Dry Cycles Research Articles

Evaluation of water treatments on surfaces to inhibit bacterial spore resuspension

AbstractThe impact of water and the wet–dry cycle was examined as a potential mitigation solution to pathogenic bacterial spore transport and inhalation risk via resuspension of spores from surfaces due to human activities. In this study, a fine mist of water was distributed onto a hydrophilic surface to represent conditions during a dew cycle or fog. Resuspension experiments were conducted on clean and dusty surfaces while they were wet and after drying. These resuspension results were directly compared to surfaces that had not been subjected to any surface water treatment to determine an absolute resuspension rate reduction ratio that could be treated as independent of resuspension technique. A minimum of a 3‐log reduction in resuspension was observed for dusty wet coupons and a maximum reduction of 4‐logs was observed after the clean coupons had dried. Water treatments have been demonstrated to inhibit spore resuspension under certain laboratory conditions while under an air‐generated shear stress similar in magnitude to shear forces generated by human interaction. This research has demonstrated that treating surfaces with water to inhibit spore resuspension could be a valuable tool in exposure minimization and remediation after a bioterrorism event.

Investigation on shear performance and prediction model of CFRP-ECC-concrete composite interface suffered from anodic polarization and environmental degradation

This study aims to investigate shear performance and prediction model of CFRP-ECC-concrete composite interface suffered from anodic polarization and environmental degradation. The effect of ECC mixtures, cathodic current densities, polarization period, and the duration of sulfate soaking and sulfate attacking by wet and dry cycles on the interface of the composite were studied. The results showed that three failure modes of CFRP-ECC-concrete composite interface were found. Shear load-slip curves showed double broken lines characteristics, while voltage-deterioration time curves showed an approximate linear increase relationship between voltage and polarization time. The five parameters all had significant effects shear strength deterioration on the CFRP-ECC-concrete composite interface. Moreover, this study proposed an innovative prediction model to the interfacial shear strength by the measured voltage, which can provide an important basic theory for ICCP-SS technology. This work makes a contribution to the ICCP-SS technology on the shear performance and prediction model of composite interface.

Исследование стойкости бетонов анизотропной и вариатропной структур к попеременному увлажнению и высушиванию

Objective: study of the influence of a number of operational factors on the final resistance of varitropic concrete to alternating cycles of wetting and drying. This work identifies the problem of concrete resistance to cyclic wetting and drying, and also formulates a scientific deficiency consisting in the inadequacy of the existing knowledge base regarding the relationship between the type of concrete structure and its resistance to cyclic influences, including alternating wetting and drying. Methods: test samples were made using three different technologies: vibration, centrifugation, and vibration centrifugation. The following main characteristics were studied: compressive strength, tensile strength in bending, water resistance. Experimental studies have shown that concretes with a varitropic structure (centrifugation and vibration centrifugation) have higher resistance to alternating wetting and drying than concretes with an anisotropic structure (vibration). After 500 cycles of wetting-drying and a high degree of aggressiveness of the saturated aqueous environment in terms of the content of sulfate, chloride and nitrate salts, the loss of compressive and tensile strength in bending for vibrated concrete was 28.7 and 32.7 respectively, for centrifuged concrete — 26.2 and 27.8%, respectively, and for vibrocentrifuged ones — 19.6 and 21.4 %, respectively. Results: Vibrocentrifuged varitropic concretes showed the greatest resistance to the effects of alternating wetting in an aqueous environment with varying degrees of aggressiveness and drying compared to centrifuged varitropic and vibrated anisotropic concretes.

