (UCS) tests, synchrotron radiation micro-computed tomography (micro-CT), and three-dimensional (3D) reconstruction of CT images were performed to study the multiscale evolution characteristics of EICP-reinforced sea sand under the effect of D-W cycles. The potential correlations between microstructure characteristics and macro-mechanical property deterioration were investigated using gray relational analysis (GRA). Results showed that the UCS of EICP-treated specimens decreases by 63.7% after 15 D-W cycles. The proportion of mesopores gradually decreases whereas the proportion of macropores increases due to the exfoliated calcium carbonate with increasing number of D-W cycles. The microstructure in EICP-reinforced sea sand was gradually disintegrated, resulting in increasing pore size and development of pore shape from ellipsoidal to columnar and branched. The gray relational degree suggested that the weight loss rate and UCS deterioration were attributed to the development of branched pores with a size of 100–1000 μm under the action of D-W cycles. Overall, the results in this study provide a useful guidancee for the long-term stability and evolution characteristics of EICP-reinforced sea sand under D-W weathering conditions.

Dynamic stability assessment of reservoir colluvial landslide using a hypoplastic clay constitutive model considering the effects of drying-wetting cycles on the hydro-fluctuation belt

The hydro-fluctuation belt of reservoir landslides undergoes repeated drying-wetting (D–W) cycles due to the annual fluctuation of water level in the Three Gorges Reservoir Area. Mechanical properties of the hydro-fluctuation belt subjected to D-W cycles should be considered for the evolution of landslide stability affected by seasonal rainfall and periodic reservoir water fluctuations. In addition, a reliable constitutive model essential for evaluating landslide stability should be employed to describe the mechanical property of soil. In this study, taking the Tangjiao landslide as an example, a series of drained triaxial and oedometer tests were conducted to study the effects of D-W cycles on the shearing and compression behaviors of the sliding mass soil. Then, the time-varying parameters of a hypoplastic clay constitutive model were calibrated based on the soil experiments under different D-W cycles. Eventually, the hydro-mechanical coupled simulation analyses were performed to study long-term deformations of the landslide front part influenced by actual rainfall and reservoir water fluctuations. Moreover, the evolution of landslide stability was analyzed using the vector-sum method based on stress fields with different time steps. The test results show that the D-W cycle significantly affects the mechanical property of soil. The hypoplastic model predicts well the shearing and compression behaviors of soil under different D-W cycles. The numerical results indicate that the soil weakening in the hydro-fluctuation belt increases the deformation magnitude of the toe slope and gradually decreases the landslide stability. This study provides some references for the dynamic stability assessment and long-term hydro-mechanical simulation of reservoir landslides.

Effects of drying-wetting cycles on the salinity and the mechanical behavior of sebkha soils. A case study from Ain M'Lila, Algeria

Sebkha soils are defined as problem soils located in arid, semi-arid, and coastal areas. Generally, they are fine soil, composed of silt, sand, and clay, which are cemented by different salts (e.g., halite, gypsum, and calcite). In nature, sebkha saline soils are exposed to different drying and wetting (D-W) cycles. However, these cycles have a significant effect on the mechanical behavior of these soils. This study aims to characterize the chemical, mineralogical, and geotechnical properties of sebkha soil using an experimental approach. We focus on the effects of D-W cycles on the unconfined compressive strength (UCS) and salinity of sebkha soils from Ain M'Lila, Algeria. In addition, these D-W cycles were applied to the samples dried in the open air to achieve the targeted water content (water content values of 7%, 11.4%, and 13%). The results obtained show that the UCS increases with decrease in water content and decreases with an increase in the number of D-W cycles. In addition, these cycles affect the salinity of the sebkha soil. Indeed, a significant decrease in soil salinity was recorded with an increase in the number of D-W cycles. Finally, a relationship was found between the salinity of the soil and UCS. The latter decreases with a decrease in soil salinity; this relationship becomes very significant for low water content values of 7% or less.

Effects of Drying-Wetting Cycles on the Microstructure and Mechanical Properties of Granite Residual Soils

Effects of Drying-Wetting Cycles on the Microstructure and Mechanical Properties of Granite Residual Soils

Shear Strength Deterioration of Compacted Residual Soils under a Wind Turbine due to Drying-Wetting Cycles and Vibrations

The soil beneath a wind turbine withstands not only environmental impacts but also continuous vibrations transmitted from the superstructure. This paper presents an experimental study of the deterioration characteristics of shear strengths of residual soils affected by drying-wetting cycles and continuous vibrations. A series of triaxial tests were performed on compacted residual soil specimens after various drying-wetting cycles and vibrations. The influences of drying-wetting cycles and vibrations on the shear strengths of residual soils with different compaction degrees were analyzed. The results demonstrate that the shear strength and cohesion of compacted residual soils decreased as the number of drying-wetting cycles increased, and they tended to be stable after three drying-wetting cycles. The angle of internal friction decreased linearly with the reduction of compaction degree but was generally not affected by drying-wetting cycles. The shear strength of compacted residual soils also decreased because of continuous vibrations. After 10000 vibrations, the strength was stabilized gradually. Both the cohesion and angle of internal friction showed dynamic attenuation phenomenon. Finally, a modified Mohr–Coulomb strength equation considering the effects of drying-wetting cycles and vibrations was established. This equation could be used to predict the shear strength of compacted residual soils and further estimate the embedded depth of wind turbine foundations.

