Search Results (68)

To investigate the evolution trend of the extraction zone above the drawbell in block caving, an experimental apparatus incorporating the drawbell structure was designed. Ore drawing experiments were conducted using materials with varying particle size gradations. The results demonstrate that the extraction zones for all three gradations exhibit an ellipsoidal shape in the vertical direction, with elliptical cross-sections. As the draw height increases, both the major and minor axes of the extraction zone’s maximum cross-section continuously enlarge, stabilizing beyond a draw height of 80 cm. The ore fragment size significantly influences the extraction zone dimensions. Gradation I, characterized by the smallest average particle size, yielded the largest extraction zone, whereas Gradation III, with the largest average particle size, resulted in the smallest. Numerical simulations of ore drawing for the different particle sizes were performed using PFC3D. The extent of the extraction zone in the numerical results was determined by reconstructing the initial positions of the drawn particles. The simulations show good agreement with the experimental findings, particularly regarding how the major and minor axes of the extraction zone cross-section vary with increasing draw height. Moreover, the simulations confirm that smaller average particle sizes enhance particle flowability, leading to larger extraction zones, as anticipated. Full article

The stability of bottom structures in block caving mines is significantly challenged by impact loads generated from large rockfalls and ore collapses on slopes. This study aims to investigate the mechanical response and failure characteristics of bottom structures under such dynamic and cyclic loading conditions. Discrete element methods (DEMs) were employed to simulate the impact load amplitudes caused by large rockfalls on bottom structures. Specimens with identical mechanical properties to the bottom structure were fabricated at a 1:100 scale, based on the principle of similarity ratio tests. Three distinct types of impact loads were identified and analyzed: overall impact from large-scale slope collapses, localized impact from partial rock and soil mass collapses, and continuous multiple impacts from progressive slope failures. True triaxial tests were conducted to evaluate the mechanical response of the bottom structure under these loading scenarios. The results indicate that while overall and multiple impact loads from slope collapses do not lead to catastrophic failure of the bottom structure, severe damage occurs under a 100 m thickness of ore and large block impacts. Specifically, the inner walls of ore accumulation troughs peel off, and ore pillars between troughs fracture and fail. This study highlights the need for advanced experimental and numerical approaches to accurately predict the stability and failure modes of bottom structures under complex loading conditions. Full article

When the distribution characteristics of rock particles are unknown, obtaining reasonable particle size parameters through trial-and-error methods is time-consuming. Therefore, identifying a set of particle size parameters that can accurately reflect the macro-mechanical properties of rock is crucial. In this study, a series of uniaxial compression and direct shear tests were conducted on standard rock models with varying particle sizes and particle size ratios using the discrete element method (DEM). The results indicate that the uniaxial compressive strength, elastic modulus, and shear stiffness increase with decreasing particle size. Conversely, the uniaxial compressive strength, elastic modulus, and shear stiffness decrease as the particle size ratio increases. Based on the simulation results, the accuracy and reliability of numerical simulations can be ensured when the relative average particle size exceeds 50 and the particle size ratio is greater than 1.5. These findings can be applied to other similar numerical studies, thereby reducing the time required for parameter matching and enhancing the efficiency of scientific research. Full article

The Nevados de Chillán Volcanic Complex is one of the most active of the Southern Volcanic Zone. It is formed by NW-SE-aligned eruptive centers divided into two subcomplexes, namely Cerro Blanco (basaltic andesitic) and Las Termas (dacitic), and two satellite cones (to the SW and NE of the main alignment). Our study of the Shangri-La volcano, which is located between the two subcomplexes, in alignment with the satellite cones, and which produced dacitic lavas with basaltic andesitic enclaves, sheds light on the compositional and structural diversity of the volcanic complex. Detailed petrography along with mineral chemistry allows us to suggest partial hybridization between the enclaves and the host lavas and that mixing processes are related to the generation of the Shangri-La volcano and to other volcanic products generated in the complex. This is supported by mixing trends between the enclaves and the most differentiated units from Las Termas. We argue the presence of two main magma storage areas genetically related to crustal structures. A dacitic reservoir (~950 °C) is fed along NW-SE structures, whereas a deeper mafic reservoir (>1100 °C) utilizes predominantly NE-SW structures. We suggest that the intersection between these sets of structures facilitates magma ascent and controls the Nevados de Chillán plumbing system dynamics. Full article

