EN中文

过刊目录

  • 2023年, 20卷, 第05期
    刊出日期：2024-06-19
      
  • 全选
    |
  • Flood risk on arid alluvial fans: a case study in the Joghatay Mountains,Northeast Iran
    Kaveh GHAHRAMAN, Balázs NAGY
    2023, 20(05): 1183-1200.
      可视化   收藏
    Among the common hazards related to alluvial fans, flooding is one of the most important.Nonetheless, in populated alluvial fans, not only the natural processes are effective in floods, but the artificial structures and modifications can change the behavior of flooding and its potential risks. This study aims to indicate the flood-prone landforms in a set of populated alluvial fans in an arid region and investigate the role of anthropogenic activities in controlling/exacerbating flooding in alluvial fans. To achieve this goal, 15 Ground Range Detected in High resolution(GRDH) SAR Sentinel-1 images, covering a total of 24 alluvial fans, were acquired. Pre-processing and post-processing steps were applied to all images to identify flood-prone sections of the studied alluvial fans. The results showed that feeder channels,spreading sites, and wide interfluves are the most flood-prone landforms of alluvial fans. In terms of anthropogenic modifications to mitigate flooding, a rampart system is distributed in the study area.Ramparts are levee like structures formed from the fan material. They aim to mitigate flood hazard on residential areas, infrastructures, and agricultural lands of the study area. Results show that the rampart system can reduce the danger of floods, but it cannot be considered a long-term solution. Therefore, a comprehensive flood protection system distributed throughout the whole alluvial fan system is needed.Results also reveal that in regions where flood monitoring is challenging, SAR images can be used as a freely available data set to monitor and identify flooding hotspots.
  • Fast clogging problem of open check dams and a new type suggestion:curved footed type open check dam
    AN?LAN Tu??e, AK?AL? Emre
    2023, 20(05): 1201-1219.
      可视化   收藏
    Driftwood is one of the important physical components in mountainous rivers which causes severe hazards due to the clogging of bridges, culverts,and narrow sections during floods. Therefore, the understanding of driftwood dynamics and mitigation measures are crucial for managing wood in rivers.Open check dams are the most commonly used engineering measure for preventing driftwood from reaching downstream areas. Nevertheless, these open check dams frequently lose their sediment transport function when they are blocked by sediment and driftwood, especially during major flood events. This paper proposes a new type of open check dam for preventing from clogging. Thus, flume experiments were conducted to examine the influence of different types of open check dams on the characteristics of driftwood deposition. For the model with wood length(LWD)=16.5 cm, wood diameter(D) =15 mm, and wood number(N)=172, the highest trapping efficiency was observed with 90.1% and 87.2% retention rates for the classical debris flow breaker and curved footed open check dams, respectively. Laboratory tests showed that through this proposed design, woody debris blockage in a very short time was prevented from the accumulation of woods beside the dam. In addition to this, most of the sediment passed through the check dam and most of the driftwood got trapped.It can be briefly stated that the geometrical design of the structure plays an important role and can be chosen carefully to optimize trapping efficiency. By designing this type of open check dams in mountain river basins, it may provide a better understanding of the driftwood accumulation and basis for the optimal design of these structures. Further development of the solution proposed in this work can pave the way for designing different types of open check dams for effective flood management.
  • Landslide displacement prediction based on the ICEEMDAN, ApEn and the CNN-LSTM models
    LI Li-min, WANG Chao-yang, WEN Zong-zhou, GAO Jian, XIA Meng-fan
    2023, 20(05): 1220-1231.
