Logarithmic Relationship Research Articles

Assessing Asphalt Pavement Pre-Compaction with Paver Screed Frequency Measurements

The quality and longevity of an asphalt road depends on the accurate compaction of the asphalt pavement. Particular emphasis should be placed on the pre-compaction process involving the paver’s screed. Inadequate or excessive pre-compaction can result in paving errors and inhomogeneities within the pavement, which even expert roller operation cannot rectify. In practical paving, however, the degree of pre-compaction is rarely determined, so that one is dependent on the empirical knowledge and assessments of the paving personnel. Within the context of the research initiative, InfraROB (Grant Agreement No.: 955337), an innovative system was devised to infer the extent of pre-compaction by leveraging the resonance frequency of the paver’s screed. This system comprises a rugged, enclosed acceleration sensor capable of capturing high-speed accelerations and a Wi-Fi-enabled control unit for data storage and processing. To validate this system, a series of test pavements were constructed using an asphalt binder mix (AC 16 BS), deliberately varying the speed of the tamper compaction unit in four steps from 0 rpm up to 1500 rpm. Half of the test lanes were longitudinally compacted with rollers, allowing for the examination of the asphalt pavement in its partially pre-compacted state. To achieve this, drill cores were extracted, and their density was assessed in the laboratory. Through the application of Fast Fourier Transformation, the measured resonance frequency data was analysed and subsequently correlated with the outcomes of the drill core inspections. This analysis revealed a strong logarithmic relationship between the average peak acceleration and the bulk densities measured, with a high coefficient of determination exceeding 0.9. The presented method enables real-time assessment of the pre-compaction status of asphalt pavement, offering support to paving personnel, optimising roller usage, and enhancing asphalt pavement quality.

Measurements and Simulation of Compressive Behavior of Biodegradable Seedling Containers

Highlights Compression tests were conducted on biodegradable containers with various conditions. The lateral loading reduced the compressive strength compared with the vertical loading. A model was developed using FEA to simulate the compressive behavior of the biocontainer. Model results showed similar ductile behaviors of the biocontainers with test results. The compressive strengths of wet biocontainers were below 20% of dry ones. Abstract. Biodegradable seedling containers (biocontainers) are becoming increasingly popular for use in transplanting and greenhouse applications. However, biocontainers have reduced mechanical strength when compared to plastic containers, often being damaged during the handling process. In this study, Canadian peat moss biocontainers were tested to study their compressive properties under different scenarios of various container sizes (small and large), moisture conditions (dry and wet), and orientation (vertical and lateral) relative to the loading direction. Also, simulations were performed using the Finite Element Analysis (FEA) for the selected scenario, focusing on the small container with two moisture conditions. The testing results showed that the force-displacement behavior of biocontainers varied dramatically with the orientation. In the lateral orientation, the biocontainers were able to carry loads while being largely deformed. However, the lateral orientation resulted in a reduced compressive strength of 21% compared with the vertical orientation. The moisture condition was found to be the second most dominant factor affecting the result. The compressive strength of the wet biocontainer was only 15.4%-19.6% of the dry ones. FEA simulation results showed similar ductile behaviors of the biocontainers under compression. Compared with the testing results, the relative errors of the simulated compressive strengths were 24.0% for the small, dry container and 9.89% for the small, wet one. FEA simulations were conducted with various Young’s Modulus values, revealing a logarithmic relationship with the container strength and deformation. The obtained knowledge of how the biocontainers react when subjected to compression provides insight to the failure mechanism of the container. The information is valuable for guiding the proper handling of biocontainers. Keywords: Biocontainer, Compression, FEA, Moisture condition, Property.

Basal heave stability analysis of excavations considering the soil strength increasing with depth

The failure mechanism and sliding surface are significant for calculating the safety factor of deep excavations. In this study, the discontinuous layout optimization (DLO) method is used to investigate the influence of the increase in soil strength with depth and the width of the excavation on the basal heave failure mechanism. First, the DLO results show that with the soil strength increasing linearly with depth, the sliding surface extension downward is limited. The sliding surface is located below the toe of the retaining structure when the embedded ratio D/H is small, which is different from the traditional assumption. The logarithmic relationship between the normalized sliding radius R/(D + h) and the embedded ratio D/H is obtained. This relationship provides a reference for determining the size of the sliding surface and solving the problem that the safety factor decreases as the embedded ratio increases in Shanghai’s local code. Furthermore, the safety factor Fs first decreases and then gradually becomes stable as the width-to-depth ratio B/H increases. When Fs reaches a stable value, B/H is taken as the critical width-to-depth ratio (B/H)s to classify the wide and narrow excavations, and the linear relationship between (B/H)s and D/H is given.

