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过刊目录

  • 2020年, 17卷, 第12期
    刊出日期：2024-06-19
      
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  • Tourist management in national parks in the Czech-German borderland:Bohemian 'Switzerland' and Saxon‘Switzerland'
    Krzysztof KO?ODZIEJCZYK
    2020, 17(12): 2853-2879.
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    In the article tourist management in two national parks in the Czech-German borderland are being compared,namely Bohemian 'Switzerland'(also known as Czech 'Switzerland') and Saxon'Switzerland'.Situated on either side of the state border,they feature the same type of geographical environment.Transport accessibility,transborder links and the hiking trail network are analyzed using methodology sourced from graph theory.The result of the analyses is a classification of tourist hubs and tourist centers,as well as an indication of the main directions of tourist flow.The German national park is decidedly more accessible but with a detrimental effect on the natural environment primarily due to its fragmentation by a dense network of tourist trails.In both parks trails enter the core zone(in theory a strict protection area) but this occurs on a larger scale on the German side.In the Czech national park a greater number of positive examples of managing tourist movements can be identified.Additionally,larger areas managed for dispersion,or from which tourists are generally excluded,are located there.
  • Exploring the potential of Sentinel-2A satellite data for aboveground biomass estimation in fragmented Himalayan subtropical pine forest
    Mobushir Riaz KHAN, Iftikhar Ahmad KHAN, Muhammad Hasan Ali BAIG, LIU Zheng-jia, Muhammad Irfan ASHRAF
    2020, 17(12): 2880-2896.
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    The Sentinel-2 A satellite having embedded advantage of red edge spectral bands offers multispectral imageries with improved spatial,spectral and temporal resolutions as compared to the other contemporary satellites providing medium resolution data.Our study was aimed at exploring the potential of Sentinel-2 A imagery to estimate Above Ground Biomass(AGB) of Subtropical Pine Forest in Pakistan administered Kashmir.We developed an AGB predictive model using field inventory and Sentinel 2 A based spectral and textural parameters along with topographic features derived from ALOS Digital Elevation Model(DEM).Field inventory data was collected from 108 randomly distributed plots(0.1 ha each) across the study area.The stepwise linear regression method was employed to investigate the potential relationship between field data and corresponding satellite data.Biomass and carbon mapping of the study area was carried out through established AGB estimation model with R(o.86),R2(0.74),adjusted R2(0.72) and RMSE value of 33 t/ha.Our results showed that first order textures(mean,standard deviation and variance) significantly contributed in AGB predictive modeling while only one spectral band ratio made contribution from spectral domain.Our study leads to the conclusion that Sentinel-2 A optical data is a potential source for AGB estimation in subtropical pine forest of the area of interest with added benefit of its free of cost availability,higher quality data and long-term continuity that can be utilized for biomass carbon distribution mapping in the resource constraint study area for sustainable forest management.
  • Deformation mechanism and collapse treatment of the rock surrounding a shallow tunnel based on on-site monitoring
    QIU Hong-zhi, CHEN Xiao-qing, WU Qi-hong, WANG Ren-chao, ZHAO Wan-yu, QIAN Ke-jiang
    2020, 17(12): 2897-2914.
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    When tunnels are constructed at shallow depths in areas with poor geological conditions,such as portal sections,valleys and hillsides in regions with granitic bedrock,considerable excavation-induced deformation of the surrounding rock may occur,potentially resulting in tunnel collapses.The main reason for these problems is the lack of understanding of the deformation mechanism and evolution of the soft granitic rock surrounding the tunnel and the adoption of inappropriate construction technology and methods.This article analyzes the deformation mechanism of the rock surrounding a shallow tunnel based on in situ monitoring data as a case study and suggests that certain measures should be taken to effectively control the deformation of the surrounding rock and to minimize the potential for tunnel collapse.The results show that the deformation of the granitic soil surrounding the tunnel can be divided into three stages:the rapid deformation stage,the slow deformation stage and the stabilization stage.Appropriate construction methods should be carefully selected to ensure safety during tunnel excavation in the first stage.To avoid secondary disasters caused by tunnel collapses,three treatment measures may be implemented as part of safety management:enhancing the monitoring of the surrounding rock deformation,adjusting the construction methods and optimizing the support systems.In particular,accurate monitoring data and timely information feedback play a vital role in tunnel construction.Therefore,engineers with considerable engineering experience and professional knowledge are needed to analyze the monitoring data and make accurate predictions of tunnel deformation to ensure that reasonable measures are taken in the process of shallow tunnel excavation.