      可视化   收藏
    Landslide deformation is affected by its geological conditions and many environmental factors.So it has the characteristics of dynamic, nonlinear and unstable, which makes the prediction of landslide displacement difficult. In view of the above problems,this paper proposes a dynamic prediction model of landslide displacement based on the improvement of complete ensemble empirical mode decomposition with adaptive noise(ICEEMDAN), approximate entropy(ApEn) and convolution long short-term memory(CNN-LSTM) neural network. Firstly,ICEEMDAN and Ap En are used to decompose the cumulative displacements into trend, periodic and random displacements. Then, the least square quintic polynomial function is used to fit the displacement of trend term, and the CNN-LSTM is used to predict the displacement of periodic term and random term.Finally, the displacement prediction results of trend term, periodic term and random term are superimposed to obtain the cumulative displacement prediction value. The proposed model has been verified in Bazimen landslide in the Three Gorges Reservoir area of China. The experimental results show that the model proposed in this paper can more effectively predict the displacement changes of landslides. As compared with long short-term memory(LSTM) neural network, gated recurrent unit(GRU) network model and back propagation(BP)neural network, CNN-LSTM neural network had higher prediction accuracy in predicting the periodic displacement, with the mean absolute percentage error(MAPE) reduced by 3.621%, 6.893% and 15.886% respectively, and the root mean square error(RMSE) reduced by 3.834 mm, 3.945 mm and 7.422mm respectively. Conclusively, this model not only has high prediction accuracy but also is more stable,which can provide a new insight for practical landslide prevention and control engineering.
  • Landslide susceptibility mapping of mountain roads based on machine learning combined model
    DOU Hong-qiang, HUANG Si-yi, JIAN Wen-bin, WANG Hao
    2023, 20(05): 1232-1248.
      可视化   收藏
    Landslide susceptibility mapping of mountain roads is frequently confronted by insufficient historical landslide sample data,multicollinearity of existing evaluation index factors,and inconsistency of evaluation factors due to regional environmental variations. Then, a single machine learning model can easily become overfitting,thus reducing the accuracy and robustness of the evaluation model. This paper proposes a combined machine-learning model to address the issues. The landslide susceptibility in mountain roads were mapped by using factor analysis to normalize and reduce the dimensionality of the initial condition factor and generating six new combination factors as evaluation indexes. The mountain roads in the Youxi County, Fujian Province, China were used for the landslide susceptibility mapping. Three most frequently used machine learning techniques, support vector machine(SVM), random forest(RF), and artificial neural network(ANN) models, were used to model the landslide susceptibility of the study area and validate the accuracy of this evaluation index system. The global minimum variance portfolio was utilized to construct a machine learning combined model. 5-fold cross-validation, statistical indexes, and AUC(Area Under Curve) values were implemented to evaluate the predictive accuracy of the landslide susceptibility model. The mean AUC values for the SVM, RF, and ANN models in the training stage were 89.2%, 88.5%, and 87.9%, respectively, and 78.0%,73.7%, and 76.7%, respectively, in the validating stage.In the training and validation stages, the mean AUC values of the combined model were 92.4% and 87.1%,respectively. The combined model provides greater prediction accuracy and model robustness than one single model.
  • Prediction of the instability probability for rainfall induced landslides: the effect of morphological differences in geomorphology within mapping units
    WANG Kai, ZHANG Shao-jie, XIE Wan-li, GUAN Hui
    2023, 20(05): 1249-1265.
      可视化   收藏
    Slope units is an effective mapping unit for rainfall landslides prediction at regional scale. At present, slope units extracted by hydrology and morphological method report very different morphological feature and boundaries. In order to investigate the effect of morphological difference on the prediction performance, this paper presents a general landslide probability analysis model for slope units. Monte Carlo method was used to describe the spatial uncertainties of soil mechanical parameters within slope units, and random search technique was performed to obtain the minimum safety factor;transient hydrological processes simulation was used to provide key hydrological parameters required by the model, thereby achieving landslide prediction driven by quantitative precipitation estimation and forecasting data. The prediction performance of conventional slope units(CSUs) and homogeneous slope units(HSUs) were analyzed in three case studies from Fengjie County, China. The results indicate that the mean missing alarm rate of CSUs and HSUs are 31.4% and 10.6%, respectively. Receiver Operating Characteristics(ROC) analysis also reveals that HSUs is capable of improving the overall prediction performance, and may be used further for rainfall-induced landslide prediction at regional scale.
