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过刊目录

  • 2023年, 20卷, 第01期
    刊出日期：2024-06-19
      
  • 全选
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  • Deformation and failure mechanism of Yanjiao rock slope influenced by rainfall and water level fluctuation of the Xiluodu hydropower station reservoir
    WANG Neng-feng, HE Jian-xian, DU Xiao-xiang, CAI Bin, ZHAO Jian-jun
    2023, 20(01): 1-14.
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    With the construction of the Xiluodu hydropower station on the Jinsha River, the reservoir impoundment began in 2013 and the water level fluctuates annually between 540 m and 600 m above sea level. The Yanjiao rock slope which is located on the left bank of the Jinsha River 75 km upstream of the Xiluodu dam site, began to deform in 2014. The potential failure of the slope not only threatens Yanjiao town but also affects the safe operation of the Xiluodu reservoir. This paper is to find the factors influencing the Yanjiao slope deformation through field investigation, geotechnical reconnaissance, and monitoring. Results show that the Yanjiao slope can be divided into a bank collapse area(BCA) and a strong deformation area(SDA) based on the crack distribution characteristics of the slope. The rear area of the slope has been experiencing persistent deformation with a maximum cumulative displacement(GPS monitoring point G4) of 505 mm and 399 mm in the horizontal and vertical directions,respectively. The potential failure surface of the slope is formed 36 m below the surface based on the borehole inclinometer. The bank collapses of the Yanjiao slope are directly caused by the reservoir impoundment while the deformation area of the slope is affected by the combination of the rainfall and reservoir water level fluctuation. Based on mechanism of the Yanjiao slope, prestressed anchor combined with the surface drainage and slope unloading are recommended to prevent potential deformation.
  • Investigating the performance of passageway corridor for ground reinforced embankments against rockfall
    Muhammet ?EL?K
    2023, 20(01): 15-30.
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    Rockfall disasters can result in damages to various structures such as highways and buildings.Ground reinforced embankments(GRE) are one of the barrier types used to prevent rockfall. GRE absorb the impact energy of the hitting rock blocks by the movement of fine soil particles triggered by the penetration of the rock in the soil. In this process,stresses in the wall are distributed in both the transverse and longitudinal directions. GREs on the valley slopes can be hundreds of meters long, so such structures cause difficulty in transition to valley slope behind the embankments. Especially, access to areas such as agricultural, pasture or forest lands behind the GRE becomes a challenge. The current paper presents the design of passageways in GRE using the finite element method to provide safe corridors at several different parts within the hundreds of meters long structures. A total of 4 different passageway designs for GRE were developed. Each finite element model was subjected to rockfall with different kinetic energies of 500, 1000 and 3000kJ. The obtained results showed that 44% increase in structure volume increased the impact capacity from 500 kJ to 3000kJ.Furthermore, the critical displacement caused by rockfall impact with an energy of 3000 kJ was reduced by 31%. It was determined that the support applied with the reinforced concrete wall did not reach the desired energy absorption value due to its rigid structure, and even collapsed at 3000 kJ.
  • Effects of the probability of pulse-like ground motions on landslide susceptibility assessment in near-fault areas
    LIU Jing, FU Hai-ying, ZHANG Ying-bin, XU Pei-yi, HAO Run-dan, YU Hai-hong, HE Yun-yong, DENG Hong-yan, ZHENG Lu
    2023, 20(01): 31-48.
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    Earthquake-induced strong near-fault ground motion is typically accompanied by largevelocity pulse-like component, which causes serious damage to slopes and buildings. Although not all near-fault ground motions contain a pulse-like component, it is important to consider this factor in regional earthquake-induced landslide susceptibility assessment. In the present study, we considered the probability of the observed pulse-like ground motion at each site(PP) in the region of an earthquake as one of the conditioning factors for landslide susceptibility assessment. A subset of the area affected by the 1994Mw6.7 Northridge earthquake in California was examined. To explore and verify the effects of PP on landslide susceptibility assessment, seven models were established, consisting of six identical influencing factors(elevation, slope gradient, aspect,distance to drainage, distance to roads, and geology)and one or two factors characterizing the intensity of the earthquake(distance to fault, peak ground acceleration, peak ground velocity, and PP) in logistic regression analysis. The results showed that the model considering PP performed better in susceptibility assessment, with an area under the receiver operating characteristic curve value of 0.956.Based on the results of relative importance analysis,the contribution of the PP value to earthquakeinduced landslide susceptibility was ranked fourth after the slope gradient, elevation, and lithology. The prediction performance of the model considering the pulse-like effect was better than that reported previously. A logistic regression model that considers the pulse-like effect can be applied in disaster prevention, mitigation, and construction planning in near-fault areas.
