Ecuador has a relatively low level of geological exploration but possesses significant potential for copper resources. It has emerged as a hotspot for copper exploration and development on a global scale. Currently, investment in copper exploration and development ranks first among all mineral types and is experiencing rapid growth. This sector is primarily dominated by mining companies from Europe and the United States, although China and Ecuador also play important roles. Since the beginning of the 21st century, substantial progress has been made in the exploration and development of copper resources. Four major copper deposits have been discovered, leading to a rapid increase in reserves, resources, and production. Over the past decade, the total of new reserves and resources has accounted for 11.56% of the global increase, positioning Ecuador fourth in the world. From 2019 to 2024, the output of copper has surged by more than 15 times, which has become a crucial source for China's copper resource security. By systematically analyzing the endowment characteristics and the current status of exploration and development of Ecuador's copper resources, along with the country's resource and investment environment, this paper evaluates the investment potential of copper ore, as well as the opportunities and risks involved. It is recommended that Chinese enterprises enhance their research on the rules of copper mineralization, focus on the changes in mining rights registration and mining laws, and stay informed about the latest discoveries in major copper projects .

Objective: To address the unclear grout diffusion mechanism and the insufficient understanding of geoelectrical response characteristics during grouting in saturated sand strata, indoor grouting simulation experiments were conducted to investigate the grout diffusion behavior and its geoelectrical response characteristics in saturated sand layers, so as to provide a theoretical basis for real-time monitoring and performance evaluation of grouting-based water control and strata reinforcement in underground engineering. Methods: A saturated sand layer was constructed in a three-dimensional physical model with dimensions of 82 cm × 82 cm × 82 cm, and grouting experiments were carried out under a grouting pressure of 0.3 MPa. Based on the indoor three-dimensional model and a parallel electrical monitoring system, the exciting current, self-potential, primary field potential, and apparent resistivity were dynamically monitored throughout the entire grouting process. The spatiotemporal evolution characteristics of these electrical parameters during grout diffusion and consolidation were then systematically analyzed. Results: The experimental results showed that the exciting current was a sensitive electrical parameter for characterizing the grout diffusion and consolidation processes, effectively reflecting the advance of the grout front and the evolution of conductive pathways. At the initial stage of grouting, the exciting current decreased from approximately 0.75 mA to 0.65 mA. Subsequently, with the displacement and mixing of grout and pore water, the electrical conductivity increased, and the exciting current rose to approximately 0.80 mA before gradually stabilizing. Both the self-potential and primary field potential exhibited pronounced fluctuations and increasing trends during grouting, which effectively revealed the migration pathways and diffusion range of grout at different strata levels. Owing to the heterogeneity of the weathered zone, the variations in electrical parameters were more complex, with stronger spatial differences and instability, whereas the responses in the saturated sand layer were relatively consistent. The three-dimensional inversion results of apparent resistivity indicated that the resistivity generally decreased first and then increased during the grouting process. During the grouting stage, grout entered the formation and mixed with pore water, forming a low-resistivity zone of approximately 50 Ω·m. During the consolidation stage, as cement hydration intensified and pore spaces were progressively filled, the free water content decreased and the conductive pathways within the pores were weakened, resulting in a gradual increase in resistivity to above 150 Ω·m. Conclusions: Grout diffusion and consolidation in saturated sand strata induce significant geoelectrical responses during the grouting process. Among the monitored parameters, the exciting current is the most sensitive to the advancing grout front and consolidation evolution, while the self-potential, primary field potential, and apparent resistivity can characterize grout migration and consolidation features from different perspectives. Grout consolidation in saturated sand strata exerts a pronounced weakening effect on conductive pathways, leading to significant electrical property variations. The results of this study can provide a reference for the real-time monitoring, dynamic identification, and engineering evaluation of grouting-based water control and reinforcement effects in underground engineering such as coal mines.