Evaluation of the Performance of the ATESTA Forced Convection Dryer when Drying Pineapples

Objective: Evaluating the performance of the ATESTA [Solar Energy and Appropriate Technology Workshop] forced convection dryer, developed at the Albert Schweitzer Ecological Center of Burkina [CEAS Burkina], on the drying of pineapple slices in Togo. Method: For this purpose, two ATESTA dryers were setup in a company in Lomé, Togo, one operating in forced convection and the other, the witness, in natural convection mode. Drying tests of pineapple slices were carried out with these two dryers. Data were collected on water loss, organoleptic parameters and energy consumption during the drying process Findings: The results showed that the water loss rate increased by 11.4% as well as the first choice dry matter content by 36% and an energy saving of 21% percent of natural convection to forced convection. This performance of the ATESTA forced convection dryer increases the economic profit of USD [United States Dollar] 2.68/kg or USD 45.52/drying cycle and USD 2678.40/t of dried pineapples. The results of microbiological analyses revealed that the total flora [1.2.102 CFU/g] [Colony-Forming Unit per gram] yeast and mold [6.4.101 CFU/g] content of pineapple slices dried by the ATESTA forced convection dryer were in line with the limit values of the Directive 2000/13/EC [European Parliament and the Council]. Novelty: Performance tests on the forced convection dryer have made a more efficient dryer available to pineapple processors. Forced convection can also be adapted to existing dryers. Keywords: Performance, ATESTA dryer, Togo, Forced convection, Dried prineapple

Dynamic and Energy Consumption Characteristics of Sandstone Ring Specimens under Dry and Wet Cycling

The aim of this study was to examine the effects of sandstone ring specimens with different inner diameters on dynamic compression mechanical characteristics after dry and wet circulation. To carry out our study, we subjected a sandstone ring specimen with a 50 mm outer diameter and a 0~25 mm inner diameter to 10 cycles of dry and wet circulation. Afterward, we recorded the specimen’s basic physical parameters and used a split-Hopkinson pressure bar (SHPB) test device to perform an impact compression test. Following dry and wet circulation, our results showed that the mass loss rate increased and the volume expansion rates and density decreased with the increase in the inner diameter of the sandstone ring sample. Simultaneously, with the increase in the inner diameter of the specimen ring, the dynamic compressive strength of the specimen presented an exponential negative correlation, the dynamic elastic modulus presented a quadratic negative correlation, and the dynamic peak strain presented a quadratic positive correlation. Concurrently, the average particle size of the specimen decreased, and the degree of breakage increased with the increase in the sandstone sample’s inner diameter. Regarding the energy analysis performed in this study, the sandstone ring sample’s energy dissipation increased, and its kinetic performance evidently weakened with the increase in the ring sample’s inner diameter. The results of this study have certain reference values for the construction and maintenance of natural cavity rock and underground hard rock roadways.

Experimental study on the disintegration behavior and mechanism of red-bed mudstone in guangxi, China

Red-bed mudstone (RBM) has the characteristics of being easily softened and disintegrated under dry and wet cycles. To investigate the weakening and disintegration characteristics of the RBM, typical mudstone from Guangxi highway slope was taken as the research object in this study. Disintegration tests, water chemistry tests, and microscopic tests were performed to investigate the disintegration mechanism of this RBM. The results indicate that the RBM exhibits strong disintegration, releasing soluble salts such as potassium chloride and sulfates during the disintegration process. The hydrolysis of clay minerals is the main cause of changes in ion concentration in the solution. Throughout the dry and wet cycles, the proportion of macro-pores and meso-pores significantly increases, while the percentage of small and micro-pores gradually decreases. Under the influence of dry and wet cycles, the contact area between particles gradually decreases, transitioning from face-to-face contact to face-edge contact and finally to edge-to-edge contact. These research findings provide a basis for the stability analysis and prevention of landslide hazards in the red-bed soft rock areas.

