Search

In cold regions, the thermal effect of accumulated water on underlying permafrost and permafrost subgrade remains a significant hazard causing engineering risks. Water depth of accumulated water may be an important influence factor of permafrost thermal stability, but there is lack of qualitative and quantitative research about that. In this study, equivalent thermal conductivity theory and solid heat transfer theory have been used to establish the calculation model for simulating heat transfer in water and soil. Thereafter, the accuracy and reliability of the calculation model are checked by monitored data and subsequently used to analyze the thermal erosion of water on underlying permafrost and permafrost under the embankment. These simulation results show that shallow water can protect permafrost and deeper water disrupts the thermal stability of underlying permafrost. The thermal effect extent of water is primarily determined by its depth, and the concept of critical depth and stable depth of accumulated water has been proposed. Moreover, the temperature field of permafrost under embankment can be changed by the slope toe water. In addition, the thermal effect range of the slope toe water is limited by the thermal influence radius, which increases with the depth of standing water. These findings provide support as well as a fundamental base for environmental issues arising from the accumulated water. These observations will, thus, also be valuable to further engineering environment studies in cold regions.

Corrosion products caused by accumulated water in low places of the product oil pipeline often lead to trunk line equipment blockage.It is an effective method to reduce the corrosion of product oil pipeline and prevent the pipeline blockage by oil flow shear to flush the accumulated water in low places and discharge it out of the pipeline.The research progress on the accumulated water flow characteristics, the accumulated water movement speed, the critical conditions under which accumulated water can be displaced, the influencing factors and rules of critical conditions were summarized, from the aspects of experimental research, theoretical analysis and numerical simulation.The existing problems in the current research were analyzed, and it was proposed that the experimental research on the distribution characteristics and movement speed of accumulated water should be carried out in a wider speed range(0.57–1.53 m/s).In addition, the critical conditions for the transformation from pipes pre-wetted with water to constant oil-wetting pipes should also be studied.The research results have guiding significance to discharging the accumulated water and impurities.

Water accumulation in permafrost regions causes a heavy thermal impact on the frozen layer, thereby leading to its degeneration. First, based on the real heat transfer process, this study proposes relevant hypotheses and governing equations for heat calculation models involving completely melted water, ice-bearing water, water–soil interface, and soil under water. The models consider the water surface as a thermal boundary on account of the natural buoyancy convection mechanism in water and the phase transition process. Second, this study verifies the accuracy of the calculation models regarding the measured water and permafrost temperatures. The four seasonal vertical temperature changes in the water according to this model are found to be consistent with the actual temperature-change trend, and the permafrost temperature under water is also consistent with the actual temperature field. This study thus provides theoretical support for the thermal impact analysis of water in permafrost regions.

Abstract: According to the principle and grading standards of DC electric in-advance detection, the paper analyzed the geophysical characteristics of gob in abandoned coal mines, summed up the verified characteristics of DC electric anomalies in advanced detection of goaf water. The results showed that water-accumulating gob of abandoned mines is commonly characterized by low resistivity, the anomaly bigger than 2 δ (δ is square deviation) is disastrous anomaly; although the old workings full of water in abandoned mines have low resistivity, the amplitude and anomalies is not the same, there are some differences, the workings not fully filled with water have relatively low resistivity; water-accumulating gob near roof and floor sometimes have abnormal response of low resistivity because of infiltration of fractures. There exists interpretation ambiguity for advanced electric detection. [Copyright &y& Elsevier]