  • Characteristics of gully bed scour and siltation between check dams
    LYU Xiao-bo, YOU Yong, WANG Zhuang, LIU Jin-feng, SUN Hao, ZHAO Wan-yu
    2023, 20(01): 49-64.
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    Check dams are the most commonly used engineering measure for debris flow control worldwide. The scour and siltation characteristics between dams are important factors affecting dam design. In this study, classical dimensional analysis of the variables that influence the development of gully bed scour and siltation was carried out. Flume experiments were conducted to examine the influence characteristics of opening width, flume slope, debris flow density, and opening rate on the characteristics of gully bed scour and siltation. The influential characteristics of variables on the dimensionless scour depth, scour length, siltation length, scour volume and siltation volume were obtained. The experiments showed that, with an increase in the relative opening from 1.5 to 2.5, scour depth increased by 7.4%, scour length decreased by 11.2%, siltation length increased by 22.0%, scour volume decreased by 4.7% and siltation volume increased by 22.0%. With an increase in flume gradient from 0.105 to 0.213, scour depth,siltation length and siltation volume increased by 40.0%, 65.9% and 65.9%, respectively, and scour length decreased by 20.1%. With an increase in sediment concentration from 0.303 to 0.545, siltation length and siltation volume increased by 15.4% and 15.4%, respectively, and scour depth, scour length and scour volume decreased by 9.6%, 9.1% and 17.8%,respectively. As opening rate increased from 0.08 to 0.32, siltation length and siltation volume increased by 33.3% and 33.3%, respectively, and scour depth,scour length and scour volume decreased by 5.4%,13.7% and 18.4%, respectively. The results showed that the flume gradient was the most influential factor on scour depth, scour length, siltation length and siltation volume, and the sediment concentration was the most influential factor on scour volume. Then,according to the experimental data, some empirical formulas predicting scour depth, scour length,siltation length, scour volume and siltation volume were obtained. The error between the computed values according to the formulas in this paper and the observed values was within ±10%. These research results may provide a technological basis for window dam design in debris flow disaster prevention and mitigation.
  • Influence of different soil properties on the failure behavior of deposit slope under earthquake after rainfall
    YANG Bing, HOU Jiang-rong, ZHOU Zi-hong, GOU Jin-cheng
    2023, 20(01): 65-77.
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    In this study, the influence of soil properties on the failure behavior and mechanism of slope under earthquake after rainfall was studied with shaking table test in the laboratory, in which the failure process of slope and instant responses of water content and pore water pressure were tested. Based on the principle of similarity, a model test was designed. The experimental results showed that soil properties exhibit significant influence on failure mode and failure mechanism of slope. Local flowslide,local failure, and creep flowslide failure modes appear in the slope exposed to only rainfall. However, under earthquake after rainfall, the other three failure modes occur, i.e., local slip failure, overall slip failure,and shallow scouring and creep flowslide failure. The spatial distribution of water content and pore water pressure are the two key factors leading to slope failure. Furthermore, due to the difference of permeability, the soil properties not only affect the spatial distribution of water content of the slope after rainfall, resulting in the peak pore water pressure which occurs mainly near the foot of the slope and near the bedrock interface in the middle and lower parts of the slope, but also affect the dissipation of excess pore water pressure in the process of earthquake. Finally, it is discovered that different types of soil lead to significant differences in the peak acceleration of slope failure. The critical acceleration of slope with coarse-grained soil is greater than that of slope with fine-grained soil. The critical acceleration of slope failure shows a close relationship with soil properties.
  • Overcast sky condition prevails on and influences the biometeorology of the tropical Andean Páramos
    Paola MONTENEGRO-DíAZ, Rolando CéLLERI ALVEAR, Galo CARRILLO-ROJAS
    2023, 20(01): 78-86.