  • Rapid identification of landslide,collapse and crack based on low-altitude remote sensing image of UAV
    LIAN Xu-gang, LI Zou-jun, YUAN Hong-yan, LIU Ji-bo, ZHANG Yan-jun, LIU Xiao-yu, WU Yan-ru
    2020, 17(12): 2915-2928.
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    Landslides,collapses and cracks are the main types of geological hazards,which threaten the safety of human life and property at all times.In emergency surveying and mapping,it is timeconsuming and laborious to use the method of field artificial investigation and recognition and using satellite image to identify ground hazards,there are some problems,such as time lag,low resolution,and difficult to select the map on demand.In this paper,a10 cm per pixel resolution photogrammetry of a geological hazard-prone area of Taohuagou,Shanxi Province,China is carried out by DJ 4 UAV.The digital orthophoto model(DOM),digital surface model(DSM) and three-dimensional point cloud model(3 DPCM) are generated in this region.The method of visual interpretation of cracks based on DOM(as main)-3 DPCM(as auxiliary) and landslide and collapse based on 3 DPCM(as main)-DOM and DSM(as auxiliary) are proposed.Based on the low altitude remote sensing image of UAV,the shape characteristics,geological characteristics and distribution of the identified hazards are analyzed.The results show that using UAV low altitude remote sensing image,the method of combination of main and auxiliary data can quickly and accurately identify landslide,collapse and crack,the accuracy of crack identification is 93%,and the accuracy of landslide and collapse identification is 100%.It mainly occurs in silty clay and mudstone geology and is greatly affected by slope foot excavation.This study can play a great role in the recognition of sudden hazards by low altitude remote sensing images of UAV.
  • GIS-based evaluation of landslide susceptibility using a novel hybrid computational intelligence model on different mapping units
    ZHANG Ting-yu, MAO Zhong-an, WANG Tao
    2020, 17(12): 2929-2941.
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    Landslide susceptibility mapping is significant for landslide prevention.Many approaches have been used for landslide susceptibility prediction,however,their performances are unstable.This study constructed a hybrid model,namely box counting dimension-based kernel logistic regression model,which uses fractal dimension calculated by box counting method as input data based on grid cells mapping unit and terrain mapping unit.The performance of this model was evaluated in the application in Zhidan County,Shaanxi Province,China.Firstly,a total of 221 landslides were identified and mapped,and 11 landslide predisposing factors were considered.Secondly,the landslide susceptibility maps(LSMs) of the study area were obtained by constructing the model on two different mapping units.Finally,the results were evaluated with five statistical indexes,sensitivity,specificity,positive predictive value(PPV),negative predictive value(NPV) and Accuracy.The statistical indexes of the model obtained on the terrain mapping unit were larger than those based on grid cells mapping unit.For training and validation datasets,the area under the receiver operating characteristic curve(AUC) of the model based on terrain mapping unit were 0.9374 and 0.9527,respectively,indicating that establishing this model on the terrain mapping unit was advantageous in the study area.The results show that the fractal dimension improves the prediction ability of the kernel logistic model.In addition,the terrain mapping unit is a more promising mapping unit in Loess areas.
  • Deformation and failure of a high-steep slope induced by multi-layer coal mining
    YU Jian-le, ZHAO Jian-jun, YAN Hao-yuan, LAI Qi-yi, HUANG Run-qiu, LIU Xiu-wei, LI Yang-chun
    2020, 17(12): 2942-2960.