Reasonable top coal thickness for large cross-section open-off cut in lower-layer mining

The thickness of top coal is the main factor affecting the stability of the large cross section open-off cut under the goaf. The 1-2 lower 203 cross section open-off cut of the Huojitu Coal Mine was used as the background to investigate the top coal rational thickness of the large cross section open-off cut under the goaf in slicing mining. The top coal above the cut was simplified into a beam model to calculate its plastic zone range with the elastoplastic theory under the influence of the upper slicing mining and the lower slicing cut excavating. The deformation law of the top coal of the large cross section open-off cut under different top coal thicknesses was studied with both a simulation experiment and numerical simulation. The displacement, stress, and top coal structure of the surrounding rock of the cut were observed in situ using several observation methods. The results show that the plastic zone of the floor in the upper slicing face and the influence of the cut excavation are 2.02 m and 1.43 m, and the maximum plastic zone of the top coal is 3.45 m. A top coal thickness of more than 3.45 m is conducive to maintaining the stability of the large cross section open-off cut. The top coal of the cut can be divided into the roof-fall hazard zone and roof-fall warning zone according to the results monitored by distributed optical fiber. When the top coal thickness is 3.0 m, 3.5 m, and 4.0 m, the deformation law changes from an exponential deformation to a linear and then to a logarithmic relationship in the roof-fall hazard zone and from a linear to a logarithmic relationship in the roof-fall warning zone. When the thickness of top coal is 3.5 m and 4.0 m, the subsidence trend of the top coal visibly decreases, and the subsidence is only 56% and 39% of the subsidence of that of a thickness of 3 m. The deformation law of top coal measured using the DIC (Digital Image Correlation, DIC) is consistent with that of distributed optical fiber. The average thickness of the top coal reserved in the 1-2 lower 203 large cross section open-off cut is 4.0 m. The maximum surface subsidence of the top coal cut hole is 12 mm in the field monitoring. The maximum internal subsidence is 6 mm, and the maximum shed beam strain is –416 με. The deformation of the top coal is slight, indicating that the top coal thickness of 3.5–4.0 m is reasonable.

Assessment of Morphometric and Hypsometric Analysis of the Ruste Basin Using Remote Sensing and Geographical Information System Techniques

A basin’s characteristics and features need to be comprehended completely by conducting morphometric analysis, such as evaluating the basin’s size, form, and surface features, to estimate floods and erosion rates properly. The main objective of this investigation is to evaluate morphometric measures and hypsometric analysis of Erbil’s Ruste Basin employing remote sensing and geographical information system methods. To investigate the significant tributaries of the selected area, the hydrology tool within the Spatial Analysis Tools of ArcGIS, version 10.7, was utilized to define the basin boundaries, map the drainage networks, and obtain topographic data. The findings of the linear morphometric parameters revealed that the logarithmic relationship between stream orders and stream numbers was negative. The difference in stream order and number seen in the watershed is due to topography and bedrock influence. The results also showed a negative correlation between stream length and stream order, and a coefficient of determination of 0.972, which indicates that the basin is made of low-permeability formation and subsoil materials. Considering the areal morphometric parameters, the circularity ratio, elongation ratio, and form factor are 0.594, 0.853 and 0.572, respectively, suggested a semi-circular shape. A drainage density value of 2.259 km-1 showed that the Ruste Basin is a basin with steeply to very steeply sloping hilly terrain with varying plant covering. Furthermore, the Ruste Basin has high relief and slope with a relief ratio of 0.151 and basin relief of 2.576 km, both of which imply that it has a steep slope with high erosive force, limited infiltration, and a high runoff rate. Ruste Basin’s ruggedness number was 5.819, indicating that it has badlands topography. The average hypsometric integral was 0.467, denoting a mature basin featuring S-shaped hypsometric curves. In conclusion, the results showed that analysis of morphometric parameters and hypsometric integral and curve provides us with a notion to basin characterization and guidance to making appropriate decisions to establish effective actions to sustainable water and soil conservation and natural resources management through applying water harvesting methods, check dams, and bench terraces.