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    Clouds play a major role in modulating the biometeorological processes. We studied the influence of cloudiness on four biometeorological variables:daily air temperature(T_(air)), relative humidity(RH),reference evapotranspiration(ET_r),and photosynthetic active radiation(PAR), recorded at four sites of Andean Páramos in southern Ecuador during 2.5 to 5.5 years. First, we quantified both the cloud cover percentage(Cloud%) creating cloud masks over the visible bands of Landsat 7 images and the sky condition(K_T) using the records of solar and extraterrestrial radiation. Second, we estimated K_T from Cloud%. Finally, we quantified T_(air), RH, ET_r, and PAR under clear, cloudy, and overcast K_T and their dependence on K_T. The average Cloud% ranged between 65%–76%, and K_T corroborated the prevailing overcast sky(between 55% and 72.5% of the days) over the páramos. The proposed model performed well in the sites of calibration(R~2 = 0.80;MBE = 0.00; RMSE = 0.05) and validation(R~2 = 0.74;MBE =-0.07; RMSE = 0.11). The overcast sky diminished T_(air)(≤ 10o C), ET_r(≤ 1.6 mm day~(-1)), and PAR(4 MJ m~(-2) day~(-1)) and increased RH(≥ 88%),while the variables showed the opposite behavior during the uncommon clear sky(≤ 5.5% of the days).Thus, mostly the dynamic of RH(R~2 ≥ 0.62), ETr(R~2≥ 0.85), and PAR(R~2 ≥ 0.77) depended on K_T. Hence,the prevailing overcast sky influenced the biometeorology of the páramos.
  • A new formula of recovery factor for non-equilibrium transport of graded suspended sediment in the Middle Yangtze River
    LI Lin-lin, XIA Jun-qiang, ZHOU Mei-rong, DENG Shan-shan, LI Zhi-wei
    2023, 20(01): 87-100.
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    Suspended sediment concentrations in the Middle Yangtze River(MYR) reduced greatly after the Three Gorges Project operation, causing the composition of bed material to coarsen continuously.However, little is known about the non-equilibrium transport of graded suspended sediment owing to different bed material compositions(BMCs) along the MYR, and it is necessary to determine the magnitude of recovery factor. Using the Markov stochastic process in conjunction with the hiding-exposure effect of non-uniform bed-material, a new formula is proposed for calculating the recovery factor including the effect of different BMCs, and it is incorporated into the non-equilibrium transport equation to simulate the recovery processes of suspended load in both sand-gravel bed and sand bed reaches of the MYR. The results show that:(i) the recovery rate of graded sediment concentrations at Zhicheng was slower than that at Shashi during the period 2003-2007;(ii) the mean recovery factors of the coarse,medium, and fine sediment fractions in the ZhichengShashi reach were 0.152, 0.0012, and 0.0005,respectively, and the coarse sediment recovered up to the maximum sediment concentration of 0.138 kg/m~3 over a distance of 15 km; and(iii) the results of the new formula that can consider the effect of bed material composition are in general agreement with the field observations, and the spatial and temporal delay effects are inversely related to particle size and BMC. Consequently, the BMC effect on the nonequilibrium sediment transport in different reaches of the MYR needs to be considered for higher simulation accuracy.
  • Larch growth across thermal and moisture gradients in the Siberian Mountains
    KHARUK Viacheslav I., PETROV Il'ya A., GOLYUKOV Alexey S., DVINSKAYA Maria L., IM Sergei T., SHUSHPANOV Alexander S.
    2023, 20(01): 101-114.
