Coal mining in China has resulted in numerous subsided areas, exacerbating land scarcity issues. The Yellow River carries a high sediment load of nearly 1.6 billion tons annually. Cleaning up the accumulated silt is costly and takes up land. Reusing the sediment from the Yellow River to fill and reclaim the subsided areas caused by coal mining addresses both sedimentation and land reclamation issues, killing two birds with one stone. Nonetheless, technical challenges have emerged, such as machinery sinking into the soil, difficulty draining water, and poor soil quality improvement. To tackle these issues, understanding the physical and mechanical properties of Yellow River sediment is essential. Results show that the average particle size (D50) is 0.08 mm, categorized as fine-grained sandy soil with a relatively uniform particle size distribution. The permeability coefficient is 2.91 x 10-3 cm center dot s-1, similar to that of silty soil, indicating the feasibility for filling reclamation. However, the low permeability requires drainage improvement to accelerate construction timelines. The internal friction angle of the sediment ranges from 34.67 degrees to 31.76 degrees, with a cohesion from 20.79 to 23.92 kPa. To ensure safe and stable construction, machinery must not sink into the fill material. It is recommended to enhance drainage to about 13% for quicker drainage and stable construction. The sediment has a compression coefficient of 0.05 MPa-1, indicating low compressibility. Mechanical compression is not economically viable during the reclamation process. Design elevation (H) and fill elevation (h) should account for cumulative deformation settlement.

It is proposed to build a high-speed railway through the China -Mongolia -Russia economic corridor (CMREC) which runs from Beijing to Moscow via Mongolia. However, the frozen ground in this corridor has great impacts on the infrastructure stability, especially under the background of climate warming and permafrost degradation. Based on the Bayesian Network Model (BNM), this study evaluates the suitability for engineering construction in the CMREC, by using 21 factors in five aspects of terrain, climate, ecology, soil, and frozen-ground thermal stability. The results showed that the corridor of Mongolia's Gobi and Inner Mongolia in China is suitable for engineering construction, and the corridor in Amur, Russia near the northern part of Northeast China is also suitable due to cold and stable permafrost overlaying by a thin active layer. However, the corridor near Petropavlovsk in Kazakhstan and Omsk in Russia is not suitable for engineering construction because of low freezing index and ecological vulnerability. Furthermore, the sensitivity analysis of influence factors indicates that the thermal stability of frozen ground has the greatest impact on the suitability of engineering construction. These conclusions can provide a reference basis for the future engineering planning, construction and risk assessment.

Climate warming could exacerbate the occurrence of thaw settlement hazard in the permafrost regions of the Qinghai-Tibet Plateau (QTP), which would threaten the stability of engineering infrastructure in cold regions. The risk associated with permafrost settlement, valuable for the regional sustainable development, remains poorly assessed or understood on the QTP. In this study, three common Geo-hazard indices were used to assess the settlement risks in the permafrost regions of the QTP, including the settlement index, the risk zonation index, and the allowable bearing capacity index. However, large spatial differences existed in simulating the risk maps by using the abovementioned Geo-hazard indices. Hence, we developed a combined index (I-c) by integrating the three indices to reduce the uncertainty of the simulations. The results indicated that the ground ice is a critical factor for assessing the settlement risk in permafrost regions. We also applied the Ic to assess the settlement risk along the Qinghai-Tibet Railway (QTR). The proportion of low-risk area along the QTR would be the highest (45.38%) for the future periods 2061-2080 under Representative Concentration Pathway 4.5. The medium-risk area combined with the high-risk area would be accounted for more than 40%, which were located at the boundary of the present permafrost regions. Therefore, the corresponding adaptation measures should be taken to reduce the potential economic losses caused by the high-risk regions to the infrastructure. Overall, the results would present valuable references for engineering design, construction and maintenance, and provide insights for early warning and prevention of permafrost thaw settlement hazard on the QTP. (C) 2021 Elsevier B.V. All rights reserved.