Previous joint test studies have mainly been conducted under the condition of uniformly distributed loads, but in engineering, overlying loads are often non-uniformly distributed. It is necessary to investigate the shear mechanical properties of joints under non-uniform loads. This paper establishes three typical mechanical models: far-field concentration (FFC), near-field concentration (NFC), and focus on center (FOC). Direct shear test simulations using the DEM software PFC reveal that the location of load concentration affects main shear parameters. The closer the load concentration is to the far end along the shear direction, the greater the deformation of rock mass during failure is, the higher the proportion of shear cracks is, and the greater the strength and energy required for failure are. Compared to a uniformly distributed load (UD) condition, FOC shows similar mechanical properties; NFC yields inferior outcomes, while FFC results in superior mechanical performance compared to UD. By utilizing machine learning, five prediction models for non-uniform load shear strength are developed, with the Genetic-XGBoost algorithm demonstrating the highest accuracy. Weight calculation results indicate that load distribution form is the most critical factor influencing shear strength. Full article

Jointed soft-hard composite rocks are frequently encountered in nature, and this complex structure contributes to unpredictable fracturing mechanisms and failure behavior. In this study, soft-hard composite rocks with three joints were fabricated to conduct a uniaxial loading experiment, supplemented by Digital Image Correlation (DIC) and Acoustic Emission (AE) experiments. The results indicate that the mechanical parameters display a V-shape variation trend with the increase of joint angle, which minimized at 30°. The peak strength ranges from 33.48 MPa to 44.93 MPa. The failure characteristics change from tensile failure to shear failure and finally to intact failure. According to the displacement curves on both sides of the crack, the initiation of wing cracks is driven by the direct tensile displacement field and indirect tensile displacement field for specimens with joint angles of 0–30° and 75–90°, respectively. While the crack initiation from joint tips corresponding to specimens with a joint angle of 45–60° is controlled by direct and indirect tensile displacement fields. Wherein the cracks initiate from the coplanar joint in the hard layer, driven by the indirect tensile displacement field, and the cracks expanding upward from other joint tips are more susceptible to the indirect tensile displacement field. Full article

Euphorbia jolkinii dominates the subalpine meadows in Shangri-La (Southwest China) owing to its potent allelopathic effects. However, the effects underlying its allelopathy require further characterization at the physiological and molecular levels. In this study, the physiological, biochemical, and metabolic mechanisms underlying E. jolkinii allelopathy were investigated using Arundinella hookeri as a receptor plant. The treatment of A. hookeri seedlings with E. jolkinii aqueous extract (EJAE) disrupted their growth by inhibiting photosynthesis, disrupting oxidation systems, and increasing soluble sugar accumulation and chlorophyll synthesis. Collectively, this causes severe impairment accompanied by abnormal photosynthesis and reduced biomass accumulation. Moreover, EJAE treatment suppressed gibberellin, indoleacetic acid, zeatin, salicylic acid, and jasmonic acid levels while promoting abscisic acid accumulation. Further metabolomic analyses identified numerous differentially abundant metabolites primarily enriched in the α-linolenic, phenylpropanoid, and flavonoid biosynthesis pathways in EJAE-treated A. hookeri seedlings. This study demonstrated that E. jolkinii exhibits potent and comprehensive allelopathic effects on receptor plants, including a significant disruption of endogenous hormone synthesis, the inhibition of photosynthesis, an impairment of membrane and oxidation systems, and changes in crucial metabolic processes associated with α-linolenic, phenylpropanoid, and flavonoid biosynthesis. Thus, our study provides a solid theoretical foundation for understanding the regulatory mechanisms underlying E. jolkinii allelopathy. Full article