  • Ecological and hydrologic evolution history in the sensitive zone of both East Asian summer monsoon and Westerly since the Last Glacial Maximum
    LI Yu, PENG Si-min
    2023, 20(05): 1266-1281.
      可视化   收藏
    The Qilian Mountains, located in the northeastern Qinghai-Tibet Plateau, is a sensitive zone of both East Asian summer monsoon(EASM)and westerly winds(WW). The evolution history and driving mechanism of the ecosystem and hydrologic cycle in this region on long-term timescales have not yet been clarified. In this study, we comprehensively study the hydrologic and ecological evolution history in the sensitive zone since the Last Glacial Maximum(LGM) by integrating surface sediments, paleoclimate records, TraCE-21ka transient simulations, and PMIP3-CMIP5 multi-model simulation. Results show that hydrologic and ecological proxies from surface sediments are significantly different from west to east and mainly divided into three sections: the monsoonaffected region in the eastern Qilian Mountains, the intersection region in the central Qilian Mountains,and the westerly-affected region in the western Qilian Mountains. Meanwhile, paleo-ecological and paleohydrologic reconstructions from the surroundings uncover a synchronous climate evolution that the EASM mainly controls the eastern Qilian Mountains and penetrates the central Qilian Mountains in monsoon intensity maximum, while the WW dominates the central and western Qilian Mountains on both glacial-interglacial and millennial timescales.The simulation results further bear out the glacial humid climate in the central and western Qilian Mountains caused by the enhanced WW, and the humidity maximum in the eastern Qilian Mountains controlled by the strong mid-Holocene monsoon. In general, east-west differences in climate pattern and response for the EASM and the WW are integrally stable on both short-term and long-term timescales.
  • Soil chronosequence derived from landslides on the upper reach of Minjiang River, western China
    HE Jun-bo, WU Yan-hong, BING Hai-jian, ZHU He, ZHOU Jun
    2023, 20(05): 1282-1292.
      可视化   收藏
    Soil chronosequences derived from landslides with certain time series are the great avenue to elevate our understanding on the processes of pedogenesis, nutrient dynamics, and ecosystem evolution. However, the construction of reliable soil chronosequence from historical landslides remains intricate. Here, we presented a 22,000-year soil chronosequence from multiple landslides on the upper reach of Minjiang River, western China. The variation in a variety of pedogenesis indices and soil nutrients verified the reliability of the chronosequence. The silica-alumina ratio and silica sesquioxide ratio decreased significantly with soil age.This reflected the enrichment of Al/Fe/Ti oxides but the depletion of Si oxides with the soil development.Meanwhile, the values of the Chemical Index of Weathering and the Chemical Index of Alteration increased significantly with soil age, especially from 5 to 89 years. These variations were attributed to the soil weathering, which led to the destruction of soil minerals with the rapid loss of most of cations(e.g., K,Na, Ca, and Mg) during the soil development. The concentrations of carbon and nitrogen in topsoil increased with soil age, and the carbon accumulation rate slowed significantly from 5,500 to 22,000 years.The total phosphorus concentrations decreased with soil age, suggesting the gradual loss of soil phosphorus with soil development. The results indicate that the landslide chronosequence established on the upper reach of Minjiang River is reliable and delineates a long-term soil development process, which will provide a great platform for further improvement of biogeochemical theories and understanding sustainable vegetation restoration.
  • Pollution and health risk assessment of heavy metals in waters around mine sites of Elazig(Eastern Turkey)
    H.Alim BARAN, Mahmut Tahir NALBANTCILAR, Nida KOKTAN
    2023, 20(05): 1293-1306.
