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过刊目录

  • 2023年, 20卷, 第06期
    刊出日期：2024-06-19
      
  • 全选
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  • Eastern Siberia permafrost transect(ESPT).A first stage:The Verkhoyansk Range part
    Robert SYSOLYATIN, Svetlana KALINICHEVA, Alexander FEDOROV, Maria ROZHINA
    2023, 20(06): 1499-1507.
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    Environmental and geomorphological processes in the mountainous areas of Eastern Siberia is strongly conditioned by the thermal state of permafrost(permanently frozen ground). However, the scarce data about climate and weak of permafrost study have led to the unclarity of mountain permafrost condition in this region. The increase in the mean annual air temperature over the past 50 years in the northeastern Siberia by various estimates is from 1.1℃ to 3.3℃. So far, almost no information is available on the permafrost response to climatic changes in the region. The Kolyma Route(around 2000 km length), connecting Yakutsk and Magadan that crosses 5 climatic types and more than 10 permafrost landscapes, so it seems a suitable path for establishing basic(reference) monitoring sites. From 12 target boreholes, on the first stage 5 boreholes up to 30 m in depth were drilled and instrumented for measuring temperature at sites adjacent to weather stations in the Verkhoyansk Range from 283 to 1288 m a.s.l. Here we present conception, purpose, and methods for permafrost study project with first preliminary results from the highest weather station of the East Siberia Mountain. The following research about geophysical investigations, permafrost landscape description, mapping and spatial modelling, numerical computing, physical modelling of permafrost thickness might be initiated by the Eastern Siberia Permafrost Transect(ESPT)-project.
  • Assessment of the spatial extent of permafrost in the Upper Indus Basin(UIB)
    Wasim HASSAN, G.JEELANI, A.P.DIMRI, Marcus NüSSER
    2023, 20(06): 1508-1525.
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    Climate change differentially influences the frozen ground, a major dynamic component of the cryosphere, on a local and regional scale. Under the warming climate with pronounced effects reported at higher altitudes, the characterization of the frozen ground is very important in the Upper Indus Basin(UIB), an important and critical region with respect to climate and hydro-glaciological dynamics. In this study, the efficiency and reliability of the surface frost number model are assessed in delineating the spatial extent of different classes of frozen ground in the region. The daily MODIS land surface temperature(LST) with ground surface temperature(GST) and surface geomorphological expressions as ground validation datasets are used jointly in efficiently determining the extent of different classes of frozen ground(continuous and discontinuous permafrost and seasonal frost). The LST and GST resonate with each other in the annual cycle of temperature variation, however, with mean annual LST exhibiting an offset(cold bias) of 5 to 7℃ relative to mean GST. This study shows that the highest permafrost extent is observed in areas where the lowest thinning rates of glacier ice are reported and vice versa. The surface frost number model categorizes an area of 38% ± 3% and 15%± 3% in the UIB as permafrost and seasonal frost, respectively. Based on the altitude model, the lower limit of alpine permafrost is approximated at a mean altitude of 4919 ± 590 m a.s.l. in the UIB. The present study acts as preliminary work in the data sparse and inaccessible regions of the UIB in characterizing the frozen and unfrozen ground and may act as a promising input data source in glaciohydro-meteorological models for the Himalaya and Karakoram. In addition, the study also underlines the consideration of this derelict cryospheric climatic variable in defining and accounting for the sustainable development of socio-economic systems through its intricate ramification on agricultural activity, landscape stability and infrastructure.
  • Species richness and similarity of the flora on four lajedos in Boa Nova, Bahia, Brazil
    Morgana Maria DO CARMO BARBOSA, Anderson FERREIRA PINTO MACHADO, Andrea Karla ALMEIDA DOS SANTOS, Raymundo José DE Sá-NETO, Michele MARTINS CORRêA
    2023, 20(06): 1526-1539.
