Search Results (61)

Loess, a typical soil widely distributed in China, exhibits engineering properties that are highly sensitive to environmental changes, leading to increased erosion and the development of surface cracks. This article examines the influence of initial moisture content, dry density, and thickness on crack formation in compacted loess subjected to wet–dry cycles, using both laboratory experiments and numerical simulation analysis. It quantitatively analyzes the process of crack evolution using digital image processing technology. The experimental results indicate that wet–dry cycles can cause cumulative damage to the soil, significantly encouraging the initiation and expansion of secondary cracks. New cracks often branch out and extend along the existing crack network, demonstrating that the initial crack morphology has a controlling effect over the final crack distribution pattern. Numerical simulations based on MultiFracS software further revealed that soil samples with a thickness of 0.5 cm exhibited more pronounced surface cracking characteristics than those with a thickness of 2 cm, with thinner layers of soil tending to form a more complex network of cracks. The simulation results align closely with the indoor test data, confirming the reliability of the established model in predicting fracture dynamics. The study provides theoretical underpinnings and practical guidance for evaluating the stability of engineering slopes and for managing and mitigating fissure hazards in loess. Full article

In water-limited regions, plant–water interactions significantly affect the hydrological cycle and vegetation dynamics, particularly in deep-rooted plantations where deep water uptake mitigates water stress during seasonal and interannual droughts. In this study, we improved the University of Arizona version of the Noah-MP model by incorporating actual soil thickness, along with new subsurface and water table schemes, to evaluate the long-term influence of plant–water interactions in Robinia pseudoacacia L. plantations. We found that soil water content was sensitive to both soil stratification and vertical root distribution, with Nash–Sutcliffe efficiency increasing from less than 0.20 to 0.63 in sensitivity experiments. Plant–water interactions resulted in persistent low soil water content within the root zone, whereas the static vegetation experiment overestimated soil moisture because of unrealistic infiltration. Transpiration and water uptake remained in dynamic equilibrium, and vegetation growth was not limited by water availability. Deep water uptake (>2 m) contributed 0.3–20.5% of transpiration during the growing season, with higher contributions observed in drier years. Compared to precipitation, evapotranspiration was more sensitive to soil water storage in the upper 0–2 m of soil. Our results emphasize the critical role of plant–water interactions in regulating water availability for deep-rooted plantations on the Loess Plateau under changing environmental conditions. Full article

Loess–palaeosol sequences (LPSs) are continuous records of palaeoenvironmental and palaeoclimatic conditions during the Quaternary. This study includes 17 LPS located in the NE of the Iberian Peninsula, irregularly distributed, associated with different river basins: the Ebro Basin, the Mora Basin, and the Ter sub-basin. The soils developed on these loess deposits present a loam–sandy texture, coarser than the typical loess, ochre in colour, with variable thickness (1–12 m), calcareous composition (20–45% CaCO₃ eq.), very low or null organic matter (OM), and basic pH. These deposits have been classified as desert LPS, whose pedogenesis is mainly associated with the redistribution of calcium carbonate and, in some cases, gypsum. Several methodologies have been applied to determine their mineralogical, physical, and chemical characteristics and date them by luminescence techniques. In addition, some relevant pedofeatures (porosity, CaCO₃, gypsum, etc.) have been characterised in detail. The aims of the present study have been to know the pedogenic development of the LPS by defining the main soil-forming factors that have affected them in order to associate these factors with the characteristic palaeoclimatic and palaeoenvironmental conditions reported in this area over time and to improve the understanding of soil evolution. Full article

The Kashmir Valley, characterized by its rich loess–palaeosol sequences (LPSs), provides a unique geo-archive for reconstructing Late Quaternary climate dynamics. This study presents an extensive multi-proxy study, integrating high-resolution lithostratigraphy, geochemical analyses, stable isotope analysis of soil organic matter (δ¹³C-VPDB), and radiocarbon (¹⁴C) chronology of a sediment sequence approximately 200 cm thick, to unravel the complex interplay of climatic, pedogenic and environmental processes shaping the region spanning the Pleistocene–Holocene transition. The results establish a precise chronology of the sediment sequence between 13.4 ka and 7.2 ka, covering the transition from the Pleistocene to the Holocene Epoch. The results reveal distinct climatic and environmental conditions during this Epoch. The study reveals substantial loess deposition during the cold and dry glacial climate towards the end of the Pleistocene, followed by a shift to a warmer and wetter interglacial climate at the onset of the Holocene Epoch. This climatic shift led to the development of soil units with pronounced fluvial characteristics around 10 ka, eventually transitioning to fluvial deposition. Geochemical indices such as Ca/Ti, Al/Ti, Si/Ti, and K/Ti indicate low weathering intensity prior to 11 ka, followed by a noticeable increase around 11 ka, possibly driven by enhanced precipitation. δ¹³C values, ranging from −26.2‰ to −22.5‰, suggest C₃-dominated vegetation during the Late Pleistocene, indicating wetter climatic conditions. This study provides valuable insights into the intricate interactions between climate, soil development, and vegetation dynamics during the critical Late Pleistocene–Holocene transition in the Kashmir Valley. Full article