Numerical simulation of fluid flow and heat transfer in steady state laminar natural convection in horizontal circular cylindrical enclosures

Heat transfer by natural convection often occurs in a closed enclosure in various applications. Different geometries of the cross section of a two-dimensional enclosure, such as triangle, rectangle, and trapezoid have already been investigated. In this research, a regular polygon with twelve sides is considered. The study focuses on the rate of heat transfer through the enclosure, using one side of the polygon as the hot surface and another side as the cold surface. The dodecagon can serve as a model for circular cylindrical enclosures under constant temperature boundary conditions over a specified length. The Nusselt number of the enclosure is obtained for each side as the hot surface. Both the lowest and highest Nusselt numbers are evaluated based on the position of the cold side. The findings reveal that the highest Nusselt number does not necessarily correspond to configurations where the hot and cold sides are directly opposite each other. In situations where convection heat transfer through the enclosure is the predominant mode of heat transfer, the Nusselt number is a power function of the Rayleigh number. Conversely, a logarithmic relationship is observed in cases of conduction heat transfer within the enclosure.

Synthesis of Guanine/Vermiculite Two-Dimensional Nanocomposites for Wireless Humidity Sensing in Nut Storage Environment.

Two-dimensional (2D) nanostructures have the advantages of high specific surface area, easy surface functionalization, abundant active sites, and good compatibility with device integration and can be assembled into three-dimensional structures, which are key to the development of high-performance gas sensors. In this study, 2D vermiculite (VMT) nanosheets and guanine (G), two renewable resources with unique chemical structures, were organically combined to fully use the specificity of their molecular structures and functional activities. Driven by the regulation of 2D VMT nanosheets, guanine/vermiculite (G/VMT)-based 2D nanocomposites with controllable pore structure, multiple binding sites, and unobstructed mass transfer were designed and synthesized. The G/VMT nanocomposite material was used as a quartz crystal microbalance (QCM) electrode-sensitive film material to build a QCM-based humidity sensor. G/VMT-based QCM humidity sensor had good logarithmic linear relation (0.9971), high sensitivity (24.49 Hz/% relative humidity), low hysteresis (1.75% RH), fast response/recovery time (39/6 s), and good stability. Furthermore, with a QCM sensor and a specially designed wireless circuit, a wireless humidity detection system transmitting via Wi-Fi allows real-time monitoring of nut storage. This study presents an environmentally friendly, high-performance, miniature 2D nanocomposite sensor strategy for real-time monitoring.

Seepage Characteristics of Shale Fracture and the Effect of Filling Sand under Normal Stress

As a new type of unconventional natural gas resource, shale gas plays a vital role in energy supply. In order to deeply understand the shale fracture seepage characteristics, filled and unfilled fracture seepage tests were carried out on shale samples with different fracture surface topography with the use of self-developed shale fracture seepage testing equipment. The fitting formula that the seepage discharge decreased as a negative exponential function with the increase in normal stress was obtained in the unfilled fracture seepage test; the fitting coefficient had a good logarithmic and exponential function relationship with joint roughness coefficient JRC and surface development interface area ratio Sdr. Meanwhile, the modified cubic law was obtained by adding the correction coefficient. The correction coefficient had an exponential relationship with the anisotropy value Ka. Compared with the unfilled one, the fracture surface topography had little effect on the seepage discharge when it was filled. The experimental results show the effects of water head difference, fracture surface topography, particle size, and thickness of filling sand on shale fracture seepage characteristics under different normal stress conditions, which have a certain significance for improving the efficiency of shale gas production.