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    Climate-driven changes in the thermal and moisture regimes may variously influence different tree species growth and ranges. We hypothesize that drought resistant Siberian larch(Larix sibirica Ledeb.) and precipitation-sensitive Siberian pine(Pinus sibirica Du Tour) responded differently to climate change along the elevational thermal and precipitation gradients. We studied the influence of air temperature, precipitation, soil moisture, and atmospheric drought(indicated by the drought index SPEI) on larch and pine growth along the southward megaslope of the West Sayan Ridge. We found that since 2000 climate change resulted in increasing larch and pine radial growth index(GI)(c. 1.5–3times) within treeline(2000–2300 m) and timberline(1900–2000 m) ecotones, i.e. within high precipitation zones. Within the forest-steppe ecotone(1100–1200 m) in which L. sibirica is the only species, larch GI stagnated or even decreased. The total forested area increased since 2000 up to +50%in the high elevations, whereas in the low elevations(<1400 m) area changes were negligible. Within treeline and timberline, trees' GI was stimulated by summer temperature. Meanwhile, temperature increase in early spring reduces GI due to living tissue activation followed by tissue damage by desiccation.Within forest-steppe, larch radial growth was mostly dependent on soil moisture. Warming shifted dependence on moisture to the early dates of the growing period. Acute droughts decreased GI within forest-steppe as well as within treeline, whereas the drought influence on both species within highlands was insignificant. Within forest-steppe seedlings establishment was poor, whereas it was successful within treeline and timberline. Current climate change leads to stagnation or even decrease in Larix sibirica growth in the southern lowland habitat. In combination with poor seedlings establishment,reduced growth threatens the transformation of open lowland forests into forest-steppe and steppe communities. Meanwhile, in the highlands warming facilitated the growth of Siberian larch and pine and the increase of forested area.
  • Characteristics of the dynamic changes in active accumulated temperature in Sichuan, China in the last 51 years against the background of climate change
    WANG Hao, JIANG Shan, WANG Jia-bin, YU Xiao-hang, HUANG Jia-ning, LIU Jian-gang
    2023, 20(01): 115-128.
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    It is of utmost necessity to understand the dynamics of regional active accumulated temperature(AAT) to cope with the negative impacts of global warming on agroforestry development and food security and to provide a real-time and effective reference basis for regional agroforestry planning.The daily temperature data from 30 meteorological stations in Sichuan Province from 1970 to 2020, and sea surface temperature(SST) index data from the Atlantic Multiphase Oscillation(AMO) and Pacific Decadal Oscillation(PDO) were used for the study.Sichuan Province was divided into the western region(WS) and the eastern region(ES), considering 1000 m above sea level as the boundary. The spatiotemporal characteristics of ≥0°C and ≥10°C active accumulated temperature(AAT0, AAT10) in WS and ES were analyzed comprehensively using 5-day average sliding, empirical orthogonal function(EOF),ensemble empirical mode decomposition(EEMD),and multiple mutation tests. The results show that(1)AAT0 and AAT10 of WS ranged from 3034°C to 3586°C and 1971°C to 2636°C, respectively, while the AAT0 and AAT10 of ES ranged from 5863°C to 6513°C and 4847°C to 5875°C, respectively. The period around 1997 was a significant abrupt change,and the AAT in the province generally increased during the subsequent time period(2) AAT in the study area is mainly driven by the fluctuations of AMO, as reflected by the low-to-high variation of AAT coinciding with the jump of the cold-to-warm phase of AMO. Considering different time scale fluctuations in the past 51 years, the major cycle for both AAT0 and AAT10 in WS is 3.40 a, while the major cycles in ES are 3.64 a and 3.19 a, respectively with a sub-cycle of 7.29 a. AAT fluctuation has an insignificant periodic characteristic of 25.50 a on the interdecadal scale(3)The spatial heterogeneity of AAT in WS is prominent and is mainly reflected by the significantly warm conditions in the south of the WS region and relatively slight warm conditions in the north, as well as by the isolated cooling area in the form of "freezing point", i.e., Xiaojin county. In contrast, the spatial variability of AAT in ES is more or less consistent,with the warming areas concentrated in the foothills of the western edge of the basin and a slight increase in AAT observed in the central part of the basin.
  • Historical relationships of the Mesoamerican highlands, with emphasis on tropical montane cloud forests: a temporal cladistic biogeographical analysis
    CASTRO-TORREBLANCA Marisol, ESPINOSA David, BUENO-HERNáNDEZ Alfredo, LUNA-VEGA Isolda
    2023, 20(01): 129-140.
