Cave Soil Research Articles

Model Test and Numerical Simulation for Tunnel Leakage-Induced Seepage Erosion in Different Strata

Leakage in underground structures, especially tunnels, may cause seepage erosion in the surrounding soil, which in turn leads to ground subsidence, posing a great threat to urban safety. The current literature mainly focuses on seepage erosion in the sand but lacks a systematic study on the development process of seepage erosion induced by tunnel leakage in different strata. To investigate the different seepage erosion modes induced by tunnel leakage in different stratum types, a series of reduced-scale model tests were carried out. A coupled fluid–solid numerical model was further established to analyze the fine-scale characteristics of different seepage erosion modes. The results show that (1) the soil seepage erosion modes can be divided into three categories: no soil cave, unstable soil cave, and stable soil cave; (2) the adopted coupled fluid–solid numerical model based on DEM, which takes into account the degradation of clay during seepage erosion, can effectively simulate the erosion process of soil with different seepage erosion modes; (3) the phenomena of the three erosion modes are different in the process of erosion development; and (4) the micro-mechanisms of the three seepage erosion modes are different, which are manifested in the erosion range, soil arching effect, and displacement.

Numerical Simulation on the Leakage-Induced Collapse of Segmental Tunnels

Sudden leakage during tunnel construction poses a great threat to the safety of the tunnel. There are relatively few studies on the mechanism of structural collapse induced by tunnel leakage, so it is difficult to propose effective control measures. To solve this problem, a coupled fluid–solid strata analysis model and a nonlinear FEM tunnel model were established based on model test results to analyze the mechanism of tunnel collapse. The following conclusions were drawn: (1) A DEM-based coupled fluid–solid model combined with a nonlinear FEM tunnel model can effectively simulate the physical process of tunnel collapse. (2) The mechanism of tunnel leakage-induced strata response is the continuous destabilization and reappearance of the soil arching effect, which restricts the erosion of the soil and results in macroscopic soil caves, and finally leads to the impact load of the destabilized soil. (3) The process of the tunnel structure collapse is as follows: firstly, a large deformation of the tunnel structure is caused by the redistribution of external loads generated by the earth arching effect; then, due to the multiple impact loads from the destabilization of the soil, plastic hinges are generated at the tunnel joints, and the tunnel collapses.

Study on the Influence of Moisture Content and Void Ratio on the Disintegration of Red Clay

Guilin is a famous karst area, and currently the view that the disintegration of red clay will cause soil cave collapse is increasingly recognized. In order to study the influence of the coupling effect of moisture content and void ratio on the disintegration of red clay, different moisture contents and void ratios of Guilin red clay were placed on a self-made disintegration apparatus to record the real-time disintegration amount and observe the disintegration phenomenon. Images of the structural characteristics of soil were obtained by a scanning electron microscope (SEM). Additionally, nuclear magnetic resonance (NMR) was applied to analyze the distribution of water in both natural and saturated states. The results show that the disintegration rate of red clay decreases as the initial moisture content increases, but increases with the increase of void ratio. Both moisture content and void ratio affect the structural characteristics of red clay. When the moisture content remains constant, the soil changes from a three-peak to a two-peak structure as the void ratio increases. The total area and secondary peak area of the T2 spectrum increase, while the starting T2 value of the main peak shifts to the right and the area decreases. Meanwhile, the starting T2 value of the secondary peak shifts to the right and the area increases. When the void ratio remains constant, the starting T2 value of the main peak gradually shifts to the left and the area decreases as the moisture content increases. However, the starting T2 value of the secondary peak shifts to the right and the area decreases or first decreases and then increases. The disintegration rate does not exhibit a significant relationship with either pore volume or macropore volume. The combined water saturation shows a bilinear relationship with both the moisture content and void ratio, where it increases as the initial moisture content increases, but decreases as the void ratio increases, with a correlation coefficient of 0.9929. The disintegration rate has an exponential relationship with the combined water saturation, and it decreases as the combined water saturation increases, with a correlation coefficient of 0.9934.