Heat release rate prediction for high-altitude gasoline pool fires based on field tests of combustion characteristics

The heat release rate is of great significance for fire protection design, whether in highway tunnel, building, oil depot and aircraft. Simply, the heat release rate can be estimated by multiplying the mass loss rate by the effective heat of combustion, which can be investigated via pool fire test, because of its wide applicability in various fire scenarios. In fact, both mass loss rate and effective heat of combustion are affected by the high-altitude environment, including the low atmospheric pressure and low ambient temperature. Thus, to obtain the mass loss rate and effective heat of combustion, field tests of gasoline pool fire were conducted at 4 altitudes. The test environments of 4 altitudes were consistent with that of real fires at high altitudes, especially the atmospheric pressure and ambient temperature, to ensure that the measuring data were correct. The heat release rate at high altitudes were calculated by using the fitting formulas of mass loss rate and effective heat of combustion, which were presented in this paper. The results revealed the following: (1) Both the atmospheric pressure and ambient temperature were important factors for the mass loss rate and effective heat of combustion. (2) Based on a global model and flame temperature correlation, a mass loss rate estimation method was established. After analysis, a linear relationship between lnm˙ and lnP∞ was identified for temperature greater than 0 °C, otherwise, there was a logarithmic relationship between lnm˙ and lnP∞. In addition, the fitting formula of mass loss rate was obtained. (3) A theoretical method of effective heat of combustion based on the Gibbs energy minimization approach was established. For simplification, the effects of atmospheric pressure and ambient temperature were approximately independent. The effective heat of combustion increased linearly with both atmospheric pressure and ambient temperature, and the fitting formula was gained by considering above two factors. (4) The heat release rates of gasoline pool fire at high altitudes were calculated, which varied with ambient temperature as the Gaussian function. And the relationship between heat release rate and atmospheric pressure was power function. The atmospheric pressure effect on heat release rate was more significant at temperatures lower than 10 °C. The results in this work could provide a basis for heat release rate prediction studies and subsequent research on smoke diffusion, whether in aircraft, highway tunnel, building and oil depot at high altitudes.

Large-Strain Nonlinear Consolidation of Sand-Drained Foundations Considering Vacuum Preloading and the Variation in Radial Permeability Coefficient

The vacuum preloading method effectively strengthens soft soil foundations with vertical drainage, which produces a smear effect when laying sand drains. Meanwhile, the seepage of pore water and soil deformation during consolidation exhibit nonlinear characteristics. Therefore, based on Gibson’s 1D large-strain consolidation theory, this paper developed a more generalized large-strain radical consolidation model of sand-drained soft foundations under free-strain assumptions. In this system, the double logarithmic compression permeability relationships for soft soils with large-strain properties, the variation in the radical permeability coefficient in the smear zone, and the effect of the non-Darcy flow were all included. Then, the partial differential control equations were numerically solved by the finite difference method and validated with existing radical consolidation test results and derived analytical solutions. Finally, the influences of relevant model parameters on consolidation are discussed. The analysis shows that the greater the maximum dimensionless vacuum negative pressure P0, the faster the consolidation rate of sand-drained foundations. Meanwhile, the decrease in the negative pressure transfer coefficient k1 will result in a decreasing final settlement amount. Moreover, the consolidation rate of sand-drained foundations is slower considering the non-Darcy flow, but the final settlement is unaffected.

Soil organic carbon stocks increased across the tide-induced salinity transect in restored mangrove region

AbstractBlue carbon in mangrove ecosystems contributes significantly to the global carbon cycle. However, large uncertainties maintain in the soil organic carbon (SOC) storage throughout the tide-induced salinity and alkalinity transect in the mangrove restoration region in Southern China. Total 125 soil samples were obtained to detect the SOC content and physicochemical properties. The mean SOC content of each layer ranged from 6.82 to 7.86 g kg−1, while the SOC density ranged from 2.99 to 11.41 kg m−2, increasing with soil depths. From different land covers in the study region, the SOC content varied from 4.63 to 9.71 g kg−1, increasing across the salinity and alkalinity transect, while the SOC density fluctuated from 3.01 kg m−2 in mudflats to 10.05 kg m−2 in mangrove forests. SOC concentration was favorably linked with total nitrogen (r = 0.95), and total phosphorus (r = 0.74), and negatively correlated with Cl− (r = − 0.95), electrical conductivity (r = − 0.24), and total dissolved solids (r = − 0.08). There were significant logarithmic relationships between SOC content and the concentrations of clay (r = 0.76), fine silt (r = 0.81), medium silt (r = − 0.82), and coarse silt (r = − 0.78). The spatial patterns of SOC concentration were notably affected by soil texture, physicochemical properties, and land-cover type, providing essential reference for future investigations of blue carbon budget in restored mangrove forests.

