In practical engineering, coal burst is usually caused by the combination of high geo-stress and dynamic loading. To study the dynamic response of coal in geo-stress conditions, numerical models of a coupled static–dynamic split Hopkinson pressure bar (SHPB) test system were established, based on which impact tests for coal specimens at different impact speeds and static pre-stress levels were conducted. The mechanical properties, energy characteristics and failure patterns of coal specimens under coupled static and dynamic loads were analyzed. The results show that when the pre-stress is constant, peak stress, the maximum strain energy and the maximum kinetic energy increase significantly with impact speed. Nevertheless, they are less affected by the static pre-stress, increasing linearly with a pre-stress level under lower impact speeds but becoming stable under higher impact speeds. In addition, weak dynamic loads may trigger the instability of the coal specimen in a high pre-stre
The unique ecosystems and biodiversity associated with mid-ocean ridge (MOR) hydrothermal vent systems contrast sharply with surrounding deep-sea habitats, however both may be increasingly threatened by anthropogenic activity (e.g., mining activities at massive sulphide deposits). Climate change can alter the deep-sea through increased bottom temperatures, loss of oxygen, and modifications to deep water circulation. Despite the potential of these profound impacts, the mechanisms enabling these systems and their ecosystems to persist, function and respond to oceanic, crustal, and anthropogenic forces remain poorly understood. This is due primarily to technological challenges and difficulties in accessing, observing and monitoring the deep-sea. In this context, the development of deep-sea observatories in the 2000s focused on understanding the coupling between sub-surface flow and oceanic and crustal conditions, and how they influence biological processes. Deep-sea observatories provide
Introduction The establishment of China’s first official overseas military base in Djibouti in 2017 set the precedent for People’s Liberation Army (PLA) units to be permanently stationed abroad. Many foreign analysts assume that China will continue expanding its overseas military presence, most likely through a mix of adding new bases and leveraging dual-use ports. The 2021 U.S. Department of Defense …
Soft-soil reinforcement with stone columns is a popular ground improvement method. Installation of columns modifies the surrounding soft soil properties; this phenomenon is termed "smear."Although several previous investigations were carried out on smear zone characterization, appropriate field-based studies are limited. The authors performed field-based investigations to quantify the installation effects by collecting a series of undisturbed soil samples from a reinforced soft ground site with newly installed stone columns and conducting laboratory testing followed by nonlinear regression analysis. It is observed that the stone column installation induced significant alteration in the soft soil properties when the columns are closely spaced. An explicit fast Lagrange finite-difference modeling is carried out employing unit cell analogy, where the nonlinear variation in soft clay permeability and compressibility is simulated. The disturbed soft-soil parameters obtained are su
Novel approaches developed by scientists including Lexie Yang of ORNL scan massive datasets of large-scale satellite images to more accurately map infrastructure – such as buildings and roads – in hours versus days.