Prospecting and evaluating antimicrobial resistance and metal tolerance of microorganisms isolated from cave soil in Serra de Carajás – PA

The microbial communities present in cavities, especially in iron lithology environments, remain largely unknown. The isolation and characterization of cave microbiota are essential for identifying new species and obtaining substances of biotechnological relevance, such as antimicrobial compounds and microorganisms capable of bioremediating heavy metals. The objective of this study was to evaluate the antimicrobial activity and metal tolerance of bacteria isolated from the soil of caves GEM-1423 and GEM-1462 located in the Campos Ferruginosos National Park, in Serra de Carajás, Pará, Brazil. The bacteria were isolated from soil in different zones of the caves (photic, penumbra and aphotic) and subjected to antimicrobial susceptibility tests using the disk-diffusion technique and assessment of tolerance to metals by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (CBM). Regarding the resistance profile, the bacteria showed high resistance to the antimicrobials Trimethoprim, Ampicillin and Amoxicillin. All bacteria showed tolerance to the metals Fe, Mn, Pb, Mg and K. These data are fundamental to understanding the potential of these microbial communities in iron lithology environments, thus contributing to the advancement of knowledge around ​​cave microbiology, with implications significant for environmental biotechnology and conservation of underground ecosystems.

Cave Soil Streptomyces sp. strain YC69 Antagonistic to Chilli Fungal Pathogens Exhibits In Vitro Anticancer Activity Against Human Cervical Cancer Cells.

Cancer is one of the fatal diseases and has high mortality worldwide, and the major drawback with the cure is the side effects from the chemotherapeutic agents. The increased multidrug resistance among microbial pathogens is a serious threat to plant and animal health. There is an urgent need for an alternative that can battle against pathogens and can be used for cancer treatment. Presently, actinomycetes were isolated from cave soil, and the crude extract obtained from the potent isolate was analyzed with gas chromatography-mass spectrometry (GC-MS) and high-performance thin layer chromatography (HPTLC) to identify bioactive metabolites. The crude extract was examined for in vitro antimicrobial activity on human pathogens and antifungal activity on plant pathogens. The isolate Streptomyces sp. strain YC69 exhibited antagonistic activity and antimicrobial activity in a dose-dependent manner, with the highest inhibition in Staphylococcus aureus. GC-MS revealed many bioactive compounds, and HPTLC depicted metabolite fingerprints. The antifungal activity exhibited a delayed lag phase in growth curve assay and distorted and collapsed cells of Fusarium oxysporum in scanning electron microscopy (SEM) images. In the MTT assay, the IC50 of 41.98µg/ml against HeLa cells was obtained with clear evidence for deformed cells and blebbing of the cell membrane. The results from the current study suggest that the crude extract from Streptomyces sp. strain YC69 contains antimicrobial metabolites that can inhibit pathogenic microbes in plants and humans. The MTT assay results conclude that further studies on purification may lead to the use of Streptomyces sp. strain YC69 as a source for anti-oncogenic compounds.

Analysis of the Influence of Groundwater Level Fluctuation on Karst Soil Cave Collapse

Artificial water pumping and rainfall will induce groundwater level fluctuations, leading to large-scale karst collapse. Therefore, the combination of physical model test and FLAC3D numerical simulation is adopted to simulate the soil cave collapse caused by three different initial water level fluctuations in this paper. The influence of various initial water level heights on the variation of water-gas pressure, soil pressure of the overlying soil layer, and deformation in the existing soil cave during the fluctuation was analyzed. The relationship between initial water level height, deformation and collapse of the cave, and water-gas pressure was established, and the action law of water level fluctuations on the collapse of soil cave was introduced. The results show the following: (1) The change of water-gas pressure positively correlates with the initial water level height, directly affecting the overlying soil layer deformation. (2) The change of soil pressure of overlying soil positively correlates with the change of water-gas pressure under different initial water level fluctuations. (3) The deformation and collapse difficulty of the soil cave negatively correlates with the initial water level. The higher the initial water level, the stronger the negative pressure absorption and positive pressure gas explosion effect on the overburden on the soil cave and the collapse will occur with fewer water level fluctuations. (4) The numerical simulation results are consistent with the laboratory model test. These laws elucidate the change of water-gas pressure in different initial water level fluctuations and reveal the collapse mechanism of water level fluctuations. It will provide essential theoretical support for further research on the action law of hydrodynamic factors on karst collapse and a scientific and reasonable basis for urban groundwater pumping control, karst and roadbed collapse prevention and prediction.