Jointed composite rock masses are ubiquitous, where the interplay between fractures and bedding planes significantly complicates their failure mechanisms. This study conducted uniaxial compression tests on a composite rock material featuring soft and hard components with unparallel double joints. Leveraging the digital image correlation (DIC) method and acoustic emission (AE) technology, the investigation analyzed the influence of joint angles on the mechanical properties, failure modes, and crack propagation behaviors. The results indicate that the peak strength exhibits an ascending–descending–ascending trend with the variation of upper joint angle, peaking at 90°. The failure modes can be systematically categorized into three types. The failure of the specimen is predominantly influenced by the upper joint. However, when the lower joint angle is relatively flat, it becomes more prone to contributing to the failure of the specimen. The lower joint-dominated failure mode only occurs when the upper joint angle is 90°. As the lower joint angle remains at 90°, an augmentation in the upper joint angle initially leads to a decrease and subsequently to an increase in the proportion of shear cracks. In contrast, when the lower joint angle deviates from 90°, the increase of the upper joint angle initially boosts and then diminishes the proportion of shear cracks. Full article

The national parks agglomeration in China is presently undergoing a pivotal phase of planning and construction. Synergistic development of nature-based tourism within the Qinghai–Tibet Plateau National Parks Agglomeration is essential for optimizing the spatial configuration of regional functions and substantiating the necessity of the agglomeration development of national parks. This study develops an assessment framework for the synergistic development of nature-based tourism based on the interconnection of elements. By constructing a model of nature-based tourism elements’ interconnections and employing social network analysis, it investigates the characteristics and status of synergistic development in nature-based tourism within the Qinghai–Tibet Plateau National Parks Agglomeration, while also proposing pathways for optimization. The findings reveal that: (1) By integrating multi-source heterogeneous data on resource complementarity, product connectivity, tourist source sharing, and information linkage, a robust assessment framework for the synergistic development of nature-based tourism in the national parks agglomeration was established. (2) The synergistic development of nature-based tourism within the national parks agglomeration on the Qinghai–Tibet Plateau demonstrates spatial heterogeneity. Shangri-La National Park and Qinghai Lake National Park serve as the core of the tourism flow network, whereas Mount Kailash National Park, Gaoligong Mountain National Park, and Pamir–Kunlun Mountains National Park exhibit the least favorable states of coordinated development. (3) Utilizing social network analysis, this study classified the national parks into core and peripheral positions within the nature-based tourism synergy network and proposed corresponding optimization strategies. The findings of this research contribute to optimizing the overall layout of the Qinghai–Tibet Plateau national parks agglomeration. Additionally, they provide theoretical and methodological references for the nature-based tourism synergistic development in other national park agglomerations. Full article