      可视化   收藏
    Turkey's Eastern Anatolia Region is the oldest known mineral mining area of Maden and Alacakaya. Chromite production in the Alacakaya field constitutes 50% of the country's exports, and copper mines in the Maden region account for approximately 12% of the country's copper production. There is a risk of water pollution due to significant mine waste which affects the Inci and Maden rivers. The water needs of many settlements are met from these streams, which run through these two mine sites. This study investigated the water pollution in the rivers. 25 water samples were collected during the dry and rainy periods, and the Al,Cr, Cu, Fe, Li, Mn, Ni, Pb, Sr and Zn contents of these samples were examined in terms of health. Evaluation of element concentrations and creation of spatial distribution maps were performed using ArcGIS software. Spatial distribution maps, correlation and cluster analysis indicate that the source of heavy metals observed in waters is mine fields. The heavy metal content of the samples is higher in the dry period, the high concentration values are obtained from the mine sites, the decrease in the concentrations throughout the flow during the rainy period, are indicators of the effect of the mines on the water pollution. As a result of the comparison from the analysis results of water samples with World Health Organization(WHO),Environmental Protection Agency(EPA) and European Commission(EC) standards, the element values of Al, Cr, Fe, Mn,Ni and Pb exceeded the permissible values for health.The concentrations of these elements for dry period samples are: 0-6.411 mg L~(-1), 0.006-0.235 mg L~(-1), 0-13.433 mg L~(-1), 0-0.316 mg L~(-1), 0-0.495 mg L~(-1), 0-0.065mg L~(-1), and for rainy period samples are 0-1.698mg/L, 0-0.2 mg L~(-1), 0-9.033 mg L~(-1), 0-0.173 mg L~(-1), 0-0.373 mg L~(-1), 0-0.034 mg L~(-1), respectively. Although the waters in the region are polluted by heavy metals,it has been determined that there is no noncarcinogenic hazard as a result of the calculation of the hazard index(HI<1) by ingestion and dermal contact within the scope of human health risk assessment. This study will be beneficial as it draws attention to the prevention of the negative effects of water pollution, which may cause serious health problems in the future as a result of mining activities in the region.
  • Are the altitudinal patterns of plant diversity derived from field surveys consistent with those from empirical integrated methods?
    ZHAN Qing-hua, FU Zhi-hao, ZHOU Ya-dong, YAN Xue, WANG Qing-feng
    2023, 20(05): 1307-1315.
      可视化   收藏
    Field surveys and empirical integrated methods are commonly used in the ecological research to understand the altitudinal pattern of plant diversity of mountains. However, few studies have compared the differences between the two methods on the same scale. Here, we addressed and compared the altitudinal patterns of species richness(SR),phylogenetic diversity(PD), the standardized effect size of phylogenetic diversity(PDses) and mean phylogenetic distance(MPDses) of about 580 angiosperms growing on Mount Kenya from two independent datasets: one is based on our several times field surveys in this mountain and another one is based on empirical data integrated from literatures.We found that the altitudinal diversity patterns of field surveys dataset were consistent with the empirical integrated dataset. Both SR and PD showed hump-shaped patterns along the altitude, and both PDses and MPDses showed monotonically decreasing patterns along the altitude. The ratio of diversity between field surveys dataset and empirical integrated dataset were gradually increase along the altitude. Our research provides new insight for understanding the altitudinal diversity patterns of plants of a tropical mountain.
  • Dramatic changes in anatomical traits of a C_4 grass Chrysopogon serrulatus Trin.(Poaceae) over a 1000 m elevational gradient
    FATIMA Sana, HAMEED Mansoor, AHMAD Farooq, AHMAD Muhammad Sajid Aqeel, ANWAR Majid, MUNIR Mahwish, ASHRAF Muhammad, SHAH Syed Mohsan Raza, BASHARAT Sana, AHMAD Iftikhar, KHALIL Sangam
    2023, 20(05): 1316-1335.