Frequent agricultural irrigation events continuously raise the groundwater table on loess platforms, triggering numerous loess landslides and significantly contributing to soil erosion in the Chinese Loess Plateau. The movement of irrigation water within the surficial loess layer is crucial for comprehending the mechanisms of moisture penetration into thick layers. To investigate the infiltration and evaporation processes of irrigation water, a large undisturbed soil column with a 60 cm inner diameter and 100 cm height was extracted from the surficial loess layer. An irrigation simulation event was executed on the undisturbed soil column and the ponding infiltration and subsequent evaporation processes were systematically monitored. A ruler placed above the soil column recorded the ponding height during irrigation. Moisture probes and tensiometers were installed at five depths to monitor the temporal variations in volumetric water content (VWC) and matric suction. Additionally, an evaporation gauge and an automatic weighing balance measured the potential and actual evaporation. The results revealed that the initially high infiltration rate rapidly decreased to a stable value slightly below the saturated hydraulic conductivity (K_s). A fitted Mezencev model successfully replicated the ponding infiltration process with a high correlation coefficient of 0.995. The monitored VWC of the surficial 15 cm-thick loess approached a saturated state upon the advancing of the wetting front, while the matric suction sharply decreased from an initial high value of 65 kPa to nearly 0 kPa. The monitored evaporation process of the soil column was divided into an initial constant rate stage and a subsequent decreasing rate stage. During the constant rate stage, the actual evaporation closely matched or slightly exceeded the potential evaporation rate. In the decreasing rate stage, the actual evaporation rate fell below the potential evaporation rate. The critical VWC ranged from 26% to 28%, with the corresponding matric suction recovering to approximately 25 kPa as the evaporation process transitioned between stages. The complete evaporation process was effectively modeled using a fitted Rose model with a high correlation coefficient (R² = 0.971). These findings provide valuable insights into predicting water infiltration and evaporation capacities in loess layers, thereby enhancing the understanding of water movement within thick loess deposits and the processes driving soil erosion. Full article

Due to the unique structural characteristics of loess, the strength of loess is significantly influenced by the water content. Therefore, different support parameters should be used for loess tunnels constructed in different water content strata. This paper takes the Fengshouling Tunnel as a case study, studying the reasonable primary support parameters under different water contents using the surrounding rock strength test, on-site monitoring, and numerical simulation software analysis. The research findings indicate that the strength of the surrounding rock is functionally related to its water content, with the cohesive force c exhibiting an exponential relationship and the angle of internal friction φ showing a linear relationship, and that the cohesive force c is more affected by changes in water content than the internal friction angle φ. The crown settlement of the loess tunnel exceeds the horizontal convergence, and the deformation behavior can be categorized into three distinct stages: rapid growth, continuous growth, and slow growth. Concurrently, the primary support structure mainly bears compressive stress. On the basis of considering structural safety and engineering economy, for tunnels with a general water content (10~17%), it is recommended to use I18 steel ribs spaced 60 cm apart and C25 shotcrete with a 24 cm thickness; for high water content (17~25%), it is recommended to use I20a steel ribs, also spaced 60 cm apart, complemented by C25 shotcrete increased to a 26 cm thickness; for situations with an extremely high water content (≥25%), it is recommended to reinforce the surrounding rock with curtain grouting and use steel ribs with the same 60 cm spacing, along with C25 shotcrete maintained at a 26 cm thickness. This paper proposes reasonable support parameters for loess tunnels applicable to different water contents. These results can provide guidance and specific reference for loess tunnels under different water content strata. Full article

