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。

夏特河源于天山最大现代冰川作用中心托木尔—汗腾格里峰的东北坡,流域内保存有形态较为清晰的四套冰川沉积。这些地形记录了夏特河流域的古冰川变化,对它们进行研究可获得该地晚第四纪以来的冰川时空演化规律。在第三套冰碛夹层中的砂质透镜体里采集了5个OSL年代学样品,应用单片再生(SAR)测年技术测得它们的年龄为(13.3±0.8)～(20.1±1.3)ka。基于测年结果、各套冰碛距现代冰川的远近、冰碛垄的完整程度、冰碛物的风化胶结状况及接触关系,并参阅托木尔—汗腾格里峰南坡与东南坡以及东、中、西段天山其他流域的年代学资料,可初步得出:第一套和第二套冰碛分别沉积于小冰期和新冰期;第三套冰碛形成于末次盛冰期及随后的冰消期,可对应于海洋氧同位素阶段(MIS)2;保存在河口的第四套冰川沉积及与其相关联的宽阔且长达数十千米的"U"形谷共同指示,它应形成于冰川规模较大的倒数第二次冰期,时间上可对应于MIS 6。

夏特河源于天山最大现代冰川作用中心托木尔—汗腾格里峰的东北坡,流域内保存有形态较为清晰的四套冰川沉积。这些地形记录了夏特河流域的古冰川变化,对它们进行研究可获得该地晚第四纪以来的冰川时空演化规律。在第三套冰碛夹层中的砂质透镜体里采集了5个OSL年代学样品,应用单片再生(SAR)测年技术测得它们的年龄为(13.3±0.8)～(20.1±1.3)ka。基于测年结果、各套冰碛距现代冰川的远近、冰碛垄的完整程度、冰碛物的风化胶结状况及接触关系,并参阅托木尔—汗腾格里峰南坡与东南坡以及东、中、西段天山其他流域的年代学资料,可初步得出:第一套和第二套冰碛分别沉积于小冰期和新冰期;第三套冰碛形成于末次盛冰期及随后的冰消期,可对应于海洋氧同位素阶段(MIS)2;保存在河口的第四套冰川沉积及与其相关联的宽阔且长达数十千米的"U"形谷共同指示,它应形成于冰川规模较大的倒数第二次冰期,时间上可对应于MIS 6。