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    The historical relationships of nine areas of endemism of the tropical montane cloud forests(TMCFs) were analysed based on a temporal cladistic biogeographical approach.Three cladistic biogeographical analyses were conducted based on 29cladograms of terrestrial taxa by partitioning them into three time-slices, namely, Miocene, Pliocene, and Pleistocene. The results showed different area relationships over time. For the Miocene and Pliocene time slices, the Isthmus of Tehuantepec acted as a geographic barrier that fragmented the TMCFs into two portions: west of the Isthmus and east of the Isthmus. In the case of the Pleistocene, the TMCFs were broken into two portions, one related to the Neotropical region and the other to the Nearctic region. Furthermore, the analyses allowed us to detect the influences of different geological and paleoclimatological events on the distribution of the TMCFs over time. Therefore, the TMCFs current distribution might have been driven by geological events during the Miocene-Pliocene, whereas climatic fluctuations have the highest impact during the Pleistocene.
  • Evolution and bathymetry of glacial lake at the lowest elevation in Nepal Himalaya
    Shusila KANDEL, Nitesh KHADKA, Dhurba TIWARI, Dibas SHRESTHA, Kedar RIJAL
    2023, 20(01): 141-144.
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    One of the prominent impacts of climate change induced glacier retreat in the Himalayas is the formation and expansion of glacial lakes. The newly formed glacial lakes are mostly located in higher altitudinal regions(4200-5800 m) of Himalaya,however, a new glacial lake(Kapuche, 28.446° N and 84.116° E) have been reported to be emerged in the relatively low elevation area of ～2450 m above sea level(masl) in the Nepal Himalaya. This short communication presents the remote sensing-based evolution and field-based bathymetry of Kapuche lake, and further discusses its formation process and lake type for being a glacial lake at the lowest elevation in Nepal Himalaya.
  • Spatio-temporal variation of trace elements distributed over surface water of Upper Ganga River Basin in Western Himalayan Region
    Deepika DIMRI, Ambika KUMAR, Deepak Kumar MISHRA, Archana SHARMA
    2023, 20(01): 145-162.
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    The rivers draining from the Himalayan range distribute enormous amount of fresh water to the people living in downstream regions. Trace metals flowed with river water can lead to serious impact on ecological system and human health. Nevertheless,the documentation on trace elements of Himalayan rivers is inadequately documented. The current study deals with the spatial and temporal variability of the major and trace elements of Ganga river water in epirhithron, metarhithron and hyporhithron zone belonging to Himalayan segment. Water samples from nineteen monitoring locations were collected in pre-monsoon(May-June),monsoon(AugustSeptember) and post-monsoon(December) seasons and subjected to be assessed for 20 elements(Ag, Al,Ba, Cd, Ca, Cr, Cu, Fe, Ga, K, Mn, Mg, Na, Ni, Pb, Sr,Th, U, Zn, and Zr) using ICP-OES(Inductively Coupled Plasma-Optical Emission Spectrometer).Different water pollution indexes such as HPI(Heavy Metal Pollution Index), MI(Metal Index) and PI(Pollution Index) were used to describe current water quality status at each monitoring station under particular classified ecological zone. The studied stations in hyporhithron zone had the value of Metal Index(MI>1), indicating threshold of warning.Further, the highest values of HPI in hyporhithron zone correspond to poor water quality status. Sites with poor water quality were also found to be contaminated as per the Pollution Index(PI),exhibiting high concentrations for element(Fe).However, the epirhithron and metarhithron zone in Himalayan segment showed excellent water quality mainly contributed from natural sources. Cluster Analysis(CA) and Principal Component Analysis(PCA) were applied to identify the main influential sources for Ganga river water pollution. The Kriging interpolation method was also applied to prepare spatial distribution map of computed indexes(HPI,MI, and PI). With the help of index of local Moran's I(LMI), identified spatial clusters and spatial outliers revealed the elevated concentration of most elements in hyporhithron zone. The dataset presented in this study would be convenient for government officials in developing more effective management policies and necessary steps to check and monitor the Ganga river water quality. It was also suggested that further investigations in terms of trace elemental sources and their role in self-purification properties of Ganga water can be addressed in future.
  • Ethnobotany of food, medicinal, construction and household utilities producing plants in Cikaniki, Gunung Halimun Salak National Park,Indonesia
    Asih Perwita DEWI, Peniwidiyanti PENIWIDIYANTI, Muhammad Rifqi HARIRI, Prima Wahyu Kusuma HUTABARAT, Irfan MARTIANSYAH, Intani Quarta LAILATY, Ahmad MUNAWIR, Misbah Satria GIRI, Ervan AMBARITA
    2023, 20(01): 163-181.