On 18 December 2023, a 6.2-magnitude earthquake struck Jishishan, affecting multiple counties and cities in Gansu and Qinghai Provinces. The seismic intensity of the meizoseismal area was VIII, resulting in extensive structural damage and building collapses. A damage assessment was conducted of the epicenter and surrounding high-intensity zones. To understand the typical structures and characteristics of the buildings that were damaged in these high-intensity zones, this study summarizes the characteristics of the damage to typical rural houses, compares the damage of the rural houses across different sites, and analyzes the causes behind these variations. The findings of the study indicate the following: (1) Timber and some brick–timber structures, due to their age, insufficient material strength, and lack of adequate connections between parts of the building, primarily experienced severe damage or total collapse, characterized by through-wall cracks, partial collapses, or complete collapses. (2) Brick–concrete structures predominantly suffered moderate to severe damage due to factors such as improper layout, uneven façades, and inadequate or incomplete seismic measures. The observed damage included significant wall cracks and extensive damage to two-story buildings. (3) Frame structures, mainly used for public facilities like schools, hospitals, and health centers, exhibited strong integrity and excellent seismic performance, resulting in minimal to no damage, with damage largely confined to non-load-bearing components. (4) The amplification effects of seismic waves in thick loess basin areas, slope sites, and the hanging wall effect of faults exacerbated structural damage to rural houses located in certain villages within the high-intensity areas. The results of this study can serve as a reference for post-disaster reconstruction and seismic retrofitting of buildings and contribute positively to enhancing the disaster resilience of rural housing. Full article

Landslides on gently inclined loess–bedrock contact surfaces are common geological hazards in the northwestern Loess Plateau region of China and pose a serious threat to the lives and property of local residents as well as sustainable regional development. Taking the Libi landslide in Shanxi Province as a case study (with dimensions of 400 m × 340 m, maximum thickness of 35.0 m, and volume of approximately 3.79 × 10⁴ m³, where the slip zone is located within the highly weathered sandy mudstone layer of the Upper Shihezi Formation of the Permian System), this study employed a combination of physical model experiments and numerical simulations to thoroughly investigate the formation mechanism of gently inclined loess landslides. Via the use of physical model experiments, a landslide model was constructed at a 1:120 geometric similarity ratio in addition to three scenarios: rainfall only, rainfall + rapid groundwater level rise, and rainfall + slow groundwater level rise. The dynamic changes in the water content, pore water pressure, and soil pressure within the slope were systematically monitored. Numerical simulations were conducted via GEO-STUDIO 2012 software to further verify and supplement the physical model experimental results. The research findings revealed that (1) under rainfall conditions alone, the landslide primarily exhibited surface saturation and localized instability, with a maximum displacement of only 0.028 m, which did not lead to overall instability; (2) under the combined effects of rainfall and rapid groundwater level rise, a “sudden translational failure mode” developed, characterized by rapid slope saturation, abrupt stress adjustment, and sudden overall instability; and (3) under conditions of rainfall and a gradual groundwater level rise, a “progressive translational failure mode” emerged, experiencing four stages: initiation, development, acceleration, and activation, ultimately resulting in translational sliding of the entire mass. Through a comparative analysis of physical model experiments, numerical simulation results, and field monitoring data, it was verified that the Libi landslide belongs to the “progressive translational failure mode”, providing important theoretical basis for the identification, early warning, and prevention of such types of landslides. Full article

Soil erosion and the loss of soil organic carbon (SOC) pools are considered serious environmental problems in undulating landscapes on loess covers, accompanied in some areas, such as south Poland, by the physical degradation of chernozemic soils. The aim of the present study was to identify the scale and reasons for spatial variation of the SOC pools in the intensely cultivated Luvic Phaeozems in one of the unique patches of chernozemic soils in Poland. This study, carried out in a soil catena located in the undulating Carpathian Foreland in south-east Poland, has demonstrated that the SOC pools can greatly differ on a very small scale, even in relatively less differentiated landscapes and in soils classified into the same group. The scale and reasons for the differentiation of the SOC pools depend on the method (depth) of calculation. The spatial differences were smaller and were mainly related to the SOC concentrations and the bulk density of the topsoil horizons, when calculated for depths of 0–30 cm and 0–50 cm. On the other hand, the SOC pools calculated for the 0–100 cm soil layer differed most significantly between the profiles in the catena, representing a continuous growing trend from the uppermost towards the lowermost part of the catena, and were clearly related to the total thickness of the humus horizon(s). The latter findings confirm that sheet erosion has a major impact on the spatial variation of SOC pools in an agricultural landscape. However, soil morphology and the distribution of SOC across the soil profiles suggest additional influences from historical pedogenesis and modern farming technology. The presence of black, thick and humus-rich chernic horizons in all soils across the catena indicates that modern farming must not degrade the soils, but, on the contrary, it can help in the restoration of even neo-formation of chernozemic soils (Phaeozems), if oriented towards the conservation of humus content, soil structure, and biological activity. Full article