Disintegration characteristics of sodic–saline loessial soil after freeze–thaw and wet–dry cycles

AbstractGeological hazards such as gully erosion, collapse and slope failure occur frequently in loess areas, which are closely related to the soil disintegration characteristics. Understanding the impact of freeze–thaw and wet–dry action on soil disintegration in the context of climate change is essential to establish effective soil and water conservation strategies and prevent engineering geological hazards in loess areas. In this study, sodic–saline loessial soils with different clay content were subjected to freeze–thaw and wet–dry cycles, followed by aggregate durability tests, direct shear tests and disintegration tests to investigate the effects of the two natural processes on soil disintegration characteristics. The results showed that the samples subjected to freeze–thaw cycles primarily exhibited rapid and stable disintegration, followed by slow disintegration, whereas the samples subjected to wet–dry cycles revealed weight gain, continuous slow disintegration and eventual sudden disintegration. Freeze–thaw action continuously deteriorated the disintegration resistance of soil, while wet–dry action improved the disintegration resistance of soil after the first cycle, and gradually weakened it in subsequent cycles. Statistical analysis showed that, for samples undergoing freeze–thaw cycles, the number of cycles and clay content were positively correlated with the disintegration rate, while the aggregate durability was negatively correlated with the disintegration rate. For samples undergoing wet–dry cycles, the number of cycles had a positive effect on the disintegration rate, while the clay content, shear strength and cohesion had a negative correlation with the disintegration rate. At a certain clay content, there was a positive correlation observed between the surface crack ratio, crack length and width with the disintegration rate of the wet–dry samples, while shear strength and cohesion had a negative correlation with the disintegration rate of both freeze–thaw and wet–dry samples. Furthermore, the study outlined the disintegration mechanism of loessial soils based on internal factors, driving factors, resistance factors and evolutionary factors. This study contributes to the in‐depth understanding of the catastrophic mechanism of geological hazards in cold and arid areas and provides experimental evidence for its control and management.

Hysteretic water-retention behaviour of unsaturated hydrophobised soils

Hydrophobised soils found in the superficial region of earthen infrastructure can affect the hydrological processes of these structures. The hysteretic water-retention curve (WRC), which governs these processes, for hydrophobised soils has rarely been reported. Existing apparatus is unable to measure the WRC of unsaturated soils as it could not control the condition of pore water pressure (uw) in excess of pore air pressure (ua) when the contact angle was larger than 90°. In this study, a new apparatus was created, which sandwiches a soil sample between a high water-entry value (WEV) membrane and a high air-entry value (AEV) ceramic disc, to control the uw < ua and uw > ua conditions. Contact angle hysteresis and menisci evolution in the test materials during wet–dry cycles were measured to interpret the WRC. The WEV of soil increased with decreasing chemical heterogeneity and particle size. When drying the hydrophobised soils, they could retain water before reaching a certain negative uw. The WEV identified from the second wetting cycle was lower than that from the first cycle, whereas the AEV remained largely unchanged. The WEV and AEV decreased when the particle size of the hydrophobised materials was increased, resulting in a smaller hysteresis size.

Stability of Expansive Soil Slopes under Wetting–Drying Cycles Based on the Discrete Element Method

The swelling-shrinkage behavior of expansive soils under climate changes will cause the crack development, which can be destructive of expansive soil slopes. This study investigated the effect of drying/wetting cycles on the stability of an expansive soil slope using the discrete element method (DEM), in consideration of the crack development induced by climate changes. The strength reduction method was adopted in the DEM calculations, which was coupled with the unsaturated seepage analysis given by the finite element method. The slope stability and the failure model of the slope after different times of wetting–drying cycles were analyzed, and the results were compared with those calculated by the limit equilibrium method and the finite element method. The results indicated that the failure pattern of the expansive soil slope was strongly influenced by the wetting–drying cycles. A shallow sliding surface of the expansive soil slope occurred after several wetting–drying cycles. Similarly, the safety factor of the expansive soil slope decreased gradually with the wetting–drying cycles. Considering the cracks’ evolution inside the expansive soil slope from the drying/wetting cycles, a shallower sliding surface with a smaller safety factor was obtained from the strength reduction method of the DEM, in comparison with the two conventional methods of the Limit equilibrium method and finite element method. Therefore, cracks play an essential role in the expansive soil slope stability. The strength reduction method of the DEM, which considers the cracks’ evolution during drying/wetting cycles, is more reliable.