Water infiltration in a cracked soil considering effect of drying-wetting cycles

Infiltration is of great concern in many fields like hydrology, agriculture as well as geotechnical and geological engineering. This study aims to investigate water infiltration in a cracked soil. Infiltration tests were conducted on compacted soil samples with different cracking degrees by drying to various water contents. Three drying-wetting cycles were applied. Experimental results show that no desiccation cracks are observed in the first drying process while cracks initiate and propagate in the second and third drying processes. Different from the infiltration curve of the non-cracked soil sample consisting of two distinct stages, that of the cracked soil consists of three distinct stages, representing constant, rapid reduction and gradual reduction in infiltration rate, respectively. A modified equation is proposed to describe the infiltration behavior of a cracked soil considering the prehealing time of cracks. Furthermore, it is found that for the tested soil, 4% of surface crack ratio is a critical value. When surface crack ratio is smaller than the critical value, its influence on infiltration capacity is insignificant. Afterwards, the infiltration capacity increases dramatically with increasing surface crack ratio. Based on this observation, a piecewise function is proposed to characterize the relationship between the normalized infiltration capacity of cracked soil and surface crack ratio. Infiltration capacity also increases with decreasing initial water content and increasing number of drying-wetting cycles. In terms of steady final infiltration rate, it increases with increasing initial water content as well as increasing number of drying-wetting cycles, but is not affected by desiccation cracking.

The effects of suction history on the cyclic behavior of unsaturated road base filling materials

Road base is usually subjected to cyclic traffic loadings as well as environment loads. Evidence shows that excessive permanent deformation of the road base may occur under the action of traffic loads and the complicated suction history induced by climate change. Currently, how the suction history of road base affects its long-term deformation remains unclear. To gain a deep understanding of the long-term deformation of road base, cyclic loading tests were conducted on the road base aggregates (mixture of crushed tuff aggregates and clay fines) under controlled suction and suction histories. A large-size soil-water characteristic curve (SWCC) test apparatus was designed and manufactured for the water retention test of the large-size specimen, and the large-diameter cyclic triaxial testing system (LDCTTS) was upgraded with the unsaturated control system to control the matric suction and suction history during the cyclic loading test. Test results show that the permanent axial strain of the mixture has a negative correlation with the current suction and maximum suction history. The effect of drying-wetting cycles on the permanent axial strain is significant. The permanent axial strain decreases with drying-wetting cycles at the drying path, while increases with drying-wetting cycles at the wetting path. The resilient modulus increases significantly with the current suction magnitude while is independent of the suction history.

Effects of Drying-Wetting Cycles on the Mechanical Behavior of Reconstituted Granite-Residual Soils

AbstractIn Central South of China, granite residual soil (GRS) is one of the main subgrade soils for transportation infrastructures. To further understand the effects of drying and wetting (D-W) cy...

Resistance of Recycled Aggregate Concrete (RAC) Subjected to Drying-Wetting Cycles to Attack of Magnesium and Sodium Sulfates

Recycled aggregates were widely used in the concrete industry as a replacement of natural aggregates in the last two decades. In this study, the resistance of concrete mixtures having various levels of recycled aggregate as a replacement of natural coarse aggregate to the attack of magnesium and sodium sulfates was investigated. Five mixtures made with 0%, 25%, 50%, 75%, and 100% recycled aggregate were partially immersed in magnesium and sodium sulfate solutions having concentrations of 2.5%, 4.5%, and 6.5% and subjected to drying-wetting cycles for a total of 10 weeks. Mass losses of concrete specimens owing to the attack of sulfate solutions and the effect of drying-wetting cycles were recorded weekly. Results show that the incorporation of recycled aggregate decreased the compressive strength of concrete at ages of 7 and 28 days. The decline in the compressive strength was more significant when the replacement percentage exceeds 50%. Mass losses of concrete specimens were found to be increased as the level of recycled aggregate increased. Mass losses of concrete specimens having 100% recycled aggregate were approximately as twice as those of concrete specimens having 0% recycled aggregate owing to 10 weeks of partial immersion in magnesium sulfate solutions of concentrations of 2.5%, 4.5%, and 6.5%. The attack of sodium sulfates was less aggressive than that of the magnesium sulfates. Results also show that the reduction in the compressive strength is directly proportional to the mass loss following a linear equation of R-squared value of 0.937.