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    During underground mining,accurate revelation on the deformation and failure mechanisms of a high-steep slope under multi-layer mining conditions facilitates the prevention and control of geological disasters in mines.Numerical simulation based on discrete element theory can be used to explore the characteristics and mechanism of action of deformation and failure of a slope under complex geological and multi-layer mining conditions.By utilising PFC2 D(particle flow code) software,the deformation and failure characteristics of a high-steep slope in Faer Coal Mine in Guizhou Province,China were investigated.Additionally,the mechanism of influence of different numbers of mining layers on the deformation and failure of the high and steep slope was elucidated.The result showed that after the goaf passed by the slope toe,multi-layer mining aggravated the subsidence and deformation of the slope toe:the slope toppled forward as it sank.The toppling of the slope changed the slope structures:the strata in the front of the slope were transformed from anti-dip to down-dip features.Extruded by collapsedtoppled rock mass,the slope toe and the rock mass located in the lower part of the slope toe generally exhibited a locking effect on the slope.Multi-layer mining degraded the overall stability of the slope,in that the total displacement of the slope was much greater than the total mining thickness of the coal seams.Based on the aforementioned research,ideas for preventing and controlling geological disasters during mining operations under a high-steep slope were proposed.
  • Comparative performance assessment of landslide susceptibility models with presence-only,presenceabsence,and pseudo-absence data
    ZHAO Dong-mei, JIAO Yuan-mei, WANG Jin-liang, DING Yin-ping, LIU Zhi-lin, LIU Cheng-jing, QIU Ying-mei, ZHANG Juan, XU Qiu-e, WU Chang-run
    2020, 17(12): 2961-2981.
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    The quality of the data for statistical methods plays an important role in landslide susceptibility mapping.How different data types influence the performance of landslide susceptibility maps is worth studying.The goal of this study was to explore the effects of different data types namely,presence-only(PO),presence-absence(PA),and pseudo-absence(PAs) data,on the predictive capability of landslide susceptibility mapping.This was completed by conducting a case study in the landslide-prone Honghe County in the Yunnan Province of China.A total of 428 landslide PO data points were selected.An equivalent number of nonlandslide locations were generated as PA data by random sampling,and 10,000 sites were uniformly selected at random from each region as PAs data.Three landslide susceptibility models,namely the information value model(IVM),logistic regression(LR) model,and maximum entropy(MaxEnt) model,corresponding to the three data types were investigated.Additionally,the area under the receiver operating characteristic curves(ROC-AUC),seven statistical indices(i.e.accuracy,sensibility,falsepositive rate,specificity,precision,Kappa,and Fmeasure),and a landslide density analysis were used to evaluate model performance regarding landslide susceptibility mapping.Our results indicated that the MaxEnt model using PAs data performed the best and had the highest fitness with the highest ROC-AUC values and statistical indices,followed by the IVM model with only landslide data(PO),and the LR model using PA data.Using PAs data avoided the inherent over-predictive shortcomings of PO data by limiting the predicted area of high-landslide susceptibility.Additionally,the random sampling design of landslide PA data increased the uncertainty of landslide susceptibility mapping and influenced the performance of the model.Therefore,our results suggested that the PAs data sampling provided a useful data type in the absence of high-quality data.Finally,we summarized the principles,advantages,and disadvantages of the three data types to assist with model optimization and the improvement of predicted performance and fitness.
  • Channelized and unchannelized collapses of granular columns on a horizontal surface
    ZHANG Quan, HUANG Bo-lin, ZHAO Hai-lin, CHEN Xiao-ting, LUO Chao-lin
    2020, 17(12): 2982-2996.