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    The municipality of Boa Nova, in northeastern Brazil, is in an ecotone zone between the Caatinga and Atlantic Forest phytogeographic domains. The transition phytophysiognomy is seasonal forest and known locally as mata de cipó. In these phytophysiognomies there are lajedos, which are rock outcrops colonized by vegetation welladapted to extreme microclimatic variation and vegetation diversity is affected by the vegetation types of the surrounding areas. Due to the singularity of these environments and the relevance of floristic studies for conservation, this work aimed to identify the species richness and compare the similarity of the flora on four rock outcrops in Boa Nova. The flora was surveyed during exploratory walks along lajedos between 2016 and 2019. In total, 162 species were identified on the Boa Nova outcrops. The flora has a composition and structure similar to semiarid outcrops, as well as endemic species that also occur in surrounding phytophysiomies. Despite the proximity, a similarity index revealed there is floristic dissimilarity between the areas. Nine new occurrences were recorded for the region, five species are threatened with extinction(Aosa gilgiana, Ficus cyclophylla, Hippeastrum stigmovittatum, Pleroma caatingae and Trixis pruskii), and 43 species are common in anthropogenic areas. This reinforces the importance of actions to conserve these areas.
  • Critical thresholds for stage division of water erosion process in different ridge systems in mollisol region of Northeast China
    JIAO Jian, QIN Wei, LI Kun-heng, XU Hai-chao, YIN Zhe, HOU Shu-yan
    2023, 20(06): 1540-1560.
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    Extreme rainfall events on a slope under ridge tillage systems cause concentrated stream soil loss. To analyse the critical thresholds for different stages of water erosion process of ridge systems, simulated rainfall-erosion experiments for the contour wide ridge(CWR), contour narrow ridge(CNR), longitudinal wide ridge(LWR), and longitudinal narrow ridge(LNR) were conducted under four rainfall intensities, with slope gradients of 3° and 5°. For the runoff event, the runoff depth order was LNR > LWR > CWR > CNR; the soil loss order was CNR > LNR > CWR > LWR. The product of slope factor(S) and rainfall erosivity(R) or runoff depth(D), can be adopted as critical thresholds for different stages of runoff and soil erosion process. For the longitudinal ridge systems, R values were provided for LWR and LNR and were the beginning of sheet flow, whereas the product of rainfall erosivity and slope factor(RS) values were provided for LWR and LNR as the beginning of the accelerated concentrated flow. For the contour ridge systems, R values were provided for CWR and CNR as critical thresholds for the beginning of overflow. The product of runoff depth and slope factor(DS) values were 9.98 and 7.73 mm for CWR and CNR, respectively, and were critical thresholds for the beginning of ridge failure; the DS values were 18.45 and 12.75 mm for CWR and CNR, respectively, and were critical thresholds for the beginning of the formation of ephemeral gully erosion. The critical thresholds can distinguish different stages of soil erosion process modelling.
  • Effects of phosphorus fertilizer application rate on transformation processes of phosphorus fractions in the purple alluvial soil of a riparian zone
    HE Li-ping, JIA Kai-tao, LIU Dan, WANG Ke-hong, DUAN Lin-Yan, LIN Jun-jie
    2023, 20(06): 1561-1574.
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    Effects of phosphorus(P) fertilizer application rate on soil transformation processes of P fraction are still unclear in the riparian zone. Purple alluvial soils in the riparian zone of the Three Gorges Reservoir were collected to conduct a 21-day incubation executed by two hydrological environments(drying and flooding) and ten application rates of P fertilizer. Transformation percentages of P fertilizer(TPPF) were calculated as content differences of soil P fractions between fertilizer addition and none fertilizer addition divided by soil total P increases caused by fertilizer addition. TPPF to inorganic P extracted by sodium hydroxide(NaOH-Pi) and hydrochloric acid(HCl-Pi) increase by 20.91%(9.71%) and 24.26%(40.72%) under the drying(flooding) environment. Instead, TPPF to the other fractions decrease. Phosphorus fertilizer input mainly has indirect positive and negative effects on organic P via precipitated P under the drying and flooding environments and finally has indirect positive effects on labile P(p<0.001). Percentage changes of water-soluble inorganic P(H_2O-Pi) and HCl-Pi under the flooding environment are higher than that under the drying environment, and percentage changes of organic P extracted by sodium hydrogen carbonate(Na HCO_3-Po) and NaOH-Pi show an opposite trend(p<0.01). ?(differences in soil P fraction content between flooding and drying incubations) H_2O-Pi is negatively correlated with ?NaHCO_3-Po, and ?NaHCO_3-Po is positively correlated with ?NaOH-Pi(p <0.001). In conclusion, P fertilizer is transformed more into precipitated P than into other P fractions with an application rate increase. Phosphorus fertilizer input mainly increases organic P via precipitated P under the drying environment and decreases organic P via precipitated P under the flooding environment, and organic P is further transformed into labile P. With P fertilizer input, P release caused by flooding is derived from NaHCO_3-Po release triggered by NaOH-Pi release. The results can be helpful for the understanding of P fertilizer migration processes from the riparian zone soil to the Three Gorges Reservoir under rain leaching and flooding.