Drying-wetting cycles consistently increase net nitrogen mineralization in 25 agricultural soils across intensity and number of drying-wetting cycles

An increase in extreme weather events such as heavy rainfall and extreme drought causes intensive and frequent drying-wetting (DW) cycles, which have strong effects on the availability of nitrogen (N) for plant growth and development. How the effects of DW cycles on N turnover vary with the intensity and number of DW cycles and soil properties has not been clearly addressed, which hinders predicting soil biogeochemical cycles in a changing world. Herein, we examined the response of net N mineralization in agricultural soils measured at a standard temperature (25 °C) to DW cycles varying in intensity and number. A total of 25 soils differing in texture and organic matter content were collected to create a soil property gradient. We also established the relationships of DW cycle effects on net N mineralization to soil properties. The DW cycles significantly increased N mineralization by 11.05 ± 0.66 mg kg−1 (+81.7%), and the increase was consistent across DW intensities and numbers for most soils. The release of inorganic N was dependent on soil properties, while the regulation of soil properties on DW effects varied with DW intensity, with stronger regulation under intense DW cycles (60% to 0% field capacity) than under moderate DW cycles (100% to 20% field capacity). The effect of intense DW cycles on NH4+ increased with clay content but decreased with soil pH and sand content. The effect on NO3− has opposite responses to these soil properties when compared with the effects on NH4+. The effect on total inorganic N increased with soil pH and inorganic N concentration. These results indicated that DW cycles have the potential to increase N availability in agricultural soils and highlighted the underestimation of N availability predicted with averaged soil moisture instead of real-time soil moisture under changing soil moisture conditions.

Effects of Drying-Wetting Cycles on Durability of Carbonated Reactive Magnesia-Admixed Clayey Soil

AbstractThe durability of CO2-carbonated reactive magnesia (MgO)-admixed clayey soils against drying-wetting cycles has not been well understood now despite the fact that the engineering properties...

Effects of Drying-Wetting Cycles on Soil-Water Characteristic Curve

Alternate drying-wetting cycle is considered to be one of the important factors that can affect the hydro-mechanical properties of soil. Due to the variability of climatic condition, soils are experienced by multiple drying-wetting cycles. But most of the previous studies on soil physical and mechanical properties are limited to a single drying-wetting cycle. This study is conducted to evaluate the effects of multiple drying-wetting cycles on SWCC. The microfabric changes are also studied by Scanning Electron Microscopy (SEM) which shows that soil particles are drawn closer together with increasing the drying-wetting cycles and led to a variation of microstructure. The SWCC results show that with increasing drying-wetting cycles the water content and water retention capacity decrease. The air entry value decreases with increasing drying-wetting cycles and the curves shift to the left. The impact of first drying-wetting cycle is more and decreases with subsequent cycles and reaches an equilibrium state after 4 drying-wetting cycles. The relationship between the van Genuchten model parameters and the number of drying-wetting cycles of investigated soil can be described by an exponential function.

Effect of drying-wetting cycles on leaching behavior of cement solidified lead-contaminated soil

Lead contaminated soil was treated by different concentration of ordinary Portland cement (OPC). Solidified cylindrical samples were dried at 40°C in oven for 48h subsequent to 24h of immersing in different solution for one drying-wetting. 10 cycles were conducted on specimens. The changes in mass loss of specimens, as well as leaching concentration and pH of filtered leachates were studied after each cycle. Results indicated that drying-wetting cycles could accelerate the leaching and deterioration of solidified specimens. The cumulative leached lead with acetic acid (pH=2.88) in this study was 109, 83 and 71mg respectively for solidified specimens of cement-to-dry soil (C/Sd) ratios 0.2, 0.3 and 0.4, compared to 37, 30, and 25mg for a semi-dynamic leaching test. With the increase of cycle times, the cumulative mass loss of specimens increased linearly, but pH of filtered leachates decreased. The leachability and deterioration of solidified specimens increased with acidity of solution. Increases of C/Sd clearly reduced the leachability and deterioration behavior.

Short-Term Responses of Nitrogen Mineralization and Microbial Community to Moisture Regimes in Greenhouse Vegetable Soils

Soil drying and wetting impose significant influences on soil nitrogen (N) dynamics and microbial communities. However, effects of drying-wetting cycles, while common in vegetable soils, especially under greenhouse conditions, have not been well studied. In this study, two greenhouse vegetable soils, which were collected from Xinji (XJ) and Hangzhou (HZ), China, were maintained at 30% and 75% water-holding capacity (WHC), or five cycles of 75% WHC followed by a 7-day dry-down to 30% WHC (DW). Soil inorganic N content increased during incubation. Net N mineralization (Nmin), microbial activity, and microbial biomass were significantly higher in the DW treatment than in the 30% and 75% WHC treatments. The higher water content (75% WHC) treatment had higher Nmin, microbial activity, and microbial biomass than the lower water content treatment (30% WHC). Multivariate analyses of community-level physiological profile (CLPP) and phospholipid fatty acid (PLFA) data indicated that soil moisture regime had a significant effect on soil microbial community substrate utilization pattern and microbial community composition. The significant positive correlation between Nmin and microbial substrate utilization or PLFAs suggested that soil N mineralization had a close relationship with microbial community.