Application of Long-Range Cross-Hole Acoustic Wave Detection Technology in Geotechnical Engineering Detection: Case Studies of Tunnel-Surrounding Rock, Foundation and Subgrade

The adverse geological conditions of soil cave, karst cave and goaf in deep foundation directly affect the safety and economy of geotechnical engineering construction. It is a difficult problem in geotechnical engineering detection to detect the distribution of bad geological conditions efficiently and accurately. Aiming at the problems of short penetrating distance and low resolution of cross-hole acoustic wave detection in rock-soil mass, based on the characteristics of acoustic wave propagation in rock and soil layers and comprehensively utilizing the spark source and data acquisition device, a long-distance cross-hole acoustic wave detection technology is proposed. According to the indoor concrete model test and field tests of geotechnical engineering, the applicability of the long-distance cross-hole acoustic wave detection technology in the detection of geotechnical structure and adverse geological phenomena under complex geological conditions is verified. The results show that acoustic wave CT imaging can accurately detect the cavities in the indoor concrete model test. In addition, the field tests of the grouting effect of tunnel-surrounding rock, high-rise building foundation and subgrade further verify the rapidity, accuracy and intuitiveness of the long-distance cross-hole acoustic wave detection technology. This work provides a reference for eliminating the potential safety problems caused by adverse geological conditions and similar geotechnical engineering investigation.

A new genus and two new species of chigger mites (Trombidiformes: Leeuwenhoekiidae) from Brazilian caves with notes about the genus Whartonia Ewing, 1944

ABSTRACT The family Leeuwenhoekiidae has a worldwide distribution. In Brazil, it is represented by five genera and 10 species parasitising all groups of terrestrial vertebrates. Examination of material housed in the Acari Collection of the Instituto Butantan revealed undescribed species belonging to this family. In the present study, we describe a new genus, Caramuruacarus gen. nov., with the type species Caramuruacarus carnavalesca sp. nov. from the Minas Gerais State and a new species for the genus Whartonia, Whartonia parauapebensis sp. nov., from Pará State, both from the soil of Brazilian caves. In addition, a discussion of the genus Whartonia and its subgenera is provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:B4D09A27-D163-4772-B4FA-79949D5FEC9F http://www.zoobank.org/urn:lsid:zoobank.org:pub:F3533B72-8643-467F-A348-63534EB67AAA http://www.zoobank.org/urn:lsid:zoobank.org:pub:3BC85F16-1E6D-4FFB-9B71-465A2689D9EE

Characterization and applicability of novel alkali–tolerant carbonatogenic bacteria as environment-friendly bioconsolidants for management of concrete structures and soil erosion

Cracking and erosion are critical factors that reduce the mechanical properties and stability of concrete structures and soil, respectively. They are recognized worldwide as severe disasters causing the collapse of many structures including stone heritage and dams, and landslides. Therefore, it is essential to propose effective and environment-friendly management methods to prevent them. Carbonatogenesis has recently received considerable attention as a reliable biological process for remediating cracks in calcareous structures, stabilizing loose soils, and sequestering CO2 in the environment. Isolating and characterizing carbonatogenic bacteria with excellent performance is crucial for applying this process to the field of environmental and civil engineering. The aim of this study was to isolate new CaCO3–precipitating bacteria and investigate various properties for their use as bioconsolidants. Furthermore, the possibility of restoring damaged structures and stabilizing loose sandy soil using isolated strain was investigated. Strain LC13 with urease and CaCO3–precipitating activity was isolated from limestone cave soil in Korea and identified as Arthrobacter sulfureus by phenotypic characterization and 16S rRNA gene analysis. Although cell growth was observed after an adaptation period at pH 11, strain LC13 grew well at pH 7–11, indicating alkali tolerance. The optimal conditions for CaCO3 precipitation were 1.0% yeast extract, 2.5% urea, 0.35% NaHCO3, and 400 mM CaCl2, with an initial pH of 6.5 at 30 °C. Under optimized conditions, maximal CaCO3 (22.92 ± 0.14 g/l) precipitated after 3 days, which was 10.8–fold higher than the value in a urea–CaCl2 medium. CaCO3 precipitation by strain LC13 was associated with an increased pH due to ureolysis and protein deamination. Using an optimized medium as a cementation solution, strain LC13 completely remediated 340–760 μm wide cracks over 3 days, and also restored the spalling of concrete surfaces. Furthermore, the sand treated with LC13 solidified with a surface strength of 14.9 kPa. Instrumental analysis confirmed that the crystals precipitated were a mixture of CaCO3 polymorphs composed of rhombohedral calcite and spherical vaterite. These results suggest that A. sulfureus LC13 may be useful for implementing sustainable biorestoration and environmental management technologies such as the in situ remediation of structural cracks and in situ prevention of soil erosion.