  • Intensities of human disturbance dictate the floral diversity in tropical forest:the case of a secondary forest in Benguet, Philippines
    Domelson A.BALANGEN, Melchor S.CATONES, Jane M.BAYENG, Jones T.NAPALDET
    2023, 20(06): 1575-1588.
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    This study inventoried the floral diversity of a secondary forest in Tuba, Benguet, Philippines as affected by different intensities of human disturbance. This study is unique from other land use studies in Southeast Asia in having conventional farms as the most disturbed land use while other sites have oil palm plantations. A total of 267 species belonging to 222 genera and 78 families was documented. Results showed that the level of human disturbance is the major factor affecting the floral diversity while the effect of elevation is secondary. The level of human disturbance is significantly associated with species richness, species composition, dominant species and biodiversity indices. Greater human disturbance, as in the case of conventional farms, results in lower species richness, predominantly weed composition, dominant weed species and lower biodiversity indices. On the other hand, lesser human disturbance(as in the case of secondary forest) leads to higher species richness, greater native species composition, dominance of indigenous species, and higher diversity indices. The most disturbed land use experienced the greatest loss of species richness, change in floristic composition and vegetation structure, as well as a shift from native to alien-dominated plant communities. These results showed that the effect of land use change is not limited to species richness but also to species composition, dominant species and biodiversity indices. Locally, the study is an important baseline data for biodiversity conservation of the Marcos Highway Watershed Forest Reserve.
  • Large-scale characteristics of thermokarst lakes across the source area of the Yellow River on the Qinghai-Tibetan Plateau
    LIU Wen-hui, ZHOU Guang-hao, LIU Hai-rui, LI Qing-peng, XIE Chang-wei, LI Qing, ZHAO Jian-yun, ZHANG Qi
    2023, 20(06): 1589-1604.
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    As significant evidence of permafrost degradation, thermokarst lakes play an important role in the permafrost regions by regulating hydrology, ecology, and biogeochemistry. In the Sources Area of the Yellow River(SAYR), permafrost degradation has accelerated since the 1980s, and numerous thermokarst lakes have been discovered. In this paper, we use Sentinel-2 images to extract thermokarst lake boundaries and perform a regional-scale study on their geometry across the permafrost region in the SAYR. We also explored the spatiotemporal variations and potential drivers from the perspectives of the permafrost, climate, terrain and vegetation conditions. The results showed that there were 47,518 thermokarst lakes in 2021 with a total area of 190.22×10~6 m~2, with an average size of 4,003.3 m~2. The 44,928 ponds(≤10,000 m~2) predominated the whole lake number(94.1%) but contributed to a small portion of the total lake area(28.8%). With 2,590 features(5.9%), small-sized(10,000 to 100,000 m~2) and large-sized lakes(>100,000 m~2) constituted up to 71.2% of the total lake area. Thermokarst lakes developed more significantly in warm permafrost regions than in cold permafrost areas; 74.1% of lakes with a total area of 119.6×10~6 m~2(62.9%), were distributed in warm permafrost regions. Most thermokarst lakes were likely to develop within the elevation range of 4,500～4,800 m, on flat terrain(slope<10°), on SE and S aspects and in alpine meadow areas. The thermokarst lakes in the study region experienced significant shrinkage between 1990 and 2021, characterized by obvious lake drainage; the lake numbers decreased by 5418(56.1%), with a decreasing area of 58.63×10~6 m~2(49.0%). This shrinkage of the thermokarst lake area was attributable mainly to the intensified degradation of rich-ice permafrost thawing arising from continued climate warming, despite the wetting climatic trend.
