This study addresses the cracking issue of airport foundations in marine and coastal regions by proposing an unsaturated reinforcement method based on Microbially Induced Calcium Carbonate Precipitation (MICP) combined with coconut fibers. Composite sand columns incorporating coconut fiber and bioslurry were prepared, and the effects of fiber length and content on the mechanical properties of MICP-treated sand columns were investigated. Experimental results revealed that the addition of short fibers (1-5 mm) significantly improved the unconfined compressive strength and ductility of the MICP-treated sand columns. As the bioslurry content decreases in the sand columns, the enhancement effect of short fibers on the unconfined compressive strength becomes more pronounced, with fiber addition improving compressive strength by up to 98 %. However, the inclusion of medium fibers (5-10 mm) and long fibers (10-15 mm) negatively affected the mechanical properties of the sand columns. Microstructural analysis further confirmed the synergistic reinforcement effect of short fibers and calcium carbonate precipitation. Short fibers acted as bridges, forming additional contact points between sand particles, which facilitated calcium carbonate precipitation at critical contact points, thereby enhancing the overall stability and strength of the sand columns. This characteristic was more pronounced under unsaturated conditions. This study provides a feasible technical solution for the effective reinforcement of airport foundations and demonstrates potential in unsaturated reinforcement and improving the ductility of sandy soil foundations.

Reconstructing fluvial dynamics is a fundamental requirement for understating the interaction between past environmental changes and human adaptation. This study focuses on the central part of the floodplain of the Nan River in northern Thailand that likely played a role in the catastrophic flood of 1818 CE, which damaged the ancient of Nan city and forced its relocation. We investigated nine sediment cores from the floodplain and from the eastern tributaries of the Nan River, to identify the potential source of floods in the past. By combining the analyses of sedimentary characteristics and provenance, the study reveals that the eastern tributaries were the dominant sediment source for most areas, with the Nan River only influencing areas close to its channel. According to optically stimulated luminescence dating, the highest sediment accumulation occurred during the eleventh to thirteenth centuries CE, coinciding with agricultural expansion and deforestation, suggesting increased erosion in the catchment of the tributaries. These findings challenge the assumption that the main Nan River has been the primary contributor to flooding catastrophes in the region and highlights the potential crucial role of smaller tributaries in similar settings in other parts of the globe.

The Dead Sea Transform (DST), a prominent tectonic feature on Earth's crust, provides an exceptional natural laboratory for investigating the dynamic processes associated with continental rifting and its subsequent evolution. This study focuses on the sedimentary and tectonic evolution of the Yesha Fault, a marginal fault of the DST. Along the Yesha Fault, a distinct, elongated depression, known as the Yesha Valley was formed. Through detailed analysis of sedimentary sequences from boreholes and geochronological data obtained by optically stimulated luminescence and magnetostratigraphy, this research aims to refine the understanding of sedimentation patterns, rates, and tectonic activity associated with this marginal fault. The initial formation of the Yesha Valley, postdating the Brunhes-Matuyama reversal (-773 ka), was driven by normal faulting, resulting in an accommodation space progressively infilled with clastic and aeolian sediments. The sedimentary record reveals four distinct cycles of calcic soil between -780 ka and -450 ka, indicative of short episodes of tectonic subsidence, each followed by a period of tectonic quiescence, during which carbonate accumulated and calcic soils have developed. Following -450 ka, the sedimentary sequence accumulated in the subsiding valley lacks evidence of abrupt tectonic events, suggesting a transition to a tectonic regime dominated by gradual creep. During the last glacial period, sedimentation is characterized by clay deposition, with more hydric conditions and increased organic content observed between 4 and 6.5 m, whereas the uppermost 2 m of the soil reflects the influence of recent anthropogenic activity. Sediment accumulation rates within the Yesha Valley exhibit considerable variability, ranging from 20.8 cm/ka to 1.8 cm/ka, with an average of 3.2 cm/ka. These rates are an order of magnitude lower than those observed in the adjacent Hula Basin, indicating a slower tectonic regime along the marginal Yesha Fault and valley.