Diversity and Composition of Methanotroph Communities in Caves.

ABSTRACTMethane oxidizing microorganisms (methanotrophs) are ubiquitous in the environment and represent a major sink for the greenhouse gas methane (CH4). Recent studies have demonstrated methanotrophs are abundant and contribute to CH4 dynamics in caves. However, very little is known about what controls the distribution and abundance of methanotrophs in subterranean ecosystems. Here, we report a survey of soils collected from > 20 caves in North America to elucidate the factors shaping cave methanotroph communities. Using 16S rRNA sequencing, we recovered methanotrophs from nearly all (98%) of the samples, including cave sites where CH4 concentrations were at or below detection limits (≤0.3 ppmv). We identified a core methanotroph community among caves comprised of high-affinity methanotrophs. Although associated with local-scale mineralogy, methanotroph composition did not systematically vary between the entrances and interior of caves, where CH4 concentrations varied. We also observed methanotrophs are able to disperse readily between cave systems showing these organisms have low barriers to dispersal. Lastly, the relative abundance of methanotrophs was positively correlated with cave-air CH4 concentrations, suggesting these microorganisms contribute to CH4 flux in subterranean ecosystems.IMPORTANCE Recent observations have shown the atmospheric greenhouse gas methane (CH4) is consumed by microorganisms (methanotrophs) in caves at rates comparable to CH4 oxidation in surface soils. Caves are abundant in karst landscapes that comprise 14% of Earth’s land surface area, and therefore may represent a potentially important, but overlooked, CH4 sink. We sampled cave soils to gain a better understand the community composition and structure of cave methanotrophs. Our results show the members of the USC-γ clade are dominant in cave communities and can easily disperse through the environment, methanotroph relative abundance was correlated with local scale mineralogy of soils, and the relative abundance of methanotrophs was positively correlated with CH4 concentrations in cave air.

Nutrient-limited subarctic caves harbour more diverse and complex bacterial communities than their surface soil

BackgroundSubarctic regions are particularly vulnerable to climate change, yet little is known about nutrient availability and biodiversity of their cave ecosystems. Such knowledge is crucial for predicting the vulnerability of these ecosystems to consequences of climate change. Thus, to improve our understanding of life in these habitats, we characterized environmental variables, as well as bacterial and invertebrate communities of six subarctic caves in Northern Norway.ResultsOnly a minuscule diversity of surface-adapted invertebrates were found in these caves. However, the bacterial communities in caves were compositionally different, more diverse and more complex than the nutrient-richer surface soil. Cave soil microbiomes were less variable between caves than between surface communities in the same area, suggesting that the stable cave environments with tougher conditions drive the uniform microbial communities. We also observed only a small proportion of cave bacterial genera originating from the surface, indicating unique cave-adapted microbial communities. Increased diversity within caves may stem from higher niche specialization and levels of interdependencies for nutrient cycling among bacterial taxa in these oligotrophic environments.ConclusionsTaken together this suggest that environmental changes, e.g., faster melting of snow as a result of global warming that could alter nutrient influx, can have a detrimental impact on interactions and dependencies of these complex communities. This comparative exploration of cave and surface microbiomes also lays the foundation to further investigate the long-term environmental variables that shape the biodiversity of these vulnerable ecosystems.