High soil moisture rather than drying-rewetting cycles reduces the effectiveness of nitrification inhibitors in mitigating N2O emissions

Climate change has been intensifying soil drying and rewetting cycles, which can alter the soil microbiome structure and activity. Here we hypothesized that a soil drying-rewetting cycle enhances biodegradation and, hence, decreases the effectiveness of nitrification inhibitors (NIs). The effectiveness of DMPP (3,4-Dimethylpyrazole phosphate) and MP + TZ (3-Methylpyrazol and Triazol) was evaluated in 60-day incubation studies under a drying and rewetting cycle relative to constant low and high soil moisture conditions (40% and 80% water-holding capacity, WHC, respectively) in two different textured soils. The measurements included (i) daily and cumulative N2O-N emissions, (ii) soil NH4+-N and NO3−-N concentrations, and (iii) the composition of bacterial soil communities. Application of DMPP and MP + TZ reduced the overall N2O-N emissions under drying-rewetting (-45%), as well as under 40% WHC (-39%) and 80% WHC (-25%). DMPP retarded nitrification and decreased N2O-N release from the sandy and silt loam soils, while MP + TZ mitigated N2O-N production only from the silt loam soil. Unexpectedly, between days 30 and 60, N2O-N emissions from NI-treated soils increased by up to fivefold relative to the No-NI treatment in the silt loam soil at 80% WHC. Likewise, the relative abundance of the studied nitrifying bacteria indicated that the NIs had only short-term effectiveness in the silt loam soil. These results suggested that DMPP and MP + TZ might trigger high N2O-N release from fine-textured soil with constant high moisture after this short-term inhibitory effect. In conclusion, DMPP and MP + TZ effectively reduce N2O-N emissions under soil drying and rewetting.

The Effect of Wetting–Drying Cycles on the Deterioration of the Physical and Mechanical Properties of Cemented Paste Backfill in Open-Pit Coal Mines

To promote the sustainable exploitation of open-pit coal resources, waste is used as backfill material to realize the comprehensive utilization of solid waste mine resources. We proposed a mining method that is a combination of the highwall mining and filling mining methods. Cemented paste backfill (CPB) samples were prepared with high-clay-mineral-content marl particles as aggregate and normal Portland cement, sulfoaluminate cement and gypsum as cementing materials. The physical and mechanical properties and microstructural evolution of CPB with different binder ratios under wetting–drying cycles were measured. The results showed that the CPB with 0–3 wetting–drying cycles underwent shear and tensile coalescence, and that with 4–10 cycles underwent shear coalescence. The unconfined compressive strength (UCS) and elastic modulus (EM) decreased exponentially with increasing number of wetting–drying cycles but decreased exponentially and cubically with increasing porosity, respectively. The EM is more sensitive to gypsum content than the UCS. CPB deterioration was divided into an initial deterioration stage and a secondary deterioration stage. The evolution curve of the total damage variable presents an ‘S’ shape, with an initial damage stage, an accelerated damage expansion stage, a decelerated damage expansion stage and an end damage stage. The research results provide a basis for improving the recovery rate of resources under highwall conditions, and the extensive utilization of stripping materials, and promote the coordinated development of coal resource exploitation and environmental protection.