      可视化   收藏
    Chrysopogon serrulatus(false beard-grass)is a dominant component of vegetation in the foothills of the Himalayas. To study whole plant morphology,individuals of C. serrulatus were collected from three plots at each of six locations spanning from 400 to 1,400 m. The population colonizing the highest elevation modifications in different plant organs. Roots showed increased metaxylem number and area. In the stem, especially outside of the vascular tissue, there was intensive sclerification indicative of increased xeromorphy as a survival strategy. At the highest elevation, leaves were wider; aerenchyma formation and increased sclerification were noted in the leaf sheath; and a greater proportion of storage parenchyma was observed in the leaf blade, all indicators of succulence.In contrast, leaves at lower elevations had xeric morphological features such as increased epidermal thickness, sclerification and more developed metaxylem area. In conclusion, shifting of morphological features in below-and above-ground plant parts of C. serrulatus were linked to shifts in environmental factors along this elevation gradient,thus enabling the successful distribution of this species along this elevation gradient.
  • Soil erosion differences in paired grassland and forestland catchments on the Chinese Loess Plateau
    YANG Si-qi, LUO Da, HAN Hao, JIN Zhao
    2023, 20(05): 1336-1348.
      可视化   收藏
    In this study, two adjacent gauged catchments on the Chinese Loess Plateau were selected, in which one catchment was afforested and one was restored with natural vegetation in 1954. The distributions of soil erosion rates were estimated between 2010 and 2020 with a high spatial resolution of 2 m in the paired catchments based on the Revised Universal Soil Loss Equation model(RUSLE) and Geographic Information Systems(GIS). The results showed that the simulated soil erosion rates in 2010-2020 averaged 12.58 and 8.56 t ha~(-1) a~(-1) for the grassland and forestland catchment, respectively.Moreover, areas with high soil erosion rates(> 80t ha~(-1) a~(-1)) were mainly distributed in the topography with steep slope gradients(>45°). Comparisons between simulated soil erosion rates and observed annual sediment loads indicated that the simulation results of the grassland catchment were lower than the observed values, while it was reversed in the forestland catchment. We conclude that the RUSLE model cannot simulate the gravity erosion induced by extreme rainfall events. For the forestland catchment,insufficient streamflow and dense vegetation coverage are crucial factors resulting in hindering the movement of sediments.
  • Precipitation scale effect of the TRMM satellite in Tianshan,China
    NING Shan, ZHOU Hong-wu, ZHANG Zheng-yong, BAI Shi-biao, LIU Lin
    2023, 20(05): 1349-1368.
      可视化   收藏
    High-resolution precipitation data is conducive to objectively describe the spatial-temporal variability of regional precipitation, and the study of downscaling techniques and spatial scale effects can provide technical and theoretical support to improve the spatial resolution and accuracy of satellite precipitation data. In this study, we used a machine learning algorithm combined with a regression algorithm RF-PLS(Random Forest-Partial Least Squares) to construct a downscaling model to obtain three types of high-resolution TRMM(Tropical Rainfall Measuring Mission) downscaled precipitation data for the years 2000-2017 at 250 m, 500 m, and 1km. The scale effects with topographic and geomorphological features in the study area were analysed. Finally, we described the spatial and temporal variation of precipitation based on the optimal TRMM downscaled precipitation data. The results showed that: 1) The linear relationships between the TRMM downscaled precipitation data obtained by each of the three downscaled models(PLS, RF, and RF-PLS) and the precipitation at the observation stations were improved compared to the linear relationships between the original TRMM data and the precipitation at the observation stations. The accuracy of the RF-PLS model was better than the other two models. 2) Based on the RF-PLS model, the resolution of the TRMM data was increased to three different scales(250 m, 500 m, and 1 km),considering the scale effects with topographic and geomorphological features.The precipitation simulation effect with a spatial resolution of 500 m was better than the other two scales. 3) The annual precipitation was the highest in the areas with extremely high mountains, followed by the mediumhigh mountain, high mountain, medium mountain,medium-low mountain, plain, low mountain, and basin.
  • Failure mechanism of a large-scale composite deposits caused by the water level increases
    ZHANG Xin, TU Guo-xiang, LUO Qi-feng, TANG Hao, ZHANG Yu-lin, LI An-run
    2023, 20(05): 1369-1384.