Isolation and identification of Streptomyces tunisiensis from Garmsar salt cave soil with antibacterial and gene expression activity against Pseudomonas aeruginosa

It is known that more than 70% of the current antibiotics have been produced by Streptomyces; therefore, the main goal of the present study was to isolate halophiles Streptomyces to investigate their antimicrobial properties on the expression of the pathogenic genes of clinically resistant Pseudomonas aeruginosa. To this aim, isolation of Streptomyces from soil was performed by serial dilution method, and cultivation on ISP2 and SCA medium. The secondary metabolite was extracted by ethyl acetate method. The presence of exo A, alg D and oprl genes were determined by PCR in 50 clinical isolates of Pseudomonas aeruginosa. The inhibitory effect of active metabolites on gene expression were investigated by employing the real-time PCR technique. The purification of secondary metabolites were performed by employing the HPLC technique. Moreover, the FTIR technique was employed to determine the functional groups to help performing identifications by employing the LC-MS technique. Finally, selected Streptomyces was identified by 16S ribosomal RNA gene. Accordingly, the possible forms of Streptomyces were isolated and identified, in which Streptomyces number 25 had the highest growth inhibition zone against the clinical strains of Pseudomonas aeruginosa. The obtained results of molecular analysis showed 95.4% similarity to Streptomyces tunisiensis. The effect of selected Streptomyces secondary metabolites reduced expressions of both of exo A and algD genes in 1024μg/mL concentration. In this regard, the potent fraction could be known as an isobutyl Nonactin analogue. The concluding remarks of this work showed the antimicrobial activity of halophilus Streptomyces species against the resistant strains of Pseudomonas aeruginosa with the ability of producing antibiotics proposing for running further investigations to determine the active compound structures.

Environmental DNA of insects and springtails from caves reveals complex processes of eDNA transfer in soils

Subterranean environments host a substantial amount of biodiversity, however assessing the distribution of species living underground is still extremely challenging. Environmental DNA (eDNA) metabarcoding is a powerful tool to estimate biodiversity in poorly known environments and has excellent performance for soil organisms. Here, we tested 1) whether eDNA metabarcoding from cave soils/sediments allows to successfully detect springtails (Hexapoda: Collembola) and insects (Hexapoda: Insecta); 2) whether eDNA mostly represents autochthonous (cave-dwelling) organisms or it also incorporates information from species living in surface environments; 3) whether eDNA detection probability changes across taxa with different ecology. Environmental DNA metabarcoding analyses detected a large number of Molecular Operational Taxonomic Units (MOTUs) for both insects and springtails. For springtails, detection probability was high, with a substantial proportion of hypogean species, suggesting that eDNA provides good information on the distribution of these organisms in caves. Conversely, for insects most of MOTUs represented taxa living outside caves, and the majority of them represented taxa/organisms living in freshwater environments (Ephemeroptera, Plecoptera and Trichoptera). The eDNA of freshwater insects was particularly abundant in deep sectors of caves, far from the entrance. Furthermore, average detection probability of insects was significantly lower than the one of springtails. This suggests that cave soils/sediments act as “conveyer belts of biodiversity information”, possibly because percolating water lead to the accumulation of eDNA of organisms living in nearby areas. Cave soils hold a complex mix of autochthonous and allochthonous eDNA. eDNA provided unprecedented information on the understudied subterranean cave organisms; analyses of detection probability and occupancy can help teasing apart local eDNA from the eDNA representing spatially-integrated biodiversity for whole landscape.

Analysis of the Influence of the Distribution and Development of Soil Caves on the Stability of High‐Voltage Transmission Tower Foundations

As a kind of concealed flawed geology, karst geology easily forms soil caves, which may have a negative effect on adjacent transmission tower foundations. Since soil caves are continuously developed when surface water flows through soil, or groundwater levels fluctuate, the effect of soil caves on transmission lines in power transmission engineering needs to be investigated. In this paper, combined with an engineering case in western Hubei, first, FLAC3D finite element software is used to analyze the influence of a single underground soil cave during continuous development and expansion on 500 kV transmission towers. Considering the maximum allowable tilt value of the tower foundation, the stress state and deformation of the soil around the foundation are monitored during the calculation and analysis, and the maximum allowable radius of the soil cave in different positions is obtained. For example, the development radii of soil holes are 1.5 m, 2 m, and 2.5 m for burial depths of 7 m and 8 m, 9 m, and 10 m and 11 m, respectively, and the development radius of soil holes with a burial depth of 12 m and below can reach the maximum value of 3 m under actual working conditions. Then, the results of two simplified models of columnar and spherical development of the soil cave are compared, and it is found that columnar development is more in line with the actual situation. Finally, under the condition of a close‐range double soil cave distribution, the influence of the size, depth, and gap between the two caves on the tower foundation is simulated. This study can provide references for the safe operation of transmission towers and the assessment of possible disasters in karst areas.