Experimental Study on Physical and Mechanical Properties of Lightweight Cellular Concrete Specimens Cast in Field and Laboratory

This paper presents a series of laboratory tests for evaluating the material properties of Lightweight cellular concrete (LCC) with different cement-to-fly ash ratios and at different ages. LCC specimens used in this study were cast in the field and/or laboratory. Large and small direct shear box tests were used to determine the shear strengths of LCC specimens. The test results show that the average wet densities for the LCC specimens cast in the laboratory ranged from 460 to 491 kg/m3, whereas the average wet densities for the specimens cast in the field ranged from 480 to 578 kg/m3 at the age of 28 days. The permeability values for the LCC specimens cast in the field ranged from 5.4 × 10-7 to 7.7 × 10-6 m/s and the permeability values for the LCC specimens cast in the laboratory ranged from 6.8 × 10-7 to 2.5 × 10-6 m/s. The measured peak friction angles of the LCC specimens from the small direct shear box tests ranged from 19° to 63°, whereas the measured peak friction angles of the LCC specimens from large direct shear box tests ranged from 23° to 79°. The average measured compressive strengths for the LCC specimens cast in the field and laboratory ranged from 0.43 to 1.15 MPa and 1.08 to 1.11 MPa at the age of 28 days, respectively. LCC specimens showed shrinkage behavior when subjected to wet–dry cycles and had good resistance to freeze–thaw cycles following ASTM D560/560M. The paper also compares the material properties of LCC measured in this study with those reported in the literature and the comparison shows good agreement overall.

Effect of Wet-Dry Cycling on the Microstructure of Various Weathering Grade Sandstone

This study investigated the effect of rock-water interaction on microstructural properties of various weathering grade sandstone. Sandstone samples were acquired from the Sor-Range coal mine area, Pakistan, and were investigated using a tabletop scanning electron microscope (SEM). The characteristics of microstructures from micrographs were obtained using ImageJ software. According to the findings an increase in wet and dry cycles significantly affects the microstructures (pore spaces and microcracks). The porosity and microcracks density of sandstone increases with the number of wet and dry cycles. Furthermore, the length of microcracks increases as the weathering grade increases. As variation in rock macroscopic mechanical characteristics is directly associated with the deterioration of microstructures. Therefore, analyzing the effect of water-rock interaction in various weathering grades of rock can offer a more accurate reference index for assessing the stability of geotechnical structures.

Improved mechanical response of Nano-SiO2 powder cemented soil under the coupling effect of dry and wet cycles and seawater corrosion

Improved mechanical response of Nano-SiO2 powder cemented soil under the coupling effect of dry and wet cycles and seawater corrosion

Experimental study on the effect of water-induced deterioration on shear properties of bolted rock joints

The investigation into the impact of dry and wet cycles as well as prolonged immersion on the shear properties of bolted rock joints can facilitate comprehension of the mechanism behind shear damage in anchorage rock slopes located within dam sites, which is crucial for conducting long-term stability analyses of such slopes and ensuring safe operation of hydropower plants. In this study, the sandstone from the Three Gorges reservoir area was collected and utilized to made into bolted rock joint specimens, which underwent 12 cycles of wetting and drying as well as 180 days of immersion before undergoing direct shear tests to investigate the degradation of their mechanical properties. The test results indicate that both treatments for water deterioration can significantly reduce the peak shear strength of bolted sandstone joints. The shear deformation characteristics of bolts also vary with the decrease in rock mass strength. As the number of wet and dry cycles, as well as immersion time, increases, the plastic hinge length of the bolt gradually extends. The surface roughness of the joint has an impact on the fracture mode of the bolt. In a flat joint, the fracture section of the bolt exhibits a certain inclination angle, indicating a damage mode where positive and shear stresses act in concert; whereas in a rough joint, the fracture section of the anchor rod shows almost zero inclination angle and is damaged under positive stress. Finally, an attempt was made to apply the conclusions of this paper to engineering by conducting a time-varying reliability analysis of the generalized anchored slope model. The results obtained have significant guidance for evaluating the long-term stability of anchored slopes in hydropower projects.