Microbially induced calcium carbonate precipitation (MICP) is an emerging ecofriendly microbial engineering technique that utilizes urease-producing microorganisms to enhance the mechanical properties of soils. Sporosarcina pasteurii (S. pasteurii) stands out among these microorganisms as an efficient urease producer. However, field trials often lead to less-than-optimal experimental outcomes due to the presence of native soil microbes. To evaluate the impact of indigenous microorganisms on the effectiveness of MICP at the site, bacteria isolated from natural soil, classified of on-site low-ureolysis and high-ureolysis bacteria (OSLUB and OSHUB, respectively), were combined with S. pasteurii to conduct MICP experiments both in microfluidic chips and sand columns. Analysis covered the bacterial population, urease activity, pH changes, calcium carbonate crystal count and volume, as well as the unconfined compressive strength (UCS) of reinforced samples. Experimental results revealed that combining OSLUB with S. pasteurii led to a reduction in bacterial activity of 74% to 84% by 120 h, resulting in an approximately 60% decrease in the chemical conversion rate and the UCS of MICP-treated soils was 60% lower than the S. pasteurii. However, when OSHUB is mixed with S. pasteurii, although there is a reduction in bacterial activity by 49% to 54% by the 120-h mark, the decrease remains less pronounced than the activity decrease observed in S. pasteurii alone, which is 64%. Consequently, the rates of calcium carbonate chemical conversion were enhanced by 9% to 45%, and the UCS of the reinforced sand columns showed a slight improvement relative to the control group. This research highlights the distinct impacts of OSLUB and OSHUB on the efficiency of MICP on location. The main difference between OSLUB and OSHUB lies in their respective effects on pH levels following mixing. OSLUB tends to decrease the pH level gradually in the combined bacterial environment, while OSHUB, in contrast, increases the pH level over time in the same setting. The maintenance of both high bacterial activity and high precipitation rates is crucially dependent on pH levels, highlighting the importance of these findings for enhancing MICP efficiency in field applications. Strategies that either diminish the presence of OSLUB while augmenting that of OSHUB, or that sustain a relatively high pH level, could be valuable. These avenues promise significant improvements and merit further investigation in future studies.

Microbially induced carbonate precipitation (MICP) utilizing a urease active bioslurry is an ecofriendly method that can improve soil strength. However, the micromechanisms, such as ion diffusion, production rate of CaCO3, porosity, and permeability of pile reinforced by bioslurry, require further investigation. In this study, both biopile model tests and a coupled fluid-flow, solute transport and biochemical reactive model were conducted to analyze the mechanical property and biocementation mechanism of pile formed by urease active bioslurry. Results showed that the simulated CaCO3 content along the biopile length after 120 h grouting was close to test results. The UCS of the biopile decreased from 3.44 MPa to 0.88 MPa and the CaCO3 content decreased from 13.5% to 9.1% with increasing depth. The largest reduction in CaCO3 content was observed in the middle part of the biopile as the CaCO3 crystals in the upper part hindered the downward transport of the cementation solution. The morphology of CaCO3 crystals was influenced by cementation solution concentration, as evidenced by the predominance of spherical vaterite crystals in the upper part of the biopile and rhomboidal calcite crystals in the middle and lower parts. During the grouting process, the concentration of calcium ions and urea decreased, while the ammonium ion levels increased with depth due to the utilization of calcium ions and urea for CaCO3 precipitation and ammonium ion production. The production rate of CaCO3 first increased rapidly to reach a peak value and then decreased. The porosity and permeability demonstrated both linear and nonlinear decreasing trends as the CaCO3 concentration increased. The largest reduction in porosity and permeability, reaching 20% and 58% in the biopile top.

Several studies have documented a close relationship between forest fires and the instability of the soil-vegetation system. Furthermore, repeated wildfires, especially characterized by extreme severity and intensity, can induce hydrological and geomorphological effects that persist over several years, e.g., the temporary erosion rate intensification and the susceptibility increase of most significant downslope soil movement. This study analyzes the close relationship between wildfires and soil instability by examining the mega-fire in July 2021 in the Montiferru - Planargia region (Sardinia, Central Mediterranean). The proposed multiscalar methodology provides management and plan indications to mitigate potential damages caused by extreme wildfire, especially in areas with high susceptibility from a hydrogeological perspective, using physical models supported by open geodata in a GIS-based workflow.