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    Columnar dangerous rock mass is widely developed in many high and steep mountain areas around the world.It often collapses,disintegrates and produces debris flow,which is disastrous.The collapse process of the columnar dangerous rock mass is very similar to the collapse of granular column.In this paper,we report the results of an experimental investigation of the flow induced by the collapse of a column of granular material over a horizontal surface.Two different setups are used,namely,a channelized granular column collapse(i.e.,two-dimensional) and an unchannelized granular column collapse(i.e.,three-dimensional),allowing us to compare channelized and unchannelized collapses flows.The experimental data suggest that our experimental findings were markedly different from those reported by previous authors(i.e.,include the channelized and unchannelized collapse flows showed differences in energy conversion and dissipation).In channelized collapse flows,the maximum vertical speed appears in the free fall regime,while,the maximum speed in the vertical direction of unchannelized collapse flows appears in the spreading regime.During the whole collapse process,i.e.,in channelized and unchannelized collapse flows,the conversion of potential energy and kinetic energy does not occur uniformly,and the maximum kinetic energy of the channelized collapse flows is higher than that of the unchannelized collapse flows,and compared with the unchannelized collapse flows,the dissipation energy in the channelized collapse flows is lower.A series of experiments was performed to predict the behaviour of different granular columns(characterized by different initial aspect ratio(a),varying from 1 to 4).The data obtained from 2 D experimental model and3 D experimental model have certain amount of difference,such as the particle runout distance(d_1),the maximum central height(h_2),and the deposition angle(i.e.,β_1,β_2).These differences show that the 2 D experimental model does not fully represent the 3 D conditions(i.e.,the role of side-walls on the channelized collapse flows characteristic is nonnegligible).Accordingly,care must be taken when validating 3 D models with 2 D experimental data.The movement of the tower dangerous rock masses with collapse failure mode could be evaluated using this channelized and unchannelized granular column experimental results.
  • Stability analysis of open-pit gold mine slopes and optimization of mining scheme in Inner Mongolia,China
    REN Shu-lin, TAO Zhi-gang, HE Man-chao, PANG Shi-hui, LI Meng-nan, XU Hao-tian
    2020, 17(12): 2997-3011.
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    The geological structure of the Changshanhao open-pit mine in Urad Middle Banner,Inner Mongolia,China is extremely complicated,and slope instability has frequently occurred in various forms,such as wedge sliding,bedding sliding,and toppling failure.In order to study the failure mechanisms of these slopes,the geological structure and mechanical rock properties were investigated based on field investigations and laboratory tests.Numerical models for the present mining area and final mining area of the original scheme were established to analyze slope stability.The results showed that the unique geomorphological characteristics of the mining area were generated by geological tectonism,and the north side of the stope is an anti-dip layered rock slope and the south side is a dip layered rock slope.Slope failure is the consequence of endogenic and exogenic integration,including physical and mechanical properties of the rock mass,geological structures such as faults and joints,and human-caused factors such as blasting and excavation disturbances.Then the original excavation scheme was redesigned mainly by optimizing the slope angle and decreasing the final mining depth to maintain slope stability.Finally,the Monte Carlo method was used to analyze the reliability of the slope angle optimization scheme.The open-pit mine excavation plan that meets the stability requirements was obtained eventually.
  • Obtaining morphometric variables from gullies using two methods of interpolation laser scanner data:the case study of Vassouras,Brazil
    OLIVEIRA Carlos Magno Moreira de, FRANCELINO Márcio Rocha, MENDON?A Bruno Araujo Furtado de, RAMOS Isabela Queiroz
    2020, 17(12): 3012-3023.
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    Gully erosion is a worldwide problem of land degradation and water quality,and it is also frequent in Brazil.Typically,anthropic influence is the major driver of gully evolution.To study and monitor gullies it is necessary to use specific instruments and methods to obtain accurate information.The objective of this study was to use Terrestrial Laser Scanning(TLS) to create digital elevation model(DEM) accurately and define morphometric variables that characterize gullies in a mountainous relief.Two different interpolations were evaluated using the Topogrid and GridSurfaceCreate algorithms to elaborate DEM.Topographic profile for gullies was used to assess modeling quality.The DEM of the Gully 1(G_1) from the Topogrid algorithm estimated soil loss of 49%,whereas the GridSurfaceCreate algorithm estimated a soil loss of97%,in a period of 1 year.The estimated soil loss for the Gully 2(G2) was 14% from the Topogrid,and 8%from the GridSurfaceCreate algorithm.The GridSurfaceCreate algorithm underestimated the volume to area ratio for G2 due to a failure on interpolating a region of low point representativity.The Topogrid algorithm represented better the terrain irregularities,as observed through the topographic profiles traced in three regions of G1 and G2.Statistical analysis showed that the GridSurfaceCreate algorithm presented lower accuracy in estimating elevations.The underestimation trend of this algorithm was also observed in G2.The gullies showed considerable soil losses,which may reduce the areas suitable for agricultural activities,and silting up of water courses.The Topogrid algorithm presented satisfactory results,denoting great potential to produce morphometric data of gullies.