Plant mucilage increases pull‐out resistance of root analogues from soil

AbstractThe interface between plants' roots and soil is strongly affected by rhizodeposits, especially mucilage, that change mechanical and hydrological behaviour. In addition to impacts to aggregation, water capture and root penetration, rhizodeposits may also affect the pull‐out resistance of plant roots. Due to the complex architecture of plant roots and an inability to restrict rhizodeposit production, this study used a simplified system of wooden skewers to simulate roots and chia seed mucilage as a model to simulate rhizodeposit compounds. Pull‐out tests were then carried out to measure the impacts of mucilage, and one (WD1) or two (WD2) cycles of wetting and drying of soils. Using a mechanical test frame, the maximum pull‐out resistance (Fmax) and pull‐out displacement (dL) were recorded, allowing for pull‐out energy (E), average pull‐out force () and bond strength (τmax) to be calculated. The results showed that all pull‐out parameters of the samples with added rhizodeposit compounds tended to decrease between WD1 and WD2, but they were still significantly greater than without the added mucilage. The model rhizodeposit increased all pull‐out parameters by a minimum of 30%. With an additional wet–dry cycle, the mucilage tended to cause a decline in pull‐out parameters relative to a single wet‐dry cycle. This suggests mucilages could enhance the mechanical resistance of roots to pull‐out, but resistance decreases over time with cycles of wetting and drying. To conclude, an important role of mucilage is pull‐out resistance, which has relevance to plant anchorage and root reinforcement of soils.

Environmental Marine Degradation of PLA/Wood Composite as an Alternative Sustainable Boat Building Material

Abstract IIn this study, which can be considered a contribution to the global effort to produce sustainable materials and to search new manufacturing methods for the boat building industry, the performance of a 3D printable polylactic acid and recycled wood (PLAW) composite was investigated under the simulated operational conditions of a boat. The wood used in the composite was yellow pine (Pinus sylvestris), a local wood widely used in boat building and 8% by weight in the composite. For the study, tensile and compressive strength tests were performed in both atmospheric and post-aging conditions, using composite samples produced by the additive manufacturing method. The durations of the accelerated aging before the experiments were one, two and four weeks. During these aging periods, water spraying, a salty fog environment and a drying cycle were applied at elevated temperatures and at equal time intervals, daily. The effect of wood additive on the composite and the joining efficiency of the components were also examined with scanning and optical microscopes. The performance of the obtained composite and the effects of aging on performance were measured using two different thermal analyses: differential scanning calorimetry and thermogravimetric analysis. From the results obtained, it can be seen that PLAW composite can be used in the manufacture of structural elements subjected to relatively low loads in boats. It is an option that will provide integrity in the future interior design of wooden boats.

Analysis of the Mechanical Properties of Cured Sludge by Alkaline Excitation of Phosphogypsum

Engineering slag is a green building material that meets the requirements of contemporary sustainable development, and the solidification technology of residue is particularly important in the practical engineering of resource utilization and environmental protection. In order to reuse the waste soil and industrial waste and reduce the construction cost, the stabilization effect of adding different contents of calcium oxide, blast furnace slag and phosphogypsum to the waste soil of a township road reconstruction project was studied. The unconfined compressive strength test of calcium oxide further clarified the solidification mechanism of residual soil and helped us to obtain the optimal curing ratio. The dry and wet cycle test simulated the influence of temperature and humidity changes on the appearance, quality, strength and water resistance in actual engineering. The experimental results show that the unconfined compressive strength of the sample reaches 1.273 MPa after 7 days of curing when the mixture of 4% calcium oxide (ratio to 100% plain soil) and 16% blast furnace slag (ratio to 100% plain soil) is mixed. When the three materials were mixed, the unconfined compressive strength of 4% calcium oxide (the ratio of 35% phosphogypsum and 65% plain soil) and 16% blast furnace slag (the ratio of 35% phosphogypsum and 65% plain soil) reached 1.670 MPa and 3.107 MPa at 7 and 28 days, respectively. The curing age has a significant promoting effect on the stability of loess. The dry and wet cycle test results conclude that the specimens have good durability and stability. The results of microstructure analysis shows that a large number of ettringite and C-S-H gel were formed in the gelling system, which not only makes the original soil more stable, but also acts as a part of filling pores, and the two work together to support the soil and improve the strength.

