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过刊目录

  • 2021年, 18卷, 第07期
    刊出日期：2024-06-19
      
  • 全选
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  • Climate change indirectly enhances sandstorm prevention services by altering ecosystem patterns on the Qinghai-Tibet Plateau
    MENG Nan, YANG Yan-zheng, ZHENG Hua, LI Ruo-nan
    2021, 18(07): 1711-1724.
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    Climate change influences both ecosystems and ecosystem services. The impacts of climate change on ecosystems and ecosystem services have been separately documented. However, it is less well known how ecosystem changes driven by climate change will influence ecosystem services, especially in climate-sensitive regions. Here, we analyzed future climate trends between 2040 and 2100 under four Shared Socioeconomic Pathway(SSP) scenarios(SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) from the Coupled Model Intercomparison Project 6(CMIP6). We quantified their impacts on ecosystems patterns and on the ecosystem service of sandstorm prevention on the Qinghai-Tibet Plateau(QTP), one of the most climate-sensitive regions in the world, using Random Forest model(RF) and Revised Wind Erosion Equation(RWEQ). Strong warming(0.04°C/yr) and wetting(0.65 mm/yr) trends were projected from 2015 to 2100. Under these trends, there will be increased interspersion in the pattern of grassland and sparse vegetation with meadow and swamp vegetation, although their overall area will remain similar, while the areas of shrub and needleleaved forest classes will increase and move toward higher altitudes. Driven by the changes in ecosystem patterns caused by climate change indirectly, grassland will play an irreplaceable role in providing sandstorm prevention services, and sandstorm prevention services will increase gradually from 2040 to 2100(1.059-1.070 billion tons) on the QTP. However, some areas show a risk of deterioration in the future and these should be the focus of ecological rehabilitation. Our research helps to understand the cascading relationship among climate change, ecosystem patterns and ecosystem services, which provides important spatio-temporal information for future ecosystem service management.
  • Assessment of ecological importance of the Qinghai-Tibet Plateau based on ecosystem service flows
    LIN Zi-yan, XIAO Yi, OUYANG Zhi-yun
    2021, 18(07): 1725-1736.
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    Assessments of ecological importance based on static indexes that do not consider service flows frequently underestimate the importance of the Qinghai-Tibet Plateau as a "source". On the basis of natural environmental characteristics, this study selected six type of ecosystem services for evaluation, including water retention, soil retention, carbon sequestration, biodiversity conservation, sandstorm prevention, and tourism. According to the attributes of each ecosystem service flow, we calculated the flow length and traffic accessibility indexes, using Arc GIS hydrological module and kernel functions separately, to comprehensively analyse the ecological importance levels of the Qinghai-Tibet Plateau. Results showed that after considering the service flows, the ecologically important zone shifted to the core area of the Three River Source Region, such as Zadoi County located in the Tanggula Mountains. The area of extreme importance is mainly distributed in the Yarlung Zangbo River basin, Tanggula Mountains, Hengduan Mountains, and Qilian Mountains, which accounts for 31.7% of the Qinghai-Tibet Plateau, providing approximately 60% of the ecosystem services and having extremely high protection efficiency and protection value. By introducing ecosystem service flow indexes, this study confirmed the ecological importance of core source areas such as the Tanggula Mountains, weakened the space bias caused by not considering the spatial transfer of ecosystem services, and provided technical support for optimizing ecological protection strategies and coordinating regional development.
  • Lake water storage change estimation and its linkage with terrestrial water storage change in the northeastern Tibetan Plateau
    LI Ya-wei, WANG Yu-zhe, XU Min, KANG Shi-chang
    2021, 18(07): 1737-1747.
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    Tibetan Plateau(TP) lakes are important water resources, which are experiencing quick expansion in recent decades. Previous researches mainly focus on analyzing the relationship between terrestrial water storage(TWS) change and lake water storage(LWS) change in the total inner TP, it is still lack of researches about the spatial difference and the characteristic of sub-region in the inner TP. In this study, we estimated the area change of 34 lakes by using Landsat images in the northeastern TP during 1976–2013, and LWS change by using the Shuttle Radar Topography Mission(SRTM). The results suggested that LWS had shrunk from 1976 to 1994, and then expanded quickly until 2013. LWS had a serious decrease by 13.6 Gt during 1976–1994, and then it increased quickly by 35.4 Gt during 1994–2013. We estimated TWS change, soil moisture change, and permafrost degradation based on the satellite data and related models during 2003–2013. The results indicated that their changing rates were 1.86 Gt/y, 0.22 Gt/y, and –0.19 Gt/y, respectively. We also calculated the change of groundwater based on the mass balance with a decreasing trend of –0.054 Gt/y. The results suggested that the cause of TWS change was the increase of LWS. We analyzed the cause of lake change according to water balance, and found that the primary cause of lake expansion was the increasing precipitation(80.7%), followed by glacier meltwater(10.3%) and permafrost degradation(9%). The spatial difference between LWS change and TWS change should be studied further, which is important to understand the driving mechanism of water resources change.