      可视化   收藏
    The failure of slope caused by variations in water levels on both banks of reservoirs is common.Reservoir landslides greatly threaten the safety of reservoir area. Taking large-scale composite deposits located on the Lancang River in Southwest China as a study case, the origin of the deposits was analyzed based on the field investigation and a multi-material model was established in the physical model test.Combined with numerical simulation, the failure mechanism of the composite deposits during reservoir water level variations was studied. The results indicate that the deformation of the large-scale composite deposits is a staged sliding mode during the impoundment process. The first slip deformation is greatly affected by the buoyancy weight-reducing effect, and the permeability of soil and variation in the water level are the factors controlling slope deformation initiation. The high water sensitivity and low permeability of fine grained soil play an important role in the re-deformation of deposits slope. During the impoundment process, the deformation trend of the deposit slope is decreasing,and vertical consolidation of soil and increasing hydrostatic pressure on the slope surface are the main reasons for deformation attenuation. It is considered that the probability of large-scale sliding of the deposits during the impoundment period is low. But the damage caused by local bank collapse of the deposit slope still needs attention. The results of this paper will further improve our understanding of the failure mechanism of composite deposits caused by water level increases and provide guidance for the construction of hydropower stations.
  • Proposing a novel geo-structural model for Torbat-e-Jam-Fariman plain(Northeast of Iran), based on Geomorphic indices calculation, conjugating the field evidences
    Mohsen JAMI, Alireza DOCHESHMEH GORGIJ
    2023, 20(05): 1385-1401.
      可视化   收藏
    There are various faults in northern and southern margins of Torbat-e-Jam-Fariman plain which show the probability of enormous earthquake in the future. In present study the geomorphic indices contain Asymmetry Function(Af), Sinuosity of mountain front(Smf), Valley floor index(Vf), Hypsometric index(Hi), Mean Axial slope of channel index(MASC) and Drainage Basin Shape(Bs), have been utilized to determine the relative tectonic activity index(IAT) to recognize, eventually, the geo-structural model of the study area. Faults and folds control the geo-structural activities of the study area, and the geomorphic indices are being affected in consequence of their activities. The intensity of these activities is different throughout the plain. There are many geomorphic evidences, related to active transform fault which are detectable all over the study area such as deviated rivers,quaternary sediments transformation, fault traces.Therefore, recognition of geo-structural model of the study area is extremely vital. Field study, then,approved the results of geomorphic indices calculation in determining the geo-structural model of the study area. Results depicted that the geostructural model of the study area is a kind of Horsetail splay form which is in accordance to the relative tectonic activity of the study area. Based on the above mentioned results it can be predicted that the splays are the trail of Neyshabour fault.
  • Field experiments on quantifying the contributions of Coreopsis canopies and roots to controlling runoff and erosion on steep loess slopes
    GONG Yu-wei, YU Hai-jun, TIAN Pei, GUO Wen-zhao, CHEN Lin, SHEN Ding-tao
    2023, 20(05): 1402-1423.
      可视化   收藏
    Grass recovery is often implemented in the loess area of China to control erosion. However, the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear.Taking the typical forage species(Coreopsis) in semiarid areas as subject, this study quantified the effects of canopies and roots on controlling slope runoff and erosion. A series of field experiments were conducted in a loess hilly region of China. Field plots(5 m length, 2 m width, 25° slope gradient)constructed with three ground covers(bare soil;Coreopsis with intact grass; only roots of Coreopsis),were applied with simultaneous simulated rainfall(60mm h~(-1)) and upslope inflow(10, 30, 50, 70, 90L min~(-1)). The results showed that compared with bare soil, intact grass significantly reduced runoff and soil loss rates by 16.6% and 62.4% on average, and decreased soil erodibility parameter by 66.3%. As inflow rate increased, the reductions in runoff and soil loss rates increased from 2.93 to 14.00 L min~(-1) and 35.11 to 121.96 g m~(-2) min~(-1), respectively. Canopies relatively contributed 66.7% to lowering flow velocity,turbulence, weakening erosive force and increasing hydraulic resistance. Roots played a predominant role in reducing soil loss and enhancing soil antierodibility, with relative contributions of 78.8% and 73.8%. Furthermore, the maximum erosion depth reduced by Coreopsis was at the upper slope section which was previously eroded the most. These results demonstrated the efficiency of Coreopsis cover in controlling runoff and erosion on steep loess slopes,especially under large inflow rates and at upper slope sections. We suggest protecting Coreopsis with intact grass at upper slope sections, while the aboveground grass biomass can be used for grazing or harvesting at middle and lower slope sections, with roots reserved.