Against the backdrop of sustained growth in China’s energy demand and the progressive exhaustion of coal resources in eastern mining districts, coal-bearing regions in Northwest China are assuming an increasingly important role in maintaining long-term energy supply stability. Nevertheless, coal extraction in this region is inherently constrained by fragile geological settings, which pose fundamental challenges to large-scale, deep, and long-duration mining activities. As mining disturbances accumulate over time, tensions between coal exploitation and the regional geological-environmental system continue to intensify. In this context, this study focuses on the coupled responses of key Earth system components, including the lithosphere, hydrosphere, ecosphere and atmosphere, to coal mining disturbances. Drawing on the conceptual framework of Earth system science, geological safeguard requirements and implementation pathways for loss-reducing coal mining are proposed. First, it provides an in-depth analysis of the effects of coal mining on Earth's multi-spheres and clarifies the relationship between Earth system science and coal mining. Second, from the perspectives of Earth system science, such as holism, dynamism, quantification, and systematization, it innovates the geological support requirements for low-impact coal mining in terms of geological survey methods, evaluation of geological elements, evolution of geological conditions, and sustainable development of geological resources. Finally, by integrating multi-scale and multi-approach exploration and observation technologies, a geological survey method and a three-dimensional dynamic monitoring model covering the entire coal mining lifecycle are established. Utilizing massive, multi-source, and diverse measured data, a multi-sphere coupling model is constructed to quantitatively analyze the dynamic evolution of geological elements during coal mining, thereby building a supply-side-guided guarantee system for minimizing mining-induced damage. From a methodological standpoint, Earth system science offers an effective framework for interpreting the interconnected responses of multiple Earth system components induced by coal mining, while mining activities provide a natural laboratory for exploring multi-sphere coupling mechanisms. Geological safeguard research for loss-reducing coal mining therefore necessitates a fundamental paradigm shift from traditional practices characterized by static assessments, segmented stages, experience-based judgments, single-sphere isolation, and production-oriented priorities to an integrated approach centered on process-based dynamics, quantitative geological characterization, multi-sphere coupling, and sustainability considerations. To support this transition, a comprehensive geological safeguard system is proposed, incorporating an integrated "space-air-ground" monitoring network, quantitative models describing cross-sphere interactions, and supply-side driving mechanisms. This system is intended to enable a full life-cycle framework for loss-reducing coal development, extending from precise early warning of mining-induced risks to diversified utilization of resources and products after mine closure. This research provides important theoretical support for achieving green mining of coal resources and holds significant practical value for the implementation of strategic national energy policies in the northwest region.

In recent years, the significant increase in land resource demands in loess gully regions has led to rapid development of fill engineering projects, accompanied by increasingly prominent landslide hazards. While altering the original topography, these projects substantially modify the stress state of soil mass, with moisture content and confining pressure fluctuations becoming critical factors affecting slope stability. This study focuses on a loess-filled slope in Tianshui City, conducting a series of triaxial creep tests under controlled moisture content and confining pressure. The results demonstrate: ① Increased moisture content weakens soil structure and reduces soil strength, while higher confining pressure restricts lateral deformation. ② During moisture content elevation, the failure mode transitions from brittle fracture to plastic bulging (notably at 24% moisture content), with significantly increased axial compression. ③ Moisture content increase elevates pore water pressure, shifting the Mohr circle leftward; meanwhile, long-term creep effects reduce shear strength through decreased effective stress and moisture-induced cementation weakening, triggering shear failure when the Mohr circle boundary exceeds the new strength threshold. ④ Although confining pressure enhances long-term soil strength, stress redistribution in actual projects causes shear stress concentration at the slope toe as fill height increases, ultimately reducing slope stability. This study systematically reveals the creep behavior, failure characteristics, and stress evolution of filled slopes under varying moisture content and confining pressure conditions, providing experimental references and theoretical foundations for stability control in loess-filled engineering projects.

To elucidate the mechanical and seepage properties of typical Yan'an loess at different burial depths and its microstructural evolution patterns, this study systematically investigates four in situ loess layers (L₁–L₄) from a representative profile in Fuxian County, Yan'an. The objective is to clarify the synergistic mechanism of “structural densification–strength enhancement–permeability reduction,” providing scientific basis for regional loess stratum stability assessment and impermeability reinforcement design. Systematic investigations were conducted on the four loess layers using direct shear tests, permeability tests, and scanning electron microscopy (SEM) analysis. Pore parameters were quantitatively extracted using Avizo software. Data coupling analysis was performed via Pearson correlation analysis and principal component analysis (PCA). Results indicate: ① Shear strength exhibits a layered pattern with burial depth, showing significantly increased cohesion and a slight decrease in internal friction angle. ② The permeability coefficient decreases significantly with depth, exhibiting a “permeable upper layer, dense lower layer” characteristic, plummeting from 17.79×10⁻⁵ cm/s in Layer L₁ to 7.55×10⁻⁵ cm/s in Layer L₄. ③ At the microstructural level, particle contact patterns change from point contact and weak cementation in shallow layers to surface contact and strong cementation in deeper layers. Pores evolved from large pores (>35 μm) to medium-small pores (<30 μm), with shapes tending toward roundness. The orientation shifted from vertical dominance to uniform distribution. ④ Pearson analysis indicates a significant positive correlation between dry density and cohesion, while showing significant negative correlations with total pore area and permeability coefficient. PCA analysis reveals PC1 (contribution rate 70.8%) as the primary factor governing “structural densification-strength enhancement,” clearly distinguishing sample distributions between L₁ (loose, high permeability) and L₄ (dense, low permeability) layers. Conclusions indicate that the evolution of physical and mechanical properties in Yan'an loess is jointly governed by compaction and microstructural remodeling. With increasing burial depth, loess undergoes a “compaction-remodeling-densification” process: particles become more tightly packed, contact modes shift to surface contact, and large pores are compressed and destroyed, replaced by medium and small pores. Macro-scale manifestations include increased cohesion and significantly reduced permeability. Dry density, cohesion, and pore characteristics collectively govern the overall evolutionary trend of loess from loose and highly permeable to dense and low-permeability.