The three stages of loess collapse are characterized by notable concealment and sudden onset due to the sudden nature of loess collapse and the prolonged duration of the peristaltic deformation stage. Traditional displacement monitoring methods struggle to detect early signals of instability and failure, leading to poor timeliness in disaster warnings. This project begins by examining non-force field information related to the loess collapse process. It focuses on acoustic emission monitoring and employs model tests to identify effective waveguide rods for monitoring loess collapse. Additionally, the project investigates the evolution anomalies of acoustic emission parameters before and after loess collapse failure, aiming to establish early warning criteria for loess collapse based on acoustic emission. This work provides a theoretical basis for monitoring and early warning of loess collapses. This study evaluates five parameters of the active waveguide system: sensor installation method, filling material, waveguide rod wall thickness, outer wrapping material, and outer wrapping wall thickness. The densities of the filler materials were tested using the optimal parameters derived from the tests to identify the best configurations for active acoustic emission (AE) waveguide systems suitable for monitoring loess collapse. Subsequently, a one-sided connected loess collapse model was employed for indoor tests, integrating real-time AE monitoring with the active waveguide method. This model facilitates the exploration of AE response characteristics during loess collapse and the analysis of destructive forms of loess collapse and time-sequence evolution of AE ringing counts throughout the deformation and destruction process. Results indicate that using filler materials with high elasticity modulus, high compactness, and low Poisson’s ratio, along with thin outer wrapping and waveguide rod walls, leads to strong AE signals. As deformation damage of loess collapse intensifies, the number of AE ringing counts notably increases. A rapid rise in cumulative ringing counts can indicate a “sudden increase”, or the b-value may stabilize, providing precursor information for loess collapse. Full article

Abstract: In the context of the large-scale management of the Loess Plateau and efforts to reduce water and sediment in the Yellow River, this study focuses on a typical watershed within the Loess Plateau. The potential for vegetation restoration in the Kuye River Basin is estimated based on the assumption that vegetation cover should be relatively uniform under similar habitat conditions. The potential for terrace restoration is assessed through an analysis of topographic features and soil layer thickness, while the potential for silt dam construction is evaluated by considering various hydrological and geomorphological factors. Based on these assessments, the overall potential for soil erosion control in the watershed is synthesized, providing a comprehensive understanding of target areas for ecological restoration within the Kuye River Basin. The study demonstrates that the areas with the greatest potential for vegetation restoration in the Kuye River Basin are concentrated in the upper and middle reaches of the basin, which are in closer proximity to the river. The total potential for terracing is 1013.85 km², which is primarily distributed across the river terraces, farmlands, and gentle slopes on both sides of the riverbanks. Additionally, the potential for the construction of check dams is 14,390 units. The target areas for terracing measures in the Kuye River Basin are primarily situated in the middle and lower reaches of the basin, which are in closer proximity to the river. Conversely, the target areas for forest, grass, and check dams, as well as other small watershed integrated management measures, are predominantly located in the hill and gully areas on the eastern and southern sides of the basin. The implementation of the gradual ecological construction of the watershed, based on the aforementioned objectives, will facilitate the protection, improvement, and rational utilization of soil, water, and other natural resources within the watershed. Full article

The Loess Plateau area, with complex geomorphological features and geological structure, is highly prone to geologic disasters such as landslides and debris flow, which cause great losses. To investigate the initiation mechanism of landslide and debris flow disasters and their spreading patterns, historical satellite images in the Laolang gully were collected and digitized to generate three-dimensional topographic and geomorphological maps. Typical landslides were selected for landslide thickness measurement using a standard penetrometer and high-density electrical method. Numerical models were established to simulate the occurrence and development of landslides under different working conditions and to evaluate the spreading range based on the propagation algorithm and friction law. The results show that the 10 m resolution DEM data are well matched with the potential hazard events observed in the field site. The smaller the critical slope threshold, the greater the extent and distance of landslide spreading. The larger the angle of arrival, the greater the energy loss, and therefore the smaller the landslide movement distance. The results can provide scientific theoretical guidance for the prevention and control of rainfall-induced landslide and debris flow disasters in the Loess Plateau area. Full article