  • Identifying ephemeral gullies from high-resolution images and DEMs using flow-directional detection
    DAI Wen, HU Guang-hui, YANG Xin, YANG Xian-wu, CHENG Yi-han, XIONG Li-yang, GIS, University of Salzburg, TANG Guo-an
    2020, 17(12): 3024-3038.
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    Ephemeral gullies,which are widely developed worldwide and threaten farmlands,have aroused a growing concern.Identifying and mapping gullies are generally considered prerequisites of gully erosion assessment.However,ephemeral gully mapping remains a challenge.In this study,we proposed a flow-directional detection for identifying ephemeral gullies from high-resolution images and digital elevation models(DEMs).Ephemeral gullies exhibit clear linear features in high-resolution images.An edge detection operator was initially used to identify linear features from high-resolution images.Then,according to gully erosion mechanism,the flow-directional detection was designed.Edge images obtained from edge detection and flow directions obtained from DEMs were used to implement the flow-directional detection that detects ephemeral gullies along the flow direction.Results from ten study areas in the Loess Plateau of China showed that ranges of precision,recall,and Fmeasure are 6 o.66%-90.47%,65.74%-94.98%,and63.10%-91.93%,respectively.The proposed method is flexible and can be used with various images and DEMs.However,analysis of the effect of DEM resolution and accuracy showed that DEM resolution only demonstrates a minor effect on the detection results.Conversely,DEM accuracy influences the detection result and is more important than the DEM resolution.The worse the vertical accuracy of DEM,the lower the performance of the flow-directional detection will be.This work is beneficial to research related to monitoring gully erosion and assessing soil loss.
  • Models and measurements of seven years of evapotranspiration on a high elevation site on the Central Tibetan Plateau
    WANG Li-hui, HE Xiao-bo, Jakob F.STEINER, ZHANG Dong-wei, WU Jin-kui, WANG Shao-yong, DING Yong-jian
    2020, 17(12): 3039-3053.
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    Evapotrantaspiration is a crucial part of the hydrological cycle but few ground observatories for the Tibetan Plateau exist.In this study,we present lysimeter measurements from the growing season during seven years at a remote field location on the Tibetan Plateau.The measurements show rates between 2.5 and 3 mm·d~(-1) during the warmer months from June to August,dropping to 2 to 2.5 mm·d~(-1) in September.This results in a total volume of evapotranspiration of approximately 300 mm·yr~(-1) for the months from June to September.The inter-daily variability is however large,and comparison to meteorological variables suggest that this is largely driven by radiation and humidity.Data for a single season from a nearby flux tower allows us to compare the two common measurement methods for evapotranspiration in the field,showing an overall good agreement between the approaches.We also tested commonly applied models used to estimate evapotranspiration rates,namely the FAO-PenmanMonteith(PM) and the Priestly-Taylor(PT) model,which both make use of radiation data as well as the simpler Hargreaves-Samani(HS) and Rohwer(R)models which only need air temperature and wind speed as input.The most data intensive model(PM)has the lowest root mean square error(RMSE)(1.36 mm·d~(-1)) and the mean bias error(MBE)(-0.05 mm·d~(-1)) and reproduces the daily variability generally well.The much simpler HS model performs slightly worse(1.38 and 0.35 mm·d~(-1)),but fails to reproduce the variability,due to its lack of information of local radiation and humidity data.Our results are in line with large scale estimates of evapotranspiration for the cold and arid region,provide a first long time series of in-situ measurements from a high elevation site and suggest that both the PM and HS models are appropriate when no direct measurements are available.