  • Numerical simulation of rockburst disaster and control strategy of constant resistance and large deformation anchor cable in Gaoloushan tunnel
    MIAO Cheng-yu, JIANG Ming, LI Zhi-hu, SUN Xiao-ming, ZHANG Tong, ZHANG Yong, YANG Jin-kun, REN Chao, SONG Peng
    2023, 20(06): 1605-1619.
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    The Gaoloushan Tunnel in Longnan City, Gansu Province, China, frequently experiences rockburst disasters due to high in-situ stress. Managing rockburst in deep-buried tunnels remains a challenging issue. This paper employs RFPA(Rock Failure Process Analysis) software to establish a calculation model of constant resistance and large deformation(CRLD) anchorages and analyzes the effects of different support methods and pre-stress levels on rockburst. We simulate the process of tunnel rockburst disasters and find that ordinary anchor support incurs rockburst on the right arch waist and arch top, forming a V-shaped explosion pit. CRLD anchor support has several advantages in rockburst control, such as more uniform stress distribution in the surrounding rock, a uniform distribution of plastic zones, less noticeable damage to the tunnel, and effective control of the arch top displacement. The effectiveness of the CRLD anchor support under varying pre-stress conditions shows that a higher prestress results in a smaller plastic zone of the surrounding rock and arch top displacement and a lower number of acoustic emission signals, which better explains the excavation compensation effect. Moreover, adding long anchorages in the deep surrounding rock area can better control rockburst and reduce surrounding rock deformation. Based on these findings, we propose a comprehensive control system that combines long and short anchorages and provides the optimal scheme based on calculations. Therefore, by using high-prestress CRLD anchor support and the combination of long and short anchorages at critical positions, we can enhance the integrity of the surrounding rock, effectively absorb the energy released by the surrounding rock deformation, and reduce the incidence of rockburst disasters.
  • Wireless remote spatiotemporal monitoring of high-fill foundation deformation
    YANG Xiao-hui, LI Zhi-qian, ZHU Yan-peng, GUO Nan
    2023, 20(06): 1620-1638.
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    The spatial and temporal deformation patterns and deformation control indicators of highfill foundations directly affect the design, construction and operational safety of high-fill projects. In situ monitoring can comprehensively reflect the deformation of high-fill during and after construction. In this paper, we have first designed and installed an integrated wireless remote monitoring system for high-fill to achieve real-time dynamic monitoring of settlement, pore water pressure and soil pressure of the fill foundation. Based on the monitoring results of nearly one year of the construction period and two years after construction, it was found that the deformation amount and deformation rate of the high-fill foundation showed a non-linear growth relationship with the filling rate and filling height. The settlement deformation of the high-fill foundation during the loading period was mainly dominated by the original foundation soil, accounting for 54.4% of the total settlement on average; the settlement deformation during the post-construction period was mainly dominated by the filling body, accounting for 77.04% of the total settlement on average, and the settlement deformation during the post-construction period mainly occurred in the first year after construction. The analysis of the deformation mechanism suggests that the deformation of the filling body is dominated by exhaust consolidation during the loading period and drainage consolidation during the post-construction period; the deformation of the original foundation soil is dominated by drainage consolidation during the loading period and drainage consolidation develops slowly during the post-construction period. It is recommended that the original foundation should be reinforced before the large area filling construction, and that the filling rate should be strictly controlled during construction. The research results can provide a scientific basis for deformation calculation and stability assessment of high-fill foundations.
  • A framework for identifying the onset of landslide acceleration based on the exponential moving average(EMA)
    WANG Jia-zhu, JU Neng-pan, TIE Yong-bo, BAI Yong-jian, GE Hua
    2023, 20(06): 1639-1649.