  • Carbon storage of the forest and its spatial pattern in Tibet, China
    JIA Long-yu, WANG Gen-xu, LUO Ji, RAN Fei, LI Wei, ZHOU Jun, YANG Dan-li, SHI Wen-bo, XU Qian, ZHU Kun, YANG Yang
    2021, 18(07): 1748-1761.
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    The raising concentration of atmospheric CO_2 resulted in global warming. The forest ecosystem in Tibet played an irreplaceable role in maintaining global carbon balance and mitigating climate change for its abundant original forest resources with powerful action of carbon sink. In the present study, the samples of soil and vegetation were collected at a total of 137 sites from 2001 to 2018 in Tibet. Based on the field survey of Tibet's forest resources and 8~(th) forest inventory data, we estimated the carbon storage and carbon density of forest vegetation(tree layer, shrub, grass, litter and dead wood) and soil(0-50 cm) in Tibet. Geostatistical methods combined with Kriging spatial interpolation and Moran's I were applied to reveal their spatial distribution patterns and variation characteristics. The carbon density of forest vegetation and soil in Tibet were 74.57 t ha~(-1) and 96.24 t ha~(-1), respectively. The carbon storage of forest vegetation and soil in Tibet were 344.35 Tg C and 440.53 Tg C, respectively. Carbon density of fir(Abies forest) was 144.80 t ha~(-1) with the highest value among all the forest types. Carbon storage of spruce(Picea forest) was the highest with 99.09 Tg C compared with other forest types. The carbon density of fir forest and spruce forest both increased with the rising temperature and precipitation. Temperature was the main influential factor. The spatial distribution of carbon density of forest vegetation, soil, and ecosystem in Tibet generally showed declining trends from western Tibet to eastern Tibet. Our results facilitated the understanding of the carbon sequestration role of forest ecosystem in the Tibet. It also implied that as the carbon storage potential of Tibet's forests are expected to increase, these forests are likely to serve as huge carbon sinks in the current era of global warming and climate change.
  • Vegetation cover of the lahar valley on the Sarychev Peak volcano(Matua Isl., Middle Kuril Islands) after the Eruption in 2009: current state and features of succession processes
    Fedor A.ROMANYUK, Alexander V.KORDYUKOV
    2021, 18(07): 1762-1777.
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    The paper presents the study of the vegetation recovery after the descent of the lahar during the eruption of the Sarychev Peak volcano(Matua Isl., Middle Kuriles) in 2009. The works were carried out in 2017. It was found that during the secondary succession, plant communities, typical of the altitudinal zonation of the volcanic structure vegetation, are formed on lahar sediments in the following manner: the upper sections of the slope are occupied by sparse meadow and shrub vegetation, the middle are presented by shrub belt with a developed canopy, and the lower are representative of shrub large-grass belt. At the same time, the ordination analysis of the vegetation cover of the lahar valley by the detrended correspondence analysis(DCA) revealed the dispersion of the counting areas along the altitudinal gradient. This is opposite to that characteristic for both, the background communities on the slopes of the studied volcanic structure, and for communities in dynamical equilibrium of a typical altitude profile. Besides, directly correlating indicators of α-diversity of communities indicate the presence of open young communities at the stage of a complex grouping. Since the species Duschekia fruticosa which is an identifier in buried sites, forms communities in a state of dynamic equilibrium, with individuals of 40–50 years old, and at the time of the work, formed a canopy with individuals of 7–8 years old, a complete recovery of the communities of the lahar valley is possible in no less than 40 years. The acquired data on the recovery of vegetation on lahar contribute to the study of succession processes in the sites located in the zone of active volcanism. In addition, in this work, for the first time, the rates of restoration of the vegetation cover following its destruction as a result of burial by lahar products, are estimated. The specific features of this process are also considered. Employing the broad range of mathematical methods for quantitative analysis of indicators of young communities inhabiting the substrate makes it possible to identify patterns of vegetation formed during succession processes. The specifics of this organization are taken into account in this analysis.