  • Stem taper equations for diameter and volume predictions of Abies cilicica Carr.in the Taurus Mountains,Turkey
    Onur ALKAN, Ramazan ?Z?EL?K
    2020, 17(12): 3054-3069.
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    Taper equations are an important tool in estimating stem volumes at a multi-product level for sustainable forest management.Nine taper equations are tested from three categories to estimate diameter at specified point on the stem,height at specified diameter,volumes of any desired portion of the stem,and whole tree volume of Taurus fir in Taurus Mountains of Turkey.To account for autocorrelation and multicollinearity present among multiple stem data observations collected from the same tree.proper statistical approaches were used in model fitting.Comparisons are made to determine which equation provides the best overall fit to all data based on four goodness-of-fit statistics,Coefficient of determination(R2);Root mean square error(RMSE),Akaike's Information Criterion(AIC),and Bayesian information criterion(BIC).Results indicated that all taper equations tested could be used to accurately estimate section diameter at given height and stem volume.Clark et al.'s taper equation provided better results than the others for Taurus fir when an additional stem diameter observation at 5.30 m was available.Segmented and variable-form taper models consistently provided better results than the simple taper models except for Max and Burkhart's model.Fang et al.'s and Kozak's taper models showed equally good performance to describe stem taper and to predict tree stem volume.Therefore,these taper equations are able to be used to estimate diameter and volume for Taurus fir trees,if an upper stem diameter measurement was not available.
  • Effects of climate variability and land use/land cover change on the Daihai wetland of central Inner Mongolia over the past decades
    CHUN Xi, QIN Fu-ying, ZHOU Hai-jun, DAN Dan, XIA Ying-ying, ULAMBADRAKH Khukhuudei
    2020, 17(12): 3070-3084.
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    The wetland ecosystem and its driving mechanism are significance impact on the ecological environment and the sustainable development of semi-arid regional economy.Agricultural and industrial land use/land cover change(LUCC) is also important for wetland system.The Daihai wetland(DW)in Inner Mongolia has been suffering from severe environmental problems such as water resource shortages and wetland areas decrease.We analyzed spatiotemporal LUCC at the catchment scale of Daihai Lake,which has recently exhibited a dramatic loss of water area,and investigated the potential role of climatic changes and human activities in the wetland loss.From 1976 to 2015,the arable land and construction land increased by 71.72 and 15.81 km2,with ranges of 18.72% and 39.61%,respectively.Meanwhile,the wetland area decreased by 84.47 km2,accounting for 29.07% of the area in1976.From 1960 to 2015,the area of Daihai Lake decreased by 100.73 km~2,diminishing to 37.09% of the area in 1960,and the lake storage accordingly shrank from 12.9×10~8 to approximately 3.9×10~8 m~3.The lake level also rapidly declined.From 1962 to2014,the lake water mineralization,total nitrogen(TN),and total phosphorus(TP) increased by 2410,7.86,and 0.182 mg L-1,respectively.The pollution sources included not only mineral fertilizers and pesticides,but also livestock,poultry breeding,aquaculture,and rural household waste.The lake area decreased with increasing agricultural development,Daihai power plant(DHPP) water consumption,and catchment climatic dryness.Thus,the urgent implementation of effective restoration and mitigation measures are needed.
  • Land use induced blurring of forest-grassland transition in north-west Himalaya-A case study using Moving Split Window boundary detection technique
    Shevita PANDITA, Harish Chander DUTT
    2020, 17(12): 3085-3096.