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    Predicting the failure time of a landslide is considered as challenging work in the field of landslide research, and inverse velocity is proved to be an effective and convenient method. The onset of acceleration(OOA) has a crucial effect on the prediction failure time from the inverse velocity method. However, a simple method to identify OOA points is lacked, and most of the identifications rely on expert experience. Therefore, this study presents an application of a simple framework developed to identify the OOA by analyzing monitoring velocity data in three steps, including selection of the absolute value of velocity, reliable area identification and OOA identification. A new parameter based on exponential moving average(EMA) is developed to identify the landslide OOA. The framework is applied to three historical case studies to test its practicability and effectiveness. The forecasting results show a good correspondence between the accuracy rate and the coefficient of determination(R~2). The predicted failure time according to the linear extrapolation starting from the identified OOA points is acceptable with a high R~2 and high accuracy.
  • Spatiotemporal distribution of regional landslides and erosion rates in Southeastern Tibet
    WANG Xue-liang, SUN Juan-juan, WANG Shan-shan, QI Sheng-wen, ZHAO Hai-jun, GUO Song-feng, WANG Xin-hui
    2023, 20(06): 1650-1659.
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    The difficulty in estimating ages of regional landslides hampers to assess frequency of landslides and hence to quantitatively assess regional landslide hazard. In this study, we used radiocarbon dating of organic sediment on boulder rock varnish to estimate landslide ages in Langxian(LX) arid region in southeastern Tibet. Samples of rock varnish with organic sediment were collected on site for radiocarbon dating, leading to landslide ages from 1880 ± 30 to 18,430 ± 30 yr B.P. To measure surface roughness characteristics of 109 remotely-mapped large bedrock landslide deposits, we estimated average standard deviation of slope(SDS) over an area of ～640 km~2 by calculating the slope gradient of each raster cell and using a rectangular moving window method in Arc Map from a 5 m-resolution Digital Elevation Model generated from helicopterobtained photographs. Combing estimated landslide ages(t) with average surface roughness of mapped landslide deposits(R) quantified by SDS, we fit an exponential landslide deposits surface roughness-age function(t=1.47×10~6×e~(-1.46R), r~2=0.63) that was used to estimate regional landslide ages in LX. We conclude that three periods with clusters of regional landslides in LX were revealed by different surface roughness of landslide deposits combing roughness-age function, with the values of 5563-7455 yr B.P., 1724-4151 yr B.P., and 960-1287 yr B.P.. Furthermore, we used our estimates of landslide ages to quantify landslide erosion rates of three corresponding hillslopes in LX ranging from 0.50 to 2.42 mm yr~(-1). Although rock varnish radiocarbon dating provides us a feasible option for timing regional landslides of arid regions, the epistemic uncertainty in the dating method should arouse our attention, which could be reduced by increasing the number of samples.
  • Sediment sources and their impacts on a check dam-controlled watershed, Loess Plateau, China
    BAI Lu-lu, SHI Peng, WANG Wen, LI Zhan-bin, YU Kun-xia, LI Peng, CUI Ling-zhou, SHEN Rong-jian, GUAN Mu-hong, DU Xin-chun, ZHANG Xun-le, CHEN Wen-fu
    2023, 20(06): 1660-1673.
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    Soil erosion is a major issue in Loess Plateau, China, and quantitative analyses of sediment sources are crucial for soil erosion control. In this study, a combination of flood couplet analysis and composite fingerprint identification was used for historical reconstructions of soil erosion in sediment source areas in Loess Plateau. Each flood couplet was constructed based on sediment 137Cs activity, and past soil erosion was calculated using soil bulk density and storage capacity curves. The contribution rates of the sediment sources were calculated using the fingerprinting method, and the amount of erosion in the sediment source areas was estimated. The best fingerprint combination(Cr, Ni, V, and TOC) enabled a 97.2% recognition of sediment sources from 29 flood events(1956–1990) in the Loess Plateau. The contribution rates of gullies, farmland, grassland, and shrubland were 44.89%, 26.38%, 10.49%, and 18.24%, respectively. These four land use types contributed 1,227, 751, 512, and 279 tons of sediments, respectively. Re-vegetation decreased soil erosion(1966–1983), whereas deforestation increased soil erosion(1956–1965 and 1984–1990). Rational soil and water conservation measures on slopes and check dam construction in gullies are therefore suggested to mitigate erosion.