  • Does forest restoration influence soil infiltrability? A case study in the restored woodland of Sierra de ávila(Central Spain)
    MONGIL-MANSO Jorge, NAVARRO-HEVIA Joaquín, SAN MARTíN Roberto
    2021, 18(07): 1778-1793.
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    Infiltration, as a major component of the hydrological cycle, plays an important role in ecosystems, river flooding, and soil erosion. Therefore, this process has been studied on different soils, with different vegetation cover, and under different climate conditions. However, it is still necessary to know how infiltration rates depend on land degradation, vegetation cover, forest management, and forest restoration, since soil infiltration is related to soil hydrological function and hydrological ecosystem services. The aim of our study is to analyze the way reforestation and check dam construction have helped to improve soil infiltration rates in comparison with old, degraded land, different soils and vegetation covers in Central Spain. Therefore, three infiltration tests were carried out by means of a simple methacrylate infiltrometer ring, in four sampling plots, for five types of land use:(i) native holm oak forest,(ii) 60-year-old reforested pine wood,(iii) shrubs,(iv) sediment wedges of check dams, and(v) gullies and degraded hillslopes. Our results show much higher infiltration rates in the soil of 60-yearold pine reforestation sites(1198.00 mm·h~(-1)), and in the sediment wedges of check dams(1088.00 mm·h~(-1)), than in those of degraded hillslopes(365.00 mm·h~(-1)) and shrubland(420.80 mm·h~(-1)). The rates were also shown to be close to those from the remaining patches of native holm oak woodland(770.40 mm·h~(-1)). We also found that organic matter, humus and litter depth, and height of vegetation and cover, all improve soil infiltration rates, while slope degree, presence of coarse elements, stoniness, clay content, bulk density, and electric conductivity inhibit the rates. It was additionally seen that pine reforestation and check dam construction caused degraded land to recover its hydrological conditions to a level that is quite close to that of the ancient oak holm native forest, alongside ameliorating the hydrological cycle in the watershed. This information will be very useful for decisionmaking processes related to land restoration projects, forest management, and environmental policy.
  • Estimation of mountain block recharge on the northern Tianshan Mountains using numerical modeling
    PING Jian-hua, ZHU Ya-qiang, MEI Xue-mei, LENG Wei, LI Sheng, ZHAO Ji-chang
    2021, 18(07): 1794-1810.
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    Mountain block recharge(MBR), an important water resource, is a widespread process that recharges lowland aquifers. However, little is known about MBR due to the limited climatic and geologic data in mountainous regions such as the northern central foothills of Tianshan. Here, we present an approach to quantify MBR through the combination of water balance calculations and numerical modeling. MBR calculated from the water balance in the data-limited Tianshan Mountains is employed as a fluid-flux boundary condition in the numerical model of the plain. To verify the performance of the model, mean absolute error and root mean square error were used. Results show that the volume of water that is recharging the aquifer via MBR is 107.29 million m~3/yr, accounting for 2.2% of the total precipitation that falls in the mountains. Additionally, 53.3% of that precipitation enters the plain aquifer via runoff, totaling 2,652.68 million m~3/yr. The lower volume of MBR is attributed to a major range-bounding anticline with apparent low permeability in the Tianshan Mountains. Through numerical modeling of groundwater, MBR coming from bedrock was found to be significant, accounting for 14% of total aquifer recharge in the plain, only after the portion of runoff seepage. This research contributes to a deeper understanding of MBR, and may provide instructions for estimating groundwater recharge in arid and semi-arid areas.
  • Variations in rare earth elements with environmental factors in lake surface sediments from 17 lakes in western China
    DU Ding-ding, CHEN Liu-qin, BAI Yong-hui, HU Hai-ping
    2021, 18(07): 1811-1822.