喀斯特洞穴小型土壤节肢动物多样性

PDF HTML阅读 XML下载 导出引用 引用提醒 喀斯特洞穴小型土壤节肢动物多样性 DOI: 10.5846/stxb202008122104 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然基金项目（31760130）；贵阳市财政支持贵阳学院学科建设与研究生教育项目（SH-2020）；贵州省教育厅创新群体项目（黔教合KY字[2021]013号）；贵州省贵阳学院院士工作站项目（黔科合平台人才[2019]5605） Diversity of cave soil microarthropod in karst region Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究洞穴土壤节肢动物，有助于了解土壤节肢动物对特殊环境的响应，对于深入认识喀斯特生态过程具有重要意义。以喀斯特洞穴生态系统小型土壤节肢动物为研究对象，采用主成分分析、重复测量方差分析、相关性分析和冗余分析等方法探讨了小型土壤节肢动物与环境因子的相互作用关系。调查共获得小型土壤节肢动物2399个，隶属7纲15目121科。其中，自然林优势类群为等节跳科（Isotomidae），洞穴优势类群为奥甲螨科（Oppiidae）。PCA分析显示，洞穴与自然林小型土壤节肢动物群落组成差异明显。洞穴小型土壤节肢动物类群数、密度和Shannon-Wiener指数（H'）显著低于自然林（P<0.05），自然林小型土壤节肢动物类群数、密度和Shannon-Wiener指数（H'）季节差异显著（P<0.05），洞穴类群数、密度和Shannon-Wiener指数（H'）季节差异不明显。相关性分析结果表明，小型土壤节肢动物类群数和Shannon-Wiener指数（H'）与pH值、全磷和光照强度显著相关（P<0.05），密度与pH值、全磷、有机质和光照强度显著相关（P<0.05）。RDA分析表明，土壤pH值是影响小型土壤节肢动物多样性的最主要因子。研究结果表明，小型土壤节肢动物多样性受生境类型的影响，洞穴生态系统生境脆弱，稳定性差，不利于小型土壤节肢动物的生存。因此，应该加强洞穴生物多样性保护，避免不合理的开发利用。 Abstract:Karstic cave is a special closed ecosystem, with environmental condition significantly distinct from common ecosystem types, and it is considered an ideal place to study karst ecological processes. Soil arthropod is a critical component of terrestrial ecosystem, and highly sensitive to environmental changes and even small variation in ambient environmental condition has severe consequence on their community composition and diversity, so exploring the cave soil arthropod is helpful to understand the response of soil arthropod to special environment, and is of great significance for better understanding of ecological processes in karst areas. In this study, two habitats types (cave and natural forest) were selected in south Guizhou and soil microarthropod were investigated using Tullgren methods in May, July, October 2018 and January 2019, and principal component analysis(PCA), Repeated measures ANOVA, Pearson's correlation test and redundancy analysis (RDA) were used to examine the interaction between soil microarthropod and environmental factors. A total of 2399 soil microarthropod specimens were captured and classified into 7 classes, 15 orders, and 121 families. Among them, the dominant group was Isotomidae in natural forest, Oppiidae in cave, accounting for 12.09% and 20.79% of the total density, respectively. PCA demonstrated that the structural composition of soil microarthropod communities differed markedly between the cave and natural forest. The group number, density and Shannon-Wiener index(H') in the different habitats showed that these indicators were significantly lower in the cave than those in the natural forests (P<0.05). The group number, density and Shannon-Wiener index(H') of the soil microarthropod had an obvious seasonal variation in natural forests (P<0.05), while these indicators in the cave showed no significant seasonal fluctuation. Pearson correlation analysis indicated that group number and Shannon-Wiener index(H') of the soil microarthropod were significantly correlated with pH, TP and light intensity, and density was correlated significantly with pH, TP, SOM and light intensity (P<0.05). RDA revealed that pH value was the main environmental factor affecting the diversity of the soil microarthropod community. All results showed that diversity of soil microarthropod is significantly influenced by habitat types. Cave ecosystem is extremely fragile, unstable and unfavorable for soil microarthropod survival. Therefore, we should strengthen protection of cave biodiversity, and avoid unreasonable development and utilization of cave. 参考文献 相似文献 引证文献