Astronomically paced climate and carbon cycle feedbacks in the lead-up to the Late Devonian Kellwasser Crisis

Abstract. Repeated carbon isotope excursions and widespread organic-rich shale deposition mark the Middle and Upper Devonian series. Various explanations such as extensive volcanism and land plant evolution have been given for these perturbations and the general sensitivity of the Devonian oceans to the development of anoxia, but their repeated nature suggests that astronomical forcing may have controlled their timing. Here, a cyclostratigraphic study of the Kellwasser Crisis at the Frasnian–Famennian stage boundary (ca. 372 Ma) is carried out. The Kellwasser Crisis was one of the most ecologically impactful of the Devonian perturbations and is ranked among the “Big Five” Phanerozoic mass extinctions. The studied site is the Winsenberg roadcut section in the Rhenish Massif, Germany, which represents a quiet tropical shelf basin setting. Centimetre-scale elemental records, generated by portable X-ray scanning, allow for testing of the hypothesis that a 2.4 Myr eccentricity node preceded the Upper Kellwasser event. The study's results are supportive of this hypothesis. We find enhanced chemical weathering (K2O / Al2O3) during the period leading up to the Upper Kellwasser and a peak in distal detrital input (SiO2 / CaO) and riverine runoff (TiO2 / Al2O3) just prior to the start of the Upper Kellwasser event. We interpret this pattern as the long-term eccentricity minimum facilitating excessive regolith build-up in the absence of strong seasonal contrasts. The Earth's system coming out of this node would have rapidly intensified the hydrological cycle, causing these nutrient-rich regoliths to be eroded and washed away to the oceans, where they resulted in eutrophication and anoxia. An astronomical control on regional climate is observed beyond this single crisis. Wet–dry cycles were paced by 405 kyr eccentricity, with both the Lower and Upper Kellwasser events taking place during comparatively drier times. A precession-sensitive monsoonal climate system prevailed on shorter timescales. Intensification of this monsoonal system following the node may have caused the widespread regolith erosion. We estimate the total duration of the Kellwasser Crisis at ca. 900 kyr, with the individual events lasting for ca. 250 and 100 kyr, respectively. If astronomical control indeed operated via regolith development in monsoonal climates, then land plants may have played an important role. This would not have been through evolutionary steps directly triggering Kellwasser perturbations but by gradually strengthening the climatic response to orbital forcing via soil development – creating soils thick enough to meaningfully respond to orbital forcing – and intensifying the hydrological cycle.

Experimental study on damage of slope under drying and wetting cycle based on DC electric method.

In order to investigate the seepage law and crack development characteristics of dump slopes, as well as the impact on slope stability during drying and wetting cycles, a simulation test slope system was constructed in a rainfall environment, specifically designed to mimic the engineering conditions of dump slope. The apparent resistivity response formula for the seepage and crack development processes was derived based on the three-phase medium theory of rock-soil bodies and Maxwell's conductivity formula. The geoelectric field characteristics pertaining to slope damage and the corresponding patterns of alteration were comprehensively investigated. The results demonstrate a negative correlation between resistivity and slope water content, with resistivity increasing as cracks develop and decreasing with water infiltration. The progression of crack formation in a rainfall environment on a dump slope can be categorized into three stages: The initial phase involves the saturation of the slope as water content increases. Subsequently, the second phase entails the initiation and expansion of capillary zones, along with the formation of dominant waterways. Lastly, the third phase encompasses the formation and expansion of cracks within the dumping site. The occurrence of sudden changes and abnormal fluctuations in apparent resistivity within a saturated slope signifies the presence of cracks and weak surfaces, leading to gradual and irreversible damage. This phenomenon serves as an indicator of slope damage and can be utilized for the early prediction of slope instability.