Accurate estimation of forest aboveground carbon stock (AGC) is essential for understanding carbon accounting and climate change. In previous studies, the extracted factors, such as spectral textures, vegetation indices, and textural features, were used to estimate the AGC. However, few studies examined how different factors affect estimation accuracy in detail. Meanwhile, there are also many uncertainties in the collection and processing of the field data. To quantify the various uncertainties in the process of AGC estimation, we used the random forest (RF) to establish estimation models based on field data and Sentinel-1/2 images in Shangri-La. The models included the band information model (BIM), the vegetation index model (VIM), the texture information model (TIM), the Sentinel-2 factor model (S-2M), and the Sentinel-1/2 factor model (S-1/2M). Then, uncertainties resulting from the plot scale and estimation models were calculated using error equations. Our goal is to analyze the influence of different factors on AGC estimation and to assess the uncertainty of plot scale and estimation models quantitatively. The results showed that (1) the uncertainty of the measurement was 3.02%, while the error of the monocarbon stock model was the main uncertainty at the plot scale, which was 9.09%; (2) the BIM had the lowest accuracy (R² = 0.551) and the highest total uncertainty (22.29%); by gradually introducing different factors in the process of modeling, the accuracies improved significantly (VIM: R² = 0.688, TIM: R² = 0.715, S-2M: R² = 0.826), and the total uncertainty decreased to some extent (VIM: 14.12%, TIM: 12.56%, S-2M: 10.79%); (3) the S-1/2M with the introduction of Sentinel-1 synthetic aperture radar (SAR) data has the highest accuracy (R² = 0.872) and the lowest total uncertainty (8.43%). The inaccuracy of spectral features is highest, followed by vegetation indices, while textural features have the lowest inaccuracy. Uncertainty in the remote-sensing-based estimation model remains a significant source of uncertainty compared to the plot scale. Even though the uncertainty at the plot scale is relatively small, this error should not be ignored. The uncertainty in the estimation process could be further reduced by improving the precision of the measurement and the fitting of the monocarbon stock estimation model. Full article

In forest resource surveys, using sampling methods to estimate aboveground carbon stock (ACS) can significantly reduce survey costs. This study improves the accuracy of ACS estimation by optimizing the stratified sampling design. The sampling process was divided into two stages: stratification and intra-stratum sampling. For stratification, remote sensing features were used as stratification variables, and a spatial clustering stratification method was introduced. For intra-stratum sampling, a composite method, Spatially Correlated Poisson Disk Sampling (SCPDS), was proposed. Using Random Forest (RF) and the sample points selected by SCPDS, the ACS was estimated and compared with traditional sampling methods for Pinus densata in Shangri-La, Yunnan, China. The results showed that (1) by selecting effective stratification variables (e.g., texture features), the required sample size was reduced by up to 19.35% compared to that of simple random sampling; (2) the Ward clustering method greatly improved stratification heterogeneity; (3) for intra-stratum sampling, the SCPDS method ensured spatial independence within strata, particularly at low sampling rates (1%–5%), where its error was significantly lower than that of other methods, indicating greater stability and improved accuracy; (4) the SCPDS-based model achieved the best fitting accuracy, with R² = 0.886. The total carbon stock of Pinus densata using RF was 7,872,787.5 t, closely matching forest management inventory (FMI) data. Through sampling, even with a relatively small sample size, the representative plots can still accurately reflect ACS estimates that are consistent with those derived from large-scale plot surveys. Thus, the optimized stratified sampling method effectively reduced sampling costs while significantly enhancing the stability and accuracy of the results. Full article

Pile and anchor structures are extensively employed for slope stabilization. However, their dynamic response under seismic loading remains unclear and current seismic designs primarily use the pseudo-static method. Here, a three-dimensional numerical simulation of the dynamic behavior of a bedding rock slope supported by pile–anchor systems under earthquakes is conducted. The dynamic calculation for the slope subjected to seismic forces with varying excitation directions and acceleration amplitudes is performed. The dynamic behavior of both the slope and the pile–anchor system is investigated with respect to the slope’s failure mode, the dynamic soil pressure behind the pile, the anchor axial force, the bending moment, and the lateral displacement of the pile. The results indicate that the anti-slide piles cause a reflective and superposition effect on seismic waves within weak rock layers. As the input seismic intensity increases, the axial force in the anchor cables also increases, with the peak axial force occurring during the main energy phase of the seismic waves. The dynamic soil pressure acting behind the piles varies with the stratification of the slope rock layers, with lower peak dynamic earth pressure observed in weak layers. The weak layers on the slope surface experience through-shear failure. Under strong seismic loading, the structural element state undergoes significant changes. Full article