To increase the detection accuracy of soil structure and moisture content in reconstituted soils under complex conditions, this study utilizes a 400 MHz ground-penetrating radar (GPR) to examine a study area consisting of loess, sandy loam, red clay, and mixed soil. The research involves analyzing the single-channel waveforms and two-dimensional images of GPR, preprocessing the data, obtaining envelope information via amplitude envelope detection, and performing a Hilbert transformation. This study employs a least squares fitting approach to the instantaneous phase envelope to ascertain the thickness of various soil layers. By utilizing the average envelope amplitude (AEA) method, a correlation between the radar’s early signal amplitude envelope and the soil’s shallow dielectric constant is established to invert the moisture content of the soil. The analysis integrates soil structure and moisture distribution data to investigate soil structure characteristics and moisture content performance under diverse soil properties and depths. The findings indicate that the envelope detection method effectively identifies stratification boundaries across different soil types; the AEA method is particularly efficacious in inverting the moisture content of reconstituted soils up to 3 m deep, with an average relative error ranging from 2.81% to 7.41%. Notably, moisture content variations in stratified reconstituted soils are more pronounced than those in mixed soil areas, displaying a marked stepwise increase with depth. The moisture content trends in the vertical direction of the same soil profile are generally consistent. This research offers a novel approach to studying reconstituted soils under complex conditions, confirming the viability of the envelope detection and AEA methods for intricate soil investigations and broadening the application spectrum of GPR in soil studies. Full article

The combination effect of straw mulching and supplemental irrigation on the soil water and heat, and the growth and productivity of mature apple trees on the Loess Plateau of China remains unclear. Field experiments were conducted in 2022 and 2023 to evaluate the combined effect of straw mulching and supplemental irrigation (two irrigation types, ring and double-row drip irrigation, and three irrigation levels: high, medium, and low irrigation level) on the soil water and temperature, growth, yield, and water productivity (WP) of a mature apple orchard. Local rainfed cultivation was used as the control (CK). The results showed that straw mulching increased soil moisture by 2.4–6.5% compared to the CK treatment. Supplemental irrigation significantly increased soil moisture in the 0–60 cm layer by 3.0–8.1%, and its effect increased with an increasing irrigation level. Straw mulching significantly reduced soil temperature by 7.8% compared to the CK treatment. Supplemental irrigation significantly increased the new shoot length and stem thickness of apple trees. Under straw mulching, a medium supplemental irrigation level significantly increased both apple yield and WP compared to the CK treatment. In this study area, it is recommended to choose a combination of straw mulching and a medium supplemental irrigation level. Full article

The Beiluo River Basin, situated in the central region of the Loess Plateau, frequently experiences landslide geological disasters, posing a severe threat to local lives and property. Thus, establishing a detailed database of historical landslides and analyzing and revealing their development characteristics are of paramount importance for providing a foundation for geological hazard risk assessment. First, in this study, landslides in the Beiluo River Basin are interpreted using Google Earth and ZY-3 high-resolution satellite imagery. Combined with a historical landslide inventory and field investigations, a landslide database for the Beiluo River Basin is compiled, containing a total of 1781 landslides. Based on this, the geometric and spatial characteristics of the landslides are analyzed, and the relationships between the different types of landslides and landslide scale, stream order, and geomorphological types are further explored. The results show that 50.05% of the landslides have a slope aspect between 225° and 360°, 68.78% have a slope gradient of 16–25°, and 38.97% are primarily linear in profile morphology. Areas with a high landslide density within a 10 km radius are mainly concentrated in the loess ridge and hillock landform region between Wuqi and Zhidan Counties and in the loess tableland region between Fu and Luochuan Counties, with a significant clustering effect observed in the Fu County area. Loess–bedrock interface landslides are relatively numerous in the northern loess ridge and hillock landform region due to riverbed incision and the smaller thickness of loess in this area. Intra-loess landslides are primarily found in the southern loess tableland region due to headward erosion and the greater thickness of loess in this area. Loess–clay interface landslides, influenced by riverbed incision and the limited exposure of red clay, are mainly distributed in the northern part of the southern loess tableland region and on both sides of the Beiluo River Valley in Ganquan County. These results will aid in further understanding the development and spatial distribution of landslides in the Beiluo River Basin and provide crucial support for subsequent landslide susceptibility mapping and geological hazard assessment in the region. Full article