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    Transition zone or ecotone is a unique community sandwiched between two communities/ecosystems/biomes.These ecotones in Himalaya remained unexplored for many ecological aspects like biodiversity,phyto-sociology,boundary detection and even impact of change in land use pattern(anthropogenic activity).The most accepted and widespread technique called as Moving Split Window(MSW) technique is used for detection of vegetation and environmental boundaries at four different sites in the lesser stratum of north-west Himalaya.All the four sites were at different distances from the nearest human inhabited area.Anthropogenic activities like grazing,herb collection,wood collection etc.were common at proximal sites.Such activities have led to the change in land use pattern.In this study,we have tried to work out the impact of the change in land use pattern(human interference) on the vegetation and basic environmental parameters like soil pH,electrical conductivity and moisture on forestgrassland ecotone in north-west Himalaya.Data on mountain steepness was also collected and analyzed.The dissimilarity profile using the statistical tool Squared Euclidian Distance(SED) indicated that species turnover locations increase with the increase in distance of ecotones from human settlements.The ecotones at distant locations from human villages are characterized with blunt as well as sharp peaks for vegetation data,however,conditions are reverse in case of the proximal sites.The study also reveals that as the distance between the ecotone and human settlements increases,the complex conditions like multiple vegetation boundaries prevails on the transitions.In this regard,land use induced blurring of forest-grassland transition in north-west Himalaya is summed up in the study.
  • Tree species composition and diversity in montane forests of Garhwal Himalaya in relation to environmental and soil properties
    Dinesh Singh RAWAT, P.TIWARI, Sudipta Kumar DAS, J.K.TIWARI
    2020, 17(12): 3097-3111.
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    The montane forests of Garhwal Himalaya were investigated for tree species composition and diversity in relation to environmental and edaphic variables.A stratified random sampling approach was adopted to collect the field data from each forest.A total of 39 tree species belonging to 31 genera and 23 families were recorded from the sampling area(6 forest stands ×10 plots in each).Lauraceae with 5 species was the largest family while Quercus(4 species) emerged as the largest genus.Species-area curve(asymptote) predicted more species than the observed number of species.Cluster analysis has shown that the two Abies pindrow dominant forest stands had the highest similarity in tree species composition.The tree stem density ranged from 540-1170 ha-1,basal area 23.01-55.94 m~2 ha-1,ShannonWiener diversity index 1.69-2.49,evenness index0.42-0.74,beta diversity 0.40-0.82 and similarity index 0.17-0.54 in the six studied forests.Two-way indicator species analysis(TWINSPAN) identified four distinct tree communities in the study area with Daphniphyllum himalayense,Abies pindrow,Quercus oblongata,and Pinus roxburghii as indicator species of corresponding communities.Canonical correspondence analysis(CCA) ascertained the TWINSPAN results and revealed the relation of tree species with environmental and edaphic variables.The phytosociological attributes of tree species varied from one forest stand to another;however,the tree species richness,density,and diversity peaked at intermediate elevation on the north aspect.Findings reveal that tree composition and diversity in the montane forests of Garhwal Himalaya are influenced by both environmental(elevation and slope aspect)and soil variables(texture,water holding capacity,moisture content,available N,exchangeable P,and pH).This study will help in understanding the forest distribution across the western Himalaya,guiding the conservationists and policymakers in carrying out conservation-related management activities,designing the long-term monitoring studies and assessing the effects of ongoing and future climate change and disturbances.
  • Creep damage properties of sandstone under dry-wet cycles
    WANG Xin-gang, LIAN Bao-qin, WANG Jia-ding, FENG Wen-kai, GU Tian-Feng
    2020, 17(12): 3112-3122.
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    Rock creep properties can be used to predict the long-term stability in rock engineering.In reservoir bank slopes,sandstones which are frequently used in the bank slope undergoing longterm effects of dry-wet(DW) cycles due to periodic water inundation and drainage may gradually accumulate creep deformation,resulting in rock structure's damage or even geological hazards such as landslides.To fully investigate the effect of DW cycles on the creep damage properties of sandstone,triaxial creep tests were conducted on saturated sandstone with different DW cycles by using a triaxial rheometer apparatus.The experimental results show that both the instantaneous strain and the stabilized strain increase with the DW cycles.In addition,using the Burgers model,four kinds of functions including an exponentially decreasing function,a linearly decreasing function,a linearly increasing function and an exponentially increasing function were proposed to express the relationships between the shear modulus,viscoelastic parameters of the Burgers model and the deviatoric stress under different DW cycles.Through comparative analysis,it is found that the theoretical curves generated using proposed four kinds of functions are in good agreement with the experimental data.Furthermore,macromorphological and microstructural observations were performed on specimens after various triaxial rheological tests.For samples with small number of DW cycles,approximately X-shaped fracture surfaces were observed in shear failure zones,whereas several shear fractures including obvious axial and horizontal tensile cracks,and flaws were found for samples with relatively large DW cycles due to long-term propagation and evolution of micro-fissures and micro-pores.Furthermore,as the DW cycles increases,the variation in micro-structure of samples after creep failure was summarized into three stages,namely,a stage with good and dense structure,a stage with pore and fissure propagation,and a stage with extensive increase of pores,fissures and loose particles.It is concluded that the combination effect of permeation of water molecules through pores and fissures within sandstone,and the propagation of preexisting pores and fissures owing to the dissolution of mineral particles leads to further deterioration of the mechanical properties of sandstone as the number of DW cycles increases.This study provides a fundamental basis for evaluating the long-term stability of reservoir bank slopes under cyclic fluctuations of water level.