Identification of Critical Urban Clusters for Placating Urban Heat Island Effects over Fast-Growing Tropical City Regions: Estimating the Contribution of Different City Sizes in Escalating UHI Intensity

The incessant rise of artificial surfaces has increased the temperatures of cities, distressing urban health and sustainability. Fast-growing tropical cities particularly call for an understanding of this phenomenon, known as the urban heat island (UHI). The present study was conducted to detect UHI dynamics over the National Capital Region of India. Stretching over more than 32 000 km2, this region consists of urban centers of varying sizes. Landsat thermal bands were processed to extract temperature patterns between 1999 and 2019. Urban climate change was prominent, as a 2349-km2 expansion in UHI area was spotted. Urban clusters of different sizes were demarcated by applying the k-nearest neighbor algorithm on the normalized difference building index maps. This empirical analysis helped to form a logarithmic relation between city size and UHI intensity. Observed results set a framework to assess the thermal environment of numerous urban centers from any tropical country. UHI intensity values for various city sizes were computed, as they were crucial to decide the outdoor comfort zones based on the base temperature conditions of other cities. Further, the critical zones in each urban cluster were identified using the vegetation index, and scopes of landscaping were suggested based on the observed building morphologies of different local climate zones.

Topographical characterization and permeability correlation of steel fiber reinforced concrete surface under freeze-thaw cycles and NaCl solution immersion

This study investigates the relationship between the surface topography of steel fiber reinforced concrete (SFRC) and both the freeze-thaw damage and permeability of the concrete matrix subjected to freeze-thaw cycles and immersion in a sodium chloride solution. Rapid freeze-thaw tests were conducted on concrete immersed in NaCl solution to introduce freeze-thaw damage. A custom-developed 3D laser-scanning device was employed to capture the surface topography information of concrete subjected to freeze-thaw cycles. Multivariate analysis was utilized to determine the suitable parameter for evaluating the roughness of the concrete surface. A correlation analysis was carried out between the surface topography of concrete and the freeze-thaw damage parameters, including mass loss (ΔWn), relative dynamic modulus of elasticity (RDME), and ultrasonic pulse velocity (Uv). A custom-designed vacuum permeability device was used to measure the permeability of concrete matrix. The relationship between the surface topography and permeability of concrete subjected to freeze-thaw damage is studied. The results show that the steel fibers significantly reduce the freeze-thaw damage and surface roughness of concrete subjected to freeze-thaw damage in the sodium chloride solution. Roughness number (RN) is the most representative parameter for evaluating the topographical characterization of concrete surface and can be used to quantify the surface topography of concrete exposed to freeze-thaw cycles. The absolute values of correlation coefficient between RN and its ΔWn, RDME, and Uv reach up to 0.89, which suggests that RN can indirectly evaluate the freeze-thaw damage of concrete. Furthermore, there exists a logarithmic relationship between RN and the permeability of the concrete matrix, with the correlation coefficient R2 exceeding 0.86. This relationship can be utilized to quickly estimate its permeability based on the surface roughness of SFRC exposed in cold coastal regions.

Water-Yield Relationships of Potato in Mediterranean Climatic Conditions

This study was carried out in Isparta University of Applied Sciences, Faculty of Agriculture, Agricultural Research, and Application Farm in 2021 to determine the effect of different irrigation water levels on tuber yield and quality parameters of the Agria potato variety. Drip irrigation method was used in the study and five different irrigation water levels (S1: 120% of the seven-day ETo, S2: 90% of the seven-day ETo, S3: 60% of the seven-day ETo, S4: 30% of the seven-day ETo, S5: No irrigation except germination and emergence) were determined based on the reference evapotranspiration (ETo). Irrigation water (IW) amounts varied between 85.66-639.26 mm and evapotranspiration varied between 296.54-825.15 mm. Different amounts of IW significantly affected the vegetative growth, yield and quality parameters of potato. As irrigation water decreased, total tuber yield and marketable yield declined. Total tuber yield and marketable yield were 46.11 t/ha and 40.59 t/ha, respectively, in S1 treatment where the maximum amount of IW was applied, while they were 12.96 t/ha and 6.37 t/ha, respectively, in S5 treatment where no irrigation was applied. Logarithmic relationships were determined between evapotranspiration and total yield and between the amount of IW and total yield. Water use efficiency was determined between 43.69-55.88 kg/(ha×mm) and irrigation water use efficiency between 32.34-51.86 kg/(ha×mm) and yield response factor (ky) was calculated as 1.19.