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    Numerous lakes in western China are excellent sites for understanding environmental change. However, what dominates rare earth element(REE) variations are still under debate in the lake environmental research. In this study, we selected 28 surface sediment samples from 17 lakes(i.e. largescale lakes, small water bodies, etc.) in the QinghaiTibet Plateau and Xinjiang area. These samples were analyzed to reveal the behavior of the REEs and major elements. These REE patterns are characterized by light rare earth element(LREE) enrichment, weak Ce anomaly(0.84-0.98, 0.94 on average) and negative Eu anomaly(0.53-1.00, 0.67 on average). The homogeneous REE patterns may reflect similar REE of the source lithologys. However, the REE abundances showed some significant differences. In this study, water chemistry data analyses inferred that the highly REE values appear possibly in the saltwater lake, and also related to carbonate mineral, whereas p H played a minor role in REE concentrations. In large-scale lakes(e.g. Lake Bosten and Lake Ulungur), the results showed that the relatively larger REE values are in the margins of lakes. Moreover, lower REE contents are towards the central region. Comprehensive study suggested that five major factors control the REE contents:(1) The REE tends to increase with the increase of the weathering intensity.(2) Likewise, heavy mineral(i.e. rutile, anatase, zircon, etc.) are probably primary in these sediments because they are highly enriched in the REE.(3) The contribution of Fe-Mn oxides is significant in sediments because their concentrations highly correlate with the REE.(4) The carbonate mineral(mainly calcite) played a significant role on the REE values in the lakes because the REEs are incorporated into the carbonate minerals generating the low REE concentrations.(5) Major element analysis, mineral analysis, and grain-size data analysis showed that the REE distribution is chiefly influenced by finer grain-size component of lake sediments due to the decreasing proportion of quartz and feldspar than coarser one. Moreover, the clay minerals in finer grain-size sediments can highly absorb the REE.
  • Impact of anthropogenic activities on vegetation dynamics in a reservoir area: model establishment and a case study of Longkaikou Reservoir in China
    YANG Wei, PEI Jun, CAI Yan-peng, YI Yu-jun
    2021, 18(07): 1823-1836.
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    Vegetation in hot and arid valleys is a crucial indicator of ecosystem health, but is vulnerable to human activities and environmental change. Using the Longkaikou Reservoir in the Jinsha River in southwestern China as a case study, we developed a spatially explicit model that combined the plant growth, fruiting, seed dispersal, and seed germination stages to reveal the potential impact of multiple human activities(reservoir construction, logging, grazing, and aerial seeding) on the vegetation dynamics of Dodonaea viscosa and Pinus yunnanensis. After reservoir construction, the grassland area of 68 km~2 in 2003 decreased to 24 km~2 in 2018, replaced by forest, shrubland, and bodies of water, and the precipitation increased during the dry season, which indicated the improvement of the local plant and soil environment. Our model predicted that when soil moisture decreased by more than 20% compared to current levels, the area of D. viscosa increased greatly at low elevations; however, when at higher soil moisture, P. yunnanensis would occupy more of the study area. Logging and grazing would slightly change the spatial pattern of vegetation and delay P. yunnanensis communities from achieving stability by directly reducing plant biomass. Countermeasures such as aerial seeding would increase the total area by 13.13 km~2 and 8.09 km~2 of two plants, respectively, and accelerate the stabilization of plant communities. The effects of multiple human activities on vegetation may counteract each other; for example, logging decreased the P. yunnanensis area whereas aerial seeding increased it, and plant biomass changed in response to this pressure. Given the complex relationships between vegetation and human impacts, our study provides a scientific basis for vegetation restoration and ecological security in this hot and arid valley.
  • Leaf thickness and elevation explain naturalized alien species richness in a tropical mountain forest: A case study from Mount Gede-Pangrango National Park, Indonesia
    Decky Indrawan JUNAEDI, Imawan Wahyu HIDAYAT, Muhammad EFENDI, Zaenal MUTAQIEN, Musyarofah ZUHRI, Taufikurrahman NASUTION, Fitri KURNIAW ATI, Muhammad Imam SURYA, Lily ISMAINI, Aisyah HANDAYANI, Andes Hamuraby ROZAK
    2021, 18(07): 1837-1846.
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    Exotic plant invasion is one of the major causes of species extinction. In many contexts, mountainous forests are the last refuge for native species. There are several inventory studies conducted in mountainous and tropical forests in Indonesia. However, there are no studies yet on the factors that explain the abundance and richness of surveyed naturalized alien species. This study investigated whether the number of individuals and abundanceweighted species richness(AWR) of naturalized alien plant species in the hiking-trail of Mount GedePangrango National Park(MGPNP) forest area correlated with leaf traits(specific leaf area(SLA) and leaf thickness) and environmental factors(elevation, slope, and normalized difference vegetation index(NDVI)). We showed that leaf thickness and habitat elevation explained the AWR variations of naturalized alien species. We did not detect any important effect of leaf traits and environmental factors on the number of individuals per exotic species per plot. The influence of leaf thickness and habitat elevation indicates the important role of both biotic and abiotic factors on exotic species to develop a high species richness and become an invasive species in the tropical mountain forest ecosystem.