  • Dynamic response characteristics of dry and watersaturated schist under impact loading
    ZHOU Yang, SU Sheng-rui, CHEN Jian-xun
    2020, 17(12): 3123-3136.
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    Many geological engineering hazards are closely related to the dynamic mechanical properties of rock materials.However,most existing studies on the dynamic mechanical properties of rock materials were conducted on the hard rocks such as sandstone,granite,limestone,and marble,whereas soft rocks,such as schist,are less studied.Therefore,in this study,a series of triaxial impact tests were conducted on dry and saturated schist by employing a modified triaxial split Hopkinson pressure bar system to reveal the coupling effects of water,strain rate,and triaxial confining pressure on the mechanical properties of schist.The results show that schist is a type of watersensitive rock and the stress-strain curve of saturated schist has apparent ductility.The effects of strain rate on dynamic strain,deformation modulus and peak stress were analyzed.The results also show that the dynamic peak stress is affected by the combined softening effect and viscous effect of water under impact loading.Finally,it was found that the failure mode of schist belongs to typical axial tensile failure under uniaxial impact tests,and shear failure is the main failure mode under triaxial impact tests.With the increase in confining pressure,the failure modes of schist change from tensile failure to shear failure.This research can provide useful parameters for geological engineering hazard prevention in mountain areas.
  • Recent tectonic activity in Central Alborz Mountain,Iran:morphometric analysis and knickpoint identification
    Parisa SHOKRI, Maryam DEHBOZORGI, Saeid HAKIMI ASIABAR
    2020, 17(12): 3137-3161.
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    Alborz,as part of the Alpine-Himalayan orogeny belt,has been the result of the convergence of the Central Iranian and Eurasian plate since the late Triassic.The study area located in Central Alborz encompasses different Quaternary faults.Thus,the present study aimed to evaluate the effect of faults on river landforms through morphotectonic indices and the causes of knickpoints and knickzones in the Bedrock Rivers in part of Central Alborz.To this end,six morphometric indices such as longitudinal gradient(SL),hierarchical anomaly(Δα),the bifurcation index(R),hypsometric integral and hypsometric curve(Hi-Hc),relative relief(Bh),and basin shape(Bs) were calculated and analyzed in38 sub-basins of the area.Finally,the area was divided into extremely high,high,medium,and low tectonic activity areas using the relative tectonic activity(IAT).Normalized steepness and concavity indices along with the longitudinal profiles of the streams were obtained using Matlab and Arc GIS software.Based on the findings,the existence of slope-break knickpoints at the mountain piedmont at the outlet of large rivers through active faults demonstrated that most of these landforms were created by movements along the main faults such as Khazar,Nusha,Soheil,Deylaman,Kashachal,representing high tectonic activity in the central and southern parts of the study area.However,the values of these indices were extremely low and indicated low tectonic activity in the northern parts located in the embayment part of the Caspian Sea.Finally,the findings revealed that these classes correspond well to the areas with landforms such as V-shaped and narrow valleys,gorges,deflected and offset streams,deformed Neogene,and Quaternary units that indicate the post-Neogene activity.