  • Insights into the long-term stability of landslide dams on the eastern margin of the Tibetan Plateau, China——A case study of the Diexi area
    SONG Liang, WANG Yun-sheng, HU Dong-yu, WU Hao-chen, TANG Tao, LIU Shi-cheng
    2023, 20(06): 1674-1694.
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    Landslide dams, especially long-term stable landslide dams, have been recognized as important contributors to regional geomorphological evolution. Here, the Diexi area, a long-term stable dam-prone area located in upstream of the Minjiang River on the eastern Tibetan Plateau, was adopted to reveal reasons that landslide dams are concentrated in this area and maintain long-term stability via detailed field investigations, landslide dam sampling, unmanned aerial vehicle(UAV) images, and digital surface models(DSM). The results show the controlling factors that the slopes are prone to sliding and rock mass structure deterioration including lithological combination mode, slope structure, topographic conditions, a series of NNE-trending radial fissures and hydrological conditions. Fault activities, which have caused many earthquakes, are the main inducing factor. Landslide dams are prone to occurrence in the Diexi area owing to the combined effect of the narrow channels, the large landslide dam volume and the rock fragments. The river flow, and the landslide dam volume, material, structure, and parameters control the stability of landslide dams. The landslide dam consists of various sizes of boulders and all landslide dams exhibit an obvious inverse grading sequence, and this size combination could consume most of the flow energy, and consequently protect the dam from incision. Additionally, a total of seven knickpoints were formed by landslide dams, and the longitudinal gradient upstream of every landslide dam was found to decrease by the action of knickpoint. In the eastern margin of the Tibetan Plateau, there are numerous landslide dams existed for hundreds or thousands of years. Studies on the long-term stable landslide dams in the Diexi area could provide experience for studying similar kinds of landslide dams in this region.
  • Geohazards and risk assessment along highway in Sichuan Province, China
    YANG Hong-zhi, DONG Jia-yu, GUO Xu-liang
    2023, 20(06): 1695-1711.
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    Geohazards along highways are the main natural hazards that could affect the safety and operation of highway systems. Understanding the risks faced by highways in areas affected by geohazards is an urgent problem to be solved. This study used historical geohazard events from Sichuan Province and highway network data to propose a geohazard risk index that reflects the risk geohazards along highways. Furthermore, this work applied the entropy method and expert scoring to calculate the weight of the index. The spatial distributions of landslides, debris flows, collapses, and unstable slopes along the highways were analysed based on ArcGIS spatial statistics, and the highway geohazard intensity index were obtained. The relationships between slope, rainfall, vegetation coverage, rock type, land use, and incision depth with geohazards were analysed, and the highway geohazard susceptibility index was calculated by the weighted information method. Based on the intensity and susceptibility index, we obtained a geohazard risk index which can better evaluate the risk of highways, and made a highway geohazard risk map to aid the prevention and mitigation of geohazards along highways and assist with highway network planning.
  • Changes of spring wind erosion based on wind erosion climate factor in the black soil region of Northeast China
    YAN Ping, JI Sheng-tai, LI Xiu-fen, ZHU Hai-xia, WANG Liang-liang, ZHAI Mo, WANG Ping, ZHAO Hui-ying
    2023, 20(06): 1712-1724.