The superimposed effects of extreme rainfall events and engineering disturbances in the Loess Plateau have led to a significant increase in the risk of shallow loess landslides. This situation reveals the engineering governance contradiction of "ecological improvement vs. disaster intensification" in ecological restoration projects. This study focuses on the mechanical properties of the root-soil interface of Robinia pseudoacacia. Through methods including in-situ testing, single shear test, and theoretical analysis, we systematically quantified the multi-field coupling effects of moisture content fluctuations, root topological types, and variations in root content on the shear strength evolution of the root-soil interface. The results indicate: ① Vegetation roots in the shear strength characteristics of the root-soil interface. The shear process can be divided into three stages: initial linear elastic deformation, damage accumulation, and progressive failure. ② The stress-strain curves of the root-soil interface can be categorized into softening and hardening types, with the softening type comprising a strength-increasing phase followed by a strength-decaying phase. ③ A predictive model considering the stress-strain softening of the root-soil interface was proposed, demonstrating favorable predictive performance. This research provides essential data and theoretical support for ecological restoration in rapid slope stability assessments that incorporate vegetation factors.

The seasonal rainfall leads to a frequent wet-dry cycle environment across the China Loess Plateau. This environment often aggravates foundation settlement and collapsible deformation in loess subgrades. This study investigates the coupling mechanism of microstructural damage and macro-deformation evolution under wet-dry cycles. The findings provide a theoretical basis for engineering disaster prevention in loess regions. Artificially structured loess with controllable composition and uniform structure was prepared to simulate natural loess. This experimental approach facilitated the systematic study of the effects of wet-dry cycles (0～9 cycles) on loess. Macro-mechanical behaviors were tested using confined compression and single-line collapsibility methods. Microstructural characteristics were analyzed via Scanning Electron Microscopy (SEM), particle analysis, and X-ray Diffraction (XRD). The test results indicate that wet-dry cycling causes irreversible damage to the loess microstructure. Macroscopically, compressive deformation shows a significant positive correlation with the number of cycles. Conversely, the collapsibility coefficient follows a non-monotonic evolutionary pattern, first increasing and then decreasing. The structural parameters exhibit a non-linear decay characterized by an "initial sharp drop followed by stabilization". The first three cycles constitute the primary structural damage phase; the decay rate slows down significantly during cycles 5 to 9, reaching only about one-quarter of the initial rate. Microscopically, the dissolution and loss of cementing agents cause the soil structure to evolve. The support system transforms from a "strong cementation-large aggregate" structure to a "weak cementation-loose particle" contact system. This loss of cementing agents and the resulting microstructural rearrangement are the essential causes of macroscopic mechanical degradation. In the initial cycles, structural disintegration driven by cementation failure dominates. This significantly enhances collapsibility sensitivity. In later cycles, pore compaction and structural reorganization increase the soil's resistance to further deformation. Therefore, engineering practices must prioritize waterproofing during the early exposure period of the foundation to prevent sudden settlements caused by accumulated structural damage.