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    The community living around the Cikaniki Area of Gunung Halimun Salak National Park(CAGHSNP) uses various plants to fulfill their needs.Their habits are related to indigenous knowledge of using plants as food, medicine, construction, and household utilities, which dynamic societal changes have not displaced. This study aimed to inventory and update potential plants used as food, medicine,construction, and household utilities by local communities in the Cikaniki area, and measure and analyze their cultural and ethnobotanical value. This study objected to five hamlets in the Cikaniki at Malasari Village, Nanggung District, Bogor Regency,West Java, Indonesia. The quantitative analysis was calculated based on the Informant Consensus Factor,Fidelity Level, and Use Value. We analyzed the qualitative data based on the data collection through observation, interviews, and documentation from informants and respondents in five hamlets. The study recorded 199 plant species from 75 families used by the community of CA-GHSNP. The most utilized species in Cikaniki were Staurogyne elongata,Caryota mitis, Blumea balsamifera, Castanopsis argentea, Pilea melastomoides, and Piper betle.There are 72 species of plants used as food, 122species for medicinal purposes, and 50 species of plants used for construction and household utilities.The potential plant species in the CA-GHSNP, their utilization categories, and recommendation for conservation strategy are discussed.
  • Soil erosion and its causes in high-filling body: A case study of a valley area on the Loess Plateau, China
    BAO Han, TANG Ming, LAN Heng-xing, PENG Jian-bing, ZHENG Han, GUO Guan-miao
    2023, 20(01): 182-196.
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    Large-scale land consolidation projects(LCPs) have been carried out on the Loess Plateau to increase the area of agriculture land. The newly created land is prone to soil erosion under the effects of water and gravity. Taking a typical high-filling body(HFB) formed by LCPs in Yan'an, China as the subject, this study comprehensively investigated the types and causes of soil erosion with multiple methods of field investigation, on-site monitoring and laboratory tests. Results showed that the HFB presented a composite pattern of soil erosion with multiple types mainly including underground erosion,mixed water-gravity erosion, seepage erosion, and scouring erosion. The type of erosion varied spatially in different parts of the HFB depending on the dominant factors, mainly including the groundwater state, rainfall, runoff, gravity action, topography, and soil erodibility. The underground erosion mainly occurred at the positions with higher groundwater level and larger hydraulic gradient, while scouring erosion mainly occurred at the positions with extensive interactions of surface runoff, channel slope gradient and soil properties. And near the leading edge of the top of the slope, a band of mixed watergravity erosion occurred owing to the effects of water and gravity. In addition, nearly saturated soils at the toe of HFB displayed groundwater exfiltration and slope-face slumping. Based on our findings on the causes and variation of soil erosion for the HFB, we proposed the following erosion prevention and control measures to protect the LCPs on the Loess Plateau: to construct drainage ditches and blind ditches to form a complete drainage system, plant alfalfa on the top platform to increase rainfall interception and reduce surface runoff, set seepage ditches and plant deep-rooted plants at the toe of the slope to improve slope toe stability, monitor groundwater level and slope deformation to learn the erosion dynamics and slope stability, and optimize the geometry of HFB such as the slope gradient and slope steps to reduce soil erosion.
  • Selecting proper sites for underground dam construction using Multi-Attribute Utility Theory in arid and semi-arid regions
    Mohammad Hassan SADEGHIRAVESH, Hassan KHOSRAVI, Azam ABOLHASANI
    2023, 20(01): 197-208.
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    Although the construction of underground dams is one of the best methods to conserve water resources in arid and semi-arid regions, applying efficient methods for the selection of suitable sites for subsurface dam construction remains a challenge.Due to the costly and time-consuming methods of site selection for underground dam construction, this study aimed to present a new method using geographic information systems techniques and decision-making processes. The exclusionary criteria including fault, slope, hypsometry, land use, soil,stream, geology, and chemical properties of groundwater were selected for site selection of dam construction and inappropriate regions were omitted by integration and scoring layers in ArcGIS based on the Boolean logic. Finally, appropriate sites were prioritized using the Multi-Attribute Utility Theory.According to the results of the utility coefficient, seven sites were selected as the region for underground dam construction based on all criteria and experts' opinions. The site of Nazarabad dam was the best location for underground dam construction with a utility coefficient of 0.7137 followed by sites of Akhavan with a utility coefficient of 0.4633 and Mirshamsi with a utility coefficient of 0.4083. This study proposed a new approach for the construction of the subsurface dam at the proper site and help managers and decision-makers achieve sustainable water resources with limited facilities and capital and avoid wasting national capital.