Effect of polyvinyl alcohol powder on the impermeability, frost resistance and pore structure of calcium sulfoaluminate cement concrete

The pore structure has close tie with the performances of concrete, especially the impermeability and frost resistance. In this paper, Polyvinyl alcohol (PVA) powder was added into calcium sulfoaluminate cement (CSA) concrete to improve the pore structure. The effect of PVA on the impermeability, frost resistance and pore structure of CSA concrete were studied, and the relationship between impermeability and pore structure was revealed. The results show that PVA significantly improves the impermeability and frost resistance of CSA concrete. The seepage height reduces from 3.06 mm to 1.43 mm, the relative permeability coefficient reduces from 4.82 × 10-6 mm·h−1 to 1.05 × 10-6 mm·h−1, and the frost resistance increases from F100 to F150. PVA can reduce the porosity of CSA concrete, and the critical pore size and pore connectivity also gradually decrease, while the fractal dimension gradually increases. The relative permeability coefficient of CSA concrete has a good linear relationship with porosity and capillary porosity, an exponential relationship with critical pore size, a negative linear relationship with fractal dimension, and a logarithmic relationship with pore connectivity. Therefore, the addition of PVA reduces the porosity of CSA concrete and improves the impermeability and frost resistance.

Reaction induced conformational change in polyindole: Polyindole/PVA film as biomimetic sensors of temperature and electrical energetic condition.

The influence of surrounding temperature and electrical energetic condition on the conformational movements (cooperative actuation) of polyindole is verified using a polyindole-coated polyvinyl alcohol (PIN/PVA) film. Chronopotentiometric studies revealsthat the consumed electrical energy during the reaction varies linearly with the change in working temperature. The influence of temperature on the reversible conformational movements of the polymer chain is related to the charge consumed during the reaction. The logarithmic dependence of reversible redox charge obtained from coulovoltammogram with inverse of temperature further proved the temperature sensing characteristics and the influence of temperature on the cooperative actuation of the PIN/PVA film. The conformational relaxation increases as the temperature increases through hosting higher number of counter anions with the solvent molecule. The extension of the redox reaction or charge consumption was found to decrease as the scan rate increases. The double logarithmic relation between the consumed redox charge and the scan rate has proved that the electrical energetic condition can influence the conformational movement or the extension of the redox reaction in a reversible manner. The results suggest that the PIN/PVA film can act as a biomimetic macro molecular sensor of working temperature and electrical energetic condition as biological muscles do.

Threshold-like effect of soil NO3− concentrations on denitrification product N2O/(N2O+N2) ratio is mediated by soil pH

The interactive effects of soil pH and nitrate (NO3−) availability on denitrification-derived nitrous oxide (N2O) and dinitrogen (N2) emissions, as well as N2O/(N2O + N2) product ratio (N2Oi) remain difficult to evaluate. Here, we consecutively monitored denitrification-derived N2O and N2 emissions with different soil pH and NO3− concentrations by using the artificial 15N gas flux method in combination with a global meta-analysis of 458 observations to illustrate the interactive effects of soil pH and NO3− availability on N2Oi. Isotopic data indicated that pH adjustment through liming significantly and nonlinearly reduced N2Oi and increased cumulative N2 emissions. Liming decreased cumulative N2O emissions by approximately threefold in low NO3− treatments (p < 0.01), while at high NO3− treatments liming showed no effect. The meta-analysis revealed a logarithmic relationship between N2Oi and increasing soil NO3− concentrations across different soil pH levels, indicating a threshold-like effect of NO3− concentrations on the reduction of N2O during denitrification. The threshold NO3− concentration tends to raise with increasing soil pH. Hence, there were significant interaction effects of soil pH and soil NO3− concentration on the N2Oi value. The present study emphasizes the need to consider soil pH and NO3− concentration interaction effects on denitrification for proposing the effective mitigation practices of denitrification-derived soil N2O emissions.