  • Assessing the invasion risk of botanical garden's exotic threatened collections to adjacent mountain forests: A case study of Cibodas Botanical Garden
    JUNAEDI Decky Indrawan, PUTRI Dwinda Mariska, KURNIAWAN Vandra
    2021, 18(07): 1847-1855.
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    A primary objective of botanical gardens is to conserve threatened plant species from different regions and countries. However, such ex-situ conservation practices for exotic plant species may pose a significant plant invasion risks. In this study, we predict the naturalization probability of exotic threatened plant species of Cibodas Botanical Garden(CBG) collections based on leaf trait(specific leaf area, SLA) or as a function of invasion risk assessment scoring system(Tropical Weed Risk Assessment Protocol, TWRAP). We found that SLA and TWRAP were positively correlated with naturalization probability. The TWRAP model produced higher predictive probabilities with larger uncertainty compared to SLA model. Parmentiera cereifera and Burretiodendron hsienmu are two species that have highest naturalization probability based on SLA model. Chamaedorea oblongata has the highest naturalization probability based on TWRAP model. From practical and management point of view, we recommend the simultaneous use of SLA-based and TWRAP-based invasive species risk assessment to estimate the naturalization risk of exotic threatened collections of botanical gardens to adjacent mountain forests. Finally, given the important conservation value of threatened exotic collection of botanical garden, we need to be aware with the invasion risks of these species. The threatened condition of a plant species is not only caused by its natural characteristics but also may be caused(in fact mostly confounding with) by external disturbance either natural catastrophic or human related activities. Thus, a threatened species may not necessarily a noninvasive species outside their natural distribution ranges.
  • Plant studies in Himachal Pradesh, Western Himalaya: a systematic review
    Himanshu BARGALI, Manisha MATHELA, Rupali SHARMA, Monika SHARMA, Dani YAMING, Amit KUMAR
    2021, 18(07): 1856-1873.
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    Owing to a predicted rise in temperature, increase in precipitation and the escalating anthropogenic stresses, the Himalayan ecosystems are the most threatened non-polar regions of the world. In the past, there have been racing extinctions and range shifts of several life forms in this region, particularly of the plant species. Therefore, consistent qualitative and quantitative records on botanical baseline data on a regular basis are indispensable. The current communication attempts to provide a detailed account on the current state of knowledge and research gaps in floristic studies of Himachal Pradesh, Western Himalaya. Based on an extensive review of more than 140 studies in the form of scientific peer reviewed literature on floristics, medicinal and aromatic plants(MAPs), rare, endangered, threatened and endemic species and ethno-botany, it is revealed that the number of floristic studies in Himachal Pradesh have surged in the past years but studies pertaining to the lower plants remain meagre. Unfortunately, the remote valleys including micro-watersheds lying in the coldarid regions are relatively less studied in terms of available growing stock and population status of MAPs. Depleting traditional ethno-botanical knowledge has been the major concern and, many threatened MAPs need to be accessed globally following IUCN standards. Thus, documentation of the conservation status of key MAPs, setting aside conservation areas around viable populations of threatened species, developing germplasm banks of the priority MAPs and monitoring the impacts of climate change has been suggested.
  • Impact failure models and application condition of trees in debris-flow hazard mitigation
    JIN Ke, CHEN Jian-gang, CHEN Xiao-qing, ZHAO Wan-yu, SI Guang-wu, GONG Xing-long
    2021, 18(07): 1874-1885.
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    Forestry has played an important role in hazard mitigation associated with debris flows. Most forest mitigation measures refer to the experience of soil and water conservation, which disregard the destructive effect of debris flows, causing potentially serious consequences. Determination of the effect of a forest on reducing debris-flow velocity and even stopping debris flows requires distinguishing between when the debris flow will destroy the forest and when the trees will withstand the debris-flow impact force. In this paper, we summarized two impact failure models of a single tree: stem breakage and overturning. The influences of different tree sizes characteristics(stem base diameter, tree weight, and root failure radius) and debris-flow characteristics(density, velocity, flow depth, and boulder diameter) on tree failure were analyzed. The observations obtained from the model adopted in this study show that trees are more prone to stem breakage than overturning. With an increase in tree size, the ability to resist stem breakage and overturning increases. Debris-flow density influences the critical failure conditions of trees substantially less than the debrisflow velocity, depth, and boulder diameter. The application conditions of forests in debris-flow hazard mitigation were proposed based on the analysis of the model results. The proposed models were applied in the Xiajijiehaizi Gully as a case study, and the results explain the destruction of trees in the forest dispersing zone. This work provides references for implementing forest measures for debris-flow hazard mitigation.