  • Dual-objective pattern optimization method for land suitability zoning in mountain counties
    WANG Lei, WU Lian, ZHANG Wei, JING Wen-li
    2023, 20(01): 209-226.
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    As the basic administrative unit of China,counties have grown rapidly in recent years in the context of rapid urbanization, especially for counties located in mountainous areas. The drastic changes in land in mountainous areas can easily cause irreversible damage to the sensitive ecological environment. Through the dual-objective suitability zoning of ecological and construction balance,regional sustainable land use patterns can be realized.In this study, Hantai District in Southern Shaanxi province, China, was chosen as the research area aiming at creating a balance between ecological supply and the development of construction in spatial planning. A dual-objective process evaluation system for ecological protection and construction development was proposed with 15 resistance factors selected from three attributes: natural ecology,economic society, and policy. The minimum resistance surface discrimination methods for ecological land and construction development land were proposed based on vertical space superposition and horizontal minimum cumulative resistance models. Finally, the land in Hantai District was divided into four development grades from the optimal angle of dual goals, i.e., the construction core zone being 134.56 km~2, the suitable construction zone 115.77 km~2, the ecological buffer zone 153.74 km~2, and the ecological control zone 151.93 km~2,using the method combining resistance difference and threshold division. In addition, the development direction of each town under jurisdiction was identified. This study compensates for the deficiency of traditional methods that evaluate land only from a single vertical or horizontal process.
  • Mechanical and acoustic emission characteristics of anhydrite rock under freeze-thaw cycles
    ZHANG Chi, JIN Xiao-guang, HOU Chao, HE Jie
    2023, 20(01): 227-241.
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    To study the damage mechanisms of anhydrite rock under freeze-thaw cycles, the physicalmechanical properties and the microcracking activities of anhydrite rock were investigated through mass variation, nuclear magnetic resonance, scanning electron microscope tests, and uniaxial compression combined with acoustic emission(AE) tests. Results show that with the increase of freeze-thaw processes,the mass, uniaxial compression strength, and elastic modulus of the anhydrite specimens decrease while the porosity and plasticity characteristics increase.For example, after 120 cycles, the uniaxial compression strength and elastic modulus decrease by 46.54% and 60.16%, and the porosity increase by 75%. Combined with the evolution trend of stressstrain curves and the detected events, three stages were labeled to investigate the AE characteristics in freeze-thaw weathered anhydrite rock. It is found that with the increase of freeze-thaw cycles, the proportions of AE counts in stage Ⅰ and stage Ⅱ show a decaying exponential trend. Contrarily, the proportion of AE counts in stage Ⅲ displays an exponential ascending trend. Meanwhile, as the freeze-thaw cycles increase, the low-frequency AE signals increase while the intermediate-frequency AE signals decrease. After 120 cycles, the proportion of low-frequency AE signals increases by 168.95%, and the proportion of intermediate-frequency AE signals reduces by 81.14%. It is concluded that the microtensile cracking events occupy a dominant position during the loading process. With the increase of freeze-thaw cycles, the b value of samples decreases.After 120 cycles, b value decreases by 27.2%, which means that the proportion of cracking events in rocks with small amplitude decreases. Finally, it is proposed that the freeze-thaw damage mechanism of anhydrite is also characterized by the water chemical softening effect.
  • Dynamic mechanical characteristics of frozen subgrade soil subjected to freeze-thaw cycles
    WANG Dan, LIU En-long, YANG Cheng-song, LIU You-qian, ZHU Sheng-xian, YU Qi-hao
    2023, 20(01): 242-255.