An insight into the effect of primary hidden microfissures on mechanical behaviors and failure characteristics of brittle basalt

The anisotropy of mechanical properties of hard rocks is usually affected by the internal primary hidden microfissure structures, which tend to induce secondary rock fracture propagation even surrounding rock instabilities in deep underground excavation. This research attempts to reveal the control effect of primary hidden microfissures on the mechanical behaviors and failure characteristics of cryptocrystalline basalt with hidden microfissures (CBWHM) through a series of laboratory tests. Firstly, a geometric feature extraction method for primary hidden microfissures of basalt rock has been proposed, by which 20 groups of three-dimensional (3D) visualization models of cylindrical basalt samples were established, and the distribution location and volume crack rate (KV) of hidden microfissures were simultaneously determined. On this basis, a series of the uniaxial compression tests of basalt samples with synchronous acoustic emission (AE) were carried out. Results show that the location and development degree of primary hidden microfissures significantly control the mechanical characteristics of basalt, with the relevant micro-fracture events occurring earlier and throughout the whole loading process compared with intact samples. In general, there exists a uniaxial polynomial fitting relationship between the strength of basalt samples and KV. The larger the KV, the lower the peak strength (σc) of basalt, which could decrease by 30–50% compared to that of the intact rock when KV is more than 5‰. However, when the hidden microfissures with large dip angles are located close to the central axis, the influence of KV on the rock strength becomes less, but the crack propagation and failure morphology are still obviously controlled by the hidden microfissures. The statistical analysis results of surface cracks and rock fragment characteristics of the damaged basalt samples further show that the basalt rock is easy to expand, penetrate and eventually fail along the hidden microfissures under loading, and it is tensile fracture that controls the failure of CBWHM. With an increase of KV, the mass percentage (W) of the coarse particle of the sample fragments increases gradually, and the fractal dimension (D) of the rock fragments and KV of the hidden microfisures show an obvious logarithmic curve relationship. The research could provide effective guidance for the interpretation of the meso-mechanism of hard rock failures.

Energetic impact of reconstructed debris flow on the intensity and duration of growth disturbances in tree rings

A rare study on the quantitative relationship between the energetic impact of debris flows on the intensity and duration of growth disturbances of tree rings was carried out, partly due to a lack of feasible approaches and detailed field evidence. In this study, we first used a dendrogeomorphic technique to determine the age of a recent debris flow derived from historic landslide deposits at Qingyang Mountain (QYM) on the northeastern Tibet plateau. We acquired the quantitative data on the annual widths of tree rings in history and confirmed the influence of the debris flow rather than other factors (e.g., climatic events and inset outbreaking) in disturbing the growth of tree rings in a specific year. Using this approach, we determined that the age of the debris flow at QYM occurred in 1982, which was speculated to be triggered by the high monthly precipitation registered during July 1982. Subsequently, based on the boundaries of historic debris flow identified on remote sensing images before and after 1982 and the depth-integrated continuum model, we reconstructed the process of the 1982 debris flow and obtained the kinematic energy of the debris flow impacting the sampled trees. Based on the study, we observed that two growth disturbance patterns of tree rings influenced by the reconstructed 1982 debris flow were revealed, including growth suppression and asymmetric growth. We obtained a raw logarithm relationship between duration (i.e., lasting time for the disturbed tree rings to recover the initial width) and intensity of growth disturbances (i.e., growth suppression ratio of disturbed tree rings). We concluded that there is a negative exponential relationship between the simulated kinematic energy of debris flow impacting the disturbed trees and the time to recover the initial width of corresponding tree rings.

Effect of different loading rates on the fracture behavior of FRP‐reinforced concrete

AbstractIn order to study the effect of different loading rates on the fracture behavior of fiber‐reinforced polymer (FRP) reinforced concrete, the fracture experiments of FRP‐reinforced concrete beams under different loading rates were carried out. The calculation method of fracture toughness was given by analytic deduction, and the effects of different loading rates on the fracture parameters were analyzed. The experimental results show that there are three critical points in the fracture process of FRP‐reinforced concrete beam, which are the crack initiation load, crack resistance load, and ultimate load points. The effective crack length at the crack resistance load point increases with the increase of loading rate, and the effective crack length at the ultimate load point does not vary as the loading rate. With the increase of loading rate, the elastic modulus and fracture toughness increase gradually, and there is a logarithmic relationship with the loading rate, which has obvious rate correlation. The fracture process zone (FPZ) length of FRP‐reinforced concrete beams gradually decreases with the increase of loading rate.