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    The dry and windy climate and low ground cover in spring in the black soil region of Northeast China make the soil strongly affected by wind erosion, which seriously threatens the food security and ecological security of this region. In this paper, based on the daily observation data of 124 meteorological stations in study area from 1961 to 2020, seasonal and monthly wind erosion climate factor( C) in spring(March to May) were calculated by using the method proposed by the Food and Agriculture Organization of the United Nations(FAO), the wind erosion characterization in spring were systematically analyzed based on C by various statistical analysis methods. The results showed that in the past 60 years, spring wind erosion climate factor(C_(Sp)) and monthly C of the whole region and each province(region) all showed highly significant decreasing trend, but they began to show rebounded trend in the middle or late 2000s. C_(Sp) of the study area showed a significant upward trend since 2008 with an increase of 4.59(10a)~(-1). The main contributors to this upward trend are the changes of C in March and in April. For the four provinces(regions), C_(Sp) in Heilongjiang, Jilin, Liaoning and eastern Inner Mongolia all showed rebounded since 2008, 2011, 2008 and 2009, respectively. The rebounded trend of C_(Sp) in eastern Inner Mongolia was the most obvious with a tendency rate of 11.27(10a)~(-1), and its mutation occurred after 1984. The rebound trend of C_(Sp) in Heilongjiang Province takes the second place, with a trend rate of 4.72(10a)~(-1), but there's no obvious time mutation characteristics. The spatial characteristics of CSpand monthly C are similar, showing decreasing characteristics centered on the typical black soil belt of Northeast China. Compared with 1961-1990, in the period from 1991 to 2020, the proportion of high value areas(C_(Sp)>35, monthly C>10) has decreased to varying degrees, while the proportion of low value areas( C_(Sp)≤10, monthly C ≤4) has increased. The trends of seasonal and monthly C in 82.2%～87.7% of the stations show significant decreases at 95% confidence level. C_(Sp) is closely related to wind speed at 2m height, temperature difference, minimum temperature and precipitation in the same period, of which the correlation between C_(Sp) and wind speed is the strongest, indicating that the main control factor for C_(Sp) in the study area is wind speed, but the impact of the change of temperature and precipitation on C_(Sp) cannot be ignored.
  • Movement and deformation characteristics of overlying rock mass in deep coal seam
    LI Yong, ZHENG Jing, WANG Feng-nian, HU Chao-wen, YANG Fan, MA Xin-gen, TAO Zhi-gang
    2023, 20(06): 1725-1741.
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    The 110 mining method is an innovative and useful coal mining technology. It mainly relies on two technologies to improve coal mining rate: Top cutting and pressure relief, Negative Poisson's ratio anchor cable(NPR anchor cable) support. This study develops a large-scale physical model test using the speckle monitoring system(DIC), the stress-strain monitoring system, and the infrared thermal imaging system to deeply investigate the roadway deformation and failure law of the 110 mining method, the displacement movement mechanism of the overlying rock mass, and the change law of rock pressure. Results showed that pillarless coal mining utilizing mine pressure and rock fragmentation and expansion characteristics, the use of cut top pressure relief and NPR anchor stress compensation technology in the kilometer level of deep underground coal mining still has a positive effect along the tunnel space. In addition, they can reduce surface subsidence, provide a scientific basis for ecological protection, and develop other kilometer-level deep soft rock high-ground stress underground projects.
  • Sustainable remediation of failed slope using helical soil nails
    Saurabh RAWAT, Ashok Kumar GUPTA, Pankaj SHARMA
    2023, 20(06): 1742-1758.
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    The performance of a helical soil nailed structure is dependent on the installation torque required and the consequent pullout resistance developed. The present research work aims at proposing theoretical models to estimate the required torque during installation of helical soil nails. Moreover, theoretical models are also developed to predict the pullout capacity of single and group of the helical nail for uniform and staggered arrangements. The proposed model predicts the pure-elastic and elastic-plastic pullout behavior of different helical nails. An equation for estimating the capacity-totorque Ratio(Kt) has also been developed for different nail shaft diameters. The results from the proposed models are validated with experimental results obtained from model testing of both single and group of helical nails. The predicted results are also compared for validation with the published literature. The results for installation torque and pullout load depict that the developed models predict values which are in accordance with the experimental results and are also found in good agreement with the published literature. Thus, the proposed models can effectively be used by the filed engineers for estimating the required installation torque and corresponding pullout capacities for single or double plate helical soil nails in cohesionless soil under surcharge pressure range of 0 – 50k Pa.
  • Experimental study on the movement law of overlying rock non-pillar coal overhead mining
    LI Yong, ZHENG Jing, WANG Feng-nian, MA Xin-gen, ZHANG Rui-xue, SUN Ying-ying, YIN Jian-bin, TAO Zhi-gang
    2023, 20(06): 1759-1773.