  • Potential sediment sources identification of debris flows in the Jiangjia Gully, China
    TIAN Xia-fei, LI Yong, TIAN Quan-yan
    2021, 18(07): 1886-1901.
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    It is of great significance for gully prevention and management to identify the potential sediment source of debris flow. Debris flow in a gully always originates from tributaries that have different gravity potential energies and sediment condition. In this study, tributaries of the Jiangjia Gully(JJG) in Yunnan province, China, are taken as the study area to determine the possible sediment sources of debris flow. It was found that tributaries with a high evolution index(EI, the integral of the hypsometric curve) always had high gravity potential energy, which favors the occurrence of landslide activity. Furthermore, the relationship between sediment distribution, gravity potential energy, and EI is compared, respectively. The results showed that the EI had a greater influence on the occurrence of landslides, and sediments were concentrated in tributaries with EI between 0.5 and 0.6. Accordingly, tributaries with EI > 0.5 were identified as the sediment sources of debris flow. In addition, the shape of a tributary was related to EI and can reflect the condition of water and sediment storage.
  • Changing mountain farmscapes: vulnerability and migration drivers in the Paute River watershed, Southern Ecuador
    Mario E.DONOSO, Fausto O.SARMIENTO
    2021, 18(07): 1902-1919.
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    Abrupt changes in land use/land cover have often characterized Andean rural landscapes. This is particularly notorious in the Paute River watershed in southern Ecuador. We seek to show how, under tenets of the global economy, rural mountain landscapes suffer constant modifications due to the agricultural practices of dwellers and migrants. Erosion of arable slopes takes center stage in analyzing vulnerability due to the high erodibility factor found in this watershed. By using remote sensing and GIS applications, we analyzed the potential erodibility with intersections of rural development constraining of ecosystem services, including the production of water, food, and cultural values in the Paute River watershed. We found six sources of migratory flows and analyzed topographic and elevation effects in potential erodibility indexes of agroecological options to ameliorate the environmental stress. We identified factors associated with migration trends observed in the area and assessed vulnerability issues of resource management that could prevent deforestation, soil erosion, and acculturation amidst the pressures of development in the region. We conclude that sustainable development options can be implemented with a watershed management approach oriented to diminish emigration. This approach shall be integrative, inclusive, and respectful of the rich biocultural diversity heritage conservation of southern Ecuador.
  • Deformation of the Zhangjiazhuang high-speed railway tunnel: an analysis of causal mechanisms using geomorphological surveys and D-InSAR monitoring
    MENG Xing-min, QI Tian-jun, ZHAO Yan, DIJKSTRA Tom, SHI Wei, LUO Yin-fei, WU Yuan-zhao, SU Xiao-jun, ZHAO Fu-meng, MA Jin-hui, ZHANG Yi, CHEN Guan, YUE Dong-xia, ZHANG Mao-sheng
    2021, 18(07): 1920-1936.
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    On 18 January 2016, the Zhangjiazhuang high-speed railway tunnel in Ledu, Qinghai Province, China, underwent serious deformation and structural damage. A crack formed at the top of the tunnel and the concrete on the crown peeled off. As a result, the tunnel could not be operated for three months. In order to determine the types and spatial distribution of the landslides in the region and the surface deformation characteristics associated with the tunnel deformation, we used field geological and geomorphological surveys, unmanned aerial vehicle image interpretation and differential interferometric synthetic aperture radar(D-In SAR) surface deformation monitoring. Nine ancient and old landslides were identified and analysed in the study area. Surface deformation monitoring and investigation of buildings in several villages on the slope front showed that the tunnel deformation was not related to deep-seated gravitational slope deformation. However, surface deformation monitoring revealed an active NEE–SWW fault in the area intersecting the tunnel at the location of the tunnel rupture. This constitutes a plausible mechanism for the deformation of the tunnel. Our study highlights the need for detailed engineering geomorphological investigations to better predict the occurrence of tunnel deformation events in the future.