  • Dynamic response characteristics of a circular lined tunnel under anisotropy frost heave of overlying soil at the tunnel portal section in cold regions
    ZHANG Shuo-cheng, CHEN Wen-hua
    2023, 20(05): 1424-1440.
      可视化   收藏
    The rapid development of traffic engineering in cold regions and its consequent problems need to be considered. In this paper, the dynamic response characteristics of the tunnel portal section in cold regions with harmonic load acting on the lining were studied in the frequency domain. The lining is in close contact with the frozen soil, and there is relative movement between the frozen and unfrozen soil due to the phase change. The analytical solution of the vibration of tunnel portal section caused by the harmonic load acting on the lining was derived under the consideration of the anisotropy frost heave of overlying soil. Based on the continuity conditions and boundary conditions,the undetermined coefficients were obtained, and the analytical solutions for different medium displacements and stresses of the cold-region tunnel system were acquired. The vertical pressure coefficient was equivalently simplified as a variable that could be used to replace the thickness of the overlying soil above the tunnel. The analysis of the parameter model shows that the change of the medium parameters(lining, frozen, and unfrozen soil)affects the circumferential stresses, the radial displacements and their peak frequencies of the soil.For example, the increase of density ratio of tunnel lining to frozen soil decreases the radial stresses of the frozen and unfrozen soil; the increase of volumetric frost heaving strain of the frozen soil increases the radial displacements of the frozen surface and decreases the stability of the frozen surface; the increasing of thickness of the frozen soil significantly reduces the radial displacement of unfrozen soil at dimensionless radius η = 4.5 compared with that of frozen soil at η = 1.5.
  • Centrifuge and numerical modeling of h-type anti-slide pile reinforced soil-rock mixture slope
    ZHANG Hao, XING Hao-feng, XUE Dao-rui, TANNANT Dwayne
    2023, 20(05): 1441-1457.
      可视化   收藏
    Due to the loose structure, high porosity and high permeability of soil-rock mixture slope, the slope is unstable and may cause huge economic losses and casualties. The h-type anti-slide pile is regarded as an effective means to prevent the instability of soilrock mixture slope. In this paper, a centrifuge model test was conducted to investigate the stress distribution of the h-type anti-slide pile and the evolution process of soil arching during the loading. A numerical simulation model was built based on the similar relationship between the centrifuge model and the prototype to investigate the influence factors of the pile spacing, anchored depth, and crossbeam stiffness, and some recommendations were proposed for its application. The results show that the bending moment distribution of the rear pile exhibits Wshaped, while for the front pile, its distribution resembles V-shaped. The soil arching evolution process during loading is gradually dissipated from bottom to top and from far to near. During the loading, the change of bending moment can be divided into three stages, namely, the stabilization stage, the slow growth stage, and the rapid growth stage. In engineering projects, the recommended values of the pile spacing, anchored depth, and crossbeam stiffness are 4.0d, 2.0d, and 2.0EI, where d and EI are the diameter and bending stiffness of the h-type anti-slide pile respectively.
  • Design of the yielding support used highly deformable elements for a tunnel excavated in squeezing rock
    TIAN Hong-ming, TIAN Yun, CHEN Wei-zhong, TAN Xian-jun, SHU Xiao-yun, LIU Xia-lin
    2023, 20(05): 1458-1468.