The study of the wetting-induced deformation mechanism of loess is of great importance for engineering disaster prevention and control in the Loess Plateau region. This research focuses on the Q₃p and Q₂p loess from Fuxian County, northern Shaanxi, aiming to reveal the deformation behavior and underlying mechanisms of loess from different geological eras under wetting conditions. A comparative study of the engineering properties of the two types of loess was systematically conducted through a series of physico-mechanical tests, mineral composition analysis, scanning electron microscopy (SEM) observations, and multi-condition consolidation-collapse tests. The results indicate that the consolidation deformation process of both types of loess can be divided into three stages: slow deformation under low pressure, accelerated deformation under medium pressure, and stabilized deformation under high pressure. Under high pressure conditions, the consolidation deformation becomes more sensitive to changes in initial water content. With increasing initial water content, the compression deformation of the Q₃p specimens intensifies significantly, while that of the Q₂p specimens weakens. In collapse tests, the two groups exhibited fundamentally opposite deformation characteristics: the Q₃p specimens showed typical collapse behavior, with the collapse coefficient initially increasing and then decreasing with rising pressure, whereas the Q₂p specimens displayed certain expansion characteristics. As the initial water content increased, the collapse coefficient of the Q₃p specimens gradually decreased, while the expansion tendency of the Q₂p specimens also weakened. Microstructural analysis revealed that the stability of the loess microstructure, particularly the presence of large pores, provides the necessary space for compression and collapse deformation. Mineral composition analysis indicated that the dissolution of soluble salt minerals (e.g., calcite) exacerbates soil compression and collapse deformation, while the water-absorbing expansion of clay minerals (e.g., illite) partially suppresses these behaviors. This study elucidates the controlling mechanism of the coupling effect between mineral composition and microstructure on the wetting-induced deformation behavior of loess, providing important theoretical support and practical guidance for engineering construction and geohazard mitigation in loess regions.

As the core node of the "belt and road" Central Asia land route, the engineering geological stability of Ili region in Xinjiang is crucial to regional development. The mechanical properties of Quaternary loess, which is widely distributed in the region, are continuously deteriorated under the complex climatic conditions such as seasonal freeze-thaw, dry wet cycle, heavy rainfall and the continuous effect of engineering activities, thus inducing frequent regional loess landslides. Therefore, it is of practical significance to further study the effect of freeze-thaw-wetting-drying (FTWD) cycle on the mechanical properties and nonlinear degradation law of Ili remolded loess. Based on the consolidated undrained triaxial shear test and microscopic test under FTWD cycle, the stress-strain response, strength parameter evolution and damage mechanism were revealed from the macro and micro scale. On this basis, assuming that the micro element strength of loess obeys the Log-logistic distribution function, the damage model of loess is established and its applicability is verified. The results showed that the shear strength decreased by 22.9% with the increase of the number of cycles, and the cohesion attenuation (45.2%) was significantly higher than the internal friction angle (7.27%). In the microscopic image, it can be seen that the compacted loess presents the characteristics of aggregate structure.The deviatoric stress-strain relationship curve of Ili loess sample is mainly strain hardening type. The cohesion of Ili loess decreases significantly with the increase of FTWD cycles, while the internal friction angle changes slightly. Combining the traditional Duncan-Chang model with the statistical damage theory, a constitutive model which can uniformly characterize the strain hardening and strain softening characteristics under different FTWD cycles is established, and the model parameters are solved. The model verification shows that it has good predictability for the test results under different confining pressures and cycles.

In order to study the soil-water characteristics and micro-mechanism of sulfate saline soil under freeze-thaw-salt coupling, the soil-water characteristic curves of saline soil with different salt content were tested and fitted with Gardner model, van-Genuchten model, and Fredlund-Xing model, and the microstructure and pore distribution characteristics of sulfate saline soil under freeze-thaw-salt coupling were analyzed. The results indicate that the volumetric water content of sulfate-salted soil decreases as matrix suction increases, with the resulting curves exhibiting a single-peak inverse ‘S’ shape. Notably, for a given volumetric water content, higher salt concentrations correspond to increased matrix suction. Freeze-thaw cycles promote the microstructural disintegration of the soil, leading to an increase in large pore volume and overall porosity. Following these cycles, both the matrix suction and volumetric water content of the soil samples decreased, causing the soil-water characteristic curve to shift leftward with an increasing number of freeze-thaw cycles.To evaluate the test results of saline soil, the G model, V-G model, and F-X model were employed. The F-X model exhibited a low fitting correlation coefficient, while the V-G model demonstrated poor fitting in both high and low suction phases. In contrast, the G model provided an overall good fitting performance. The microstructural changes in soil samples resulting from freeze-thaw actions are critical factors contributing to the reduction of the soil's water-holding capacity. The progressive development of pores and fissures in the samples, influenced by freezing, thawing, and salinity, facilitates the migration of water equilibrium.