  • Numerical simulation on the stability of rock slope based on an improved SPH Method
    YU Shu-yang, REN Xu-hua, ZHANG Ji-xun, WANG Hai-jun, SUN Zhao-hua, ZHOU Yu
    2021, 18(07): 1937-1950.
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    The presence of random fissures has a great impact on rock slope stability. To investigate the failure modes and stability of rock slopes containing different types of pre-existing fissures, the fracture mark ξ was introduced to improve the kernel function in the traditional smoothed particle dynamics(SPH) method, and a novel numerical method, the improved kernel of smoothed particle hydrodynamics(IKSPH), was proposed to realise the microscopic damage characteristics of particles. The ‘random fissure generating method' has been proposed for random fissure generation, and the gravity increase method has been embedded into the IKSPH program, thereby realising the stability analysis of rock slopes considering crack propagation processes. A typical steep rock slope is taken as a numerical simulation example considering the random distributions of preexisting fissures, and its failure modes as well as the stability under different conditions were simulated. The results show that the failure processes of the rock slope contain propagations of microcracks and then macrocrack penetrations. When the fissure length is short, shallow collapse failure modes can be observed; when the fissure length is long, the deep layer slide occurs, and the slope stability decreases with an increase in fissure length. The micro and macrocrack surfaces are basically consistent with pre-existing fissure angles, and the safety factor is the least at a fissure angle of 30°. The greater the fissure density, the greater the number of macrocracks, and the stability decreases with an increase in the number of pre-existing fissures. The research results can provide some references for disaster protection and understanding the failure laws of rock slopes. Meanwhile, combining the geological survey results with the numerical simulations and developing a high-performance IKSPH program will be a future research direction.
  • Investigation on creep behavior of warm frozen silty sand under thermo-mechanical coupling loads
    ZHANG Feng, SHI Sheng, FENG De-cheng, CAI Lei-zhou
    2021, 18(07): 1951-1965.
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    In cold regions, the creep characteristics of warm frozen silty sand have significant effect on the stability of slope and subgrade. To investigate the creep behavior of warm frozen silty sand under thermo-mechanical coupling loads, a series of triaxial creep tests were carried out under different temperatures and stresses. The test results reveal that the creep strains decrease as the consolidation stress increases, and finally tend to be equal under the same loading stress, regardless of whether the stress is isotropic or deviatoric. Additionally, warm frozen silty sand is highly sensitive to temperature, which greatly influences the creep strain both in the consolidation stage and loading stage. Furthermore, based on the creep test phenomena, a new creep model that considers the influence of the stress level, temperature, hardening, and damage effect was established and experimentally validated. Finally, the sensitivity of the model parameters was analyzed, and it was found that the creep curve transitions from the attenuation creep stage to the non-attenuation creep stage as the temperature coefficient and stress coefficient increases. The hardening effect gradually changes to the damage effect as the coupling coefficient of the hardening and damage increases.
  • Creep characteristics and constitutive model for frozen mixed soils
    SONG Bing-tang, LIU En-long, SHI Zhao-yun, WANG Pan, YU Qi-hao
    2021, 18(07): 1966-1976.
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    The uniform settle caused by the permafrost creep is still the primary problem of engineering construction in cold region. To investigate the creep characteristics of frozen soils mixed with silty clay and coarse-grained sand, several triaxial creep tests of frozen mixed soils under different conditions(temperature, confining pressure, coarse-grained particle content) were performed, and the effects of the temperature, confining pressure and coarse particle content on the creep characteristics of frozen mixed soils were also analyzed. The results of the experiments indicated that when the confining pressure was low, the specimen exhibited an attenuation creep under a low-stress level(0.4-0.7) and a non-attenuation creep under a high-stress level(0.7-0.9). In contrast, when the confining pressure was high, the specimen had both initial and stable creep stages, but no the accelerated creep stage. The higher the content of coarse grains, the shorter the stable creep stage, and the easier to enter the accelerated creep stage for the specimen. Further, the long-term strength of frozen soils decreased with an increase in the content of coarse grains. Finally, a newly improved Nishihara model was proposed to consider both the hardening effect and damage effect by introducing both the hardening and damage variables, which can model the entire creep process of frozen soils modeled relatively easily. It was found that with the increasing content of coarse particle, both the strengthening and damaged effects in the creep process are reduced