      可视化   收藏
    Yielding support is often used in the squeezing tunnel to prevent damage to the lining induced by large deformation of the surrounding rock.Highly Deformable Elements(HDE) which is often installed along the circumferential direction of the shotcrete lining is a common type of yielding support.To determine the yield parameters of HDE, the support characteristic of the lining using HDE and the ground pressure considering strain-softening of soft rock were analyzed by an analytical method. The analytical solution showed that when considering the strain-softening of squeezing ground, the ground pressure has a non-zero minimum value. The minimum value of ground stress can be used to determine the constant yield stress of the HDE, and the corresponding deformation of the minimum ground pressure can be used to determine the deformation capacity of the HDE. Based on the variation in the design constant yield stress and yield displacement of HDE with the in-situ stress and the mechanical parameters of the soft rock, equations were proposed for determining of the yield parameters of the HDE.
  • Stress response characteristics of BFRP anchors on loess mudstone slope under rainfall conditions
    WEI Hong, WU Hong-gang, WU Dao-yong, TANG Lin, PAI Li-fang, GUAN Wei
    2023, 20(05): 1469-1482.
      可视化   收藏
    To investigate the stress response characteristics and shear stress transfer mechanism of BFRP(basalt fiber reinforced plastics) anchors under rainfall conditions and to explore the reinforcement effect of BFRP anchors, a comparative indoor physical model test was conducted in this study using loess mudstone slope as a typical case, and multi-attribute response data, such as slope displacement, BFRP anchor strain and axial force, were obtained. Based on the variation law of slope displacement, it can be concluded that the deformation displacement of the slope on the side reinforced by BFRP anchors is smaller than that of slopes reinforced with steel anchors; the bearing capacity of BFRP anchor is given priority in time, and the anchoring effect of BFRP anchor at the top of the slope is given priority, and the axial force value of anchor is characterized by a surface amplification effect in space; the axial force is higher around the anchor head and tends to decay as a negative exponential function as the anchor extends in the direction of the interior of the slope; the shear stress of BFRP anchor and anchorage body are unevenly distributed along the axial direction, with the maximum value occurring in the free section near the slope surface and decreases as the BFRP anchor extends towards the interior of the slope. These results can provide a theoretical basis for the optimal design of BFRP anchors.
  • Characteristics and driving factors of abandoned cultivated land in the hilly regions of southern China: A case study in Longnan, Jiangxi Province
    CHEN Ze-bin, CHEN Yong-lin, LI Chao-jun, LIN Jian-ping, CHEN Pei-ru, SUN Wei-wei, WAN Zhi-wei
    2023, 20(05): 1483-1498.
      可视化   收藏
    The abandonment of cultivated land in southern China was gradually obvious. This research aims to provide a reference for solving the abandonment of cultivated land in hilly regions and promote rural development in China. We examined Longnan county located in the hilly regions of southern China as an example, where abandoned cultivated land is very common. We analyzed its land use data with a field survey to identify the abandoned cultivated land and geospatial characteristics. From the two aspects of social and natural factors, we analyzed the factors driving cultivated land abandonment with the help of Geodetector. The results showed that in 2019, the total area of the abandoned cultivated land in Longnan county was 4,962.35 hm~2, covering 39.51% of this region. Among the topographic factors, the abandonment rate is positively correlated with elevation and slope gradient,but not with slope direction. Among the land parcel conditions, the abandonment rate is positively correlated with the access to road network and cultivation distance from settlement. At the county level, the abandonment of cultivated land in study area was affected by multiple factors, among which,the direct factor was the reduction in the labor force,such as the decrease of farming laborers and the increase of female population, which made farming unsustainable. Changes in production factors also promoted transformations in farmers' motivation to engage in production, such as the decrease of grain crops and the increase of cash crops, which was the indirect factor affecting cultivated land abandonment.The development of the rural nonagricultural industry affected farmers' enthusiasm, such as the decrease of farming households, which was the fundamental factor leading to cultivated land abandonment in this area.