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Karst spring water dynamic characteristics and its response to atmospheric precipitation are of great significance for water resources utilization under the background of climate change. This paper selects Longzici spring area, North China, as the study area. Based on a long series of spring water flow and precipitation data, the dynamic characteristics of spring flow were analyzed and the numerical simulation of the groundwater flow model was established. The results show that the groundwater kept the sustained decline over the past decades which is in a negative equilibrium state, with a storage variable of − 2.26 million m3/year. The sensitivity of spring flow to precipitation under different precipitation scenarios shows that the water level changes in the recharge and drainage areas are similar about (3–5 cm) and slightly larger than that in the runoff area(1.5 cm) when minimum rainfall (287.24 mm) happens. When the precipitation is at its maximum (867.66 mm), the water level change in the runoff area can reach 95 cm which is much larger than those in the recharge and discharge areas. The results indicate that Longzici karst spring has a relatively good regulation water resource capacity and the runoff area is more sensitive which plays an important role in response to climate change. [ABSTRACT FROM AUTHOR]

Fracture of high-level extra thick and hard roof (ETHR) above the coal seam is the main reason for the frequent occurrence of mine dynamic disasters such as mine earthquake and rock burst. In order to address this problem, the ground fracturing technology was proposed in this paper to presplit the high-level roof. The FLAC numerical model was established to study the dynamic response of the ETHR before and after fracturing. The simulation results show that: The existence of hydraulic fracture can effectively reduce the first breaking span of ETHR, and slow down the stress and elastic deformation energy concentration of coal and rock mass on both sides of goaf. In order to ensure the economical and effective opening of prefabricated cracks, the comprehensive influence of tensile stress zone and induced stress between cracks should be fully considered in the design of crack spacing. Finally, the field test of hydraulic fracturing was carried out in 63up06 working face in Dongtan coal mine in China. The results of microseismic monitoring showed that there were only 4 strong mine earthquake events of magnitude 2.0 that happened in the first 400 m of excavation, compared with the adjacent working face, the number of large energy mining earthquake events decreased significantly. It showed that the ground fracturing effectively controlled the high and thick strata and verified the feasibility of the ground fracturing technology. The research results can provide some guidance for the treatment of mine earthquake and rock burst in similar working face. [ABSTRACT FROM AUTHOR]

As an important resource for human survival, soil plays an important role in maintaining productivity, environmental quality, animal and plant health, etc. Soil quality evaluation, as a decision-making tool to improve understanding of soil quality, can effectively indicate soil status. Mu Us sandy land of Daji Khan in northern Shaanxi Province is one of the serious desertification areas in China. The phenomenon of soil erosion and ecological deterioration is extremely serious. Therefore, it is urgent to strengthen to pay attention to the research of Mu Us sandy land, to help the restoration of damaged soil, and to build a powerful soil ecosystem. In this paper, the soil quality in the process of development and utilization of the Mu Us sandy land was evaluated based on fuzzy sets for the purpose of sustainable utilization of compound soil. Based on soil structure and soil fertility, 16 evaluation indexes of soil quality in Mu Us sandy land were screened, and then the evaluation index system of soil quality was constructed. The fuzzy multi-objective decision-making model based on fuzzy sets was used to comprehensively evaluate the soil quality from 2013 to 2019. We calculated that the year-on-year growth rates of soil quality from 2013 to 2019 are 13.56, 0.16, 12.81, 33.84, 9.68, and 14.80%, respectively. The results showed that the overall soil quality in the study area showed a trend of increasing year by year, and the year-on-year increase was the largest in 2017. Meanwhile, the reasons for the sudden increase in soil quality in typical years were analyzed. The results showed that the dominant factor of this phenomenon was the comprehensive influence of soil fertility. Furthermore, the relationship between soil fertility and cultivated horizon in typical years was analyzed one by one, and the specific factors affecting soil fertility were discussed. [ABSTRACT FROM AUTHOR]

Yilong Lake is the southernmost plateau freshwater lake in China. The health of its watershed ecosystem is of special strategic significance to maintain the ecological security and ensure the sustainable development of regional economy and society. This paper analyzed the characteristics of landscape type in Yilong Lake Basin of 1990, 1995, 2000, 2005, 2010, 2015 and 2018 and discussed the impact of landscape pattern type changes and its effect on ecosystem services values (ESV). The results showed that: (1) The landscape types of Yilong Lake are mainly forest land and the largest dynamic degree of comprehensive 1andscape type in the six stages is 2010–2015 and the smallest is 2015–2018. (2) Spatially, the most frequent conversion was arbor forest land, which turned to shrub forest land and garden land. The rapid expansion of construction land and transportation land were turned by cultivated land area. (3) Temporally, from 1990 to 2018, the total ESV also increases year by year, and the regional distribution of high ESV is consistent with the distribution of water areas and gardens. The comprehensive analysis shows that the implementation of governance projects such as ecological protection and governance of Yilong Lake surface mountain are conducive to increase the landscape types and the total ESV. [ABSTRACT FROM AUTHOR]

Identification of volcanic lithofacies is critical for reservoir exploration and a major difficulty in China's Liaohe oil field. In this paper, we present a fractal analysis method for identifying volcanic facies by estimating the fractal dimension of logging data. The fractal properties of lithofacies logging curves are explored, as well as the categorization scheme of volcanic lithofacies in the eastern sag of the Liaohe basin. Five logging curves impacted by volcanic lithofacies from four wells in the Liaohe basin's eastern depression were chosen. The Box-counting dimension is used to develop a logging lithofacies identification criterion. Furthermore, we calculated the fractal dimension of logging curves using box-counting dimension methods. [ABSTRACT FROM AUTHOR]

Recently, special attention has been drawn to the high-salt argillaceous dolomite reservoir in Jianghan basin, China due to its abundant oil resources with complex geological conditions. However, the current production methods used to develop this reservoir are not efficient with low throughput. Hence, the purpose of this paper is to explore the main possible reasons affecting the oil well productivity and determine suitable field development method for the target oilfield through experimental and numerical simulation approaches. The mercury injection capillary pressure (MICP) test results indicate that the average pore radius of samples is 0.0144 μm, and pore size distribution (PSD) results from MICP indicate that single peaks appeared in the PSD curves of the pore type samples. Permeability peaks of the samples range from 0.01 to 0.03 μm, and mesopores make most of the permeability contribution of the samples, which also reveals the low-permeability and porosity characteristics of the target oilfield. The results of core stress sensitivity tests show that the largest permeability damage rate is 98.97% with an average permeability damage rate of 98.37% while the maximum porosity damage rate is less than 10% with an average damage rate of 5.57% during the process of depressurization. The results of Non-Darcy percolation experiment indicate that threshold pressure gradient testing by water is about 0.03 MPa/m, which is close to the actual situation of the target oilfield. Numerical simulation method that considers the impact of threshold pressure gradient and stress sensitivity were established to study flooding patterns deployment for the research area. The simulation results show that performing water alternating gas flooding (WAG) by using CO2 is recommended for the development of the high-salt reservoir with inverse five-spot flooding pattern made up of 400 m well spacing in X-direction and 150 m row spacing. [ABSTRACT FROM AUTHOR]