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    Pillarless coal mining technology is a new practical technology. Based on the compensating mechanical behavior of the Negative Poisson's Ratio(NPR) anchor cable on the roof, the roadway was successfully retained by the top cutting and pressure relief technology. This study utilizes the Digital Speckle Monitoring(DIC monitoring), stress-strain monitoring, and infrared thermal imaging systems to conduct physical model experiment of similar materials from the displacement, stress-strain, and temperature fields to investigate in depth the fracture change law of the overlying rock. In addition, it uses FLAC3D numerical simulation to invert the surface displacement settlement. The results show that the non-pillar overhead mining under the 110 mining method has little influence on the rock crack in the middle of the coal seam, and the crack development area is mainly concentrated in the overlying rock mass of the upward coal seam. The compensatory mechanical behavior of NPR anchor cable and the dilatation characteristics of rock mass have a good effect of retaining roadway along goaf, and can also reduce surface settlement. The 110 mining method provides a scientific basis for ecological environment protection and the development of other kilometer deep soft rock high ground stress underground projects.
  • Supporting structure failure caused by the squeezing tunnel creep and its reinforcement measure
    ZHAO Jin-peng, TAN Zhong-sheng, LI Lei, WANG Xiu-ying
    2023, 20(06): 1774-1789.
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    Tunnels deeply buried have high crustal stress and are prone to large deformation disasters when encountering soft rock. The large deformation phenomenon during the construction process of the Maoxian Tunnel on the Chengdu-Lanzhou Railway is particularly evident. This article focuses on the large deformation problem of the No.1 inclined shaft of the Maoxian Tunnel, and uses on-site monitoring methods to explore the reasons for tunnel structure failure, and analyzes the mechanical behavior of the tunnel structure. By using numerical simulation methods, the effectiveness of the second-layer support in resisting creep loads in tunnels was studied, and the influence of the construction time of the secondlayer support on the mechanical properties of the tunnel was discussed. The results indicate that the first-layer support in the tunnel is a structural failure caused by asymmetric deformation caused by creep, while the second-layer support has a good effect on resisting creep loads. The research results can provide a technical reference for deformation control of squeezing tunnels.
  • Effects of solar radiation and fine roots on suction of Amorpha fruticose-vegetated soil
    GUO Han-qing, CHEN Xiao-qing, SONG Dong-ri, MU Qing-yi, SADEGHI Hamed, JIANG Hao, LV Ming
    2023, 20(06): 1790-1804.
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    The thickness of shallow landslides is generally less than 2 m, which is of the same order of magnitude as the growth range of vegetation roots. Vegetation roots can improve the stability of shallow soil through mechanical and hydraulic effects. Therefore, the landslide process is closely related to the plant roots growing on the slope surface. Plant roots play a dominant role in the regulation of soil suction through solar radiation induced transpiration. However, little is known about the correlation between cumulative solar radiation and soil suction. Moreover, the specific effects of fine roots on the suction distribution are not clear in most previous studies. In this study, a vegetated soil of a drought-tolerant and water-tolerant shrub, namely Amorpha fruticose, was adopted. The suction and volumetric water content of bare and vegetated soils were monitored under natural conditions for 4 months. The results demonstrate that there is a nearly linear relationship between cumulative solar radiation and suction ranging from zero to 100 kPa. Regarding the modeling of the soil-plant-atmosphere interactions, this relationship could serve a significant role in calculating the root water uptake under given solar radiation conditions. In addition, higher suctions were observed at the lower layer of the vegetated soil than those at the middle layer, which is different from the results of vegetated soil from previous investigations. This is due to the fact that the root area index(RAI) of fine roots at the lower layer is twice that of the middle layer. Importantly, the higher concentration of fine roots at the lower layer of vegetated soil sample resembles the root distribution of shrub near the soil-bedrock interface on shallow bedrock landslides. The fine roots would increase soil suction through transpiration, and hence reduce the permeability and increase shear strength of landslides. Eventually, these new findings serve as a preliminary step on the evaluation of the stability of this common type of landslides.