The renovation and revitalization of vernacular architecture are pivotal in sustainable rural development. In regions like Shangri-La, traditional structures not only safeguard cultural heritage but also provide a foundation for enhancing local communities’ living conditions. However, these villages face growing challenges, including infrastructure decay, cultural erosion, and inadequate adaptation to modern living standards. Addressing these issues requires innovative research approaches that combine heritage preservation with the integration of contemporary functionality. This study employs a research-by-design approach, focusing on the Shanpian House as a case study, to explore how pre-planning and post-evaluation methods can revitalize traditional vernacular architecture. The pre-planning phase utilizes field surveys and archival research to assess spatial, cultural, and environmental conditions, framing a design strategy informed by field theory. In doing so, it evaluates how traditional architectural elements can be preserved while introducing modern construction techniques that meet current living standards. The post-evaluation phase, conducted through questionnaires and semi-structured interviews, assesses user satisfaction, focusing on the impact of architectural esthetics, structural stability, and material choices. Key findings from an OLS regression highlight the strong positive correlation between architectural style, structural choices, and cultural relevance with resident satisfaction. The research emphasizes that design elements such as structural details, materials, and infrastructure upgrades are critical in shaping perceptions of both functionality and cultural identity. Interestingly, the model reveals that improving architectural esthetics, alongside modern indoor features such as network connectivity, has a significant impact on enhancing overall resident satisfaction (significance level: 0.181). This study contributes to the broader discourse on sustainable building renovation by demonstrating how traditional architecture can be thoughtfully adapted for contemporary use and also proposes a paradigm shift in the renovation of historic buildings, advocating for a balance between preservation and modernization. The application of sustainable materials, digital modeling, and innovative construction techniques further ensures that these traditional structures meet the demands of modern civilization while maintaining their cultural integrity. Full article

Genetic diversity is crucial for determining the evolutionary potential of a species and is essential for developing optimal conservation strategies. The impact of habitat fragmentation on the genetic diversity of food-deceptive orchids seems to be unpredictable because of their specialized seed and pollen dispersal mechanisms. The habitat of deceptive Cypripedium flavum was severely fragmented during the past half century. This study investigated the genetic diversity and structure of seven fragmented Cypripedium flavum populations in Shangrila County using AFLP markers. A total of 376 alleles were identified, with a range of 70 to 81 alleles per locus. The species exhibited considerable genetic diversity, as evidenced by an average Nei’s gene diversity (H) of 0.339 and a Shannon’s information index (I) of 0.505, with all loci being polymorphic. Based on Molecular Variance (AMOVA), 8.75% of the genetic differentiation was found among populations, while the remaining 91.25% of genetic variation occurred within populations. Population structure analysis revealed that the C. flavum germplasm can be categorized into 2 distinct groups, among which there was significant gene flow. Despite habitat fragmentation, C. flavum still retained a high level of genetic diversity, and the substantial gene flow (5.0826) is a key factor in maintaining the genetic diversity. These findings offer valuable insights for the conservation and potential use of C. flavum genetic resources. Full article

Surface subsidence resulting from block caving mining causes considerable environmental and economic harm in mining areas, highlighting the critical need for accurate predictions of surface subsidence. Given the unique features of the block caving technique and the resemblance between the released ore pillars and the mining processes, this paper developed a lightweight model to forecast surface settlement utilizing the probability integration approach to address the issue of predicting surface settlement in metallic mines. This study focuses on the Pulang Copper Mine, situated in the northeast of Shangri-La County within the Yunnan Province, as a case example. This mine employs the block caving method, which results in substantial surface subsidence. A visual mining simulation program is designed to combine the ore mining plan with the prediction model, manage the ore output of each mining point in batches, treat the ore pillars released in the planning cycle as strip work, and simulate and calculate the surface area above the ore pillars settlement value. The calculated values of surface subsidence induced by ore drawing are then interpreted as the downward displacement of the surface subsidence beneath the strip workings. Furthermore, to verify the reliability of the model, three-dimensional laser point cloud data of the Pulang Copper Mine in recent years were collected, and the differences between the predicted surface and the measured surface were calculated and analyzed. Full article