An Applied Study On Safety Warning Distance With Numerical Simulation For The Development And Management Of Subway Tunnels In Karst Area

If lacking scientific and rational planning and management when underground engineering is developed karst collapse risk area, it will bring immeasurable losses to subway construction, operation and disaster relief. To this end, this paper puts forward the concept of “Safety Warning Distance”. According to the final collapse form of karst soil cave-funnel-shaped collapse influence area, the critical slope angle β is proposed in the subway tunnels risk section “Red Line of Safety Warning”. Then the critical safety warning distance safe asafe is calculated by FLAC 3D numerical simulation of the boundary scale of karst soil cave when it finally collapses. This research method can provide a safe and reliable scientific reference for future subway Line adjustment, construction, operation and disaster relief.

The Influence of Groundwater on the Development of Soil Cave����A Case Study of a Project in Yugan County

The Influence of Groundwater on the Development of Soil Cave����A Case Study of a Project in Yugan County

Fruit wrapping kraft coated paper promotes the isolation of actinobacteria using ex situ and in situ methods

Designing novel isolation methods could enhance the diversification of the available bacterial strains to biotechnology. In this study, the new ex situ and in situ cultivation methods are introduced for the isolation of actinobacteria. In the ex situ experiments, the soil suspension was spread on the isolation media located above some ordinary papers in immediate contact with the slurry of soil substrate and incubated for 16weeks. The paper was wholly immersed in the cave soil for in situ cultivations, and the containers were buried under layers of soil in Hampoeil cave for 10weeks. Fruit wrapping kraft coated paper, with 68.8% recovery of isolates, was a better choice in isolation of actinobacteria than other studied filter paper. Based on the molecular identification results, 19% of the isolates obtained from the in situ cultivation method had less than 98.5% similarity to known taxa of actinobacteria and potentially may represent new species. In contrast, in the standard cultivation method, 1.3% of the isolates had less than 98.5% similarity 16Sr RNA gene. This data shows that the introduced cultivation method is a promising technique for isolating less culturable or new actinobacteria.

Detection Methods for Unfavorable Geology and Soil Caves before Grouting in Karst Terrains

Detection Methods for Unfavorable Geology and Soil Caves before Grouting in Karst Terrains

Study on Ground Collapse of Covered Karst Soil Caves by Sudden Drop of Groundwater

In this study, the ellipsoidal soil cave with vertical collapses in the covering karst area is studied. Based on certain assumptions, the mechanical model of karst collapse caused by groundwater drop was established. Then, based on the negative pressure calculation formula of soil cave cavity according to Boyle–Mariotte’s law, the expression of the stability coefficient of the soil cave was proposed. Subsequently, the feasibility of the theoretical formula was verified. The calculation example analyzed the relationship of groundwater parameters and overburden thickness. The results show that when the initial groundwater level is higher than the top of cave, the law between the stability coefficient of soil cave and groundwater drawdown shows the jumping horizontal broken line. Thus, soil cave tends to collapse when the falling groundwater level drops over the vault; when the initial groundwater level ranges from the bottom to the top of the cave body, the stability coefficient and groundwater drawdown show a negative correlation law, the curve is steep at the early stage and then becomes gentle at the latter stage, and the higher the initial groundwater level in the cave is, the greater stability coefficient of soil cave reduces; when the initial groundwater level is lower than the bottom of the cave, the effect of drawdown is limited. In addition, for the small drawdown or low initial groundwater level, the stability coefficient of soil cave first decreases and then increases with the increases in thickness of overburden, and the thinner the overburden is, the greater the drawdown rate is; when the drawdown or the initial groundwater level is higher, the stability coefficient of soil cave positively relates to the thickness of the overburden layer.