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    As a widely-applied engineering material in cold regions, the frozen subgrade soils are usually subjected to seismic loading, which are also dramatically influenced by the freeze-thaw(F-T)cycles due to the varying temperature. A series of dynamic cyclic triaxial experiments were conducted through a cryogenic triaxial apparatus for exploring the influences of F-T cycles on the dynamic mechanical properties of frozen subgrade clay.According to the experimental results of frozen clay at the temperature of-10°C, the dynamic responses and microstructure variation at different times of F-T cycles(0, 1, 5, and 20 cycles) were explored in detail.It is experimentally demonstrated that the dynamic stress-strain curves and dynamic volumetric strain curves of frozen clay are significantly sparse after 20F-T cycles. Meanwhile, the cyclic number at failure(Nf) of the frozen specimen reduces by 89% after 20freeze-thaw cycles at a low ratio of the dynamic stress amplitude. In addition, with the increasing F-T cycles,the axial accumulative strain, residual deformation,and the value of damage variable of frozen clay increase, while the dynamic resilient modulus and dynamic strength decrease. Finally, the influence of the F-T cycles on the failure mechanisms of frozen clay was discussed in terms of the microstructure variation. These studies contribute to a better understanding of the fundamental changes in the dynamic mechanical of frozen soils exposed to F-T cycles in cold and seismic regions.
  • Damage evolution and strength attenuation characteristics of carbonaceous slate under low velocity dynamic impact
    TAO Zhi-gang, LI Meng-nan, LIU Kui-ming, AI Kai-wen, WANG Yong
    2023, 20(01): 256-272.
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    Rock is subjected to impact loading during tunnel and subsurface engineering.For understanding the damage evolution of rock under dynamic impact, mechanical research was performed on the carboniferous slate surrounding the Muzhailing tunnel under different influencing factors based on the Split Hopkinson Pressure Bar(SHPB)experimental system. The results show that:(1)carbonaceous slate exhibits a continuous failure process, which develops more rapidly in the presence of joints; simultaneously, a negative correlation was found between the joint density and the dynamic strength of rock;(2) under different impact velocities and wavelengths, the method of using incident energy to represent the dynamic damage threshold of carbonaceous slate under high in situ stress was proposed based on the kinetic energy theorem, and the damage threshold of carbonaceous slate was calculated to be 53 J;(3) impact times is the most critical core variable and negatively correlated with peak strength and positively correlated with strain rate, maximum strain, and cumulative damage. The carbonaceous slate is subjected to repeated load impacts, which is followed by accumulation of damage, continuous strength attenuation, and internal dominant fracture expansion. In particular,when the samples break, there is only one main rupture surface, which is the most significant difference from the single impact rupture form.
  • Strength and deformation behavior of the Yellow River silt under triaxial drained condition considering characteristic states
    CHEN Yu-yuan, WANG Yu-ke, Hemanta HAZARIKA, WAN Yong-shuai
    2023, 20(01): 273-284.
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    Currently, the application of the Yellow River silt in subgrade, especially in expressway subgrade, has not been widely promoted. The main reason is that the research on the mechanical characteristics of the Yellow River silt used for subgrade filling is extremely limited. In this study, the static shear test of the Yellow River silt under drained condition was carried out using Global Digital Systems(GDS) triaxial apparatus, and the effects of confining pressure, relative density and shear rate on the strength and deformation behavior of the Yellow River silt were investigated. The cohesive force of the Yellow River silt is low, and the friction angle is the main factor determining the shear strength. Friction angle at phase transformation state φ_(pt), friction angle at peak state φ_(ps), friction angle at critical state φ_(cs),were obtained via the observation on the evolution law of mobilized friction angle during the whole shearing process. The friction angles corresponding to three different characteristic states have the following magnitude relationship, namely φ_(ps)>φ_(cs)>φ_(pt). The strength parameters for low-grade subgrade and highgrade subgrade were chosen to be 29.33° and 33.75°.The critical state line(CSL), envelop of phase transformation(EOP), and envelop of dilatancy(EOD) for three different characteristic states were determined. The critical stress ratio M, the phase transformation stress ratio M_(pt) and the dilatancy stress ratio M_d of the Yellow River silt are 1.199, 1.235,1.152, respectively. These results provide a basis for the mechanical analysis of the Yellow River silt subgrades and the subsequent establishment of dynamic constitutive model of the Yellow River silt.