准确界定蒙山峨峪口砾石堆积堤的形成时代，对于探明其成因、澄清山东中低山丘陵第四纪冰川有无之争，是一个需要解决的科学问题。峨峪口堆积垄岗砾石组构、沉积构造、地貌组合等标志，均指向其为山洪泥石流堆积物，且为暴发频率极低、发展周期较长的水石流或稀性泥石流堆积。其下伏第四纪沉积物OSL埋藏年龄和AMS14C年龄可作为砾石堆积堤形成时代的最老约束参考年龄，当地村民迁居此地的历史可作为最小约束参考年代。OSL测年结果为2.1～2.3 ka BP,AMS14C测年结果为951～1522 cal AD,证明砾石堆积堤为数百年前形成的历史泥石流遗迹。

准确界定蒙山峨峪口砾石堆积堤的形成时代，对于探明其成因、澄清山东中低山丘陵第四纪冰川有无之争，是一个需要解决的科学问题。峨峪口堆积垄岗砾石组构、沉积构造、地貌组合等标志，均指向其为山洪泥石流堆积物，且为暴发频率极低、发展周期较长的水石流或稀性泥石流堆积。其下伏第四纪沉积物OSL埋藏年龄和AMS14C年龄可作为砾石堆积堤形成时代的最老约束参考年龄，当地村民迁居此地的历史可作为最小约束参考年代。OSL测年结果为2.1～2.3 ka BP,AMS14C测年结果为951～1522 cal AD,证明砾石堆积堤为数百年前形成的历史泥石流遗迹。

准确界定蒙山峨峪口砾石堆积堤的形成时代，对于探明其成因、澄清山东中低山丘陵第四纪冰川有无之争，是一个需要解决的科学问题。峨峪口堆积垄岗砾石组构、沉积构造、地貌组合等标志，均指向其为山洪泥石流堆积物，且为暴发频率极低、发展周期较长的水石流或稀性泥石流堆积。其下伏第四纪沉积物OSL埋藏年龄和AMS14C年龄可作为砾石堆积堤形成时代的最老约束参考年龄，当地村民迁居此地的历史可作为最小约束参考年代。OSL测年结果为2.1～2.3 ka BP,AMS14C测年结果为951～1522 cal AD,证明砾石堆积堤为数百年前形成的历史泥石流遗迹。

Aeolian landscapes dominate the semiarid dune fields across the Asian summer monsoonal boundary (ASMB) of northern China, where the widespread palaeosols are usually regarded as indicators of enhanced monsoonal precipitation (moisture) during the Late Quaternary. However, the processes of palaeosol development, and their response to climate change, remain controversial due to the complex land-atmosphere interactions within different bioclimatic zones. Here, we review the patterns of palaeosol development, precipitation/moisture (P/ M) evolution, and lake level fluctuations across different sub-regions of the ASMB. With the aid of typical temperature and vegetation records, we qualitatively and quantitatively distinguish the contributions of different climatic factors to palaeosol development since 20 ka (1 ka = 1000 cal yr BP) and elucidate the underlying mechanisms. Our results indicate an asynchronous pattern of palaeosol development, with optimum develop-ment during 10-4, 8-4, and 6-2 ka in northeastern (NE) China, north central (NC) China, and on the NE Qinghai -Tibetan Plateau (QTP), respectively. This implies a transmeridional asynchronous pattern of palaeosol devel-opment on the scale of the ASMB. Our qualitative and quantitative analysis of the contributions of climatic variables elucidates the various relationships between palaeosol development and the climatic background across different sub-regions of the ASMB. The results demonstrate that temperature and precipitation are the dominant factors for palaeosol development in NE and NC China, respectively; whereas effective moisture, rather than temperature and precipitation alone, controls palaeosol development on the NE QTP, demonstrating different pedogenic responses against the same overall climatic background. These mechanisms are supported by the results of multiple studies of Holocene vegetation evolution and the associated climatic conditions. We conclude that the asynchronous pattern of palaeosol development across the ASMB was caused by variations in different dominant climatic factors, highlighting the diverse and complex interactions of climate change and Earth surface processes, even within the relatively uniform climatic environment of semiarid northern China. Our findings emphasize the differing responses of palaeosol development to regional climate change and provide new insights into the interactions of the land-atmosphere system in the critical zone of northern China.