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According to local villagers, the main Beiguo landslide on the Heyang Loess Tableland in China occurred several decades ago (the specific time is unknown). After the initial occurrence of the main landslide, there was no major activity for several decades until December 17–22, 2017 (2 months after the rainy season), when the main landslide was completely reactivated. One of the interesting findings of our field survey is that there are two erosion gullies and numerous loess caves (groups) developed at the top of the Beiguo landslide, which are generally considered to be the dominant channels by which rainwater or surface runoff enters the deep underground space. In order to better understand the process and triggering factors of the main landslide's reactivation, a multidisciplinary investigation including satellite remote sensing, interferometric synthetic aperture radar (InSAR), an unmanned aerial vehicle (UAV) survey, a terrestrial laser scanning (TLS) survey, an electrical resistivity tomography (ERT) survey, laboratory experiments, real-time monitoring using an inclinometer, and field investigations of the Beiguo landslide was conducted. We believe that the reactivation of the main Beiguo landslide may have been occurring for more than 10 years, or perhaps even longer. Since 2011, there have been several signs of local activity in the main landslide body, and the last accelerated stage of the entire deformation process occurred in 2017. The development and existence of loess caves directly destroyed the stability of the slope, and the rainfall and surface runoff quickly entered the interior of the main landslide. The influence of the loess caves on the landslide's reactivation was long-term and continuous. The results of this study suggest that the several days of abundant and continuous rainfall in the rainy season in 2017 were the last direct trigger of the final reactivation of the main landslide. The secondary landslide significantly changed the original slope, including the aspect of the slope profile's morphology, the slope gradient, relief, erosion, and accumulation, which accelerated the evolution of the tableland landform. This study enhances our understanding of the reactivation behavior of loess landslides, and also provides important support for the monitoring and prevention of reactivated landslides in the future. [ABSTRACT FROM AUTHOR]

The natural gas hydrate (NGH) reservoir in China is mainly distributed in the continental shelf with water depths ranging from 600–1500 m, about 90% of which is stored in the shallow area of the deep sea, with weak cementation and non-diagenetic characteristics. In order to test and study this type of NGH, samples must be prepared in situ, in large quantities, and at fast speed. At present, there are problems with the common stirring, spraying, and bubbling preparation techniques available, such as slow generation rate, low gas storage density, and lack of rapid preparation. Therefore, the rapid preparation of large samples of non-diagenetic natural gas hydrate has received extensive attention at home and abroad. In view of this technical bottleneck, Southwest Petroleum University innovatively established a rapid preparation kettle of 1062 L. In this paper, the preparation experiment of natural gas hydrate in the South China Sea (the pressure of the preparation kettle was reduced from 7 MPa to 3.3 MPa) was carried out in the preparation method of the 'three-in-one' (stirring method, spraying method, bubbling method) and experimental test method. In the process of preparation of non-diagenetic gas hydrate, the data of dynamic image, temperature, pressure, electrical resistivity, and reaction time are tested. During the preparation of natural gas hydrate, temperature, pressure, and electrical resistivity curves in four preparation methods were made, respectively. Through the experimental data analysis of different preparation methods of natural gas hydrate, it has been found that the preparation time of natural gas hydrate using the stirring method, the spraying method, and the bubbling method alone require a longer preparation time. However, when the three-in-one method is used to prepare natural gas hydrate, the preparation cycle of natural gas hydrate is obviously shortened. The preparation time of the single method of stirring method, spraying method, and bubbling method is respectively about 5.13, 3.59, and 3.37 times as long as that of three-in-one method. The three-in-one method for preparing natural gas hydrate greatly improves the preparation efficiency, which has a great significance to the scientific and technological progress of experimental research and evaluation methods of natural gas hydrate. [ABSTRACT FROM AUTHOR]